Study on the relationship between light intensities in water and photo-degradation of dissolved organic matter.

为了阐明水中腐殖物质和有机污染物的光化学降解性，进行了腐殖物质的分离、表征和光化学实验。(1)从河湖水中分离腐殖物质为了从水中分离腐殖物质，对XAD树脂吸附、真空浓缩和分子筛、超滤等几种方法进行了研究。其中切向流超滤效果最好。因此，将10至60 L的河流和琵琶湖水样品超滤以获得腐殖酸级分。(2)腐殖物质的表征与定量分析水样中分离出的腐殖酸组分具有以下理化性质。它们通过吸收365 nm的紫外线而发射478 nm的荧光。它们的紫外光谱几乎不随pH变化。水中腐殖酸组分的木质素酚组合物指示流域的时间植被类型。上游水体中腐殖酸组分占DOC的90%以上，下游水体中腐殖酸组分占DOC的50%左右。(3)腐殖酸组分和有机污染物的光化学降解性从水中分离的腐殖酸组分在有和没有被鉴定为水中有机污染物的标准化合物的情况下被辐照。太阳光和人造光被用作光源，石英瓶被用作反应容器。光化学降解的时间进程监测的变化，它们加速光降解的芳烃。首次发现尿素在水中发生光化学降解。

In order to clarify the photochemical degradability of humic substances and organic pollutants in water, separation and characterization of humic substances and photochemical experiments were conducted.(1) Separation of humic substances from river and lake watersTo separate humic substances from water, several procedures including XAD-resin adsorption, concentration in vacuo and molecular sieving, and ultra-filtration were examined. Among them, tangential-flow ultra-filtration gave the best result. Thus, 10 to 60 L of river and Lake Biwa water samples were ultra-filtered to obtain humic fraction.(2) Characterization and quantification of humic substancesThe humic fractions separated water samples have following physical and chemical properties. They emit fluorescence of 478 nm by absorbing 365 nm of UV.Their UV spectra show little pH-dependent change. Lignin phenol compositions of the humic fraction in water are indicative of the temporal vegetation type of the watershed. The humic fraction accounts for more than 90% of DOC in upstream water and about 50% in Lake Biwa water with decreasing its contribution in the downstream.(3) Photochemical degradability of humic fraction and organic pollutantsThe humic fraction separated from water was irradiated with and without standard compounds identified as an organic pollutant in water. Solar and artificial lights were used as a light source, and a quartz bottle as a reaction vessel. A time course of photochemical degradation was monitored by changes inThey accelerated photo-degradation of aromatic hydrocarbons. Urea was found for the first time to be degraded photochemically in water.