Department of Agronomy, Federal Rural University of Pernambuco, Dom Manuel de Medeiros Street, S/n - Dois Irmãos, 52171-900, Recife, PE, Brazil.
Ecotoxicol Environ Saf. 2019 Nov 15;183:109469. doi: 10.1016/j.ecoenv.2019.109469. Epub 2019 Jul 31.
Botafogo river estuary poses the highest Hg concentration reported for mangrove soils in Brazil. Such high contamination took place owing to the improper waste disposal for 24 years from a chlor-alkali plant nearby the estuary. Here we determined Hg concentrations in soils, mangrove plants (Rhizophora mangle and Laguncularia racemosa), and an aquatic organism (the oyster species Crassostrea rhizophorae) to assess Hg bioavailability. Besides, a sequential extraction procedure was used to separate soil Hg into five fractions: water-soluble; 'human stomach acid' soluble; organically bound; elemental Hg; mercuric sulfide. Results showed that environmentally available concentration of Hg in the mangrove soils were up to 150-fold higher than a pristine mangrove under the same geological context used as a reference. Additionally, Hg concentration in soils was also above sediment quality guidelines and Hg adverse effects towards sensitive estuarine organisms are likely. Mercury concentrations in oysters were the highest reported in Brazil, but within safety standards according to the country food security agency. It seems that Hg stocks in the studied soils are governed by organic matter and redox conditions, but changing on environmental conditions and land use can alter this balance and convert these mangrove areas from sink to source of Hg to the environment.
博塔福戈河口的土壤汞浓度是巴西红树林土壤中报道的最高值。这种高污染是由于河口附近的氯碱厂 24 年来的废物处理不当造成的。在这里，我们测定了土壤、红树林植物（红树和卤蕨）和水生生物（牡蛎物种珠母贝）中的汞浓度，以评估汞的生物利用度。此外，还采用了连续提取程序将土壤中的汞分为五部分：水溶性；“人胃酸”溶性；有机结合；元素汞；硫化汞。结果表明，在与作为参照的同一地质背景下的原始红树林相比，红树林土壤中环境可利用的汞浓度高达 150 倍。此外，土壤中的汞浓度也高于沉积物质量指南，汞对敏感的河口生物可能产生不利影响。牡蛎中的汞浓度是巴西报道的最高值，但根据该国食品安全机构的标准，仍在安全范围内。看来，研究土壤中的汞储量受有机质和氧化还原条件的控制，但环境条件和土地利用的变化可能会改变这种平衡，使这些红树林地区从汞的汇转变为环境的汞源。
