Temporal variability of chromophoric dissolved organic matter in the Pearl River Estuary, China from 2003 to 2009

摘要

The present study aims to investigate the temporal variability of chromophoric dissolved organic matter through remote sensing and to determine its influence factors in the Pearl River Estuary. A medium resolution imaging spectrometer, chromophoric dissolved organic matter product was evaluated with in situ absorption coefficient (R-2 = 0.9605, RMS = 0.1672 and MRE = 0.3930). L2 daily products were then averaged into monthly data to analyze variability in the specified area from January 2003 to December 2009. Accumulated anomaly analysis and the wavelet analysis showed that the variability had a significant period of one year from 2003 to 2009, accompanied with 3 and 6 month periods in 2004 and 2008 separately. Cross wavelet transform was used to analyze the relationships between chromophoric dissolved organic matter and its influence factors including rainfall and phytoplankton in time frequency space. Relationships with salinity and light were also analyzed. It was found that photobleaching induces lower dissolved organic matter in summer even though there is greater discharge due to large rainfall intensity during this season. However, the anomalous strong precipitation may cause significantly higher findings in the study area. An example was a heavy flood caused by strong precipitation in 2008 induced higher findings for the period for less than half a year.