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

为了弄清水中腐殖质和有机污染物的光化学降解性，对腐殖质进行了分离表征，并进行了光化学实验。(1)河湖水体中腐殖质的分离为了分离水体中的腐殖质，研究了xad树脂吸附、真空浓缩分子筛和超滤等几种方法。其中，切流超滤效果最好。因此，对琵琶江、琵琶湖水样进行10 ~ 60 L的超滤，得到腐殖质馏分。(2)腐植酸物质的表征和定量从水样中分离出的腐植酸组分具有以下物理和化学性质。它们通过吸收365纳米的紫外线发出478纳米的荧光。它们的紫外光谱随ph值变化不大。水体腐殖质组分的木质素酚组成反映了流域的植被类型。腐殖质组分在上游水体DOC中占90%以上，在琵琶湖水体中占50%左右，其在下游的贡献逐渐减少。(3)腐殖质组分和有机污染物的光化学降解性对从水中分离出来的腐殖质组分进行了有和无标准化合物的水中有机污染物照射。太阳能和人造光源被用作光源，石英瓶作为反应容器。通过测定它们对芳香烃光降解的加速作用，监测光化学降解的时间过程。首次发现尿素在水中光化学降解。

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.