Response of lead cycling in the surface Sargasso Sea to changes in tropospheric input
Response of lead cycling in the surface Sargasso Sea to changes in tropospheric input
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马尾藻海表层铅循环对对流层输入变化的响应
DOI：
10.1029/93jc01639
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发表时间：
1993
影响因子：
--
通讯作者：
Y. Erel
中科院分区：
文献类型：
--
作者：
A. Véron;T. Church;A. Flegal;C. Patterson;Y. Erel
对1989年4月和11月在百慕大大西洋时间序列站（美国联合全球海洋通量研究）收集的地表水样本（0-600米）和捕获粒子中的铅及其稳定同位素进行了分析。这些结果与1988年8月以来在百慕大连续收集的降水测定的湿大气铅沉降进行了比较，该降水是大气-海洋化学实验计划的一部分。尽管预期存在季节性变化，但自1979年以来，由于对流层沉积相应减少了5至8倍，地表水中的铅浓度明显下降了30%至40%。这一结果与1989年剖面前500 m的206Pb/207Pb比值（1.18-1.20）明显低于1984年剖面（1.20-1.21）的稳定铅同位素测量结果相印证。这种同位素变化反映了美国铅矿石供应的变化，以及欧洲非洲对西北大西洋铅投入的贡献相对增加，这可能是由于北美汽油消费铅排放减少所致。这种对对流层输入地表水的年际变化的快速响应与其有效的生物反应性有关，1989年4月在150米部署的沉积物捕集器就证明了这一点。沉积物捕集器的结果表明，在浮游生物活跃的时期，铅迅速渗透到前200米，并伴有大颗粒。回顾1988-1989年在百慕大收集的三维等熵气团轨迹和降水事件表明，每年30%至40%的铅沉降来自贸易偏东的气象体制。1989年4月和11月在地表水（0-100米）观测到的铅同位素信号清楚地证明了这一投入。我们发现，在季节混合层（0-50 m）中积累的铅反映了这种大气输入。考虑该混合层测得的同位素信号（1.178±0.001），以及温带西风和贸易东风对马尾藻海大气铅沉积的贡献，我们计算出欧亚地区的同位素特征为1.155（±0.004）。根据这些结果，我们计算出马尾藻海地表水实际206Pb/207Pb平均比值为1.188（±0.004）。
Lead and its stable isotopes have been analyzed in surface water samples (0–600 m) and trapped particles collected at the Bermuda Atlantic Time Series Station (U.S. Joint Global Ocean Flux Study) in April and November 1989. These results are compared with wet atmospheric lead deposition as determined from precipitation continuously collected in Bermuda since August 1988 as pan of the Atmosphere-Ocean Chemistry Experiment program. Despite an expected seasonal variability, lead concentrations in surface waters have clearly decreased by 30 to 40% since 1979 in response to a corresponding decline by a factor of 5 to 8 of the tropospheric deposition. This result is corroborated by stable lead isotope measurements with 206Pb/207Pb ratios which are significantly less radiogenic (1.18–1.20) in the first 500 m of the 1989 profile than those measured in 1984 (1.20–1.21). This isotopic shift reflects changes of lead ore supply in the United States as well as a relative increase of the Eurafrican contribution to lead input in the northwest Atlantic that is likely due to the reduction of lead emissions from gasoline consumption in North America. This fast response of lead to interannual variations of the tropospheric input into surface waters is related to its efficient bioreactivity, as demonstrated with a sediment trap deployed at 150 m in April 1989. Sediment trap results show the rapid penetration of lead into the first 200 m associated with large particles during a period of high plankton activity. Retrospective isentropic air mass trajectories in three dimensions coupled with the precipitation events collected in Bermuda in 1988–1989 show that 30 to 40% of the annual lead deposition originates from the trade easterly meteorological regime. This input is clearly evidenced with lead isotopic signals observed in surface waters (0–100 m) in April and November 1989. We show that lead accumulated in the seasonal mixed layer (0–50 m) reflects this atmospheric input. Taking into account the isotopic signal measured in this mixed layer (1.178±0.001) as well as the respective contribution of the temperate westerlies and trade easterlies to atmospheric lead deposition to the Sargasso Sea, we calculate that the isotopic signature from the Eurafrican regions is 1.155 (±0.004). Based on these results, we calculate that the actual 206Pb/207Pb average ratio in surface waters of the Sargasso Sea is 1.188 (±0.004).