No abstract

Traditional methods for the analysis of trace metals require particulate matter (PM) collected on specific filter substrates. In this paper, methods for elemental analysis of PM collected on substrates commonly used for organic analysis in air quality studies are developed. Polyurethane foam (PUF), polypropylene (PP), and quartz fiber (QF) substrates were first digested in a mixture of HNO(3)/HCl/HF/H(2)O(2) using a microwave digestion system and then analyzed for elements by inductively coupled plasma mass spectrometry. Filter blanks and recoveries for standard reference materials (SRMs) on these substrates were compared with a cellulose (CL) substrate, more commonly used for trace metal analysis in PM. The results show concentrations of filter blanks in the order of QF > PUF > PP > CL with a high variability in PUF and PP blanks relative to QF. Percent recovery of most elements from the SRMs on all substrates are within +/-20% of certified or reference values. QF substrates showed consistent blanks with a reproducibility better than +/-10% for the majority of elements. Therefore, QF substrates were applied to ambient PM collected in a variety of environments from pristine to polluted. Concentrations of field blanks for > or = 18 of 31 elements analyzed on a small section of QF substrate are < or = 25% of the amounts present in samples for urban atmospheres. Results suggest that QF used in a high-volume sampler can be a suitable substrate to quantify trace elements, in addition to organic species and hence reduce logistics and costs in air pollution studies.

As part of the Desert Southwest Coarse Particulate Matter Study which characterized the composition of fine and coarse particulate matter in Pinal County, AZ during 2010-2011, several source samples were collected from several different soil types to assist in source apportionment analysis of the study results. Soil types included native desert soils, agricultural soils (crop farming), dirt-road material adjacent to agricultural areas, paved road dusts, dirt road material from within and adjacent to a cattle feedlot, and material from an active cattle feedlot. Following laboratory resuspension of the soil, sizesegregated PM 2.5 and PM 10 fractions for each source type were collected on filters and characterized for mass, ions, OC, EC, and trace elements. While there are unique chemical compositions of soils in the region (e.g., high As and Sb) that reiterate the importance of using local source profiles (e.g., native soils) as compared to Upper Continental Crust or soil profiles from other regions in receptor modeling studies. The study also provides new insights into the impact of land-use modification on source emission profiles. Specifically, high OC and PO 4 3-are found in material representative of local cattle feedlot activities while elevated Cu, Sb and Zn are found from sources impacted by motor vehicle traffic. Results of the study indicate that the local native soil composition is only slightly modified by agricultural activities and this study provides the chemical composition of both native and agricultural soil for source apportionment studies in the Desert Southwest.

No abstract

No abstract

A year-long study was conducted in Pinal County, AZ, to characterize coarse (2.5 -10 µm aerodynamic diameter, AD) and fine (< 2.5 µm AD) particulate matter (PMc and PMf, respectively) to further understand spatial and temporal variations in ambient PM concentrations and composition in rural, arid environments. Measurements of PMc and PMf mass, ions, elements, and carbon concentrations at one-in-six day resolution were obtained at three sites within the region. Results from the summer of 2009 and specifically the local monsoon period are presented.The summer monsoon season (July -September) and associated rain and/or high wind events, has historically had the largest number of PM 10 NAAQS exceedances within a year. Rain events served to clean the atmosphere, decreasing PMc concentrations resulting in a more uniform spatial gradient among the sites. The monsoon period also is characterized by high wind events, increasing PMc mass concentrations, possibly due to increased local wind-driven soil erosion or transport. Two PM 10 NAAQS exceedances at the urban monitoring site were explained by high wind events and can likely be excluded from PM 10 compliance calculations as exceptional events. At the more rural Cowtown site, PM 10 NAAQS exceedances were more frequent, likely due to the impact from local dust sources.PM mass concentrations at the Cowtown site were typically higher than at the Pinal County Housing and Casa Grande sites. Crustal material was equal to 52-63% of the PMc mass concentration on average. High concentrations of phosphate and organic carbon found at the rural Cowtown were associated with local cattle feeding operations. A relatively high correlation between PMc and PMf (R 2 = 0.63) indicated that the lower tail of the coarse particle fraction often impacts the fine particle fraction, increasing the PMf concentrations. Therefore, reductions in PMc sources will likely also reduce PMf concentrations, which also are near the value of the 24-hr PM 2.5 NAAQS.Implications: In the desert southwest, summer monsoons are often associated with above average PM 10 (<10 µm AD) mass concentrations. Competing influences of monsoon rain and wind events showed that rain suppresses ambient concentrations while high wind increase them. In this region, the PMc fraction dominates PM 10 and crustal sources contribute 52-63% to local PMc mass concentrations on average. Cattle feedlot emissions are also an important source and a unique chemical signature was identified for this source. Observations suggest monsoon wind events alone cannot explain PM 10 NAAQS exceedances, thus requiring these values to remain in compliance calculations rather than being removed as exceptional wind events.

Phoenix, AZ, experiences high particulate matter (PM) episodes, especially in the wintertime. The spatial variation of the PM concentrations and resulting differences in exposure is of particular concern. In this study, PM 2.5 (PM with aerodynamic diameter Ͻ2.5 m) and PM 10 (PM with aerodynamic diameter Ͻ10 m) samples were collected simultaneously from the east and west sides of South Phoenix and at a control site in Tempe and analyzed for trace elements and bulk elemental and organic carbon.

The emission of particulate matter (PM 10 and PM 2.5 ) and ammonia (NH 3 ) by aeration processes at wastewater treatment plants (WWTPs) with and without odor control units was examined. Local concentrations of PM 2.5 , PM 10 , and NH 3 at the aeration basins were within urban ranges. Emission fluxes of NH 3 and PM 2.5 for a medium-sized WWTP were determined to be 136 g day À1 and 43 g day À1 , respectively, which are not substantial emission fluxes for urban environments. Odor control treatment using a granulated activated carbon bed reduced aerosol and NH 3 emissions substantially. Detection of sterols, in particular the fecal sterol campesterol, in the PM clearly demonstrates aerosolization of wastewater components in the aeration process. The presence of campesterol in PM 2.5 at a remote fenceline location in a WWTP facility illustrates that wastewater components are aerosolized in the fine PM fraction and transported beyond the facilities.Implications: Wastewater treatment plants are potential emission sources of particulate matter and gases. This study characterized particulate matter emissions from aeration basins and quantified emissions fluxes of particulate matter and NH 3 . While fine and coarse particles as well as NH 3 are being emitted, the overall emissions are small compared to other urban sources. However, fecal steroid presence in particles at the fence of a treatment plant demonstrates that wastewater material is getting aerosolized and transported beyond the facilities.