Fate and transport of 1278-TCDD, 1378-TCDD, and 1478-TCDD in soil-water systems.
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-(14)C]-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.
Fan
Zhaosheng
Z
Department of Soil Science, North Dakota State University, Fargo, ND 58105, USA.
Casey
Francis X M
FX
Larsen
Gerald L
GL
Hakk
Heldur
H
D000327:Adsorption; D007536:Isomerism; D007700:Kinetics; D008956:Models, Chemical; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000032:analysis; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000032:analysis*; D014867:Water / Q000032:analysis*
D000072317:Polychlorinated Dibenzodioxins; D012987:Soil; D012989:Soil Pollutants; D014867:Water; C445379:1,2,7,8-tetrachlorodibenzo-p-dioxin; C078329:1,3,7,8-tetrachlorodibenzo-4-dioxin