Mercury methylation along a lake-forest transect in the Tapajos river floodplain, Brazilian Amazon: seasonal and vertical variations
Mercury methylation along a lake-forest transect in the Tapajos river floodplain, Brazilian Amazon: seasonal and vertical variations
复制标题
DOI：
10.1016/s0048-9697(00)00627-6
复制
发表时间：
2000-10-16
影响因子：
9.8
通讯作者：
Mergler, D
中科院分区：
文献类型：
--
作者：
Guimaraes, JRD;Roulet, M;Mergler, D
通过对塔帕霍斯河Enseada Grande湖森林样带不同深度和不同位置的Hg-203测定，评价了沉积物、土壤和其他地点甲基汞净生产量的季节和空间变化。土壤和沉积物样本是在地表和不同深度采集的，最深可达9厘米。新鲜样品和酸化对照(1-3克干重)在25-28摄氏度的黑暗中培养3天，0.5-1.6微克汞(-1)(干重)。添加为(HgCl2)-Hg-203。CH3-Hg-203经酸浸后在闪烁鸡尾酒中提取并测定。甲基汞的生产量在不同地点、不同沉积物或土层之间有数量级的差异。季节变化小于采样深度和位置的变化。在两个季节，沉积物和土壤或淹水土壤中的甲基汞生成量随着深度的增加而减少，在表层，富碳滨海植物带(2.3-8.9%)和淹水森林(3.2-4.5%)的甲基汞生成量比湖心(0.2-0.56%)高一个数量级。在泥泞的干燥土壤(旱季)和已经被淹了几个月的土壤中也发现了类似的甲基汞生产。在大型植物带土壤中(旱季)，甲基化主要与稀薄的雀麦属植物有关。Rootlet层。在森林立地，土壤甲基化的垂直变化在淹水土壤中没有干旱土壤明显，在淹水过程中，沉积在枯枝落叶层上的絮状沉积物甲基化速率较高。漂浮雀形藻的根。是一个重要的汞甲基化位点，特别是那些大量定植围植生物的地方(3.4-5.4%)。表层或近底层水中的甲基化在所有地点都检测不到(<；3x10(-2)%)。洪水泛滥的森林和大型植物垫子是亚马逊的具体特征，是来自自然和人造来源的汞输入与当地人口通过鱼类摄取而暴露于甲基汞之间的重要联系。(C)2000 Elsevier Science B.V.保留所有权利。
The seasonal and spatial variations of net methylmercury production in sediments, soils and other sites were evaluated by assays with Hg-203 at different depths and locations along a lake-forest transect at lake Enseada Grande, Tapajos river. Soil and sediment samples were taken at the surface and at different depths up to 9 cm. Fresh samples and acidified controls (1-3 g dry wt.) were slurried with local water and incubated in the dark at 25-28 degrees C for 3 days with 0.5-1.6 mu g Hg g(-1) (dry wt.) added as (HgCl2)-Hg-203. CH3 Hg-203 was extracted and measured in scintillation cocktail after acid leaching. Methylmercury production varied by orders of magnitude among sites and among sediment or soil layers. Seasonal variations were smaller than those with sample depth and location. In both seasons, MeHg formation in sediment and soil or flooded soil decreased with depth and was, in the top layers, one order of magnitude higher in the C-rich littoral macrophyte zone (2.3-8.9%) and flooded forest (3.2-4.5%) than in the center of the lake (0.2-0.56%). Similar MeHg production was found in slurried dry soils (dry season) and in soils already flooded for months. In the macrophyte zone soil (dry season), methylation was mainly associated with the thin Paspalum sp. rootlet layer. In the forest site, vertical variation in methylation was less pronounced in flooded than in dry soils and during the inundation the higher methylation rate was found in the flocculent sediment settled over the litter layer. The roots of floating Paspalum sp. were an important Hg methylation site, particularly those heavily colonized with periphyton (3.4-5.4%). Methylation in surface or near-bottom water was undetectable (< 3 x 10(-2)%) at all sites. Flooded forests and macrophyte mats are specific features of the Amazon and are important links between Hg inputs from natural and manmade sources and MeHg exposure of local populations through fish intake. (C) 2000 Elsevier Science B.V. All rights reserved.