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Author: Jennifer A. Bower Publisher: ISBN: Category : Languages : en Pages : 236
Book Description
Lead (Pb), a trace metal notorious for its impacts on human health, has achieved worldwide environmental dispersal resulting from centuries of use by human society. The toxicity of Pb is governed largely by its mineral form, which is in turn controlled by pH, localized reactivity and soil processes that differ according to soil type, location and Pb source. Given the context of these localized dependencies, or site specificity, efforts to predict Pb toxicity and refine sustainable remediation techniques are most useful when Pb behavior is constrained and predicted within environments with homogeneous conditions, such as a single soil. I evaluated and predicted the behavior of Pb, a typical anthropogenic contaminant, within a single soil using bioaccessibility testing and predictive geospatial modeling to assess potential impacts and refine sustainable remediation methods. To test the hypothesis that Pb speciation is influenced by competitive sorption processes in soils, I investigated changes in mobility and speciation of Pb upon addition of amendments at multiple scales using flow-through column experiments, soil characterization and synchrotron-based x-ray techniques. Kriging and cokriging maps provided a successful estimation of background and total Pb, the latter incorporating housing age as a secondary variable to increase model accuracy, though efforts to automate detection of background Pb were complicated by approximation of building extents, and overall heterogeneity of soil Pb concentration gives high error. Acute Pb heterogeneity is observed at the scale of a single site among near-structure samples. At the city-scale, determination of bioaccessibility revealed that bioaccessible and total Pb are well-correlated, to the extent that bioaccessibility may be predicted for the soil underlying Burlington, VT; this information, combined with predictive blood lead level modeling and the CDC’s recent establishment of 5 μg kg-1 as a threshold for blood lead toxicity, enabled the establishment of a site-specific revised soil Pb limit of 360 mg kg-1, lower than the EPA’s general soil Pb threshold of 400 mg kg-1. Characterization of leached and unleached soil using scanning electron microscope energy dispersive spectroscopy (SEM-EDS) and microfocused x-ray techniques provided a first look at Pb paint species using synchrotron technologies. Pb was present within paint chips as hydrocerussite, but appeared to weather to anglesite over time. Pb also seemed to act as cation bridge, attracting clay minerals electrostatically and becoming incorporated into heterogeneous soil aggregates. Accessory paint elements are identified in soil and within paint chips and may further complicate these systems. Column experiments, at acidic pH, yielded little evidence of Pb mobility change in response to modification of competitive sorbents. Kinetics of Pb release were driven by pH, with Pb solubilizing at pH of ~4.9 as column soil acidifies. This work provides evidence for changes in Pb speciation over time in urban soils impacted by Pb paint, and presents a framework for predictive risk analysis at a local site using experimental and modeling tools. Multiscale observations and analytical results can be used in future efforts to model and refine sustainable remediation solutions within a site-specific context.
Author: Jennifer A. Bower Publisher: ISBN: Category : Languages : en Pages : 236
Book Description
Lead (Pb), a trace metal notorious for its impacts on human health, has achieved worldwide environmental dispersal resulting from centuries of use by human society. The toxicity of Pb is governed largely by its mineral form, which is in turn controlled by pH, localized reactivity and soil processes that differ according to soil type, location and Pb source. Given the context of these localized dependencies, or site specificity, efforts to predict Pb toxicity and refine sustainable remediation techniques are most useful when Pb behavior is constrained and predicted within environments with homogeneous conditions, such as a single soil. I evaluated and predicted the behavior of Pb, a typical anthropogenic contaminant, within a single soil using bioaccessibility testing and predictive geospatial modeling to assess potential impacts and refine sustainable remediation methods. To test the hypothesis that Pb speciation is influenced by competitive sorption processes in soils, I investigated changes in mobility and speciation of Pb upon addition of amendments at multiple scales using flow-through column experiments, soil characterization and synchrotron-based x-ray techniques. Kriging and cokriging maps provided a successful estimation of background and total Pb, the latter incorporating housing age as a secondary variable to increase model accuracy, though efforts to automate detection of background Pb were complicated by approximation of building extents, and overall heterogeneity of soil Pb concentration gives high error. Acute Pb heterogeneity is observed at the scale of a single site among near-structure samples. At the city-scale, determination of bioaccessibility revealed that bioaccessible and total Pb are well-correlated, to the extent that bioaccessibility may be predicted for the soil underlying Burlington, VT; this information, combined with predictive blood lead level modeling and the CDC’s recent establishment of 5 μg kg-1 as a threshold for blood lead toxicity, enabled the establishment of a site-specific revised soil Pb limit of 360 mg kg-1, lower than the EPA’s general soil Pb threshold of 400 mg kg-1. Characterization of leached and unleached soil using scanning electron microscope energy dispersive spectroscopy (SEM-EDS) and microfocused x-ray techniques provided a first look at Pb paint species using synchrotron technologies. Pb was present within paint chips as hydrocerussite, but appeared to weather to anglesite over time. Pb also seemed to act as cation bridge, attracting clay minerals electrostatically and becoming incorporated into heterogeneous soil aggregates. Accessory paint elements are identified in soil and within paint chips and may further complicate these systems. Column experiments, at acidic pH, yielded little evidence of Pb mobility change in response to modification of competitive sorbents. Kinetics of Pb release were driven by pH, with Pb solubilizing at pH of ~4.9 as column soil acidifies. This work provides evidence for changes in Pb speciation over time in urban soils impacted by Pb paint, and presents a framework for predictive risk analysis at a local site using experimental and modeling tools. Multiscale observations and analytical results can be used in future efforts to model and refine sustainable remediation solutions within a site-specific context.
Author: Grant William Reeder Publisher: ISBN: Category : Bioavailability Languages : en Pages : 168
Book Description
The potential of a soil to immobilize heavy metal ions is dependent on the presence of adsorption sites, and the stability of metal species over the range of geochemical conditions present in the soil over time. Lead (Pb) is a cumulative toxin that is enriched in much of the urban pedosphere due to historical use of Pb-based paint and Pb-amended gasoline. Because in-situ remediation of Pb is possible if the bioavailable fraction can be rendered inert, understanding Pb-sorbent interactions is necessary to accurately and efficiently alter Pb speciation in soils. The objectives of this study are to 1) determine efficient ways to predict Pb behavior at the field scale, and 2) characterize microscale controls on Pb speciation. A combination of geospatial and analytical tools has been used across a variety of spatial scales to provide the first multiscale analysis of microenvironment impact on Pb speciation in soils. This research investigated Pb distribution at the field scale (in Burlington, VT), and mobility at the microscale. The field-scale study has shown that the relationship between total Pb and bioaccessible Pb is not linear, in stark contrast to the existing conceptual model of this relationship. It was determined that the disproportional influence of fine-fraction Pb in low total-Pb soils results in elevated bioavailability. Microscale investigations determined that there is a positive correlation between the density of reactive microenvironments and the release of Pb from contaminated soil, and that altered distributions of microenvironments significantly alters the rate of Pb release. This research identifies specific mechanisms controlling Pb behavior in soils at both the field and the microscale, which can be used to inform improvements to implementation of remediation.
Author: Lauren R. Stewart Publisher: ISBN: Category : Bioavailability Languages : en Pages : 61
Book Description
Lead poisoning in young children is a concern in many urban areas, even 30 years after the banning of Pb-based paint and leaded gasoline. Soil and dust have been found to be prominent lead exposure pathways for children because young children often inadvertently ingest contaminated soil and dust through exploratory hand-to-mouth activities. In 2010, 16.6% of 6,550 children tested in Toledo, OH had blood lead levels (BLLs) above the CDC lead poisoning reference level of 5 μg/dL. The objectives of this study were 1) to quantify the concentration and distribution of total and bioavailable lead in soils of Toledo, OH; 2) to relate total lead and bioavailable lead in soils to BLLs in children; and 3) to model the relationship between BLLs in children and spatial variables such as housing age and road density. Outreach education served as a means to educate students about the dangers of soil lead as well as the importance of sampling protocols in science. Students in Toledo area schools were instructed on proper USEPA soil sampling guidelines and were asked to collect soil samples from their yards. A subsample of 81 soils was analyzed for total lead and bioavailable lead. Site-specific total lead and bioavailability data were used in the USEPA Integrated Exposure Uptake and Biokinetic (IEUBK) model to predict BLLs for children under 7 years of age. A spatial index model was derived using fuzzy sets, analytical hierarchy process (AHP) and weighted linear combination (WLC) to relate 6 spatial predictor variables to the predicted BLLs. It was found that 8.6% of sampled sites had total lead concentrations above the USEPA action level of 400 mg/kg, but 28.4% of soils samples yielded predicted elevated BLLs, suggesting the action level is set too high. The majority of soil samples had lead bioavailability values above 60%, thus increasing the risk of lead poisoning. The spatial variables influencing risk of lead poisoning from most important to least important were age of housing, road density, percent impervious surfaces, home value, household income and soil type. The data predict that lead poisoning disproportionately affects children from low socioeconomic status families.
Author: Kirsten Schwarz Publisher: ISBN: Category : Lead Languages : en Pages : 138
Book Description
Lead contamination of the urban environment is not a new phenomenon. A great deal of research has focused on the health effects of lead-based paint. Less attention, however, has been given to the potential problem of soil contaminated with lead from the past use of lead-containing products such as lead-based paint and leaded gasoline. Identifying areas of high contamination is necessary in order to prioritize soil remediation and public health efforts. This requires a comprehensive understanding of a highly heterogeneous and dynamic system. This research addresses whether land use or land cover is a better predictor of lead concentrations in soil. Specifically, this research addresses whether landscape features, including trees, lawns, buildings, and roads, can be used to predict lead concentrations in soil. Through a method of rapid assessment of soil lead concentrations, I gathered spatially explicit data from urban residential yards to generate several models that predict the spatial distribution of lead in soil. Using the results of these models, potential inequities associated with the modeled spatial distribution of lead in soil and socio-demographic features were explored. The results of this study suggest that the distribution of lead in urban residential soils is more closely correlated with features of urban land cover compared to metrics of land use. Specifically, the spatial distribution of lead in urban residential soils is strongly influenced by three factors: housing age, distance to the major road networks, and distance to built structures. Through the comparison of various spatial models, this research demonstrates that a greater amount of variation in the data is explained by machine learning techniques compared to traditional modeling techniques. In addition, important correlations between the modeled distribution of lead in soil and socio-demographic features such as race and poverty have been identified. Specifically, a greater amount of soil contamination is predicted to be present in high poverty areas. This research contributes to the growing field of urban ecology by advancing our knowledge of how spatial heterogeneity affects the distribution of a critical pollutant in urban systems. This work also tests the suitability of using land cover as a predictive ecological variable.
Author: M.J. McLaughlin Publisher: Springer Science & Business Media ISBN: 9401144737 Category : Science Languages : en Pages : 283
Book Description
Over forty years ago, concern was first focussed on cadmium contamination of soils, fertilisers and the food chain. Adverse effects on human health were first highlighted nearly 30 years ago in Japan with the outbreak of Itai-itai disease. Since then, substantial research data have accumulated for cadmium on chemistry in soils, additions to soils, uptake by plants, adverse effects on the soil biota and transfer through the food chain. However, this information has never been compiled into a single volume. This was the stimulus for the Kevin G. Tiller Memorial Symposium "Cadmium in Soils, Plants and the Food Chain", held at the University of California, Berkeley, in June 1997 as part of the Fourth International Conference on the Biogeochemistry of Trace Elements. This symposium brought together leading scientists in the field of cadmium behaviour in soils and plants, to review the scientific data in the literature and highlight gaps in our current knowledge of the subject. This series of review papers are presented here and deal with the chemistry of cadmium in soils, the potential for transfer through the food chain and management to minimise this problem. We hope this information provides a sound scientific basis to assist development of policies and regulations for controlling cadmium in the soil environment.
Author: Astrid Sigel Publisher: Walter de Gruyter GmbH & Co KG ISBN: 3110434334 Category : Science Languages : en Pages : 596
Book Description
Volume 17, entitled Lead: Its Effects on Environment and Health of the series Metal Ions in Life Sciences centers on the interrelations between biosystems and lead. The book provides an up-to-date review of the bioinorganic chemistry of this metal and its ions; it covers the biogeochemistry of lead, its use (not only as gasoline additive) and anthropogenic release into the environment, its cycling and speciation in the atmosphere, in waters, soils, and sediments, and also in mammalian organs. The analytical tools to determine and to quantify this toxic element in blood, saliva, urine, hair, etc. are described. The properties of lead(II) complexes formed with amino acids, peptides, proteins (including metallothioneins), nucleobases, nucleotides, nucleic acids, and other ligands of biological relevance are summarized for the solid state and for aqueous solutions as well. All this is important for obtaining a coherent picture on the properties of lead, its effects on plants and toxic actions on mammalian organs. This and more is treated in an authoritative and timely manner in the 16 stimulating chapters of Volume 17, which are written by 36 internationally recognized experts from 13 nations. The impact of this recently again vibrant research area is manifested in nearly 2000 references, over 50 tables and more than 100 illustrations (half in color). Lead: Its Effects on Environment and Health is an essential resource for scientists working in the wide range from material sciences, inorganic biochemistry all the way through to medicine including the clinic ... not forgetting that it also provides excellent information for teaching.
Author: A. Hunt Publisher: ISBN: Category : Dust Languages : en Pages : 17
Book Description
Particulate lead in urban soils from Syracuse, NY, was characterized by computer assisted scanning electron microscopy (SEM) and X-ray energy spectroscopy (EDX). Samples collected from the building line of houses built prior to 1940 showed bulk lead values of 870 to 5350 ?g/g, the origin of which is suspected to have been from lead-based paints. In contrast to previous analyses of household dusts, only a small fraction of the particulate lead could be identified with potential input materials; most of the lead is strongly associated with the iron and manganese phases in the soils. Estimates of the amount of soil bulk lead amenable to SEM characterization ranged from 20 to 115% with lower values being associated with lower soil pH. The results suggest that soil lead derived from paint undergoes a relatively rapid transformation and redistribution with consequent loss of its potentially distinctive individual particle identity.
Author: Jennifer A. Bower
Author: Jennifer A. Bower
Author: Grant William Reeder
Author: Lauren R. Stewart
Author: Kirsten Schwarz
Author: Brian E. Davies
Author: 
Author: Deborah E. Morrison-Ibrahim
Author: M.J. McLaughlin
Author: Astrid Sigel
Author: A. Hunt