Maia Poliana Dutra, Maurice Laurence, Tessier Emmanuel, Amouroux David, Cossa Daniel, Pérez Marcela, Moreira-Turcq Patricia, Rhéault Isabelle
Université de Toulouse, UPS (SVT-OMP), LMTG, 14 Avenue Edouard Belin, Toulouse, France.
Sci Total Environ. 2009 Nov 15;407(23):6073-84. doi: 10.1016/j.scitotenv.2009.08.015. Epub 2009 Sep 11.
This work presents the distribution and the partition of mercury (Hg) in the Curuai floodplain lakes along the Amazon River. The maximum Total Filtered Hg (T-FHg) concentrations in the floodplain lakes (28 to 52 pmol L(-1)) coincide with the maximum T-FHg concentrations of the Amazon River and are measured during the flooding period. The lowest T-FHg values (3 to 5 pmol L(-1)) are observed during the flood peak of the mainstream, during the rainy season, when waters are diluted by the local rainfall. In this system, Hg is mainly transported in the particulate phase, confirmed by elevated values of the Hg partition coefficient (4.77<K(d) (Hg)<5.83 Lkg(-1)). The highest Total Particulate Hg (T-PHg) concentrations (47-478 pmol L(-1)) in the lakes are measured during the dry season when they are isolated from the mainstream. This enrichment is due to the elevated TSS content associated to the re-suspension of the bottom sediments by the wind action and the bioturbation in shallow water lakes. In the flooded system, the lakes show different geochemical characteristics that control the Hg distribution and partition. In the white water (WW) lakes, characterized by oxidative neutral waters and highest TSS contents (till 2041 mg L(-1)), the T-PHg is associated to the particulate organic matter mainly during the dry season, while the T-FHg and T-FMn concentrations are correlated. In the black water (BW) lakes that show reductive pH conditions and lowest TSS load (2 to 5 2 mg L(-1)), P-iron and T-PHg display a positive relationship whereas the redox conditions favor the desorption of Hg from the particulate to the filtered phase. The mercury mass budget estimated in this study confirms that the Curuai floodplain system acts as a particulate mercury trap, with a net storage of particulate Hg of 150 kg PHg year(-1).
这项研究展示了亚马逊河沿岸库鲁艾河漫滩湖泊中汞（Hg）的分布与分配情况。河漫滩湖泊中总过滤汞（T - FHg）的最高浓度（28至52皮摩尔/升）与亚马逊河的最高T - FHg浓度一致，且在洪水期测得。最低的T - FHg值（3至5皮摩尔/升）出现在主流洪水高峰期，即雨季，此时河水被当地降雨稀释。在该系统中，汞主要以颗粒态形式传输，汞分配系数的升高值（4.77 < K(d)(Hg) < 5.83升/千克）证实了这一点。湖泊中总颗粒汞（T - PHg）的最高浓度（47 - 478皮摩尔/升）在旱季测得，此时湖泊与主流隔绝。这种富集是由于风蚀作用使底部沉积物再悬浮以及浅水湖泊中的生物扰动导致总悬浮物（TSS）含量升高所致。在洪水淹没的系统中，湖泊呈现出不同的地球化学特征，这些特征控制着汞的分布与分配。在以氧化性中性水体和最高TSS含量（高达2041毫克/升）为特征的白水（WW）湖中，T - PHg主要在旱季与颗粒有机物相关联，而T - FHg和T - FMn浓度相互关联。在呈现还原pH条件且TSS负荷最低（2至52毫克/升）的黑水（BW）湖中，颗粒态铁（P - iron）与T - PHg呈现正相关关系，而氧化还原条件有利于汞从颗粒态解吸至过滤态。本研究估算的汞质量收支证实，库鲁艾河漫滩系统起到了颗粒汞阱的作用，颗粒汞的净储存量为每年150千克PHg。
