A review of global environmental mercury processes in response to human and natural perturbations: Changes of emissions, climate, and land use.
A review of global environmental mercury processes in response to human and natural perturbations: Changes of emissions, climate, and land use.
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DOI：
10.1007/s13280-017-1004-9
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发表时间：
2018-03
期刊：
影响因子：
6.5
通讯作者：
Selin NE
中科院分区：
文献类型：
--
作者：
Obrist D;Kirk JL;Zhang L;Sunderland EM;Jiskra M;Selin NE
我们回顾了最近的进展，我们的全球汞（Hg）的循环，包括最佳估计的汞浓度和池的大小在主要的环境隔间和交换过程中，这些水库之间。最近取得的进展包括：提供了新的全球数据集，涵盖了世界上以前缺乏环境汞数据的地区;将这些数据纳入全球和区域模型，不断改善对全球汞循环的估计。新的分析技术，如汞稳定同位素表征，提供了新的来源和转化过程的限制。全球受人类活动影响的主要汞储存库包括大气（4.4 - 5.3 Gt）、陆地环境（特别是土壤：250 - 1000 Gg）和水生生态系统（例如，海洋：270 - 450千兆克）。1990年至2010年间，人类活动造成的汞排放量下降，导致欧洲和美国大气中的Hg0浓度和HgII湿沉降量下降（每年下降-1.5%至-2.2%）。据报告，北方高纬度地区大气中的汞含量下降幅度较小（每年-0.2%），但南半球没有，而东亚大气中的汞含量仍在增加。新的观察和更新的模型现在表明，热带和亚热带自由对流层中存在高浓度的氧化HgII，深对流可以清除这些HgII库。因此，据预测，全球湿汞沉积总量的50%将发生在热带海洋。海洋汞逃逸是当今大气汞的一大来源（约2900毫克/年;范围1900 - 4200毫克/年）。增强的海水Hg0水平表明增强的Hg0海洋逃避热带辐合带，这可能与高HgII沉积。长期以来，陆地被认为是汞的重要来源，对陆地向大气排放气态汞的估计值已向下修正，由于植物大量吸收汞，大多数陆地环境现在被认为是大气汞的净汇。据估计，全球每年植物的凋落物沉积量为1，020 - 1，230毫克。稳定同位素分析和直接通量测量提供的证据表明，在许多生态系统中，通过植物输入的Hg 0沉积占主导地位，占土壤中Hg的57 - 94%。在全球水生汞排放中，估计约50%发生在中国和印度，这两个国家的汞流入西太平洋和北印度洋。第一份全球淡水汞清单表明，内陆淡水汞排放主要来自手工和小规模采金业（手工和小规模采金业;约880毫克/年）、工业和废水排放（220毫克/年）以及陆地迁移（170 - 300毫克/年）。在远洋区域，汞的主要来源是大气沉积;北冰洋是个例外，河流和海岸侵蚀可能是主要来源。北大西洋海水中的汞浓度在过去几十年中似乎有所下降，但自1980年代中期以来，由于亚洲大陆大气沉降的增加，太平洋海水中的汞浓度有所上升。最后，我们提供的例子，由于排放，气候和土地利用的变化，汞循环正在进行和预期的变化。预计未来排放量的变化将在很大程度上取决于小规模手工开采金矿，以及《水俣公约》规定的能源使用情景和技术要求。我们预测，土地利用和气候变化对汞循环的影响将是巨大的，并与生态系统功能和全球大气及海洋环流的变化有着内在的联系。我们预测未来汞的全球循环和人类接触的多重和同时变化的能力正在迅速发展，但需要进一步加强。
We review recent progress in our understanding of the global cycling of mercury (Hg), including best estimates of Hg concentrations and pool sizes in major environmental compartments and exchange processes within and between these reservoirs. Recent advances include the availability of new global datasets covering areas of the world where environmental Hg data were previously lacking; integration of these data into global and regional models is continually improving estimates of global Hg cycling. New analytical techniques, such as Hg stable isotope characterization, provide novel constraints of sources and transformation processes. The major global Hg reservoirs that are, and continue to be, affected by anthropogenic activities include the atmosphere (4.4–5.3 Gt), terrestrial environments (particularly soils: 250–1000 Gg), and aquatic ecosystems (e.g., oceans: 270–450 Gg). Declines in anthropogenic Hg emissions between 1990 and 2010 have led to declines in atmospheric Hg0 concentrations and HgII wet deposition in Europe and the US (− 1.5 to − 2.2% per year). Smaller atmospheric Hg0 declines (− 0.2% per year) have been reported in high northern latitudes, but not in the southern hemisphere, while increasing atmospheric Hg loads are still reported in East Asia. New observations and updated models now suggest high concentrations of oxidized HgII in the tropical and subtropical free troposphere where deep convection can scavenge these HgII reservoirs. As a result, up to 50% of total global wet HgII deposition has been predicted to occur to tropical oceans. Ocean Hg0 evasion is a large source of present-day atmospheric Hg (approximately 2900 Mg/year; range 1900–4200 Mg/year). Enhanced seawater Hg0 levels suggest enhanced Hg0 ocean evasion in the intertropical convergence zone, which may be linked to high HgII deposition. Estimates of gaseous Hg0 emissions to the atmosphere over land, long considered a critical Hg source, have been revised downward, and most terrestrial environments now are considered net sinks of atmospheric Hg due to substantial Hg uptake by plants. Litterfall deposition by plants is now estimated at 1020–1230 Mg/year globally. Stable isotope analysis and direct flux measurements provide evidence that in many ecosystems Hg0 deposition via plant inputs dominates, accounting for 57–94% of Hg in soils. Of global aquatic Hg releases, around 50% are estimated to occur in China and India, where Hg drains into the West Pacific and North Indian Oceans. A first inventory of global freshwater Hg suggests that inland freshwater Hg releases may be dominated by artisanal and small-scale gold mining (ASGM; approximately 880 Mg/year), industrial and wastewater releases (220 Mg/year), and terrestrial mobilization (170–300 Mg/year). For pelagic ocean regions, the dominant source of Hg is atmospheric deposition; an exception is the Arctic Ocean, where riverine and coastal erosion is likely the dominant source. Ocean water Hg concentrations in the North Atlantic appear to have declined during the last several decades but have increased since the mid-1980s in the Pacific due to enhanced atmospheric deposition from the Asian continent. Finally, we provide examples of ongoing and anticipated changes in Hg cycling due to emission, climate, and land use changes. It is anticipated that future emissions changes will be strongly dependent on ASGM, as well as energy use scenarios and technology requirements implemented under the Minamata Convention. We predict that land use and climate change impacts on Hg cycling will be large and inherently linked to changes in ecosystem function and global atmospheric and ocean circulations. Our ability to predict multiple and simultaneous changes in future Hg global cycling and human exposure is rapidly developing but requires further enhancement.
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