Global Biogeochemical Implications of Mercury Discharges from Rivers and Sediment Burial
Global Biogeochemical Implications of Mercury Discharges from Rivers and Sediment Burial
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DOI：
10.1021/es502134t
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发表时间：
2014-08-19
影响因子：
11.4
通讯作者：
Sunderland, Elsie M.
中科院分区：
文献类型：
--
作者：
Amos, Helen M.;Jacob, Daniel J.;Sunderland, Elsie M.
河流是海洋生态系统汞的重要来源。根据对汇编观测数据的分析，我们估计全球目前从河流到海洋边缘的汞排放量为27 +/- 13 Mmol a（-1）（5500 +/- 2700 Mg a（-1）），其中28%到达公海，其余沉积到海洋边缘沉积物中。在全球范围内，从河流进入公海的汞占大气输入量的30%。这比以前估计的要大，因为考虑到亚洲河流中的浓度升高以及不同类型河口的近海运输的变化。自20世纪70年代以来，流入北大西洋的河流汞减少了几倍，而流入北太平洋的汞却增加了。这些趋势对海洋边缘的汞浓度有很大影响，但在公海中影响太小，无法解释观测到的北大西洋海水浓度下降或北太平洋海水浓度上升的现象。海洋边缘沉积物中汞的埋藏是全球汞地球化学循环中的一个主要汇，这是以前没有考虑过的。我们发现，包括这个汇在一个完全耦合的全球生物地球化学箱模型有助于平衡大量的人为释放的汞从商业产品最近添加到全球库存。这也意味着，可以在更短的时间内（几百年而不是几千年）从活跃的环境循环中清除遗留的人为汞。自然环境中的汞含量低于先前的估计，这意味着人类活动的影响相对较大。
Rivers are an important source of mercury (Hg) to marine ecosystems. Based on an analysis of compiled observations, we estimate global present-day Hg discharges from rivers to ocean margins are 27 +/- 13 Mmol a(-1) (5500 +/- 2700 Mg a(-1)), of which 28% reaches the open ocean and the rest is deposited to ocean margin sediments. Globally, the source of Hg to the open ocean from rivers amounts to 30% of atmospheric inputs. This is larger than previously estimated due to accounting for elevated concentrations in Asian rivers and variability in offshore transport across different types of estuaries. Riverine inputs of Hg to the North Atlantic have decreased several-fold since the 1970s while inputs to the North Pacific have increased. These trends have large effects on Hg concentrations at ocean margins but are too small in the open ocean to explain observed declines of seawater concentrations in the North Atlantic or increases in the North Pacific. Burial of Hg in ocean margin sediments represents a major sink in the global Hg biogeochemical cycle that has not been previously considered. We find that including this sink in a fully coupled global biogeochemical box model helps to balance the large anthropogenic release of Hg from commercial products recently added to global inventories. It also implies that legacy anthropogenic Hg can be removed from active environmental cycling on a faster time scale (centuries instead of millennia). Natural environmental Hg levels are lower than previously estimated, implying a relatively larger impact from human activity.