In Situ Measurements of Calcium Carbonate Dissolution Rates

CaCO3溶解是co2全球循环的重要组成部分。研究碳酸盐溶解速率的方法多种多样；室内实验、水柱原位溶解实验和模拟，与沉积物中%CaC03的观测分布进行比较。这项工作提供了使用底栖通量室的原位溶解速率的测量。直接测量方法是测量进入腔室的钙通量；间接测量将根据碱度、二氧化碳、氧气和硝酸盐通量的测量结果，为试验室内的碱度建立预算。模拟孔隙水碳酸盐离子浓度和溶解通量的数值模型将与观测数据进行比较，并用于估计碳酸盐溶解速率常数。模型的准确性和预测的速率常数将通过向腔水中注入酸和监测碱度、二氧化碳和钙的反应来检验。将利用孔隙水剖面增加的营养物质、氡和氧通量的测量来限制所研究地点发生的成岩反应。这项研究将在两个地区进行，包括一系列沉积物类型，加利福尼亚边境地区的盆地和东赤道太平洋的一个样带。

CaCO3 dissolution is an important component in the global cycling of C02. Various approaches have been used to study carbonate dissolution rates; laboratory experiments, in situ dissolution experiments in the water column and modeling to compare with observed distributions of %CaC03 in sediments. This work provides measurements of in situ dissolution rates using benthic flux chambers. Direct measurements will be made by measuring the flux of calcium into a chamber; indirect measurements will be made by establishing a budget for alkalinity in the chamber, based on measurements of alkalinity, C02, oxygen and nitrate fluxes. A numerical model to simulate pore water carbonate ion concentration and dissolution fluxes will be compared to observed data and used to estimate the bulk carbonate dissolution rate constant. The accuracy of the model and the predicted rate constants will be tested by injecting acid into the chamber water and monitoring the response of alkalinity, C02 and calcium. Measurements of nutrient, radon and oxygen fluxes, augmented by pore water profiles, will be used to constrain the diagenetic reactions occuring at the sites studied. This study will be conducted in two regions that include a range of sediment types, the basins of the California borderland and a transect in the Eastern equatorial Pacific.