Sinks for trace metals, nutrients, and sediments in wetlands of the Chickahominy River near Richmond, Virginia

Abstract

The Chickahominy River drains 790 km ~ in southeastern Virginia, including approximately 155 km ~ of dense commercial, industrial, and urban development in the upper basin near R~chmond, Virginia. Previous studies have shown that total stream concentrations of trace metals and nutrients increased during storms, suggesting resuspension of contaminated sediments and (or) stormwater influxes of pollutants. The possible role of wetlands in maintaining water quality is of concern because the river furnishes about 46 percent of the water supply for the City of Newport News. Particle sizes of sediments and their corresponding total concentrations of carbon, nitrogen, copper, nickel, lead, and zinc were determined to assess their distribution within wetlands adjacent to the river. Except for Zn, concentrations of all measured constituents in the <63-urn-particle fraction were lower downstream of Richmond, suggesting that most contaminants are retained in the upper basin. Zinc concentrations increased along downstream reaches, peaking at 510 mg kg-' approximately 8 km below the confluence of Upham Brook with the Chickahominy River. Lead concentrations up to 192 mg kg-' were measured in sediments along Upham Brook near Richmond. Concentrations of Zn and Cu were highest in streambed sediments and lowest in elevated forested wetlands. The results suggest that the developing regions of the basin have a significarlt effect on sediment chemistry within the basin and that wetlands play a role in retaining these sediment-borne contaminants in upper reaches of the basin. Studies are underway to assess the stablity of these sediments and the capacity of these contaminated wetlands to continue fo assimilate them.

Design and Construction of Wetlands for Aqueous Transfers and Transformations of Selected Metals

“…For example, constructed wetlands may serve as buffer zones between valued aquatic systems and potential point or nonpoint source materials that cause adverse effects in the downstream portions of these aquatic systems (Rodgers and Dunn, 1994). Constructed wetlands have been used for treatment of many materials including metals and have been effective in removing metals with primarily lithic geochemical cycles from wastewater and acid mine drainage areas (Brodie et al, 1990;Gambrell et al, 1991;Hammer, 1992;Hupp et al, 1993;Lapakko and Eger, 1988;Masscheleyn et al, 1992;Niering, 1985;Puckett et al, 1993;Sinicrope et al, 1993;USEPA, 1988). Full-scale demonstration constructed wetlands have successfully treated industrial effluents and other recalcitrant materials (East, 1993;Gillette, 1992;Rogozinski et al, 1992).…”

Phosphorus retention in non-tidal palustrine forssted wetlands of the mid-atlantic region

“…Past studies have examined the geomorphologic structure and/or vegetational composition of these wetlands (e.g., Hack 1957, Parsons and Ware 1982, Osterkamp and Hupp 1984. More recent studies have focused on sediment and trace element dynamics (Hupp et al 1993, Puckett et al 1993.…”

Sediment and trace element trapping in a forested wetland, Chickahominy River, Virginia

“…Zinc has the highest concentrations, followed by lead and chromium. Lead, copper, cadmium, and tin are most concentrated along Upham Brook (site 2), the tributary that drains the most urban-industrial part of the basin (Puckett et al 1993). Concentrations of these elements decline from site 3 to site 8 (Figure 5), suggesting that most traceelement trapping occurs near the source of element entry within the upper parts of the study area where stream power is lowest (Figure 3).…”

“…Investigations in the basin suggest that deposited fines in wetland areas (site 3) have a substantially lesser bulk density. Puckett et al (1993) calculated a mean bulk density of 0.67 g/cm 3 at site 3, where sedimentation rates are highest, and this value was applied to all element-load computations at remaining sites. The <2000 um sediment fraction is used in the analysis because it includes virtually all mineral size clasts that settle in the vicinity of the trees sampled to estimate deposition rates and because there is little evidence to support differential trace-element uptake by trees among size clasts smaller than 2000 urn.…”