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Influence of dissolved organic matter on carbonyl sulfide and carbon disulfide formation from cysteine during sunlight photolysis.
Environmental Science: Processes & Impacts ( IF 5.5 ) Pub Date : 2020-07-22 , DOI: 10.1039/d0em00219d Mahsa Modiri Gharehveran 1 , Ethan Hain 2 , Lee Blaney 2 , Amisha D Shah 3
Environmental Science: Processes & Impacts ( IF 5.5 ) Pub Date : 2020-07-22 , DOI: 10.1039/d0em00219d Mahsa Modiri Gharehveran 1 , Ethan Hain 2 , Lee Blaney 2 , Amisha D Shah 3
Affiliation
Carbonyl sulfide (COS) and carbon disulfide (CS2) are important atmospheric gases that are formed from organic sulfur precursors present in natural waters when exposed to sunlight. However, it remains unclear how specific water constituents, such as dissolved organic matter (DOM), affect COS and CS2 formation. To better understand the role of DOM, irradiation experiments were conducted in O2-free synthetic waters containing four different DOM isolates, acquired from freshwater to open ocean sources, and the sulfur-based amino acid, cysteine (CYS). CYS is a known natural precursor of COS and CS2. Results indicated that COS formation did not vary strongly with DOM type, although small impacts were observed on the kinetic patterns. COS formation also increased with increasing CYS concentration but decreased with increasing DOM concentration. Quenching experiments indicated that ˙OH was not involved in the rate-limiting step of COS formation, whereas excited triplet states of DOM (3CDOM*) were plausibly involved, although the quenching agents used to remove 3CDOM* may have reacted with the CYS-derived intermediates as well. CS2 was not formed under any of the experimental conditions. Overall, DOM-containing synthetic waters had a limited to no effect towards forming COS and CS2, especially when compared to the higher concentrations formed in sunlit natural waters, as examined previously. The reasons behind this limited effect need to be explored further but may be due to the additional water quality constituents present in these natural waters. The findings of this study imply that multiple variables beyond DOM govern COS and CS2 photoproduction when moving from freshwaters to open ocean waters.
中文翻译:
阳光下光解过程中溶解的有机物对半胱氨酸中羰基硫和二硫化碳形成的影响。
羰基硫(COS)和二硫化碳(CS 2)是重要的大气气体,当暴露于阳光下时,它们是由天然水中存在的有机硫前体形成的。但是,尚不清楚特定的水成分(例如溶解的有机物(DOM))如何影响COS和CS 2的形成。为了更好地理解DOM的作用,在含有O 4的合成水中进行了辐照实验,该合成水包含四种不同的DOM分离物(从淡水获取到开放的海洋资源)以及基于硫的氨基酸半胱氨酸(CYS)。CYS是COS和CS 2的已知天然前体。结果表明,尽管对动力学模式影响很小,但COS的形成随DOM类型变化不大。COS的形成也随着CYS浓度的增加而增加,但随着DOM浓度的增加而减少。淬火实验表明,˙OH不参与COS形成的限速步骤,而DOM的激发三重态(3 CDOM *)可能与之相关,尽管用于除去3 CDOM *的淬灭剂可能已与CYS反应衍生的中间体。在任何实验条件下均未形成CS 2。总体而言,含DOM的合成水对形成COS和CS 2的影响有限,尤其是与先前检查过的在日光照射的天然水中形成的较高浓度相比时。这种局限性作用背后的原因有待进一步探讨,但可能是由于这些天然水体中存在额外的水质成分所致。这项研究的发现表明,当从淡水迁移到开放水域时,DOM以外的多个变量控制着COS和CS 2的光产生。
更新日期:2020-09-23
中文翻译:
阳光下光解过程中溶解的有机物对半胱氨酸中羰基硫和二硫化碳形成的影响。
羰基硫(COS)和二硫化碳(CS 2)是重要的大气气体,当暴露于阳光下时,它们是由天然水中存在的有机硫前体形成的。但是,尚不清楚特定的水成分(例如溶解的有机物(DOM))如何影响COS和CS 2的形成。为了更好地理解DOM的作用,在含有O 4的合成水中进行了辐照实验,该合成水包含四种不同的DOM分离物(从淡水获取到开放的海洋资源)以及基于硫的氨基酸半胱氨酸(CYS)。CYS是COS和CS 2的已知天然前体。结果表明,尽管对动力学模式影响很小,但COS的形成随DOM类型变化不大。COS的形成也随着CYS浓度的增加而增加,但随着DOM浓度的增加而减少。淬火实验表明,˙OH不参与COS形成的限速步骤,而DOM的激发三重态(3 CDOM *)可能与之相关,尽管用于除去3 CDOM *的淬灭剂可能已与CYS反应衍生的中间体。在任何实验条件下均未形成CS 2。总体而言,含DOM的合成水对形成COS和CS 2的影响有限,尤其是与先前检查过的在日光照射的天然水中形成的较高浓度相比时。这种局限性作用背后的原因有待进一步探讨,但可能是由于这些天然水体中存在额外的水质成分所致。这项研究的发现表明,当从淡水迁移到开放水域时,DOM以外的多个变量控制着COS和CS 2的光产生。