Abstract:To quantify impacts of oxygen distribution dynamic on exchange process between surface sediment and overlying water, we employed O2 penetrating microelectrode system (Unisence Ltd., Denmark) to obtain multiple high resolution microprofiles of in-situ O2, calculated O2 exchange rate using Fick First Law. Besides, we also investigated the influence of anaerobic and aerobic processes (microaeration air bubbles, microaeration nitrogen bubbles, injection CaO2 suspension into surface sediments) on mineralization of soil organic matter. In the present study, the results showed that diffusive boundary layer (DBL) thickness containing significant chemical gradients, which greatly limited oxygen exchange between bottom water and topsoil, is dependent on oxygen levels in the benthic overlying water. In anaerobic conditions by means of nitrogen microbubbles, DBL ranged from 0.2 to 0.4millimeters in thickness. However, DBL thickness increased dramatically between 0.4~0.7mm (P<0.05) compared to treatments with bubbling air or injection CaO2 suspension into surface sediments. Also, O2 exchange was accelerated in the case of enough oxygen supply. O2 benthic diffusive flux were (5.31±0.66) and (17.14±3.15) mmol O2/(m2·d) in bubbling air treatment, injection CaO2 suspension into surface sediments, increased by 9% and 250% in relation to (4.87±0.92) mmol O2/(m2·d) in control, respectively. An obvious tendency for increasing O2exchange was observed with temperature rise.
古小治, 张启超, 孙淑雲, 陈开宁. 富氧-缺氧过程对氧气分布及交换过程影响[J]. 中国环境科学, 2015, 35(5): 1495-1501.
GU Xiao-Zhi, ZHANG Qi-Chao, SUN Shu-Yun, CHEN Kai-Ning. Influence of anaerobic and aerobic processes on bottom oxygen dynamic and exchange process across sediment- water interface. CHINA ENVIRONMENTAL SCIENCECE, 2015, 35(5): 1495-1501.