Progress 10/01/17 to 09/30/21
Outputs
Target Audience:Our research has the goal of improved understanding of the bioavailability of toxic metals, particularly lead (Pb), in soils, and possible methods of remediation of urban lead-contaminated soils to reduce human exposure to this toxic metal. Since regulators at present use total rather than bioavailable quantity of toxic metals in soils to set rules and guidelines, our results are directed at these agencies in order to provide a more scientific basis for such rules. In addition, our interactions with landowners and other community stakeholders (e.g., through gardening events and discussion forums in New York City (NYC), urban farming workshops in Buffalo, responding to information requests by email and phone) have indicated a need for comprehensive educational programs addressing diverse topics, including: 1) Training on site assessment for contaminants and soil sampling and testing protocols; 2) Information about and access to reliable, affordable, certified soil testing labs; 3) Simple guidelines for interpretation of soil test results that allow for site-specific considerations; 4) Assessment of contaminants in municipal compost and available soil/fill, and access to these materials; and 5) Possible liability issues or closure or avoidance of gardens if soil tests reveal contamination. All of these topics are informed by our past and ongoing research on the behavior of metal contaminants in urban garden soils. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project has provided the opportunity in 2019-2021 for two PhD-level graduate students from China, Yuting Zhou from Zhejiang University, and Xinxin Li from Shandong University, to each spend a year in our laboratory, learning new research methods and conducting research on chemical testing of soils and measuring bioavailability of toxic metals in soils. How have the results been disseminated to communities of interest?We have disseminated our research results in peer-reviewed publications. In addition we have provided interpretations of our results on soil remediation to reduce exposure to lead in less technical form to community stakeholders (gardeners, farmers, extension agents) through gardening events and discussion forums in New York City, Buffalo, Pittsburgh and other urban centers via urban farming workshops, and by responding to numerous information requests by email and phone calls. Fact sheets and workshops to address these topics continue to be developed to augment existing resources and are available at our newly developed Healthy Soils website : blogs.cornell.edu/healthysoils/ What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Our overall goal with this project is to improve our understanding of the mechanisms by which solubility and bioavailability of toxic metals in soils contaminated by past uses are controlled and influenced by soil physical, chemical and biological properties. Toxic heavy metals such as Pb are retained in soils by chemical adsorption on mineral surfaces, precipitation as carbonates, sulfates and phosphates, and complexation by natural organic polymers (humic materials) in the soil. The project research has focused on the chemical adsorption and precipitation reactions of Pb in soils and aqueous solutions in particular. Experiments were completed on the precipitation reactions of Pb with carbonate, sulfate and phosphate with mineral precipitates identified based upon Fourier Transform IR and X-ray diffraction methods. This research was designed to assess the stability of Pb phosphates, specifically hydroxy pyromorphite, in aqueous systems. The formation of this mineral in soils is believed to reduce the solubility, toxicity and bioavailability of Pb in soil and water systems. Additional experiments were conducted to study the bonding of Pb ions by natural and synthetic organic polymers. These experiments determined the effects of functional group type, pH and metal loading on the bonding affinity of Pb for these polymers. Several peer-review publications have resulted from these experiments. Experiments have also been completed in determining the importance that biological activity in soils can have in controlling Pb solubility and bioavailability. We have measured the "rhizosphere effect", that is, the impact that plant roots have on Pb solubility in the soil and potential for plant uptake. This involved extracting the soil water from Pb-contaminated soils that either do or do not have established plant populations. The results have now been published in the high-impact journal Environmental Pollution.
Publications
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Progress 10/01/19 to 09/30/20
Outputs
Target Audience:Our research has the goal of improved understanding of the bioavailability of toxic metals, particularly lead (Pb), in soils, and possible methods of remediation of urban lead-contaminated soils to reduce human exposure to this toxic metal. Since regulators at present use total rather than bioavailable quantity of toxic metals in soils to set rules and guidelines, our results are directed at these agencies in order to provide a more scientific basis for such rules. In addition, our interactions with landowners and other community stakeholders (e.g., through gardening events and discussion forums in New York City (NYC), urban farming workshops in Buffalo, responding to information requests by email and phone) have indicated a need for comprehensive educational programs addressing diverse topics, including: 1) Training on site assessment for contaminants and soil sampling and testing protocols; 2) Information about and access to reliable, affordable, certified soil testing labs; 3) Simple guidelines for interpretation of soil test results that allow for site-specific considerations; 4) Assessment of contaminants in municipal compost and available soil/fill, and access to these materials; and 5) Possible liability issues or closure or avoidance of gardens if soil tests reveal contamination. All of these topics are informed by our past and ongoing research on the behavior of metal contaminants in urban garden soils. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project has provided the opportunity in 2019 and 2020 for two PhD-level graduate students from China, Yuting Zhou from Zhejiang University, and Xinxin Li from Shandong University, to each spend a year in our laboratory, learning new research methods and conducting research on chemical testing of soils and measuring bioavailability of toxic metals in soils. How have the results been disseminated to communities of interest?We have disseminated our research results in peer-reviewed publications. In addition we have provided interpretations of our results on soil remediation to reduce exposure to lead in less technical form to community stakeholders (gardeners, farmers, extension agents) through gardening events and discussion forums in New York City, Buffalo, Pittsburgh and other urban centers via urban farming workshops, and by responding to numerous information requests by email and phone calls. Fact sheets and workshops to address these topics continue to be developed to augment existing resources and are available at our newly developed Healthy Soils website: blogs.cornell.edu/healthysoils/ What do you plan to do during the next reporting period to accomplish the goals?We have conducted a series of Pb adsorption experiments on organic polymers, including tannic acid, humic acid, and carboxymethylcellulose, in an effort to determine the types of functional groups in natural soil organic matter that are involved in Pb2+ bonding. The Pb ion-selective electrode was used in these studies to measure the free Pb2+ ions in solution at equilibrium with the organic solids. The resulting data will be analyzed in the coming year to calculate partitioning coefficients of Pb on organic polymers, and provide better understanding of the critical role that soil organic matter has in immobilizing and reducing bioavailability of Pb in soils. Experiments have also been completed in determining the importance that biological activity in soils can have in controlling Pb solubility and bioavailability. We have measured the "rhizosphere effect", that is, the impact that plant roots have on Pb solubility in the soil and potential for plant uptake. This involved extracting the soil water from Pb-contaminated soils that either do or do not have established plant populations. The results have been summarized in a manuscript that is now under review in the high-impact journal Environmental Pollution.
Impacts
What was accomplished under these goals?
Our overall goal with this project is to improve our understanding of the mechanisms by which solubility and bioavailability of toxic metals in soils contaminated by past uses are controlled and influenced by soil physical, chemical and biological properties. Toxic heavy metals such as Pb and Cd are retained in soils by one or more processes depending upon soil properties. These processes include chemical adsorption on mineral surfaces, precipitation as carbonates, sulfates and phophates, and complexation by natural organic polymers (humic materials) in the soil. In this particular funded period, our research focused on thechemical adsorption and precipitation reactions of Cd and Pb. Adsorption isotherms of both Pb and Cd over a very wide concentration range were curvilinear and were better modeled using the linearized Freundlich compared to the linearized Langmuir isotherm. Pb adsorbed more strongly than Cd on all soils, but soil pH, soil organic matter content, CEC and total Mn were positively correlated with the Pb and Cd bonding constants of the soils. Experiments were completed on the precipitation reactions of Pb with carbonate, sulfate and phosphate with mineral precipitates identified based upon Fourier Transform IR and X-ray diffraction methods. Finally, studies of the bonding of Pb ions by natural and synthetic organic polymers were conducted to determine the effects of functional group type, pH and metal loading on the bonding affinity for these polymers. We are in the process of finalizing manuscripts on the latter two studies for publication in peer-review journals.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2020
Citation:
Zhou, Y , S Sherpa, MB McBride. 2020. Pb and Cd chemisorption by acid mineral soils with variable Mn and organic matter contents. Geoderma Vol. ? 368,Article No. 114274
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Progress 10/01/18 to 09/30/19
Outputs
Target Audience:Our research is undertaken to better understand the bioavailability of toxic metals, particularly lead, in soils. Since regulators at present use total rather than bioavailable quantity of toxic metals in soils to set rules and guidelines, our results are directed at these agencies in order to provide a more scientific basis for such rules. In addition, our interactions with landowners and other community stakeholders (e.g., through gardening events and discussion forums in New York City, urban farming workshops in Buffalo, responding to information requests by email and phone) have indicated a need for comprehensive educational programs addressing diverse topics, including: 1) Training on site assessment for contaminants and soil sampling and testing protocols; 2) Information about and access to reliable, affordable, certified soil testing labs; 3) Simple guidelines for interpretation of soil test results that allow for site-specific considerations; 4) Assessment of contaminants in municipal compost and available soil/fill, and access to these materials; and 5) Possible liability issues or closure or avoidance of gardens if soil tests reveal contamination. All of these topics are informed by our past and ongoing research on the behavior of metal contaminants in urban garden soils. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project has provided the opportunity in 2018-2019 for two PhD-level graduate students from China, Yuting Zhou from Zhejiang University, and Xinxin Li from Shandong University, to each spend a year in our laboratory, learning new research methods and conducting research on chemical testing of soils and measuring bioavailability of toxic metals in soils. In addition, one Cornell undergraduate student was employed over the summer of 2019 to conduct experiments on the adsorption of Pb ions by natural organic polymers. How have the results been disseminated to communities of interest?We have disseminated our research results in peer-reviewed publications. In addition we have provided interpretations of our results in less technical form to community stakeholders (gardeners, farmers, extension agents) through gardening events and discussion forums in New York City, Buffalo, Pittsburgh and other urban centers via urban farming workshops, and by responding to numerous information requests by email and phone calls. Fact sheets and workshops to address these topics continue to be developed to augment existing resources and are available at our newly developed Healthy Soils website : blogs.cornell.edu/healthysoils/ What do you plan to do during the next reporting period to accomplish the goals?We are in the process of conducting a series of Pb adsorption experiments on organic polymers, including tannic acid, humic acid, and carboxymethylcellulose, in an effort to determine the types of functional groups in natural soil organic matter that are involved in Pb2+bonding. The Pb ion-selective electrode is being used in these studies to measure the free Pb2+ions in solution at equilibrium with the organic solids. The resulting data will be used to calculate partitioning coefficients of Pb on organic polymers, and provide better understanding of the critical role that soil organic matter has in immobilizing and reducing bioavailability of Pb in soils. Experiments are also underway in determining the importance of biological activity in soils in controlling Pb solubility and bioavailability. Specifically, we are measuring the "rhizosphere effect", that is, the impact that plant roots have on Pb solubility in the soil and potential for plant uptake. This involves extracting the soil water from Pb-contaminated soils that either do or do not have established plant populations.
Impacts
What was accomplished under these goals?
The overall goal is to better understand the mechanisms by which the solubility and bioavailability of toxic metals in soils contaminated by past uses are controlled and influenced by soil physical, chemical and biological properties. Research was completed on the specific adsorption of Pb and Cd by acid soils common in the Northeastern states.Adsorption isotherms of both Pb and Cd over a very wide concentration range were curvilinear and were better modeled using the linearized Freundlich compared to the linearized Langmuir isotherm. Pb adsorbed more strongly than Cd on all soils, but soil pH, soil organic matter content, CEC and total Mn were positively correlated with the Pb and Cd bonding constants of the soils. Work conducted in our laboratory had earlier shown that solid-phase Pb oxalate is sufficiently stable relative to Pb phosphates that it can limit Pb solubility in low pH (<5.5) environments, but also that oxalate complexes strongly enough with Pb ions to partially dissolve Pb phosphate and raise the solubility of Pb. We have now further investigated whether Pb solubility in soils and water could be limited by co-precipitation of Pb oxalate with Ca oxalate. Ca oxalate is a relatively insoluble and very commonly occurring biomineral in plants and soils. We found that sequestration of Pb into Ca-oxalate to form a solid solution substantially lowered Pb solubility relative to that of pure Pb oxalate to an extent inversely proportional to the Pb mole fraction for Pb mole fractions less than 0.1. Characterization of the Pb-Ca oxalate co-precipitates by X-ray diffraction, optical microscopy, and Fourier transform infrared spectroscopy revealed that the whewellite (Ca-oxalate monohydrate) structure was destabilized by substitution of small amounts of Pb into the lattice, and thus the formation of the Ca-oxalate dihydrate (weddellite) was favored over the monohydrate. At Pb mole fractions above 0.20, discrete crystallites of Pb-oxalatewere identified. These new findings imply that Pb-Ca oxalate co-precipitates in the presence of Ca could reduce the solubility of Pb in Pb-contaminated acid soils.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2019
Citation:
M.B. McBride, S. Kelch, M. Schmidt, Y. Zhou, L. Aristilde and C.E. Martinez. 2019. Lead solubility and mineral structures of co-precipitated lead-calcium oxalates. Environmental Science and Technology.
M.B. McBride and Y. Zhou. 2019. Cadmium and zinc bioaccumulation by Phytolacca americana from hydroponic media and contaminated soils. International Journal of Phytoremediation, 21, 1215-1224.
X.Y. Tang, R. Li, Y. Zheng and M.B. McBride. 2019. Health assessment of nickel-contaminated soils linked to chemical and biological characteristics. Soil Science Society of America Journal, 83, 614-623.
M.B. McBride, S.E. Kelch, M.P. Schmidt, S. Sherpa, C.E. Martinez and L. Aristilde. 2019. Oxlate-enhanced solubility of lead (Pb) in the presence of phosphate: pH control on mineral precipitation. Environmental Science- Processes and Impacts, 21, 738-747.
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Progress 10/01/17 to 09/30/18
Outputs
Target Audience:The need for affordable, locally-produced food continues to fuel interest in urban gardening and agriculture, as well as gardening efforts in a variety of residential and community spaces from backyards to schools to old farmlands across NYS. These activities help provide food security, economic savings, green space, opportunities for recreation and community building, reductions in environmental impacts of long-distance food transport and diverse benefits for public health. However, gardens and farms are often located on vacant lots and abandoned properties with a history of contamination, and can contain a number of soil chemicals that may contaminate fruits and vegetables and pose risks to human health. Our research and Extension project will address this challenge by providing science-based resources to help gardeners, farmers, and others maximize the many benefits of gardening and farming while minimizing risks from exposures to toxic metals in soils and vegetables. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project has provided the opportunity in 2017-2018 for one PhD-level graduate student (Yuting Zhou) from Zhejiang University, and one research scientist( Hou Meifang) from the Shanghai Institute of Technology, to spend a year in our laboratory, learning new research methods and conducting research on chemical testing of soils and measuring adsorption behavior of toxic metals such as lead and cadmium in soils. How have the results been disseminated to communities of interest?We have disseminated our research results in peer-reviewed publications. In addition we have provided interpretations of our results in less technical form to community stakeholders (gardeners, farmers, extension agents) through gardening events and discussion forums in New York City, Buffalo, Pittsburgh and other urban centers via urban farming workshops, and by responding to numerous information requests by email and phone calls. Fact sheets and workshops to address these topics continue to be developed to augment existing resources and are available at a newly developed Healthy Soils website : blogs.cornell.edu/healthysoils/ What do you plan to do during the next reporting period to accomplish the goals?We are in the process of conducting a series of laboratory experiments to explore in detail the processes by which the toxic heavy metals, lead (Pb) and cadmium (Cd), are adsorbed and made unavailable to plant or microbial uptake by soils. Strong adsorption in soils is attributable to the mineral (silicate clays, Fe and Mn oxides) and organic components of the soils. We will measure the chemical adsorption of the Pb2+ and Cd2+ ions on several soils of New York and Vermont containing very different levels of Fe, Mn and organic matter. Adsorption isotherms will be fit to the most appropriate mathematical function that describes the relationship between amount of metal adsorbed and the equilibrium concentration of metal in solution. The coefficients determined from these isotherms will allow us to determine which soil properties most strongly influence the affinity of these soils for Cd and Pb. We also will carry out a series of Pb adsorption experiments on organic polymers, including tannic acid, humic acid, and carboxymethylcellulose, in an effort to determine the types of functional groups in natural soil organic matter that are involved in Pb2+ bonding. The Pb ion-selective electrode will be used in these studies to measure the free Pb2+ ions in solution at equilibrium with the organic solids. The resulting data will be used to calculate partitioning coefficients of Pb on organic polymers, and provide better understanding of the critical role that soil organic matter has in immobilizing and reducing bioavailability of Pb in soils.
Impacts
What was accomplished under these goals?
Based on our field research in urban and non-urban environments, we were able to establish that the contamination of leafy vegetables by lead was almost exclusively due to soil particle attachment to the plant surfaces, a process that was greatly diminished by mulch or cover of soils. In addition, we found that thorough washing of these vegetables with water could remove a large fraction of this contamination, but the use of surfactants or vinegar solutions provided no additional benefit. Research on soil processes affecting bioavailability of Pbshowed that Pb phosphates were most effective in immobilizing Pb at soil pH above 6. At lower pH, low molecular weight organic acids are able to compete with phosphate for reaction with Pb, elevating Pb solubility. Thus, biological processes in soils are likely toalter the solubility of Pb phosphates, reducing the effectiveness of phosphate amendments to soils as a means to reduce plant availability. Although we continue to explore possibilities for phytoremediation of metal-contaminated soils, our most recent studies using pokeweed as a hyperaccumulator plant have shown far greater potential for Zn and Cd than for Pb phytoextraction from soils. The reason for this is largely the much lower solubility of Pb compared to Zn and Cd in soil solution. Even when the contaminated soils were acidified using oxalic acid, little Pb transfer into the pokeweed shoots occurred. We conclude that reports of significant phytoextraction of Pb from contaminated soils are exaggerated or simply based on faulty data.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Li F, Z Li, P Mao, YW Li, YX Li, MB McBride, JT Wu, P Zhuang. 2018. Heavy metal availability, bioaccessibility and leachability in contaminated soil: effects of pig manure and earthworms. Environmental Science and Pollution Research International. DOI:10.1007/s11356-018-2080-5.
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Zhang, S, J Song, Y Cheng and MB McBride. 2018. Derivation of regional risk screening values for cadmium-contaminated agricultural land in the Guizhou Plateau. Land Degrad Dev., 29, 2366-2377.
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Tang, X , MP Lim and MB McBride. 2018. Arsenic uptake by arugula (Eruca vesicaria, L.) cultivars as affected by phosphate availability. Chemosphere 195, 559-566.
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
Tai, YP, ZA Li and MB McBride. 2017. Dry cultivation enhances cadmium solubility in contaminated soils but minimizes cadmium accumulation in a leafy vegetable. Journal of Soils and Sediments 17, 2822-2830.
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Tang, X and MB McBride. 2018. Phytotoxicity and microbial respiration of Ni-spiked soils after field aging for 12 years. Environmental Toxicology and Chemistry 9999, 1-7.
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