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首页> 外文会议>NATO Advanced Research Workshop on Global Atmospheric Change and its Impact on Regional Air Quality >The Photochemical Degradation of Chloral and Oxalyl Chloride
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The Photochemical Degradation of Chloral and Oxalyl Chloride

机译：氯和草氯的光化学劣化

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The major source of chloral, CCl_3CHO in the atmosphere is from the degradation of 1,1,1-trichloroethane, methyl chloroform, (Nelson et al., 1990, Platz et al., 1995). In comparison, direct emissions of chloral from its use as a feedstock chemical are negligible. While methyl chloroforms was formerly widely used as a solvent, it is now strictly regulated as an ozone-depleting substance under the Montreal Protocol. As a consequence, estimates of annual global emissions have fallen by approximately 95% over the last 10 years (Midgeley and McCulloch, 1999). These calculations are borne out by recent observations of atmospheric background concentrations of methyl chloroform (Montzka et al, 1999). Methyl chloroform degrades mainly by reaction with the hydroxyl radical in the troposphere to give chloral (～85%) with minor contributions from hydrolysis in the oceans (～5%) and destruction in the stratosphere (～10%) (Cox, 1998). Chloral is expected to have a relatively short atmospheric lifetime due to its loss via reaction with the OH radical, UV photolysis and wet deposition (Nelson et a.l, 1990, Platz et al., 1995, Rattigan et al., 1993, Barry et al., 1994, Sidebottom and Franklin, 1996, Rattigan et al., 1998, Talukdar et al., 2001). It has generally been assumed that the major tropospheric loss process for chloral is by photolysis. This suggestion is based on the UV absorption cross sections of chloral and an assumed quantum yield for photodissociation of unity (Rattigan et al., 1993, Sidebottom and Franklin, 1996, Rattigan et al., 1998). This work is concerned with a determination of the quantum yields for photodissociation of CCl_3CHO and for formation of the resulting products under atmospheric conditions.
机译：氯醛的主要来源，在CCl_3CHO大气是从1,1,1-三氯乙烷，甲基氯仿，（Nelson等人，1990，广场等人，1995）的降解。相比较而言，其作为原料化学品的使用三氯乙醛直接排放可以忽略不计。而甲基chloroforms以前广泛用作溶剂，现在是严格规定为根据蒙特利尔议定书的臭氧消耗物质。因此，每年全球排放量的估计有大约95％在过去的10年（Midgeley和麦卡洛克，1999年）下降。这些计算由最近甲基氯仿的大气背景浓度（Montzka等人，1999）的观察结果所证实。甲基氯仿降解主要是由与从水解在海洋次要贡献（〜5％）和破坏平流层中的（〜10％）（考克斯，1998）中的羟基在对流层中，得到氯醛（〜85％）的自由基反应。三氯乙醛预期具有相对短的大气寿命，由于经由与OH自由基，UV光解和湿沉积（Nelson等人，1990，广场等人，1995，Rattigan等人，1993，Barry等反应其损耗，1994，Sidebottom和Franklin，1996，Rattigan等人，1998，塔卢克达尔等人，2001）。它通常被认为对三氯乙醛的主要对流层减肥过程是通过光解。这个建议是基于氯醛的UV吸收截面和用于统一的光解的假定量子产率（Rattigan等人，1993，Sidebottom和Franklin，1996，Rattigan等人，1998）。这项工作涉及的量子产率为CCl_3CHO的光解和用于形成大气条件下所得到的产品的的确定。

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