Dissertations, Theses, and Capstone Projects

Date of Degree

2-2025

Document Type

Dissertation

Degree Name

Ph.D.

Program

Earth & Environmental Sciences

Advisor

Zhongqi (Joshua) Cheng

Committee Members

Peter M Groffman

Theodore Muth

Richard K Shaw

Subject Categories

Earth Sciences | Environmental Sciences

Keywords

Urban Soil, Anthropogenic Soil, Ground Penetrating Radar, Electromagnetic Induction, Organic Carbon, Carbon Quality

Abstract

Urban soils are the foundation of urban ecosystems and play a vital role in long-term urban sustainability and resiliency. Accurate soil surveys of urban areas should be done at higher resolution since extensive human activities often result in urban soil being highly disturbed and spatially variable. Besides heterogeneity, one of the unique and challenging aspects of urban soil is the nature and properties of its organic carbon with a significant percentage of black carbon (a particulate product of incomplete combustion), which is less biologically active. Thus, in order to determine the ability of a soil to support biological activity and supply nutrients for plant growth, the properties of organic carbon need to be assessed. Conventional USDA-Natural Resources Conservation Service (NRCS) methods take considerable time for full characterization of collected soil samples. This limitation could be overcome by geophysical tools such as ground-penetrating radar (GPR) and electromagnetic induction (EMI), which can image large areas in a relatively short time without excavating the soil. These tools can map subsurface features and the degree of heterogeneity, which can provide useful information for representative site selection and sampling. How well these geophysical data correlate with site characteristics, however, has not yet been well established. In this research, 13 soil series covering a wide range of soil conditions were investigated across New York City using standard conventional soil survey methods with geophysical methods employed for 10 of them. From each site, samples were collected for laboratory determination of bulk density, pH and soluble salts, black carbon, cation exchange capacity, and plant available nutrients using standard protocols in the NRCS Field and Lab Analysis. Additionally, total carbon and nitrogen, C/N ratio, readily labile carbon and nitrogen, microbial biomass carbon and nitrogen were determined using standard laboratory protocols. Organic carbon quality was found to be strongly influenced by human-altered and human-transported (HAHT) materials, playing a critical role in the ability of urban soils to support ecological and environmental functions. Data from geophysical tools (i.e., GPR and EMI) were compared with field observations and laboratory results, including texture, consistence, salt content, bulk density, depth to the water table, and soil composition at each site, to map subsurface features. The results of this study revealed that GPR and EMI are capable of providing valuable interpretations of some common soil properties. These tools can play significant roles in complementing and enhancing traditional soil survey methods, within urban environments, where soils exhibit considerable variations over short distances, and survey encounters various challenges. The findings will help soil practitioners and decision-makers in protecting, conserving, and managing urban soils for an ever-expanding world population.

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