In the summer of 2007, one cruise survey on terrigenous chromophoric dissolved organic matter (CDOM) was carried out in the Zhoushan sea area of the East China Sea.Fluorescence intensities at the excitation wavelength 370 nm/the emission wavelength 460 nm and absorption coefficients at the wavelength 355 nm were determined, which represented terrigenous CDOM concentrations.Fluorescence indices were also measured as the indicator of CDOM sources.The results show that CDOM concentrations roughly tend to decrease in the direction from the land to the sea, but there is some phenomenon of vertical jump.High concentrations of CDOM in the surface water were observed at some sites of the northeast of the Zhoushan sea area from time to time, but they showed a great variability, which suggesting that the waters might be subject to the impact of estuarine plume of the Changjiang River.It is found at a continuous observation station that the concentrations of CDOM at the low tide are often higher than those at the high tide.During the mixing process between river water and seawater, the CDOM concentrations and light absorption coefficients at 355 nm have a significant negative linear relationship with the salinity.That is to say, CDOM takes on the conservative behavior in general.However, CDOM concentrations are significantly lower than the theoretical dilution values in the low salinity zone, indicating a non-conservative removal behavior of CDOM in the suspended sediment front.The fluorescence indices are almost fixed at 1.50 in most of water samples with the salinity between 24 and 31, indicating that CDOM can be dominated with terrigenous sources.However, the fluorescence indices vary from 1.70 to 1.90 and above in low salinity (＜24) zone, indicating that CDOM can be dominated with marine sources; it is related to the significant removal of terrigenous fractions of CDOM in this zone with low salinity and high turbidity.These results prove that terrigenous organic matter can be used as a good tracer and indicate the variability of water quality in the coastal plume.%2007年夏季在东海舟山海域河口锋区开展了陆源溶解有机质的调查研究.测定了有色溶解有机质(CDOM)在激发波长370 nm/发射波长460 nm处的荧光强度和在λ=355 nm处的吸收系数,用于代表陆源CDOM浓度,并测定了荧光指数以指示CDOM来源.结果表明,CDOM的荧光值和紫外吸收系数之间呈显著正相关性,陆源CDOM浓度大体有向海方向降低的趋势,但是纵向上存在一些"突跃"现象.在舟山海域东北角不时观测到表层水体含有高浓度的CDOM,但变异性很大,推测可能该海区受到长江口羽状流的影响.在连续观测站发现陆源CDOM浓度在低平潮时往往比高平潮时要高.河海水在混合过程中CDOM浓度与盐度呈显著的线性负相关关系.在低盐度的悬沙锋区(S<24)CDOM浓度明显低于理论稀释值,而在较高盐度的羽状锋区,CDOM浓度接近于理论稀释值.在盐度为24～31范围内,大部分水样的荧光指数在1.50上下波动,表明其中CDOM来源以陆地来源为主;在较低盐度(S<24)的水样中荧光指数在1.70至1.90以上,表明CDOM以海洋来源为主,这与其陆源组分在高浊度的低盐度区存在显著的去除过程有关.研究表明,舟山海域水质存在着显著的变异性,与近岸羽状流密切相关,陆源溶解有机质的分布特征对此有较好的响应.
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