Mercury contamination: A human tragedy

Historically, the element, mercury, has been widely applied in industry, agriculture, and medicine. The role of mercury in technological progress and therapeutic benefits has generally been quickly accepted despite sketchy trial-and-error methods used to evaluate its overall impact. The discovery of the negative side effects of mercury, such as degradation of the environment and the accompanying threat to human health, has often been overlooked, sometimes for centuries. Mercury Contamination: A Human Tragedy (Wiley-Interscience 1977) describes both historical and current applications of quicksilver, the impact on human beings and the environment, and the social and legal efforts to reform the abuses. The following exerpts are taken from the impact of mercury on human beings and the environment in various parts of the world.     

IMPACT OF NONCHLORINATED SECONDARY AND TERTIARY EFFLUENTS ON WARM WATER FISH COMMUNITIES1

ABSTRACT: The fish communities in three sewage receiving Illinois streams were monitored by electrofishing as treatment changed from secondary with chlorination to secondary without chlorination to tertiary without chlorination over a 40-month period. Degradation of the fish communities was severe during the secondary treatment/chlorination period. When treatment was changed to secondary without chlorination, strong improvements occurred in the fish communities of all streams, and degradation could no longer be demonstrated on the basis of species number. The onset of tertiary treatment resulted in few additional changes in the fish communities, with the possible exception of increased abundance of several species of minnows. Tertiary treatment consisted of nitrification, sand filtration, and, in two streams, phosphorus removal.     

SMALL FISH MODELS FOR IDENTIFYING CARCINOGENS IN THE AQUEOUS ENVIRONMENT1

ABSTRACT: Contaminants in water and sediments can be carcinogenic to aquatic wildlife as well as humans. Identifying those carcinogens, however, is difficult because they often occur in low concentrations and exert their effects over a large part of the life span of affected organisms. Furthermore, the carcinogens are often components of complex mixtures. Recent studies suggest that laboratory-reared fish species might be well suited for testing water-associated and other carcinogens. Here, we review the principal carcinogen exposure methods that utilize small fish species or can be adapted to utilize small fish species to detect carcinogens in aqueous environments. Emphasis is placed on methods for which the end-point is tumor induction. The methods discussed are dietary exposures, skin painting, embryo microinjection, early life stage (pulse) exposures, static water exposures, flow-through exposures, and controlled field exposures. Early life stage exposures seem to have the greatest utility with regard to carcinogen sensitivity, ease of administration, disposal of test compounds, and economy of materials and effort. For certain types of carcinogens, however, long-term flow-through exposures are probably required. In summary, small fish carcinogenesis models offer an array of methodologies that can be utilized in a variety of combinations depending on compounds tested, exposure parameters employed, and end points sought.     

Relation of Lake Acidification and Recovery to Fish,Common Loon and Common Merganser Occurrence in Algoma Lakes

Models are needed that predict both spatial and temporal improvements to ecosystems following reductions of acidifying emissions that produce `acid rain'. Logistic regression models were developed for the occurrence of fish and two fish-eatingbirds, common loons (Gavia immer) and common mergansers(Mergus merganser), using monitoring data collected onlakes across Ontario. These models were applied in the Algomaregion, including the Turkey Lakes Watershed (TLW). Using theWaterfowl Acidification Response Modeling System (WARMS), severalSO₂ emission reduction scenarios were simulated, i.e. thosecontributing to measured 1982–1986 sulphate deposition levels, 1994levels (corresponding to full implementation of Canadian SO₂emission reductions as stipulated in the 1991 Canada/U.S. AirQuality Agreement), 2010 levels (1994 plus full U.S. reductions),and both a 50% and a 75% further reduction beyond 2010 levels. Some habitat improvements in Algoma were predicted under the 2010scenario for all biota, but substantial increases in habitatquality, especially for mergansers, would occur only under further reductions. The TLW showed little change in chemistry orbiota, while lakes near the Montreal River were predicted toimprove substantially.     

AN INTEGRATIVE APPROACH TOWARDS UNDERSTANDING ECOLOGICAL RESPONSES TO DAM REMOVAL: THE MANATAWNY CREEK STUDY1

ABSTRACT: Dam removal has been proposed as an effective method of river restoration, but few integrative studies have examined ecological responses to the removal of dams. In 1999, we initiated an interdisciplinary study to determine ecological responses to the removal of a 2 m high dam on lower Manatawny Creek in southeastern Pennsylvania. We used an integrative monitoring program to assess the physical, chemical, and biological responses to dam removal. Following removal in 2000, increased sediment transport has led to major changes in channel form in the former impoundment and downstream reaches. Water quality did not change markedly following removal, probably because of the impoundment's short hydraulic residence time (less than two hours at base flow) and infrequent temperature stratification. When the impoundment was converted to a free flowing reach, the composition of the benthic macroinvertebrate and fish assemblages in this portion of Manatawny Creek shifted dramatically from lentic to lotic taxa. Some fish species inhabiting the free flowing reach downstream from the dam were negatively affected by large scale sediment transport and habitat alteration following dam removal, but this appears to be a short term response. Based on our observations and experiences in this study, we provide a list of issues to evaluate when considering future dam removals.     

宁夏引黄灌区低洼盐碱荒地的开发利用方向研究

宁夏自治区引黄灌区有十几万ｈｍ２的低洼盐碱荒地资源,长期处于荒芜状态。本文试图通过对资源条件进行综合评价及对各种开发利用模式综合比较,提出目前最佳的利用方向是挖塘养鱼造台田,建立立体生态农业体系。这对于当地农村经济发展和西北地区渔业基地建设具有重大意义。     

运用模拟生态系统评价果尔在稻田使用的安全性

在自行设计的稻田－鱼塘模拟生态系统中，以鲤鱼幼鱼和沼虾成虾为试验生物，对果尔在稻田使用的生态影响进行了模拟评价。结果表明，果尔在环境中消解很快，若按规定剂量在稻田使用，不会对邻近水域的鱼虾类生物产生危害，对稻田养鱼也是安全的。     

东大湖养鱼场水质遗传毒理的检测研究

本文报道了利用蚕豆根尖微核技术和鱼周血有核红细胞微核技术检测东大潮5个渔场的水质污染情况。结果为：各渔场蚕豆根尖MCN‰与对照（自来水）存在显著差异（F＞F(0．01)，P＜0．01），根据污染指数划分：A、B两渔场为重污染，C、D为中度污染，E为轻污染。各渔场鱼周血有核红细胞MCN‰与无明显污染源水体（柏录）存在着显著性差异（F＞F(0．01)，P＜0．01）。两种方法检测结果呈一致性，污染程度为A≈B＞C≈D＞E。微核率变化主要受污染源性质及位置的影响。将两种遗传毒性检测方法与化学方法检测相配合．能全面、准确、快速地监测水体污染状况，具有广泛的应用前景。     

水体中PCDD/Fs生物标示器的研究进展

水生生物体内PCDDs/Fs的累积作用是通过3种途径实现的,包括通过鳃和表皮从水中的直接摄入(生物富集),水中悬浮颗粒的摄取(吞入)和污染食物的消耗(生物放大)。鱼体内的PCDDs/Fs含量可以在一定程度上反映水体的PCDDs/Fs污染水平。但是,由于鱼体的生物-沉积物累积因子相当低,其作为生物累积标示的可能性仍有待进一步的研究。鱼体肝脏的总细胞色素P450、细胞色素P4501A、乙氧基试卤灵-O-脱乙基酶、超氧化物歧化酶和脂过氧化反应水平等指标都可作为水体PCDDs/Fs污染的较为敏感的生化生物标示器     

鱼体中单甲脒农药的测定

本文介绍了单甲脒农药在鱼体中残留量的测定方法.鱼样经石油醚提取,液-液分配后用高效液相色谱法测定.方法对单甲脒的最低检出浓度为0.05mg·kg~(-1),最低检出限为3×10~(-7)g,平均添加回收率为96.38±3.56%.