urban brownfields to gardens: minimizing human exposure to lead and arsenic PDF
Preview urban brownfields to gardens: minimizing human exposure to lead and arsenic
URBAN BROWNFIELDS TO GARDENS: MINIMIZING HUMAN EXPOSURE TO LEAD AND ARSENIC by PHILLIP PETERSON DEFOE B.S., State University of New York-Plattsburgh, 2003 M.S., Tuskegee University, 2008 AN ABSTRACT OF A DISSERTATION submitted in partial fulfillment of the requirements for the degree DOCTOR OF PHILOSOPHY Department of Agronomy College of Agriculture KANSAS STATE UNIVERSITY Manhattan, Kansas 2014 ABSTRACT Urban gardens have been a popular re-use option in the transformation of brownfields— located in older industrialized cities and near peri-urban developments. They provide accessible, available, and affordable supplies of fresh fruits and vegetables, effectively reducing the enigma of “food deserts” across U.S. cities. However, direct (soil ingestion, inhalation) and indirect (soil-plant-human) human exposure concerns about real or perceived trace element contamination in urban soils persist due to previous use. Elevated lead (Pb) and/or arsenic (As) concentrations were found at two (Tacoma and Seattle, WA) urban gardens. The Tacoma site was contaminated with Pb (51 to 312 mg kg-1) and As (39 to 146 mg kg-1), whereas soil Pb at the Seattle site ranged from 506 to 2,022 mg kg-1, and As concentrations were < 20 mg kg-1. Experimental design at both sites was a randomized complete block with a split-plot arrangement (main plots: biosolids/compost vs. non-amended control; sub-plot: plant type). Tacoma site treatment included a Class A biosolids mix (TAGRO) with dolomite. The Seattle site was amended with Cedar-Grove Compost (CGC) plus dolomite. Efficacy of biosolids/compost amendment in reducing Pb and As concentrations was evaluated using root, leafy, and fruit vegetables. Soil Pb and As bioaccessibility were also evaluated. Food chain transfer of Pb and As in vegetables due to surface contamination of produce samples were evaluated on the basis of cleaning procedures. A laboratory incubation study and a controlled greenhouse experiment were conducted on soils collected from the Tacoma site. Effectiveness of addition of laboratory synthesized ferrihydrite (Fh: iron oxyhydroxide) and TAGRO mix, each alone or in combination were screened and tested on the Pb and As co-contaminated Tacoma soil. Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy studies of Pb and As were conducted on incubation study samples to understand treatment-induced Pb- and As- speciation changes. Dilution of soil Pb (10 to 23%) and As (12 to 25%) were observed for biosolids amendment at the Tacoma site, while CGC amendment resulted in 20 to 50% dilution in soil Pb at the Seattle site. Biosolids and CGC amendments reduced Pb concentrations in the vegetables by 50% to 71%. At both sites, Pb concentrations of root vegetables exceeded the MLs established by the Food and Agriculture Organization (FAO) and the World Health Organization (WHO). Arsenic concentrations in vegetables were below an estimated ML and were reduced by 46% to 80% when grown on biosolids amended soils. Laboratory cleaning further reduced Pb and As food-chain transfer in vegetables grown in contaminated urban soils. Laboratory incubation and greenhouse studies showed dissolution of Pb in TAGRO plus Fh, and Pb concentrations in Fh amendments were significantly lower than the other amendments. Bioaccessible Pb and As were low. Significant reductions in bioaccessible As were observed when soils were amended with both TAGRO and Fh. X-ray absorption spectroscopy results indicated that chloropyromorphite-like (stable Pb phosphates) phases were the most dominant Pb species. Arsenic existed mainly as As5+, scorodite (FeAsO ·2H O)-like species in all the 4 2 treatments ranging from about 60% (control) to about 70% (TAGRO plus ferrihydrite). Amendments utilizing both biosolids and Fh significantly reduce human exposure risks present in urban soils contaminated with Pb and As. URBAN BROWNFIELDS TO GARDENS: MINIMIZING HUMAN EXPOSURE TO LEAD AND ARSENIC by PHILLIP PETERSON DEFOE B.S., State University of New York-Plattsburgh, 2003 M.S., Tuskegee University, 2008 A DISSERTATION submitted in partial fulfillment of the requirements for the degree DOCTOR OF PHILOSOPY Department of Agronomy College of Agriculture KANSAS STATE UNIVERSITY Manhattan, Kansas 2014 Approved by: Major Professor Ganga M. Hettiarachchi Copyright PHILLIP PETERSON DEFOE 2014 ABSTRACT Urban gardens have been a popular re-use option in the transformation of brownfields— located in older industrialized cities and near peri-urban developments. They provide accessible, available, and affordable supplies of fresh fruits and vegetables, effectively reducing the enigma of “food deserts” across U.S. cities. However, direct (soil ingestion, inhalation) and indirect (soil-plant-human) human exposure concerns about real or perceived trace element contamination in urban soils persist due to previous use. Elevated lead (Pb) and/or arsenic (As) concentrations were found at two (Tacoma and Seattle, WA) urban gardens. The Tacoma site was contaminated with Pb (51 to 312 mg kg-1) and As (39 to 146 mg kg-1), whereas soil Pb at the Seattle site ranged from 506 to 2,022 mg kg-1, and As concentrations were < 20 mg kg-1. Experimental design at both sites was a randomized complete block with a split-plot arrangement (main plots: biosolids/compost vs. non-amended control; sub-plot: plant type). Tacoma site treatment included a Class A biosolids mix (TAGRO) with dolomite. The Seattle site was amended with Cedar-Grove Compost (CGC) plus dolomite. Efficacy of biosolids/compost amendment in reducing Pb and As concentrations was evaluated using root, leafy, and fruit vegetables. Soil Pb and As bioaccessibility were also evaluated. Food chain transfer of Pb and As in vegetables due to surface contamination of produce samples were evaluated on the basis of cleaning procedures. A laboratory incubation study and a controlled greenhouse experiment were conducted on soils collected from the Tacoma site. Effectiveness of addition of laboratory synthesized ferrihydrite (Fh: iron oxyhydroxide) and TAGRO mix, each alone or in combination were screened and tested on the Pb and As co-contaminated Tacoma soil. Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy studies of Pb and As were conducted on incubation study samples to understand treatment-induced Pb- and As- speciation changes. Dilution of soil Pb (10 to 23%) and As (12 to 25%) were observed for biosolids amendment at the Tacoma site, while CGC amendment resulted in 20 to 50% dilution in soil Pb at the Seattle site. Biosolids and CGC amendments reduced Pb concentrations in the vegetables by 50% to 71%. At both sites, Pb concentrations of root vegetables exceeded the MLs established by the Food and Agriculture Organization (FAO) and the World Health Organization (WHO). Arsenic concentrations in vegetables were below an estimated ML and were reduced by 46% to 80% when grown on biosolids amended soils. Laboratory cleaning further reduced Pb and As food-chain transfer in vegetables grown in contaminated urban soils. Laboratory incubation and greenhouse studies showed dissolution of Pb in TAGRO plus Fh, and Pb concentrations in Fh amendments were significantly lower than the other amendments. Bioaccessible Pb and As were low. Significant reductions in bioaccessible As were observed when soils were amended with both TAGRO and Fh. X-ray absorption spectroscopy results indicated that chloropyromorphite-like (stable Pb phosphates) phases were the most dominant Pb species. Arsenic existed mainly as As5+, scorodite (FeAsO ·2H O)-like species in all the 4 2 treatments ranging from about 60% (control) to about 70% (TAGRO plus ferrihydrite). Amendments utilizing both biosolids and Fh significantly reduce human exposure risks present in urban soils contaminated with Pb and As. TABLE OF CONTENTS List of Figures .............................................................................................................................. xiii List of Tables ............................................................................................................................... xvi Acknowledgements ..................................................................................................................... xvii Dedication .................................................................................................................................. xviii CHAPTER 1 - GENERAL INTRODUCTION .............................................................................. 1 CHAPTER 2 - LITERATURE REVIEW ..................................................................................... 13 Brownfields ............................................................................................................................... 13 Definition .............................................................................................................................. 13 Location and rise of brownfields .......................................................................................... 13 Deindustrialization and peri-urban developments ................................................................ 14 Reuse options for Brownfields .............................................................................................. 15 Economic benefits to brownfield revitalization .................................................................... 17 Brownfields to urban gardens ............................................................................................... 17 Gardening on urban brownfields........................................................................................... 18 Urban Soils ............................................................................................................................... 19 Urban soil definition ............................................................................................................. 19 Urban soil characteristics ...................................................................................................... 19 Lead .......................................................................................................................................... 20 Description and Occurrence .................................................................................................. 20 Properties and general uses ................................................................................................... 22 Lead-based paints.............................................................................................................. 22 Lead in gasoline ................................................................................................................ 23 Lead alloys ........................................................................................................................ 23 Lead toxicity and Human Health .......................................................................................... 24 Lead blood concentrations ................................................................................................ 25 Lead concentration in soils ................................................................................................... 26 Lead in soil environments ..................................................................................................... 26 Solubility and Stability of Pb minerals in soils ..................................................................... 27 Lead adsorption ..................................................................................................................... 29 viii Remediation of Soil Lead ......................................................................................................... 30 Lead Remediation Approaches in urban soils....................................................................... 30 Chemical stabilization of soil Pb using inorganic phosphate sources .................................. 31 In situ soil Pb stabilization using biosolids composts ........................................................... 32 ARSENIC ................................................................................................................................. 33 Description of arsenic ........................................................................................................... 33 Uses of arsenic ...................................................................................................................... 33 Arsenical Insecticides ....................................................................................................... 33 Arsenic in Chromated Copper Arsenate ........................................................................... 34 Secondary uses of Arsenic ................................................................................................ 34 Arsenic toxicity and human health ....................................................................................... 35 Arsenic concentration in soils ............................................................................................... 35 Arsenic in soil environments ................................................................................................ 36 Arsenic Sorption ................................................................................................................... 37 Effect of competing ions ................................................................................................... 38 Remediation of Soil Arsenic ..................................................................................................... 39 Arsenic Remediation ............................................................................................................. 39 In situ chemical immobilization........................................................................................ 40 Remediating soils contaminated with multi contaminants ................................................... 41 Bioavailability assessment of Lead and Arsenic................................................................... 42 Use of X-Ray Absorption Spectroscopy in Pb and As contaminated soils .......................... 44 LEAD AND ARSENIC CONCENTRATIONS IN PLANTS ................................................. 46 Lead concentration in plants ................................................................................................. 46 Arsenic concentration in plants ............................................................................................. 47 Assessing safe concentrations of Pb and As in crops ........................................................... 48 References ................................................................................................................................. 49 CHAPTER 3 - Safety of gardening on lead- and arsenic-contaminated brownfields .................. 72 Introduction ............................................................................................................................... 73 Materials and Methods .............................................................................................................. 78 Study Sites ............................................................................................................................ 78 Soil Sample Preparation and Laboratory Analyses............................................................... 83 ix Plant Sample Preparation and Laboratory Analyses ............................................................. 83 Bioaccessible Pb and As Measurement ................................................................................ 84 Data Analysis ........................................................................................................................ 85 Results and Discussion ............................................................................................................. 85 Lead in Tacoma soils ............................................................................................................ 86 Assessing safe Pb concentrations in Tacoma vegetables ...................................................... 87 Effect of cleaning on Tacoma vegetables ............................................................................. 89 Arsenic in Tacoma soils ........................................................................................................ 90 Assessing safe As concentrations in Tacoma vegetables...................................................... 91 Lead in Seattle soils .............................................................................................................. 92 Assessing safe Pb concentrations in Seattle vegetables ........................................................ 93 Effect of cleaning on Seattle vegetables ............................................................................... 93 Bioconcentration Factor ........................................................................................................ 94 Bioaccessible Pb and As ....................................................................................................... 96 Gardening Implications ......................................................................................................... 97 Conclusion ................................................................................................................................ 98 Acknowledgements ................................................................................................................... 99 References ............................................................................................................................... 105 CHAPTER 4 - Evaluation of In Situ Soil Amendments on Speciation and Bioaccessibility of Lead and Arsenic in an Urban Soil: An Incubation Study .................................................. 129 Abstract ................................................................................................................................... 130 Introduction ............................................................................................................................. 131 Materials and Methods ............................................................................................................ 135 Soil collection and processing ............................................................................................ 135 Experimental set-up ............................................................................................................ 136 Iron-oxide preparation......................................................................................................... 137 Treatments ........................................................................................................................... 138 Chemical analyses ............................................................................................................... 139 Determination of bioaccessible Pb ...................................................................................... 139 Determination of bioaccessible As ..................................................................................... 140 Chemical analysis of Pb and As .......................................................................................... 141 x
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