Enhanced degradation of carbofuran in pacific northwest soils

Abstract

Persistence of ¹⁴C‐carbonyl carbofuran was measured in Pacific Northwest soils that had received 1–14 applications of the insecticide for root weevil control on perennial crops. Insecticide decay curves were obtained in nonautoclaved soil and several autoclaved soil samples from previously‐treated fields and in nonautoclaved soils from paired control sites not previously treated with carbofuran. The insecticide usually degraded faster in soil from previously‐treated fields than in soil from corresponding control fields. Among 26 previously‐treated fields, the pseudo half‐life (time for 50% loss) of carbofuran was < one wk in 11 soils, 1–3 wks in 8 soils and > 4 wks in the remaining soils. Among the nontreated control fields the pseudo half‐life was > than 2 wks in all cases and > than 15 wks in 5 of the soils. The carbofuran decay curve always possessed an initial lag phase where soil mixing enhanced insecticide decline. Carbofuran degraded very slowly in autoclaved soil samples. The half‐life of carbofuran exceeded 16 wk in all autoclaved soils tested and in most instances 85–90% of the original dosage remained when the tests were terminated 112 days after treatment. These results provided evidence that many of the soils which received applications of carbofuran over the past several years have developed a capacity to degrade carbofuran very rapidly.     

Supercritical Fluid Extraction for Forensic Analysis of Hydrocarbons in Soil

Supercritical fluid extraction (SFE) was investigated to evaluate its potential for obtaining high quality chromatographic fingerprints from soils encountered in environmental investigations. While the volatile and semivolatile fractions of light nonaqueous phase liquid (LNAPL) samples can be “fingerprinted” in a single chromatographic run, it is commonly not possible to obtain samples of LNAPL in the locations of interest. For this and other reasons, it was desirable to develop this method (SFE) of soil extraction, which allows chromatographic fingerprinting of the same quality routinely obtained with LNAPL so that environmental forensic investigations could be extended to areas beyond those containing LNAPL in monitoring wells. In this study, SFE was compared to conventional dichloromethane extraction. Both artificially spiked soil and soil from petroleum release sites were tested. Since water can be a problem when using the SFE method, particular attention was given to handling soils with high moisture contents. The SFE extracts showed excellent retention of low molecular components, including pentanes. Gas chromatography of SFE extracts yielded molecular distributions that showed no significant bias toward either low or high molecular weight components. These results show that SFE can be used to obtain an unbiased, single-run chromatographic “fingerprint” of both volatile and semivolatile hydrocarbons in contaminated soil samples.     

固定化微生物修复石油污染土壤影响因素研究

针对石油污染土壤修复,利用实验室已筛选的高效石油降解单菌SM-3,以天然有机材料为载体,吸附法制备固定化微生物。将游离与固定化微生物应用于室内花盆模拟修复石油污染土壤,对C/N/P、微生物投加量、石油含量、氧化剂和表面活性剂设计5因素4水平正交实验,探讨不同修复时期各影响因素的重要性顺序,最佳条件下各菌株的修复效果。结果表明,不同微生物在不同降解时期,各影响因素的重要性会发生变化;经过21 d的修复,固定化单菌SM-3石油降解率为22.77%,修复过程中,接种量是最重要的影响因素,营养元素N、P投加影响较大,表面活性剂和氧化剂影响次之。     

Effects of sewage sludge amendments on pesticide sorption and leaching through undisturbed Mediterranean soils

The Gharb region in Morocco is an important agricultural zone where soils receive pesticide treatments and organic amendments to increase yields. The groundwater aquifer in the Gharb region is relatively shallow and thus vulnerable. The objective of this work was to study the influence of organic amendments on diuron, cyhalofop-butyl and procymidone leaching through undisturbed soil columns. Two soils were sampled from the Gharb region, a Dehs (sandy soil) and a R’mel (loamy clay soil). Following elution (124.5 mm), the amount of pesticide residues in the leachates of the sandy soil (0.06–0.21 %) was lower than in those of the loamy clay soil (0.20–0.36 %), which was probably due to preferential flow through the loamy clay soil. The amount of procymidone leached through the amended soil columns was greater than the control for the sandy soil only. The organic amendments did not significantly influence diuron and cyhalofop-butyl leaching in either of the soils. The application of organic amendments affected the amounts of dissolved organic matter (DOM) eluted and thus pesticide leaching as a function of soil-type. Nevertheless, in some case, the formation of pesticide-DOM complexes appeared to promote pesticide leaching, thus increasing groundwater contamination risks.     

Cr(Ⅵ)污染土壤的热解还原无害化处理

提出了用热解还原法对含铬土壤进行无害化处理的新技术,研究了热解温度、热解时间及土壤有机质对铬无害化处理的影响,分析了热解前后土壤中铬的元素形态的变化.同时还探讨了热解还原过程中Cr(Ⅵ)的无害化机制.结果表明,土壤中的有机质在热解还原过程中产生的挥发分对Cr(Ⅵ)的无害化起核心作用;在200～600℃范围内,Cr(Ⅵ)的还原量随着热解温度升高而增大,500.0℃最适合于经济有效地实现Cr(Ⅵ)的热解还原处理;Cr(Ⅵ)的热解还原过程较快.铬的形态分析结果表明,热解后可交换态和碳酸盐结合态铬量大大降低,大部分铬转化成了活性低的残渣态,极大地降低了铬的危害.     

喀纳斯自然保护区生态系统服务价值变化研究

生态系统可持续发展是随着全球范围内可持续发展研究的深入和人们对环境破坏和资源利用认识的不断加深而逐渐形成的.人类社会的可持续发展从根本上取决于生态系统及其服务的可持续性,本文应用喀纳斯自然保护区1980、2005年两期Landsat TM影像解译数据,参照谢高地等制定的中国生态系统单位面积生态服务当量因子和新疆布尔津县单位面积农田生态系统提供的食物生产服务的经济价值,确定喀纳斯自然保护区生态系统单位面积生态服务价值系数,对保护区生态系统服务价值及其变化进行了估算和比较.结果表明,林地和草地是喀纳斯自然保护区主要的土地利用类型,25年间土地利用总体上发生了明显变化,林地面积在减少,革地、水域、建设用地面积略有增加；保护区生态系统服务价值由1980年的37.289亿元减少至2005年的36.351亿元,有林地和离覆盖度草地的减少是服务价值降低的主要原因；主要由林地、草地和水域提供的维持生物多样性、水文调节、气候调节、保持土壤等单项功能服务价值均呈现不同程度地减少,说明保护区生态系统结构和功能已受到影响,保护区生态环境质量不断趋向退化.     

土壤-植物系统中磷和砷相互作用关系的研究进展

砷元素导致的环境污染问题日益突出，施磷已成为植物修复砷污染土壤过程中必要强化措施之一。土壤-植物系统中磷和砷的相互作用关系是非常复杂的，研究表明：磷和砷在土壤中往往是共生的，但又存在竞争吸附关系；磷和砷在不同植物中的相互作用关系主要有拮抗效应和协同效应；有必要通过分子生物学手段对磷和砷表达基理进行深入研究，获得对砷具有超积累能力的植株。     

Volatilization of 1,2‐dibromo‐3‐chloropropane (DBCP) from soils

Abstract

The volatilization of DBCP from soils, as affected by the soil characteristics and application techniques, was studied in a laboratory experiment. The volatilization rate of DBCP applied in water was higher from sandy and silty loam soils than from clay soil. Water added after DBCP application acted as a soil cover, decreasing the volatilization rate. The results obtained with DBCP application in hexane to air‐dry soils, indicate that adsorption could be an important factor in reducing the volatilization losses.

Diffusion coefficients were calculated from the volatilization parameters, by using a simplified relationship between volatilization losses and diffusion through soil.     

Bacterial diversity in paclobutrazol applied agricultural soils

The aim of this study was to investigate the bacterial communities on paclobutrazol [(2RS, 3RS)-1-(4-Chlorophenyl)-4, 4-dimethyl-2-(1H-1,2,4-triazol-1-yl) pentan-3-ol]–applied agricultural soils by denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR) amplified 16S rDNA gene fragments. Three different agricultural soil samples were collected from paclobutrazol applied mango and waxapple orchards, peanut fields and untreated rice fields as a control for DGGE analysis. The DGGE pattern of PCR- generated 16S rDNA gene fragments indicated that the bacterial populations from four paclobutrazol–applied soils of peanut fields were closely related to each other and two paclobutrazol–applied soils of mango and waxapple orchards harbored closely related bacterial communities. But, paclobutrazol–free agricultural soils comprised relatively a different bacterial group. However, the bacterial populations of mango and waxapple orchard are completely different from the bacterial communities of peanut field. Further purification and sequence analysis of 40 DGGE bands followed by phylogenetic tree assay showed similar results that soil bacteria from paclobutrazol applied mango and waxapple orchard are phylogenetically related. Based on the phylogenetic analysis, the clone M-4 was clad 100 % (bootstrap value) with Mycobacterium sp. The Mycobacterium sp. has been proved to degrade the phenolic compounds such as phenol, 4-chlorphenol, 2,4-dichlorophenol and paclobutrazol molecule containing chlorobenzene ring.     

Assessment of Reclaimed Municipal Wastewater Application on Rice Cultivation

Field research was carried out to assess the effects of the application of reclaimed municipal wastewater on rice cultivation in Thessaloniki, Greece during a 2-year period (1999–2000). Effects on production cost, soil composition, and health risk were examined. A randomized complete block design was used for the paddy field with three treatments and four replicates. The treatments were (1) river irrigation water with N–P fertilization, (2) reclaimed wastewater irrigation with surface N fertilization, and (3) reclaimed wastewater irrigation without fertilization. The results showed that the total production cost decreased 8.8% and 11.9% by applying the second and third treatments, respectively, compared to the first treatment, without significant differences in the agronomic and rice quality traits. Soil composition showed discrepancies between the 2 years and the three treatments, whereas the pathogens of the reclaimed wastewater and rice tissues posed a low human risk when taking the needed precautions.