A Modeling Approach to Compare ΣPCB Concentrationsrnbetween Congener-Specific Analyses

摘要

Changes in analytical methods over time pose problems for assessing long-term trends in environmental contamination byrnPCBs. Congener-specific analyses vary widely in the number and identity of the 209 distinct PCB chemical configurationsrn(congeners) that are quantified, leading to inconsistencies among summed PCB concentrations (SPCB) reported by differentrnstudies. Here, we present a modeling approach using linear regression to compare SPCB concentrations derived fromrndifferent congener-specific analyses measuring different co-eluting groups. The approach can be used to develop a specificrnconversion model between any 2 sets of congener-specific analytical data from similar samples (similar matrix and geographicrnorigin). We demonstrate the method by developing a conversion model for an example data set that includes data from 2rndifferent analytical methods, a low resolution method quantifying 119 congeners and a high resolution method quantifying allrn209 congeners.We used the model to show that the 119-congener set captured most (93%) of the total PCB concentration (i.e.,rnS209PCB) in sediment and biological samples. SPCB concentrations estimated using the model closely matched measuredrnvalues (mean relative percent difference¼9.6). General applications of the modeling approach include 1) generatingrncomparable SPCB concentrations for samples that were analyzed for different congener sets; and 2) estimating thernproportional contribution of different congener sets to SPCB. This approach may be especially valuable for enablingrncomparison of long-term remediation monitoring results even as analytical methods change over time.