香溪河库湾春季水华期间水体光学特征及相关分析

CHARACTERISTIC AND REGRESSION ANALYSIS OF THE PAR ATTENUATION COEFFICIENT IN XIANGXI BAY DURING SPRING BLOOM

研究了香溪河库湾春季水华期间(2006年3月3日—4月16日)透明度水层可见光衰减系数KSd的时空特征,分析其与表层水叶绿素a浓度、DOC浓度和透明度Sd的相关关系。结果表明:香溪河库湾春季水华可见光衰减系数KSd时空变异很大;除峡口河段(样点X7—X8)外,可见光衰减系数KSd的变化特征取决于叶绿素a浓度和DOC浓度的时空变化,类似于深水湖泊;除峡口河段(样点X7—X8)外,香溪河库湾可见光衰减系数KSd和透明度之间呈反比的关系具有显著的相关,但它们之间的反比关系因水体叶绿素a和无机悬浮颗粒的空间差异而有所不同。

During the period of spring bloom from March 3 to April 16,2005 in Xiangxi Bay, The vertical attenuation coefficients （KSd） of downward visible irradiance（PAR） and Secchi disc transparency（Sd） were measured with a scanning spectroradiometer and a 30 cm diameter black and white quadrant disc. Water chemistry variables such as chlorophyll-α and dissolved organic carbon（DOC） were measured to determine the relative contribution of attenuating constituent in explaining the substantial variation in the PAR attenuation coefficients KSd. Based on the in situ investigation data obtained, The underwater light field in Xiangxi Bay was characterised and the relationship between these two optical properties of the underwater was quantified with SPSS software. The analyses including application of empirical theories demonstrate that temporal patterns and inter-system differences in KSd and 1/Sd during the period were well correlated for most of the sampling sites, except in the Xiakou reach, and the inverse relationship these two optical properties is influenced by chlorophyll-α and inorganic tripton to some extent. Regression Analyses of these PAR attenuation coefficient data and observations of Chla and DOC, documente that Chlorophyll α and Dissolved organic carbon are the important constituents responsible for spatial distribution and temporal variation of the PAR attenuation coefficients KSd in Xiangxi Bay, except in the Xiakou raech. In addition to application of empirical and deterministic modeling frameworks, those results demonstrate that the Xiangxi Bay in the optic characteristic during the period of spring bloom is similar to many deep lakes, and differ from many shallow lakes where increase of total suspended matter due to sediment resuspension results in decrease of transparency and increase of beam attenuation coefficient.