Seasonal quantification of Zn²⁺, Pb²⁺ and Cu²⁺ in urban dusts in a semiarid city in northwest Mexico

Arid and semi-arid cities are of especial interest due to the high amount of dusts that are deposited daily. Dust particles contain heavy metals that are considered potentially toxic elements (PTEs). High concentrations of PTEs in dust particles can result in risks to human health. Few studies have documented accumulation rates of atmospheric deposition and the influence of the North American Monsoon (NAM) in the movement of PTEs. Precipitation and urban runoff derived from the NAM play an important role in the deposition and resuspension of PTEs on urban surfaces. In this work, we quantified spatial and temporal patterns of Zn²⁺, Pb²⁺ and Cu²⁺ in an urban-rural gradient using ion-exchange resin (IER) collectors. Three monitoring periods were chosen and the samplings were carried out during the dry and rainy season in a city influenced by the NAM. Results from the IER collectors during the first monitoring period estimated 4.6 gZn²⁺ha⁻¹ 15 wk⁻¹, 3.3 gPb²⁺ha^-115 wk⁻¹ and 3.7 gCu²⁺ha^-115 wk⁻¹. During the second period, the deposition rates were 5.6 gZn²⁺ha⁻¹ 37 wk⁻¹, 1.1 gPb²⁺ha⁻¹ 37 wk⁻¹ and 1.5 gCu²⁺ha⁻¹ 37 wk⁻¹. Finally, in the third period 7.0 gZn²⁺ ha^-117 wk⁻¹, 0.6 gPb²⁺ha⁻¹ 17 wk⁻¹ and 0.9 gCu²⁺ha⁻¹ 17 wk⁻¹ were found. The central area of the city exhibited the highest deposition rates of PTEs influenced by precipitation and flood areas. Results of this work demonstrate the importance of the NAM in the movement of PTEs caused by precipitation and winds that promote the movement of particles in an urban area.