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Assessment of heavy metal contamination and restoration of soil food web structural complexity in urban vacant lots in two post-industrial cities

Sharma, Kuhuk
http://rave.ohiolink.edu/etdc/view?acc_num=osu1406232323

Abstract Details

2014, Doctor of Philosophy, Ohio State University, Environmental Science.
Increasing proportions of vacant land parcels in post-industrial cities is a growing concern due to decreasing land value and increasing maintenance externalities. Utilizing this urban vacant land for growing food crops can promote local self-reliance and access to healthy food; specifically in low income disadvantaged neighborhoods. However, impact of heavy metal contaminants on soil quality, is a major concern for urban agriculture. Additionally, health of vacant lot soil also depends on the structural bio-diversity of the below ground soil food web. Hence the specific objectives of this research were (i) to assess the level of soil heavy metal concentrations in two post-industrial cities and determine their potential human health risk (Chapter 2); (ii) to evaluate the relationship between heavy metal concentrations and the structure and function of the soil food web using nematodes as surrogates of soil microbial community (Chapter 3); (iii) to test a novel approach of transplantation of an intact soil core to reconstruct the structural complexity of a disturbed soil food web and restore its level of multi trophic interactions to a pre-disturbance level (Chapter 4) (iv) finally, to re-construct the soil food web in urban vacant lot using intact soil cores from relatively undisturbed forest soil, and assess the survival of the introduced nematode species under organic matter with different C:N ratios (Chapter 4) We determined the extent of soil Pb, Cd, Zn, As and Cr concentrations in 43 vacant lots in two disadvantaged neighborhoods in Hough (Cleveland) and Weinland Park (Columbus), Ohio. Results showed that compared to the Ecological Soil Screening levels (Eco SSL) for human ingestion of soil, only 6% of the lots in Weinland Park and 53% in Hough neighborhood had Pb concentrations above the Eco SSL of 400 mg Pb/kg soil. Also, all the studied sites exceeded the Eco SSL value of 0.4 mg As/kg soil; however, soil As concentration in 94% of the lots in Weinland Park and 90% of the lots in Hough were not elevated beyond the natural background concentration in Franklin and Cuyahoga counties respectively. Associations with soil nematode community showed that the sensitive, higher trophic level omnivorous and predatory nematodes were found in low abundance indicating the disturbed nature of the urban soil food webs. Multiple regression analysis revealed a combination of As, Cd, Cr, soil texture and organic matter as significant variables whose interactions affected the abundance of nematodes and the community indices such as channel index, enrichment index and structure index. We observed distinct associations between metals, soil properties and nematode parameters in the two neighborhoods. All the studied vacant lots were not contaminated and metal concentration was not uniform across a given lot. To restore soil food web complexity in lots with little or no metal contamination, we tested a new approach of intact soil core transplantation and hypothesized that the missing nematode trophic guilds (along with associated soil organisms) can be reestablished using intact soil cores (9cm dia, 10cm deep) brought carefully from undisturbed forest. Laboratory and field analysis showed that higher trophic level nematodes can spread out of the transplanted cores and colonize a 2.25 m2 area within 2 weeks, with >50% increase in structure index within 3 weeks. Further analysis was carried out in vacant lots with metal concentrations lower than the USEPA established Soil Screening Levels (SSL). We tested the potential of organic amendments differing in their C:N ratios such as compost, peat and grass clippings to help in sustenance of the introduced nematode trophic guilds. Results showed that the use of organic compost and grass clippings as soil amendments supported maximum increase in abundance of higher trophic level nematodes and improvement of nematode community structure and maturity indices. Results from this study can help improve soil health in urban vacant lots, thus eliminating the need for large-scale topsoil replacements. This will pave the way for establishment of sustainable and safe urban food production systems.
Parwinder Grewal, Dr. (Advisor)
Larry Phelan, Dr. (Committee Member)
Nick Basta, Dr. (Committee Member)
Rafiq Islam, Dr. (Committee Member)
209 p.
Environmental Science
Soil health; heavy metal contamination; urban vacant lots; nematode community structure; soil food web health

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Citations

  • Sharma, K. (2014). Assessment of heavy metal contamination and restoration of soil food web structural complexity in urban vacant lots in two post-industrial cities [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406232323

    APA Style (7th edition)

  • Sharma, Kuhuk. Assessment of heavy metal contamination and restoration of soil food web structural complexity in urban vacant lots in two post-industrial cities. 2014. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1406232323.

    MLA Style (8th edition)

  • Sharma, Kuhuk. "Assessment of heavy metal contamination and restoration of soil food web structural complexity in urban vacant lots in two post-industrial cities." Doctoral dissertation, Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406232323

    Chicago Manual of Style (17th edition)

osu1406232323
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