Tracing The Migration And Changes Of DOM In Typical Karst Subterranean River

With the continuous development of city industrialization,human activities become an important factor affecting the source of organic matter in Karst Underground River.At the same time,Numerous studies have proved that DIC?dissolved inorganic carbon,including CO2?aq?,HCO3-,CO32-,mainly HCO3-at pH=7⁹?can be preserves in the relatively stable from of organic carbon?OC?through photosynthesis of phytoplankton in aquatic ecosystems.Because of the particularity of karst area,The organic matter can enter the material circulation and energy flow of the underground karst system directly through the water hole,the skylight and the inf iltration of the soil.Fatty acid is an important component of lipids,which has been widely applied in trace organic matter sourcesThis study is based on the Nanshan Laodongdong and Qiangmuguan subterranean rivers which located in Chongqing province,Comparative analys is the temporal and spatial variation of fatty acid characteristics,sampling analysis by rainfall encryption,discuss variation characteristics aboutfatty acid content and composition in karst subterranean river during rainfall events.The sampling analysis of Nanshan Laolongdong and Qingmuguan underground river at 6 points,The results as below:?1?The content of dissolved fatty acids ranges from 587 to 50214 ng·L^-1 in Nanshan laolongong,the mean value of whose particulate fatty acids is 9897 ng·L^-1,The content of dissolved fatty acids ranges from 356 to 24970 ng·L^-1 in Q ingmuguan,the mean value of whose particulate fatty acids is 4935 ng·L^-1.The fatty acid compositions of Nanshan Laolongong and Q ingmuguan underground rivers are dominated by Saturated straight chain fatty acid,each of which in Laolongdong' Nanshan is showed as SSFA>MUFA>BSFA>PUFA in Laolongdong and each in Q ingmuguan is showed as SSFA>BSFA>MUFA>PUFA.Microorganisms such as algae and bacteria in the subterranean river are the causes of different organic matter,Changes of fatty acid composition in underground river,Land use influences supply sources.?2?The differences in the activities of people in the river basin affect the source of organic matter in Laolongdong and Q ingmuguan underground river.The underground river is seriously polluted and the sewage is discharged into the underground river,or sewage leakage into the underground river,the underground river is facing the risk of becoming a sewer,the river is muddy and peculiar smell.In Laolongdong underground river,dissolved fatty acids mainly come from bacterial and phytoplankton sources,influenced by natural and human activities.Under the natural condition,there is a stud farm in the valley,there is no factory distribution.The population density is higher in the Longdong basin,a large number of distribution hot pot shop,factory aggregation,there are manywaste incineration points.In Qingmuguan underground river,dissolved fatty acids mainly come from Mixed input of phytoplankton,fungi and a small amount of fat in higher plants.Fatty acid concentration shows a seasonal variation in Q ingmuguan and Laolongdongb underground rivers:the fatty acid concentration in rainy season is higher than that in dry season.The content of dissolved fatty acids is mainly affected by rainfall in Q ingmuguan and Laolongdong underground rivers.?3?During the rainfall monitoring period,Qingmuguan is faster than Laolongdong that the underground river response to rainfall.During the rainfall event,The dissolved and particulate fatty acid content in Laolongdong underground river is higher than that in Qingmuguan underground river.The concentration of dissolved fatty acids manifests itself as SSFA>MUFA>PUFA>BSFA in the Laolongdong and Qingmuguan underground river,during the rainfall,the branched chain saturated fatty acids which are indicated of the source of the bacteria are diluted,while the polyunsaturated fatty acids derived from algae and bacteria are increased by the effects of surface runoff.Comparison between the samples during the rainfall and the conventional sampling: the mean of Jiangjiaquan particle and dissolved fatty acid is higher than that of conventional sampling.During the rainfall period,the effect of rainfall on soil erosion is stronger,and the surface runoff is formed after rainfall,a large amount of surface organic matter is brought into the underground river,and the difference content of organic matter on the surface of the river basin directly affected the organic matter in the underground river.Compared with long chain saturated fatty acids and unsaturated fatty acids,the Short chain saturated fatty acids and branched chain saturated fatty acids move faster to underground river outlet.?4?During the rainfall event,in Laolongdong underground river "old water" is mainly controlled by bacterial and phytoplankton.in Q ingmuguan underground river "old water" is mainly controlled by fungal."O ld water" stay for a long time in the underground r iver pipeline,During the rainfall season the drop water and fracture water bring a large number of organic matter sources which is come from fungal in soil cover into the underground river.Fatty acids carried by surface runoff mainly derived from phytoplankton and fungal in Qingmuguan and from phytoplankton and fungal in Q ingmuguan.Fungal fatty acid accounted for an absolute advantage in Laolongdong because of the terrigenous fatty acids influencet.During the rainfall season the drop water and fracture water bring a large number of organic matter sources which is come from fungal in soil cover into the Laolongdong and Qingmuguan underground river,the differences of land use between the Q ingmuguan and Laolongdong are the main factors affecting the source of organic matter in the underground river.T he dissolved organic matter is controlled by fungal.The organic matter of the phytoplankton source is brought by surface runoff enters into the Q ingmuguan underground river.