有色可溶性有机物在线荧光技术在水质监测中的应用

Application of Online Fluorescent Dissolved Organic Matter Sensor in Water Quality Monitoring

FDOM(荧光有机物)在线荧光探头是采用激发波长370 nm和发射波长460 nm下荧光强度来计算水体CDOM(有色可溶性有机物)丰度的传感器,为探究该传感器在内陆水体水质监测中的应用和适用性,以水源供给水库千岛湖为案例,通过FDOM荧光探头监测该湖泊不同季节CDOM丰度,结合CDOM光谱吸收、ρ(DOC)(DOC表示溶解性有机碳)、ρ(TN)、ρ(TP)、ρ(CODMn)、ρ(DTN)(DTN表示溶解性总氮)、ρ(DTP)(DTP表示溶解性总磷)和ρ(Chla)等水质参数数据,揭示FDOM荧光强度与其他水质参数的耦合关系,检验FDOM荧光探头对有机物的监测能力.结果表明:①2014年5月千岛湖TLI平均值(38.4±4.4)显著高于2018年10月TLI平均值34.9±3.0(t-test,P<0.001),根据TLI及各水质参数平均值判定该湖处于中贫营养状态.②大部分水质参数呈现出由西北入湖河口向下游大坝出水口方向递减的趋势,表明上游新安江对该湖有机物具有较大的贡献.③FDOM荧光强度与CDOM吸收系数a(254)(R^2=0.91,P<0.01)、a(350)(R^2=0.90,P<0.01)均呈极显著正相关且具有较高的线性拟合优度,这意味着FDOM荧光强度可以很好地表征CDOM丰度.④FDOM荧光强度与ρ(DOC)(R^2=0.49,P<0.01)、ρ(TN)(R^2=0.61,P<0.01)、ρ(TP)(R^2=0.75,P<0.01)、ρ(CODMn)(R^2=0.35,P<0.01)、ρ(DTN)(R^2=0.59,P<0.01)、ρ(DTP)(R^2=0.56,P<0.01)、ρ(Chla)(R^2=0.68,P<0.01)均呈极显著正相关且与大多数水质参数具有相似的分布特征,并且能很好地识别潜在污染物高值区.研究显示,荧光探头在可见波长下所得陆源类腐殖酸FDOM荧光强度能很好地成为潜在污染物替代指标,并能有效呈现有机物分布特征,因而该技术在饮用水湖泊水质监测中具有潜在广阔的应用前景.

The application of online fluorescence sensor in water quality monitoring has attracted increasing attention.FDOM(fluorescent dissolved organic matter)online probe is a sensor which uses excitation wavelength 370 nm and emission wavelength 460 nm to determine the dynamics of CDOM in water.We explored the applicability of this online fluorescence sensor in drinking water quality monitoring.We conducted field sampling at Lake Qiandao,and used fluorescent dissolved organic matter(FDOM)sensor as a surrogate of CDOM(chromophoric dissolved organic matter)concentration in different seasons of Lake Qiandao,combined with CDOM spectral absorption,TN,TP,DOC(dissolved organic carbon),CODMn and other water quality indices.The results showed that:(1)The mean value of TLI in May 2014 was 38.4±4.4,the mean value of TLI in October 2018 was 34.9±3.0,and there was a significant difference between the two mean values(P<0.001,t-test).According to the value of TLI and the mean value of the water quality parameters,the lake was in oligo-and mesotrophic state.(2)Most of the water quality parameters showed a decreasing trend from the northwest inflowing estuary to the downstream open waters,indicating that the upstream Xin'an River had contributed significantly to the CDOM pool of the lake.(3)There were significantly positive correlations between the fluorescence intensity of FDOM and CDOM absorption coefficient a(254)(R^2=0.91,P<0.01)and a(350)(R^2=0.90,P<0.01).This indicated that the fluorescence intensity of FDOM could be a useful tracer for CDOM concentration.(4)Statistical correlation analyses further showed that the fluorescence intensity of FDOM was significantly positively correlated toρ(DOC)(R^2=0.49,P<0.01),ρ(TN)(R^2=0.61,P<0.01),ρ(TP)(R^2=0.75,P<0.01),ρ(CODMn)(R^2=0.35,P<0.01),ρ(DTN)(R^2=0.59,P<0.01),ρ(DTP)(R^2=0.56,P<0.01)andρ(Chla)(R^2=0.68,P<0.01).FDOM displayed similar spatial distribution patterns with the above mentioned water quality parameters.This indicates that FDOM could be used to track the concentrations of water quality parameters in Lake Qiandao.Therefore,the FDOM sensor with an emission wavelength of about 460 nm of has broad application prospects in monitoring the water quality of drinking water lakes.