Institute of Hydrobiology, Biology Centre of the AS CR, v.v.i., Na Sádkách 7, České Budějovice, 37005, Czech Republic.
Environ Monit Assess. 2010 Dec;171(1-4):71-81. doi: 10.1007/s10661-010-1529-x. Epub 2010 Jun 10.
Laboratory photochemical experiments with stream water were done to characterize the photodegradation of dissolved organic carbon (DOC) and photochemical release of organically bound metals. The samples were collected from Bear Brook Watershed, Hadlock Brook, and Mud Pond Stream in Maine, USA, during January and April 2006. Filtered samples were irradiated in a reactor equipped with 350 nm irradiation lamps. Aliquots of irradiated samples were analyzed for DOC, dissolved aluminum (Al(d)) and iron (Fe(d)), pH, and UV-Vis spectra. Organically bound metals (Fe(o) and Al(o)) were measured after passing the sample through a column filled with a strong cation exchange resin (Dowex HCR-W2). UV radiation resulted in a decrease in DOC concentration and structural changes in DOC composition. UV-Vis spectra showed a decrease in aromaticity and molecular weight of DOC during irradiation. The DOC ranged from 0.1 to 0.35 mmol L(-1) at the beginning of experiments and decreased 5% to 37% after irradiation. Oxidation and structural changes in DOC resulted in the release of organically bound metals. Initial Fe(o) concentrations ranged from 0.16 to 0.79 μmol L(-1) and decreased 56% to 81% during the irradiation. The concentration of Al(o) ranged from 1.0 to 3.85 μmol L(-1) and declined steadily throughout the irradiation, resulting in 8% to 76% decline. Degradation of a small percentage of organically bound Al and Fe occurs rapidly enough so as to be an important process in first- and second-order streams. Irradiation energy absorbed by samples during hours of laboratory experiments equates to days in stream environment. Degradation of more refractory complexes occurs on a time scale that requires longer residence times, such as in lakes. This study demonstrated a strong impact of photochemical degradation of DOC on its metal-complexing ability and capacity. The results also suggest different binding properties of Fe and Al in their organic complexes.
实验室对河水进行光化学实验，以表征溶解有机碳（DOC）的光降解和有机结合金属的光化学释放。这些样品是 2006 年 1 月和 4 月在美国缅因州的熊溪流域、哈多克溪和泥塘溪采集的。过滤后的样品在装有 350nm 照射灯的反应器中进行照射。辐照后的样品的一部分用于分析 DOC、溶解铝（Al(d)）和铁（Fe(d)）、pH 值和紫外-可见光谱。有机结合金属（Fe(o)和 Al(o)）在通过填充有强阳离子交换树脂（Dowex HCR-W2）的柱子后进行测量。紫外辐射导致 DOC 浓度降低和 DOC 组成结构发生变化。辐照过程中，DOC 的紫外-可见光谱显示出芳香度和分子量降低。实验开始时，DOC 的浓度范围为 0.1 至 0.35mmol/L，辐照后下降 5%至 37%。DOC 的氧化和结构变化导致有机结合金属的释放。初始 Fe(o)浓度范围为 0.16 至 0.79μmol/L，辐照过程中下降 56%至 81%。Al(o)的浓度范围为 1.0 至 3.85μmol/L，整个辐照过程中持续下降，下降 8%至 76%。一小部分有机结合的 Al 和 Fe 迅速降解，足以成为一级和二级河流中重要的过程。实验室实验中样品吸收的辐照能相当于河流环境中的数天。更难降解的络合物的降解需要更长的停留时间，如在湖泊中。本研究表明，DOC 的光化学降解对其金属络合能力和容量有很大影响。结果还表明，Fe 和 Al 在其有机络合物中的结合性质不同。
