Improving risk assessments for manufactured gas plant soils by measuring PAH availability.

Remediation of soils at oil-gas manufactured gas plant (MGP) sites is driven primarily by the human health risks posed by the carcinogenic polycyclic aromatic hydrocarbons (PAHs), particularly benzo[a]pyrene (BaP), that are associated with lampblack residues. Although PAHs on lampblack are tightly sorbed, risk assessments do not account for this reduced availability. A multi-investigator study of 7 oil-gas MGP site soil samples demonstrated that the dermal and ingestion absorption factors are far lower than current default assumptions used in risk assessments.

A protocol to estimate the release of anthropogenic hydrocarbons from contaminated soils.

An operational protocol, appropriate for a tier 1 or tier 2 type relative risk evaluation of a site that has polycyclic aromatic hydrocarbon (PAH) or petroleum hydrocarbon impacted soils, was developed to estimate the fraction of anthropogenic hydrophobic hydrocarbons that will be released rapidly from such soils. The development of this protocol used over 400 datasets from 40 different field samples to establish and verify the operational protocol. The datasets resulted from four-month kinetic desorption studies of these field samples.

Comparing PAH availability from manufactured gas plant soils and sediments with chemical and biological tests. 1. PAH release during water desorption and supercritical carbon dioxide extraction.

Soil and sediment samples from oil gas (OG) and coal gas (CG) manufactured gas plant (MGP) sites were selected to represent a range of PAH concentrations (150-40,000 mg/kg) and sample matrix compositions. Samples varied from vegetated soils to lampblack soot and had carbon contents from 3 to 87 wt %. SFE desorption (120 min) and water/XAD2 desorption (120 days) curves were determined and fit with a simple two-site model to determine the rapid-released fraction (F) for PAHs ranging from naphthalene to benzo[ghi]perylene.

PAH release during water desorption, supercritical carbon dioxide extraction, and field bioremediation.

Removal rates of polycyclic aromatic hydrocarbons (PAHs) from manufactured gas plant (MGP) soils were determined using water desorption for 120 days and mild supercritical carbon dioxide extraction (SFE) for 200 min. Both techniques were used to compare the changes in desorption rates for individual PAHs from untreated and treated soils that were obtained from a field biotreatment unit after 58, 147, and 343 days. Water desorption profiles (plotted in days) and SFE profiles (plotted in minutes) were very similar regardless of whether a PAH was rapidly or slowly removed.

Predicting hydrocarbon removal from thermally enhanced soil vapor extraction systems. 2. Field study.

The effectiveness of a thermally enhanced soil vapor extraction (SVE) system to remove semi-volatile organic chemicals (SVOCs) was investigated in a field study. The data allowed the calculations of SVOC removal rates at several temperatures. A previous laboratory study using the same field soils had developed a relationship between SVOC removal rate constants and inverse temperature.

Predicting hydrocarbon removal from thermally enhanced soil vapor extraction systems. 1. Laboratory studies.

Conventional soil vapor extraction (SVE) systems have a limited effectiveness at removing semi-volatile chemicals from soil. Raising chemical vapor pressures by heating soil in-situ can decrease remediation time and help remove semi-volatile chemicals that otherwise would not be removed by conventional SVE. The increased compound removal rate that results from use of thermally enhanced SVE was investigated in laboratory studies.

Effect of Media Nitrogen Concentration on Biofilter Performance.

A pilot-scale biofilter was used to determine important design and operational parameters related to biofiltration of volatile organic compounds (VOCs). The importance of nitrogen availability in terms of biofilter performance was determined. Results showed that microbially accessible nitrogen (ammonia and nitrate) in the areas of highest microbial activity were depleted when toluene loading rates were 30 g/m-h or greater.

Effect of Periods of Non-Use on Biofilter Performance.

A biofilter does not operate as a true filter, but removes chemicals from gases by sorption and biologically degrades them. The objective of the research reported in this paper was to investigate the effect of periods of non-use on biofilter performance. The concept of non-use had two meanings in this research: "no chemical loading," which indicated that humidified air was passing through the biofilter with no chemicals, and "stagnant," which reflected that no flow at all was passing through the biofilter.

Bioconcentration and biokinetics of heavy metals in the earthworm.

This study examines the steady state and non-steady state kinetics of five metals, cadmium, copper, lead, nickel, and zinc in earthworms. The steady state kinetics are based on field studies in which worms from contaminated and uncontaminated sites were collected and measurements were made of concentrations in the earthworms and soils. For each of the metals, evidence suggests that bioconcentration depends on the metal concentrations in the soil; bioconcentration is greater at lower soil concentrations.

The toxicity of p-aminophenol in the Sprague-Dawley rat: effects on growth, reproduction and foetal development.

p-Aminophenol (p-AP) was fed in the diet to groups of 40 male and 45 female Sprague-Dawley rats at levels of 0.07, 0.2 or 0.

Evaluation of the teratological and dominant lethal potential of N,N-bis-(2-hydroxyethyl)-p-phenylenediamine sulphate in a 6-month feeding study in rats.

N,N-Bis-(2-hydroxyethyl)-p-phenylenediamine sulphate (N,N-Bis) was administered to 40 male and 45 female Sprague-Dawley rats per group by admixture with their diets at levels of 0.03, 0.1 and 0.

A subchronic, teratologic, and dominant lethal study of 2-methylresorcinol in rats. II. Teratologic and dominant lethal study.

2-Methylresorcinol (2-MR) was administered to groups of 40 male and 35 female Sprague-Dawley rats by admixture with the diets at levels of 0.1, 0.4, and 1.

A subchronic, teratologic, and dominant lethal study of 2-methylresorcinol in rats. I. Subchronic toxicity.

2-methylresorcinol (2-MR) was administered to groups of 40 male and 35 female Sprague-Dawley rats by admixture with diets at levels of 0.1, 0.4, and 1.

Results of teratogenicity testing of m-aminophenol in Sprague-Dawley rats.

meta-Aminophenol (m-AP) was administered in the diet to female Sprague-Dawley rats for a period of at least 90 days at levels of 0.1, 0.25, and 1.

The absence of teratogenic hazard potential of p-phenylenediamine in Sprague-Dawley rats.

Para-phenylenediamine (PPD) was administered by gavage to pregnant Sprague-Dawley Rats at dose levels of 5, 10, 15, 20, and 30 mg/kg/day on days 6 through 15 of gestation (day 0 = day sperm was found in the vagina). A sham control group and a pair fed control group were studied at the same time. Pregnant animals were killed on day 20 of gestation and 1/3 of the fetuses were examined for visceral malformations and 2/3 for skeletal malformations and variations.

Heritable translocation study on two hair dye formulations.

Sexually mature Charles River Sprague Dawley CD outbred male rats received topical applications of hair dyes twice weekly for 10 weeks. They were then mated to one sexually mature female of the same strain each week for three weeks. One hundred F1 males from these matings, maintained under standard conditions for 12 weeks, were paired with one mature female per week for three weeks.

Hazardous solid waste from agriculture.

Large quantities of food processing, crop, forestry, and animal solid wastes are generated in the United States each year. The major components of these wastes are biodegradable. However, they also contain components such as nitrogen, human and animal pathogens, medicinals, feed additives, salts, and certain metals, that under uncontrolled conditions can be detrimental to aquatic, plant, animal, or human life.

Dominant lethal mutagenicity study on hair dyes.

A dominant lethal mutagenicity study was performed in rats with the following chemicals that may be used to dye hair: 2-nitro-p-phenylenediamine, 4-nitro-o-phenylenediamine, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, p-toluenediamine, 2,4-diaminoanisole, 2,5-diaminoanisole, 2-amino-4-nitrophenol, 2-amino-5-nitrophenol, and 4-amino-2-nitrophenol. The compounds were administered intraperitoneally three times weekly for 8 weeks to groups of 20 sexually mature Charles River CD male rats at a dose of 20 mg/kg. This amount of dye is an enormous exaggeration of the human exposure from brief montly topical application of a hair color product containing 2 g (40 mg/kg) or less total dye.