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\title{Lichen Species as Bio-Accumulator of Some Halogens on Mount Cameroon Volcano, West Africa}
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             \author[1]{Ayuk Elizabeth  Orock}

             \author[2]{A. B.  Fonge}

             \author[3]{E. M.  Shemang}

             \author[4]{M.  Zhai}

             \author[5]{C. E.  Suh}

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\date{\small \em Received: 1 January 1970 Accepted: 1 January 1970 Published: 1 January 1970}

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\begin{abstract}
        


Lichens diversities are informative indicators for assessing impacts of air pollution, climate change, environmental health, volcanic activities, habitat heterogeneity and continuity. Lacking roots, vascular tissues, stomata and waxy cuticle, they absorb and accumulate airborne nutrients/pollutants from the atmosphere over their entire surface. Halogens, especially fluorides are released into the atmosphere in large amounts by volcanic eruptions and their pollutants levels in lichens can be determined quantitatively by chemical analysis of species.

\end{abstract}


\keywords{lichens, mount cameroon, leptogium gelatinosum, fluorine and halogens.}

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\section[{Introduction}]{Introduction}\par
olcanic regions have always attracted many people worldwide because of the high fertility of their soils \hyperref[b21]{(Diana et al., 2019)}. However, human proximity to volcanoes can lead to several health problems as consequence of the chronic exposure to the materials released from the volcanic activity. An element often found in elevated concentrations in volcanic regions is fluorine. Although fluoride is recognized to have a beneficial effect on the rate of occurrence of dental caries when ingested in small amounts, its excessive intake results in a widespread but preventable pathological disease called fluorosis \hyperref[b20]{(Dey and Giri, 2015)} While skeletal fluorosis, the most severe form of fluorosis, requires a chronic exposure to high concentrations of fluoride in water (4-8 mg/L), dental fluorosis occurs after shorter periods of exposure to fluoride in lower concentrations (1.5-2.0 mg/L). In some volcanic regions, where exposure to elevated amounts of fluoride is persistent, biomonitoring programs are fundamental \hyperref[b23]{(Garcia and Borgnino, 2015)}.\par
In the present world pollution scenario, a comprehensive knowledge of pollutants and their adverse effects on the ecosystem are required for selection of a workable monitoring and conservation technique \hyperref[b44]{(Munzi et al., 2012;}\hyperref[b0]{Ahmad et al., 2007)}. The increasing awareness of the potential hazards and impact of air pollution on the health of human populations, forest decline, climate change and loss of agricultural productivity, for example, has been a cause of increasing public concern throughout the world \hyperref[b53]{(Smodis, 2007)}. This has highlighted the need for continuous monitoring of the levels of pollutants in the environment \hyperref[b24]{(Garty et al., 2002)}. Environmental monitoring approaches that are cheap, can be used anywhere, and respond to many kinds of airborne pollutants are needed to fingerprint the pollutant sources and their dispersion pattern \hyperref[b36]{(Larsen et al., 2007)}. A comprehensive approach to reduce the impacts of pollution and climate change, an approach that decreases emissions across all sectors and enhances the adaptive capacity of all nations with economic reflections is needed \hyperref[b48]{(Pinhoa et al., 2012)}.\par
Lichens emerge as the key answer to this monitoring problem and are the flora of choice for monitoring studies  {\ref (Notcutt and Davis, 1989)}. They obtain their nutrients directly from the atmosphere and their chemical composition therefore holds the promise of becoming a natural or 'green' technique for monitoring the health of the environment around passively degassing volcanoes and industries. Bioaccumulation in lichen thalli has been used as a major tool for assessing air quality in volcanic and industrial areas \hyperref[b7]{(Bennett, 2006)}. They are extremely valuable in environmental monitoring since they exist worldwide and are sensitive to many different kinds of pollutants \hyperref[b9]{(Brodeková et al., 2006)}. They are slow growing; do not shed parts and are perennial pioneer plants commonly described as sentinel organisms  {\ref (Loppi et al., 2002)}. They are good bio-accumulators of heavy metals and trace elements and can be transplanted where they do not occur in nature \hyperref[b39]{(Llop et al., 2012)}.\par
Lichens are mutual symbiosis between fungi with an algal and/or a cyanobacterial partner \hyperref[b43]{(Morris and Purvis, 2007)}. The success in lichenization is attributed to a genetic combination resulting from metabolic biomolecules and influenced by environmental factors \hyperref[b30]{(Jatinder et al., 2012)}. This process has created unique characteristics in lichens such as the unique anatomical (absence of roots, stomata, vascular tissues and cuticle) and physiological (poikilohydry and absorbance of nutrient from general thallus surface from the atmosphere. These peculiarities, allow lichens to grow in all sorts of terrestrial habitats comprising 8\% of vegetation.\par
According to \hyperref[b37]{Lawrey (1986)}, lichens produce a wide array of more than 1000 unique secondary metabolites (depsides, depsidones, ?-orcinoldibenzyl esters, and xanthones, usnic acid and pulvinic acid derivatives, for example) as adaptations for life in marginal habitats. These secondary metabolites assist to maintain the lichen symbiotic association and compete with organisms sharing the same niche \hyperref[b15]{(Culberson and Culberson, 2001)}. Another characteristic stress-resistance mechanism is the accumulation of melanin and oxalate crystals in their thallus, which provide a crystal layer on the thallial surface making lichens tolerant to extreme environments and good bioaccumulators of atmospheric substances \hyperref[b29]{(Hess et al., 2008)}. Most lichens are tolerant to high concentrations of atmospheric pollutants well beyond levels necessary for their physiological requirement by sequestrating and accumulating varied oxalate crystals \hyperref[b24]{(Garty et al., 2002;}\hyperref[b8]{Bjerke et al., 2002;}\hyperref[b11]{Chen et al., 2000)}. The aggregates of these oxalate crystals disintegrate and provide a crystal layer on the thallial surface making lichens good bioaccumulators. Since lichens do not shed parts \hyperref[b60]{(Walker et al., 2003;}\hyperref[b42]{Monge-Nájera et al., 2002)}, and bioaccumulate pollutants safely in their thalli over time, pollutants levels can be professionally determined quantitatively by chemical analysis of species and qualitatively by observing species diversity, abundance and distribution \hyperref[b32]{(Jovans, 2008)}. With their indiscriminate ability to absorb and bio-accumulate both nutrients/ pollutants from the atmosphere, elevated concentrations of certain elements in lichens are a sure sign of atmospheric deposition  {\ref (van Herk, 1999)}.\par
Lichens can be used as bio-monitors of pollutants by quantifying the amount of trace element(s) accumulated within them over time \hyperref[b54]{(Srivastava et al., 2015}\hyperref[b6]{, Bargagli, 2016)}. They have been used to assess deposition and air quality in hundreds of studies worldwide \hyperref[b22]{(Donahue, 2018)}.  {\ref Ayrault et al., 2007, have} shown a relationship between the quantities of pollutants in the environment and those concentrated in lichen thallus. A variety of elements and chemical compounds affecting lichen growth and distribution are found in the atmosphere \hyperref[b3]{(Bajpai et al. 2011)}. Pollutants, including sulfur dioxide (SO 2 ), nitrogen dioxide (NO 2 ) and fluoride (F) compounds, remain in the same chemical form after they are emitted into the atmosphere and are easily absorbed by lichens. Gases like chlorine and fluorine, leads to the injury of fundamental metabolic processes, which arise by acidifying the water and the substrates, resulting in the loss of most sensitive lichen species \hyperref[b9]{(Brodeková et al., 2006)}. Many lichens are sensitive to fluorine pollutant as it can concentrate in hydrated lichens to more than 200 times ambient concentrations  {\ref (Notcutt and Davis, 1989)}. Fluoride are highly toxic to lichens, and elevated levels of fluoride are correlated with chlorophyll breakdown, reduced ATP concentration, reduced photosynthesis and disappearance of species \hyperref[b55]{(Stefano and Luisa, 2006)}. In general, obvious damage to lichens begins at levels of 50-70 ppm.\par
In most parts of Europe like Germany for example, \hyperref[b28]{(Hauck, 2005)}, lichen transplants from pristine to polluted areas are carried out to bioaccumulate atmospheric pollutants. The lichen Hypogimnia physodes was used to bio-accumulate radionuclide Uranium \hyperref[b26]{(Golubev et al., 2006)} and rare earth elements in Czech Republic \hyperref[b31]{(Jitka et al., 2010)}. The fruticose lichen Stereocaulon vesuvianum, growing on the slopes of Mount Vesuvius in South Italy, was used as a bio-monitor of 134 Cs, 137 Cs, 103 Ru and 106 Ru derived from the  {\ref April 26, 1986} Chernobyl nuclear reactor disaster  {\ref (Environment Canada, 2003)}. \hyperref[b27]{Grasso et al. (1999)} found that lichen composition reflects the contribution of the volcanic activity in Mount Etna and Vulcano Island. They noted that, distribution of the degassing elements (arsenic (As), antimony (Sb), Br, and lead.\par
Volcanoes emit a variety of gases both between and during eruptions, including H 2 O, CO 2 , SO 2 , HCl, NH 3 , H 2 S, HF and a few other minor constituents \hyperref[b14]{(Cronin and Sharp, 2002)}. These gases interact rapidly with the ash particles of a volcanic plume and especially atmospheric water to form acidic aerosols. These aerosols given off during and after volcanic eruptions caused problems on a number of occasions when it has accumulated in low lying areas. Exposure to excessive amounts of fluoride may cause adverse health effects for humans and animals \hyperref[b13]{(Conti et al., 2016)} The plume dispersed by winds after a volcanic eruption contains volcanic ash that may also be a source of fluoride at levels that are potentially toxic. Fluorides are released into the environment naturally through the weathering and dissolution of minerals, the emissions from volcanoes and from marine aerosols (WHO, 2002) fluoride emissions from volcanoes and the natural occurrence of excessive amounts of fluoride in drinking water have affected the health of humans and livestock for centuries, if not millennia. Although sometimes of anthropogenic origin, high levels of fluorine are generally related to natural sources. Volcanic emissions of fluorine take the form of either sluggish permanent release from quiescent volcanoes (passive degassing) or rarer but more impacting discharges during short-lived volcanic eruptions \hyperref[b51]{(Schwandner et al., 2004}\hyperref[b38]{Linhares et al., 2017)}. It has been estimated that passive degassing, like that existing at Mt. Etna (Italy) and Masaya (Nicaragua) volcanoes, accounts for about 90\% of the volcanic fluorine release. The influence of these emissions on the surrounding environment and in particular on vegetation has been investigated by several authors \hyperref[b46]{(Nelson and Wheeler, 2016)}.\par
Little or no bio-accumulation and monitoring work have been carried out on the active Mt. Cameroon. Mount Cameroon volcano with a return period of 20 years \hyperref[b57]{(Suh et al., 2003)}, has been the most frequent erupted volcano in West Africa, with eight eruptions in the last 100 years  {\ref (1909, 1922, 1925, 1954, 1959, 1982, 1999 and 2000)}. It constantly releases various constituents into the environment during active eruptions and even in quiescent degassing periods \hyperref[b56]{(Suh et al., 2008)}. These researchers reported that, Mt. Cameroon basanites melt inclusions has shown high levels of carbon dioxide with a concentration of 967 µg/g, sulphur 2400 µg/g, chlorine 1270 µg/g and fluorine 1530 µg/g. In spite of these findings, there is little knowledge of lichens toxic levels and remediation of the high levels of halides release from this volcano.\par
The objective of this paper was to determine the concentration levels of some halogens and identify potential lichens species that can be used as appropriate bio-accumulators of halide toxicity for Mt. Cameroon degassing volcano. 
\section[{II.}]{II.} 
\section[{Materials and Methods}]{Materials and Methods} 
\section[{a) Description of the Study Area i. Location}]{a) Description of the Study Area i. Location}\par
The study area (Fig. \hyperref[fig_0]{1}) is the active MC volcano located in the coastal belt of the Gulf of Guinea, South West Region of Cameroon. It lies between Latitudes 3 º 57' to 4 º 27'N and Longitudes 8 º 58' to 9 º 24'E \hyperref[b57]{(Suh et al., 2003)}. It is the highest peak in West Africa, is of volcanic origin and rises from the Atlantic Ocean to a height of 4100 m. It covers a surface area of about 1750 km 2 (DeLancey and Mark, 2000). The survey sites were divided into Northern and Southern contrasting flanks following wind direction and ash fall trends from various eruptions. The northern flank was called the leeward and southern flank was called the windward. Out of the eight sites selected on the two flanks, four were on the leeward flank (Lower Buea, Upper Buea, IRAD-Ekona and Ekona-Mbenge) and four from the windward flank (Batoke, Bakingili, Idenau and Bomana). Lower Buea on the leeward flank comprises of University of Buea campus, Great Soppo, and Sasse. Some species were collected from control area of Mamfe (5.7512 º N -9.3146 º E) about 270 km from Mt. Cameroon.\par
The survey was also done based on altitudinal levels which ranged between 3 to 2178 m above sea level (Table \hyperref[tab_0]{1}). The altitudinal levels were divided into three (low, mid and high) ranges.  
\section[{c) Sample Selection}]{c) Sample Selection}\par
Thirty-four macro lichens (Foliose and Fruticose) species from six families, eight genera were collected from 8 sites around Mt. Cameroon. From each sites, different sampling points were surveyed given a total of about 12 sampling points in the study. These species were collected from trees and rocks (Table \hyperref[tab_1]{S2}).\par
All the collecting points were Georeferenced with a High Sensitive ErexGlobal Positioning System (GPS).\par
The samples were selected based on the criteria shown on Table \hyperref[tab_1]{2}. The selected species were common to most sites and represent various altitudinal levels on the two flanks of the edifice.  
\section[{d) Sample preparation and analytical procedure}]{d) Sample preparation and analytical procedure}\par
In the Life Sciences laboratory, University of Buea, the lichen species to be analysed for their halogens (F, Br and Cl) levels, were sorted and curated to remove adhering bark, mosses, other lichen species, soil particles, etc. Following \hyperref[b41]{Lorenzini et al., 2006}, no washing procedure was done, to avoid the leaching of soluble matter from tissues. The species were put in labeled envelops and oven-dried to constant weight in a Gallenkemp Hot box oven fan size 3 at 60 º C for 48 hours. The different species were put in small zip locked bags and labeled with chemical codes. Samples were chemically analysed by selective ion electrode method, at the department of geology, university of Botswana. A 0.5 g split of each sample was digested with hydrogen fluoride (HF), then aqua regia and the aliquots analysed.\par
The detection limits ranged from 0.01 to 0.02 ?g/g. Replicate analyses were performed on selected samples and data quality was excellent with standard deviation values less than 1\%. Standards were run between samples and quality control of the analyses was ensured by inserting blanks into the analytical run after 6 samples. Prior to statistical analysis of the geochemical parameters, the data set was regrouped based on the lichen species. The entire data were then log-transformed to normalise skewed distributions. The significance of the difference between means was tested using ANOVA test to compare the concentration of Halogens according to Elevation, Post Hoc Multiple Comparisons Altitudes, Independent Samples t-Test to compare the concentration of Halogens according to substrate types and Box -plot to confirm the test.\par
Volume XXII Issue IV Version I  
\section[{Results}]{Results}\par
ANOVA test on the variation in the concentration of halogens across the different elevation revealed that there was a significant difference (p = 0.022) for F and Br and p= 0.030 for Cl at 95\% confidence level (Table \hyperref[tab_1]{2}   Student t-test for the comparism of the halogens with regards to the substrate (Table \hyperref[tab_4]{4}) shows no significance difference in the means of the all the halogens but a slight difference (p= 0.048 at 0.05 levels) in the variance of Cl.    
\section[{B}]{B}\par
Table \hyperref[tab_1]{S2} revealed that, of the eight lichen genera used for analyses, Leptogium was the most abundant, widely distributed and had very high concentrations of halogens compared to all the other species. Leptogium gelatinosum accumulating ability differs between sites. Leptogium gelatinosum samples from northern leeward flank (MC 02 from Upper Buea, MC 04 from Bomana and MC 10 and MC 11 from Ekona-Mbenge) show low accumulation of halogens over samples collected from the western windward flank Sasse (MC01 and MC03), Idenau (MC 05 and MC06), Bakingili (MC07) and Batoke (MC08 and MC09).\par
Although, Leptogium gelatinosum recorded highest concentrations, other species like Heterodermia obscurata, Cladonia sp, Usnea articulate in BmtUM recorded high concentrations. Lichen species also showed differing accumulating potentials in substrates (Parmotrema tinctorum (MC27) a corticolous sample collected in Ekona-Mbenge accumulated more than the saxicolous specimen (MC26) collected in the same point).\par
All the eight lichen genera showed very high concentrations of F and low levels of Br. F concentration is highest in Leptogium (188 ?g/g) and lowest in Parmotrema (0 ?g/gto 23 ?g/g). The geochemical analysis of the lichens indicated that F was the most dominant halogen (Fig. \hyperref[fig_6]{S1}) with concentrations that range from 25-188 (mean = 78.00 ± 48.68 ?g/g). The range for Cl concentration was 10-127 ?g/g (mean =47.23 ± 33.37 ?g/g), while that for Br, ranges from 0-63 ?g/g (mean= 18 ± 19.58).\par
Fig. \hyperref[fig_7]{S2} shows that, there was highest F-bioaccumulation in Leptogium gelatinosum species in Idenau which ranges from (153 to188 ?g/g), Batoke (165 ?g/g), Bakingili (178 ?g/g), Sasse (152 to155 ?g/g) and low in Ekona-Mbenge (34 ?g/g).\par
Cl bio-accumulation in the Leptogium gelatinosum species in Idenau ranges from (110 to119 ?g/g) was highest and lowest in the Leptogium gelatinosum of Bomana (23 ?g/g), Ekona (33 ?g/g) and Hut 1(28 ?g/g) (Fig. S3).\par
Fig.  {\ref S4}, revealed no Br bio-accumulation in the Leptogium gelatinosum species in Ekona (0 ?g/g) and Bomana (0 ?g/g) but higher in Idenau (63 ?g/g). 
\section[{IV. Discussion}]{IV. Discussion}\par
Lichens from Mt. Cameroon demonstrated significant compositional variation between species as observed on the multi-element distribution patterns even for those growing in the same area. However, specimens from the same species tend to have similar element concentration patterns. This could be explained by the fact that lichens species selectively accumulated some elements. Similarly, \hyperref[b50]{Rani et al. (2011)} found out that, the estimated nine heavy metals in lichen samples from 12 different sites of Dehradun city by periodic monitoring and spotted Zn, Ni, Cd and Cr were higher in lichens, collected from road side while maximum quantity of Fe, Cu and Al were reported in lichens collected from central sites of the city while the lowest amounts of all the metals were reported in sites farther from city.\par
The species Leptogium gelatinosum with very high concentrations of the halogens in all the sampling sites and even the control area of Mamfe 270 km from Mt. Cameroon has a higher tendency to sequestrate these elements than all the other species recorded in the study. This is in accordance with the study about the suitability of the fruticose lichens Evernia prunastri, Cetraria islandica and Ramalina farinacea collected from oak trees in a remote area located in the Chianti Region (Tuscany,central Italy), as transplants for biomonitoring trace element, showed that E. prunastri has to be preferred for its higher accumulating capacity  {\ref (Cercasov et al., 2002)}. Different lichens species in different environments have different sequestration potentials, for example, Ramalina fastigiata has been used as a bio indicator of the impact of a coal mine in Portugal Jó?wiak, (2012).\par
The very high concentrations of F in lichens in this study reflects the study of \hyperref[b56]{Suh et al. (2008)} who measured halogen content in melt inclusions at this volcano and their results indicated an average value of 1530 ?g/g F and 1270 ?g/g Cl. They recorded unusually high F concentrations when compared to glass inclusions from Etna, Hawaii and Piton de la Fournaise. However, the Cl concentrations from Mt. Cameroon were midway between the high values measured for Etna and the low values for Hawaii and Piton de la Fournaise. These exceptionally high values relative to those recorded in this study which maybe an indication that these halogens are an important component of the volatile budget at Mt. Cameroon. These researchers reported that, the concentrations of F in olivine hosted glass inclusion from Mt. Cameroon are the highest known F concentrations for basaltic glass inclusions in the world.\par
Altitude contributed to the halogens concentration variations as intra-species variations consistently yield high concentrations in samples collected from the downwind SW flank of the volcano. These localities lie in the path of wind bearing volcanic gas plumes from Mt. Cameroon and therefore pin their higher halogen content to passive degassing. \hyperref[b1]{Aiuppa et al. (2004)} reported that, during explosive activity huge quantities of fluorine are deposited with ashes around the volcano up to distances of hundreds of km. Fluorine is present as an adsorbed outer layer on the tephra particles which adsorption occurs by condensation of fluoride onto the tephra particles in the plume above the volcano as it cools. The smaller tephra particles have a larger surface area, so carry more absorbed fluoride to be carried further from the volcanic source, and so their greater fluorine-carrying capacity extends the zone of potential fluorine poisoning considerably, even to regions where only a 1 mm thick deposit forms. It is advisable to sample and analyse the tephra or vegetation to identify hazardous regions.\par
This suggests that gases emitted from the volcano are blown south-westwards and are eventually deposited close to the coast resulting in higher halogen content in the lichen species from these areas. More so, the inputs from the sea and from agricultural farms might have increased the high levels in this coastal areas. Studies by \hyperref[b45]{Ndlovu et al. (2019)}, on moss and lichen biomonitoring of atmospheric pollution in the Western Cape Province (South Africa) observed halogens to have elevated concentrations for samples collected from areas with close proximity to the ocean. That is, for both moss and lichen samples at areas closer to the ocean had higher halogen concentrations. Their results also confirmed elevated concentration levels for halogens (Cl, I, Br) in areas closest to the ocean. However, since fluorides are released into the atmosphere in large amounts by volcanic eruptions \hyperref[b3]{(Bajpai et al., 2011)} and fluoride (F) compounds, remain in the same chemical form after they are emitted into the atmosphere, the very high levels of F bioaccumulation in this study, might have come from the degassing volcanic winds of Mt. Cameroon. Also, since other sampling points inland shows high concentration of F, degassing winds and ash deposition should have a greater influence.\par
In this study, even though Leptogium gelatinosum was the highest bioaccmulator, Stictastenroos and Heretodemia obscurata are also good accumulators, while all the Usnea species are poor accumulators. According to \hyperref[b10]{Brodo et al. (2001)} fruticose lichens like Usnea are very sensitive to air pollutants than foliose lichens and occur only in very pure environments. Out of different growth forms of lichens, foliose lichens are prior to metal accumulation followed by crustose and squamulose lichens \hyperref[b34]{(Kar et al., 2014)} and least by fruticose lichens \hyperref[b52]{(Shukla et al.,2014)}. However, lichens from the Usnea species have been used to evaluate heavy metal deposition patterns in the Antarctic  {\ref (Poblet et al., 2011)}. Certain epiphytic lichens have been particularly gained attention for their bioaccumulation potential like Hypogymnia physodes for bioaccumulation of trace elements and Pyxine cocoes for bioaccumulation of metals \hyperref[b4]{(Bajpai et al., 2012;}\hyperref[b16]{Daimari et al., 2020)}.\par
The differing accumulating potentials in substrates of lichen species in this study, (example, Parmotrema tinctorum (MC27) a corticolous sample collected in Ekona-Mbenge accumulated more than the saxicolous specimen (MC26) collected in the same point).Contrary, the findings of \hyperref[b12]{(Chettri et al.,1997)}, who used the lichen species Neophuscelia pulla and Xanthoparmelia taractica to study the bioaccumulation of heavy metals in abandoned copper mines in Greece, where there was a significant correlation between the copper content in the soil(saxicolose) and that of the tree(corticolous) lichen thalli. However, it is for this reason that most studies use epiphytic macro lichens as bio-monitors for air pollutants \hyperref[b40]{(Loppi and Pirintsos, 2003)}. For example, \hyperref[b33]{Käffer et al. (2011)} also reported corticolous lichens as environmental indicators in urban areas in southern Brazil. Furthermore, the no to slight significant difference in means of halogens concentrations with regards to substrates in this study is in accordance with the study of \hyperref[b3]{Bajpai et al. (2011)} in Mandav city in central India illustrated that although most of the metals were absent, or present in insignificant amount in substrates, yet the thallus of lichens had significantly higher concentration of metals such as Cd, Cr, Ni and Zn. Thus it is apparent that the accumulated metals were air borne.\par
All the eight lichen genera showed very high concentrations of F and low levels of Br. Weinstein et al.\par
(1998) reported that, Br and I emissions are not usually of environmental importance and there is virtually no scientific literature on either element. The gas Cl is potentially very hazardous but it is very rare to be released in sufficient quantities to pose a risk \hyperref[b58]{(Temple et al., 1998)}. Chlorine concentrations of 0.4 -2.5 ?g/g range cause severe symptoms like upper surface bleaching, epinasty (distorted growth), chlorosis (yellowing) and leaf drop to plants \hyperref[b58]{(Temple and Krause, 1998)}. The Cl/F ratio in the specimens' ranges from 0.29 to 0.94, which is lower than those measured in lichen specimens at Mt. Etna which ranges from 0.51 to 1.46 \hyperref[b47]{(Notcutt and Davies, 1989)}. According to Delmelle et al.  {\ref (1997)} changes in the Cl/F ratio may reflect different physico-chemical behaviour of the gases entering the atmosphere. However, Halmer et al.  {\ref (2002)} reported that in areas without nearby emission sources, the mean concentrations of fluoride in ambient air are generally less than 0.1µg/g. This was observed from the control area (Mamfe 270 Km) with lower concentrations as compared to those from Mt. Cameroon. Even near emission sources, the levels of airborne fluoride usually do not exceed 2-3 µg/g and in most soils, fluoride is present at concentrations ranging from 20 to 1000 µg/g. This figure can reach several thousand µg/g in mineral soils with natural phosphate or fluoride deposits. Therefore, the atmospheric halogens load at Mt. Cameroon is significantly high and lichens can be potential monitors of this volcanic gas flux.\par
V. 
\section[{Conclusion}]{Conclusion}\par
Leptogium gelatinosum and Heretodemia obscurataare good accumulators, while Usnea species poor accumulators and therefore can be used for pollution bio-monitoring programs in Cameroon. The Leptogium gelatinosum species is therefore a suitable species for monitoring passive degassing at Mt. Cameroon. Also, considering that, lichens of the windward flank of MC accumulated more elemental contents than those from the leeward flanks, shows that wind direction and ash fall contribute largely to pollutant load in lichen species in the windward flanks of mount Cameroon reflecting volcanic degassing as the source. This chemical analysis serves as a baseline data for future studies.\par
Volume XXII Issue IV Version I    \begin{figure}[htbp]
\noindent\textbf{1}\includegraphics[]{image-2.png}
\caption{\label{fig_0}Fig. 1 :}\end{figure}
 \begin{figure}[htbp]
\noindent\textbf{3}\includegraphics[]{image-3.png}
\caption{\label{fig_2}Fig. 3 :}\end{figure}
 \begin{figure}[htbp]
\noindent\textbf{}\includegraphics[]{image-4.png}
\caption{\label{fig_3}}\end{figure}
 \begin{figure}[htbp]
\noindent\textbf{3}\includegraphics[]{image-5.png}
\caption{\label{fig_4}Fig. 3 :}\end{figure}
 \begin{figure}[htbp]
\noindent\textbf{}\includegraphics[]{image-6.png}
\caption{\label{fig_5}B}\end{figure}
 \begin{figure}[htbp]
\noindent\textbf{S1}\includegraphics[]{image-7.png}
\caption{\label{fig_6}Figure S1 :BB}\end{figure}
 \begin{figure}[htbp]
\noindent\textbf{S2}\includegraphics[]{image-8.png}
\caption{\label{fig_7}Figure S2 :}\end{figure}
   \begin{figure}[htbp]
\noindent\textbf{1} \par 
\begin{longtable}{P{0.12857142857142856\textwidth}P{0.19285714285714284\textwidth}P{0.5285714285714286\textwidth}}
Altitude\tabcellsep Range(m)\tabcellsep Sites\\
Low\tabcellsep 3 -499\tabcellsep IRAD-Ekona\\
\tabcellsep \tabcellsep Batoke\\
\tabcellsep \tabcellsep Bakingili\\
\tabcellsep \tabcellsep Idenau\\
Mid\tabcellsep 500-1000\tabcellsep Ekona-Mbenge\\
\tabcellsep \tabcellsep Lower Buea\\
\tabcellsep \tabcellsep Bomana\\
High\tabcellsep >1000\tabcellsep Upper Buea\end{longtable} \par
 
\caption{\label{tab_0}Table 1 :}\end{figure}
 \begin{figure}[htbp]
\noindent\textbf{2} \par 
\begin{longtable}{P{0.11501650165016501\textwidth}P{0.4376237623762376\textwidth}P{0.2973597359735974\textwidth}}
\multicolumn{2}{l}{S/N Criteria (species abundance at sites, elevation, flanks, morphology)}\tabcellsep Species\\
1.\tabcellsep Foliose Species common to all sampling sites\tabcellsep Leptogium gelatinosum,\\
2.\tabcellsep Species of mid elevation\tabcellsep Heterodermia obscurata\\
\tabcellsep \tabcellsep Heterodermia jabonica\\
3.\tabcellsep Species found on the same sampling (Leeward) site but differ in substrate\tabcellsep Parmotrema tinctorum\\
\tabcellsep (tree/rock)\tabcellsep \\
4.\tabcellsep Species restricted to the mid and high altitudes\tabcellsep Flavoparmelia caperata\\
5.\tabcellsep Site-specific species (These are species found only in particular sampling\tabcellsep Canoparmelia concrescens\\
\tabcellsep points and not seen in any other area)\tabcellsep Cladonia sp, Sticta stenroos\\
\tabcellsep \tabcellsep Usnea dasypoga,\\
\tabcellsep \tabcellsep Usnea florida, Usnea articulate\end{longtable} \par
 
\caption{\label{tab_1}Table 2 :}\end{figure}
 \begin{figure}[htbp]
\noindent\textbf{} \par 
\begin{longtable}{P{0.06128526645768025\textwidth}P{0.25579937304075234\textwidth}P{0.24780564263322885\textwidth}P{0.07727272727272727\textwidth}P{0.1225705329153605\textwidth}P{0.04263322884012539\textwidth}P{0.04263322884012539\textwidth}}
\tabcellsep \tabcellsep Sum of Squares\tabcellsep \multicolumn{2}{l}{Df Mean Square}\tabcellsep F\tabcellsep Sig.\\
\tabcellsep Between Groups\tabcellsep 17554.069\tabcellsep 2\tabcellsep 8777.035\tabcellsep 4.321\tabcellsep .022\\
Fluorine\tabcellsep Within Groups\tabcellsep 62966.666\tabcellsep 31\tabcellsep 2031.183\tabcellsep \\
\tabcellsep Total\tabcellsep 80520.735\tabcellsep 33\tabcellsep \tabcellsep \\
\tabcellsep Between Groups\tabcellsep 7630.711\tabcellsep 2\tabcellsep 3815.355\tabcellsep 3.926\tabcellsep .030\\
Chlorine\tabcellsep Within Groups\tabcellsep 30129.760\tabcellsep 31\tabcellsep 971.928\tabcellsep \\
\tabcellsep Total\tabcellsep 37760.471\tabcellsep 33\tabcellsep \tabcellsep \\
\tabcellsep Between Groups\tabcellsep 2814.601\tabcellsep 2\tabcellsep 1407.300\tabcellsep 4.322\tabcellsep .022\\
Bromine\tabcellsep Within Groups\tabcellsep 10093.429\tabcellsep 31\tabcellsep 325.594\tabcellsep \\
\tabcellsep Total\tabcellsep 12908.029\tabcellsep 33\tabcellsep \tabcellsep \end{longtable} \par
 
\caption{\label{tab_2}}\end{figure}
 \begin{figure}[htbp]
\noindent\textbf{3} \par 
\begin{longtable}{P{0.1190978886756238\textwidth}P{0.13785988483685221\textwidth}P{0.12970249520153548\textwidth}P{0.1190978886756238\textwidth}P{0.09136276391554703\textwidth}P{0.061996161228406906\textwidth}P{0.1190978886756238\textwidth}P{0.07178502879078695\textwidth}}
\multicolumn{2}{l}{Tukey HSD}\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \\
\tabcellsep \multicolumn{2}{l}{Dependent Variable}\tabcellsep Mean Difference (I-J)\tabcellsep Std. Error\tabcellsep Sig.\tabcellsep \multicolumn{2}{l}{95\% Confidence Interval Lower Upper Bound Bound}\\
Fluorine\tabcellsep \multicolumn{2}{l}{Low (3-499m) Mid (500-1000m)}\tabcellsep 51.849 *\tabcellsep 19.255\tabcellsep .030\tabcellsep 4.46\tabcellsep 99.24\\
\tabcellsep \tabcellsep High (>1000m)\tabcellsep 51.051 *\tabcellsep 20.257\tabcellsep .044\tabcellsep 1.19\tabcellsep 100.91\\
\tabcellsep \multicolumn{2}{l}{Mid (500-1000m) Low (3-499m)}\tabcellsep -51.849 *\tabcellsep 19.255\tabcellsep .030\tabcellsep -99.24\tabcellsep -4.46\\
\tabcellsep \tabcellsep High (>1000m)\tabcellsep -.799\tabcellsep 18.159\tabcellsep .999\tabcellsep -45.49\tabcellsep 43.89\\
\tabcellsep High (>1000m)\tabcellsep Low (3-499m)\tabcellsep -51.051 *\tabcellsep 20.257\tabcellsep .044\tabcellsep -100.91\tabcellsep -1.19\\
\tabcellsep \tabcellsep Mid (500-1000m)\tabcellsep .799\tabcellsep 18.159\tabcellsep .999\tabcellsep -43.89\tabcellsep 45.49\\
\multicolumn{3}{l}{Chlorine Low (3-499m) Mid (500-1000m)}\tabcellsep 36.357 *\tabcellsep 13.320\tabcellsep .027\tabcellsep 3.57\tabcellsep 69.14\\
\tabcellsep \tabcellsep High (>1000m)\tabcellsep 29.364\tabcellsep 14.012\tabcellsep .107\tabcellsep -5.12\tabcellsep 63.85\\
\tabcellsep \multicolumn{2}{l}{Mid (500-1000m) Low (3-499m)}\tabcellsep -36.357 *\tabcellsep 13.320\tabcellsep .027\tabcellsep -69.14\tabcellsep -3.57\\
\tabcellsep \tabcellsep High (>1000m)\tabcellsep -6.994\tabcellsep 12.561\tabcellsep .844\tabcellsep -37.91\tabcellsep 23.92\\
\tabcellsep High (>1000m)\tabcellsep Low (3-499m)\tabcellsep -29.364\tabcellsep 14.012\tabcellsep .107\tabcellsep -63.85\tabcellsep 5.12\\
\tabcellsep \tabcellsep Mid (500-1000m)\tabcellsep 6.994\tabcellsep 12.561\tabcellsep .844\tabcellsep -23.92\tabcellsep 37.91\\
\multicolumn{3}{l}{Bromine Low (3-499m) Mid (500-1000m)}\tabcellsep 18.762\tabcellsep 7.709\tabcellsep .053\tabcellsep -.21\tabcellsep 37.74\\
\tabcellsep \tabcellsep High (>1000m)\tabcellsep 22.333 *\tabcellsep 8.110\tabcellsep .026\tabcellsep 2.37\tabcellsep 42.29\\
\tabcellsep \multicolumn{2}{l}{Mid (500-1000m) Low (3-499m)}\tabcellsep -18.762\tabcellsep 7.709\tabcellsep .053\tabcellsep -37.74\tabcellsep .21\\
\tabcellsep \tabcellsep High (>1000m)\tabcellsep 3.571\tabcellsep 7.270\tabcellsep .876\tabcellsep -14.32\tabcellsep 21.46\\
\tabcellsep High (>1000m)\tabcellsep Low (3-499m)\tabcellsep -22.333 *\tabcellsep 8.110\tabcellsep .026\tabcellsep -42.29\tabcellsep -2.37\\
\tabcellsep \tabcellsep Mid (500-1000m)\tabcellsep -3.571\tabcellsep 7.270\tabcellsep .876\tabcellsep -21.46\tabcellsep 14.32\\
\multicolumn{4}{l}{*. The mean difference is significant at the 0.05 level.}\tabcellsep \tabcellsep \tabcellsep \end{longtable} \par
 
\caption{\label{tab_3}Table 3 :}\end{figure}
 \begin{figure}[htbp]
\noindent\textbf{4} \par 
\begin{longtable}{P{0.032857142857142856\textwidth}P{0.19714285714285715\textwidth}P{0.07571428571428572\textwidth}P{0.022857142857142857\textwidth}P{0.045714285714285714\textwidth}P{0.032857142857142856\textwidth}P{0.09571428571428571\textwidth}P{0.07857142857142857\textwidth}P{0.08142857142857143\textwidth}P{0.12857142857142856\textwidth}P{0.05857142857142857\textwidth}}
\tabcellsep \tabcellsep \multicolumn{2}{l}{Levene's Test}\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \\
\tabcellsep \tabcellsep \multicolumn{2}{l}{for Equality of}\tabcellsep \tabcellsep \tabcellsep \multicolumn{3}{l}{t-test for Equality of Means}\tabcellsep \tabcellsep \\
\tabcellsep \tabcellsep \multicolumn{2}{l}{Variances}\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \\
\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \multicolumn{2}{l}{95\% Confidence}\\
\tabcellsep \tabcellsep F\tabcellsep Sig.\tabcellsep T\tabcellsep Df\tabcellsep Sig. (2-tailed)\tabcellsep Mean Difference\tabcellsep Std. Error Difference\tabcellsep \multicolumn{2}{l}{Interval of the Difference}\\
\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep Lower\tabcellsep Upper\\
Fluorine\tabcellsep Equal\tabcellsep 3.568\tabcellsep .068\tabcellsep -.623\tabcellsep 32\tabcellsep .538\tabcellsep -16.533\tabcellsep 26.541\tabcellsep -70.595\tabcellsep 37.528\\
\tabcellsep variances\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \\
\tabcellsep assumed\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \\
\tabcellsep Equal\tabcellsep \tabcellsep \tabcellsep -.435\tabcellsep 3.324\tabcellsep .690\tabcellsep -16.533\tabcellsep 38.030\tabcellsep -131.152\tabcellsep 98.086\\
\tabcellsep variances not\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \\
\tabcellsep assumed\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \\
Chlorine\tabcellsep Equal\tabcellsep 4.234\tabcellsep .048\tabcellsep -1.169\tabcellsep 32\tabcellsep .251\tabcellsep -20.933\tabcellsep 17.907\tabcellsep -57.408\tabcellsep 15.541\\
\tabcellsep variances\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \\
\tabcellsep assumed\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \\
\tabcellsep Equal\tabcellsep \tabcellsep \tabcellsep -.760\tabcellsep 3.266\tabcellsep .498\tabcellsep -20.933\tabcellsep 27.552\tabcellsep -104.716\tabcellsep 62.849\\
\tabcellsep variances not\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \\
\tabcellsep assumed\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \\
Bromine\tabcellsep Equal\tabcellsep 2.837\tabcellsep .102\tabcellsep -.761\tabcellsep 32\tabcellsep .452\tabcellsep -8.067\tabcellsep 10.595\tabcellsep -29.648\tabcellsep 13.515\\
\tabcellsep variances\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \\
\tabcellsep assumed\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \\
\tabcellsep Equal\tabcellsep \tabcellsep \tabcellsep -.541\tabcellsep 3.340\tabcellsep .623\tabcellsep -8.067\tabcellsep 14.914\tabcellsep -52.907\tabcellsep 36.774\\
\tabcellsep variances not\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \\
\tabcellsep assumed\tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \tabcellsep \end{longtable} \par
 
\caption{\label{tab_4}Table 4 :}\end{figure}
 			\footnote{Lichen Species as Bio-Accumulator of Some Halogens on Mount Cameroon Volcano, West Africa} 		 		\backmatter   			 
\subsection[{Acknowledgments}]{Acknowledgments}\par
We are grateful for the support by the University of Botswana Gaborone (UBG) where the chemical analyses were performed. We thank Professor Suh Tening Aaron of the University of Buea, who is part of the interdisciplinary research framework under the theme "Understanding the environment of Mount Cameroon". We thank Dr Smith B. Babiaka of the Department of Chemistry, University of Buea, for proof reading of the manuscript. 			  			 
\subsection[{Supplementary Information}]{Supplementary Information}\par
The online version of this article offers supplementary material (https://doi.org/xxxxx). 
\subsection[{Conflict of Interests}]{Conflict of Interests}\par
The authors declare that there is no conflict of interest whatsoever Funding This study did not receive any funding.  
\subsection[{List of Tables}]{List of Tables}			 			  				\begin{bibitemlist}{1}
\bibitem[Safe]{b5}\label{b5} 	 		\textit{},  		 			Safe 		.  		 \xref{http://dx.doi.org/10.1016/j.ecoenv.2012.06.001}{10.1016/j.ecoenv.2012.06.001}.  		 \url{https://doi.org/10.1016/j.ecoenv.2012.06.001}  		83 p. .  	 
\bibitem[Lanham]{b18}\label{b18} 	 		\textit{},  		 			Maryland Lanham 		.  		The Scarecrow Press.  	 
\bibitem[Garty et al. ()]{b24}\label{b24} 	 		\textit{},  		 			J Garty 		,  		 			T Levin 		,  		 			Y Cohen 		,  		 			H Lehr 		.  		2002.  	 
\bibitem[Diana et al. ()]{b21}\label{b21} 	 		\textit{},  		 			P S. L Diana 		,  		 			V Patrícia 		,  		 			Santos Armindo Dos 		.  		 \xref{http://dx.doi.org/10.5772/intechopen.86058}{10.5772/intechopen.86058}.  		2019.  	 	 (Environmental Health IntechOpen) 
\bibitem[Monge-Nájera et al. ()]{b42}\label{b42} 	 		‘A new method to assess air pollution using lichens as bio-indicators’.  		 			J Monge-Nájera 		,  		 			I G María 		,  		 			R R Marta 		,  		 			V H Méndez 		.  	 	 		\textit{Revista de Biological Tropical}  		2002. 50  (1)  p. .  	 
\bibitem[Bajpai and Upreti ()]{b4}\label{b4} 	 		‘Accumulation and toxic effect of arsenic and other heavy metals in a contaminated area of West Bengal, India, in the lichen Pyxine cocoes’.  		 			R Bajpai 		,  		 			D Upreti 		.  	 	 		\textit{Sw.) Nyl. Ecotox. Environ}  		2012.  	 
\bibitem[Notcutt and Davies ()]{b47}\label{b47} 	 		‘Accumulation of volcanogenic fluoride by vegetation: Mt’.  		 			G Notcutt 		,  		 			F Davies 		.  		 \xref{http://dx.doi.org/10.1016/0377-0273(89}{10.1016/0377-0273(89}.  		 \url{https://doi.org/10.1016/0377-0273(89}  	 	 		\textit{Journal of Volcanology and Geothermal Research}  		1989. 329  (333)  p. .  	 
\bibitem[Donahue ()]{b22}\label{b22} 	 		‘Air Pollution and Air Quality’.  		 			N Donahue 		.  	 	 		\textit{Green Chemistry: An Inclusive Approach},  				2018. Elsevier. p. .  	 
\bibitem[Brodeková et al. ()]{b9}\label{b9} 	 		‘An assessment of epiphytic lichen diversity and environmental quality in Knocksink Wood Nature Reserve’.  		 			L Brodeková 		,  		 			A Gilmer 		,  		 			P Dowding 		,  		 			H Fox 		,  		 			GuttováA 		.  		 \xref{http://dx.doi.org/10.3318/BIOE.2006.106.3.215}{10.3318/BIOE.2006.106.3.215}.  		 \url{https://doi.org/10.3318/BIOE.2006.106.3.215}  	 	 		\textit{Proceedings of the Royal Irish Academy}  		2006. 106 p. .  	 	 (Biology) 
\bibitem[Godinho et al. ()]{b25}\label{b25} 	 		‘Bio-accumulation behaviour of transplants of the lichen Flavoparmelia caperata in relation to total deposition at a polluted location in Portugal’.  		 			R M Godinho 		,  		 			H T Wolterbeek 		,  		 			T G Verburg 		,  		 			M C Freitas 		.  		 \xref{http://dx.doi.org/10.1034/j.1399-3054.2002.1150213.x25}{10.1034/j.1399-3054.2002.1150213.x25}.  		 \url{https://doi.org/10.1016/j.envpol.2007.06.034}  	 	 		\textit{Environmental Pollution}  		2008. 115  (2)  p. .  	 	 (Physiologia Plantarum) 
\bibitem[Lawrey ()]{b37}\label{b37} 	 		‘Biological role of lichen substances’.  		 			J D Lawrey 		.  		 \xref{http://dx.doi.org/10.2307/3242751}{10.2307/3242751}.  		 \url{https://doi.org/10.2307/3242751}  	 	 		\textit{The Bryologist}  		1986. 89 p. .  	 
\bibitem[Daimari ()]{b16}\label{b16} 	 		‘Biomonitoring by epiphytic lichen species Pyxine cocoes (Sw.) Nyl.: Understanding characteristics of trace metal in ambient air of different land uses in mid-Brahmaputra Valley’.  		 			R Daimari 		.  		 \xref{http://dx.doi.org/10.1007/s10661-019-8007-x}{10.1007/s10661-019-8007-x}.  		 \url{https://doi.org/10.1007/s10661-019-8007-x}  	 	 		\textit{Environ. Monit. Assess}  		2020. 192.  	 
\bibitem[Käffer et al. ()]{b33}\label{b33} 	 		‘Corticolous lichens as environmental indicators in urban areas in southern Brazil’.  		 			M I Käffer 		,  		 			S M D A Martins 		,  		 			C Alves 		,  		 			V C Pereira 		,  		 			J Fachel 		,  		 			V M F Vargas 		.  	 	 		\textit{Ecological Indicators}  		2011. 11  (5)  p. .  	 
\bibitem[Bajpai et al. ()]{b3}\label{b3} 	 		‘Determination of atmospheric heavy metals using two lichen species in Katni and Rewa cities’.  		 			R Bajpai 		,  		 			G K Mishra 		,  		 			S Mohabe 		,  		 			D K Upreti 		,  		 			S Nayaka 		.  	 	 		\textit{India. J. Environ. Biol}  		2011. 32 p. .  	 
\bibitem[Schwandner et al. ()]{b51}\label{b51} 	 		‘Diffuse emission of organic trace gases from the flank and the crater of a quiescent active volcano’.  		 			F M Schwandner 		,  		 			T M Seward 		,  		 			A P Gize 		,  		 			P A Hall 		,  		 			V Dietrich 		.  	 	 		\textit{J. Geophys.Res}  		2004. 109 p. D04301.  	 
\bibitem[Bjerke and Dahl ()]{b8}\label{b8} 	 		‘Distribution patterns of usnic acid-producing lichens along local radiation gradients in West Greenland’.  		 			J W Bjerke 		,  		 			T Dahl 		.  		 \xref{http://dx.doi.org/10.1127/0029-5035/2002/0075-0487}{10.1127/0029-5035/2002/0075-0487}.  		 \url{https://doi.org/10.1127/0029-5035/2002/0075-0487}  	 	 		\textit{Nova Hedwigia}  		2002. 75 p. .  	 
\bibitem[Kar et al. ()]{b34}\label{b34} 	 		‘Diversity of epiphytic lichens and their role in sequestration of atmospheric metals’.  		 			S Kar 		,  		 			A C Samal 		,  		 			J P Maity 		,  		 			S Santra 		.  		 \xref{http://dx.doi.org/10.1007/s13762-013-0270-8}{10.1007/s13762-013-0270-8}.  	 	 		\textit{Int. J. Environ. Sci. Technol}  		2014. 11 p. .  	 
\bibitem[Jatinder et al. ()]{b30}\label{b30} 	 		‘Diversity of lichens along altitudinal and land use gradients in the Trans Himalayan cold desert of Ladakh’.  		 			K Jatinder 		,  		 			K Roshni 		,  		 			R Himanshu 		,  		 			D K Upreti 		,  		 			A Tayade 		,  		 			S Hota 		,  		 			O P Chaurasia 		,  		 			R B Srivastava 		.  		 \xref{http://dx.doi.org/10.26438/ijsrbs/v6i1.97104}{10.26438/ijsrbs/v6i1.97104}.  		 \url{https://doi.org/10.26438/ijsrbs/v6i1.97104}  	 	 		\textit{Nature and Science}  		2012. 10  (4) .  	 
\bibitem[Cronin and Sharp ()]{b14}\label{b14} 	 		‘Environmental impacts on health from continuous volcanic activity at Yasur (Tanna) and Ambrym, Vanuatu’.  		 			S Cronin 		,  		 			D Sharp 		.  	 	 		\textit{Int. J. Environ. Health Res}  		2002. 12 p. 123.  	 
\bibitem[Hauck ()]{b28}\label{b28} 	 		‘Epiphytic lichen diversity on dead and dying conifers under different levels of atmospheric pollution’.  		 			M Hauck 		.  		 \xref{http://dx.doi.org/10.1016/j.envpol.2004.09.021}{10.1016/j.envpol.2004.09.021}.  		 \url{https://doi.org/10.1016/j.envpol.2004.09.021}  	 	 		\textit{Environmental Pollution}  		2005. 135 p. .  	 
\bibitem[Srivastava et al. ()]{b54}\label{b54} 	 		\textit{Epiphytic lichen ramalina as indicator of atmospheric metal deposition, along land use gradients in and around binsar Wildlife Sanctuary},  		 			K Srivastava 		,  		 			P Bhattacharya 		,  		 			H Rai 		,  		 			P Nag 		,  		 			R K Gupta 		.  		2015. Kumaun, Western Himalaya; India: Progress and Prosp.  	 
\bibitem[Loppi and Pirintsos ()]{b40}\label{b40} 	 		‘Epiphytic lichens as sentinels for heavy metal pollution at forest ecosystems (central Italy)’.  		 			S Loppi 		,  		 			S A Pirintsos 		.  		 \xref{http://dx.doi.org/10.1016/S0269-7491(02}{10.1016/S0269-7491(02}.  		 \url{https://doi.org/10.1016/S0269-7491(02}  	 	 		\textit{Environmental Pollution}  		2003. 121 p. .  	 
\bibitem[Ayrault et al. ()]{b2}\label{b2} 	 		‘Factors to consider for trace element deposition bio-monitoring surveys with lichen transplants’.  		 			S Ayrault 		,  		 			R Clochiatti 		,  		 			F Carrot 		,  		 			L Daudin 		,  		 			J Bennett 		.  		 \xref{http://dx.doi.org/10.1016/j.scitotenv.2006.10.032}{10.1016/j.scitotenv.2006.10.032}.  		 \url{https://doi.org/10.1016/j.scitotenv.2006.10.032}  	 	 		\textit{The Science of the Total Environment}  		2007. 372 p. .  	 
\bibitem[Weinstein et al. ()]{b61}\label{b61} 	 		‘Fluoride’.  		 			L H Weinstein 		,  		 			A Davison 		,  		 			U Arndt 		.  	 	 		\textit{Recognition of Air Pollutant Injury to Vegetation: A Pictorial Atlas. 2 nd Edition},  				 (Pittsburgh, PA)  		1998. p. .  	 
\bibitem[Dey and Giri ()]{b20}\label{b20} 	 		‘Fluoride fact on human health and health problems: A review’.  		 			S Dey 		,  		 			B Giri 		.  	 	 		\textit{Medical and Clinical Reviews}  		2015. 2  (2) .  	 
\bibitem[Garcia and Borgnino ()]{b23}\label{b23} 	 		‘Fluoride in the context of the environment’.  		 			M G Garcia 		,  		 			L Borgnino 		.  	 	 		\textit{Chemistry, Analysis, Function and Effects},  				 			V R Preedy 		 (ed.)  		 (London)  		2015. The Royal Society of Chemistry. p. .  	 
\bibitem[Culberson and Culberson ()]{b15}\label{b15} 	 		‘Future directions in lichen chemistry’.  		 			C F Culberson 		,  		 			W L Culberson 		.  		 \xref{http://dx.doi.org/10.1639/0007-2745}{10.1639/0007-2745}.  		 \url{https://doi.org/10.1639/0007-2745}  	 	 		\textit{The Bryologist}  		2001. 2001. 104 p. 104.  	 	 (0230: fdilc]2.0.CO) 
\bibitem[Delancey and Mark ()]{b17}\label{b17} 	 		\textit{Historical Dictionary of the Republic of Cameroon},  		 			M W Delancey 		,  		 			D D Mark 		.  		2000.  	 	 (3rd ed.) 
\bibitem[Smodis ()]{b53}\label{b53} 	 		‘Investigation of trace element atmospheric pollution by nuclear analytical techniques at a global scale: Harmonised approaches supported by the IAEA’.  		 			B Smodis 		.  		 \xref{http://dx.doi.org/10.1016/j.jenvman.2006.08.007}{10.1016/j.jenvman.2006.08.007}.  		 \url{https://doi.org/10.1016/j.jenvman.2006.08.007}  	 	 		\textit{Journal of Environmental Management}  		2007. 85 p. .  	 
\bibitem[Lorenzini et al. ()]{b41}\label{b41} 	 		‘Leaves of Pittosporum tobira as indicators of airborne trace element and PM10 distribution in central Italy’.  		 			G Lorenzini 		,  		 			C Grassi 		,  		 			C Nali 		,  		 			A Petti 		,  		 			S Loppi 		,  		 			L Tognoti 		.  	 	 		\textit{Atmospheric Environment}  		2006. 40  (22)  p. .  	 
\bibitem[Larsen et al. ()]{b36}\label{b36} 	 		‘Lichen and bryophyte distribution on oak in London in relation to air pollution and bark acidity’.  		 			R S Larsen 		,  		 			J N B Bell 		,  		 			P W James 		,  		 			P J Chimonides 		,  		 			F J Rumsey 		,  		 			A Tremper 		,  		 			O W Purvis 		.  		 \xref{http://dx.doi.org/10.1016/j.envpol.2006.03.033}{10.1016/j.envpol.2006.03.033}.  		 \url{https://doi.org/10.1016/j.envpol.2006.03.033}  	 	 		\textit{Environmental Pollution}  		2007. 146 p. .  	 
\bibitem[Jovans ()]{b32}\label{b32} 	 		‘Lichen bioindication of biodiversity, air quality and climate: baseline results from monitoring in Washington’.  		 			S Jovans 		.  	 	 		\textit{Oregon and California. General Technical Report}  		2008.  	 
\bibitem[Stefano ()]{b55}\label{b55} 	 		‘Lichen Diversity and Lichen Transplants as Monitors of Air Pollution in a Rural Area of Central Italy’.  		 			Luisa Stefano 		,  		 			F 		.  		 \xref{http://dx.doi.org/10.1007/s10661-006-4937-1}{10.1007/s10661-006-4937-1}.  	 	 		\textit{Environmental Monitoring and Assessment}  		2006. 114 p. .  	 
\bibitem[Pinhoa et al. ()]{b48}\label{b48} 	 		‘Lichen functional groups as ecological indicators of the effects of land-use in Mediterranean ecosystems’.  		 			P Pinhoa 		,  		 			A Bergamini 		,  		 			P Carvalhod 		,  		 			C Branquinhoa 		,  		 			S Stofer 		,  		 			S Scheidegger 		,  		 			C Máguas 		,  		 			C 		.  		 \xref{http://dx.doi.org/10.1016/j.ecolind.2011.09.022}{10.1016/j.ecolind.2011.09.022}.  		 \url{https://doi.org/10.1016/j.ecolind.2011.09.022}  	 	 		\textit{Ecological Indicators}  		2012. 15 p. .  	 
\bibitem[Bennett ()]{b7}\label{b7} 	 		‘Lichens and air pollution’.  		 			J P Bennett 		.  	 	 		\textit{International Society of Enviromental Botanists}  		2006. 12  (4) .  	 
\bibitem[Chettri et al. ()]{b12}\label{b12} 	 		‘Lichens as a tool for biogeochemical prospecting’.  		 			M K Chettri 		,  		 			T Sawidis 		,  		 			S Karataglis 		.  		 \xref{http://dx.doi.org/10.1016/S0341-8162}{10.1016/S0341-8162}.  	 	 		\textit{Ecotoxicology and Environmental Safety}  		1997. 38  (3)  p. .  	 
\bibitem[Grasso et al. ()]{b27}\label{b27} 	 		‘Lichens as bioindicators in volcanic areas: Mt. Etna and Vulcano Island (Italy)’.  		 			M F Grasso 		,  		 			R Clocchiatti 		,  		 			F Carrot 		,  		 			Deschamps 		,  		 			F Vurro 		.  	 	 		\textit{Environmental Geology}  		1999. 37 p. .  	 
\bibitem[Brodo et al. ()]{b10}\label{b10} 	 		\textit{Lichens of North America},  		 			I M Brodo 		,  		 			S D Sharnoff 		,  		 			S Sharnoff 		.  		2001. New Haven: Yale University Press.  	 
\bibitem[Shukla et al. ()]{b52}\label{b52} 	 		\textit{Lichens to Biomonitor the Environment},  		 			V Shukla 		,  		 			D K Upreti 		,  		 			R Bajpai 		.  		 \xref{http://dx.doi.org/10.1007/978-81-322-1503-5}{10.1007/978-81-322-1503-5}.  		 \url{https://doi.org/10.1007/978-81-322-1503-5}  		2014. p. .  	 
\bibitem[Morris and Purvis ()]{b43}\label{b43} 	 		\textit{London: The Natural History Museum},  		 			J Morris 		,  		 			W Purvis 		.  		2007. p. 19.  	 	 (Lichens (Life)) 
\bibitem[Van Herk et al. ()]{b59}\label{b59} 	 		‘Long-term monitoring in the Netherlands suggests that lichens respond to global warming’.  		 			C M Van Herk 		,  		 			A Aptroot 		,  		 			H F Van Dobben 		.  		 \xref{http://dx.doi.org/10.1006/lich.2002.0378}{10.1006/lich.2002.0378}.  		 \url{https://doi.org/10.1006/lich.2002.0378}  	 	 		\textit{Lichenologist}  		2002. 34  (2)  p. .  	 
\bibitem[Jó?wiak ()]{b35}\label{b35} 	 		‘Macroscopic changes of Hypogymnia physodes (L.) Nyl. in antropogenic stress conditions’.  		 			M Jó?wiak 		.  	 	 		\textit{Monit. ?rod. Przyr}  		2012. 13 p. .  	 
\bibitem[Bargagli ()]{b6}\label{b6} 	 		‘Moss and Lichen Biomonitoring of Atmospheric Mercury: A Review’.  		 			R Bargagli 		.  		 \xref{http://dx.doi.org/10.1016/j.scitotenv.2016.07.202}{10.1016/j.scitotenv.2016.07.202}.  		 \url{https://doi.org/10.1016/j.scitotenv.2016.07.202}  	 	 		\textit{Science of the Total Environment}  		2016. 572 p. 31.  	 
\bibitem[Ndlovu et al. ()]{b45}\label{b45} 	 		‘Moss and Lichen Biomonitoring of Atmospheric Pollution in the Western Cape Province (South Africa)’.  		 			N B Ndlovu 		,  		 			M V Frontasyeva 		,  		 			R T Newman 		,  		 			P Maleka 		.  		 \xref{http://dx.doi.org/10.4236/ajac.2019.103008}{10.4236/ajac.2019.103008}.  		 \url{https://doi.org/10.4236/ajac.2019.103008}  	 	 		\textit{American Journal of Analytical Chemistry}  		2019. 10 p. .  	 
\bibitem[Déruelle et al. ()]{b19}\label{b19} 	 		‘Mount Cameroon: an active volcano of the Cameroon Line’.  		 			B Déruelle 		,  		 			N'ni 		,  		 			R Kombou 		.  	 	 		\textit{Journal of African Earth Science}  		1997. 6  (2)  p. .  	 
\bibitem[Suh et al. ()]{b56}\label{b56} 	 		‘Olivine-hosted glass inclusions from Scoriae erupted in 1954-2000 at Mount Cameroon volcano, West Africa’.  		 			C E Suh 		,  		 			J F Luhr 		,  		 			M S Njome 		.  		 \xref{http://dx.doi.org/10.1016/j.jvolgeores.2007.07.004}{10.1016/j.jvolgeores.2007.07.004}.  		 \url{https://doi.org/10.1016/j.jvolgeores.2007.07.004}  	 	 		\textit{Journal of Volcanology and Geothermal Research}  		2008. 169 p. .  	 
\bibitem[Rani et al. ()]{b50}\label{b50} 	 		‘Periodic monitoring with lichen Phaeophyscia hispidula (ach.) Moberg in Dehradun city’.  		 			M Rani 		,  		 			V Shukla 		,  		 			D K Upreti 		,  		 			G S Rajwar 		.  	 	 		\textit{The Environmentalist}  		2011. 31  (4)  p. .  	 
\bibitem[Temple et al. ()]{b58}\label{b58} 	 		\textit{Peroxyacetyl nitrates (PAN) and other minor pollutants. Recognition of Air Pollutant Injury to Vegetation: A Pictorial Atlas. 2nd Edition. Air and waste management association},  		 			P J Temple 		,  		 			J E J Sun 		,  		 			G H M Krause 		.  		1998. Pittsburgh. p. .  	 
\bibitem[Nelson and Wheeler ()]{b46}\label{b46} 	 		\textit{Persistence of epiphytic lichens along a tephra-depth gradient produced by the 2011 Puyehue-Cordón Caulle eruption in Parque Nacional},  		 			P R Nelson 		,  		 			T B Wheeler 		.  		 \url{https://bit.ly/2X9Mqj0}  		2016. Puyehue, Chile. Bosque. 37 p. .  	 
\bibitem[Munzi et al. ()]{b44}\label{b44} 	 		‘Physiological response of the epiphytic lichen Evernia prunastri (L.) Ach.to ecologically relevant nitrogen concentrations’.  		 			S Munzi 		,  		 			L Paoli 		,  		 			E Fiorini 		,  		 			S Loppi 		.  		 \xref{http://dx.doi.org/10.1016/j.envpol.2012.07.001}{10.1016/j.envpol.2012.07.001}.  		 \url{https://doi.org/10.1016/j.envpol.2012.07.001}  	 	 		\textit{Environmental Pollution}  		2012. 171 p. .  	 
\bibitem[Hess et al. ()]{b29}\label{b29} 	 		‘Production of oxalates in vitro by microbes isolated from rock surfaces with prehistoric paints in the Lower Pecos Region’.  		 			D Hess 		,  		 			D J Coker 		,  		 			J M Loutsch 		,  		 			Russ 		,  		 			J 		.  		 \xref{http://dx.doi.org/10.1002/gea.20208}{10.1002/gea.20208}.  		 \url{https://doi.org/10.1002/gea.20208}  	 	 		\textit{Texas. Geoarchaeology}  		2008. 23  (1)  p. .  	 
\bibitem[Walker et al. ()]{b60}\label{b60} 	 		‘Regional variation in the chemical composition of winter snow pack and terricolous lichens in relation to sources of acid emissions in the Usa river basin, northeast European Russia’.  		 			T R Walker 		,  		 			P D Crittenden 		,  		 			S D Young 		.  		 S0269-7491(03)00080-0.  		 \url{https://doi.org/10.1016/}  	 	 		\textit{Environmental}  		2003. 125 p. .  	 
\bibitem[Linhares et al. ()]{b38}\label{b38} 	 		‘Safety evaluation of fluoride content in tea infusions consumed in the Azores -a volcanic region with water springs naturally enriched in fluoride’.  		 			D Linhares 		,  		 			P Garcia 		,  		 			T Ferreira 		,  		 			Rodrigues 		.  	 	 		\textit{Biological Trace Element Research}  		2017. 179 p. .  	 
\bibitem[Suh et al. ()]{b57}\label{b57} 	 		‘The 1999 and 2000 eruptions of Mount Cameroon: eruption behaviour and petrochemistry of lava’.  		 			C E Suh 		,  		 			R S J Sparks 		,  		 			J G Fitton 		,  		 			S N Ayonghe 		,  		 			C Annen 		,  		 			R Nana 		,  		 			A Luckman 		.  		 \xref{http://dx.doi.org/10.1007/s00445-004-0388-0}{10.1007/s00445-004-0388-0}.  		 \url{http://dx.doi.org/10.1007/s00445-004-0388-0}  	 	 		\textit{Bulletin}  		2003. 65 p. .  	 
\bibitem[Jitka et al. ()]{b31}\label{b31} 	 		‘The characteristics of rare earth elements in bulk precipitation, through fall, foliage and lichens in the Lesní potok catchment and its vicinity’.  		 			S Jitka 		,  		 			N Tomás 		,  		 			R Jan 		,  		 			M Martin 		,  		 			K Petra 		,  		 			Petra S Ludek 		.  	 	 		\textit{Geochemistry: Exploration, Environment}  		2010. 10 p. .  	 	 (Analysis) 
\bibitem[Poblet et al. ()]{b49}\label{b49} 	 		‘The use of epiphytic Antarctic lichens (Usnea aurantiacoatra and U. antarctica) to determine deposition patterns of heavy metals in the Shetland Islands’.  		 			A Poblet 		,  		 			S Andrade 		,  		 			M Scagliola 		,  		 			C Vodopivez 		,  		 			A Curtosi 		,  		 			A Pucci 		,  		 			J Marcovecchio 		.  	 	 		\textit{Antarctica. Science of the Total Environment}  		1997. 207  (2-3)  p. .  	 
\bibitem[Llop et al. ()]{b39}\label{b39} 	 		‘The use of lichen functional group asindicators of air quality in a mediterranean urban environment’.  		 			E Llop 		,  		 			P Pinho 		,  		 			P Matos 		,  		 			M J Pereira 		,  		 			C Branquinho 		.  		 \xref{http://dx.doi.org/10.1016/j.ecolind.2011.06.005}{10.1016/j.ecolind.2011.06.005}.  		 \url{https://doi.org/10.1016/j.ecolind.2011.06.005}  	 	 		\textit{Ecological Indicators}  		2012. 13 p. .  	 
\bibitem[Conti et al. ()]{b13}\label{b13} 	 		\textit{Trace elements deposition in the Tierra del Fuego region (south Patagonia) by using lichen transplants after the Puyehue-Cordón Caulle (north Patagonia) volcanic eruption in 2011. Environmental Science Pollution Research International},  		 			M E Conti 		,  		 			R Jasan 		,  		 			M G Finoia 		,  		 			I Iavicoli 		,  		 			R Plá 		.  		 \url{https://bit.ly/39K7ajI}  		2016. 23 p. .  	 
\bibitem[Ahmad et al. ()]{b0}\label{b0} 	 		‘Use of bio-monitors to assess the atmospheric changes’.  		 			S Ahmad 		,  		 			M Daud 		,  		 			I H Qureshi 		.  	 	 		\textit{Proceeding Pakistan Academy of Science}  		2007. 44  (3)  p. .  	 
\bibitem[Golubev et al. ()]{b26}\label{b26} 	 		‘Using of lichens for assessment of uranium atmosphere pollution’.  		 			A Golubev 		,  		 			V Golubeva 		,  		 			A Korableva 		,  		 			N Krylov 		,  		 			V Kuznetsova 		,  		 			S Mavrin 		,  		 			Aleinikov 		,  		 			A 		.  	 	 		\textit{Environment}  		2006. 3  (36) .  	 
\bibitem[Aiuppa et al. ()]{b1}\label{b1} 	 		‘Volcanic plume monitoring at Mount Etna by diffusive (passive) sampling’.  		 			A Aiuppa 		,  		 			S Bellomo 		,  		 			Alessandro W Federico 		,  		 			C Ferm 		,  		 			M Valenza 		,  		 			M 		.  	 	 		\textit{J. Geophys. Res}  		2004. 109 p. .  	 
\bibitem[Chen et al. ()]{b11}\label{b11} 	 		‘Weathering of rocks induced by lichen colonization’.  		 			J Chen 		,  		 			H Blume 		,  		 			L Beyer 		.  		 \xref{http://dx.doi.org/10.1016/S0341-8162(99}{10.1016/S0341-8162(99}.  		 \url{https://doi.org/10.1016/S0341-8162(99}  	 	 		\textit{Catena}  		2000. 39 p. .  	 
\bibitem[WHO (2002) Fluorides. Geneva, World Health Organization Environmental Health Criteria]{b62}\label{b62} 	 		‘WHO (2002) Fluorides. Geneva, World Health Organization’.  	 	 		\textit{Environmental Health Criteria}  		227 p. 268.  	 
\end{bibitemlist}
 			 		 	 
\end{document}
