非饱和土的理论与实践

发展非饱和土的理论和技术是现代土力学的一项基本任务。本文介绍作者十几年来在这一领域的研究成果,内容包括非饱和土的仪器研制、试验研究、工程特性、力学理论、分析方法和工程应用等方面。     

Improved extraction and clean-up of imidazolinone herbicides from soil solutions using different solid-phase sorbents

Extraction and quantification of herbicide residues from soil are important in understanding the behaviour of persistent herbicides. This research investigated extraction and clean-up methods for imidazolinone herbicides from soil and soil amended with organic material. A series of solvent mixes, pH conditions and sorbents was tested. Across three imidazolinone herbicides: imazapyr, imazethapyr and imazaquin, 0.5 M NaOH extraction gave greater than 90% recovery from soil samples; however, 0.5 M NaOH:MeOH (80:20) resulted in higher recovery for imazaquin, but not for the other two herbicides. Of the sorbents tested, the use of chromatographic mode sequencing using C₁₈ and SCX sorbents provided consistent high (>85%) recovery of all three herbicides from soil and separation of the herbicides from other soil components by high performance liquid chromatography (HPLC). These two methods will allow high recovery of these imidazolinone herbicides from soil and have the ability to detect these herbicides without interference from other soil components.     

湘潭市土壤重金属地球化学特征的统计分析

运用相关性分析、聚类分析、因子分析及直方图分析对湘潭市土壤重金属地球化学特征进行了研究。结果表明：（1）As、Cd、Cu、zn与pH值呈显著正相关;As与Cd、Cu、Ph、zn呈显著正相关;Cd与As、Cu、Pb呈显著正相关;Cu与As、Cd、Pb、Zn呈显著正相关;Pb与As、Cu、zn呈显著正相关;Zn与As、Cd、Cu、Pb呈显著正相关;Hg与其他重金属及pH值不具有显著相关关系。（2）本区重金属分为两类,即Cr、pH、As、Zn、Cu、Cd;Hg、Pb。（3）区内重金属存在3种主要元素组合即As—Cd—Cu—Pb—Zn—pH;Cr—Hg;Cd—pH;（4）区内重金属As、Cd、Cr、Cu、Hg、Zn服从正态分布。（5）通过前人对湘潭市土壤重金属进行生态地球化学评价可知,区内Cd、Hg属重污染,从统计分析结果来看,Cd随着本区pH值变化而变化,并与As、Cu、Pb相关性显著;而Hg与pH值及其它重金属之间没有必然联系。     

土壤铜污染的微生物及酶学指标研究

通过室内培养试验,研究了土壤铜污染对土壤微生物基础呼吸及土壤脲酶、脱氢酶、酸性磷酸酶的影响。结果表明,土壤微生物基础呼吸在低水平铜（≤100mg／kg）添加下呈现出先上升后下降的趋势,而随着土壤铜添加水平的进一步提高（〉100mg／kg）,微生物基础呼吸作用迅速增强;土壤脲酶则随着铜含量的增加呈现出不断下降趋势,土壤磷酸酶活性则在低水平下上升而随着添加水平的进一步提高迅速降低。可见,这两种酶对土壤铜毒害反应灵敏,可作为土壤铜污染评价的指标;而土壤脱氢酶则对铜含量的变化没有表现出明显的统计规律性,不适宜作为土壤铜污染评价的酶学指标。     

Dihydronaphthalenones from endophytic fungus Fusarium sp. BCC14842

Eleven new dihydronaphthalenones 1-11, together with five known compounds; 5-hydroxydihydrofusarubin C (12), javanicin, bostrycoidin, anhydrofusarubin, and 3-O-methylfusarubin, were isolated from the endophytic fungus Fusarium sp. BCC14842. Structures were elucidated by analyses of the NMR spectroscopic and mass spectrometry data. Javanicin, 3-O-methylfusarubin, compounds 3 and 7 exhibited antimycobacterial and cytotoxic activities. Javanicin also displayed antifungal activity with IC₅₀ of 6.16 μg/mL, while compounds 2, 4, 5, 8, and 12 showed only cytotoxic activity.     

石墨炉原子吸收分光光度法测定土壤中的镉

采用硝酸、高氯酸、氢氟酸消解土壤样品,用石墨炉原子吸收分光光度法测定土壤中镉的含量。线性回归方程为A=0.01733c-1.03×10~(-5),相关系数r=0.999 2,回收率为95％～105％,相对标准偏差RSD为7.5％～8.1％,方法检出限为0.019mg/kg。试验结果表明,该方法能满足环境土壤样品监测要求。     

Arsenic fractionation in agricultural soil using an automated three-step sequential extraction method coupled to hydride generation-atomic fluorescence spectrometry

A fully automated modified three-step BCR flow-through sequential extraction method was developed for the fractionation of the arsenic (As) content from agricultural soil based on a multi-syringe flow injection analysis (MSFIA) system coupled to hydride generation-atomic fluorescence spectrometry (HG-AFS). Critical parameters that affect the performance of the automated system were optimized by exploiting a multivariate approach using a Doehlert design. The validation of the flow-based modified-BCR method was carried out by comparison with the conventional BCR method. Thus, the total As content was determined in the following three fractions: fraction 1 (F1), the acid-soluble or interchangeable fraction; fraction 2 (F2), the reducible fraction; and fraction 3 (F3), the oxidizable fraction. The limits of detection (LOD) were 4.0, 3.4, and 23.6 μg L⁻¹ for F1, F2, and F3, respectively. A wide working concentration range was obtained for the analysis of each fraction, i.e., 0.013–0.800, 0.011–0.900 and 0.079–1.400 mg L⁻¹ for F1, F2, and F3, respectively. The precision of the automated MSFIA–HG-AFS system, expressed as the relative standard deviation (RSD), was evaluated for a 200 μg L⁻¹ As standard solution, and RSD values between 5 and 8% were achieved for the three BCR fractions. The new modified three-step BCR flow-based sequential extraction method was satisfactorily applied for arsenic fractionation in real agricultural soil samples from an arsenic-contaminated mining zone to evaluate its extractability. The frequency of analysis of the proposed method was eight times higher than that of the conventional BCR method (6 vs 48 h), and the kinetics of lixiviation were established for each fraction.     

Distribution and Assessment of Heavy Metals in Trifolium dubium (Little Hop Clover) and the Impact of Soil Quality

Trifolium dubium is an edible plant that is utilized in traditional medicine for its anti-inflammatory and wound-healing properties. In this study, T. dubium was assessed to determine the elemental uptake by the plant as a function of soil characteristics. Across 10 geographic locations in KwaZulu-Natal, South Africa, the concentration of elements in T. dubium were found to be (descending order) Ca?>?Mg?>?Fe?>?Zn?>?Mn?>?Se?>?Ni?>?Cr?>?Cu?>?Co?>?Pb?>?Cd?>?As. The site had an influence on elemental uptake by the plant; however, accumulation or exclusion of elements from soil was controlled to meet physiological requirements. Soil chemical characteristics showed T. dubium grew in slightly acidic soils (pH – 6.15 to 6.68). The findings of this study show T. dubium to contain adequate concentrations of essential elements with undetectable levels of toxic metals, making the herb safe for human consumption and for use in traditional medicine. The plant can also contribute to poor communities by ameliorating food insecurity.     

高效液相色谱法同时测定土壤中毒死蜱残留及其有毒代谢物3,5,6-TCP

通过对色谱分离条件优化、提取体系建立和固相色谱小柱筛选,建立了用弗罗里硅土固相萃取小柱净化高效液相色谱法同时测定土壤中毒死蜱农药残留及其有毒代谢物3,5,6-TCP.方法加标回收率在59％～87％之间,检测限为0.0005～0.03 μg/g,日内回收率标准偏差RSD≤4.3％,日间回收率标准偏差RSD≤4.9％,方法...     

Comparison of extraction techniques for quantitative analysis of pendimethalin from soil and rice grain

The paper exploits the development, optimization, and comparison of fast, efficient, quantitative analytical extraction techniques such as ultrasonic-assisted extraction (UAE) and matrix solid-phase dispersion (MSPD) for proficient extraction of pendimethalin from soil and rice samples. Residues of pendimethalin were quantified using high-performance liquid chromatography. Impact of several experimental parameters of UAE and MSPD techniques on extraction of pendimethalin from soil and rice samples was also evaluated. Under the optimized conditions, the mean percent recoveries obtained from both methods were in the range of 80.3–101.3 and 81.7–103.1, respectively, with relative standard deviation <10. Linearity was in the range of 0.003–5.0?µg?mL^?1 with limit of detection and limit of quantification as 0.001 and 0.003?µg?g^?1, respectively. MSPD method was found superior in terms of low solvent consumption, small sample size, and reduced matrix coextracts due to simultaneous extraction and cleanup steps. Both extraction methodologies were successfully applied in monitoring routine soil and rice samples, in which pendimethalin residues (0.003–0.007?µg?g^?1) were detected in few rice samples while residues in soil samples were below the quantification limit.