Long-term monitoring of atmospheric deposition in central Arizona-Phoenix: period 1998 to present

The aims of our study are to examine the magnitude and spatial variability in the concentration and flux of wet deposited NO3-N, NH4-N, DOC, PO4-P, Cl, SO4, H+, Ca, Mg, Na, K across the Central Arizona-Phoenix region, including the developed urban core and outlying desert. Also to examine patterns of coarse dry particulate deposition across the study area and provide some minimum estimates on levels of dry deposition of these ions. We were particularly interested to answer the question: 'To what extent are concentrations and fluxes of these ions enhanced at sites within the urban core relative to undeveloped desert sites upwind and downwind of the city'. Currently we operate eight wet-dry collectors located to form a transect running approximately W-E across the study area from outlying desert to the west, upwind of the prevailing synoptic wind direction, through agriculture to urban core sites, to two downwind sites in the desert to the east and northeast (map of bucket locations). Collectors are co-located at sites of Maricopa County or Arizona Department of Environmental Quality monitoring stations wherever possible.