Distribution and Characterizations of Short-chain Organic Acids in the Seawater of the Jiaozhao Bay, China

Short-chain organic acids in marine environment play important roles in adjusting pH value, forming variety of complexes and then increasing solubility of trace metals in seawater. In this study, surface seawater samples were monthly collected during spring and summer seasons in 2010 from 19 stations in the Jiaozhou Bay, Qingdao, China. Concentrations of several short-chain organic acids of these samples were measured via high performance liquid chromatography based on modified 2-nitrophenylhydrazide derivatives methods. The concentrations of lactate, acetate and propionate ranged from 0 to 63.5 μmol/L, 0 to 19.4 μmol/L and 6.4 to 124.1 μmol/L, with average concentration of 19.6 μmol/L, 6.4 μmol/L and 98.9 μmol/L, respectively. Generally, concentrations of short-chain organic acids were lower in the central area of the bay than in its coastal area. Along coastal area, their concentrations were higher in east and west coast than in the north coast. Our results indicated both natural processes and human activities, including river discharge, ocean current, aquaculture, domestic sewage and industry strongly affected the distribution of short-chain organic acids. Industry might be the most important source of organic acids in the bay. This study showed that short-chain organic acids might be considered as unique indicator to track the influence of human activities on marine environment.