科研之友
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摘要
Understanding Zn biogeochemical cycling is necessary for monitoring Zn supply for plants and life during land use con-version, which is critical for environmentally sustainable development. But little is known about how the conversion of paddy soil to abandoned land affects the Zn isotope signature. A comparative field observation was conducted in north-east Thailand to investigate the Zn isotope footprint of paddy soils and abandoned paddy soils (PL and NPL). Our results show that Zn (tau Znint : 0.04) slightly retains on PL, but is lost from NPL (tau Znint from - 0.81 to - 0.24) to the river during weathering. Compared to PL (A66Znparent-soil:-0.29 %o), more 66Zn isotopes might enter the river when rice cultivation ceases in NPL (A66Znparent-soil from -0.26 %o to -0.47 %o). Rice harvest and then root decay might result in heavy 66Zn isotopes accumulating at the topmost soil in PL (866Zn: 0.14 %o) and short-term abandonment (1-2 years) in paddy soils (NPL1 866Zn: 0.18 %o). The release of assimilated Zn, and then the high adsorption of Zn in the Fe-SOM-metal(loid)s ternary system positively contribute to the high [Zn] in PL, while this was not observed in NPL. Our findings provide a comprehensive insight into the Zn isotope signature in response to the conversion of land-use types, which is beneficial for understanding the terrestrial Zn geochemical cycle.
