空心菜浮床栽培对集约化养殖鱼塘水质的影响

以叶绿素a(Chla)、TN、NH4+-N、NO2-N、NO3-N、TP、PO43-P、CODMn等为主要水质指标研究浮床栽培空心菜对集约化养殖鱼塘的净化作用。结果表明,通过4次收获,空心菜产量可达69618.0～73161.6kg.hm-2;空心菜覆盖率为10%和20%处理组通过收获空心菜直接从1hm2养殖池塘中移出的TN分别为27.51、52.35kg,TP分别为2.83、5.39kg。在相同监测时间下,Chla、TN、NH4+-N、NO2-N、NO3-N、TP、PO43-P、CODMn等各项水质指标按对照组、10%处理组、20%处理组的顺序均呈逐渐降低趋势;其中20%处理组对Chla、TN、NH4+-N、NO2-N、NO3-N、TP、PO43-P、CODMn的去除率分别为15.16%～49.02%、9.04%～36.56%、19.23%～46.34%、22.76%～47.74%、13.33%～56.52%、33.33%～45.10%、27.27%～48.15%、3.13%～19.05%。与对照塘相比,处理塘鱼类成活率明显提高,说明在主养鱼为鲫鱼的苗种养殖池塘中采用浮床栽培空心菜能够促进水体物质循环,加强...     

Analysis of Socioeconomic and Environmental Impacts of Waste Stabilization Pond and Unrestricted Wastewater Irrigation: Interface with Maintenance

The effluent from the waste stabilization ponds (WSPs) of the University of Nigeria, Nsukka Campus, is used for irrigation by poor rural farmers. There has been fear that the poorly maintained WSPs and the reuse practices are contributing to environmental degradation and health hazards. In this study the environmental and socioeconomic impacts of the WSPs and reuse were evaluated based on data collected from questionnaires and the literature. The engineering and agricultural properties of soil in the irrigated and nonirrigated areas were compared. Comparison of the health status of the farmers and nonfarmers, of consumers of crops irrigated with wastewater and nonconsumers was performed using Student's t test and the z-score test. The occurrences of diarrhea, typhoid fever, and malaria among the various groups were used as indices. Analyses show that the health status of the farmers and consumers is poorer than those of nonfarmers and nonconsumers at the 5% level of significance. Vegetable cultivation using WSP effluent is a means of sustenance to the farmers and provides an affordable means of satisfying their nutritional deficiencies. However, the poorly maintained WSPs create odor and mosquito nuisances, trap and destroy livestock, and flood nearby compounds with waste debris. At both 1% and 5% levels of significance, communities around the ponds (< 300 m) suffer malaria more frequently than those who live far away (> or = 300 m). Cost-benefit analysis argues in favor of improvement of WSP management and irrigation reuse of wastewater. Dredging of the ponds, training workers and farmers, and adopting appropriate maintenance and monitoring strategies will greatly enhance the socioeconomic status of the urban poor farmers.     

World copper market, 1973–1982, and international stabilization policies

This article critically examines international price stabilization policy in relation to the main features of the world copper market and the structural changes that have affected the industry in the decade up to 1982. The first section summarizes the main features of the world copper market, briefly discussing the principal structural changes; the second part examines the recent pattern of investment in copper and changes in ownership of some copper producing companies resulting from the need for improved cash flows due to the adverse effects of the recession; and the third part analyses the practical and theoretical issues relating to the question of price instability. A number of formidable problems are likely to arise from such price stabilization policies and it is concluded that it is because of these difficulties that the policies have not been implemented. Consequently, international commodity agreements designed to minimize or avoid price instability have proved difficult to conclude. New questions on which consensus is likely should be examined to promote intergovernmental co-operation, and hence market stability. With that end in view, this article lists some new questions that could form the basis of an agenda for exploratory intergovernmental discussions on copper.     

菱塘养鱼技术研究

报导了“菱塘养殖”的某些关键技术。它们包括：（１）通过品种结构调整，解决鱼菱相克的矛盾；（２）通过在菱群落“开天窗”，避免鱼窒息致死；（３）实行混合养殖，拓宽生态位；（４）通过鱼种投放量与鱼产量关系的研究，为鱼种合理搭配提供了科学依据。由于上述问题的解决，这种农业模式发挥了明显的经济效益。     

小海高位池沉积物中重金属分布与污染评价

通过分析8个小海高位池养殖区的采样点沉积物中7个典型重金属污染物的含量,采用单因子指数法和Hakanson生态风险指数法,定量确定养殖池沉积物中重金属的污染程度和潜在生态风险程度。结果表明,沉积物中主要的重金属污染因子是Cu、Pb,污染指数分别为1.14和1.08;其重金属影响因子的顺序为CuPbCdHgZnCrAs,属于轻度污染;主要潜在生态风险因子为Cd,各种重金属的潜在生态危害系数大小顺序为CdHgCuPbAsCrZn,潜在生态风险指数RI平均值为41.12,属于低潜在生态风险。     

屠宰生产废水治理技术应用研究

某禽类屠宰厂年屠宰加工肉鸡3000万只,根据屠宰废水有机物浓度较高,可生化性好的特点,选择了"水解酸化+A/O工艺+接触氧化池"处理工艺。运行结果表明,经该工艺处理后,废水中的COD、BOD5、氨氮等指标均能达标排放,有利于企业的可持续发展。     

An overview for the utilization of wastes from stainless steel industries

Significant quantities of wastes are generated as the waste materials or byproducts every day from stainless steel processes. According to the origins and characteristics, the stainless steel wastes can be mainly classified into two categories, slags and dusts. They usually contained considerable quantities of valuable metals and materials. This paper summarized and analyzed the generation, composition, characteristics and the leaching behaviors of the most of wastes obtained from the stainless steel processes. On this basis, a review of several methods for treating the various stainless steel wastes was made. It is very essential not only for recycling the valuable metals and mineral resources but also for protecting the environment.     

曝气稳定塘处理农村生活污水曝气控制条件研究

通过试验研究曝气稳定塘处理农村生活污水水力停留时间、曝气过程中塘内溶解氧和污泥浓度分布以及不同曝气周期对处理效果影响等问题,以期获得较好的处理效果和经济的能耗.结果表明,本试验曝气稳定塘条件下,4 d为本曝气稳定塘的最佳水力停留时间,间歇运行中曝气时间应该大于15 min,曝气稳定塘中各点在2～10 min内污泥浓度可逐渐达到平稳,各污染物去除效果最好的曝气周期为0.5 h曝气/1.0 h停气.     

中线式尾矿库洪水漫顶溃坝演化规律模拟研究

为了解中线式尾矿库洪水漫顶溃坝的过程和机理,并提出可行的工程措施,以某中线式尾矿库及下游周边环境为研究对象,采用物理模型试验和数值模拟法对中线式与上游式尾矿库安全性进行对比研究。研究结果表明:由于中线式尾矿库外坝坡堆积粗尾砂的渗透系数偏大,其较上游式尾矿库溃口发展的速率更快,溃坝过程持续时间约14.5 h,坝顶被泄流冲刷形成的溃口宽约289 m,尾矿库下游沟道研究范围内尾矿淤积约871万m3,大量的尾矿仍滞留在库内;采用数值模拟得出的演化趋势与物理模型试验基本一致,但数值模拟计算的尾砂流动速度较快;在拦砂坝下游修建应急拦砂坝工程,物理模型试验表明拦滞尾矿洪水时间约38 min,数值模拟结果表明拦滞尾矿洪水时间约16 min,因此应急拦砂坝措施可有效延长应急逃生时间,减轻溃坝对下游居民的影响。     

退役铀尾矿库环境稳定性分析及应用

为了对退役铀尾矿库的环境稳定性进行分析,以某退役铀尾矿库为实例,在收集了连续3年环境监测数据的基础上,通过因子分析法对影响铀尾矿库环境稳定的13个指标进行了筛选,确定了p H值等6个主要指标,并利用层次分析法确定了各指标的权重。利用模糊数学理论求出了概率α=0.9时各指标的稳定区间,通过构造函数算出了铀尾矿库环境稳定率随时间的变化情况。结果表明,该铀尾矿库的环境稳定性整体较差,仍需进一步加强治理。