Review of information on pesticide residues in the Canadian environment

Summary Pesticide residues in soil, water, food, wildlife and other media have been analysed in several monitoring studies. The purpose was to establish the distribution of these residues across a defined area, ascertain their trend over a specific period and use the results to assess environmental compliance and safety. In the present review the availability of information on pesticide residues in various Canadian environmental components was sought. With the possible exception of localized pesticide contamination of some private water supply wells, ground and surface water, most analyses revealed concentrations below guideline limits. Only a few cases were reported of mishandling, misuse and poisoning from pesticides. Continuing surveillance programmes and in-depth and well-organized monitoring studies, with special focus on areas that are vulnerable to contamination, by both provincial and federal governments, are largely responsible for the encouraging results. This experience in the control of pesticide use and monitoring of residues in the environment should be of particular interest in developing countries.Dr A.Y. Sangodoyin is a senior lecturer in the Department of Agricultural Engineering at the University of Ibadan. He was recently involved in a study visit to the University of Alberta, Edmonton, Alberta, Canada T6G 2G7, where his co-author Dr D.W. Smith is a member of staff in the Department of Civil-Engineering.     

从废感光胶片中回收银

研究了以Fe3 -乙二胺四乙酸二钠-N a2S2O3体系为浸取剂从废感光胶片中回收银的方法,考察了浸出银的最佳工艺条件。实验表明,当浸取剂中FeC l3.6H2O质量浓度为35g/L、N a2S2O3.5H2O质量浓度为150g/L、pH为7、固液质量比为3∶10时,浸取剂可重复使用6次,胶片上银的浸出率可达99%以上;浸取液中的银采用硼氢化钠还原回收,粗银粉配以熔剂高温熔炼可得到纯度达99.78%的银,银回收率达96.88%,回收银后的浸取液可循环使用。     

Enzyme-Retted Flax Fiber and Recycled Polyethylene Composites

Municipal solid wastes generated each year contain potentially useful and recyclable materials for composites. Simultaneously, interest is high for the use of natural fibers, such as flax (Linum usitatissimum L.), in composites thus providing cost and environmental benefits. To investigate the utility of these materials, composites containing flax fibers with recycled high density polyethylene (HDPE) were created and compared with similar products made with wood pulp, glass, and carbon fibers. Flax was either enzyme- or dew-retted to observe composite property differences between diverse levels of enzyme formulations and retting techniques. Coupling agents would strengthen binding between fibers and HDPE but in this study fibers were not modified in anyway to observe mechanical property differences between natural fiber composites. Composites with flax fibers from various retting methods, i.e., dew- vs. enzyme-retting, behaved differently; dew-retted fiber composites resulted in both lower strength and percent elongation. The lowest level of enzyme-retting and the most economical process produces composites that do not appear to differ from the highest level of enzyme-retting. Flax fibers improved the modulus of elasticity over wood pulp and HDPE alone and were less dense than glass or carbon fiber composites. Likely, differences in surface properties of the various flax fibers, while poorly defined and requiring further research, caused various interactions with the resin that influenced composite properties.     

Tillage erosion and its effect on soil properties and crop yield in Denmark

Tillage erosion had been identified as a major process of soil redistribution on sloping arable land. The objectives of our study were to investigate the extent of tillage erosion and its effect on soil quality and productivity under Danish conditions. Soil samples were collected to a 0.45-m depth on a regular grid from a 1.9-ha site and analyzed for 137Cs inventories, as a measure of soil redistribution, soil texture, soil organic carbon (SOC) contents, and phosphorus (P) contents. Grain yield was determined at the same sampling points. Substantial soil redistribution had occurred during the past decades, mainly due to tillage. Average tillage erosion rates of 2.7 kg m(-2) yr(-1) occurred on the shoulderslopes, while deposition amounted to 1.2 kg m(-2) yr(-1) on foot- and toeslopes. The pattern of soil redistribution could not be explained by water erosion. Soil organic carbon and P contents in soil profiles increased from the shoulder- toward the toeslopes. Tillage translocation rates were strongly correlated with SOC contents, A-horizon depth, and P contents. Thus, tillage erosion had led to truncated soils on shoulderslopes and deep, colluvial soils on the foot- and toeslopes, substantially affecting within-field variability of soil properties. We concluded that tillage erosion has important implications for SOC dynamics on hummocky land and increases the risk for nutrient losses by overland flow and leaching. Despite the occurrence of deep soils across the study area, evidence suggested that crop productivity was affected by tillage-induced soil redistribution. However, tillage erosion effects on crop yield were confounded by topography-yield relationships.     

化学溶胀法分离废弃线路板中金属与基板

废弃线路板的粉碎和所含金属组分的高效解离是后续分选回收的前提条件。本研究分别使用乙二胺等10种溶剂浸泡废弃线路板,比较对线路板中铜箔与基板间剥离强度的影响,从而筛选出4种有代表性的溶剂,即溶剂D、溶剂F、丙酮和水, 比较废弃线路板经化学溶胀后的单体解离度和获得一定粒径分布的颗粒所需的破碎时间。研究结果表明,化学溶胀后破碎能大幅提高金属的单体解离度,浸泡效果的优良排序为：溶剂D>溶剂F>丙酮>水;浸泡时间越长,浸泡温度越高,对剥离强度的降低越有利;使用溶剂D在150℃、3 h或140℃、5 h的工艺下浸泡废弃线路板,可以使铜箔与基板自动脱落。研究结果为后续的分选提供了便利的条件。     

Electrochemical oxidation of bisphenol A. Application to the removal of bisphenol A using a carbon fiber electrode

Leachate samples with a high strength of ammonium-nitrogen (NH4+-N) were collected from a local landfill site in Hong Kong. Two experiments were carried out to study (1) the inhibition of microbial activity of activated sludge by NH4+-N and (2) the chemical precipitation of NH4+-N from leachate as a preliminary treatment prior to the activated sludge process. The experimental results demonstrated that the efficiency of COD removal decreased from 97.7% to 78.1%, and the dehydrogenase activity of activated sludge decreased from 9.29 to 4.93 microg TF/mg MLSS, respectively, when the NH4+-N concentration increased from 53 to 800 mg/l. The experiment also demonstrated that the NH4+-N in the leachate can be quickly precipitated as MgNH4PO4 x 6H2O after addition of MgCl2 x 6H2O + Na2HPO4 x 12H2O. The NH4+-N concentration was reduced from 5618 to 112 mg/l within 15 min when a molar ratio of Mg2+:NH+:PO4(3-) = 1:1:1 was used. The optimum pH to reach the minimum solubility of MgNH4PO4 x 6H2O was found to be in the range of 8.5-9.0. Attention should be given to the high salinity formed in the treated leachate by using MgCl2 x 6H2O + Na2HPO4 x 12H2O, which may affect microbial activity in the following biological treatment processes. Using two other combinations of chemicals [MgO + 85%H3PO4 and Ca(H2PO4)2 x H2O + MgSO4 x 7H2O] could minimise salinity generation after precipitation, while they were less efficient for NH4+-N removal.     

Biomarker responses and reproductive toxicity of the effluent from a Chinese large sewage treatment plant in Japanese medaka (Oryzias latipes)

The present study was conducted to assess the potential toxicity of the effluent from a large sewage treatment plant (GBD-STP) in Beijing. Japanese medakas (Oryzias latipes) at reproduction active period were exposed to a serial of graded concentrations of the effluent or 100 ng l-1 of 17-alpha-ethinylestradiol (EE2, positive control). Growth, gonadosomatic index (GSI), hepatosomatic index (HSI), reproductive success, induction potency of vitellogenin (VTG) in male fish and that of 7-ethoxyresorufin-o-deethylase activity (EROD) in male fish liver were used as test endpoints. The growth suppression of fish was observed in a dose-dependent manner, resulting in significant differences in both body length and body weight of medaka above 5% effluent. This effluent can inhibit the growth of gonad of medakas and are more sensitive to male than to female. At exposure concentration of 40% and higher, there was an unexpected decrease of HSI values, which may be resulted from sub-lethal toxicity of effluent to fish liver. VTG of plasma in males were induced in all exposure concentration levels, but not in a dose-dependent manner. The concentration of 5% effluent would be the lowest observed adverse effect level (LOAEL) affecting reproductive success when examining fertile individuals, fecundity and fertilization rate. The overt CYP1A response and higher reproductive toxicity may be indicative of low process efficiency of this STP.     

Municipal solid waste characteristics and management in China

The purpose of this investigation is to evaluate the current status and identify the problems of municipal solid waste (MSW) management in China in order to determine appropriate remedial strategies. This is the first of two papers, discussing primarily the general characteristics of MSW and its management in China. The second paper focuses on specific remedial strategies. MSW generation in China has increased rapidly in the past 20 years from 31.3 million tons in 1980 to 113.0 million tons in 1998. The annual rate of increase is 3-10%. The average generation per capita is 1.0 kg/day (0.38 t/year). Nearly one-half of the waste generated is dumped in the suburbs, where the accumulated quantity has reached 6 billion tons, which has caused heavy environmental pollution. This paper provides information on MSW management in China, such as MSW generation and its physical, chemical, and biological properties. Low calorific value and high moisture content characterize China's municipal waste. Other issues related to MSW management in China are also discussed, including the factors that influence MSW generation quantity and