Identification of sources of Phoenix aerosol by positive matrix factorization

Chemical composition data for fine and coarse particles collected in Phoeni x, AZ, were analyzed using positive matrix factorization (PMF). The objecti ve was to identify the possible aerosol sources at the sampling site. PMF u ses estimates of the error in the data to provide optimum data point scalin g and permits a better treatment of missing and below-detection-limit value s. It also applies nonnegativity constraints to the factors. Two sets of fi ne particle samples were collected by different samplers. Each of the resul ting fine particle data sets was analyzed separately. For each fine particl e data set, eight factors were obtained, identified as (1) biomass burning characterized by high concentrations of organic carbon (OC), elemental carb on (EC), and K; (2) wood burning with high concentrations of Na, K, OC, and EC; (3) motor vehicles with high concentrations of OC and EC; (4) nonferro us smelting process characterized by Cu, Zn, As, and Pb; (5) heavy-duty die sel characterized by high EC, OC, and Mn; (6) sea-salt factor dominated by Na and Cl; (7) soil with high values for Al, Si, Ca, Ti, and Fe; and (8) se condary aerosol with SO4-2 and OC that may represent coal-fired power plant emissions; For the coarse particle samples, a five-factor model gave source profiles t hat are attributed to be (1) sea salt, (2) soil, (3) Fe source/motor vehicl e, (4) construction (high Ca), and (5) coal-fired power plant. Regression o f the PM mass against the factor scores was performed to estimate the mass contributions of the resolved sources. The ma for source's for the fine par ticles were motor vehicles, vegetation burning factors (biomass and wood bu rning), and coal-fired power plants. These sources contributed most of the fine aerosol mass by emitting carbonaceous particles, and they have higher contributions in winter. for the coarse particles, the major source contrib utions were soil and construction (high Ca). These sources also peaked in w inter.