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1.
Photo-oxidation of dimethylsulphide in aqueous solution 总被引：2，自引：0，他引：2
Dimethylsulphide (DMS) is readily photo-oxygenated in the presence of micromolar amounts of photosensitizers such as methylene blue, rose bengal, anthroquinone and humic acid. Two moles of DMS are oxidized for every mole of molecular oxygen utilized consistent with dimethyl-sulphoxide being the oxidation product. Coastal seawater samples examined contained sufficient naturally occurring photosensitizer to photo-oxygenate DMS in sunlight with a first order rate constant of 2.4 × 10−5 s−1. This rate is rapid enough to imply that DMS is oxidized at approximately the same rate as it is lost to the atmosphere. 相似文献
2.
Aerated solutions of potassium iodide in de-ionised water, of between 5–20% (w/v), were exposed to ambient spring sunlight to estimate the rate of photochemical production of molecular iodine from iodide and oxygen in seawater. This rate cannot be measured directly as other reactions, for example the reduction of molecular iodine by organic matter, interfere. Also, a parallel photo-oxidation, initiated by organic matter in real seawater, may also occur. The experiments yield a half-life for iodide in tropical surface waters of about 29 months suggesting that the reaction is insignificant. At this rate it will not compete effectively against the reduction of molecular iodine by organic matter, and hence molecular iodine should not appear. The experiments also consider the photo-oxidation by nitrate, and iodate, a combination of nitrite and oxygen, and eliminate significant interference by chloride, bromide and the phosphate buffer. The rate of photo-oxidation with each of the first three oxidations is found to be first order with respect to oxidant concentration. The variation of photo-oxidation rate with pH is also studied, with a brief investigation without conventional oxidant, where electron cage complexes still promote photo-oxidation. The photochemical action spectrum for these reactions in sunlight is shown to extend between 300 and 425 nm. The photo-oxidation of iodide by iodate is more interesting to marine chemistry as the photo-reduction of iodate. Nevertheless, the reduction-rate is judged to be several orders too low to be significant in seawater. The mechanism of the reactions are discussed and lessons drawn on the stability of potassium iodide solutions used in iodate analysis. The KI actinometer is recommended to those studying other photochemical systems activated by UV-A light as it is linear and very simple and reliable. 相似文献
3.
《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(1):136-153
The influence of solar radiation on springtime rates of photochemical and biological consumption of dimethylsulfide (DMS) in surface waters from the western Atlantic Ocean was examined by exposing 0.2 μm filtered and unfiltered surface seawater to natural sunlight at five depths in the upper 30 m. Parallel deck incubations of 0.2 μm filtered seawater under various long-pass optical filters were also carried out to aid in assessing the wavelength dependence of DMS photolysis. DMS photolysis rate constants for mid-day exposure (∼10:30–17:30 local time) to surface irradiance ranged from 0.026 to 0.086 h−1 and were highest in coastal and shelf waters. Photolysis rate constants decreased with increasing irradiation depth, in accordance with the attenuation of ultraviolet radiation (UVR, 280–400 nm). Total DMS consumption rates (photochemical+biological) in unfiltered surface samples also decreased with increasing incubation depth and were larger than photolysis rates at nearly all depths and all stations. The decrease in photolysis rate constants with exposure depth was mirrored by biological DMS consumption rate constants that were severely inhibited at surface irradiances, and approached or exceeded dark rate constants at deeper exposure depths. Photolysis rates were 2–19 times greater than estimated biological consumption rates in the surface light exposed samples, while biological consumption rates were significantly larger than photolysis rates at incubation depths below the 1% light level for UV–B radiation (280–320 nm). Total DMS loss rates increased up to nine-fold with UVR exposure, but changes in DMS concentrations were not strongly correlated to light dose, presumably due to parallel, light-mediated DMS production processes. The primary loss process for DMS depended mainly on the depth interval considered and the attenuation of UVR; in general, photochemical removal dominated shallow layers characterized by high UV–B intensities, whereas biological removal dominated in deeper layers where UV–B was absent, but UV–A (320–400 nm) and visible (400–700 nm) light fluxes were still relatively high. These results demonstrate that UVR exposure significantly influences the spatial and temporal pattern of DMS production and loss processes, and ultimately the DMS flux to the atmosphere. 相似文献
4.
二甲基亚砜(DMSO)是海水中的主要溶解态甲基硫化物,DMSO在二甲基硫(DMS)的生物地球化学循环中起着重要的作用。它能通过DMS的光化学氧化和细菌氧化生成,可作为DMS的1个汇,也可以通过生物直接合成或其它途径产生。DMSO同时又可以被酶、细菌、植物等还原为DMS,因此,DMSO又可充当DMS的1个源。DMSO除了能被还原为DMS外,还可能会被细菌氧化为SO42-,在氯过氧化物酶作用下被H2O2氧化为DMSO2等。海洋中DMSO的测定通常采用还原剂NaBH4将其还原为DMS后,再利用气相色谱进行测定。海水中DMSO的分布不均匀,高浓度区是那些温度较高,光照充足、浮游植物较多、生物活性较高的表层水或近岸水。 相似文献
5.
亚甲基蓝在水体系中的光化学降解研究 总被引：1，自引：0，他引：1
研究水体系中亚甲基蓝的光化学降解.结果表明,在高压汞灯照射下,亚甲基蓝在人工海水中降解得最快,蒸馏水次之,而在天然海水中降解得最慢.通过对比研究发现.重金属离子(Cu2+,Zn2+,Cd2+,Hg2+)和腐殖酸能够在一定程度上抑制亚甲基蓝的光降解;而丙酮能促进亚甲基蓝的光降解.由此可见,重金属离子和腐殖酸可能是造成亚甲基蓝在天然海水中降解缓慢的主要因素之一. 相似文献
6.
二甲基硫的海洋化学研究 总被引：2，自引：1，他引：1
二甲基硫（ＤＭＳ） 是海洋排放到大气中的最主要的生源硫化物。作者综述了ＤＭＳ在海洋中的分布特征、影响ＤＭＳ转化的因素、ＤＭＳ的海空扩散及其对环境的影响等。ＤＭＳ在海洋中存在很大程度的时空变化,这一变化不仅与海洋初级生产力水平有关,而且还与浮游植物的种类组成密切相关。微生物的降解、光化学的氧化以及海空扩散是ＤＭＳ在海洋中迁移变化的三个最重要的途径。ＤＭＳ的海－ 空扩散也存在较大的时空变化。ＤＭＳ的释放会对全球的气候变化和酸雨的形成产生重要的影响。本文同时就国内外的研究现状和今后的研究方向进行了分析和总结。 相似文献
7.
海洋石油光化学降解的研究 总被引：1，自引：0，他引：1
石油进入海水会发生各种物理、化学变化,以往的研究已证明光化学氧化在石油及其精炼产品风化过程中具有重要意义.光化学氧化机理主要在于接受日光照射的能量,以不同的方式与溶解氧结合,从而最终降解石油烃.生成的光氧化产物一般为羧酸、醇、醚、羰基化合物等几类,还有一些产物尚不能确定其结构.光氧化产物仍然存在毒性,对海洋生物等十分有害.在动力学方面,针对其某一组分已证实为一级反应动力学行为,并定量地得出了速率常数.光降解速率会受到光照条件、溶解氧、金属离子等因素的影响.目前的研究表明,对石油光化学进行深入探讨具有较高的研究价值和现实意义. 相似文献
8.
A chemoreduction-purge-and-trap gas chromatographic method has been developed for the determination of trace dimethylsulfoxide (DMSO) in seawater. In the analysis procedure, DMSO was first reduced to dimethylsufide (DMS) by sodium borohydride and then the produced DMS was analyzed using the purge-and-trap technique coupled with gas chromatographic separation and flame photometric detection. Under the optimum conditions, 97% DMSO was reduced in the standard solution samples with a standard deviation of 5% (n=5). The detection limit of DMSO was 2.7 pmol of sulfur, corresponding to a concentration of 0.75 nmol/L for a 40 ml sample. This method was applied to determine the dissolved DMSO (DMSOd) and particulate DMSO (DMSOp) concentrations in the surface seawater of the Jiaozhou Bay, and the results showed that the DMSOd and DMSOp concentrations varied from 16.8 to 921.1 nmol/L (mean:165.2 nmol/L) and from 8.0 to 162.4 nmol/L (mean:57.7 nmol/L), respectively. The high concentrations of DMSOp were generally found in productive regions. Consequently, a significant correlation was found between the concentrations of DMSOp and chlorophyll a, suggesting that phytoplankton biomass might play an important role in controlling the distribution of DMSOp in the bay. Moreover, in the study area, the concentrations of DMSOd were significantly correlated with the levels of DMS, implying that the production of DMSOd is mainly via photochemical and biological oxidation of DMS. 相似文献
9.
The tendency of dimethylsulfide (DMS) to form complexes with heavy metal ions in aqueous solutions and the factors that influence
it have been investigated. Among five heavy metal ions examined (Cu2+, Cd2+, Zn2+, Pb2+ and Hg2+), only Hg2+ bound significantly with DMS in aqueous solutions in which Hg2+ concentration was increased to much higher levels than that of natural seawater. The complexation capacity of Hg2+ for DMS was influenced by pH and media. The affinity of Hg2+ for DMS was generally lower at high than at low pH, presumably due to the competition of hydroxide ion to form hydroxomercury
species. In different solutions, the affinity of Hg2+ for DMS followed the following sequence: ultra-purified water > 35‰ NaCl solution > seawater. It seems apparent that chloride
had a negative impact on the complexation of DMS by Hg2+, owing to the competition of chloride with DMS for complexing Hg2+. In addition, the affinity of Hg2+ for DMS in the bulk seawater appeared to be higher than that in the surface microlayer seawater. The tendency of Hg2+ to form complexes with DMS in aqueous solution can be reduced by the presence of 2 mM amino-acid such as glycine, alanine,
serine and cysteine, as these ligands give stable mercury complexes. However, the presence of 2 mM acetate in experimental
solutions had no significant effect on the complexation of Hg2+ with DMS, even though this ligand has a relatively strong complexing capacity for Hg2+. Although mercury ions appeared to have a strong affinity for DMS, the concentration of mercury in seawater is too low to
produce a great effect on the distribution of DMS in oceans. 相似文献
10.
Pentachlorophenol (PCP) and 3,4-dichloroaniline (DCA) were used as models to examine photochemical reactions in seawater.The photolysis of PCP in seawater differed in both rate and product distribution from that in distilled water; rates were slower in seawater due to the photonucleophilic interaction of PCP with chloride ions, demonstrated by the formation of 36Cl-labeled PCP in irradiated PCP solutions containing Na36Cl. DCA showed no rate change and gave identical products in both systems. Both PCP and DCA yielded greater amounts of photoreduction products in seawater than in distilled water, and tetrachloromuconic acid was isolated and identified as a new and unstable PCP photoproduct resulting from ringfission. This study demonstrates the operation of photooxidation, photonucleophilic substitution, and photoreduction reactions which differ in detail between seawater and distilled water and suggests that photochemical reactions can be a major factor in the breakdown of organic pollutants and other chemicals in the marine environment. 相似文献
11.
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12.
《Deep Sea Research Part I: Oceanographic Research Papers》2000,47(2):177-192
The concentration of dimethylsulfide (DMS) and supporting parameters were determined in surface seawater and vertical profiles at 26 stations in the South China Sea. The concentrations of DMS in surface seawater ranged from 61 to 148 ng S/l, with a mean of 82 ng S/l. High concentrations of DMS were found in the productive regions. The vertical profiles of DMS were characterized by a maximum at depths typically between 20 and 75 m. The concentrations of DMS were correlated with the levels of chlorophyll a both in the surface seawater and in the vertical distribution. The concentrations of DMS were higher than expected for this chlorophyll-poor tropical sea, as indicated by markedly high DMS (ng S/l)/chlorophyll a (μg/l) ratios ranging from 315 to 3524 with a mean of 1768 for all the surface seawater samples. DMS concentration was significantly correlated with seawater temperature and dissolved oxygen, but it showed an inverse relationship to nutrients (including nitrate, phosphate and silicate). On the basis of sea surface concentrations of DMS and gas exchange calculations, the mean flux of DMS from the South China Sea to the atmosphere was estimated to be 5.5 μmol m−2 d−1. 相似文献
13.
黄、渤海二甲基硫化物的浓度分布与迁移转化速率研究 总被引：2，自引：1，他引：1
于2015年8-9月对黄、渤海海域进行现场调查，研究了海水中二甲基硫（DMS）、β-二甲巯基丙酸内盐（DMSP）、二甲亚砜（DMSO）的浓度分布、相互关系及影响因素，测定了DMS的生物生产与消耗、光化学氧化和海-气扩散速率，对DMS的迁移转化速率进行综合评价。结果表明:表层海水中DMS、溶解态DMSP（DMSPd）、颗粒态DMSP（DMSPp）、溶解态DMSO（DMSOd）和颗粒态DMSO（DMSOp）浓度的平均值分别为（6.12±3.01）nmol/L、（6.03±3.45）nmol/L、（19.47±9.15）nmol/L、（16.85±8.34）nmol/L和（14.37±7.47）nmol/L，整体呈现近岸高远海低，表层高底层低的趋势。DMS、DMSPd和DMSOp浓度与叶绿素（Chl a）浓度存在显著的相关性。表层海水中DMS光氧化速率顺序为:kUVA > kUVB > k可见，其中UVA波段占光氧化的70.8%。夏季黄、渤海微生物消耗、光氧化及海-气扩散对DMS去除的贡献率分别为32.4%、34.5%和33.1%，表明3种去除途径作用相当。黄、渤海DMS海-气通量变化范围为0.79~48.45 μmol/（m2·d），平均值为（11.87±11.35）μmol/（m2·d）。 相似文献
14.
对海水中锰的光化学反应及其影响因素进行了研究.实验结果表明,锰的光化学反应主要通过有机物为媒介进行,反应液中加入的有机物种类和浓度的改变会导致锰的光化学反应速率的改变.增加光强,有利于锰的光还原反应的进行.降低体系的pH值,可提高锰的光反应速率.锰在不同介质中光反应速率从大到小的顺序为:去离子水、人工海水、天然海水.此外,搅拌有利于锰的光反应的进行,但在体系分布已达均匀的前提下,搅拌速率的大小对锰的光反应速率几乎无影响.研究表明,通过光化学反应,海水中的锰会由四价的颗粒态转化为二价的可溶态,从而有利于浮游植物的吸收和生长. 相似文献
15.
利用静水密闭式呼吸仪,测定了不同温度（10、12、……、30℃）条件下褐菖鼬（Sebastiscus marmoratus）幼鱼耗氧率和排氨率变化．结果表明,温度对幼鱼耗氧率和排氨率均有显著影响（P〈0．05）．温度10～30℃,幼鱼耗氧率、排氨率变化范围分别为0．02～0．30mg／（g·h）和2．64～10．01ug／（g·h）,温度26、16℃时耗氧率和排氨率分别上升至峰值,分别为最小值10℃组的15．00、3．79倍;温度（F）对幼鱼耗氧率R0[mg／（g·h）]和排氨率RN[ug／（g·h）]的影响可分别用多项式表示：R0=-2．00×10^-5 T4＋1．50×10^-3 T3-3．69×10^-2 T2＋0．3978T-1．5376,R2=0．988和RN=3．00×10^-5 T6 -4．00×10^-3 T5＋0．1996 T4-5．1111T3＋70．817T2-501．10T＋1415．80,R2=0．964;幼鱼的氨熵变化范围为0．02～0．19,其蛋白质供能比变化范围为5．64％～56．65％,平均蛋白质供能比为22．56％;各温度跨度代谢率Q10值均值为4．02,18～28℃代谢率Q10值为2．81±0．09与鱼类平均Q10值较接近;各温度跨度组排泄率Q10均值为0．93,对比同一温度跨度组代谢率和排泄率Q10值,代谢率Q10值均大于排泄率Q10值两倍以上,最大组间相差达7倍．因此,幼鱼能量消耗的供能物质以脂肪和碳水化合物为主,蛋白质为辅．此外,温度变化对幼鱼代谢的影响程度明显大于对排泄的影响,且其适宜生长温度为18～28℃． 相似文献
16.
Three methods for the determination of dissolved organic carbon in seawater were compared. Samples were analysed using persulphate oxidation, high-temperature combustion, and ultraviolet photo-oxidation. The dissolved organic carbon content of the seawater samples ranged from 0.6 to 1.6 mg C/I. This study shows that results of high-temperature oxidation and photo-oxidation procedures differ by less than 5%, whereas results with persulphate oxidation are about 15% less than those obtained with the high-temperature oxidation. The relative merits of each of the oxidation techniques for the determination of organic matter in seawater are discussed. 相似文献
17.
18.
海洋中二甲基硫的生物生产与消费过程 总被引：4，自引：0，他引：4
DMS是海洋中最主要的挥发性有机硫化物,对全球气候变化和环境酸化产生重要影响。DMS的生物生产与消耗主要发生在海洋真光层。生物的生产与消耗被认为是海洋中DMS的主要来源和去除途径。海洋中DMS的生物生产和消耗是密切相关的,两者的速率基本保持平衡。目前,有关DMS生物生产与消费速率的测定方法有放射性同位素示踪和加抑制剂2种,后者颇受青睐,不过有关抑制机理还需进一步的研究。 相似文献
19.
分别采用硫酸过硫酸钾作为氧化剂进行高压消解和用浓度为1 mol/dm3盐酸浸泡提取,然后用磷钼蓝分光光度法测定海水悬浮颗粒物、沉积物中的总磷和无机磷,用差减法得到有机磷。悬浮颗粒物总磷(PTP)和无机磷(PIP)质量浓度分别为(632.4～651.7)×10-6和(436.6～452.6)×10-6时,其相对标准偏差小于1.44%。悬浮颗粒物总磷、无机磷和有机磷的回收率分别为97.2%～101.3%,97.8%～100.4%和97.3%～102.3%。所建立的分析方法可用于海水、河口水悬浮颗粒物及沉积物中不同形态磷的测定。 相似文献
20.
本文在黄渤海海域对β-二甲基巯基丙酸内盐(DMSP)降解产生丙烯酸和丙烯酸的降解过程做了初步研究。结果表明,海水中有明显的DMSP降解和丙烯酸的生成现象。在DMSP降解初期,DMSP不断降解,丙烯酸则在经过1h后浓度开始上升,达到最大值后再次下降。起始DMSP浓度越高,降解得越完全,且丙烯酸最大值越大。在观测的5h内,丙烯酸的表观降解速率总是大于DMSP的表观降解速率,且两者都与初始浓度成正相关。在丙烯酸的降解过程中,黑暗条件下起始浓度越大,丙烯酸变化速率越大,而光照条件下则恰好相反。光化学反应中前2h表现为丙烯酸的光化学生成,而后2h表现为光化学降解。 相似文献