Electro-migration of heavy metals in an aged electroplating contaminated soil affected by the coexisting hexavalent chromium

Cr(VI) was often reported to oxidize soil organic matter at acidic environments due to its high ORP, probably thus changing cationic metal species bound to soil organic matter, and influencing their electro-migration patterns. However, such an effect on the electro-migration was not confirmed in most previous studies. Therefore, this study applied a fixed voltage direct current field on an aged electroplating contaminated clayed soil, with a special interest in the direct or indirect influence of Cr(VI) on the electro-migration of other coexisting metals. After 353 h electrokinetic process, 81% of Zn, 53% of Ni and 22% of Cu in the original soil were electro-migrated into the electrolyte, and most of the remaining concentrated near the cathode. The Cr(VI) oxidized some soil organic matter along its migration pathway, with a pronounced reaction occurred near the anode at low pHs. The resulting Cr(III) reversed its original movement, and migrated towards the cathode, leading to the occurrence of a second Cr concentration peak in the soil. Metal species analyses showed that the amount of metals bound to soil organic matter significantly decreased, while a substantial increase in the Cr species bound to Fe/Mn (hydro-)oxides was observed, suggesting an enhancement of cationic metal electro-migration by the reduction of Cr(VI) into Cr(III). However, the Cr(VI) may form some stable lead chromate precipitates, and in turn demobilize Pb in the soil, as the results showed a low Pb removal and an increase in its acid-extractable and residual fractions after electrokinetic remediation.     

Simultaneous extraction of Cr(VI) and Cu(II) from humic acid with new synthesized EDTA derivatives

Soil washing is one of the few permanent treatment alternatives for removing metal contaminants. Ethylenediaminetetraacetic acid and its salts (EDTA) is very effective at removing cationic metals and has been utilized globally. However it is ineffective for anionic metal contaminants or metals bound to soil organic matter. The simultaneous removal of cationic and anionic metal contaminants by soil washing is difficult due to differences in their properties. The present study evaluated the potential of a washing process using two synthesized EDTA-derivatives, C₆HEDTA (2,2′-((2-((carboxymethyl)(2-(hexanoyloxy)ethyl)amino)ethyl)azanediyl)diacetic acid) and C₁₂HEDTA (2,2′-((2-((carboxymethyl) (2-(dodecanoyloxy)ethyl)amino)ethyl)azanediyl)diacetic acid), which consist of a hydrophilic polycarboxylic moiety and a hydrophobic moiety with a monoalkyl ester group. A series of equilibrium batch experiments at room temperature were conducted to investigate the efficacy of C₆HEDTA and C₁₂HEDTA as extractants for both oxyanion Cr(VI) and cationic Cu(II). Results showed that either C₆HEDTA or C₁₂HEDTA can extract both Cr(VI) and Cu(II) from humic acid simultaneously. However, C₆HEDTA was less effective for Cr(VI) probably because it has no surface activities to increase solubility of humic acid, like C₁₂HEDTA. Extraction of Cr(VI) was mainly attributed to the decreased surface tension and enhanced solubility of organic matter. Extraction of Cu(II) was attributed to both the Cu(II) chelation and enhanced solubility of humic acid. It was demonstrated that the hydrophilic polycarboxylic moiety of C₁₂HEDTA chelates cations while the monoalkyl ester group produces surface active properties that enhance the solubility of humic acid.     

Effect of UV-A radiation as an environmental stress on the development,longevity, and reproduction of the oriental armyworm, <Emphasis Type="Italic">Mythimna separata</Emphasis> (Lepidoptera: Noctuidae)

The ultraviolet light (UV-A) range of 320–400 nm is widely used as light trap for insect pests. Present investigation was aimed to determine the effect of UV light-A radiation on development, adult longevity, reproduction, and development of F₁ generation of Mythimna separata. Our results revealed that the mortality of the second instar larvae was higher than the third and fourth instar larvae after UV-A radiation. As the time of UV-A irradiation for pupae prolonged, the rate of adult emergence reduced. Along with the extension of radiation time decreased the longevity of adult females and males. However, the radiation exposure of 1 and 4 h/day increased fecundity of female adults, and a significant difference was observed in a 1 h/day group. The oviposition rates of female adults in all the treatments were significantly higher than the control. In addition, UV-A radiation treatments resulted in declined cumulative survival of F₁ immature stages (eggs, larvae, and pupae). After exposure time of 4 and 7 h/day, the developmental periods of F₁ larvae increased significantly, but no significant effects on F₁ pupal period were recorded.     

The reductive degradation of 1,1,1-trichloroethane by Fe(0) in a soil slurry system

Most studies on the treatment of chlorinated contaminants by Fe(0) focus on aqueous system tests. However, few is known about the effectiveness of these tests for degrading chlorinated contaminants such as 1,1,1-trichloroethane (TCA) in soil. In this work, the reductive degradation performance of 1,1,1-TCA by Fe(0) was thoroughly investigated in a soil slurry system. The effects of various factors including acid-washed iron, the initial 1,1,1-TCA concentration, Fe(0) dosage, slurry pH, and common constituents in groundwater and soil such as Cl^?, HCO₃ ^?, SO₄ ^2?, and NO₃ ^? anions and humic acid (HA) were evaluated. The experimental results showed that 1,1,1-TCA could be effectively degraded in 12 h for an initial Fe(0) dosage of 10 g L^?1 and a soil/water mass ratio of 1:5. The soil slurry experiments showed two-stage degradation kinetics: a slow reaction in the first stage and a fast reductive degradation of 1,1,1-TCA in the second stage. The reductive degradation of 1,1,1-TCA was expedited as the mass concentration of Fe(0) increased. In addition, high pHs adversely affected the degradation of 1,1,1-TCA over a pH range of 5.4–8.0 and the reductive degradation efficiency decreased with increasing slurry pH. The initial 1,1,1-TCA concentration and the presence of Cl^? and SO₄ ^2? anions had negligible effects. HCO₃ ^? anions had a accelerative effect on 1,1,1-TCA removal, and both NO₃ ^? and HA had inhibitory effects. A Cl^? mass balance showed that the amount of Cl^? ions released into the soil slurry system during the 1,1,1-TCA degradation increased with increasing reaction time, suggesting that the main degradation mechanism of 1,1,1-TCA by Fe(0) in a soil slurry system was reductive dechlorination with 1,1-DCA as the main intermediate. In conclusion, this study provides a theoretical basis for the practical application of the remediation of contaminated sites containing chlorinated solvent.     

Dechlorane Plus in surface soil of North China: levels,isomer profiles,and spatial distribution

Eighty-seven soil samples collected from North China were analyzed for Dechlorane Plus (DP). The concentrations of DP ranged from not detectable (ND) to 12.21 ng/g with a mean of 0.55 ng/g. The mean concentrations of total DP and syn-DP in four regions of North China were in the following order: Jingjin (Beijing and Tianjin)?>?Shandong?>?Shanxi?>?Hebei, while the mean concentrations of anti-DP in the four regions were in a different order: Shandong?>?Jingjin?>?Shanxi?>?Hebei. The mean f _syn values for Jingjin (0.27), Hebei (0.24), and Shanxi (0.24) were close to 0.25, while the mean f _syn value for Shandong (0.31) was closer to 0.35. In addition, the f _syn value for Shandong was significantly higher (P?<?0.01) than those of the other regions (Jingjin, Heibei, and Shanxi), indicating specific sources of DP. Syn-DP displayed a strong linear relationship with anti-DP (R ²?=?0.74), indicating that no obvious stereoselective process occurred in the soil of North China. Ordinary kriging was undertaken to map the spatial patterns of DP. High concentrations of DP in soils were present in south of Shanxi, central Hebei, south of Tianjin, and the south and northeast of Shandong, which were suggested to be connected with human activities such as e-waste dismantling.     

Trends in primary particulate matter emissions from Canadian agriculture

Particulate matter (PM) has long been recognized as an air pollutant due to its adverse health and environmental impacts. As emission of PM from agricultural operations is an emerging air quality issue, the Agricultural Particulate Matter Emissions Indicator (APMEI) has been developed to estimate the primary PM contribution to the atmosphere from agricultural operations on Census years and to assess the impact of practices adopted to mitigate these emissions at the soil landscape polygon scale as part of the agri-environmental indicator report series produced by Agriculture and Agri-Food Canada. In the APMEI, PM emissions from animal feeding operations, wind erosion, land preparation, crop harvest, fertilizer and chemical application, grain handling, and pollen were calculated and compared for the Census years of 1981-2006. In this study, we present the results for PM10 and PM2.5, which exclude chemical application and pollen sources as they only contribute to total suspended particles. In 2006, PM emissions from agricultural operations were estimated to be 652.6 kt for PM10 and 158.1 kt for PM2.5. PM emissions from wind erosion and land preparation account for most of PM emissions from agricultural operations in Canada, contributing 82% of PM10 and 76% of PM2.5 in 2006. Results from the APMEI show a strong reduction in PM emissions from agricultural operations between 1981 and 2006, with a decrease of 40% (442.8 kt) for PM10 and 47% (137.7 kt) for PM2.5. This emission reduction is mainly attributed to the adoption of conservation tillage and no-till practices and the reduction in the area of summer fallow land.     

Comparison of on-road emissions for B-0, B-10, and B-20 in transit buses

Biodiesels are often marketed as being cleaner than regular diesel for emissions. Emission test results depend on the biodiesel blend, but laboratory tests suggest that biodiesels decrease particulate matter, carbon monoxide, hydrocarbons, and air toxins when compared to regular diesel. Results for the amount of oxides of nitrogen (NOx) have been less conclusive. Tests have also not evaluated the commonly available ranges of biodiesel blends in the laboratory. Additionally, little information is available from on-road studies, so the effectiveness of using biodiesels to reduce actual emissions is unknown. A more complex relationship exists between engine operation and the rate of emission production than is typically evaluated using engine or chassis dynamometer tests. On-road emissions can vary dramatically because emissions are correlated to engine mode. Additionally, activity such as idling, acceleration, deceleration, and operation against a grade can produce higher emissions than more stable engine operating modes. Because these modes are not well captured in a laboratory environment, understanding on-road relationships is critical in evaluating the emissions reductions that may be possible with biodiesels. More tests and quantifications of the effects of different blends on engine and vehicle performance are required to promote widespread use of biodiesel. The objective of this research was to conduct on-road tests to compare the emission impacts of different blends of biodiesel to regular diesel fuel under different operating conditions. The team conducted on-road tests that utilized a portable emissions monitoring system that was used to instrument transit buses. Regular diesel and different blends of biodiesel were evaluated during on-road engine operation by instrumenting three in-use transit buses, from the CyRide system of Ames, Iowa, along an existing transit route.     

NaClO2/NaClO复合吸收液同时脱硫脱硝

针对NaClO2氧化吸收法脱硫脱硝成本过高,难以实现工业化的现状,提出了以NaClO2/NaClO为复合吸收剂的同时脱硫脱硝新方法,比单独NaClO2方法效率高,成本低。考虑实际工况条件,给定SO2与NO的初始浓度分别为2 850 mg/m3和670 mg/m3。结果表明,吸收液初始pH为6.0,液气比L/G为20 L/m3,反应温度为55℃时,平均脱硫脱硝效率分别可达99.8%和94.0%。在此基础上对反应机理进行了分析,总结出实验反应主反应方程式。该方法设备简约,操作简单,容易实现全自动控制,综合成本可以接受,比较适合中小型燃煤锅炉的烟气污染治理。     

氢氧化钠-钢渣双碱法烧结烟气脱硫工艺

在鼓泡反应器中考察了氢氧化钠-钢渣双碱法烧结烟气脱硫的主要影响因素。结果表明,在温度为常温,钢渣反应时间为2 h,钢渣加入量为40 g,SO2进口浓度为2 400 mg/m3,钢渣粒径为200目以上,烟气流量为0.05 m3/h,循环液pH保持在7～8,Na+浓度为0.5 mol/L,循环液为500 mL的条件下,脱硫率可长时间保持在80%以上。同时,对钢渣-氢氧化钠双碱法烧结烟气脱硫机理进行了探讨。     

001×14.5离子交换树脂对镍(Ⅱ)的吸附

实验采用离子交换树脂法吸附镍(Ⅱ),树脂选型确定了强酸性阳离子交换树脂001×14.5对镍(Ⅱ)吸附容量最大.用所选的001×14.5树脂吸附镍(Ⅱ)的过程,静态吸附实验表明,转速大于100 r/min时,对树脂吸附的影响可忽略,即基本消除外扩散,pH =7.0时吸附最佳,镍(Ⅱ)吸附率随树脂用量的增加而增大;001×14.5树脂吸附镍(Ⅱ)过程符合Langmuir等温吸附方程,且为优惠吸附;吸附过程符合拟二级动力学模型,吸附过程活化能为E=30.9 kJ/mol,由颗粒内扩散控制;用1 mol/L的硫酸对吸附饱和树脂进行脱附再生,脱附率可达98％以上.