No abstract

Surface water samples for arsenic (As) concentration and speciation analysis were collected from organic matter-rich blackwaters of the Lake Drummond portion of the Great Dismal Swamp in southeastern Virginia, USA. Arsenic concentrations and speciation were determined by selective hydride generation, gas chromatography with photoionization detection. Surface waters from the Great Dismal Swamp are high in dissolved organic carbon (DOC) concentrations (445-9,600 lmol/kg) and of low pH (4.2-6.4). Total dissolved As concentrations [i.e., As(III) + As(V)], hereafter As T , range from 2.2 nmol/kg to 21.4 nmol/kg. Arsenite, As(III), concentrations range from *1 nmol/kg to 17.7 nmol/kg, and As(V) ranges from *1 nmol/kg to 14.1 nmol/kg. Arsenate, As(V), is the predominant form of dissolved As in the inflow waters to the Great Dismal Swamp, whereas within the swamp proper arsenite, As(III), dominates. Arsenite accounts for 8-37% of As T in inflow waters west of the Suffolk Scarp, and between 54% and 81% of As T in Lake Drummond and Great Dismal Swamp waters east of the scarp. Arsenite is strongly correlated to DOC (r = 0.94) and inversely related to pH (r = -0.9), both at greater than the 99% confidence level. Arsenate is weakly related to pH and DOC (r = 0.4 and -0.37, respectively), and neither relationship is statistically significant. No statistical relationships exist between As(V) or As(III) and PO 4 concentrations. The predominance of As(III) and its strong correlation with DOC in Great Dismal Swamp waters suggest that DOC may inhibit As(III) adsorption or form stable aqueous complexes with As(III) in these waters. Alternatively, phytoplankton and/or bacterially mediated reduction of As(V) may be important processes in the organic-rich blackwaters and/or sediment porewaters of the swamp, leading to the prevalence of As(III) in the water column.

Soil samples were collected from Norfolk, Virginia in order to examine the extent of particulate coal, and associated arsenic (As) deposition to local soils. The particulate coal originates from the adjacent coal shipping terminal at the Lambert's Point Docks, which is the largest marine coal shipping terminal in the Northern Hemisphere. Particulate coal was separated from soil samples using heavy liquid (i.e., sodium polytungstate) extraction. Sand-sized coal separates isolated from the soil samples were subsequently digested using concentrated nitric and sulfuric acid, and analyzed for As by high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). Selected total soil digests were also analyzed for As by HR-ICP-MS. Results indicate particulate coal ranges from less than 1% up to ∼20%, by weight, of the soil samples analyzed. Arsenic concentrations in sand-sized particulate coal extracted from these sediments range from undetectable levels (i.e., <3 ng/kg) up to 17.4 mg/kg, whereas total As concentrations in the soils range from 3 to 30.5 mg/kg. The data indicate that particulate coal originating at the Lambert's Point Docks is an additional source of As to local soils, especially sites proximal to the shipping terminal. Although the particulate coal itself likely poses only minor health hazards (if any), the environmental consequences of As transported with the particulate coal is not known.