Desorption kinetics of heavy metals in the gleyic layer of permafrost-affected soils in Arctic region assessed by geochemical fractionation and DGT/DIFS

An in-situ DGT (diffusive gradient in thin films) technique was deployed to gleyic-layer soils identified in the active layer of eight Arctic islands for the release-resupply processes of labile Cd, Zn, and Pb during the thawing season. The capability to maintain the initial soil concentration of these metals is highly dependent upon landscape elevation and soil texture, which determines the labile pool size of metals (K-dl). Cd and Zn had larger labile pools compared to Pb, indicating a larger resupply capacity for those metals. The rate at which the soil system can supply metal from solid phase to solution, represented as response time (T-c), of Zn and Cd was very short (<1 min), indicating rapid resupply. The longer T-c for Pb (similar to 5 min) was consistent with its slower desorption. In fluctuating permafrost-affected areas, the increasing elevation, which causes heterogeneity in soil texture, organic matter, and pH, resulted in lower Kdl and higher T-c for Cd, Zn, and Pb. Combined with BCR methods, labile Cd was associated with Fe oxides, Zn was associated with both Fe and Mn oxides, and Pb was associated with Mn oxides and also highly bound to micro-aggregates and dissolved organic matter.

Automated summary

The study found that in the active layer of Arctic islands, Cd and Zn had larger labile pools with greater resupply capacity, while Pb had a smaller resupply capacity. Cd and Zn could rapidly resupply, while Pb's resupply was slower. Changes in landscape elevation can affect soil texture and other conditions, thus impacting the resupply processes of Cd, Zn, and Pb.