江苏近海有色可溶有机物时空分布特征

Temporal and Spatial Distribution Characteristics of Colored Dissolved Organic Matter in Coastal Waters of Jiangsu Province

有色可溶有机物(CDOM)是重要的水色要素之一,在"江苏沿海大开发"背景下,利用遥感分析其时空分布特征对监测近海水质及污染状况有重要的实际意义。用高时间分辨率的韩国静止水色卫星(GOCI)影像,在日、周、月多时间尺度上分析2011年4月至2016年5月江苏近海有色可溶有机物的时空分布特征。结果表明江苏近海CDOM以陆源为主,近岸高于远岸;月平均浓度最大值(0.180~0.206 m^(-1))在长江口最大浑浊带外,南黄海西岸次之(0.167~0.201 m^(-1)),南黄海中南部较低(0.086~0.187 m^(-1),440 nm吸收系数)。结合潮位数据,发现沿岸海域CDOM日变化与潮汐变化一致,但远海区域呈先减后增的特征。利用余弦函数对CDOM月均值进行拟合,发现南黄海月尺度变化周期性明显,其中南黄海中部海域拟合优度为0.823。南黄海主要受黄海冷水团影响,各子区季节变化显著,CDOM在冬春季高于夏秋季;长江口由于冲淡水及其他水团共同影响,情况复杂,冬春季低于夏秋季。月尺度下,CDOM浓度与悬浮物(TSM)呈正相关关系(相关系数r为0.72),且南黄海中部与南部CDOM随TSM的变化趋势较为显著。

Colored Dissolved Organic Matter （CDOM） is one of important ocean color factors. In the background of “Jiangsu Coastal Development”, it is important to monitor the water quality and pollution status of coastal waters by analyzing its spatial and temporal distribution characteristics with remote sensing data. This paper was based on the high temporal resolution of Geostationary Ocean Color Imager （GOCI） image downloaded from Korea Ocean Satellite Center. The temporal-spatial distribution of CDOM in Jiangsu coastal waters was analyzed on daily, weekly and monthly time scales from April, 2011 to May, 2016. CDOM in Jiangsu coastal waters are mainly terrigenous, and higher inshore than that of offshore. The monthly average concentration of CDOM in the western coast of the South Yellow Sea was 0.167-0.201 m^-1, and those of central and southern regions were 0.086-0.187m^-1. The maximum values were outside the maximum turbidity zone of the Yangtze River Estuary, which was 0.180-0.206 m^-1 （absorption coefficient at 440 nm）. The diurnal variation of CDOM in near shore waters was found to coincide with the change of tide, which decreased at first and then increased in the sea area. By fitting the monthly mean using cosine function, significantly cyclical variation of mean CDOM was found in the South Yellow Sea. The central region of the South Yellow Sea waters fitting coefficient was 0.823. Affected by the Yellow Sea cold water mass, the sub-regions of the South Yellow Sea changed seasonally, whose CDOM concentration in winter and spring was higher than that in summer and autumn. Because of Changjiang Diluted Water and other water masses, seasonal variation of the Yangtze River Estuary was contrary to that of the South Yellow Sea. On monthly scale, CDOM concentration was positively correlated with total suspended matter, with correlation coefficient r being 0.72. The trend of the central and southern region was more significant.