Atmospheric concentrations of PCDDs/PCDFs in Metropolitan Hartford Connecticut – Current levels and historical data

Abstract

The State of Connecticut (CT) has established an Ambient Air Quality Standard (AAQS) for PCDDs/PCDFs expressed as 2, 3, 7, 8-TCDD equivalents on an annualized basis of 1.0 pg/m 3 TEQ. This AAQS represents the maximum concentration permitted in ambient air from all known sources of PCDDs/PCDFs including background contributions. Atmospheric concentrations of PCDDs/PCDFs are currently monitored at a single site located in Hartford Connecticut. The data collected at this site are compared annually to the AAQS and ultimately used to demonstrate compliance with the AAQS. Samples were collected at Brainard Airport in Hartford, CT. during each of two winter sampling campaigns. These sampling campaigns that were conducted during the winter months of 2003–2004 and 2004–2005 each consisted of two 30day sampling events conducted in consecutive fashion. Results are provided for a total of eight (8) samples (reported as pairs) representing a total of four (4) 30 day sampling events. The mean concentration for the eight sample set of 0.013 pg/m 3 TEQ represents 1.4% of the CT DEP (Connecticut Department of Environmental Protection) AAQS guideline of 1.0 pg/m 3 TEQ. The highest values were observed during the January 20–February 18, 2005 sampling event (0.0193 and 0.0204) while the lowest TEQ values were observed during the December 21, 2004–January 20, 2005 sampling event (0.0124 and 0.0127). All measured values were significantly below the AAQS of 1.0 pg/m 3. The mean concentration for total PCDDs/PCDFs (Cl4-Cl8) measured in the eight sample set was 2.62 pg/m 3. This value is higher than concentrations measured historically at other locations in the State of Connecticut including urban settings such as Bridgeport, Wallingford and Hartford. The ambient PCDDs/PCDFs profile for the Brainard Airport Site is consistent with profiles typically attributable to combustion sources. The PCDDs/PCDFs profile is remarkably similar to profiles observed at the majority of sites used by the State of Connecticut during prior PCDDs/PCDFs monitoring programs. Congener profile analyses of samples collected in the Hartford Metropolitan area including most notably samples collected in consecutive winter seasons at the Brainard Airport site suggest a common set of source contributions to PCDDs/PCDFs levels measured in ambient air at these locations.