Use of mosses and lichens as indicators of environmental contamination with heavy metals.doc

use of mosses and lichens as indicators of environmental contamination with heavy metals. maria gapeeva papanin institute for biology of inland waters, russian academy of sciences, russia;1. introductionan increasing impact of industrial discharges on the surrounding ecosystems raises interest in heavy metals and their levels in abiotic media and biological objects. cu, cr, zn, cd, pb, and hg are the common metals of interest. also, industrial emissions of rare earth elements to ecosystems have increased, but knowledge of the environmental fate of these metals is limited. availably literary information indicates that anthropogenic emissions of rare earth elements cannot simply be ignored (krachler et al., 2003). heavy metals pollution of the catchment areas of small and medium rivers of northern european russia historically has not been of concern. they are regarded safe in respect because they are remote from large industrial centers and not directly subjected to industrial impact (reimann et al., 2001). mosses and lichens have the ability to reflect prevailing atmospheric metal ions pollutant levels in their tissues without significant adverse effects on their survival or growth( adamo, 2000, as cited in boamponsem et al., 2010). since mosses and lichens grow for several years, the levels of pollutants in them may be used for estimating the exposure of the environment to these pollutants. though there is a critical review of possible to estimate atmospheric deposition of heavy metals by analysis of terrestrial mosses (aboal et al., 2010) , they use extensively within the european moss survey. mosses have already been used as biomonitors of atmospheric heavy metal contamination of the central region of russia (sergiev posad, tula, tver, udmurt republic) (harmens et al., 2010). this original case study is aimed to determine the levels of heavy and rare earth metals in mosses and lichens of the regions that are remote from the major industrial centers. we focused on the uvod reservoir watershed as it used to supply 80% of the water needs of the city of ivanovo. 2. study location, methods and materials moss samples were collected in 2005 and 2006 in the valleys of small and medium rivers in the vologda and kostroma regions. the collection area situated between 5800 - 6050 north latitude and 3500 4510 east longitude: 9 samples, area no. 3; 68 samples, area no. 2 (uvod reservoir watershed, ivanovo region). lichen samples were collected on the watersheds of uvod reservoir, n=69, area no. 2 and those of ivane, gluhoe, vele, bragino, mohovoe, and bolshoe yaichko lakes situated in the valday national park, novgorod region (n=47, area no. 3). the collection sites locations are shown on fig. 1. the following species were selected for monitoring: mosess : epiphyte pylaisia polyantha (hedw.) bruch et al. (pylaisia); lichens: foliated (. hypogymnia, pamelipsis, parmelia ) and bushy ( . evernia, alectoria, usnea). photobions of lichens consist of green algae substantially from generation trebouxia . we selected these species because they are ubiquitous and often grow in adjacent ecotopes.fig.1. location of sampling areas.all pollutants found on their surface and/or penetrating into these mosses and lichens are of external origin, their sources being air and atmospheric precipitation. in winter 2008 snow samples were taken at 20 different locations of the uvod reservoir. samples were obtained as snow kerns throughout the whole depth of snow cover (i.e., from ground level to the top of the snow layer) as specified by gost 17.1.5.05-85 standard. upon collection, the snow kerns were placed into clean polyethylene bags and stored frozen until analysis. a typical sample preparation procedure for moss and lichens was as follows: a 0.3g sample of plant material was air dried, homogenized, and subjected to wet digestion with 6 ml of a 2 : 1 nitric acidhydrogen peroxide mixture in a speedwave mws-3+ microwave oven according to the vendor recommended program. water distilled in a distillacid bsb-939-ir device was added to the resultant solution to a final volume of 50 ml. the amounts of al, ti, cr, cu, zn, cd, pb, and rare earth elements were determined by the inductively coupled plasmamass spectrometry (icpms) method by means of a drc-e mass spectrophotometer with the use of external calibration. a blank sample was prepared with distilled water following the same method as that of metals. snow samples were allowed to thaw, filtered and analyzed without further treatment. 10 ml unfiltered melt water was digested in the mixture of 2 ml 65% hno3 and 3 ml of 30% h2o2 in a microwave digestion system (175 oc, 15 min, speedwavetm mws-3, berghof) . rare earth metals were grouped in the three categories: light - la, ce, nd, medium - sm, eu, gd,tb, dy and heavy- er,yb, lu (aubert et al., 2002). the statistica for windows 6.1 software was used for statistical treatment of the data. 3. resultsmeans, medians and maxima for the heavy metals and rare earth metals content in p. polyantha are presented in table 1. since the numbers of observations on p. polyantha were considerably different, the median is a more adequate characteristic of the statistical sample than the mean in the given case. in addition, the median is unaffected by extremely high or low values that may be not characteristic of the general population, which are sometimes found for some metals. analysis of the distributions of the heavy metal contents of p. polyantha (table below) indicated that their arithmetic means were lower than the medians, especially for p. polyantha from area no.3metal area no. 3 (n=9) area no. 2 (n=69)range md (harmens et al., 2010) mdmax mdmaxlin.a.n.a.n.a.1.11.03.5n.a.mgn.a.n.a.n.a.117516564016n.a.al21617278136123311313536850can.a.n.a.n.a.5186454012995n.a.scn.a.n.a.n.a.0.930.941.89n.a.ti88432296866174n.a.vn.a.n.a.n.a.2.242.193.752.27cr2.71.935.985.74.715.23.54fe26407381075210494280679con.a.n.a.n.a.1.451.196.39n.a.nin.a.n.a.n.a.3028722.74cu7.64.92214.714.728.98.94zn35.8298063.76115840.1gan.a.n.a.n.a.0.70.71.6n.a.as12.94.5410.60.51.40.23se0.500.271.430.0150.0190.050n.a.rbn.a.n.a.n.a.181572n.a.srn.a.n.a.n.a.4536167n.a.yn.a.n.a.n.a.0.590.862.00n.a.zrn.a.n.a.n.a.0.80.81.9n.a.mon.a.n.a.n.a.0.650.501.75n.a.cd0.290.191.050.0030.0020.010.24snn.a.n.a.n.a.0.350.330.96n.a.sbn.a.n.a.n.a.0.330.330.600.12ban.a.n.a.n.a.204174766n.a.wn.a.n.a.n.a.0.310.310.65n.a.tln.a.n.a.n.a.0.280.240.99n.a.pb6.424.7113.7928.922.3317n.a.ce3.960.8119.453.933.69.86n.a.pr0.370.091.560.410.391.04n.a.sm0.260.071.060.290.270.72n.a.nd1.450.356.041.561.463.87n.a.eu0.070.020.280.100.100.26n.a.gd0.660.222.500.320.290.79n.a.tb0.030.010.130.040.040.09n.a.dy0.160.040.650.200.190.46n.a.ho0.030.0080.120.040.0340.08n.a.er0.080.020.320.100.090.21n.a.tm0.010.0030.040.030.0120.03n.a.yb0.060.0140.230.080.0760.17n.a.lu0.0080.0020.030.0120.0110.02n.a.table 1 .the means (m), median (md) and maximum (max) heavy metal concentrations in mosses (g/g dw)the variance of heavy metal content for the different lichen groups was statistically not significant. therefore, for each collection site all the lichen samples were combined into one. table 2 lists heavy metal content of the lichen samples collected from the uvod reservoir watershed. similarly, table 3 shows heavy metal content for the snow samples. hm year 2007 (collection area no. 2) year 2008 (collection area no. 2) year 2007 (collection area no. 1)range(djingova et al., 2004)mmaxmmaxmmaxal2168491423841315513210260-2000ti105279725026410416-51cr7,530,51,12,33,15,71,0-12,4fen.a.n.a.n.a.n.a.10751935n.a.cu14,328,64.710.49,115,31,39-25,5zn0.200.683.537.85124,9191,315,6-304cd1,33,120.93.80,51,350,05-1,92pb16,038,98.713.68,816,40,75-46ce2,49,10.861.61,43,510,22-0,55pr0.292.45n.a.n.a.0.163.51n.a.sm0.201.73n.a.n.a.0.110.30n.a.nd1.139.7n.a.n.a.0.611.74n.a.eu0.060.45n.a.n.a.0.050.15n.a.gd0.825.02n.a.n.a.0.631.74n.a.light rare earth metals elements1.683.05medium rare earth metals1.173.430.230.790,862,04medium rare earth metals0.120.390.050.250,070,18table 2. level of heavy metals (g /g dw) in samples of the lichen from the uvod reservoir watershed and the valday national park.hm melt waterunfiltered melt water 22082 200822 1995 2008msdmaxmsdmaxmsdmaxcu230,966.8113.46,812,92,9zn6134 8.2123.816,523,73,7cd0,010,030,010.340.90.310,10,180,06pb0,040,20,08 9.0112.351,32,80,8light rare earth metals0,040,090,02nn0,150,270,06medium rare earth metals0,0040,0070,0020,020,0270,008heavy rare earth metals0,00030,0010,00050,0020,010,005table 3.metal levels (ppb) in filtered and unfiltered melt water from the uvod watershed (collection area no. 2).4. discussion4.1. mosses it is important to bear in mind that sources other than air pollution may influence the metal content in the mosses. the possible sources include: a) long-range atmospheric transport for v, zn, as, cd, pb, bi, sn, sb; b) local point sources for co, ni, cu; c) root uptake in vascular plants from soil, and subsequent transfer to mosses by leaching from living or dead plant material for mg, ca, sr, ba, mn, and zn; d) mineral particles, mainly windblown soil dust for li, al ,sc, ti ,cr, fe, ga ,y, zr, nb, , hf, ta, th, rare earth metals and u (berg et al., 1997). for the mosses samples collected in area no. 2, we found significant correlation between rare earth metals content and that for metals from other groups. usually these metals originate from mineral particles, mainly deposited from windblown dust. table 4 and fig. 2 highlight the relationship between al, sc, ti, v, cr, fe, co, ga, ge, y, zr and other metals. as it can be seen on fig. 3 there is significant positive correlation between the values of fe and al content in the samples. laceprndsmeugdtbdyhoertmyblumg0,43-0,26-0,28-0,31-0,31-0,32al0,900,870,860,850,850,290,840,800,750,680,650,620,610,58ca0,55-0,25-0,31-0,34-0,38-0,38-0,38sc0,520,480,490,490,460,500,510,500,490,480,460,450,41ti0,750,710,680,670,680,400,660,630,570,510,480,450,430,40v0,660,670,710,720,690,740,770,810,830,850,850,860,87cr0,630,580,570,550,560,410,560,530,480,400,380,340,350,33fe0,900,900,860,850,860,350,830,790,730,660,630,610,600,58co0,500,540,480,470,510,420,430,400,310,25cu0,320,300,330,340,330,370,400,440,450,470,460,480,48ga0,920,910,890,880,890,450,870,830,770,700,670,650,640,62ge0,470,380,400,390,370,240,420,440,430,400,380,360,360,33as0,750,730,700,690,700,290,680,630,560,500,470,440,430,44sr-,26-,27-,240,53-0,27-,28-0,33-0,37-0,39-0,43-0,42-0,42y0,850,870,910,920,900,240,950,970,990,990,990,980,970,96zr0,390,360,370,380,370,400,410,420,420,440,450,430,41nb0,730,690,680,670,680,290,670,650,600,560,540,520,510,48mo0,450,420,410,390,400,340,400,390,340,290,270,24cd0,780,750,770,760,750,430,770,760,740,710,690,680,680,66sb0,340,270,310,320,280,350,390,420,420,430,410,400,39te0,320,290,250,280,57cs0,580,540,510,500,490,460,430,360,320,280,270,260,25ba0,84-0,26-0,28-0,30-0,33-0,32-0,32hf0,490,450,470,480,450,490,490,510,500,510,520,510,48ta0,400,360,350,360,330,360,350,320,300,270,260,27w0,310,270,270,260,280,280,290,280,240,24au0,260,250,250,240,260,250,24bi0,660,610,650,650,630,320,670,690,690,660,660,640,640,64th0,750,730,700,700,720,340,680,650,590,530,490,470,450,42u0,600,630,590,590,590,550,520,470,420,390,370,370,38table 4. correlation coefficients between metal content for selected metals in mosses collected in area no. 2. fig.2. the relationship between la and al in mosses collected in the area no. 2the lead content for the moss samples collected in the area no. 2 correlates strongly only with that of antimony (r=0, 50, p0.7) accounted for 55% of all variations and consist of al, cu, as, and all rare earth elements. the loadings of the second factor consist of cd, eu, gd and account for 27%. since the major source of atmospheric al and rare earth elements is dust resulting from wind erosion of soil, we refer to it as soil erosion factor. similarly, since eu is the most volatile member of the lanthanide series, the second factor elements can be referred as long range transport of air pollution. therefore the difference in heavy metals content in lichen between years 2007 and 2008 is attributed to various amounts of dust deposited on the lichen surfac