Arsenic (As) is a common contaminant in soils, and analysis of soils by inductively coupled plasm... more Arsenic (As) is a common contaminant in soils, and analysis of soils by inductively coupled plasma–mass spectrometry (ICP‐MS) is often used to detect As in soil extracts. Internal standards (ISs) are part of ICP‐MS analyses to enhance precision and accuracy by compensating for instrument variability; however, an improper choice of IS can result in negative analytical bias. The goal of this study was to develop a protocol for evaluating ISs commonly used in ICP‐MS. Three soils of varying clay content and total As were extracted with a dilute electrolyte [0.005 mol L–1 Mg(NO3)2] and an acid digest. Arsenic concentrations were quantified by ICP‐MS using typical ISs: 6Li, 45Sc, 69Ga, 89Y, 103Rh, 115In, 159 Tb, and 209Bi. Standard addition was used as a benchmark for As quantification. The most consistent IS was 115In. Elevated, naturally occurring concentrations were detected for several of the ISs, particularly in the total digests, emphasizing the necessity for screening soils prior t...
Arsenic (As) and lead (Pb) are common soil contaminants, environmentally hazardous, and are threa... more Arsenic (As) and lead (Pb) are common soil contaminants, environmentally hazardous, and are threats to public health. Addition of soluble phosphate is known to be effective for in situ remediation of Pb-contaminated soils, but phosphate additions displace As from the soil particles and increase As concentration in soil solution. This study examined the dual use of iron (Fe) and phosphorus (P) amendments to soil, highly contaminated with As and Pb. The test soil originated from a former smelter site in Utah with As and Pb concentrations of 66,400 mg Pb kg-1 and 7,520 mg As kg-1 . Goethite, ferrihydrite, and iron-rich water treatment residuals (Fe-WTR) were added to immobilize As, and soluble P was added to reduce Pb lability. The Fe amendments were added in Fe:As mole ratios ranging from 1:1 to 1:10, and P was added in P:Pb mole ratios from 0.2:1 to 5:1. Fe-WTR was found to be the most effective Fe amendment. When Fe-WTR and P were added simultaneously, the P concentrations required to immobilize Pb resulted in increased mobilization of As, even when Fe-WTR were added at 10:1 Fe:As. However, when P was added first at 5:1 P:Pb, incubated for one week, and then amended with Fe-WTR at 10:1 Fe:As, both Pb and As were significantly immobilized. The proposed process is a practical remediation approach to soils co-contaminated with Pb and As while encouraging re-use of Fe-WTR as a sustainable amendment. This article is protected by copyright. All rights reserved.
Increasing organic rice production in Texas can have mixed impacts on soil health. • Rice grain y... more Increasing organic rice production in Texas can have mixed impacts on soil health. • Rice grain yields were reduced in organic systems. • Soil methane emissions increased in organic systems. • DNDC simulations predicted organic fertilizer impacts on yields and soil emissions. • Difference in organic and conventional fertilized grain yields diminished over time.
AbstractSmectite-bearing, expansive clayey soils are common in many areas of Texas, causing damag... more AbstractSmectite-bearing, expansive clayey soils are common in many areas of Texas, causing damage to pavements and building foundations by cyclic shrinking and swelling. The mechanism of shrinking...
The purpose of this study was to assess the impact of non-traditional water irrigation on the che... more The purpose of this study was to assess the impact of non-traditional water irrigation on the chemical and mineralogical properties of the calcareous clayey Angelo soil from West Texas. The exponential rise in population and climate change is leading to further increase in freshwater (FW) depletion, treated wastewater (TWW) and brackish groundwater (BGW) thus offer the possibility of attractive alternative water resources for irrigated agriculture. To address the differences between TWW and BGW, water samples were collected and analyzed. The water samples were analyzed for salt and nutrient content. Soil samples from three horizons (Ap, A, and B) were obtained from three different fields: Rainfed (RF), BGW irrigated, and TWW irrigated. Soil was analyzed for texture, salinity, sodicity, and carbon content. Clay mineralogy of the three different fields was analyzed using the B-horizons. TWW is slightly saline compared to the moderately saline BGW. Although, the exchangeable sodium percentage (ESP), sodium adsorption ratio (SAR), and electroconductivity (EC) have marginally increased compared to RF, however all the values of interest (SAR<13, ESP<15, pH<8.5, and EC<4) were low indicating no sodicity nor salinity problems. Smectite, illite, and kaolinite were identified in the three B-horizon samples by XRD. Overall, there was no major changes in the soil observed, which deems TWW and BGW as viable replacements for FW in arid and semi-arid regions. iii DEDICATION I dedicate this work to my parents, significant other, family, and my friends for all their encouragement and support throughout my journey to obtain this degree. thank Mr. Mathew Wilde for allowing access to his land for soil and water sampling. Without his permission and cooperation, this research would not have been possible. I would like to acknowledge WEF Nexus Research Group members and their support and help. Thanks also go to my friends and colleagues and the department faculty and staff for making my time at Texas A&M University a great experience. Finally, thanks to my parents for their encouragement and to my significant other for her patience, support, and love.
Public reporting burden for the collection of information is estimated to average 1 hour per resp... more Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
Plant physiology and biochemistry : PPB / Societe francaise de physiologie vegetale, Jan 25, 2015
Cerium oxide nanoparticles (CeO2 NP) are a common component of many commercial products. Due to t... more Cerium oxide nanoparticles (CeO2 NP) are a common component of many commercial products. Due to the general concerns over the potential toxicity of engineered nanoparticles (ENPs), the phytotoxicity and in planta accumulation of CeO2 NPs have been broadly investigated. However, most previous studies were conducted in hydroponic systems and with grain crops. For a few studies performed with soil grown plants, the impact of soil properties on the fate and transport of CeO2 NPs was generally ignored even though numerous previous studies indicate that soil properties play a critical role in the fate and transport of environmental pollutants. The objectives of this study were to evaluate the soil fractionation and bioavailability of CeO2 NPs to Raphanus sativus L (radish) in two soil types. Our results showed that the silty loam contained slightly higher exchangeable fraction (F1) of cerium element than did loamy sand soil, but significantly lower reducible (F2) and oxidizable (F3) fract...
Functions of Natural Organic Matter in Changing Environment, 2012
The objective of this study was to examine ryegrass for phytoremediation of 2,4-DCB (a polychlori... more The objective of this study was to examine ryegrass for phytoremediation of 2,4-DCB (a polychlorinated biphenyl congener)-contaminated soils. A pot experiment was conducted for 45 days using two soils (a Mollisol and an Alfisol) in greenhouse. Results showed that dissipation rates in both rhizosphere soils were significantly higher than those in controls, which were not spiked with 2,4-DCB. 2,4-DCB concentration in rhizospheric soils decreased from the initial concentration 30 ± 0.5 mg·kg−1to 3.42 mg·kg−1 in the Mollisols, as compared to 13.94 mg·kg−1 in non-rhizospheric soils. Also, a significant rhizospheric effect was observed in the Alfisols soil. A bioconcentration factor (BCF) was used to indicate the ability of ryegrass to tolerate and accumulate xenobiotics. Results showed that the BCF in shoots and roots of plants varied (P < 0.05). BCF in roots and shoots were 0.149 and 0.050 in the Mollisol soil and 0.122 and 0.027 in the Alfisol, respectively.
Proceedings of the Water Environment Federation, 2009
Visual MINTEQ (v. 2.53) was adopted to study the equlibria of potential fouling minerals in UV di... more Visual MINTEQ (v. 2.53) was adopted to study the equlibria of potential fouling minerals in UV disinfection applications. Data from fouling experiments included description of water chemistry, including the concentrations of common metal ions and ligands in solution, water temperature, pH, redox potential, hardness, etc. The modeling results were used as a template to identify likely precipitating minerals in the fouling process. Redox effect was examined for the precipitation of iron and manganese. The modeling results suggested that the hydrolytic form of Fe(III) is the dominant mineral that has potential to precipitate due to its oversaturated status. For experiments manganese precipitation appeared likely, the highly-oxidized Mn-containing minerals, such as MnO 2 , MnPO 4 , and MnOOH, appeared to have the greatest potential to precipitate. Among these forms, the saturation index of MnO 2 was usually the largest.
Petroleum contamination poses a significant threat to environmental ecosystems worldwide. Phytore... more Petroleum contamination poses a significant threat to environmental ecosystems worldwide. Phytoremediation can be used to enhance degradation of petroleum contaminants in soil. However, selection of plants for phytoremediation has proven to be complicated. This research examines the heritability of the alfalfa cultivar Riley for phytoremediation based on parental total petroleum hydrocarbon (TPH) degradation after twelve months of growth. Traits other than degradation potential, such as root and shoot yield, height, and maturity, were examined for use as selection traits. Riley showed moderate to low heritability that suggests the possibility of breeding for phytoremediation efficiency. In addition, root and shoot yield were found to correlate to TPH degradation. Crosses in which the female parent was typically associated with low TPH dissipation yielded progeny that were high efficiency TPH degraders.
Soil and Sediment Contamination: An International Journal, 2001
Phenanthrene biodegradation was investigated at different soil water contents [0.11, 0.22, 0.33, ... more Phenanthrene biodegradation was investigated at different soil water contents [0.11, 0.22, 0.33, 0.44 g H2O (g soil)− 1] to determine the effects of water availability on biodegradation rate. A subsurface horizon of Kennebec silty loam soil was used in this study.[9-14C] ...
Small arms firing ranges (SAFRs) contain a mixed amount of bullets and bullet fragments accumulat... more Small arms firing ranges (SAFRs) contain a mixed amount of bullets and bullet fragments accumulated throughout their designed lifetime. Lead-antimony (Pb-Sb) alloy copper (Cu) jacketed bullets are a common modern ammunition used at SAFRs. The impact of bullets with berm material (i.e., soil) generates a heterogeneous distribution of bullets and bullet fragments in the surrounding soil. As bullets and bullet fragments corrode in the berm soil, the migration potential for antimony compared to other metals is quite high. The goal of this study was to evaluate the spatial Sb migration potential from an SAFR as compared to lead, copper, and zinc (Zn) migration from the same SAFR. Berm soil samples were collected along with surface and ground water samples for a preliminary investigation of the Sb migration from an active SAFR. In addition, different aqueous sample preservation techniques were used and evaluated. Soil sample analysis results show the presence of the metals (i.e., Pb, Sb, Cu, and Zn) in the range floor soil samples, indicating the migration of these metals from the berm to the range floor. The groundwater samples indicate that Sb was migrating from the SAFR more readily than the other metals based on the concentration of Sb in the monitoring well farthest from the SAFR berm.
A column experiment was conducted to determine the impact of soil cover and plants on heavy metal... more A column experiment was conducted to determine the impact of soil cover and plants on heavy metal leaching from mine railings and heavy metal contaminated soil. Columns made of PVC were constructed with 30 cm subsoil covered by 30 cm of mine tailings followed by 0, 30, or 60 cm of dean topsoil. Two grasses, tall fescue (Festuca arundinacea Schreb.) and big bluestem (Andropogon gerardii), were grown in the columns. The columns were leached at a slow rate for 1 yr with a 0.001 M CaCl2 solution under unsaturated conditions. The presence of both tall fescue and big bluestem increased Zn and Cd concentrations in the leachate. Lead concentrations in leachates were not affected by the presence of plants. Although plants generally reduced the total amount of water leached, total mass of Zn and Cd leached generally was not impacted by plants. Total mass of Pb leached was positively correlated (r = 0.9) with total leachate collected from each column. Covering the mine tailings with 60 cm of topsoil (with or without vegetation) increased the mass of Zn and Cd leached relative to no topsoil. When the subsoil was absent, Zn and Cd leaching increased by as much as 20-fold, verifying the ability of soil to act as a sink for metals. Mine tailing remediation by establishing vegetation can reduce Pb movement but may enhance short-term Cd and Zn leaching. However, the changes were relatively small and do not outweigh the benefits of using vegetation in mine tailings reclamation.
Plant-bacterial combinations can increase contaminant degradation in the rhizosphere, but the rol... more Plant-bacterial combinations can increase contaminant degradation in the rhizosphere, but the role played by indigenous root-associated bacteria during plant growth in contaminated soils is unclear. The purpose of this study was to determine if plants had the ability to selectively enhance the prevalence of endophytes containing pollutant catabolic genes in unrelated environments contaminated with different pollutants. At petroleum hydrocarbon contaminated sites, two genes encoding hydrocarbon degradation, alkane monooxygenase ( alkB ) and naphthalene dioxygenase ( ndoB ), were two and four times more prevalent in bacteria extracted from the root interior (endophytic) than from the bulk soil and sediment, respectively. In field sites contaminated with nitroaromatics, two genes encoding nitrotoluene degradation, 2-nitrotoluene reductase ( ntdAa ) and nitrotoluene monooxygenase ( ntnM ), were 7 to 14 times more prevalent in endophytic bacteria. The addition of petroleum to sediment do...
Contamination of soil by hazardous substances poses a significant threat to human, environmental,... more Contamination of soil by hazardous substances poses a significant threat to human, environmental, and ecological health. Cleanup of the contaminants using destructive, invasive technologies has proven to be expensive and more importantly, often damaging to the natural resource properties of the soil, sediment, or aquifer. Phytoremediation is defined as the cleanup of contaminated sites using plants. There has been evidence of enhanced polycyclic aromatic hydrocarbons (PAHs) degradation in rhizosphere soils for a limited number of plants. However, research focusing on the degradation of PAHs in the rhizosphere of trees is lacking. The objective of this study was to assess the potential use of trees to enhance degradation of PAHs located in manufactured gas plant-impacted soils. In greenhouse studies with intact soil cores, acenaphthene, anthracene, fluoranthene, naphthalene, and phenanthrene decreased significantly (p &amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) in green ash (Fraxinus pennsylvanica Marshall) and hybrid poplar (Populus deltoides x P. nigra DN 34) phytoremediation treatments when compared to the unplanted soil control. Increases in PAH microbial degraders in rhizosphere soil were observed when compared to unvegetated soil controls. In addition, the rate of degradation or biotransformation of PAHs was greatest for soils with black willow (Salix nigra Marshall), followed by poplar, ash, and the unvegetated controls. These results support the hypothesis that a variety of plants can enhance the degradation of target PAHs in soil.
Arsenic (As) is a common contaminant in soils, and analysis of soils by inductively coupled plasm... more Arsenic (As) is a common contaminant in soils, and analysis of soils by inductively coupled plasma–mass spectrometry (ICP‐MS) is often used to detect As in soil extracts. Internal standards (ISs) are part of ICP‐MS analyses to enhance precision and accuracy by compensating for instrument variability; however, an improper choice of IS can result in negative analytical bias. The goal of this study was to develop a protocol for evaluating ISs commonly used in ICP‐MS. Three soils of varying clay content and total As were extracted with a dilute electrolyte [0.005 mol L–1 Mg(NO3)2] and an acid digest. Arsenic concentrations were quantified by ICP‐MS using typical ISs: 6Li, 45Sc, 69Ga, 89Y, 103Rh, 115In, 159 Tb, and 209Bi. Standard addition was used as a benchmark for As quantification. The most consistent IS was 115In. Elevated, naturally occurring concentrations were detected for several of the ISs, particularly in the total digests, emphasizing the necessity for screening soils prior t...
Arsenic (As) and lead (Pb) are common soil contaminants, environmentally hazardous, and are threa... more Arsenic (As) and lead (Pb) are common soil contaminants, environmentally hazardous, and are threats to public health. Addition of soluble phosphate is known to be effective for in situ remediation of Pb-contaminated soils, but phosphate additions displace As from the soil particles and increase As concentration in soil solution. This study examined the dual use of iron (Fe) and phosphorus (P) amendments to soil, highly contaminated with As and Pb. The test soil originated from a former smelter site in Utah with As and Pb concentrations of 66,400 mg Pb kg-1 and 7,520 mg As kg-1 . Goethite, ferrihydrite, and iron-rich water treatment residuals (Fe-WTR) were added to immobilize As, and soluble P was added to reduce Pb lability. The Fe amendments were added in Fe:As mole ratios ranging from 1:1 to 1:10, and P was added in P:Pb mole ratios from 0.2:1 to 5:1. Fe-WTR was found to be the most effective Fe amendment. When Fe-WTR and P were added simultaneously, the P concentrations required to immobilize Pb resulted in increased mobilization of As, even when Fe-WTR were added at 10:1 Fe:As. However, when P was added first at 5:1 P:Pb, incubated for one week, and then amended with Fe-WTR at 10:1 Fe:As, both Pb and As were significantly immobilized. The proposed process is a practical remediation approach to soils co-contaminated with Pb and As while encouraging re-use of Fe-WTR as a sustainable amendment. This article is protected by copyright. All rights reserved.
Increasing organic rice production in Texas can have mixed impacts on soil health. • Rice grain y... more Increasing organic rice production in Texas can have mixed impacts on soil health. • Rice grain yields were reduced in organic systems. • Soil methane emissions increased in organic systems. • DNDC simulations predicted organic fertilizer impacts on yields and soil emissions. • Difference in organic and conventional fertilized grain yields diminished over time.
AbstractSmectite-bearing, expansive clayey soils are common in many areas of Texas, causing damag... more AbstractSmectite-bearing, expansive clayey soils are common in many areas of Texas, causing damage to pavements and building foundations by cyclic shrinking and swelling. The mechanism of shrinking...
The purpose of this study was to assess the impact of non-traditional water irrigation on the che... more The purpose of this study was to assess the impact of non-traditional water irrigation on the chemical and mineralogical properties of the calcareous clayey Angelo soil from West Texas. The exponential rise in population and climate change is leading to further increase in freshwater (FW) depletion, treated wastewater (TWW) and brackish groundwater (BGW) thus offer the possibility of attractive alternative water resources for irrigated agriculture. To address the differences between TWW and BGW, water samples were collected and analyzed. The water samples were analyzed for salt and nutrient content. Soil samples from three horizons (Ap, A, and B) were obtained from three different fields: Rainfed (RF), BGW irrigated, and TWW irrigated. Soil was analyzed for texture, salinity, sodicity, and carbon content. Clay mineralogy of the three different fields was analyzed using the B-horizons. TWW is slightly saline compared to the moderately saline BGW. Although, the exchangeable sodium percentage (ESP), sodium adsorption ratio (SAR), and electroconductivity (EC) have marginally increased compared to RF, however all the values of interest (SAR<13, ESP<15, pH<8.5, and EC<4) were low indicating no sodicity nor salinity problems. Smectite, illite, and kaolinite were identified in the three B-horizon samples by XRD. Overall, there was no major changes in the soil observed, which deems TWW and BGW as viable replacements for FW in arid and semi-arid regions. iii DEDICATION I dedicate this work to my parents, significant other, family, and my friends for all their encouragement and support throughout my journey to obtain this degree. thank Mr. Mathew Wilde for allowing access to his land for soil and water sampling. Without his permission and cooperation, this research would not have been possible. I would like to acknowledge WEF Nexus Research Group members and their support and help. Thanks also go to my friends and colleagues and the department faculty and staff for making my time at Texas A&M University a great experience. Finally, thanks to my parents for their encouragement and to my significant other for her patience, support, and love.
Public reporting burden for the collection of information is estimated to average 1 hour per resp... more Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
Plant physiology and biochemistry : PPB / Societe francaise de physiologie vegetale, Jan 25, 2015
Cerium oxide nanoparticles (CeO2 NP) are a common component of many commercial products. Due to t... more Cerium oxide nanoparticles (CeO2 NP) are a common component of many commercial products. Due to the general concerns over the potential toxicity of engineered nanoparticles (ENPs), the phytotoxicity and in planta accumulation of CeO2 NPs have been broadly investigated. However, most previous studies were conducted in hydroponic systems and with grain crops. For a few studies performed with soil grown plants, the impact of soil properties on the fate and transport of CeO2 NPs was generally ignored even though numerous previous studies indicate that soil properties play a critical role in the fate and transport of environmental pollutants. The objectives of this study were to evaluate the soil fractionation and bioavailability of CeO2 NPs to Raphanus sativus L (radish) in two soil types. Our results showed that the silty loam contained slightly higher exchangeable fraction (F1) of cerium element than did loamy sand soil, but significantly lower reducible (F2) and oxidizable (F3) fract...
Functions of Natural Organic Matter in Changing Environment, 2012
The objective of this study was to examine ryegrass for phytoremediation of 2,4-DCB (a polychlori... more The objective of this study was to examine ryegrass for phytoremediation of 2,4-DCB (a polychlorinated biphenyl congener)-contaminated soils. A pot experiment was conducted for 45 days using two soils (a Mollisol and an Alfisol) in greenhouse. Results showed that dissipation rates in both rhizosphere soils were significantly higher than those in controls, which were not spiked with 2,4-DCB. 2,4-DCB concentration in rhizospheric soils decreased from the initial concentration 30 ± 0.5 mg·kg−1to 3.42 mg·kg−1 in the Mollisols, as compared to 13.94 mg·kg−1 in non-rhizospheric soils. Also, a significant rhizospheric effect was observed in the Alfisols soil. A bioconcentration factor (BCF) was used to indicate the ability of ryegrass to tolerate and accumulate xenobiotics. Results showed that the BCF in shoots and roots of plants varied (P < 0.05). BCF in roots and shoots were 0.149 and 0.050 in the Mollisol soil and 0.122 and 0.027 in the Alfisol, respectively.
Proceedings of the Water Environment Federation, 2009
Visual MINTEQ (v. 2.53) was adopted to study the equlibria of potential fouling minerals in UV di... more Visual MINTEQ (v. 2.53) was adopted to study the equlibria of potential fouling minerals in UV disinfection applications. Data from fouling experiments included description of water chemistry, including the concentrations of common metal ions and ligands in solution, water temperature, pH, redox potential, hardness, etc. The modeling results were used as a template to identify likely precipitating minerals in the fouling process. Redox effect was examined for the precipitation of iron and manganese. The modeling results suggested that the hydrolytic form of Fe(III) is the dominant mineral that has potential to precipitate due to its oversaturated status. For experiments manganese precipitation appeared likely, the highly-oxidized Mn-containing minerals, such as MnO 2 , MnPO 4 , and MnOOH, appeared to have the greatest potential to precipitate. Among these forms, the saturation index of MnO 2 was usually the largest.
Petroleum contamination poses a significant threat to environmental ecosystems worldwide. Phytore... more Petroleum contamination poses a significant threat to environmental ecosystems worldwide. Phytoremediation can be used to enhance degradation of petroleum contaminants in soil. However, selection of plants for phytoremediation has proven to be complicated. This research examines the heritability of the alfalfa cultivar Riley for phytoremediation based on parental total petroleum hydrocarbon (TPH) degradation after twelve months of growth. Traits other than degradation potential, such as root and shoot yield, height, and maturity, were examined for use as selection traits. Riley showed moderate to low heritability that suggests the possibility of breeding for phytoremediation efficiency. In addition, root and shoot yield were found to correlate to TPH degradation. Crosses in which the female parent was typically associated with low TPH dissipation yielded progeny that were high efficiency TPH degraders.
Soil and Sediment Contamination: An International Journal, 2001
Phenanthrene biodegradation was investigated at different soil water contents [0.11, 0.22, 0.33, ... more Phenanthrene biodegradation was investigated at different soil water contents [0.11, 0.22, 0.33, 0.44 g H2O (g soil)− 1] to determine the effects of water availability on biodegradation rate. A subsurface horizon of Kennebec silty loam soil was used in this study.[9-14C] ...
Small arms firing ranges (SAFRs) contain a mixed amount of bullets and bullet fragments accumulat... more Small arms firing ranges (SAFRs) contain a mixed amount of bullets and bullet fragments accumulated throughout their designed lifetime. Lead-antimony (Pb-Sb) alloy copper (Cu) jacketed bullets are a common modern ammunition used at SAFRs. The impact of bullets with berm material (i.e., soil) generates a heterogeneous distribution of bullets and bullet fragments in the surrounding soil. As bullets and bullet fragments corrode in the berm soil, the migration potential for antimony compared to other metals is quite high. The goal of this study was to evaluate the spatial Sb migration potential from an SAFR as compared to lead, copper, and zinc (Zn) migration from the same SAFR. Berm soil samples were collected along with surface and ground water samples for a preliminary investigation of the Sb migration from an active SAFR. In addition, different aqueous sample preservation techniques were used and evaluated. Soil sample analysis results show the presence of the metals (i.e., Pb, Sb, Cu, and Zn) in the range floor soil samples, indicating the migration of these metals from the berm to the range floor. The groundwater samples indicate that Sb was migrating from the SAFR more readily than the other metals based on the concentration of Sb in the monitoring well farthest from the SAFR berm.
A column experiment was conducted to determine the impact of soil cover and plants on heavy metal... more A column experiment was conducted to determine the impact of soil cover and plants on heavy metal leaching from mine railings and heavy metal contaminated soil. Columns made of PVC were constructed with 30 cm subsoil covered by 30 cm of mine tailings followed by 0, 30, or 60 cm of dean topsoil. Two grasses, tall fescue (Festuca arundinacea Schreb.) and big bluestem (Andropogon gerardii), were grown in the columns. The columns were leached at a slow rate for 1 yr with a 0.001 M CaCl2 solution under unsaturated conditions. The presence of both tall fescue and big bluestem increased Zn and Cd concentrations in the leachate. Lead concentrations in leachates were not affected by the presence of plants. Although plants generally reduced the total amount of water leached, total mass of Zn and Cd leached generally was not impacted by plants. Total mass of Pb leached was positively correlated (r = 0.9) with total leachate collected from each column. Covering the mine tailings with 60 cm of topsoil (with or without vegetation) increased the mass of Zn and Cd leached relative to no topsoil. When the subsoil was absent, Zn and Cd leaching increased by as much as 20-fold, verifying the ability of soil to act as a sink for metals. Mine tailing remediation by establishing vegetation can reduce Pb movement but may enhance short-term Cd and Zn leaching. However, the changes were relatively small and do not outweigh the benefits of using vegetation in mine tailings reclamation.
Plant-bacterial combinations can increase contaminant degradation in the rhizosphere, but the rol... more Plant-bacterial combinations can increase contaminant degradation in the rhizosphere, but the role played by indigenous root-associated bacteria during plant growth in contaminated soils is unclear. The purpose of this study was to determine if plants had the ability to selectively enhance the prevalence of endophytes containing pollutant catabolic genes in unrelated environments contaminated with different pollutants. At petroleum hydrocarbon contaminated sites, two genes encoding hydrocarbon degradation, alkane monooxygenase ( alkB ) and naphthalene dioxygenase ( ndoB ), were two and four times more prevalent in bacteria extracted from the root interior (endophytic) than from the bulk soil and sediment, respectively. In field sites contaminated with nitroaromatics, two genes encoding nitrotoluene degradation, 2-nitrotoluene reductase ( ntdAa ) and nitrotoluene monooxygenase ( ntnM ), were 7 to 14 times more prevalent in endophytic bacteria. The addition of petroleum to sediment do...
Contamination of soil by hazardous substances poses a significant threat to human, environmental,... more Contamination of soil by hazardous substances poses a significant threat to human, environmental, and ecological health. Cleanup of the contaminants using destructive, invasive technologies has proven to be expensive and more importantly, often damaging to the natural resource properties of the soil, sediment, or aquifer. Phytoremediation is defined as the cleanup of contaminated sites using plants. There has been evidence of enhanced polycyclic aromatic hydrocarbons (PAHs) degradation in rhizosphere soils for a limited number of plants. However, research focusing on the degradation of PAHs in the rhizosphere of trees is lacking. The objective of this study was to assess the potential use of trees to enhance degradation of PAHs located in manufactured gas plant-impacted soils. In greenhouse studies with intact soil cores, acenaphthene, anthracene, fluoranthene, naphthalene, and phenanthrene decreased significantly (p &amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) in green ash (Fraxinus pennsylvanica Marshall) and hybrid poplar (Populus deltoides x P. nigra DN 34) phytoremediation treatments when compared to the unplanted soil control. Increases in PAH microbial degraders in rhizosphere soil were observed when compared to unvegetated soil controls. In addition, the rate of degradation or biotransformation of PAHs was greatest for soils with black willow (Salix nigra Marshall), followed by poplar, ash, and the unvegetated controls. These results support the hypothesis that a variety of plants can enhance the degradation of target PAHs in soil.
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