青藏高原林线森林汞的空间分布格局及对大气环境汞污染的指示
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摘要
汞是引人关注的全球性污染物,偏远地区汞的源汇关系是当前研究的重点.由于其特殊的地理环境与大面积在线监测的不便,青藏高原大气汞的污染特征尚不明确.本研究根据青藏高原季风的传播路径,设置了云南-西藏与四川-西藏两条采样带,通过测定样带上林线森林各个组分的汞含量,来反演大气汞的污染状况.研究结果表明,青藏高原林线区域的冷杉凋落物、树叶树皮与表层土壤的汞含量均表现为越靠近青藏高原腹地,汞浓度越低.特别冷杉凋落物在云南与西藏、四川与西藏的交界区域汞浓度为60—70 ng·g~(-1),而昌都地区汞浓度仅为20—30 ng·g~(-1).此外还发现,凋落物与表层土壤的总汞含量在空间分布上与经度正相关,与纬度负相关.通过综合分析排放清单与大气环流资料,其原因可总结为:越靠近青藏高原腹地,局地源的汞排放与大气环流输送的汞均显著减少,使得大气环境汞含量降低,进而导致植被与土壤汞含量相应下降.本研究表明了凋落物中的总汞含量可作为大气环境汞污染的指示指标,证实了南亚、东南亚及我国的四川盆地与云贵高原是青藏高原大气汞污染的潜在排放源.
Mercury(Hg) is a global atmospheric pollutant, and its source-sink relationships in remote regions is the hotpot currently. Due to the specific environment and inconvenience of on-line measurements, the characteristics of atmospheric Hg pollution in Tibetan Plateau(TP) still remains unclear. In this study, two series of sampling sets(Yunnan-Southeast TP, Sichuan-Southeast TP) were set to explore such atmospheric Hg pollution by using Hg concentration in litterfall and in surface soils. The results showed that Hg concentration in litterfall, foliage, bark and surface soils decreased with the monsoon direction into TP. Specifically, Hg concentration in litterfall ranged 60—70 ng·g~(-1) in the boundary regions of Yunnan-Tibet and Sichuan-Tibet, while ranged 20—30 ng·g~(-1) in Changdu. Based on the Hg emission inventory and the meteorological data, we suggested that further in back-land of TP, the local anthropogenic emission dramatically decreased, and Hg transportation by general atmospheric circulation also intensively decreased, leading to reduce of Hg concentration in vegetation and surface soil. Our study suggested that the litterfall Hg concentration from Abies at timberline of TP can be as the index to predict the atmospheric Hg concentration in remote regions, and verified that South Asia, Southeast Asia, Sichuan Basin and Yunnan-Guizhou Plateau were the potential regions for Hg pollution sources in TP.
Mercury(Hg) is a global atmospheric pollutant, and its source-sink relationships in remote regions is the hotpot currently. Due to the specific environment and inconvenience of on-line measurements, the characteristics of atmospheric Hg pollution in Tibetan Plateau(TP) still remains unclear. In this study, two series of sampling sets(Yunnan-Southeast TP, Sichuan-Southeast TP) were set to explore such atmospheric Hg pollution by using Hg concentration in litterfall and in surface soils. The results showed that Hg concentration in litterfall, foliage, bark and surface soils decreased with the monsoon direction into TP. Specifically, Hg concentration in litterfall ranged 60—70 ng·g~(-1) in the boundary regions of Yunnan-Tibet and Sichuan-Tibet, while ranged 20—30 ng·g~(-1) in Changdu. Based on the Hg emission inventory and the meteorological data, we suggested that further in back-land of TP, the local anthropogenic emission dramatically decreased, and Hg transportation by general atmospheric circulation also intensively decreased, leading to reduce of Hg concentration in vegetation and surface soil. Our study suggested that the litterfall Hg concentration from Abies at timberline of TP can be as the index to predict the atmospheric Hg concentration in remote regions, and verified that South Asia, Southeast Asia, Sichuan Basin and Yunnan-Guizhou Plateau were the potential regions for Hg pollution sources in TP.
引文
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[13] MA M,WANG D,DU H,et al.Mercury dynamics and mass balance in a subtropical forest,southwestern China[J].Atmospheric Chemistry & Physics Discussions,2016,15(24):35857-35880.
[14] SLEMR F,ANGOT H,DOMMERGUE A,et al.Comparison of mercury concentrations measured at several sites in the Southern Hemisphere[J].Atmospheric Chemistry and Physics,2015,14(22):3125-3133.
[15] WANG Z,ZHANG X,XIAO J,et al.Mercury fluxes and pools in three subtropical forested catchments,southwest China[J].Environmental Pollution,2009,157(3):801-808.
[16] ZHOU J,FENG X,LIU H,et al.Examination of total mercury inputs by precipitation and litterfall in a remote upland forest of Southwestern China[J].Atmospheric Environment,2013,81(x):364-372.
[17] ZHOU J,WANG Z,ZHANG X,et al.Distribution and elevated soil pools of mercury in an acidic subtropical forest of southwestern China[J].Environmental Pollution,2015,202(7):187-195.
[18] CHOI H D,HOLSEN T M,HOPKE P K.Atmospheric mercury (Hg) in the Adirondacks:Concentrations and sources[J].Environmental Science & Technology,2008,42(15):5644-5653.
[19] DEMERS J D,DRISCOLL C T,FAHEY T J,et al.Mercury cycling in litter and soil in different forest types in the Adirondack region,New York,USA[J].Ecological Applications,2007,17(5):1341-1351.
[20] LARSSEN T,DE H W,WIKER M,et al.Mercury budget of a small forested boreal catchment in southeast Norway[J].Science of the Total Environment,2008,404(2):290-296.
[21] MASON R P,LAWSON N M,SHEU G R,et al.Annual and seasonal trends in mercury deposition in Maryland[J].Atmospheric Environment,2000,34(11):1691-1701.
[22] SCHWESIG D,MATZNER E.Pools and fluxes of mercury and methylmercury in two forested catchments in Germany[J].Science of the Total Environment,2000,260(1):213-223.
[23] TANG R,WANG H,LUO J,et al.Spatial distribution and temporal trends of mercury and arsenic in remote timberline coniferous forests,eastern of the Tibet Plateau,China[J].Environmental Science & Pollution Research,2015,22(15):11658-11668.
[24] FU X W,FENG X,DONG Z Q,et al.Atmospheric gaseous elemental mercury (GEM) concentrations and mercury depositions at a high-altitude mountain peak in south China[J].Atmospheric Chemistry and Physics,2010,10(5):2425-2437.
[25] LUO Y,DUAN L,WANG L,et al.Mercury concentrations in forest soils and stream waters in northeast and south China[J].Science of the Total Environment,2014,496:714-720.
[26] NAVRATIL T,SHANLEY J,ROHOVEC J,et al.Distribution and pools of mercury in czech forest soils[J].Water Air & Soil Pollution,2014,225(3):1829.
[27] OBRIST D,JOHNSON D W,LINDBERG S E,et al.Mercury distribution across 14 U.S.Forests.Part I:Spatial patterns of concentrations in biomass,litter,and soils[J].Environmental Science & Technology,2011,45(9):3974-3981.
[28] HUANG J,KANG S,WANG S,et al.Wet deposition of mercury at Lhasa,the capital city of Tibet[J].Science of the Total Environment,2013,447(1):123-132.
[29] HUANG J,KANG S,ZHANG Q,et al.Characterizations of wet mercury deposition on a remote high-elevation site in the southeastern Tibetan Plateau[J].Environmental Pollution,2015,206:518-526.
[30] HUANG J,KANG S,ZHANG Q,et al.Spatial distribution and magnification processes of mercury in snow from high-elevation glaciers in the Tibetan Plateau[J].Atmospheric Environment,2012,46(1):140-146.
[31] BLACKWELL B D,DRISCOLL C T.Deposition of mercury in forests along a montane elevation gradient[J].Environmental Science & Technology,2015,49(9):5363-70.
[32] GRIGAL D F.Inputs and outputs of mercury from terrestrial watersheds:A review[J].Environmental Reviews,2002,10(1):1-39.
[33] HUANG J,KANG S,ZHANG Q,et al.Wet deposition of mercury at a remote site in the Tibetan Plateau:Concentrations,speciation,and fluxes[J].Atmospheric Environment,2012,62(15):540-550.
[34] QIANGGONG ZHANG,JIE HUANG,FEIYUE WANG,et al.Mercury distribution and deposition in glacier snow over Western China[J].Environmental Science & Technology,2012,46(10):5404-5413.
[35] BLACKWELL B D,DRISCOLL C T.Using foliar and forest floor mercury concentrations to assess spatial patterns of mercury deposition[J].Environmental Pollution,2015,202:126-134.
[36] EAMUS D,MYERS B,DUFF G,et al.A cost-benefit analysis of leaves of eight Australian savanna tree species of differing leaf life-span[J].Photosynthetica 1999,36,(4),575-586.
[37] 仇广乐.贵州省典型汞矿地区汞的环境地球化学研究[D].贵阳:中国科学院研究生院(地球化学研究所),2005.QIU G L.Environmental geochemistry of mercury in typical mercury deposits in Guizhou Province[D].Guiyang:Graduate University of Chinese Academy of Sciences(Institute of Geochemistry),2005(in Chinese).
[38] 王之峰,汤丽玲,马生明,等.城市汞污染土壤中Hg的形态特征[J].物探与化探,2014,38(2):345-348.WANG Z F,TANG L L,MA S M,et al.Morphological characteristics of Hg in urban mercury contaminated soil [J].Geophysical and Geochemical Exploration.2014,38(2):345-348(in Chinese).
[39] WANG S,ZHANG L,LI G,et al.Mercury emission and speciation of coal-fired power plants in China[J].Atmospheric Chemistry and Physics,2010,10(3):1183-1192.
[40] YIN X,KANG S,FOY B D,et al.Multi-year monitoring of atmospheric total gaseous mercury at a remote high-altitude site (Nam Co,4730 m a.s.l.) in the inland Tibetan Plateau region[J].Atmospheric Chemistry & Physics,2018,18(14):1-44.
[41] ZHANG H,FU X,LIN C J,et al.Monsoon-facilitated characteristics and transport of atmospheric mercury at a high-altitude background site in southwestern China[J].Atmospheric Chemistry & Physics,2016,16(20):13131-13148.
[42] BING H,ZHOU J,WU Y,et al.Barrier effects of remote high mountain on atmospheric metal transport in the eastern Tibetan Plateau[J].Science of the Total Environment,2018,628-629:687-696.
[2] SHEU G R,MASON R P.An examination of methods for the measurements of reactive gaseous mercury in the atmosphere[J].Environmental Science & Technology,2001,35(6):1209-1216.
[3] FITZGERALD W F.Is Mercury increasing in the atmosphere?The Need for an atmospheric mercury Network (Amnet)[M]// Mercury as a Global Pollutant.Springer Netherlands,1995:245-254.
[4] LAMBORG C H,FITZGERALD W F,O′DONNELL J,et al.A non-steady-state compartmental model of global-scale mercury biogeochemistry with interhemispheric atmospheric gradients[J].Geochimica Et Cosmochimica Acta,2002,66(7):1105-1118.
[5] GONG P,WANG X P,XUE Y G,et al.Mercury distribution in the foliage and soil profiles of the Tibetan forest:Processes and implications for regional cycling[J].Environmental Pollution,2014,188(5):94-101.
[6] KANG S,HUANG J,WANG F,et al.Atmospheric mercury depositional chronology reconstructed from lake sediment and ice cores in the Himalayas and Tibetan Plateau[J].Environmental Science & Technology,2016,50(6):2859-2869.
[7] BISHOP K H,LEE Y H,MUNTHE J,et al.Xylem sap as a pathway for total mercury and methylmercury transport from soils to tree canopy in the boreal forest[J].Biogeochemistry,1998,40(2/3):101-113.
[8] COCKING D,ROHRER M,THOMAS R,et al.Effects of root morphology and Hg concentration in the soil on uptake by terrestrial vascular plants[J].Water Air & Soil Pollution,1995,80(1-4):1113-1116.
[9] SCHWESIG D,KREBS O.The role of ground vegetation in the uptake of mercury and methylmercury in a forest ecosystem[J].Plant & Soil,2003,253(2):445-455.
[10] RUDD J W,KELLY C A,HALL B D,et al.Importance of the forest canopy to fluxes of methyl mercury and total mercury to boreal ecosystems[J].Environmental Science & Technology,2001,35(15):3089-3098.
[11] XIAO Z,SOMMAR J,LINDQVIST O,et al.Atmospheric mercury deposition to grass in southern Sweden[J].Science of the Total Environment,1998,213(213):85-94.
[12] LEE Y H,BISHOP K H,MUNTHE J.Do concepts about catchment cycling of methylmercury and mercury in boreal catchments stand the test of time?Six years of atmospheric inputs and runoff export at Svartberget,northern Sweden[J].Science of the Total Environment,2000,260(1):11-20.
[13] MA M,WANG D,DU H,et al.Mercury dynamics and mass balance in a subtropical forest,southwestern China[J].Atmospheric Chemistry & Physics Discussions,2016,15(24):35857-35880.
[14] SLEMR F,ANGOT H,DOMMERGUE A,et al.Comparison of mercury concentrations measured at several sites in the Southern Hemisphere[J].Atmospheric Chemistry and Physics,2015,14(22):3125-3133.
[15] WANG Z,ZHANG X,XIAO J,et al.Mercury fluxes and pools in three subtropical forested catchments,southwest China[J].Environmental Pollution,2009,157(3):801-808.
[16] ZHOU J,FENG X,LIU H,et al.Examination of total mercury inputs by precipitation and litterfall in a remote upland forest of Southwestern China[J].Atmospheric Environment,2013,81(x):364-372.
[17] ZHOU J,WANG Z,ZHANG X,et al.Distribution and elevated soil pools of mercury in an acidic subtropical forest of southwestern China[J].Environmental Pollution,2015,202(7):187-195.
[18] CHOI H D,HOLSEN T M,HOPKE P K.Atmospheric mercury (Hg) in the Adirondacks:Concentrations and sources[J].Environmental Science & Technology,2008,42(15):5644-5653.
[19] DEMERS J D,DRISCOLL C T,FAHEY T J,et al.Mercury cycling in litter and soil in different forest types in the Adirondack region,New York,USA[J].Ecological Applications,2007,17(5):1341-1351.
[20] LARSSEN T,DE H W,WIKER M,et al.Mercury budget of a small forested boreal catchment in southeast Norway[J].Science of the Total Environment,2008,404(2):290-296.
[21] MASON R P,LAWSON N M,SHEU G R,et al.Annual and seasonal trends in mercury deposition in Maryland[J].Atmospheric Environment,2000,34(11):1691-1701.
[22] SCHWESIG D,MATZNER E.Pools and fluxes of mercury and methylmercury in two forested catchments in Germany[J].Science of the Total Environment,2000,260(1):213-223.
[23] TANG R,WANG H,LUO J,et al.Spatial distribution and temporal trends of mercury and arsenic in remote timberline coniferous forests,eastern of the Tibet Plateau,China[J].Environmental Science & Pollution Research,2015,22(15):11658-11668.
[24] FU X W,FENG X,DONG Z Q,et al.Atmospheric gaseous elemental mercury (GEM) concentrations and mercury depositions at a high-altitude mountain peak in south China[J].Atmospheric Chemistry and Physics,2010,10(5):2425-2437.
[25] LUO Y,DUAN L,WANG L,et al.Mercury concentrations in forest soils and stream waters in northeast and south China[J].Science of the Total Environment,2014,496:714-720.
[26] NAVRATIL T,SHANLEY J,ROHOVEC J,et al.Distribution and pools of mercury in czech forest soils[J].Water Air & Soil Pollution,2014,225(3):1829.
[27] OBRIST D,JOHNSON D W,LINDBERG S E,et al.Mercury distribution across 14 U.S.Forests.Part I:Spatial patterns of concentrations in biomass,litter,and soils[J].Environmental Science & Technology,2011,45(9):3974-3981.
[28] HUANG J,KANG S,WANG S,et al.Wet deposition of mercury at Lhasa,the capital city of Tibet[J].Science of the Total Environment,2013,447(1):123-132.
[29] HUANG J,KANG S,ZHANG Q,et al.Characterizations of wet mercury deposition on a remote high-elevation site in the southeastern Tibetan Plateau[J].Environmental Pollution,2015,206:518-526.
[30] HUANG J,KANG S,ZHANG Q,et al.Spatial distribution and magnification processes of mercury in snow from high-elevation glaciers in the Tibetan Plateau[J].Atmospheric Environment,2012,46(1):140-146.
[31] BLACKWELL B D,DRISCOLL C T.Deposition of mercury in forests along a montane elevation gradient[J].Environmental Science & Technology,2015,49(9):5363-70.
[32] GRIGAL D F.Inputs and outputs of mercury from terrestrial watersheds:A review[J].Environmental Reviews,2002,10(1):1-39.
[33] HUANG J,KANG S,ZHANG Q,et al.Wet deposition of mercury at a remote site in the Tibetan Plateau:Concentrations,speciation,and fluxes[J].Atmospheric Environment,2012,62(15):540-550.
[34] QIANGGONG ZHANG,JIE HUANG,FEIYUE WANG,et al.Mercury distribution and deposition in glacier snow over Western China[J].Environmental Science & Technology,2012,46(10):5404-5413.
[35] BLACKWELL B D,DRISCOLL C T.Using foliar and forest floor mercury concentrations to assess spatial patterns of mercury deposition[J].Environmental Pollution,2015,202:126-134.
[36] EAMUS D,MYERS B,DUFF G,et al.A cost-benefit analysis of leaves of eight Australian savanna tree species of differing leaf life-span[J].Photosynthetica 1999,36,(4),575-586.
[37] 仇广乐.贵州省典型汞矿地区汞的环境地球化学研究[D].贵阳:中国科学院研究生院(地球化学研究所),2005.QIU G L.Environmental geochemistry of mercury in typical mercury deposits in Guizhou Province[D].Guiyang:Graduate University of Chinese Academy of Sciences(Institute of Geochemistry),2005(in Chinese).
[38] 王之峰,汤丽玲,马生明,等.城市汞污染土壤中Hg的形态特征[J].物探与化探,2014,38(2):345-348.WANG Z F,TANG L L,MA S M,et al.Morphological characteristics of Hg in urban mercury contaminated soil [J].Geophysical and Geochemical Exploration.2014,38(2):345-348(in Chinese).
[39] WANG S,ZHANG L,LI G,et al.Mercury emission and speciation of coal-fired power plants in China[J].Atmospheric Chemistry and Physics,2010,10(3):1183-1192.
[40] YIN X,KANG S,FOY B D,et al.Multi-year monitoring of atmospheric total gaseous mercury at a remote high-altitude site (Nam Co,4730 m a.s.l.) in the inland Tibetan Plateau region[J].Atmospheric Chemistry & Physics,2018,18(14):1-44.
[41] ZHANG H,FU X,LIN C J,et al.Monsoon-facilitated characteristics and transport of atmospheric mercury at a high-altitude background site in southwestern China[J].Atmospheric Chemistry & Physics,2016,16(20):13131-13148.
[42] BING H,ZHOU J,WU Y,et al.Barrier effects of remote high mountain on atmospheric metal transport in the eastern Tibetan Plateau[J].Science of the Total Environment,2018,628-629:687-696.