| Studying the sources, fates, and transport pathways of anthropogenic trace elements under the influence of rapid urban expansion and growth is one of the major themes in environmental research. Because of the potential toxicity of trace elements, it is important to study them in an urban setting, especially in one that has changed from a small town to a populous city within only decades. Based on this, I carried out a trace elemental study in the soils of Maricopa County, AZ, with samples from 200 sites across three major land-use types: urban, desert, and agriculture. First, I mapped the distributions of twenty one elements in both the surface (10 cm) and lower (10 to 30 cm) soil with GIS, grouped the elements with statistical analysis, tested the effects of traffic emissions with roadside soil depth profiles, and found that most elements come from natural geological formation or non-point anthropogenic sources. Second, I studied the accumulation of arsenic in old agricultural land through irrigating with arsenic containing natural water. I used batch experiments to quantify the arsenic adsorption capacity in the local desert soil, and illustrated the capacity of arsenic adsorption on the local soil, as well as factors that influence the accumulation of arsenic through irrigation. Third, I tested the lead isotope ratios 207Pb/206Pb and 208Pb/206Pb in my 200 soil samples, and found that urban lead in Phoenix is more likely to come from historical lead-based paint than traffic or industrial emissions. Lastly, I correlated the surface lead distribution data with the socioeconomic factors of the local population, through regression and spatial autocorrelation, and found inequitable distributions of lead among the non-white and low-income populations. |
