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Dedication 总被引:1,自引:0,他引:1
Elevated concentrations of arsenic (As) occurred during warm months in water from the outlet of Lake Mohawk in northwestern
New Jersey. The shallow manmade lake is surrounded by residential development and used for recreation. Eutrophic conditions
are addressed by alum and copper sulfate applications and aerators operating in the summer. In September 2005, arsenite was
dominant in hypoxic to anoxic bottom water. Filterable As concentrations were about 1.6–2 times higher than those in the upper
water column (23–25 μg/L, mostly arsenate). Hypoxic/anoxic and near-neutral bottom conditions formed during the summer, but
became more oxic and alkaline as winter approached. Acid-leachable As concentrations in lake-bed sediments ranged up to 694 mg/kg
in highly organic material from the tops of sediment cores but were <15 mg/kg in geologic substrate. During warm months, reduced
As from the sediment diffuses into the water column and is oxidized; mixing by aerators, wind, and boat traffic spreads arsenate
and metals, some in particulate form, throughout the water column. Similar levels of As in sediments of lakes treated with
arsenic pesticides indicate that most of the As in Lake Mohawk probably derives from past use of arsenical pesticides, although
records of applications are lacking. The annual loss of As at the lake outlet is only about 0.01% of the As calculated to
be in the sediments, indicating that elevated levels of As in the lake will persist for decades. 相似文献
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