Evolution of Eco-Environment and Carbon Burial of Critical Zones in Xiantao Area, Hubei Province

Lakes in Xiantao area are continuously shrinking, while the eutrophication level and the heavy metal contents of wetland sediments rising, relatively, the ecosystem of the lakes in Jianghan plain weakening increasingly. Enhancing the studies on the eco-environment evolution, analyzing the effects of human activities and eutrophication on lake ecosystem, and discussing the rules of carbon burials in different sedimentary environments are particularly important. Based on the Quaternary geological survey of the key regions in Jianghan plain, we collected and determined sediment samples from 16 key sites in 8 different sedimentary environments (including large fisheries, small fish ponds, vadum, lakes, paddy fields, spillway, dry fields and terrace of Hanjiang River). The total organic carbon(TOC) contents of the surface soils show that the level of organic carbon in the southern area (lake sedimentary environment) is higher than that in the northern region (fluvial and pluvial environment causes), which is consitent with human activity intensity and eutrophication level indicated by pigment, total nitrogen(TN). Carbon burials of shallow core sediments are consistent with the eutrophication level indicated by pigment showing a rising tendency. The rates of carbon burials are various in different sedimentary environments. The highest is in large fisheries (77.71 g·m^-2·a^-1) while the lowest is in the terrace of Hanjiang River (3.61 g·m^-2·a^-1). Our study indicates that the carbon aggregation function of lakes is constantly enhancing, and it has important significance to study the carbon cycle of the critical zones in Jianghan plain.