Based on Optical Properties of Chromophoric Dissolved Organic Matter in the Monitoring of Coastal Eutrophication

Eutrophication is an important ecological environment problem in estuary and coastal area. The traditional monitoring technology for eutrophication is laborious and time-consuming, so it is difficult to realize the real-time and on-site monitoring and then rapid evaluate the eutrophication degree. Based on the investigation of chromophoric dissolved organic matter(CDOM) and other environmental parameters in Xiamen Bay in February, May, August and from October to November 2009, the feasibility of using CDOM optical properties to retrieve eutrophication parameters (COD, TN and TP) in coastal environment was evaluated. CDOM showed large spatial and seasonal changes in Xiamen Bay, with the highest CDOM abundance occurring in the Jiulong River Estuary. The terrestrial input and phytoplankton production were the main sources of CDOM in Xiamen Bay. The empirical formula to estimate the CDOM abundance in seawater was then established by using the salinity and chlorophyll-a data. The correlation coefficient of this empirical formula was 0.96 and the relative errors between fitted values and measured values for CDOM of different survey stations were (11. 1% 0.71%. There were high correlations between CDOM absorption coefficient and fluorescence components with chemical oxygen demand(COD), total nitrogen(TN), total phosphorus (TP) in all seasons, with the highest correlations in spring and summer, and the lowest in winter. Combined with the above results, instead of the data including COD, TN and TP got only through manual samplings and laboratory analysis, the data of salinity and chlorophyll a could be provided by water quality automatic monitoring system and CDOM data got by above empirical formula, so it is possible to realize the rapid monitoring and evaluation for the degree of coastal eutrophication by using in situ buoy system with CDOM sensor.