Study on the improvement of underwater light field in Wuli lake ecological demonstration project
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摘要: 2004年7月20日在五里湖南岸生态示范工程区共布设9个采样点进行水下光场的测定,并采集水样分析悬浮物、叶绿素a、DOC浓度和各组分吸收系数。结果表明,3类主要光衰减物质总悬浮物、叶绿素a和DOC的浓度分别为5.1~38.7 mg/L、25.5~86.4μg/L和7.43~8.74 mg/L;生态示范工程能明显降低水体悬浮物和叶绿素a浓度,Ⅱ类区总悬浮物、叶绿素a浓度相对Ⅰ类区分别降低了53.4%、33.0%,而Ⅲ类区总悬浮物、叶绿素a浓度相对Ⅰ类区分别降低了77.4%、65.0%。光合有效辐射(PAR)衰减系数在1.81~4.93 m-1间变化,对应的真光层深度为0.93~2.54 m,Ⅱ、Ⅲ类区相对Ⅰ类区PAR衰减系数分别降低了42.2%、52.8%,对应的真光层深度则分别增加了73%、112%。ag(440)、ad(440)、aph(440)的变化范围分别为0.79~1.31 m-1、0.41~2.22 m-1、0.73~2.12 m-1。纯水对总吸收的贡献均在15%以下,有色可溶性有机物(CDOM)吸收对总吸收的贡献率在18.16%~40.28%间变化,非藻类颗粒物对总吸收的贡献率在14.40%~37.88%间变化,浮游藻类对总吸收系数的贡献率基本上是各组分贡献率中最高的,在31.05%~45.28%间变化。对PAR衰减系数、真光层深度、透明度等表观光学参数与主要水色因子进行相关分析发现,水体中浮游藻类和有机颗粒物对生态示范区内的水体光学性质影响最大,而围隔外围浮游藻类、非藻类颗粒物对光的衰减相当。Abstract: On July 20,2004,the underwater irradiance was measured and the water samples were collected at 9 sampling sites in Wuli lake ecological demonstration project.The concentrations of total suspended mater(TSM),organic suspended matter(OSM),inorganic suspended mater(ISM),chlorophyll a(Chla),dissolved organic carbon(DOC)and absorption coefficients of total particles,phytoplankton,nonalgal part icles and chromophoric dissolved organic matter(CDOM)were mea sured and calculated TSM,Chla and DOC are in the range of 5.1-38.7 mg/L,25.5-86.4μ/L,7.43-8.74 mg/L,respectively.The ecological demonstration project can signif icantly decrease the concentrations of TSM and Chla TSM,Chla of type region decrease by 53.4%,33.0% and TSM,Chla of Ⅲ type region decrease 77.4%,65.0% relative to type region,photosytheically available radiation(PAR)diffuse at enuation coefficients range from 1.81 to 4.93 m-1,and the corre sponding euphotic depths range from 0.93 to 2.54 m PAR diffuse attenuation coefficients of Ⅱ and Ⅲ type region decrease by 42.2%,52.8%,respectively,and the corresponding euphotic depths increase 73%,112%,respectively. Absorption coefficient of CDOM at 440 nm(ag(440)),absorption coefficient of nonalgal particles at 400 nm(ad(440))and absorption coefficient of phytoplankton at 440 nm(aph(440))are in the range of 0.79-1.31 m-1,0.41-2.22 m-1 and 0.73-2.12m-1 The relative contribution of pure water(aw)to total absorption coefficient(a)integrated over the range of PAR(400-700 nm)is less than 15%.The relative contributions of CDOM(ag),nonalgal particles(ad)to total absorption coefficient (a)are in the range of 18.16-40.28%,14.40-37.88%,respectively.The relative contributions of phytoplankton(aph) to total absorption coefficient(a)is the biggest,ranging from 31.05 to 45.28%.Based on the regression analysis between PAR attenuation coefficients,euphotic depths,secci disc and main light attenuators and the relative contribution of every component,phytoplankton and organic suspended solid play a main role in regulating the attenuation of light in ecological demonstration project in Wuli lake However,the roles of phytoplankton and nonagal particles in regulating the attenuation of light are almost equal to type region of the periphery of ecological demonstration project.
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