Electrochemical study of the fungicide acibenzolar-s-methyl and its voltammetric determination in environmental samples

The electrochemical behavior of new generation fungicide acibenzolar-s-methyl (S-methyl 1,2,3-benzothiadiazole-7-carbothioate, ASM) on the hanging mercury drop electrode (HMDE) was investigated using square wave adsorptive stripping voltammetry. This method of determination is based on the irreversible reduction of ASM at the HMDE. The well-defined ASM peak was observed at ?0.4 V (vs. Ag/AgCl) in BR buffer at pH 2.2. The reduction peak current was proportional to concentration of ASM from 1.0 × 10^?8 to 6.0 × 10^?8 mol L^?1 with detection and quantification limit 3.0 × 10^?9 and 1.0 × 10^?8 mol L^?1, respectively. The applicability of the developed method for analysis of spiked samples of tap water, river water, and soil is illustrated. The effect of adsorption on the mercury electrode was studied in detail using the AC impedance method. Possible interferences with other common pesticides and heavy metal ions were examined. Clarification of the electrode mechanism was made using cyclic voltammetry (CV) technique.     

施用不同磷肥对植烟土壤中磷的淋失和有效磷的影响

采用土柱淋溶模拟试验和室内培养试验,研究不同磷肥施入土壤后磷的淋失和有效磷的变化.结果表明,在施磷量为35 mg/kg条件下,整个淋洗期间,钙镁磷肥、磷酸二氢钙、磷酸一氧铵、磷酸二氢铵、磷酸二氢钾5种肥料磷的淋失率很低;各处理从上而下各层土壤的Olsen-P质量比略有增加.施磷量为60 mg/kg、110 mg/kg、170mg/kg、230 mg/kg时.潮砂田肥料磷的淋失率分别为0.26%、0.74%、2.12%和3.17%;灰泥田肥料磷的淋失率分别为0.79%、1.31%、1.60%和1.94%.钙镁磷肥施人各种土壤后,随着培养时间的延长,土壤有效磷质量比逐渐增加,80 d后达到峰值并趋于稳定;磷酸二氢钾、磷酸二氧铵、磷酸一氢铵和磷酸二氢钙施人上壤后,土壤有效磷质量比逐渐降低,至培育60 d后.变化趋于平缓.不同土壤类型对磷的吸附固定率从大到小为潮砂田、灰泥田.     

Concentrations of cadmium and lead heavy metals in Dardanelles seawater

Cadmium and lead were determined simultaneously in seawater by differential pulse stripping voltammetry (DPSV) preceded by adsoptive collection of complexes with 8-hydroxyquinoline (oxine) on to a hanging mercury drop electrode (HMDE). In preliminary experiments the optimal analytical condition for oxine concentration was found to be 2.10⁻⁵ M, at pH 7.7, the accumulation potential was −1.1 V, and the initial scannig potential was −0.8 V. The peak potentials were found −0.652 V for Cd and −0.463 V for Pb At the 60 s accumalation time. The limit of detection (LOD) and limit of quantitatification (LOQ) were found to be by voltammetry as 0.588 and 1.959 μg l⁻¹ (RSD, 5.50%) for Cd and 0.931 and 3.104 μg l⁻¹ (RSD, 4.10%) for Pb at 60 s stirred accumulation time respectively. In these conditions the most of the seawater samples are amenable for direct voltammetric determination of cadmium and lead using a HMDE. An adsorptive stripping mechanism of the electrode reaction was proposed. For the comparison, seawater samples were also analysed by ICP-atomic emission spectrometry method (ICP-AES). The applied voltammetric technique was validated and good recoveries were obtained.     

重金属铜在砂质壤土土柱中运移的数值模拟

通过室内土柱出流实验,分析了重金属离子铜在饱和砂质壤土中的运移行为,发现高浓度的入流液有利于铜离子的运移。同时借助于软件包CXTFIT,用确定性平衡模型和非平衡两区模型对铜离子的出流动态进行了拟合,并预测了土柱不同深度处铜离子浓度随时间的变化过程。结果表明,室内饱和均质条件下,应用确定性平衡模型拟合参数模拟精度要高于非平衡两区模型,可以不用考虑不动水体对铜离子运移的影响。     

LED3A土柱淋洗Pb与Zn污染砂土的效果

为探究不同淋洗方式下螯合型表面活性剂LED3A（N-十二酰基乙二胺三乙酸钠盐）对重金属污染土壤的淋洗效果,采用室内土柱淋洗法研究了LED3A在不同流速条件下对Pb、Zn单一污染砂土的淋洗效果,并通过优化的BCR法分析了淋洗前、后土柱中不同深度处Pb、Zn的形态变化特征.结果表明:LED3A对Pb、Zn单一污染砂土的淋洗规律基本类似,淋出液中ρ（Pb）、ρ（Zn）随淋洗液累积孔隙体积数目的增加呈现急剧增大、达到峰值后逐渐降低的趋势;Pb、Zn的淋洗曲线中均存在不同程度的拖尾现象,且对称性较差;淋出液中ρ（Pb）、ρ（Zn）峰值和Pb、Zn最大累积去除率均随流速的增大而减小.随着淋洗深度和流速的增加,各形态Pb、Zn的去除率均呈现减小的趋势,LED3A对酸可提取态Pb、Zn的去除效果最为显著,去除率均大于50%;对氧化物结合态、有机结合态和残渣态Pb、Zn的去除率大小顺序与淋洗深度和流速有关;对比淋洗前、后土柱中重金属的形态分布可知,最易释放和被生物利用的酸可提取态的占比明显减少,不易或不能被生物利用的氧化物结合态、有机结合态和残渣态的占比明显增加.研究显示,LED3A低流速淋洗不仅能够去除一定量的土壤重金属,同时可有效降低残留重金属对环境的潜在风险.      

Impact of mining activities on soils in a semi-arid environment: Sierra Almagrera district, SE Spain

Field and laboratory-column studies were undertaken in order to investigate soil contamination derived from past mining activity in the Sierra Almagrera (SA) district in southeast Spain. The tailings, soil and sediment samples that were collected showed high concentrations of Ag, As, Ba, Cu, Pb, Sb and Zn when analyzed. The mean concentrations of these elements in the tailings were 29.8, 285.4, 54000, 57.7, 2687.5, 179.0 and 2269.0 ppm, respectively. In the soil samples these decreased to 14.3, 96.9, 24700, 37.5, 1859.1, 168.5 and 815.7 ppm, respectively. Geochemical analyses demonstrated high levels of As, Pb and Zn which were above the intervention values set forth in the Andalusian Regulations for Contaminated Soils for As (>50 ppm), Pb (>500 ppm) and Zn (>2000 ppm). Column experiments and mineralogical studies suggest that the dissolution of sulfates and other secondary phases, accumulated in soils and waste-sites during the dry season, acts to control the mobility of metals. The elution curves obtained from column experiments showed a mobilization of Ba, Cu, Pb and Zn, while a low mobility was seen for Ag, As and Sb.     

水溶性有机物在土壤剖面中的分馏及对Cu迁移的作用

通过室内土柱试验研究了DOM在土壤剖面中的“分馏”作用,DOM在纵向运移过程中的穿透行为及对污染的红壤和潮土中重金属Cu溶出效果的影响.结果表明,绿肥和猪粪DOM经过土柱后极性都有所降低,在潮土上的降低幅度较大,分别为11.4%和10.72%;DOM能够明显地增加污染土壤中Cu的溶出,且这种作用效果与DOM及土壤的性质有关,绿肥DOM的作用效果比猪粪DOM的强,整个淋洗过程中潮土上Cu的平均溶出量是红壤上的4.37倍(绿肥DOM)和3.03倍(猪粪DOM);由于微生物对DOM的分解作用,降低了DOM对土壤中Cu的溶出效果.     

南京及邻近地区新近沉积土的动剪切模量和阻尼比的试验研究

通过对南京及其邻近地区漫滩相成因的粘土、粉质粘土、淤泥质粉质粘土、粉质粘土与粉砂互层土、粉土、粉细砂等 6类新近沉积土的自振柱试验 ,详细探讨了围压大小、剪应变水平、土的颗粒组成和结构性对这 6类新近沉积土的剪切模量G及阻尼比λ的影响。通过与Seed和Idriss建议的砂土G/Gmax～γ和λ～γ曲线变化范围的对比 ,结果表明 ,不能将粉质粘土与粉砂互层土简单地当作砂土或粉质粘土对待。通过试验和理论分析 ,给出了南京及其邻近地区 6类新近沉积土动剪切模量和阻尼比随剪应变变化的平均曲线的拟合曲线、包络线及其参数的推荐值 ,对实际工程具有一定的借鉴作用     

阴角邻面火灾作用下L型钢管混凝土柱耐火极限研究

运用有限元软件ABAQUS计算L形带肋钢管混凝土柱阴角相邻两面受火全过程下的耐火极限,分析了阴角邻面受火方式下构件内部温度场和应力场的变化规律,在此基础上分析荷载比、宽厚比、计算长度、加劲肋纵向间距、荷载偏心率、荷载角等参数对耐火极限的影响规律。数据表明:荷载比、计算长度对构件耐火极限影响较大,随着荷载比和计算长度的增大,耐火极限基本呈线性下降;加劲肋间距对构件耐火性能影响较小;由于L形柱的特殊形式,偏心荷载对耐火极限的影响规律较复杂,荷载作用点偏向低温区可以提高耐火极限。     

NaOH溶液对有机相苯酚反萃取的研究

本文系统进行了ＮａＯＨ溶液对负载苯酚的ＴＢＰ＋煤油溶剂的反萃取平衡实验。考虑苯酚的支萃取平衡和解离平衡,建立了反萃取的计算模式,并证明了模型的可行性。本文还讨论了ＮａＯＨ溶液浓度,油水相比,萃取平衡分配系数,溶剂中的负载苯酚浓度和ＮａＯＨ溶液中初始酚含量对反萃取率的影响。