| The fate of sulfur-containing compounds constituted one of today's public environmental concerns since they have great influences to the global environment and the climate change. In order to understand the removal and travel process of sulfur-containing compounds in atmospheric aqueous phase and natural waters, their reactions with oxidative radicals were studied in the solutions on molecular level, as well as the contribution to sulfur-containing compounds transformation. Nanosecond laser flash photolysis transient absorption spectroscopic technique was employed to investigate the microscopic reaction mechanisms of CS2, H2S, DMS and DMSO with·OH,·SO4-,·NO3 radicals.Based on the spectra and kinetic analysis, the reaction products were attributed and the rate constants were acquired. Moreover, the influence of pH, oxygen and temperature in the waters on the oxidation of sulfur-containing compounds was studied. These studies have provided direction evidence for the assessment of sulfur-containing compounds' contribution to the global sulfur cycle. The photochemical reactions of mixed solutions and the cross pollution were then studied. The 355 nm laser photolysis of CS2 and HONO mixed aqueous solution leaded to the production of CS2OH·HONO. Cross-reaction may greatly influence the transformation of sulfur and nitrogen. Our experimental results showed that the lifetime of CS2OH·HONO was about 0.1 ms, which meant that it could damage the health of humans if it entered their bodies.Meanwhile, the secondary pollutants from the oxidation of sulfur-containing compounds such as CS2OH,·HS,·DMSOH, (DMS)2+,·DMSOOH, CS2+ cation and CS2OH·HONO were intensively studied. The kinetic parameters and the chemical behavior of these secondary pollutans in the waters were disscussed together with the removal pathway and the final products. The CS2+ cation and CS2OH·HONO adduct were reported for the first time.Based on the experimental results, the following points could be drawn. (1)In aqueous phase, CS2 reacts with·OH radical to form CS2OH adduct with the rate constant (1.02±0.07)x1010 L·mol-1·s-1 at 294.0 K and the activated energy calculated to be (26.91±0.90) kJ·mol-1. CS2OH and CS2O- are conjugated acid-base pair in solutions and the equilibrium constant is 4.9. The absorptions of CS2OH and CS2O- both lie in 230-300 nm, with the peak absorptions of CS2OH at 230 nm and CS2O- at 280 nm. Decomposition of CS2OH and CS2O yields COS and·HS/·S-. Oxygen has no influence to the formation of CS2OH, but will speed its decomposition. Reaction of CS2 with·SO4- radical in aqueous phase undergoes a charge-transfer process, and yields CS2+ cation with the rate constant (4.27±0.15)×107 L·mol-1·s-1. At pH＞0, CS2+ hydrates to form CS2OH. CS2 does not react with·NO3 radical in acetonitrile.(2)In aqueous phase, 266 nm laser photolysis of HS yields·HS radical. Meanwhile, the reaction of·OH radical with H2S also yields·HS radical, and the rate constant is (1.30±0.30)×1010 L·mol-1·s-1. The absorption of·HS radical lies in 220-320 nm, with a peak absorption at 240 nm, two shoulder absorption at 270 nm/310 nm.·HS radical furtherly reacts with O2 to yield SO2 in aqueous phase, with the rate constant (3.07±0.31)×108 L·mol-1·s-1, while in gas phase·HS radical dose not react with O2. This study shows that, in the process of aqueous H2S oxidation, the rate constant of·HS radical formation is very fast, and its further oxidation is the rate dominated step.(3)·OH radical reacts with DMS to form·DMSOH in aqueous phase, and the rate constant is (2.70±0.10)×1010 L·mol-1·s-1.·DMSOH further reacts with DMS to form (DMS)2+, which has the absorption peak at 480 nm. Both·SO4 and·NO3 radicals oxidate DMS directly to form DMS+, with the rate constants (2.60±0.20)×1010 L·mol-1·s-1 and (1.60±0.10)×1010 L·mol(-1)·s-1 respectively. DMS+ also reacts with DMS to form (DMS)2+. The main removal pathway of (DMS)2+ is to react with OH-, and the product is DMSO, which means that alkaline condition favors the oxidation of DMS. Oxygen dose not influence the oxidation of DMS, which is different with that in gas phase.(4)·OH radical reacts with DMSO to form·DMSOOH in aqueous phase, which has no obvious UV-vis absorbance..DMSOOH decomposes to yield CH3SOOH and·CH3 radical, and·CH3 radical will further react with O2 to form·CH3O2 radical.·SO4 radical oxidates DMSO directly to form DMSO+ with the absorption peak at 290 nm, and the rate constant (2.84±0.29)×109 L·mol-1·s-1. When pH is more than 9, DMSO+ is stable, however, when pH is less than 9, it will hydrolyze quickly to form·DMSOOH radical. Reaction of·NO3 with DMSO leads to the formation of·DMSONO3 adduct mainly, with the absorption peak at 440 nm, and the rate constant (1.5±0.1)×109 L·mol-1·s-1.(5)355 nm laser photolysis of CS2 and HONO mixed solution first leads to the formation CS2OH, which successively reacts with HONO to form CS2OH·HONO adduct. The formation rate constant is (2.79±0.05)×108 L·mol-1·s-1 at 293.0 K, and the decay rate constant is 1.02×104 s-1·CS2OH·HONO has wide absorption in the range of 200 to 1000 nm, and the main absorption peaks are at 230 nm, 280 nm, 305 nm, 475 nm, 490 nm, 930 nm and 970 nm. However, 355 nm laser photolysis of CS2 and NaNO2 mixed solutions only leads to the formation of CS2O- with the rate constant of (1.38±0.05)×109 L·mol-1·s-1.
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