Leaching dynamics of Zn, Pb and Cu in urban soils of a semi-arid region: A quantitative analysis.

In this study, we evaluate the leaching process and movement of PTEs once they reach the soil profile in urban soils in a semiarid city in northwest Mexico. Concentrations of Zn, Pb and Cu were quantified in an urban area using ion-exchange resin (IER) samplers. The IER is a passive method based on ion-exchange resins which allows sampling the transport of elements in macropores under unsaturated flow conditions. Samples were taken during three monitoring periods in a city influenced by the North American Monsoon (NAM). In the first monitoring period, the IER samplers showed leaching rates of 323.40 g Zn ha 15 wk, 361.90 g Pb ha15 wk, and 31.9 g Cu ha15 wk. The second period estimated 101.50 g Zn ha 37 wk, 58.20 g Pb ha 37 wk, and 20.00 g Cu ha 37 wk. Finally, in the third monitoring period concentrations of 141.90 g Zn ha17 wk, 32.10 g Pb ha 17 wk and 20.70 g Cu ha 17 wk were found. The highest leaching rate of PTEs was identified in the central area of the city and its surroundings, influenced mainly by flood areas and high surface runoff. The results of this study demonstrate the role that monsoon rains and runoff plays in the movement and distribution of PTEs in urban areas.