Total mercury levels in nine species of freshwater fish from two hydroelectric reservoirs and a crater lake in Ghana

Total mercury (Hg) concentrations were determined in the muscle tissue of fish from three reservoirs in Ghana, namely, Lake Bosomtwi, Kpong and Akosombo Hydroelectric Reservoirs. A total of 165 fish samples covering nine species were collected and analysed for total mercury. A mixture of HNO3, H2SO4 and HClO4 were used for complete oxidation of organic tissues. Hg was detected by the Cold Vapour Atomic Absorption Spectrometry technique using an automatic mercury analyzer. Total mercury concentrations in microg g(-1) (wet weight) ranged from below 0.001 to 0.070 for fish from Lake Bosomtwi, 0.010 to 0.275 for fish from Kpong Reservoir and from below 0.001 to 0.042 for fish from Akosombo Reservoir. All the results obtained are below the World Health Organization limit of 0.5 microg g(-1). The low levels of total mercury obtained in this study suggest that the three aquatic environments have not been significantly impacted by mercury contamination.     

Total Mercury Distribution in Different Tissues of Frigate Tuna (Auxis thazard thazard) from the Atlantic Coastal Waters of Ghana, Gulf of Guinea

Total mercury concentrations in different tissues of frigate tuna fish (Auxis thazard thazard) was determined by the cold vapour atomic absorption spectrometry technique using an automatic mercury analyzer. A mixture of HNO₃, HClO₄ and H₂SO₄ was used for complete oxidation of organic tissue. The concentration of mercury obtained was in the order Gills < Stomach < Gonads < Intestine < Heart < Duodenum < Liver < Muscle. The concentration of total mercury detected in the edible muscle tissue of the tuna fish tested ranged from 0.044 to 0.201 μg g⁻¹ (mean = 0.108 μg g⁻¹) wet weight. These levels are all within the maximum allowed/recommended level in fish (0.5 μg g⁻¹ wet weight) set by the Food and Agriculture Organisation/World Health Organisation (FAO/WHO) and are therefore unlikely to constitute any significant mercury exposure to the general population because of consumption of tuna fish. The results of the study suggest a relatively clean marine environment that has not been significantly impacted by mercury contamination probably due to minimal industrial activity in the region.     

Total mercury distribution in different tissues of six species of freshwater fish from the Kpong hydroelectric reservoir in Ghana

Total mercury concentrations were determined in seven tissues of 38 fish samples comprising six species from the Kpong hydroelectric reservoir in Ghana by cold vapour atomic absorption spectrometry technique using an automatic mercury analyzer. Mercury concentration in all the tissues ranged from 0.005 to 0.022 μg/g wet weight. In general, the concentration of mercury in all the tissues were decreasing in the order; liver > muscle > intestine > stomach > gonad > gill > swim bladder. Mercury concentration was generally greater in the tissues of high-trophic-level fish such as Clarotes laticeps, Mormyrops anguilloides and Chrysichthys aurutus whereas low-trophic-level fish such as Oreochromis niloticus recorded low mercury concentration in their tissues. The results obtained for total mercury concentration in the muscle tissues analysed in this study are below the WHO/FAO threshold limit of 0.5 μg/g. This suggests that the exposure of the general public to Hg through fish consumption can be considered negligible.     

中国煤中氟的含量及其分布

在全国主要产煤的26个省、市和自治区根据各煤田的地质储量、成煤时期和煤变质程度,兼顾各矿区的煤炭产量,采集305个煤样,用高温热水解-离子选择性电极法测定了全部样品的氟含量.煤中的氟主要以无机形态赋存,氟含量和变质程度之间没有必然的联系.成煤时代等单一因素对氟含量的影响可能为其它各种因素的综合作用所掩盖,对此有必要进行更深入、具体的研究研究了各省、市和自治区的煤氟含量的分布,有必要重新审视、甄别燃煤型氟中毒区氟的来源.全国煤的氟含量服从对数正态分布,90%的样品含氟范围为47～347mg/kg,宜用几何平均值136mg/kg作为全国平均煤氟含量.与世界煤相比,中国煤氟含量并无异常.