灌溉熟化作用下天山北麓荒漠灰钙土中碳酸盐的赋存转移机制与碳汇响应

The latest research shows that the carbon sink weathering by carbon dioxide is increasing due to global warming and land use change, therefore researchers need to advance their understanding of carbonate carbon sink mechanism and potential under the surface environment. The soil in the northern part of the Tianshan Mountains is desert-sierozem soil, containing a lot of carbonate, which makes it a high-quality land reserve resource. In the past 40 years, a large amount of desert-sierozem soil has been reclaimed as farmland, and its soil-forming process dominated by natural factors have been converted into a process driven by human factors. Based on the previous study on the carbon pool of desert-sierozem soil, this project starts from the reality that the soil is highly utilized by human beings, which has led to the changes of soil physical and chemical properties as well as soil functions. With the theory and method of soil geochemistry and soil mineralogy applied, combined with the time series of irrigation and tillage, the soil sampling structure will be established from a point and a surface to a three dimensional space and the distribution, occurrence and transfer mechanism of soil carbonate under different ripening intensities will be investigated. Quantitative simulation and analysis will be performed to study the responsive effect of soil native minerals, clay minerals, organic matter, salt ions, soil nutrients and soil structure during irrigation as well as the processes coupling with soil secondary carbonation. This research will help deepen the scientific understanding of the dissolution / sedimentation balance, carbon sequestration mechanism and carbon sequestration potential of soil carbonate in arid area under irrigation ripening scenario.

最新相关研究显示，碳酸盐风化碳汇随着全球变暖和土地利用变化是持续增加的，人们应重新认识表生环境中碳酸盐的碳汇机制与潜力。荒漠灰钙土是天山北麓地带性土壤，富含碳酸盐，是优质土地后备资源。近40年来，大量的荒漠灰钙土被开垦为农田，其成土过程由自然因素主导转变为人为驱动为主。基于前期对荒漠灰钙土碳库的研究，本项目尝试从人类高强度利用导致土壤理化性质与土壤功能改变的现实出发，利用土壤地球化学、土壤矿物学等相关理论与方法，结合灌溉耕作的时间序列，对新垦农田设置由点及面到三维空间的多层次土壤取样结构，探讨不同熟化强度下土壤碳酸盐的分布特征、赋存形式及转移机制；定量模拟和分析灌溉熟化过程中土壤原生矿物、粘土矿物、有机质、盐基离子、土壤养分、土壤结构等的反馈效应与土壤次生碳酸盐化之间的耦合关系。本研究将有助于加深对灌溉熟化作用下干旱区土壤碳酸盐的溶解/沉积平衡与碳截存机制的科学理解与认识。

我国是碳中和签约国，致力于为应对全球气候变暖这个目前人类社会面临的最严峻环境问题做出贡献。土壤是陆地生态系统中容量最大的碳库，是大气CO2吸收、消耗、迁移、排放等各种过程共存的场所，因此，土壤既是重要的碳源，也同时具有强大的碳汇功能，是全球碳循环中的关键环节之一。人类活动特别是农业生产活动直接影响土壤的碳库平衡和汇/源效应，本项目基于“粮食安全”和“双碳目标”的实现这两大国家长期战略，采用土壤地球化学、土壤矿物学等相关理论与方法，探讨了人类不同开发利用强度下土壤碳酸盐的分布特征、赋存形式、转移机制以及土壤原生矿物、粘土矿物、有机质、盐基离子、土壤养分、土壤结构等的反馈效应。研究表明：1）干旱区成土过程中，土体内存在长期稳定的源自硅酸盐矿物风化的 Ca2+、Mg2+、Fe2+等阳离子供给，为土壤碳酸盐截存现代大气 CO2 提供了充分的物质基础；2）干旱区存在着有机-无机协同固碳机制，大气碳以重碳酸盐形式存在是土壤次生碳酸盐淀积和碳截存的关键环节之一。土壤中有机碳含量越高，生物风化过程越强烈，由土壤中有机质分解，根系呼吸等转移的大气CO2形成的重碳酸盐富 12C，重结晶后的土壤碳酸盐截存较多大气中的轻碳，因此，干旱区植被碳库的增加在扩大土壤有机碳汇的同时也会提高土壤无机碳汇效应；3）本项目执行期间，通过国际合作交流对中国新疆和美国亚利桑那两个不同干旱区气候变化与植被响应进行了对比研究，结果表明：气候变化给不同干旱区带来的压力和挑战不同，目前的气候变暖有利于促进新疆植被的生长，但不断上升的温度严重威胁了亚利桑那西南部的旱地生态系统，亚利桑那州超过18.8%的植被显著退化，尤其是灌丛植被。本项目通过大量的野外观测和实验室分析，获得各类基础数据7100个，相关研究可为新疆干旱区制定“双碳目标”行动方案提供数据支持。