Mercury （Hg） is an environmental pollutant, and can bioaccumulate and biomagnify in the food web. Twenty four fish samples of different tropic level i.e., Herbivore, Omnivore and Carnivore were collected from two co...Mercury （Hg） is an environmental pollutant, and can bioaccumulate and biomagnify in the food web. Twenty four fish samples of different tropic level i.e., Herbivore, Omnivore and Carnivore were collected from two contaminated rivers, the Megna and the Buriganga which surround the Dhaka division for the assessment of toxic Hg. Fourteen samples were found to contain Hg in the range of 0.01-0.09 mg/kg. The highest Hg （0.09 mg/kg） was found in the Carnivore, Bele （Glossogobius giuris）. However, all fish species had lower amount of Hg than the maximum Hg limit （0.5 mg/kg for fish） set by World Health Organization （WHO）. Among all the fish species, the order of bioaccumulation was carnivore 〉 omnivore 〉 herbivore. Kajoli （Ailia coila）, Shing （Heteropnuestes fossilis）, Rui （Labeo rohita）, Chewa （Tryauchen vagine）, Rita （Rita rita）, Hilsha （Tenualosa ilisha）, Small Puti （Puntius sophore）, Bacha （Eutropiichthys vacha） and Chingri （smallprawn） were not found to contain any Hg which indicated that fish species from these rivers are safe for human consumption.展开更多
Huntsman Lake is located within the Middle Run of the Pohick Creek watershed, which is itself located within the much larger Chesapeake Bay watershed. Data collected from both the water column and the lake＇s sediment...Huntsman Lake is located within the Middle Run of the Pohick Creek watershed, which is itself located within the much larger Chesapeake Bay watershed. Data collected from both the water column and the lake＇s sediments indicate that phosphorus-rich bottom sediments are an important internal loading source, and these internal phosphorus loads would continue to adversely impact water quality until and unless sediments are removed or inactivated. The implementation of artificial circulation was anticipated to be able to increase the sequestration of phosphorus within better oxygenated bottom sediments, and was the first lake management strategy deployed in Huntsman Lake. In the first two years after the installation of a whole-lake circulation system, the lake＇s waters are no longer stratified, and the bottom waters are no longer hypoxic and/or anoxic. While there is no evidence of a subsequent reduction in concentrations of nitrogen or chlorophyll-a, average phosphorus concentrations have decreased. However, high variability in the phosphorus data decreases our confidence that this is a sustained improvement. These results are consistent with prior findings, including those from downstream systems, that the reversal of the symptoms of eutrophication can involve lag-periods up to several years, if they are successful at all.展开更多
文摘Mercury （Hg） is an environmental pollutant, and can bioaccumulate and biomagnify in the food web. Twenty four fish samples of different tropic level i.e., Herbivore, Omnivore and Carnivore were collected from two contaminated rivers, the Megna and the Buriganga which surround the Dhaka division for the assessment of toxic Hg. Fourteen samples were found to contain Hg in the range of 0.01-0.09 mg/kg. The highest Hg （0.09 mg/kg） was found in the Carnivore, Bele （Glossogobius giuris）. However, all fish species had lower amount of Hg than the maximum Hg limit （0.5 mg/kg for fish） set by World Health Organization （WHO）. Among all the fish species, the order of bioaccumulation was carnivore 〉 omnivore 〉 herbivore. Kajoli （Ailia coila）, Shing （Heteropnuestes fossilis）, Rui （Labeo rohita）, Chewa （Tryauchen vagine）, Rita （Rita rita）, Hilsha （Tenualosa ilisha）, Small Puti （Puntius sophore）, Bacha （Eutropiichthys vacha） and Chingri （smallprawn） were not found to contain any Hg which indicated that fish species from these rivers are safe for human consumption.
文摘Huntsman Lake is located within the Middle Run of the Pohick Creek watershed, which is itself located within the much larger Chesapeake Bay watershed. Data collected from both the water column and the lake＇s sediments indicate that phosphorus-rich bottom sediments are an important internal loading source, and these internal phosphorus loads would continue to adversely impact water quality until and unless sediments are removed or inactivated. The implementation of artificial circulation was anticipated to be able to increase the sequestration of phosphorus within better oxygenated bottom sediments, and was the first lake management strategy deployed in Huntsman Lake. In the first two years after the installation of a whole-lake circulation system, the lake＇s waters are no longer stratified, and the bottom waters are no longer hypoxic and/or anoxic. While there is no evidence of a subsequent reduction in concentrations of nitrogen or chlorophyll-a, average phosphorus concentrations have decreased. However, high variability in the phosphorus data decreases our confidence that this is a sustained improvement. These results are consistent with prior findings, including those from downstream systems, that the reversal of the symptoms of eutrophication can involve lag-periods up to several years, if they are successful at all.
