Determination of maize and grain herbicides and their transformation products in soil by use of soil column extraction then liquid chromatography with tandem mass spectrometry

Summary A multiresidue method has been developed for identification and quantitation of the herbicides most commonly used in cultivation of maize and grain, and of their transformation products, in soil samples. The analytes were isolated by soil column extraction (SCE) and the extracts were purified by use of a Carbograph-1 cartridge. Analysis was performed by liquid chromatography coupled with tandem mass spectrometric detection (LC-TISP-MS-MS) in negative-ion mode. To optimize the extraction conditions affecting the performance of SCE, e.g. the extracting solvent used, temperature, extracting volume, and solvent flow rate, were studied. To evaluate the matrix effect in SCE, recovery experiments were performed on soil samples, with different physical and chemical characteristics, fortified with the 100 ng g⁻¹ of the target compounds. Recovery data were satisfactory and the method detection limits were between 3 and 100 ng g⁻¹, depending on the compound.     

土壤中挥发性有机化合物的GC-MS测定

利用气相色谱－质谱联用技术，对某废弃化工厂原厂区及附近农田的土壤中可能存在的60种挥发性有机化合物进行了定性和定量分析；采用质量保证和质量控制步骤对分析结果进行监测，结果令人满意。     

土壤有机质对菲的吸附-解吸平衡的影响

以自然土壤和过氧化氢分级土壤为实验模拟样品,测定了菲在这些样品上的吸附一解吸等温线,用线性和Freundlich模型拟合了这些等温线．^13C NMR谱表明,随着土壤有机质腐殖化程度的加深,有机质将含有较多的长链烷烃化合物,含氧、氮化合物有所减少,芳香环的数量变化不大．吸附实验结果表明,土壤有机质含量与菲的吸附容量存在一定的线性相关关系．有机质腐殖质化程度较深的样品比原土壤具有更大的吸附容量,其吸附等温线表现出更为明显的非线性,而且具有更明显的解吸滞后现象．说明土壤中一些结构紧密和含极性官能团较少的有机质是引起菲的非线性吸附过程和解吸滞后现象的主要原因。     

冲积平原区土壤中重金属元素的存在形态分析

采用0.1mol／L氢氧化钠浸提腐殖酸的方法,将土壤中的腐殖酸及与腐殖酸结合的重金属元素分离出来;分别用分光光度法、原子荧光光谱法、等离子质谱法测定样品中腐殖酸及重金属元素的含量;初步测定结果显示：与腐殖酸结合的重金属元素是冲积平原区表层土壤中重金属元素的1种重要存在形态,而且可能是土壤中重金属污染元素主要的存在形式。     

Enantioselective separation of the carfentrazone‐ethyl enantiomers in soil,water and wheat by HPLC

A simple enantioselective HPLC method was developed for measuring carfentrazone‐ethyl enantiomers. The separation and determination was accomplished on an amylose tris[(S)‐α‐methylbenzylcarbamate] (Chiralpak AS) column using n‐hexane/ethanol (98:2, v/v) as mobile phase at a flow rate of 1.0 mL/min with UV detection at 248 nm. The effects of mobile‐phase composition and column temperature on the enantioseparation were discussed. The accuracy, precision, linearity, LODs, and LOQ of the method were also investigated. LOD was 0.001 mg/kg in water, 0.015 mg/kg in soil and wheat, with an LOQ of 0.0025 mg/kg in water and 0.05 mg/kg in soil and wheat for each enantiomer of carfentrazone‐ethyl. SPE was used for the enrichment and cleanup of soil, water, and wheat samples. Recoveries for two enantiomers were 88.4–106.7% with RSD_r of 4.2–9.8% at 0.1, 0.5, and 1 mg/kg levels from soil, 85.8–99.5% with the RSD_r of 4.4?9.6% at 0.005, 0.025, and 0.05 mg/kg levels from water, and from wheat the recoveries were 86.3?91.3% with RSD_r below 5.0% at 0.2, 0.5, and 1 mg/kg levels. This method could be used to identify and quantify the carfentrazone‐ethyl enantiomers in food and environment.     

Effects of land use patterns on soil aggregate stability in Sichuan Basin, China

Soil aggregate stability as a key indicator of soil structure, is a product of interactions between soil environment, management practices, and land use patterns. The objective of this study was to analyze the impact of various land use patterns on soil aggregate stability in Sichuan Basin of southwestern China. The dry- and water-stable aggregate size distributions were determined by manual dry sieving procedure and Yoder's wet sieving procedure, respectively, while microaggregates and its mechanical and chemical stabilities by Kachisky's method, oscillator method, and citrate-dithionate (C-D) reagent method, separately. The results indicated that fractal dimension and surface fractal dimension were useful indicators to reflect soil aggregate distribution. Land use patterns have an obvious influence on soil aggregate stability. In the study area, water stability, mechanical stability, and chemical stability followed the sequence, Barren landforestlandorchardcropland, and the original stability and collapse velocity were sensitive to soil properties and soil structure. The difference of aggregate stability under different land use patterns is mainly due to the intensity of human disturbance and cultivation. Improper land use patterns will lead to breakdown of unstable aggregates, producing finer and more-easily transportable particles and microaggregates. In the future, inappropriate cultivation and land use patterns should be changed to protect soil structure, to improve soil aggregate stability and soil fertility in Sichuan Basin.     

基于土拱效应的抗滑桩与护壁桩的桩间距分析

抗滑桩与护壁桩分别在滑坡治理和基坑支护中发挥着巨大的作用 ,其实施正是利用了土中的成拱效应 ,然而传统桩的设计虽考虑土拱效应的存在 ,但桩间距确定理论与方法并未建立起来。本文首先基于土体的极限平衡条件对滑坡推力作用下的土体中的成拱作用进行研究 ,得出了抗滑桩的最大桩间距公式 ,并以某一具体工程为例 ,对该最大桩间距的物理意义和可用性进行了讨论。在此基础上 ,给出了在考虑土拱效应的情况下合理桩间距的确定方法 ,并以此为据 ,对边坡加固设计提出一些建议.     

降雨条件下固体废弃物边坡变形及破坏模式试验研究

利用室内模型试验及稳定性分析的手段 ,研究在降雨作用下高速公路通过的城市固体废弃物路堑边坡变形特征及破坏模式 ,分析了边坡各部位在降雨作用下变形量的变化规律 ,得出变形过程的 5个阶段 ,给出了固体废弃物边坡主要以溜坍或滑塌、坡面冲刷及滑坡 3种破坏形式 ,并提出了治理建议     

基于因素敏感性分析的人工排土场高边坡稳定性研究

在考虑人工排土场松散高边坡基本特征、变形破坏方式等的基础上,采用因素敏感性分析法,计算讨论了影响排土场高边坡稳定的主要因素--坡体几何形态特征、日常爆破震动、水等因素的变化对其稳定性的影响程度,确定了坡体几何形态特征因素为影响其稳定性的关键因素以及在确保排土场高边坡稳定条件下的单台阶合理坡角、坡高、预留宽度等人工堆积参数及最大堆积高度。     

时程稳定性系数确定的边坡逐孔起爆孔间微差降振时间

为了获得边坡逐孔爆破最佳降振微差时间,以某个实际边坡逐孔微差爆破施工现场为原型,先利用ANSYS建立二维静态模型,借助有限元折减法确定自然状态下的潜在滑动面和静态安全系数;基于已确定的二维潜在滑动面重新建立同尺寸同性质的三维逐孔微差爆破动态模型,利用LS-DYAN进行动力分析,整个过程分别设置同排3个炮孔0、17、25、42和65 ms等5种不同孔间微差起爆方式;同时,对该施工现场进行排、孔间(25 ms,17 ms)、(25 ms,25 ms)、(25 ms,42 ms)、(25 ms,65 ms)等4种微差时间控制的等比例相似小炮测振实验。提取模拟结果中3个炮孔同时起爆时滑面单元的应力数值代入极限平衡法计算公式,绘制了冲击载荷作用下边坡稳定性系数曲线,通过对曲线的理论分析发现,最佳降振微差时间约为48 ms;而三维数值模拟和测振实验结果均显示,孔间微差时间取42 ms时降振效果较佳。这说明,边坡稳定性系数曲线给出的微差时间与模拟和实验结果较为接近,可为今后边坡逐孔微差爆破降振研究提供参考。