Comment on "Early Archaean microorganisms preferred elemental sulfur, not sulfate"

Philippot et al. (Reports, 14 September 2007, p. 1534) interpreted multiple-sulfur isotopic compositions of approximately 3.5-billion-year-old marine sulfide deposits as evidence that early Archaean microorganisms were not sulfate reducers but instead metabolized elemental sulfur. However, their data can be better explained by a scenario involving poor mixing of photochemical and surface sulfide sources.     

Large sulfur isotope fractionation does not require disproportionation

The composition of sulfur isotopes in sedimentary sulfides and sulfates traces the sulfur cycle throughout Earth's history. In particular, depletions of sulfur-34 ((34)S) in sulfide relative to sulfate exceeding 47 per mil (‰) often serve as a proxy for the disproportionation of intermediate sulfur species in addition to sulfate reduction. Here, we demonstrate that a pure, actively growing culture of a marine sulfate-reducing bacterium can deplete (34)S by up to 66‰ during sulfate reduction alone and in the absence of an extracellular oxidative sulfur cycle. Therefore, similar magnitudes of sulfur isotope fractionation in sedimentary rocks do not unambiguously record the presence of other sulfur-based metabolisms or the stepwise oxygenation of Earth's surface environment during the Proterozoic.     

Origins of sulfur in coal: importance of the ester sulfate content of peat

The sulfur found in coal stems in large part from sulfur incorporation at the peat-forming stage. Ester sulfate (a carbon-oxygen-sulfur linkage) is a major contributor to the sulfur in peat and thus is an important determiner of the quantity and forms of sulfur eventually found in coal.     

纤维素分解菌的分离鉴定及生物学特性研究

对从土壤中分离到的4株纤维素分解细菌菌1、菌2、菌3、菌4进行生物学特征研究.4种菌株都能分解稻草和滤纸,其中菌1对稻草和滤纸的分解能力最强,分解效率分别为35.11%和26.15%.4种菌株在NaNO3、(NH4)2SO4作为氮源时生长缓慢且酶活力低,而在蛋白胨作为氮源时酶活力则达到较高水平.菌1、菌2、菌3、菌4产生纤维素酶的最适温度分别为28、20、28、40 ℃.4株纤维分解菌产生纤维素酶的最适pH值为6～7.菌1与荧光假单胞菌(Pseudonomas fluorescens)16S rDNA核苷酸同源率为99.2%.根据形态学、生理生化检测以及16S rDNA核苷酸序列分析结果,鉴定菌1是荧光假单胞菌.     

秸秆还田配施硫肥对春玉米产量及硫素积累、分配特性的影响

目的 研究秸秆还田配施硫肥对春玉米产量及硫素的积累、分配与转运的影响,为探明硫在春玉米中的积累转运规律及合理施用硫肥提供理论依据。方法 试验采用双因素裂区设计,主区包括秸秆还田和秸秆不还田2个水平,副区包括配施硫肥和不配施硫肥2个水平,共有CK(不施任何肥料)、秸秆不还田不施硫、秸秆不还田施硫、秸秆还田不施硫和秸秆还田施硫5个处理。通过田间试验,探讨秸秆还田配施硫肥对春玉米各器官中硫素的积累、分配与转运的影响。结果 秸秆还田配施硫肥对春玉米有一定的增产作用,秸秆还田施硫的玉米产量比秸秆还田不施硫提高11.98%,比秸秆不还田不施硫提高20.34%。秸秆还田配施硫肥可显著提高春玉米植株硫素的积累量,秸秆还田施硫的硫素积累量比秸秆不还田施硫提高13.37%,比秸秆不还田不施硫提高52.67%。施硫可以提高玉米植株各器官中的硫素积累量,施用硫肥的硫素积累量比不施硫肥平均提高36.07%,各器官硫素积累量整体表现为籽粒>叶片>茎秆>穗部营养体。秸秆还田施硫的硫素总转运量最高,达到15.29 kg·hm^?2,比秸秆不还田不施硫提高74.54%,硫素转运量对籽粒总贡献率提高17.27%。结论 秸秆还田配施硫肥可以促进春玉米的硫素积累以及玉米植株营养器官中硫素向籽粒的转运,并最终提高春玉米产量。     

喷施硫酸锰和硫酸锌对小麦籽粒镉锰锌生物可给性的影响

为探明喷施叶面肥对小麦镉（Cd）污染健康风险的影响,通过大田试验,采用体外模拟消化方法,研究喷施不同浓度MnSO₄和ZnSO₄对小麦籽粒中Cd、锰（Mn）和锌（Zn）的含量及生物可给性的影响,计算人体对小麦Cd、Mn和Zn的摄入量,评价喷施Mn肥和Zn肥对降低人体Cd摄入、提高Mn和Zn吸收的作用。结果表明：喷施MnSO₄和ZnSO₄可显著降低小麦籽粒的Cd含量,最大降低率可达47.45%;喷施MnSO₄显著提高小麦Mn含量;喷施中高浓度的ZnSO₄显著提高小麦Zn含量。小麦Cd、Mn和Zn在胃阶段的生物可给性明显高于小肠阶段;高浓度ZnSO₄处理显著降低小麦Cd在胃阶段的生物可给性,提高Zn在胃阶段的生物可给性;高浓度MnSO₄处理使小肠阶段小麦Mn和Zn的生物可给性显著升高。食用Cd污染的小麦有Cd摄入量过高的健康风险,而ZnSO₄、高浓度MnSO₄以及中高浓度锰锌肥复配处理可显著降低人体食用小麦摄入Cd的量,最大降低率达42.86%;喷施MnSO₄显著提高小麦Mn的膳食摄入量;食用喷施MnSO₄和ZnSO₄处理的小麦可满足膳食Zn摄入的需要,其中喷施高浓度MnSO₄处理效果更好。研究表明,喷施高浓度MnSO₄可显著降低小麦Cd含量和人体Cd摄入量,显著提高小麦Mn含量以及Mn和Zn的生物可给性,从而显著提高人体Mn和Zn的摄入量。     

Atmospheric halocarbons, hydrocarbons, and sulfur hexafluoride: global distributions, sources, and sinks

The global distribution of fluorocarbon-12 and fluorocarbon-11 is used to establish a relatively fast interhemispheric exchange rate of 1 to 1.2 years. Atmospheric residence times of 65 to 70 years for fluorocarbon-12 and 40 to 45 years for fluorocarbon-l1 best fit the observational data. These residence times rule out the possibility of any significant missing sinks that may prevent these fluorocarbons from entering the stratosphere. Atmospheric measurements of methyl chloroform support an 8-to 10-year residence time and suggest global average hydroxyl radical (HO) concentrations of 3 x 10(5) to 4 x 10(5) molecules per cubic centimeter. These are a factor of 5 lower than predicted by models. Additionally, methyl chloroform global distribution supports Southern Hemispheric HO levels that are a factor of 1.5 or more larger than the Northern Hemispheric values. The long residence time and the rapid growth of methyl chloroform cause it to be a potentially significant depleter of stratospheric ozone. The oceanic sink for atmospheric carbon tetrachloride is about half as important as the stratospheric sink. A major source of methyl chloride (3 x 10(12)grams per year), sufficient to account for nearly all the atmospheric methyl chloride, has been identified in the ocean.