Origins and Transport of Aquatic Dioxins in the Japanese Watershed: Soil Contamination, Land Use, and Soil Runoff Events

Abstract

Significant dioxins accumulations in Japanese forests and paddy fields have been observed, and surface soil runoff caused by rainfall and irrigation (i.e., soil puddling in paddy fields) results in dioxins input into the aquatic environment. An extensive investigation into the origins and transport of aquatic dioxins in the Yasu watershed, Japan was conducted considering surface soil contamination level, land use, and type of soil runoff event (i.e., irrigation runoff [IR], rainfall runoff [RR], and base flow [BF]). Combined use of the chemically activated luciferase expression (CALUX) assay together with high-resolution gas chromatography and high-resolution mass spectrometry (HRGC/HRMS) efficiently enabled this study, so that origins, transport, and dynamic movement of aquatic dioxins in the watershed were revealed. The particulate organic carbon normalized particulate-dioxins WHO-toxic equivalent (TEQ) concentration predicted by the CALUX assay (Spar) was found to be a convenient molecular marker to indicate origins of aquatic dioxins and clearly reflect surface soil contamination level, land use, and soil runoff events. Using experimental results and theoretical modeling, the annual loading amount of dioxins at the middle reach of the river was estimated to be 0.458 mg WHO-TEQ in 2004. More than 96.6% of the annual loading amount was attributed to RR and derived almost evenly from forest and paddy fields at the study location. Because the annual loading amount at the middle reach is less than 0.5% of the total dioxins accumulated in the upper basin, dioxins runoff from the Japanese watershed will continue. This study shows that the combined use of the bioassay with HRGC/HRMS can provide new insights into dioxins transport and fate in the environment.

Combination of a Fast Cleanup Procedure and a DR-CALUX® Bioassay for Dioxin Surveillance in Taiwanese Soils

“…The present study also showed a strong linear correlation between the dioxin levels obtained via the HRGC/HRMS and DR-CALUX ® . A Chinese study also found a similar correlation between the results of a chemical assay and bioassay (R = 0.87) [8], while several reports found a nonlinear relationship between the results of an in vitro bioassay and the results of the HRGC/HRMS method in dioxin-contaminated soils or sediments [25,27,32,48]. Not all the reports of AhR reporter gene assays including CALUX bioassay found a linear relationship between BEQs and TEQs.…”

Utility of an alternative method (to USEPA Method 1613) for analysis of priority persistent organic pollutants in soil from mixed industrial–suburban areas of Durban, South Africa

“…Analysis of PCDD/F in the soil is very challenging as concentrations are usually very low and this is exacerbated by run-off of particle-bound PCDD/Fs (Kanematsu et al, 2009a). As such, PCDD/Fs in soil are usually significantly determined in contaminated sites and run-off sites such as paddy fields (Huyen et al, 2015;Kanematsu et al, 2009aKanematsu et al, , 2009b. No PCDD/Fs could be detected above the LOQ at all nine sites, with only three PCDD/Fs being detected from the nine sites sampled.…”