Assessment of groundwater quality and its variations in the capture zone of a pumping well in an agricultural area

Agricultural activities are frequently associated with water contamination. The spreading and storage of fertilizers, for instance, may result in groundwater contamination due to pollutants leaching into an aquifer. Nitrates and fecal bacteria are two important contaminants associated with agriculture. Thus, the development of efficient strategies for groundwater protection in agricultural areas requires an assessment of these two contaminants. Given this perspective, groundwater quality monitoring was carried out over the whole capture zone of a municipal well located in an agricultural area in the St.-Lawrence Lowlands in Québec. Thirty-eight piezometers were installed within the roughly 2 km² capture area of the well to measure physico-chemical parameters such as major ions, field measured parameters (pH, electrical conductivity, dissolved oxygen, water level, temperature), and isotopic ratios, bacteriological parameters (Heterotrophic Plate Count—HPC, enterococci, total coliforms, Escherichia coli) and their variations in space and time. Groundwater was sampled from the pumping well and the piezometers during 25 field campaigns in 2005, 2006 and 2007. The results demonstrate the impact of agricultural activities on nitrate contamination. They indicate high spatial and temporal variations in nitrate concentrations, from 6 to 125 mgNO₃⁻/L within the capture area, with 40% of the samples exceeding the Québec drinking water limit of 45 mgNO₃⁻/L. Nitrate pollution in the municipal well exceeded 45 mgNO₃⁻/L during 2005, but no bacteriological contamination was observed. The results also show a high variability of nitrate concentration with depth within the capture zone. Electrical conductivity appears as a good indicator of the presence of nitrate and calcium ions in this capture zone. Correlations between nitrate, calcium and chloride suggest that these ions come from the same source of fertilizer. Nitrate isotopic composition suggests that nitrate in groundwater originates from both chemical and organic fertilizers. The bacteriological results show that the extracted volume of water during sampling of a piezometer has a significant impact on the bacteria count. The variability of bacteriological pollution is important in space and time, showing a higher contamination during summer. Only 2% of the raw water samples exhibit contamination exceeding the drinking water standard for treated water. Total coliforms seem to be a good precursor of E. coli or enterococci contamination. Globally, the physico-chemical and bacteriological groundwater quality within the studied capture area and the pumping well shows contamination by nitrates, but low contamination levels by fecal bacteria.     

基于Web的城市污水处理厂决策支持平台研究

本研究提出了基于Web的城市污水处理厂决策支持平台的概念,开发了基于Web的污水处理决策支持系统(模拟系统与专家系统),并实现了决策支持中心的思想。文中介绍了基于Web的决策支持系统和决策支持中心的设计思想,以及利用NET技术,以单机版决策支持系统为基础进行软件开发的方法。同时本文讨论了创建决策支持平台的意义,以及在此平台上进行深入科研工作的前景。     

广州市市政建设“创园”达标分析

对照创建国家园林城市关于市政设施建设的标准，对广州市六项市政建设指标现状进行了分析，结果表明广州市各项市政建设均已达到国家园林城市标准，同时对市政建设个行业的发展重点与方向提出了一些建议。     

污泥垃圾复混肥对土壤养分状况和油菜生长及养分利用率的影响

为研究不同养分含量污泥垃圾复混肥与化肥对油菜的鲜重、干重、养分利用率及土壤速效养分含量的影响,在施肥总量(N+P2O5+K2O)相等的基础上进行盆栽试验,结果表明:20%(N+P2O5+K2O=20%)的污泥垃圾复混肥处理的油菜鲜重与干重最高,油菜对氮、磷、钾养分的利用率也最高,分别为41%,9.2%,12%,同时明显提高了土壤有机质、速效氮和速效磷的含量,但土壤速效钾含量与其它复混肥和化肥处理无明显差异。     

城市生活垃圾对石灰性褐土养分及油菜生长的影响

利用油菜盆栽试验研究了不同用量垃圾对石灰性生土和熟土全量养分、速效养分和油菜产量的影响。结果表明:随着垃圾施用量的增加,生土和熟土有机质和全氮、全磷、全钾含量都有增加的趋势,各处理与对照相比,全氮和全磷含量的差异性显著,而有机质和全钾含量的差异性不显著;随着垃圾施用量的增加,生土和熟土速效N、P、K含量都增加,且显著高于对照。施用垃圾的处理,油菜的干重和鲜重在生土和熟土上都高于对照,且提高了油菜中养分含量,特别是氮、磷元素的含量显著增加,对油菜生长具有良好的促进作用。这说明垃圾可以作为肥料资源将其农用,合理施用不仅可以提供给植物生长所需养分,提高产量,而且具有培肥改土的效果。     

长江三角洲地区城市污泥中多氯联苯和有机氯农药含量与组分研究

对我国长江三角洲地区15个主要城市的46个污泥中的多氯联苯(PCBs)和有机氯农药(OCPs)的含量与组分进行了较系统的分析,结果表明,该地区城市污泥中PCBs的含量在0~0.720mg/kg之间,平均为0.076mg/kg,大部分低于0.1mg/kg,仅2个样品中PCBs含量超过我国农用城市污泥的控制标准(0.2mg/kg)。污泥中PCBs组分以PCB44检出量最高,PCB180、PCB99、PCB52、PCB74、PCB77和PCB167次之;供试城市污泥中OCPs的含量在0~0.426mg/kg之间,平均为0.055mg/kg,大部分低于0.05mg/kg。OCPs以o,p’-DDT检出量最高,其次为p,p’-DDE、β-HCH、δ-HCH、α-HCH、γ-HCH、p,p’-DDD和p,p’-DDT。该地区城市污泥中PCBs和OCPs的含量、组分和分布与污泥类型、污水来源、污水处理工艺及化合物本身的理化性质等有关。     

广州地区生活垃圾干燥特性与动力学分析

以广州地区生活垃圾为对象在干燥箱内进行了模拟焚烧炉内干燥过程的实验研究。分析了温度对生活垃圾干燥特性的影响,采用实验数据对7种薄层干燥数学模型进行非线性拟合,获得了描述实验过程的最优干燥模型。结果表明:干燥温度越高,干燥时间越短,极值干燥速率越大。温度从100℃升高到160℃,干燥时间由322 min降至102 min,最大干燥速率由0.009 g/(g·min)升高到0.027 g/(g·min);Page,Modified page和Weibull Distribution模型可较准确地描述实验过程;通过菲克扩散模型计算出实验范围内有效扩散系数从2.212×10-9m2/s变化到8.044×10-9m2/s,由阿乌尼斯方程得出生活垃圾的活化能为27.035 kJ/mol。     

论地市级农科院所如何加快科技创新支撑现代农业发展——以湖北省恩施州农业科学院为例

文章以湖北省恩施州农业科学院为例,阐述了地市级农科院所"十一五"期间取得的成效,探讨了进一步加强农业科技创新存在的问题,如科研创新平台滞后、科研创新经费不足、科研人员待遇低、历史包袱沉重等,并针对问题提出了建设武陵山区农业科技区域创新中心、深化科技体制改革、强化人力资源建设、建好农业科技园区等发展对策。     

Variations in municipal urban forestry policies: A case study of Toronto, Canada

Urban forest conditions are driven by a range of biophysical and social factors, including urban form, socioeconomic conditions, and municipal policy. However, relatively little attention has been paid to policies, particularly those aimed at private property. The purpose of this study was to identify the types of urban tree policies that exist in the Greater Toronto Area, begin to understand why those variations may occur, and determine if such variations lead to on-the-ground differences. To address these objectives, we conducted a survey to identify policies covering the planting and removal of privately owned trees, as well as publicly owned trees along roadways in 29 municipalities. The results of the survey were then compared to census and vegetation abundance data to determine the relationship between municipal characteristics, level of policy adoption, and on-the-ground differences. We found substantial variation in the type of policies in place, with regulations addressing tree protection on private property occurring only in larger municipalities. The existence of on-the-ground differences was less clear, possibly because of the relatively recent adoption of most policies. These results highlight the need to assist smaller municipalities in developing urban forestry policies and to monitor these policies’ influence over the long term to better understand their role in shaping the urban forest.     

城市污泥堆肥商品化应用问题的探讨

讨论了国内外城市污泥的各种处理方法的利弊 ,城市污泥土地利用的可能性和有效性 ;论证了城市污泥堆肥商品化的可行性和必要性 ,并对污泥堆肥商品化应用中的安全性及质量控制等问题进行了探讨。