PM{sub}2.5 Chemical Speciation Trends Network (STN): Examination of Geographic and Temporal Trends in Species Concentrations

摘要

With up to 230 field stations operating within the PM{sub}2.5 Chemical Speciation Trends Network (STN) program, the aggregated data have significant power for identifying national-scale trends and relationships. This paper will present observations based on over four years of speciated measurements collected by RTI for the STN program sponsored by EPA/OAQPS. Correlation analysis, mapping, and time series charting have been used to identify and characterize several significant sources of fine particulate contamination such as the following: elevated elements such as potassium and strontium as the result of Independence Day fireworks, and correlations between elements known to be used in fireworks; seasonally related levels of silicon and other crustal elements in the western US, presumably as a result of summertime dry conditions and sand storms; elevated elemental carbon (EC) measurements at certain sites known to be influenced by highway traffic, and correlations between EC and elements known to be associated with diesel and internal combustion such as bromine.