介孔碳修饰石墨电极处理模拟硝基苯废水

采用水热合成—高温碳化—涂饰的方法制备了介孔碳修饰石墨电极,并将其用于模拟硝基苯废水的电化学处理,考察了废水pH、电流密度、电解质投加量对处理效果的影响。表征结果显示,修饰电极表面具有丰富的介孔结构,因而比石墨电极具有更高的硝基苯去除率和苯胺生成量。实验结果表明,在废水pH为7.0、电流密度为15 mA/cm~2、电解质硫酸钠投加量为1.775 g/L的条件下处理初始硝基苯质量浓度为100 mg/L的模拟废水,电解3.0 h时的硝基苯去除率高达99.6%,苯胺生成量最高达45.54 mg/L。     

用Ti/SnO2-RuO2电极处理黑索金废水

利用刷涂法制备了Ti/SnO2-RuO2电极,并通过SEM、XRD等测试手段对其进行形貌及结构表征。利用该电极为阳极处理黑索金(RDX)废水,考察了电解质种类、电解质质量浓度、废水pH、电流密度以及电解时间等对RDX电催化氧化效果的影响。实验结果表明,当处理100 mL质量浓度为50 mg/L的RDX废水时,以Na2SO4为电解质、Na2SO4质量浓度为5.0 g/L、废水pH为7、电流密度为15 mA/cm2、电解时间为300 min的条件下,RDX去除率达到82.55%,COD去除率达到55.41%。     

Ti/MnO2/PbO2电极的制备及电催化降解罗丹明B

采用电沉积法制备了Ti／MnO2／PbO2电极，并用其对质量浓度为20mg／L的罗丹明B模拟废水进行了电催化降解实验。实验结果表明：原水pH为4．95，无须调节废水的pH；最佳电解实验条件为：支持电解质NazSO4浓度0．09mol／L，电解电流密度40mA／cm^2，处理时间40min，在此条件下罗丹明B的去除率接近100％。     

电化学法处理高盐苯酚废水的研究

对在氯盐电解质中用电化学方法处理含酚废水进行了研究，着重探讨了盐的种类与浓度、反应温度与溶液：pH、电流密度、苯酚初始浓度及阴阳极转换频率对苯酚去除率的影响。在Na2SO4的浓度为0．2mol／L，NaCl的浓度为0．1mol／L、苯酚初始质量浓度为200mg／L、电流密度为0．04A／cm^2、温度为35℃、pH为12．5、阴阳极转换频率为5min/次及反应时间为200min的条件下，苯酚的去除率为99．5％，COD去除率为5％，CIO^-把苯酚氧化成了其他有机化合物。     

Fenton试剂降解选矿废水中残余黄药

采用Fenton试剂处理选矿废水中残余的黄药,分别考察了氧化时间、反应初始pH、Fe^2 浓度及H2O2用量对黄药降解效果的影响;用正交实验确定了4个因素的最佳条件。结果表明,反应初始pH和H2O2用量是影响黄药去除效果的主要因素。氧化时间为60min、反应初始pH为4、Fe^2 质量浓度为20mg／L、H2O2质量浓度为20mg／L、黄药质量浓度为：125mg/L时,黄药的去除率达到99．5％,COD去除率为87．5％。     

电化学转盘法处理活性艳红X-3B废水

采用电化学转盘法处理模拟活性艳红X-3B染料废水，考察了电解槽电压、电化学转盘转速、废水pH、电解时间、电导率等因素对废水色度、总有机碳（TOC）去除率的影响。在废水pH为6、电解槽电压17V、电化学转盘转速70r／min、电导率1500μs／cm、电解时间60min的条件下，废水色度和TOC去除率分别达98．2％和57．2％。通过对活性艳红X-3B紫外-可见吸收光谱的分析，探讨了活性艳红X-3B的降解机理。     

电催化氧化法处理阴离子表面活性剂废水

采用自制电化学反应器对阴离了表面活性剂废水的电催化氧化处理进行了研究,考察了阳极材料、电解电压、电解时间、电极间距离、废水pH、废水电导率等对阴离子表面活性剂电解去除效果的影响,确定了最佳的处理条件。在电解电压为8V、电解时间为30～40min、电极间距离为2cm、废水pH为8～10、废水电导率为0．620ms／cm的条件下,阴离子表面活性剂的电解处理去除率可达96％以上。     

电生成Fenton试剂处理染料废水

对电生成Fenton试剂处理酸性铬兰K染料废水进行了研究。采用石墨作阴、阳极,电解过程中向阴极表面通纯氧,并在废水中加入-定量的Fe2+,氧在阴极上还原生成H2O2,H2O2又产生强氧化剂·OH,进而对酸性铬兰K染料废水进行脱色降解。在槽电压为6 V、pH为2.5、电解液中FeSO4·7H2O的质量浓度为0.5 g／dm3、Na2SO4的质量浓度为20 g／dm3的条件下电解废水60 min,染料废水脱色率和COD去除率分别达74.1％和57.9％,电解废水120min后,染料废水脱色率和COD去除率分别达92.9％、71.3％。动力学研究表明,染料的降解符合一级动力学过程,速率常数k为0.02224 min-1。     

非均相催化氧化处理焦化废水

研究了非均相催化氧化处理焦化废水的效果。实验得出处理焦化废水的最佳条件：采用经质量浓度为80g／L的硝酸铜溶液浸渍后的γ—Al2O,为催化剂,废水pH为3,催化剂体积分数为40％,H2O2体积分数为4％,反应时间3h以上。原水经处理后COD由4540mg／L降至600mg／L以下,氨氮质量浓度由552mg／L降至160mg／L以下。     

三元微电解—Fenton试剂氧化法深度处理石化废水

采用三元微电解-Fenton试剂氧化法处理COD为60 ～ 90 mg/L的石化废水.三元微电解工艺最优条件为:m(铝屑)∶m(铁屑)∶m(活性碳)=1∶2∶2,废水初始pH 4 ～5,微电解时间45 min.Fenton试剂氧化工艺最优条件为:H2O2加入量0.6mL/L,废水pH 4,氧化时间30 min.在此条件...     

Distribution of Cd,Ck, Pb and Zn in Soil and Vegetation Compartments in Stands of Five Boreal Tree Species in N.E. Sweden

Concentrations and total quantity of cadmium (Cd), cupper (Cu),lead (Pb) and zink (Zn) were determined in biomass and soil compartments in a replicated tree species experiment with 27-yr-old stands growing on former farmland in N.E. Sweden. Sequentialextractions of soil samples were performed in order to estimate the exchangeable and an organically bound fraction of each element. The tree species included were Picea abies (L.)H. Karst., Pinus sylvestris L., Pinus contorta Dougl., Larix sibirica Ledeb., and Betula pendula Roth.Tree species influenced the rate of removal of Cu, Pb and Zn incase of stemwood harvesting, and of Cd, Cu and Zn in the case ofwhole-tree harvesting. B. pendula and P. abies had higher quantities and average concentrations of Zn in the biomass. For all species, >50% of the Zn in the stems was found in the bark. P. abies and L. sibirica had higher quantities of Cu in the biomass than the other species.P. abies and P. contorta had high quantities of Cd inthe biomass in relation to the other species. Branches and stembark contained high concentrations of Cd and Pb in relation to foliage and stemwood. Dead branches had especially high concentrations of Pb. The high accumulation rate of Zn in thebiomass of B. pendula was related to a low exchangeable amount of Zn in the A horizon. In the superficial centimeters ofthe A horizon, a depletion similar to that found for Zn was detected for Cu, whereas for Cd and Pb, no correlations were found between quantities of elements in the trees and element pools in the soil.     

Programs assessing implementation and effectiveness of state forest practice rules and BMPs in the West

The major forest nonpoint source control programs in the West are largely regulatory, either under forest practices acts (California, Idaho, New Mexico, Nevada, Oregon, and Washington) or a streamside management act (Montana). These programs and the specific rules they enforce continue to undergo intensive scrutiny. Still, the questions are the same for these regulatory programs as for states that base nonpoint source control on voluntary BMPs (Arizona, Colorado, Utah, Wyoming). Are the rules or BMPs being applied, and are they effective in reducing nonpoint source pollution to levels that protect beneficial uses of water? The level of debate about forestry in the West has resulted in detailed monitoring and research to answer these questions. In the past, state agencies have assumed levels of BMP compliance based on the percent of operations without enforcement actions. These estimates are being replaced by statistically valid and reproducible monitoring of forest practices rules and BMP compliance levels. BMP effectiveness is being assessed using both qualitative and quantitative methods. This can involve field assessments, process-based research, and control watershed studies. Some trend monitoring is also beginning. With the regional implementation rate for forestry BMPs at about 94% and rising, it is likely that effectiveness testing will continue to be a priority and consume the majority of assessment resources for this region.     

Hysteresis in Reversal of Central European Mountain Lakes from Atmospheric Acidification

Extremely high emissions of S and N compounds in Central Europe (both 280 mmol m^-2 yr^-1) declined by 70and 35%, respectively, during the last decade. Decreaseddeposition rates of SO₄ ^-2, NO₃ ^-, and NH₄ ⁺ in the region paralleled emission declines. The reduction in atmospheric inputs of S and N to mountain ecosystemshas resulted in a pronounced reversal of acidification in the Tatra Mountains and Bohemian Forest lakes. Between the 1987–1990and 1997–1999 periods, concentrations of SO₄ ^-2 and NO₃ ^- decreased (average ± standard deviation) by 22±7 and 12±7 mol L^-1, respectively, in theTatra Mountains, and by 19±7 and 15±10 mol L^-1, respectively, in the Bohemian Forest. Their decrease was compensated in part (1) by a decrease in Ca²⁺ + Mg²⁺ (17±7 mol L^-1) and H⁺ (4±6 mol L^-1), and an increase in HCO₃ ^-(10±10 mol L^-1) in the Tatra Mountains lakes, and (2) by a decrease in Al (7±4 mol L^-1), Ca²⁺ + Mg²⁺ (9±6 mol L^-1), and H⁺ (6±5 mol L^-1), in Bohemian Forest lakes. Despite the rapid decline in lake water concentrations of SO₄ ^-2 and NO₃ ^- in response to reduced S and N emissions, their present concentrations in some lakes are higher than predictionsbased on observed concentrations at comparable emission rates during development of acidification. This hysteresis in chemical reversal from acidification has delayed biological recovery of the lakes. The only unequivocal sign of biological recovery hasbeen observed in erné Lake (Bohemian Forest) where a cladoceran species Ceriodaphnia quadrangular has recentlyreached its pre-acidification abundance.     

Reconstruction of Long-Term Changes in Lake water Chemistry,Zooplankton and Benthos of a Small,Acidified High-Mountain Lake: Magic Modelling and Palaeolimnogical Analysis

Starolesnianske pleso is a small and shallow acid lake in the High Tatra Mountains, situated at 2000 m above sea level, on granitic bedrock, with sparse and thin soil cover. When detailed measurements began in the 1980s Starolesnianske pleso had pH below 5 and only one species of cladoceran zooplankton, the ubiquitous Chydorus sphaericusPalaeolimnological investigations show changes in cladoceran zooplankton and chironomid zoobenthic assemblages since about 1920 and a major change in 1970–1980. The dynamic acidification model MAGIC was used to reconstruct changes in water chemistry over the past 150 years. The results from MAGIC agree well with the sediment record; pH levels gradually decreased from 6.5 in the mid-1800s to about 5.6 in 1920 (first response in biota) to below 5.0 by 1970, and concentrations of inorganic aluminium rose dramatically beginning about 1960. In the 1990s the lake water chemistry showed clear signs of reversal in acidification brought about by a major decline in S deposition.     

Heavy Metals Removal by Biosorption and Flotation

The removal of a mixture of heavy (toxic) metal cations (copper, nickeland zinc) from liquid effluents was investigated in this study at pilotscale, using counter-current contact mode. The innovative processinvolved the abstraction of metal ions onto fungal biosorbents, followedby the application of flotation for the subsequent solid/liquid separationof biomass particles. The ability of microorganisms to remove metal ionsfrom aqueous solutions is a well-known phenomenon. Nevertheless,engineering considerations are very important in decisions, concerningthe commercial future of biosorption and practical solutions are neededfor certain problems, such as the efficient post-separation ofmetal-loaded biomass. The two processes (flotation and biosorption) caneffectively operate in combination, in what it was termed biosorptiveflotation process. The sorbents may be recycled, after appropriate elutionof metals, as well as the treated (clean) water.     

Starch-plastic materials—Preparation,physical properties,and biodegradability (a review of recent USDA research)

Recent starch-plastic research at the National Center for Agricultural Utilization Research is reviewed and related worldwide efforts are noted. Properties of starch that influence its formulation and performance in plastics are discussed. Methods are given for preparation of starch-poly(methyl acrylate) graft copolymer, starch-poly(ethylene-co-acrylic acid), and starch-poly(ethylene-co-acrylic acid)-polyethylene plastics. Their physical properties are discussed, as is degradability by enzymes or amylolytic organisms from soil, ponds, and streams.The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

High Immobilization of NH4+ in Danish Heath Soil Related to Succession,Soil and Nutrients: Implications for Critical Loads of N

During recent decades heathlands havechanged into grasslands in regions with high atmosphericnitrogen deposition. In regions with intermediatedeposition level (e.g., Denmark) changes have been lesspronounced which may be due to delay or decrease inresponse of the ecosystem. The mor layer (O horizon) mayplay an important role for this delay due to high sinkstrength for N. In this study, the capacity for netNH₄ ⁺ immobilization and mineralization wasstudied during short- and long-term incubations (2–36 days)of mor samples from Danish dry inland heaths. High short-term capacity for net NH₄ ⁺ immobilization wasfound to be a general characteristic of Danish heath morlayers both under heather (Calluna vulgaris) andcrowberry (Empetrum nigrum ssp nigrum), the latterdominating late stages in heathland succession. The netNH₄ ⁺ immobilization was higher under youngcompared to old or dead vegetation, and higher on lessnutrient poor soils than on extremely nutrient poor soils.The addition of N, P and C stimulated CO₂ productionand net NH₄ ⁺ immobilization, but not net Nmineralization. The immobilization of ¹⁵NH₄ ⁺caused release of dissolved organic N, increased N anddecreased C/N ratio in the microbial biomass, and indicatedgrowth of microorganisms with other metabolic abilitiesthan the indigenous population. No evidence was obtained ofstabilization of immobilized ¹⁵NH₄ ⁺ intosoil organic matter during the experiment. On background ofthe results and current knowledge it was concluded that therecognition of the high capacity for net NH₄ ⁺immobilization in mor layers does not allow for a raiseof critical loads for N for northern dry inland heaths.     

Bioassessment of silvicultural impacts in streams and wetlands of the Eastern United States

Bioassessment is a useful tool to determine the impact of logging practices on the biological integrity of streams and wetlands. Measuring biota directly has an intuitive appeal for impact assessment, and biota can be superior indicators to physical or chemical characteristics because they can reflect cumulative impacts over time. Logging can affect stream and wetland biota by increasing sedimentation rates, altering hydrologic, thermal, and chemical regimes, and changing the base of food webs. Biotic impacts of logging on streams compared to wetlands probably differ, and in this paper we review some of those differences. In streams, invertebrates, fishes, amphibians, algae, and macrophytes have been used as indicators of logging impacts. In wetlands, bioassessment is just beginning to be used, and plants and birds are the most promising indicator taxa. Various best management practices (BMPs) have been developed to reduce the impacts of logging on stream and wetland biota, and we review quantitative studies that have evaluated the efficacy of some of these techniques in streams and wetlands in the eastern United States. Remarkably few studies that address the overall efficacy of BMPs in limiting biotic changes in streams and wetlands after BMP implementation have been published in scientific journals, although some work exists in reports or is unpublished. We review these works, and compile conclusions about BMP efficacy for biota from this body of research.     

Characterization of air emissions and residual ash from open burning of electronic wastes during simulated rudimentary recycling operations

Air emissions and residual ash samples were collected and analyzed during experiments of open, uncontrolled combustion of electronic waste (e-waste), simulating practices associated with rudimentary e-waste recycling operations. Circuit boards and insulated wires were handled separately to simulate processes associated with metal recovery. The average emissions of polychlorinated dibenzodioxins and dibenzofurans (PCDD/PCDFs) were 92 ng toxic equivalency (TEQ)/kg [n = 2, relative standard deviation (RSD) = 98%] and 11 900 ng TEQ/kg (n = 3, RSD = 50%) of the initial mass of the circuit boards and insulated wire, respectively. The value for the insulated wire is about 100 times higher than that for backyard barrel burning of domestic waste. The emission concentrations of polybrominated dibenzodioxins and dibenzofurans (PBDD/PBDFs) from the combustion of circuit boards were 100 times higher than for their polychlorinated counterparts. Particulate matter (PM) sampling of the fly ash emissions indicated PM emission factors of approximately 15 and 17 g/kg of the initial mass for the circuit boards and insulated wire, respectively. Fly ash samples from both types of e-waste contained considerable amounts of several metallic elements and halogens; lead concentrations were more than 200 times the United States regulatory limits for municipal waste combustors and 20 times those for secondary lead smelters. Leaching tests of the residual bottom ash showed that lead concentrations exceeded U.S. Environmental Protection Agency landfill limits, designating this ash as a hazardous waste.     

Selection of Autochthonous Plant Species from SE Spain for Soil Lead Phytoremediation Purposes

Mining activity in SE of Spain, in the west Mediterranean coast, originated more than two millenniums ago. It has generated huge areas affected by heavy metals contamination, especially of lead, which is possibly one of the most important. Investigations related to the selection of autochthonous plant taxa from a typical Spanish Mediterranean area, useful for phytoextraction and phytostabilization purposes in these polluted areas are shown. Under these edaphoclimatic conditions 12 interesting species were considered, from them six taxa were chosen for further studies. Some plant species have been proposed either for phytoextraction or phytostabilization purposes. Recommendations for further research have been discussed.