盐酸、温度、时间及粒径对海洋沉积物碳酸盐去除的影响

Effects of hydrochloric acid,temperature,time and grain size on carbonate removal from marine sediments in northern South China Sea

通过南海北部表层沉积物相同体积不同盐酸浓度(0.1和1.0 mol.L-1)、不同温度(23和60℃)、不同时间(6、12和24h)和不同颗粒粒径样品(<160μm和<32μm)的交叉条件实验,利用各条件实验后样品的总碳含量及稳定碳同位素组成分析结果,研究了盐酸、温度、时间及颗粒粒径对碳酸盐去除的影响。结果表明,从提高沉积物碳酸盐盐酸酸解反应速率和效率及获取稳定可靠的TOC、δ13C有机质等参数的角度出发:(1)盐酸用量及浓度是最重要的影响因素;(2)升高反应温度是不必要的,升高反应温度既会抑制反应的进行,又会导致盐酸浓度下降并加速有机质分解,从而对沉积物总有机碳含量及其δ13C等的准确分析产生不利影响;(3)在1.0 mol.L-1盐酸过量的条件下,碳酸盐的大量分解在6h之前已基本完成;(4)颗粒粒径愈小,愈有利于样品的均匀混合及反应的进行,相应的分析结果离散度亦愈小。

The effects of various factors such as hydrochloric acid, operating temperature and time, and grain size of sediments on the efficiency of carbonate removal from marine sediments sampled from the northern South China Sea were investigated and reported in this paper. By applying HCl with a uniform volume but different concentrations （0. 1 and 1.0 mol·L^-1）, different temperatures （23 and 60℃） and different grain sizes of sediments （〈160μm and 〈32μm ）, a series of experiments were run at time intervals of 6h, 12h and 24h. Total carbon content and carbon isotopic composition of the treated sediment samples under the different experimental conditions were analyzed in order to evaluate the efficiency of carbonate removal from marine sediments. The results were as below. （1） The amount and concentration of hydrochloric acid is the most critical factor in terms of increasing reaction rate and efficiency of acidolysis reaction between carbonates in sediments and hydrochloric acid and in terms of obtaining repeatable measurement of TOC and δ13Corg. （2） Since the reaction is spontaneous and exothermic, increasing temperature is not required, because high temperature may lower the concentration of hydrochloric acid and then make the reaction even slower; in the other aspect, with temperature increasing, the organic matter decomposes more quickly, which significantly affects the accuracy of TOC and δ13Corg measurement. （3） Enormous decomposition of carbonates in sediments ocurs within 6hours in the presence of superfluous 1.0mol·L^-1 HCl. （4） The smaller the grain size of sediments is, the faster the reaction takes place, correspondingly the smaller the dispersion degree of the analytical results is.