N. Laverov Federal Center for Integrated Arctic Research, IEPS, Russian Academy of Science, Arkhangelsk, Russia.
N. Laverov Federal Center for Integrated Arctic Research, IEPS, Russian Academy of Science, Arkhangelsk, Russia; Geoscience and Environment Toulouse, UMR 5563 CNRS, University of Toulouse, Toulouse, France.
Sci Total Environ. 2018 May 1;622-623:1343-1352. doi: 10.1016/j.scitotenv.2017.12.030. Epub 2017 Dec 13.
Photo-induced degradation of dissolved organic matter (DOM) and organo-mineral colloids is one of the major factor responsible for transformation of DOM and dissolved metals in boreal and subarctic waters. In contrast to fairly good understanding of this process in inland waters of high latitude zone, the transformation of riverine DOM and associated trace element (TE) colloids in the Arctic estuaries remains virtually unknown. We incubated, under sunlight in outdoor pools, quartz reactors filled with mixtures of sterile filtered riverine and estuarine water. The water samples were collected in the estuarine zone of the largest European Arctic river, Severnaya Dvina. After 1month of exposure to sunlight, ≤5% change of dissolved organic carbon (DOC) concentration and specific ultraviolet (254nm) absorption occurred. This decrease was within the experimental uncertainty and it implies quite high resistance of river dissolved organic matter to photo-degradation in this estuary. Moreover, very low photodegradability of DOM in the freshwater point of the Severnaya Dvina River may require revisiting the current paradigm of the importance of DOC photolysis in large Arctic rivers. A novel finding was that the percentages of overall removal of Fe and some insoluble elements were quite similar across the full range of studied salinities, whereas the apparent rate of metal removal decreased with the increase of salinity. Overall, the salinity weakly impacted the removal of riverine DOC and metals in the estuarine water via photolysis and coagulation under sunlight. As a result, photoreactivity of DOM and dissolved metals in riverine end members corrected for estuarine dilution can be used to approximate the photolytic transformation of riverine material in the Arctic coastal zone.
光诱导的溶解有机质（DOM）和有机-矿物胶体的降解是导致北方和亚北极水域中 DOM 和溶解金属转化的主要因素之一。与高纬度内陆水域中对这一过程的相当了解相比，北极河口的河流 DOM 和相关痕量元素（TE）胶体的转化几乎未知。我们在户外水池中的石英反应器中，用无菌过滤的河流和河口水混合物进行了光照孵育。水样取自欧洲最大的北极河流——Severnaya Dvina 的河口区。在阳光照射 1 个月后，溶解有机碳（DOC）浓度和特定紫外（254nm）吸收的变化≤5%。这种减少在实验不确定性范围内，这意味着在该河口，河流水解有机物对光降解具有相当高的抵抗力。此外，Severnaya Dvina 河流的淡水点 DOM 的光降解性非常低，可能需要重新审视当前 DOC 光解在大型北极河流中的重要性范式。一个新的发现是，在所研究的盐度范围内，整体去除铁和一些不溶性元素的百分比非常相似，而金属去除的表观速率随着盐度的增加而降低。总体而言，盐度通过光解和阳光照射下的凝聚，对河口水中的河流 DOM 和金属的去除影响较弱。因此，可以校正河口稀释的方法来使用河流末端物质的 DOM 和溶解金属的光反应性来近似北极沿海地区河流物质的光转化。
