Isotope Chemistry for the Studies on COS・DMS Generating Mechanism and Their Behavior in Environment

羰基硫（COS）是由土壤中的微生物如排硫硫杆菌在硫氰酸盐存在下产生的。另一方面，二甲基硫化物（DMS）是由海洋中的藻类产生的，化合物中的硫来自海水硫酸盐。在这两种情况下，微生物使用无机硫来产生COS和DMS。为什么不用有机硫？为了阐明这个问题，通过在培养基中加入有机硫化合物来检查COS和DMS的实验生成。在通过添加芳基异硫醚作为有机硫来培养排硫硫杆菌的情况下，微生物没有繁殖。DMS花了很长时间才找到在实验室中有效繁殖的藻类。实验证明，Cricosphaera roscoffensis NIES 8和Alexandrium catenella NIES 677在海水介质中会产生DMS，确定化合物中硫来源的主要方法是同位素（^<32>S/^<34>S）测量。对于同位素测量，研究了COS和DMS的收集方法。COS被引入到乙烷中，加入Zn（CH_3COO）_2生成ZnS，ZnS转化为Ag_2S。以二氧化钛为光催化剂，硅胶为载体，吸附DMS，紫外光（350 ~ 380 nm）照射，得到DMS的光催化活性。将生成的SO_2通入双氧水中氧化为SO_4 ~（2-）<-2>，最后转化为Ag_2S。对上述Ag_2S生成的SO_2进行了硫同位素测定。微生物代谢对COS同位素分馏有一定影响。硫<34>氰酸盐硫的δ^ S值（6.1‰）降低到3.8‰。这一结果对探讨硫在环境中的行为具有一定的参考价值。

Carbonyl sulfide(COS) is produced by microbes such as Thiobacilius thioparus under the presence of thiocyanates in soil. On the other hand dimethly sulfide(DMS) is produced in the sea by algae and the sulfur in the compound comes from the sea water sulfate. In both cases microbes use inorganic sulfur to generate COS and DMS. Why they don't use organic sulfur? To elucidate this problem the experimental generation of COS and DMS were examined by adding organic sulfur compounds in the medium. In the case of cultivating Thiobacillus thioparus by adding aryl isothianate as organic sulfur, microbes did not breed. For DMS it took long times to find algae which breed effectively in the laboratory. Cricosphaera roscoffensis NIES 8 and Alexandrium catenella NIES 677 were recognized to generate DMS in the sea water medium experimentally.The predominant means to identify the origin of sulfur in the compounds is isotopic (^<32>S/^<34>S) measurement. For the isotopic measurement the collection method of COS and DMS were investigated. COS was introduced in ethane, added by Zn(CH_3COO)_2 to form ZnS which is converted to Ag_2S. DMS was adsorbed on silica gel with titanium oxide photo catalyst which is then irradiated by ultraviolet ray(350〜380nm). The formed SO_2 is introduced to hydrogen peroxide solution to be oxidized to SO_4^<-2> which is finally converted to Ag_2S. The sulfur isotopic measurement is carried out for SO_2 formed from Ag_2S described above. For COS isotopic fractionation by microbe metabolism was observed. δ^<34>S value (6.1‰) of thiocyanate sulfur as a standing material went to be lower as 3.8‰. This result is expected to be useful for the discussion of behavior of environmental sulfur.