Proceedings of the Annual International Conference on Soils: Volume 17, Issue 1
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(2012-01-01)
Characteristics of Soils and Heavy Metal Content of Vegetation in Oil Spill Impacted Land in Nigeria
(2012-01-01) Bada, Babatunde Saheed; Olarinre, Tosin Akinola
This study examined the impact of an oil spill on soil characteristics and heavy metal content of vegetation. Soil and vegetation were sampled using a 1 metre square quadrant at distances of 1 m, 10 m, 20 m and 30 m from the oil spill. After vegetation identification, they were separated into leaves, stems and roots. Analysis of soil characteristics and heavy metals (Pb, Cd and Zn) content of the vegetation was carried out. The data were analyzed using descriptive statistics and ANOVA. Calopogonium mucunoides, Axonopus compressus and Sida acuta were identified. Leaves had higher heavy metals content followed by stems and roots. Concentrations of heavy metals in the soils with respect to distances were in the order of 1 m > 10 m > 20 m > 30 m. Soil organic carbon content ranged from 18.75 – 27. 30 g/kg. The soils heavy metal concentrations ranged from 0.10 – 0.18 mgCd/kg, 0.34 – 0.46 mgZn/kg and 0.28 – 0.44 mgPb/kg.
Assessing the Bioavailability of Arsenic in Sediments for Use in Human Health Risk Assessment
(2012-01-01) Lamie, Pamela O
Arsenic concentrations in sediments in a wetlands located downgradient from a landfill in northeastern Massachusetts were found to be over 1,000 mg/kg in several locations with a maximum detected concentration of 4,500 mg/kg. The elevated arsenic in sediment is likely the result of the dissolution of iron and arsenic in the underlying rock under reducing conditions mobilized with the groundwater and co-precipitating out into the sediments when groundwater reaches the oxidizing surface water, producing an iron and arsenic bearing floc. Approximately 15 acres of wetlands appear to be impacted from elevated arsenic concentrations. To assess the potential impacts to human health and to determine the extent of acreage requiring remedial action, a site-specific bioavailability factor was developed using an in vitro laboratory assessment. While in vivo (live animal) studies are considered to be the most accurate measures of bioavailability for assessing absorption of contaminants by humans, the in vivo studies are expensive and lengthy. The in vitro approach undertaken for this assessment simulates digestive activity in the stomach, including residence time, pH, temperature, agitation, and solid to liquid ratio. This in vitro laboratory approach coupled with an adjustment based on in vivo data, along with a mineralogical characterization of the impacted sediments, served to develop a site-specific bioavailability factor that resulted in more accurate human health risk characterization results.
Monitoring Sources of Mercury in the Atmosphere
(2012-01-01) Metcalf, James; Mose, Douglas G
In Virginia and most other states, rain and snow collection stations have been used to determine the concentration of mercury in precipitation. These mercury measurements are distributed by the National Atmospheric Deposition Program through the Illinois State Water Survey (http://nadp.sws.uiuc.edu). Mercury deposition data has been gathered for over a decade and may be compared to the on-line data currently reported from collection sites. Coal-burning power plants are thought to contribute most of the atmospheric mercury, and it was thought that the precipitation collections would prove this hypothesis. In Virginia, this hypothesis is supported. It has been found that the atmospheric content of mercury increases during prolonged intervals without precipitation. In this study, it was found that the atmospheric content of mercury was exceptionally low following an unusually prolonged precipitation event.
Mercury Exposure Considerations: Evaluating the Chemical Form and Activities of the Individual
(2012-01-01) Teaf, Christopher M; Garber, Michele
Evaluation of exposure to mercury in an environmental or an occupational context is more complex than that for many other substances, insofar as it requires consideration of a combination of factors including the form of mercury present and the associated toxicology (e.g., elemental vs. organic vs. inorganic), as well as characteristics of the individual/exposure being evaluated (e.g., route, frequency, duration, and magnitude of exposure). Given the major differences in absorption of mercury forms by route, it is not sufficient to discuss simply “mercury exposure”, as often occurs in media reports. Methods for addressing each of these characteristics are discussed, and specific case studies are presented to illustrate the practical significance of differences in contact with several common mercury forms that may be encountered under variable exposure circumstances. In addition, a discussion is presented of the variability of responses between adults and children to selected mercury forms, with attention to similarities or differences in observed effects. Finally, common sources of mercury exposure to the general population are discussed, for purposes of comparison with potential exposures in the workplace.