Adsorption of lambda-cyhalothrin and cypermethrin on two typical Chinese soils as affected by copper

Background, aim, and scope  Pesticides and heavy metals pollution in soil environment has become a serious problem in many countries including China. Repeated applications of bordeaux mixture (a blend of copper sulfate and calcium hydroxide) and pyrethroid (Pys) insecticides have led to elevated copper (Cu) and Pys concentrations in vineyard surface soils. However, few studies focused on the interaction of Pys and heavy metals in the soil environment. Our previous studies had indicated the combined effect of cypermethrin (CPM) and Cu on soil catalase activity. Also, we had suggested that the addition of Cu could catalyze photo-degradation of CPM and lambda-cyhalothrin (λ-CHT) in aqueous solution and restrain their degradation in soil. To better understand the potential influence of Cu on the fate of Pys in the soil environment, the aim of the present work was to examine the effect of Cu on the adsorption of λ-CHT and CPM on two typical Chinese soils with different soil characteristics, which was one of the key processes controlling the fate of Pys, and to provide more information about the potential ecological risk of chemicals on the soil ecosystem. Fourier transform infrared and point charges analysis using the MOPAC program of the Gaussian system were also used to reveal the probable adsorption mechanism of λ-CHT and CPM on soils. Materials and methods  Two vineyard soils with different properties were chosen as experimental samples. They were sampled from 0 to 10 cm, dried, and sieved to 2 mm. Each soil was spiked with copper sulfate solution to obtain the following total soil Cu concentrations: 100, 200, 400, 800, and 1,600 mg·kg⁻¹. The treated soils were incubated for 2 weeks and then dried at 20°C. For each soil sample and at each soil Cu concentration, the adsorption of λ-CHT and CPM was measured using a batch equilibrium method. The concentration of λ-CHT was determined by HPLC, and the amount of λ-CHT and CPM adsorbed by the soil sample at equilibrium was determined by the difference between the initial and equilibrium concentrations in solution corrected by the blank adsorption measurement. Results  Without the addition of Cu, the adsorption of λ-CHT and CPM on Black soil is greater than that on Red soil, while the adsorption of λ-CHT on both soils is significantly stronger than that of CPM. As the soil Cu concentration increased from 19 (or 18; background) to 1,600 mg·kg⁻¹, the adsorption coefficient (K _d) of λ-CHT decreased from 12.2 to 5.9 L·kg⁻¹ for Red soil, and from 26.1 to 16.8 L·kg⁻¹ for Black soil, whereas the CPM adsorption coefficient in both soils decreased nearly by 100% (K _d decreased from 9.4 to 0.2 L·kg⁻¹ for Red soil and from 16.2 to 0.5 L·kg⁻¹ for Black soil). Discussion  Pys adsorption is a surface phenomenon which depends on the surface area and the organic matter content. Thus, the Black soil, having higher organic matter and greater surface area than that of the Red soil, show greater adsorption affinity to λ-CHT and CPM. In our study, the different adsorption affinity of the two Pys was obtained, which was probably attributed to differences with respect to their physical–chemical properties. Further comparison upon the two Pys was conducted. The point charges of halogen atoms in the λ-CHT and CPM were calculated, the differences of which probably lead to the fact that λ-CHT has a stronger binding capacity to soils than CPM. Also, FTIR spectra show that competitive adsorption occurs between CPM and Cu for the same adsorption sites, which is responsible for the obtained suppression of CPM adsorption affected by Cu. Conclusions  Lambda-cyhalothrin shows a significantly stronger adsorption than cypermethrin on both soils. This phenomenon may be due to several reasons: (1) λ-CHT has lower solubility and a higher octanol–water partition coefficient value than CPM; (2) λ-CHT consists of specific isomers, whereas CPM is mixtures of eight different isomers; (3) the chlorine and fluorine atoms in the λ-CHT have a negative point charge, whereas the chlorine atoms in the CPM have a positive point charge. As the soil Cu concentrations increased from 19 (or 18) mg·kg⁻¹ to 1,600 mg·kg⁻¹, the adsorption coefficient of λ-CHT and CPM decreased on both soils. This is mainly due to a competition between Cu and Pys for occupying the adsorption sites on soils. The information from this study have important implications for vineyard and orchard soils, which often contain elevated levels of Cu and Pys. These results are also useful in assessing the environmental fate and health effect of λ-CHT and CPM. Recommendations and perspectives  It is important for environmental scientists and engineers to get a better understanding of soil–metal–organic contaminant interactions. However, pesticide adsorption involves complex processes, and shortcomings in understanding them still restrict the ability to predict the fate and behavior of pesticide. Therefore, considerable research should be carried out to understand the mechanism of interaction between Pys and heavy metal on soils clearly.     

氯盐环境下钢筋混凝土构件锈胀开裂风险概率分析

为了研究时间和空间等不确定因素下钢筋混凝土构件的锈胀开裂损伤,针对氯离子腐蚀环境,将钢筋锈蚀划分为2阶段3个特征时刻,分析了锈蚀初始时间、锈胀开裂时间以及锈胀开裂至界限宽度时间的概率特征,建立了钢筋混凝土构件生命周期内锈蚀损伤的风险概率模型,讨论了锈蚀损伤影响参数的敏感性。结果表明:钢筋锈蚀对其影响因素的敏感程度依次为混凝土保护层、临界氯离子浓度、扩散系数和混凝土表面氯离子浓度;钢筋混凝土构件从发生锈胀开裂到裂缝达到界限宽度的时间很短,界限宽度的取值对锈蚀损伤的影响并不显著。     

两种生物炭对稻米中砷累积的影响研究

为探究土壤添加低剂量生物炭对稻米中砷累积的影响及作用机理,使用矿区砷污染土壤添加小麦和棉花秸秆生物炭进行盆栽和模拟试验.盆栽试验结果表明:添加质量分数为0.5％的低剂量小麦和棉花秸秆生物炭,可以降低稻米(糙米)砷浓度(约10％),作用有限.糙米中砷浓度的降低主要是由于其生物量增加所致.模拟试验结果表明:添加质量分数为1％?—?5％的高剂量生物炭可以显著促进土壤中砷释放,相比对照组,生物炭添加组土壤溶液中砷浓度增加了69％?—?243％,推测其可能是生物炭促进了微生物作用下铁氧化物的还原,进而导致砷释放.研究表明:土壤中施加低剂量小麦和棉花秸秆生物炭对减少水稻砷累积作用可能有限,而高剂量可能增加水稻砷污染健康风险.     

天津市夏秋季O3-PM2.5复合污染特征及气象成因分析

天津市PM_2.5-O₃复合污染主要发生在夏秋季,本研究筛选出2017年夏季一次和秋季两次典型PM_2.5-O₃复合污染过程,系统分析污染物变化特征,探究天气形势和主要气象因子的影响.结果表明,3次污染过程PM_2.5与O₃呈现不同程度的正相关性（日均值相关系数达到0.34~0.78）,O₃与PM_2.5中硫酸盐和有机碳日均浓度存在较为一致的变化趋势.与非复合污染日相比,复合污染日无机盐占PM_2.5组分的比重增加,增长率为1.9%~7.3%;而碳组分占比减小.复合污染过程发生时,天津地区处于低压槽前或高压后部,近地面弱的偏南风辐合造成较差的大气扩散条件,导致大气污染物的累积.研究结果发现,夏季和秋季PM_2.5-O₃复合污染过程需要适宜的气象条件,温度阈值分别为25~35℃和20~30℃,相对湿度分别为40%~70%和55%~100%.夏秋季复合污染过程关键无机组分及其形成机制有所差异.夏季,日间O₃等强氧化剂对SO₂的气相氧化过程和夜间高湿条件（大约60%）下液相化学反应可能是主导的化学机制,硫酸盐增长率为8.2%.秋季高湿环境（≥80%）不仅促进SO₂向硫酸盐转化,秋季第一次复合污染过程硫酸盐增长4.7%,也促进夜间N₂O₅水解反应等,秋季第二次复合污染过程硝酸盐增长6.0%,两种机制成为秋季复合日PM_2.5显著增长的关键机制.本研究揭示了驱动天津市PM_2.5-O₃复合污染过程发生的适宜气象条件、PM_2.5关键化学组分及其化学过程,为复合污染的成因及协同控制提供了参考.     

硒和生物炭联合施用降低稻米甲基汞累积的研究

汞矿区土壤汞污染是造成水稻及其他作物中汞累积的主要原因,尤其是稻米中甲基汞的累积已成为当地居民甲基汞暴露的重要途径之一。本文针对含汞废水排放所造成的稻田汞污染情形,分别进行了模拟实验和盆栽试验,探究无机硒、生物炭、硒和生物炭联合施用对降低稻米甲基汞累积的作用效果。结果表明,无论向土壤中添加无机硒,还是生物炭,抑或是两者的组合均能有效降低土壤中甲基汞含量,且随着硒添加量的增加,其相应处理组土壤甲基汞含量不断降低。盆栽试验表明稻米中甲基汞含量因硒或生物炭的添加降低62%～73%（硒处理）、88%（生物炭处理）和90%～91%（硒+生物炭处理）,表明了硒和生物炭共同施用的作用效果要好于单独施用硒的作用效果。这种效果可能与生物炭降低了土壤中甲基汞的生物可利用性有关。总之,本研究为原位修复控制稻田汞污染风险提供了可能途径。     

天水市过去116年气温变化趋势及突变分析

天水位于青藏高原东北部的副热带北部边缘,受大陆性季风气候的影响,生态环境脆弱,是研究全球变化区域响应的理想之地。基于天水市1901—2016年的月平均气温资料,运用一元线性回归、5年滑动平均和Mann-Kendall非参数检验等方法分析了过去116年来天水市气温在不同尺度上的变化特征及突变节点。结果表明：天水市1901—2016年气温总体呈上升趋势,气候倾向率为0.058℃?(10a) ^?1。各季节均表现出增温趋势,春季、夏季、秋季和冬季的线性倾向率分别为0.084℃?(10a) ^?1、0.019℃?(10a) ^?1、0.022℃?(10a) ^?1、0.102℃?(10a) ^?1。最冷月份1月及最热月份7月同样表现出增温趋势,线性倾向率依次为0.085℃?(10a) ^?1、0.038℃?(10a) ^?1。年平均气温在1923年和1993年发生了两次突变。春季和秋季突变年与年平均气温基本一致,夏季气温突变存在超前和滞后现象,冬季突变时间为1978年。最冷月份1月平均气温在1977年发生突变,最热月份7月平均气温突变年份集中在2000年之后。总体而言,天水市过去一百多年来,气温呈上升趋势与全球变暖大背景一致。     

延安市界限温度≥10℃的活动积温变化特征

利用延安气象站1951—2012年日平均气温资料,运用五日滑动平均法、一元线性回归等方法对界限温度≥10℃的初日、终日、持续天数以及活动积温进行了分析,并对初日、终日、持续时间以及活动积温与年平均气温的相关关系进行探讨。结果表明:界限温度≥10℃的初日呈现出提前趋势,气候倾向率为-1.845 d·(10a)~(-1);终日呈现出推迟趋势,变化倾向率为2.437 d·(10a)~(-1);持续时间延长,变化倾向率为4.189 d·(10a)~(-1);活动积温也增加,气候变化倾向率为106.57℃·(10a)~(-1)。界限温度≥10℃的初日、终日、持续时间以及活动积温与年平均气温存在显著相关,其中活动积温与年平均气温相关系数高达0.882,回归分析显示年平均气温每升高1℃时,界限温度≥10℃的活动积温增加217℃。     

A strategy for enhancing anaerobic digestion of waste activated sludge: Driving anodic oxidation by adding nitrate into microbial electrolysis cell

Cathodic reduction of CO₂ and anodic oxidation of organic matters are crucial to methane-producing microbial electrolysis cell (MEC) applied in anaerobic digestion of waste activated sludge. However, cathodic CO₂ reduction is usually restrained by slow metabolism rates of H₂-utilizing methanogens and low electron-capturing capacity of CO₂, which consequently slows down the anodic oxidation that participates to sludge disintegration. Herein, a strategy with adding nitrate as electron acceptor to foster electronic transfer between the anode and cathode was proposed to improve anodic oxidation. Results showed that the average efficiency of anodic oxidation in the nitrate-added MEC increased by 55.9%. Accordingly, volatile suspended solid removal efficiency in the nitrate-added MEC was 21.9% higher than that of control MEC. Although the initial cumulative methane production in the nitrate-added MEC was lower than that of control MEC, the cumulative methane production in 24?days was 8.9% higher. Fourier transform infrared spectroscopy analysis indicated that anodic oxidation of MEC with nitrate accelerated the disintegration of sludge flocs and cell walls. Calculation on current signal further revealed that anodic oxidation driven by cathodic nitrate reduction was the main mechanism responsible for the improved sludge digestion.     

头孢噻肟钠与重金属对AmpC β-内酰胺酶类抗性基因转移的影响

为探究抗生素和重金属对抗性转移及接合子抗性基因丰度的影响,借助绿色荧光蛋白标记质粒,采用滤膜接合配对方法研究了胁迫条件对细菌接合频率的影响,定量检测了转移后的AmpC β-内酰胺酶类抗性基因丰度的变化.结果表明,头孢噻肟钠及重金属共胁迫促进了AmpC β-内酰胺酶类抗性基因从复杂群落到Escherichia coli BL21的转移.3μg·L~(-1)头孢噻肟钠胁迫下,细菌接合频率为空白组的2.06倍,其中,接合子耐药基因CIT、FOX和EBC的相对丰度分别升高了7.47、4.30和1.60倍.同时,以3μg·L~(-1)头孢噻肟钠胁迫组为对照,研究了重金属汞、铜和锌共胁迫对抗性转移的影响,考虑到头孢噻肟钠的水解特性和接合子克隆性扩增,接合时间定为3 h.结果发现,汞、铜、锌与头孢噻肟钠共胁迫组的细菌接合频率分别比对照组增长了2.57、1.60和1.74倍.汞共胁迫对接合子中7种AmpC β-内酰胺酶类抗性基因丰度无显著影响;铜共胁迫效应因抗生素抗性基因(ARGs)种类不同而不同,其中,对抗性基因EBC相对丰度的影响最大;锌共胁迫效应受锌离子浓度和ARGs种类影响,100 mg·L~(-1)锌共胁迫使得EBC和CIT丰度比对照组分别增加3.56和2.76倍.可见,抗生素与重金属共胁迫条件可促进环境中AmpC β-内酰胺酶类抗性基因的转移,值得关注.     

无机复合调理剂对污泥脱水性能的影响

针对污泥的固化填埋或建材化利用等后续处置方式,采用FeCl3与生石灰、粉煤灰两种骨架构建体为主要成分的无机复合调理剂对市政污泥进行调理.通过污泥真空抽滤、离心脱水及比阻测定实验,分别确定FeCl3、生石灰、粉煤灰的优化投加量为2.0 g.L-1、20.0 g.L-1、30.0 g.L-1.在优化投加量下,污泥比阻可降到...