Air Emissions from Exposed Contaminated Sediments and Dredged Material

Abstract

The sediment-to-air fluxes of two polycyclic aromatic hydrocarbons (phenanthrene and pyrene) and a heterocyclic aromatic hydrocarbon (dibenzofuran) from a laboratorycontaminated sediment and those of three polycyclic aromatic hydrocarbons (naphthalene, phenanthrene, and pyrene) from three field sediments were investigated in experimental microcosms. The flux was dependent on the sediment moisture content, air-filled porosity, and the relative humidity of the air flowing over the sediment surface. The mathematical model predictions of flux from the laboratoryspiked sediment agreed with observed values. The fluxes of compounds with higher hydrophobicity were more air-side resistance controlled. Conspicuous differences were observed between the fluxes from the laboratoryspiked and two of the three field sediments. Two field sediments showed dramatic increases in mass-transfer resistances with increasing exposure time and had significant fractions of oil and grease. The proposed mathematical model was inadequate for predicting the flux from the latter field sediments. Sediment reworking enhanced the fluxes from the field sediments due to exposure of fresh solids to the air. Variations in flux from the lab-spiked sediment as a result of change in air relative humidity were due to differences in retardation of chemicals on a dry or wet surface sediment. High moisture in the air over the dry sediment increased the competition for sorption sites between water and contaminant and increased the contaminant flux.

Vapor-Phase Transport of Explosives from Buried Sources in Soils

“…Low signatures were observed for explosives under all environmental conditions. Diffusion models, developed previously to predict polyaromatic hydrocarbon release from exposed dredged sediment, 13,14 were applied to simulate the explosives flux data satisfactorily with one fit parameter-soil to air partition constant.…”

“…13 The test soils, spiked with the chemicals, were placed in the flux chamber in contact with air flowing over the soil surface. Stainless-steel air sampling traps containing 0.2 g Tenax TA (25-30 mesh) were attached to the exit ports of the chambers to collect explosive compounds released into the airstream.…”

“…The surface flux depends on the soil-side and air-side resistances offered to mass transport of the contaminant. 13 The retardation factor, R f , accounts for the sorption of the diffusing chemical through the soil and is given by ε a ϩ b K SA , where K SA is the soil-air partition constant (L/kg) and b is the soil bulk density (g/cm 3 ). In the absence of direct measurements, K SA can be estimated for wet soils (Ͼ5% soil moisture content) using eq 2.…”

Volatilization of Contaminants from Suspended Sediment in a Water Column during Dredging

“…There are several ongoing studies on this issue of sediment aging and desorption and this matter remains to be resolved. 20,21 CONCLUSIONS Experimental data showed significant initial fluxes from both sediments upon resuspension and were directly related to suspended solids concentrations and air flow rate. Information about the scale of dredging and suspension volume is necessary to evaluate the air pollution potential.…”

Phytoremediation as a management option for contaminated sediments in tidal marshes, flood control areas and dredged sediment landfill sites

“…Valsaraj et al (1999) studied the air emissions from PAH-contaminated dredged sediment and found it to be dependent on soil moisture, the air-filled porosity and the relative humidity of the air. Miskewitz et al (2008) studied PCB emissions from dredged sediment in laboratory conditions and found that the addition of Portland cement decreased the time constant by a factor of 4 as compared to a non-treated sediment, i.e.…”