中国西南岩溶水系统分布参数碳汇定量模型开发与应用

Scientists in China, particularly from the Institute of Karst Geology in Guilin of China, have been studying the impact of carbonate rock systems to the atmospheric CO2 since the early 1990s. Sponsored by the China Geological Survey, a nationwide study began in 2010 to monitor and estimate the total amount of atmospheric CO2 absorbed by the carbonate rock systems in China. Large amount of data including the weather, flow, water quality data, carbonate rock dissolution, and etc. have been collected from various representative locations in large river basins. The carbon sink by the carbonate rock systems in China have been estimated by several scientists, mostly using the statistical methods. Statistic models are known to be limited to existing and past scenarios and less capable for prediction and the best management practices. .The study aims to develop a physically-based carbon sink model for the typical karst flow system and karst river basins in southwest China. The carbon sink model will be based on an already developed coupled surface subsurface and conduit flow model and using the climatic, hydrological, geologic, and geographic information to model the physical, chemical and biological processes of carbon cycles in soils, karst groundwater system, and open channels and to quantify the carbon fluxes in each carbon pool and the total carbon sink for the river basin. Several sub-models will be developed to effectively and more accurately model the carbon fluxes in each pool. The sub-models include: 1) Carbon cycle sub-model in soils that model the organic and inorganic carbon; 2) Carbon cycle sub-model for caves; 3) Carbon cycle sub-model for groundwater matrix flows; 4) Carbon cycle sub-model for groundwater conduit flows; and 5) Carbon cycle sub-model for open channels (rivers and streams). Carbon cycle and equilibrium in the karst flow systems are temperature and CO2 partial dependent. Thus two other sub-models for the temperature associated with the flow system or each carbon pool and the CO2 concentration in soils will also be developed. .The hydrologic representative units in the physically based distributed carbon sink model are classified from a combination of land use and land cover for agricultural practices and vegetation covers, soil types, and topographies, which enable the model for the best management practice (BMP). The goal of BMP for carbon sink study is to find the best solution for the maximum atmospheric CO2 sink by carbonate rock system by simulating a series of management scenarios, for example, increasing vegetation cover or forestation areas.

碳酸岩系统对大气CO2的碳汇作用研究在我国已开展多年，2010年更大规模的展开。至今已取得了大量的观测数据和研究经验。碳汇研究的最终目的是估算碳平衡量，我国很多岩溶学专家已通过不同时期的观测数据用不同的方法估算碳汇量。本研究的特点是根据碳酸岩系统碳循环的特点，考虑碳循环在不同碳库中的物理、化学及生物过程与机理，以及水文、气象、地质、地理等影响因子建立分布参数性的具物理意义的碳汇定量模拟模型。在西南典型岩溶水系统耦合的地表地下水文水力学数值模拟系统的基础上，开发相应的碳循环定量（碳汇）模拟模型。根据碳循环规律，建立不同碳库的子模型。包括：土壤层有机无机碳循环子模型；岩溶洞穴碳循环子模型，岩溶水系统裂隙网络碳循环子模型，岩溶水管道地下河碳循环子模型，地表水体碳循环子模型等。开发岩溶水系统温度场模拟子模型和土壤CO2浓度模拟子模型,更有效地模拟碳循环。同时开发提高碳汇量的管理（BMP）模型。

中国西南岩溶地区生态环境日俱恶化，水资源短缺，地表地下水遭受污染，严重影响了人民的生活水平。水和土壤是岩溶区生态环境的两个重要组成部分，它们是岩溶区环境问题产生的基本载体，因此一个可靠的、结合土壤侵蚀模型的地表地下水水文水力学耦合模型是岩溶区水资源评估、开发和利用的必要工具。本项目紧紧围绕这两个因素开展了典型岩溶区水文模型和土壤侵蚀模型的建立工作，并在此基础上完善了之前的岩溶水资源管理系统（KWMS）软件。提出了一种对岩溶发育强烈区普遍适用的洼地集水区自动提取方法；建立了典型岩溶区桂江流域的RUSLE2的侵蚀模型；在水文模型和侵蚀模型的基础上，预测了在不同情景下的土壤有机碳的流失量，以及不同的土地利用结构下有机碳流失的敏感性。发表代表性学术论文两篇，多次参与国内外的学术交流活动。