基于叶绿素a浓度的珠江口感潮河段咸潮监测研究

Study on Salinity based on Chlorophyll a in Saltwater Intrusion Reach,Pearl River Estuary

依据实测资料研究了珠江口最主要的感潮河段沙湾-虎门水道和磨刀门水道水体的叶绿素浓度、盐度的高光谱特征及其空间变化趋势。结果表明:水体叶绿素a浓度和反射率波段比值有较好的相关关系,最佳关系在R704/R513处,r=0.92;在盐度大于2‰的情况下,随着盐度增加叶绿素a浓度逐渐降低,并且向伶仃洋方向随着盐度的增加叶绿素a浓度是递减的。在珠江沙湾-虎门以及磨刀门感潮河段,水体表面盐度与叶绿素a浓度之间表现为较好的负相关关系,表明可以用叶绿素a浓度来推定咸潮的入侵情况。因此,通过遥感图像反演出水体的叶绿素a浓度进而推断珠江口河网区的咸潮入侵空间变化是可能的。

In this paper,the spectral and salinity properties of chlorophyll-a and their spatial change tendency in the saltwater intrusion reach,Pearl River Estuary from the in-situ data in December of 2006 were studied. Based on the experimental results,the relationship between chlorophyll-a concentration and remote sensing reflectance was analyzed,and a strong positive linear relationship between in-situ reflectance ratio （R704/R513） and chlorophyll-a concentration was found （r=0.92,P0.001）. Additionally,chlorophyll-a concentration and salinity were also discussed. The chlorophyll-a concentration decreased with the increasing salinity,and the salinity was mounting towards the Lingding Bay in saltwater intrusion reach,while the salinity was higher than 2‰. There was a good correlative relationship between chlorophyll-a concentration and the salinity in the Shawan-Humen and Modaomen Watercourse,meaning that chlorophyll-a concentration can be used to study the distribution and behavior of salinity,and then saltwater intrusion. Chlorophyll-a concentrations varied between 4.81 and 92.6 mg/m3,and salinity between 0.43 and 18.79‰. In the Shawan-Humen watercourse,the higher chlorophyll-a concentration of surface water was observed in Shawan tributary reach where the saltwater and freshwater interfaces; In the Modaomen watercourse,the highest chlorophyll-a concentration of surface water was observed in Shenwan watercourse because of sewage flow from Shiqi watercourse and narrow river way. The study indicated that the salinity can be monitored by remote sensing from chlorophyll-a concentration.