Origin and Factors Effecting Dissolved Organic Matter in Karst Spring, Southwest China

Abstract

The dissolved biomarker composition of water samples was detected and quantified through gas chromatography-mass spectrometry to investigate the source of organic matter and its influencing factors in a subtropical monsoon karst spring. All water samples were collected in Chongqing, southwest China, in May, June, and July 2015. An analysis of the carbon number distribution characteristics and molecular characteristic parameters indicated that the dissolved organic matter in water samples mainly came from microorganism. The average biomarker contents in the samples were controlled by multi-factor coupling and showed an increasing trend in May, June, and July; this trend was consistent with temperature and inverse with rainfall. Human activities, such as urbanization and land use type, affected the fatty acid composition of the spring water. In forested land, the main fatty acids in water were saturated normal fatty acids with carbon numbers of 14,16, and 18, respectively. The C16:1ω9 (c) fatty acid, denoting the origin of algae, was found in high abundance in the water samples of the Mudu River Basin, which contains agricultural land far from urban areas. C18:1 ω9 (t), a biomarker of Gram-negative bacteria, was detected in large quantities in the cultivated land of the Laolongdong watershed.