Reaction of thiometon and disulfoton with reduced sulfur species in simulated natural environment

The reactions of thiometon and its ethyl analogue, disulfoton, with reduced sulfur species [e.g., bisulfide (HS-), polysulfide (S(n)2-), thiophenolate (PhS-), and thiosulfate (S2O3(2-))] were examined in well-defined aqueous solutions under anoxic conditions. The role of reduced sulfur species was investigated in the abiotic degradation of thiometon and disulfoton. Experiments at 25 degrees C demonstrated that HS-, S(n)2-, PhS-, and S2O3(2-) promoted the degradation of thiometon to a great extent while only S(n)2- and PhS- showed a small accelerating effect in the degradation of disulfoton. Reactions were monitored at varying concentrations of reduced sulfur species to obtain the second-order rate constants. The reactivity of the reduced sulfur species decreased in the following order: S(n)2- > PhS- > HS- approximately S2O3(2-). Transformation products were confirmed by standards or characterized by gas chromatography mass spectrometry. The results illustrate that multiple pathways occur in the reactions with reduced sulfur species, among which the nucleophilic attack at the alpha-carbon of the alkoxy group was the predominant pathway. Activation parameters of the reaction of thiometon and disulfoton with HS- were also determined from the measured second-order rate constants over a temperature range. DeltaH( not equal) values indicated that the reactivity of thiometon toward HS- was much greater than for disulfoton. Nucleophilic attack at the alkoxy group was more important for thiometon than disulfoton. When the measured second-order rate constants at 25 degrees C are multiplied by [HS-] and Sigma[S(n)2-] reported in saltmarsh porewaters, predicted half-lives show that reduced sulfur species present at environmentally relevant concentrations may present an important sink for thiometon in coastal marine environments.     

Kinetics of nitric oxide consumption in tropical soils under oxic and anoxic conditions

The kinetics of nitric oxide consumption in four tropical soils were studied under oxic and anoxic conditions in a flow-through system in the laboratory. Under anoxic conditions the soils had a very high affinity for NO, resulting in K _M values of 0.02–0.27 ppmv NO (equivalent to 0.04–0.50 nM NO in the aqueous phase). These K _M values were lower than literature values for NO consumption by denitrifying bacteria. Under oxic conditions the kinetics of NO consumption in the tropical soils were completely different, exhibiting K _M values higher than 1.7 ppmv. These higher K _M values were similar to literature values for NO consumption by aerobic heterotrophic bacteria. Thus, the tropical soils studied seem to contain two different NO consumption activities which can be distinguished by their kinetics and which predominate under aerobic and anaerobic conditions, respectively. However, it was not possible to quantify the contribution of each process to total NO consumption under natural conditions. Under aerobic conditions NO turnover kinetics were positively correlated with soil respiration, N mineralisation and soil organic carbon, whereas under anaerobic conditions they were positively correlated with potential and actual denitrification rates and pH. Received: 26 September 1996     

Confirmation of phorate, terbufos, and their sulfoxides and sulfones in water by capillary gas chromatography/chemical ionization mass spectrometry

A gas chromatographic/mass spectrometric method capable of confirming phorate, terbufos, their sulfoxides, and sulfones in water is reported. Parents and their metabolites are separated in less than 5 min using a short capillary GC column and high carrier gas linear velocities. Positive ion chemical ionization mass spectrometry generates (M + H) ions indicative of the different molecular weights of the analytes and at least one confirmatory fragment ion for each analyte. Residues have been qualitatively confirmed at the 1 ppb level in fortified water samples from a variety of sources. Apparent residues in control water were less than 0.1 ppb.     

Recovery of Salmonella species from nonfat dry milk rehydrated under rapid and reduced pre-enrichment conditions: collaborative study

A collaborative study was conducted to compare the relative efficiency of the AOAC rapid rehydration method with the reduced rehydration soak method for the recovery of Salmonella species from nonfat dry milk (NFDM). In the AOAC method, a 25 g sample of NFDM is rapidly rehydrated at a 1:9 sample/water ratio and mixed by swirling. After 60 min, the flask contents are adjusted to a pH of 6.8, and 0.45 mL of 1% aqueous brilliant green dye solution is added. The flasks are then incubated at 35 degrees C. In the soak method, a 25 g sample of NFDM is gently added to the sterile brilliant green (BG) water at a 1:9 sample/BG water ratio and allowed to soak undisturbed for 60 min at room temperature before incubation. Twelve collaborators analyzed 3 shipments of samples with the following results for the AOAC and soak methods: shipment 1-31 and 46 positive samples, respectively, with a 48% increase in detection by the soak method; shipment 3-45 and 66 positive samples, respectively, with a 47% increase in detection by the soak method; shipment 2--no significant difference in recovery of Salmonella species by the 2 methods. It is recommended that the official final action method for the detection of Salmonella species, 46.054-46.067, be revised to use the soak method for the analysis of nonfat dry milk.     

Microbial biomass and activity under oxic and anoxic conditions as affected by nitrate additions

Soil microbial activity, biomass, and community structure were examined during the transition from oxic to anoxic conditions after the addition of glucose and with or without nitrate addition. In two sets of treatments, samples were incubated for up to 35 d in closed ampoules either aerobically until oxygen was depleted or anoxically throughout the experiment. Heat‐flow rate was monitored to indicate microbial activity. Microbial biomass and community structure were measured by adenylate and phospholipid fatty acid (PFLA) content, and adenylate energy charge (AEC) was used to monitor the physiological status of the microbial biomass. Microbial activity was highest under oxic conditions and abruptly decreased under anoxic conditions. Activity peaks were observed after about 9 d of anoxic conditions probably triggered by increased nutrient availability from dying microbial biomass, but these peaks were smaller after initial oxic incubation or nitrate addition. Microbial biomass was unchanged under oxic conditions but decreased under anoxic conditions. Most surviving microbes switched into dormancy. Changes in the microbial‐population structure were small and occurred only after 9 d of anoxic incubation. The results show that the nutrient status and the availability of electron acceptors such as nitrate were important factors ruling the direction and the extent of shifts in the microbial activity and community structures due to anoxic conditions.     

不同通风量下城市污泥堆肥过程中硫素的转化特征

  【目的】  研究通风量对城市污泥堆肥过程中硫素转化和挥发性硫化物释放的影响,为有效控制挥发性含硫恶臭物质,保留污泥堆肥产品中的硫素营养提供理论依据和方法。  【方法】  城市污泥和调理剂 (锯末) 以3∶1 (湿重) 的比例混合后,采用自动好氧堆肥控制装置进行15天的堆肥试验,通过改变鼓风机频率实现不同堆体的通风量调节。设置鼓风机工作频率10、13、16 Hz 3个处理,相应的通风量为2.5、3.0和3.5 L/min。在堆肥的第0、1、2、3、5、7、9、11、13、15天进行堆体内部多点混合采样,进行挥发性硫化物的浓度测定,研究城市污泥不同堆肥阶段硫素的转化特征。  【结果】  相较于低通风量 (10 Hz),高通风量 (16 Hz) 下H₂S的峰值浓度下降了约50%,但其累积释放量增加了45.4%;甲硫醚的累积释放量提高了398%,峰值浓度增加了490.8%;CS₂的累积释放量下降了57.8%,其峰值浓度下降了77%。堆肥产品中有效硫浓度在低、中、高通风量条件下相较于堆肥前分别上升了19.5%、19.1%、36.1%。  【结论】  城市污泥堆肥过程中,提高通风量可以降低H₂S的浓度峰值,但增加了H₂S的累积释放量,甲硫醚的峰值浓度和累积释放量均显著增加;提高通风量可以抑制城市污泥堆肥过程中CS₂的释放。在低、中、高3种通风量条件下,堆肥产品的有效硫浓度相较于堆肥前都明显升高。高通风处理虽然全量硫的损失最大,但更有利于提高堆肥产品中可直接被植物吸收的有效硫含量。     

Responsiveness of Kansas soil series to sulfur application under greenhouse conditions

Abstract

Soil series of extensive acreage were selected to evaluate their S‐supplying power under greenhouse conditions using alfalfa in one study and corn and grain sorghum as test crops in a second study. The soils were divided into two major groups by textural classification for statistical evaluations. The addition of sulfur significantly increased dry matter yields and sulfur content of the plant material on all soils through the course of these studies. Significant predictors of sulfur uptake include extractable SO₄‐S and organic matter. Organic matter was a significant predictor of the percent yield response above the check yields on soils receiving S applications using corn and grain sorghum as test crops. Based on this equation, yield response would be expected in this greenhouse study with an organic matter content of 2.6% or less.     

Uptake of sulfur by four cotton cultivars grown under field conditions

There has never been an intensive study of the sulfur (S) nutrition of cotton (Gossypium hirsutum L.) when grown under field conditions. Field studies were conducted on two non‐irrigated soils to evaluate the S‐uptake characteristics of four selected cotton cultivars that are representative of those produced in the Southern United States. Four cultivars with diverse genetic backgrounds, Deltapine 90, Coker 315, Paymaster 145, and Stoneville 825 were grown on a Norfolk fine sandy loam (fine loamy, siliceous, thermic, Typic Kandiudults) and a Decatur silt loam (clayey, kaolinitic, thermic, Rhodic Paleudults). Whole plants were collected at two‐week intervals over the growing season starting at 15 days after planting. The plants were partitioned into leaves, stems, burs, seed, and lint, and analyzed (except for lint) for S. Total S uptake when averaged over both soils and all four cultivars was 20.4 (±9.4) kg/ha [or 2.7 (±0.7) kg S per 100 kg lint produced]. Sulfur uptake on the Norfolk soil (15.6 (±8.5) kg/ha) was lower compared to the Decatur soil [25.1 (±7.9) kg/ha]. There were no cultivar differences in total S uptake on the Norfolk soil, but total S uptake on the Decatur soil was affected by the interaction between sampling date and cultivar. The concentration of S and S uptake by some plant parts were affected by the interaction between sampling date and cultivar, however, cultivar differences were not consistent among soils or over the growing season. Maximum daily accumulation of S occurred during the final two week sampling period at the end of the growing season (cumulative heat unit 1193–1444) during which an average of 29.5% of the total S was accumulated.     

Glutathione levels in phloem sap of rice plants under sulfur deficient conditions

Glutathione which is an abundant reduced sulfur compound in plants is considered to play important roles in the transmission of the sulfur nutrient status between organs within the plant body and in the long-distance transport of reduced sulfur. We determined the concentrations of glutathione, γ-glutamylcysteine (γ-EC), sulfate in the rice phloem sap collected by the insect laser technique. Phloem sap was collected from the plants cultured in sulfur-deficient and control solutions. The concentration of glutathione in the rice phloem sap was higher than that of sulfate in both control and sulfur-deficient plants. Under sulfur-deficient condition, the concentration of glutathione in the phloem sap did not decrease, whereas the sulfate concentration decreased significantly. The pattern of changes in γ-EC concentration was similar to that of glutathione. These data indicate the presence of mechanisms for the maintenance of a constant glutathione concentration in the phloem sap in rice plants under sulfur deficiency, whereas the sulfate concentration was found to be relatively unstable.     

Hydrolysis of terbufos using simulated environmental conditions: rates, mechanisms, and product analysis.

This study focuses on the hydrolysis of terbufos, an organophosphorus pesticide. Combining GC-MS and wet chemistry methods, di-tert-butyl disulfide and formaldehyde were identified and quantified as major degradation products. Diethyl dithiophosphate was also indirectly identified as a degradation product under alkaline conditions. Hydrolysis rate constants of terbufos under homogeneous conditions were comparable to those of phorate and show relative insensitivity to pH under slightly acidic to neutral pH conditions, as the observed rate constants varied only in the range of (4.5-5.0) x 10(-6) s(-1) between pH 5.7 and 9.4; neutral hydrolysis is thus the most dominant hydrolysis pathway of terbufos in ambient waters. The mechanisms for terbufos hydrolysis and the formation of the major products and their temporal profiles are discussed. To assess the environmental impact of degradation products of this widely used pesticide, Microtox was used to analyze the toxicity of terbufos and two of its degradation products: diethyl dithiophosphate and di-tert-butyl disulfide; the EC(50) of terbufos was found to be >17 microM, whereas the EC(50) of di-tert-butyl disulfide was 1.3 microM.     

高氮条件下硫氮互作对冬小麦幼苗生长及氮、硫吸收利用的影响

本试验在水培条件下,研究了不同氮、硫水平对小麦幼苗生长及氮、硫吸收利用的影响。结果表明,同一供氮水平下,在0.15 mmol/L～2.40 mmol/L供硫水平范围内,小麦幼苗根系活力随供硫水平的提高而显著下降。在4 mmol/L供氮水平下提高供硫水平,小麦幼苗植株地上部含硫量和含氮量均增加,叶片光合速率提高,对叶片和次生根的发育均有促进作用,增加了地上部和根系干物质积累量,但硫素利用效率和氮素利用效率降低。在8 mmol/L供氮水平下,随供硫水平的提高,小麦幼苗地上部含硫量增加,含氮量无显著变化;供硫水平过高则导致幼苗叶片光合同化能力降低,对幼苗发育、地上部和根部干物质及氮硫素积累不利,氮、硫利用效率降低。在0.15 mmol/L供硫水平下提高供氮水平有利于增加小麦幼苗地上部和根系含氮量,在2.40 mmol/L供硫水平下提高供氮水平对小麦幼苗地上部和根系含氮量无显著影响。说明在一定的氮、硫供应水平下,氮素和硫素之间存在互促效应;供应水平过高,则相互抑制,不利于小麦对氮、硫的吸收和利用。不同品种对氮、硫供应水平的反应不同,与鲁麦21和烟农19相比,在4 mmol/L供氮水平下,较高的供硫水平更有利于豫麦34和淄麦12各器官硫素和氮素的积累;在8 mmol/L供氮水平下,豫麦34和淄麦12对过高供硫水平的耐受能力较强。     

氧化还原条件下红壤磷吸附与解吸特性及需磷量探讨

研究了5个酸性红壤由氧化条件转为还原条件的P吸附和解吸特性,以及确定供试红壤作为水田或旱地相应的施P量。结果表明:5个土样P吸附量随P液浓度的增加而增加,土壤对P的吸附曲线均可用Langmuir方程拟合,氧化条件下P最大吸附量变化范围为794.22～956.75mg/kg,还原条件下P最大吸附量变化范围为867.31～1195.62mg/kg。P解吸量随P吸附量的增加而增加,P解吸率的结果表明,淹水不同程度地降低土壤P解吸量。以Langmuir方程计算土壤溶液中P浓度在0.2mg/kg时的土壤需P量作为施P量的依据,淹水后土壤标准需P量增加。     

Effect of organic residue amendment on mineralization of sulfur in flooded rice soils under laboratory conditions

Abstract

This study was undertaken to assess the mineralization of sulfur (S) in laboratory conditions of three rice soils (Joydebpur, Faridpur, and Thakurgaon), receiving the following treatments: 1) control, 2) rice straw (Oryza sativa L.), and 3) pea vine (Pisum sativum L.). The organic residue (25 mg g^‐1) was added and mixed with soil and glass beads (1:1, soil to bead ratio) and placed into a Pyrex leaching tube. The soils were flooded and incubated at 35°C, after which they were leached with deionized water at 1, 2,4, 8, and 12 weeks for analysis of SO₄ and other chemical properties in the leachates. Potentially mineralizable S (S_o) and C (C_o) pools and first‐order rate constants (K_s for S and K_c for C) in soils amended with rice straw and pea vine under flooded conditions were estimated using an exponential equation. The S_o and K_s varied considerably among the soils and types of added organic residues, and their values in rice straw and pea vine ranged from 8.70 to 29.55 and 0.124 to 0.732 mg S kg^‐1 wk^‐1, respectively. Except for the Thakurgaon soil, the S_o and K_s values in Joydebpur and Faridpur soils were higher in the unamended treatments. Higher S_o values in the unamended soils were probably due to less microbial activity to mineralize organic S from organic residues. The results indicate that the amount of SO₄ in flooded soils amended with organic residues are dependent on soil type, nature of organic residues, and time of incubation. The C_o and K_c values under flooded incubation were higher in residue amended soils than in unamended soils. Pea vine treated soils had higher C_o and K_c values than the soils treated with rice straw.     

Nutrient accumulation in four ornamental tree species under saline stress conditions

The present investigation was conducted at Punjab Agricultural University, Ludhiana, Punjab, India to screen four ornamental tree species ideal for salt-affected environment. Screening was done on the basis of nutrient accumulation in leaves and roots. The 1-year-old tree seedlings growing in 10″ pots were subjected to five levels of sodium chloride salinity stress (control, 30, 40, 50, and 60 mM). Experimental design utilized was factorial completely randomized block with three replicates in each treatment. In addition, the sodium (Na⁺)/ potassium (K⁺) ratio in leaves and roots of all ornamental tree species was determined. Based upon nutrients content and Na⁺/K⁺, the order of salinity tolerance observed in the study was Casuarina equisetifolia > Acacia auriculiformis > Callistemon lanceolatus > Putranjiva roxburghii.     

无菌砂培条件下三种农作物对甘氨酸的吸收

Seedlings of wheat (Triticum aestivum L.), Chinese cabbage (Brassica campestris L.) and mung bean (Phaseolus radiatus L.) were grown for 30 days in sterile sand media with 6 N treatments, I.e. NH4+-N, glycine-N, 3 different ratios of glycine-N:NH4+-N (NH4+-N was labeled with 15N) and a control receiving no N, to assess the importance of amino acids in excessive N nutrition along with inorganic N interactions. The contribution of nitrogen derived from glycine-N to total plant N was investigated. The total plant N of the three species treated with N was significantly greater (P < 0.05) than the control treatment. Also, seedlings from all the three species had significantly more total N as NH4+-N (P < 0.05) than at least two of the four treatments with glycine-N. However, for all species, differences in total N among treatments with a mixture of glycine-N and NH4+-N were mostly not significant. The contribution of N derived from glycine-N to plant total N content for all species increased with increasing glycine-N:NH4+-N ratio in the treatment solution. These results indicated that agricultural plants could effectively use organic nitrogen from organic nitrogen sources (e.g. glycine) and from organic and inorganic N mixtures (e.g. a glycine-N and NH4+-N mix). There were also genotypic differences in glycine-N and NH4+-N uptake by agricultural species.     

Movement of phorate under constant and variable surface water flux in initially dry and moist soils

The distribution of phorate was studied in three texturally different soils under constant and variable surface flux of water. Phorate distribution profiles and leaching curves showed that the insecticide was displaced more efficiently and its concentration peak formed at deeper depth with constant than with variable water flux in sandy loam soils irrespective of initial soil water content. However, phorate distribution profiles were found to be independent of the methods of water application in clay soil because of its extremely low permeability.     

Metabolic capabilities of forest soil microbial populations with reduced species diversity

Microbial populations of forest soil were modified by dilution and filtration of soil to reduce species diversity. Modified populations were allowed to increase their numbers fully after inoculation into soil sterilized by irradiation. Population modification was also attempted by starvation during prolonged incubations. Fully colonized soil was suspended and inoculated into sterile soil and respiration was followed. Metabolic capabilities of populations, altered by soil dilution and filtration, were considerably diminished compared to full soil populations. Starvation did not change the metabolic capabilities of the soil population.     

Investigations of aroma volatile biosynthesis under anoxic conditions and in different tissues of "Redchief Delicious" apple fruit (Malus domestica Borkh.)

Disks from different tissues were obtained from "Redchief Delicious" apple fruit (Malus domestica Borkh.) and analyzed for the ability to metabolize 1-pentanol as well as synthesize constitutive esters and alcohols under anoxic and aerobic conditions. The skin tissue displayed a greater capacity to synthesize pentanal, pentyl acetate, pentyl propionate, pentyl butyrate, and pentyl hexanoate than the hypanthial and carpellary tissues during incubation with 1-pentanol. With the exception of pentyl acetate and pentyl propionate biosynthesis, the hypanthial tissue synthesized these compounds at a higher rate than the carpellary tissue. Anoxia inhibited both constituent and 1-pentanol-derived ester biosynthesis. While anoxia inhibited ester biosynthesis, ethanol biosynthesis increased at a greater rate in tissue disks held under these conditions. Biosynthesis of 1-butanol, 2-methyl-1-butanol, and 1-hexanol was greater in tissue disks held in air during the first part of the measurement period and dropped off more rapidly than those transpiring in tissue disks held under anoxic conditions. The biosynthetic rates of all esters, both constituent and 1-pentanol-derived, increased as a result of air exposure. While hypoxic or anoxic conditions may promote ethanol synthesis, these conditions also appear to inhibit the formation of the ethanol-derived esters partially responsible for the off-flavor in apples attributed to ultralow O(2) controlled atmosphere storage.     

Changes in phosphorus fractions in the rhizosphere of some crop species under glasshouse conditions

The aim of the present study was to evaluate the effect of cultivation of some agronomic plant species on inorganic soil‐P fractions in different sampling zones. The experiment was conducted as a completely randomized design as factorial in three replicates. The factors were plant species (10 different species and control) and soil‐sampling zone (soil adhering to root mat, rhizosphere soil, and nonrhizospheric soil). The thin‐slicing technique was modified and used to sample rhizosphere soil. The percentages of P fractions in the planted and control soils were near 64% apatite (apatite‐P), 24% octa‐Ca‐phosphates (OCP‐P), 7% Fe‐phosphates (Fe‐P), 4% di‐Ca‐phosphates (DCP‐P), 1% Al‐phosphates (Al‐P), and 0% occluded‐P (O‐P). All of the studied plant species decreased significantly all of the inorganic P fractions in soil adhering to root mat and in rhizosphere soil compared to those in nonrhizosphere soil. However, these decreases were not equal for each fraction and the percentage of apatite‐P increased in rhizosphere soil of the plant species. The means of total P, soluble P, DCP‐P, OCP‐P, Al‐P, and Fe‐P were lower in soil adhering to root mat compared to those in rhizosphere soil. However, this difference was only significant for OCP‐P. In contrast, the mean of apatite‐P in soil adhering to root mat was significantly higher than that in rhizosphere soil. The changes of apatite‐P may be more governed by microbial activities (especially mycorrhizal symbiosis) which may be higher in rhizosphere soil compared to soil adhering to root mat.