内蒙古河套灌区盐碱土壤-地下水无机碳转移过程及其碳汇形成机制

It is a major challenge for human society that global warming caused by the increase in atmospheric CO2 concentration. Soil carbon sequestration has a great potential to retard the rise of atmospheric CO2 concentration, which has become a hot issue for scientists and governments of all countries. Saline-alkaline soil-ground water may become an important place for inorganic carbon sequestration. This project takes saline-alkaline soil-ground water as an object to be studied in the Yellow River Irrigation Area in Inner Mongolia. The saline-alkaline soil has the characteristics of wide area, excessive application of water and salt-leaching, High salt and alkali content and abundant reserves in groundwater for the area irrigated by Yellow River. The carbon processes of “saline-alkaline soil-ground water” are observed and studied on the soils with different saline-alkaline levels in the field. These work will be completed. 1. The change intensity, characteristics and response rule of inorganic carbon migration are clarified in saline-alkaline soil-ground water. 2. The key factor of the spatio-temporal differentiation of inorganic carbon is clearly defined in saline-alkaline soil-ground water. The formation mechanism of inorganic carbon sequestration is determined in saline -alkaline soil-ground water. 3. The inorganic carbon sequestration potential is evaluated in saline-alkaline soil-ground water. It is built for the principle of a win-win production system of CO2 emission reduction, the increased carbon sequestration of saline-alkaline soil-ground water, and realizing agricultural production. The results will provide data support and scientific basis for formulating the environmental diplomacy strategy of China's CO2 emission reduction and help to answer the international scientific questions about the mitigation of the greenhouse effect of different agricultural production methods.

大气CO2浓度升高引起全球变暖是当今人类社会面临的重大挑战。土壤碳汇功能具有减缓大气CO2浓度上升的较大潜力成为各国科学家及政府关注的热点问题，盐碱土壤-地下水可能成为重要的无机碳汇场所。本研究针对内蒙古引黄灌区“盐碱土壤面积广、大水漫灌洗盐、地下水盐碱含量高且储量多”的特点，以河套灌区盐碱土壤-地下水为研究对象，通过不同盐碱程度盐碱土壤-地下水碳过程原位观测和系统研究，将完成：1.阐明盐碱土壤-地下水无机碳迁移变化强度、特征及其响应规律；2.明确盐碱土壤-地下水无机碳时空分异的关键作用因子，确定盐碱土壤-地下水无机碳汇形成机制；3.评估盐碱土壤-地下水无机碳汇潜力，构建CO2减排，盐碱土壤-地下水增汇和实现农业生产双赢的生产体系原理。结果将有助于制定我国CO2减排环境外交策略提供数据支撑和科学依据，有助于回答国际关于不同农业生产方式减缓温室效应方面科学问题。

本研究针对内蒙古引黄灌区“盐碱土壤面积广、大水漫灌洗盐、地下水盐碱含量高且储量多”的特点，以河套灌区盐碱土壤-地下水为研究对象，通过碳同位素技术观测不同盐碱程度盐碱土壤-地下水碳过程，1.阐明盐碱土壤-地下水无机碳迁移变化强度、特征及其响应规律。1–2 m盐碱地下水中的溶解性无机碳（DIC）浓度低于5–25 m深处，土壤DIC出现向下迁移至地下水的趋势。盐碱土壤-地下水DIC浓度与pH值（R2=0.61，p<0.05）和碳酸盐饱和指数（R2=0.93，p<0.01）呈显著正相关。pH值较高的地下水含有较高的DIC浓度，具有较强碳汇潜力。盐碱地下水δ13CDIC值-21.22‰到-11.02‰，表明盐碱地下水DIC来源于土壤次生碳酸盐的溶解平衡和大气/盐碱土壤CO2。2.明确盐碱土壤-地下水无机碳时空分异的关键作用因子，确定盐碱土壤-地下水无机碳汇形成机制。土壤淋出液DIC与EC呈显著负相关(R2=0.86，p<0.01)，与pH呈显著正相关(R2=0.94，p<0.01)；土壤SDIC与土壤EC呈显著负相关(R2=0.38，p<0.05)，与土壤pH呈显著正相关(R2=0.81，p<0.01)；土壤SIC与土壤EC呈显著负相关(R2=0.34，p<0.05)，与土壤pH无明显相关性(R2=0.06，p>0.05)。pH和EC都是影响土壤及淋出液中无机碳含量的重要因素，pH对溶解性无机碳的影响高于EC，土壤难溶性无机碳主要受EC影响。在干旱盐碱区高风化土壤的淋溶过程中，无机碳一部分以DIC的形式随淋溶液淋出到地下水中，另一部分以SDIC和SIC的形式存在于土壤中。3.评估盐碱土壤-地下水无机碳汇潜力，内蒙古河套盆地浅层盐碱地下水碳封存可达到4.66×108 g C a-1，代表了生物地球化学循环中重要的碳汇潜力。研究结果为制定我国CO2减排环境外交策略提供数据支撑和科学依据，有助于回答国际关于不同盐碱程度土壤碳汇减排方面科学问题。发表学术论文7篇，其中，SCI收录2篇：CATENA、Environmental Science Processes & Impacts，EI收录2篇，CSCD收录3篇；培养硕士生5名；培养内蒙古自治区高等学校“青年科技英才”领军人才1名。