Quantitative Speciation of Insoluble Chlorine in Environmental Solid Samples

Abstract

Since organically bound chlorine (organo-Cl) has been determined by different methods depending on samples and study fields, it has been difficult to compare organo-Cl in different environments. Here, we focused on Cl in water-insoluble fractions (insoluble Cl) and applied Cl K-edge X-ray absorption spectroscopy in conjunction with combustion ion chromatography. Quantitative speciation of insoluble Cl enabled us to compare the concentrations of Cl bonded with aromatic carbon (aromatic-Cl) and aliphatic carbon (aliphatic-Cl) as well as organo-Cl across different types of environmental solid samples (soils, particulate matter, dust, and ashes). The concentrations of organo-Cl in house dust and urban particulate matter exceeded those in forest soils, suggesting that house dust and urban particulate matter may be important pools of organochlorine compounds (OCs). Further, by studying representative samples with concentrations of some individual organochlorine compounds (OCs), we evaluated the mass balance of identified/unidentified organo-Cl. The percentages of identified Cl to organo-Cl were up to 1% in all samples evaluated, suggesting the ubiquitous presence of unidentified OCs. We also estimated the chemical forms of insoluble inorganic Cl and tested the plots of organo-Cl versus total organic carbon to find the difference between samples. This work shows that the quantitative speciation of insoluble Cl is effective for cross-comparison of organo-Cl in different environmental solid samples.