Fate and transport of 1278-TCDD, 1378-TCDD, and 1478-TCDD in soil–water systems

• Published in: The Science of the total environment 2006-12, Vol.371 (1-3), p.323-333
• Main Authors: Fan, Zhaosheng, Casey, Francis X.M., Larsen, Gerald L., Hakk, Heldur
• Format: Article
• Language: English
• Subjects: Adsorption; Applied sciences; Batch experiment; Biological and physicochemical properties of pollutants. Interaction in the soil; Dioxin; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Isomerism; Kinetics; Miscible-displacement experiment; Models, Chemical; Pollution; Pollution, environment geology; Polychlorinated Dibenzodioxins - analogs & derivatives; Polychlorinated Dibenzodioxins - analysis; Soil; Soil - analysis; Soil and sediments pollution; Soil Pollutants - analysis; Sorption; Water - analysis
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2006.07.024

The most toxic dioxin is 2,3,7,8-tetrachlorodibenzo-p-dioxin (2378-TCDD), and obtaining comprehensive experimental data for this compound is challenging. However, several nontoxic isomers of 2378-TCDD exist, and can provide significant experimental evidence about this highly toxic dioxin. The goal of this study was to obtain experimental evidence for the fate and transport of 2378-TCDD in natural soils using its nontoxic isomers, 1,2,7,8-tetrachlorodibenzo-p-dioxin (1278-TCDD), 1,3,7,8-tetrachlorodibenzo-p-dioxin (1378-TCDD), and 1,4,7,8-tetrachlorodibenzo-p-dioxin (1478-TCDD). Batch sorption and miscible-displacement experiments, in various soils, were done using [4-14C]-radiolabeled TCDDs, while metabolism of these compounds was monitored. The results from the batch experiments indicated a high sorption affinity of all the TCDD isomers to soils and a strong correlation to organic matter (OM) content. 1278-TCDD, 1378-TCDD and 1478-TCDD (TCDDs) were more tightly bound to the soil with high OM than to the soil with low OM; however, it took a longer contact time to approach sorption equilibrium of TCDDs in the soil with high OM. Miscible-displacement breakthrough curves indicated chemical nonequilibrium transport, where there was a rate-limited or kinetic sorption that was likely caused by OM. Combustion analyses of extracted soil from the soil columns showed that most TCDDs were adsorbed in the top 1–5 cm of the column. These column combustion results also showed that sorption was correlated to specific surface and soil depth, which suggested the possibility of colloidal transport.