Abstract
Freeze-thaw cycles are predicted to increase in cold temperate regions. The potential influence of the interactions of freeze-thaw cycles and agrochemicals on the release of Cd into river water is unknown. In this study, the interactions of freeze-thaw cycles and chlorpyrifos (FC) on Cd mobility in soils were analysed. The spatial variability of soil Cd under long-term intensive tillage in a freeze-thaw agro-system was also identified. The temporal variation of sediment Cd was detected based on analysis of the sediment geochemistry. The results showed that FC increased soil Cd mobility, with an increase of approximately 10% in CaCl2-extractable Cd. The increased mobile fractions of water-soluble and exchangeable Cd originated from the decreased fraction of Fe-Mn-oxide-associated Cd and organic matter-bound Cd. The total Cd content in the surface soil followed the zonally decreasing trend of dry land > paddy land > natural land. The Cd concentrations and sedimentation rates of the sediment core generally increased from 1943 to 2013 due to agricultural exploration and farmland irrigation system construction, indicating an increase of the Cd input flux into water. The results provide valuable information about the soil Cd transport response to the influence of climatic and anthropogenic factors in cold intensive agro-systems.
Highlights
Freeze-thaw cycles are predicted to increase in cold temperate regions
Soil humidity and temperature during the FT process can significantly affect soil activities[22], which strongly relate to Cd mobility[23], raising the question of how soil Cd losses respond when FT interacts with pesticides
There are some reports on soil Cd in regions with intensive agriculture that undergo FT, most of these studies were focused on the distribution and source identification[11]
Summary
Freeze-thaw cycles are predicted to increase in cold temperate regions. The potential influence of the interactions of freeze-thaw cycles and agrochemicals on the release of Cd into river water is unknown. Intensive agricultural activities can significantly decrease/increase Cd levels in soils by contributing to soil Cd accumulation and by directly impacting the soil physico-chemical properties through frequent ploughing and irrigation and the long-term application of agro-chemicals[4]. Pesticides have a notable impact on soil physico-chemical and microbial properties, such as soil pH, organic matter content and microbial activities[13]. These properties are key factors controlling soil Cd mobility[14] and vary with different land uses and pesticide levels[13,15]. The response difference in soil Cd mobility is in need of further analysis
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