The Study On Three-dimensional Fluorescent Characteristics And Temporal/Spatial Variations Of Dissolved Organic Matter In The Hot Spring In Green Island,Taiwan And Qiantang River

Chromophoric dissolved organic matter(CDOM)plays an important role in marine ecological environment and global carbon cycle.The research of the composition,source and dynamics of CDOM is of great significance in studying the biogeochemical cycle of different ecosystems.This thesis focused on the composition,source and dynamics of CDOM in the hot springs on Green Island and Qiantang River.Diurnal variations and the relationship of temperature,salinity,pH and DOC were investigated for hot spring samples obtained from Green Island off southeast Taiwan at 3h intervals over a diurnal period.The characteristics of fluorescent components and diurnal variation of CDOM were carried out using excitation emission matrix fluorescence(EEMs)spectroscopy combined with parallel factor analysis(PARAFAC).It was observed that the warm water area would have a third freshwater source such as groundwater besides the seawater and the hot spring vent fluids.The mixing ratio of the hot spring vent fluids,seawater and freshwater was estimated to be 2:3:1 based on temperature,salinity,pH and DOC.We also observed significant diurnal changes of DOC concentration with the highest amplitude at the warm water area from 84?M to 130?M,negative correlation between the DOC concentration and temperature,and positive correlation between the DOC concentration and phosphate concentration.The DOC concentration at the hot spring vent demonstrated a relative stable concentration pattern without apparent link to temperature,phosphate concentration and tides.Four fluorescent components were identified by EEM-PARAFAC:tryptophan-like C1,humic-like C2 and C3,as well as special component C4.The hot spring vent was a source of the fluorescent components C1 and C4,the fluorescence intensities of which were higher than those of the warm water area and the surrounding seawater.The high values of fluorescence index(FI)and autochthonous index(BIX)as well as low values of humification index(HIX)at the two areas of the hot springs suggested that the CDOM might be mainly autochthonous biological or bacterial origin in the study.The study of the composition,source and dynamics of CDOM in Qiantang River was also carried out.The DOC concentration of Qiantang River Section was higher than that of Fuchun River Section but lower than that of the Puyang River Tributary,which is consistent with the fact that the water in Qiantang River Section came from the Fuchun River Section and the Puyang River Tributary.The absorption coefficient a355 and DOC concentration had a significant negative correlation,which suggested that CDOM and DOC had a similar spatial distribution as well as there was a lot CDOM in the compositions of DOC.Three fluorescent components were identified by EEM-PARAFAC:humic-like C1,tryptophan-like C2 and C3.C1 might had a terrestrial source while C2 and C3 had an autochthonous source.In addition,the low values of humification index(HIX)and high values of fluorescence index(FI)and autochthonous index(BIX)in Qiantang River suggested that the DOM might be mainly autochthonous biological or bacterial origin.Overall,compared with the Fuchun River Section,the concentration of humus components was lower while the concentration of protein was higher in the Puyang River Tributary and Qiantang River Section.It indicated that there were more nutrient from human activities in Puyang River Tributary and Qiantang River than in Fuchun River Section.Compared with the hot springs on Green Island,the surface water of Qiantang River had higher DOC concentration,higher CDOM concentration,relatively higher molecular weight of CDOM and lower degree of humification.