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Biological degradation of ethanol in Southern California coastal seawater
Marine Chemistry ( IF 3 ) Pub Date : 2019-10-05 , DOI: 10.1016/j.marchem.2019.103703
Warren J. de Bruyn , Catherine D. Clark , Mary Senstad , Natalie Toms , Aaron W. Harrison

The increased use of ethanol as an additive in gasoline is expected to increase atmospheric ethanol levels. Understanding future impacts requires an understanding of the current atmospheric ethanol budget. Air-sea exchange is one of the largest sources of uncertainty in budget estimates. Understanding processes that produce or destroy ethanol in seawater will help constrain air-sea exchange estimates. The rate of biological consumption of ethanol in seawater was measured in Southern California surface coastal water sampled from a tidally flushed river mouth over a six-month period. First-order rate constants (k) for biological degradation of approximately ambient ethanol levels of 89 nM ranged from zero to 1.9 ± 0.1 × 10−2 min−1 with an average of 3.8 ± 5.9 × 10−3 min−1 (n = 20). This corresponds to an average biological turnover time (1/k) of approximately 4.4 h or an average biological half-life (0.693/k) of approximately 3 h. There were several rain events over this time period resulting in flow from upstream in the river; these were associated with increased bacterial levels, higher absorption coefficients and reduced salinity. Rate constants, in general, increased with the number of bacterial colony forming units in the water sample. Excluding the two rate constant maxima events the background biological degradation rate constant in the absence of rain/bacteria input from upstream, is 1.3 ± 1.0 × 10−3 min−1. This corresponds to an average biological turnover time of approximately 13 h and an average biological half-life of approximately 9 h. Autoclaved samples (to remove bacteria) showed no measurable ethanol degradation, suggesting that chemical loss processes are not significant.



中文翻译:

南加州沿海海水中乙醇的生物降解

乙醇作为汽油添加剂的增加使用有望增加大气中乙醇的含量。了解未来的影响需要了解当前的大气乙醇预算。海海交换是预算估计中最大的不确定性来源之一。了解在海水中产生或破坏乙醇的过程​​将有助于限制空气与海洋之间的交换估计。在六个月的时间里,从潮汐冲刷的河口采样的南加州地表沿海水中测量了海水中乙醇的生物消耗率。生物降解大约89 nM的周围乙醇水平时的一级速率常数(k)为零至1.9±0.1×10 -2  min -1,平均为3.8±5.9×10 -3 最小-1n  = 20)。这对应于约4.4 h的平均生物转换时间(1 / k)或约3 h的平均生物半衰期(0.693 / k)。在此期间,发生了几场降雨事件,导致河流上游流入。这些与细菌水平增加,吸收系数更高和盐度降低有关。通常,速率常数随水样中细菌菌落形成单位的数量而增加。排除这两个速率常数最大值事件,在没有上游雨水/细菌输入的情况下,本底生物降解速率常数为1.3±1.0×10 -3  min -1。这对应于大约13小时的平均生物学更新时间和大约9小时的平均生物学半衰期。高压灭菌的样品(去除细菌)显示没有可测量的乙醇降解,表明化学损失过程并不重要。

更新日期:2019-10-05
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