黄浦江上游蔬菜田氮素流失规律测坑研究

通过测坑试验,研究了黄浦江上游蔬菜田渗漏水中氮素的变化动态和流失规律。结果表明,蔬菜田渗漏水中氮素以NO3^--N为主,NO3^--N作为氮素在土壤中流失的主要形态将成为施用氮肥造成地下水污染的重要来源;施用精制有机肥或粗猪粪代替部分化学氮肥有利于减少蔬菜田渗漏水中氮素的流失。     

Restoring coastal wetlands that were ditched for mosquito control: A preliminary assessment of hydro-leveling as a restoration technique

The wetlands surrounding Tampa Bay, Florida were extensively ditched for mosquito control in the 1950s. Spoil from ditch construction was placed adjacent to the wetlands ditches creating mound-like features (spoil-mounds). These mounds represent a loss of 14% of the wetland area in Tampa Bay. Spoil mounds interfere with tidal flow and are locations for non-native plants to colonize (e.g., Schinus terebinthifolius). Removal of the spoil mounds to eliminate exotic plants, restore native vegetation, and re-establish natural hydrology is a restoration priority for environmental managers. Hydro-leveling, a new technique, was tested in a mangrove forest restoration project in 2004. Hydro-leveling uses a high pressure stream of water to wash sediment from the spoil mound into the adjacent wetland and ditch. To assess the effectiveness of this technique, we conducted vegetation surveys in areas that were hydro-leveled and in non-hydro-leveled areas 3 years post-project. Adult Schinus were reduced but not eliminated from hydro-leveled mounds. Schinus seedlings however were absent from hydro-leveled sites. Colonization by native species was sparse. Mangrove seedlings were essentially absent (≈2 m⁻²) from the centers of hydro-leveled mounds and were in low density on their edges (17 m⁻²) in comparison to surrounding mangrove forests (105 m⁻²). Hydro-leveling resulted in mortality of mangroves adjacent to the mounds being leveled. This was probably caused by burial of pneumatophores during the hydro-leveling process. For hydro-leveling to be a useful and successful restoration technique several requirements must be met. Spoil mounds must be lowered to the level of the surrounding wetlands. Spoil must be distributed further into the adjacent wetland to prevent burial of nearby native vegetation. Finally, native species may need to be planted on hydro-leveled areas to speed up the re-vegetation process.     

环保处罚事件对“两高”上市公司股价的影响分析

手工搜集的2007—2017年49家"两高"上市公司的67个环保处罚样本,涉及化工、钢铁、煤炭开采等六个行业,采用事件研究法对环保处罚发布前后股票市场的反应进行了实证研究,并估算了每个环保处罚事件给企业带来的市值损失。研究发现,在环保处罚公示当日,股价大幅下跌,带来显著为负的异常收益率,最多的下跌了7.72%,并且这种影响可以持续到次日。从事件日后的第二天开始,这种负面影响不再显著,表现为平均异常收益率不再显著。但其造成的股价下跌是短时间内无法恢复的,因其累积平均异常收益率持续显著为负。在市值损失方面,67家上市公司平均损失了约2.85亿元市值,最多的损失了约48.5亿元,整个样本的总市值损失约为191亿元。     

改性聚羟基丁酸-戊酸共聚物在自然环境中的生物降解性能研究

研究了聚羟基丁酸-戊酸共聚物(PHBV)及其与聚丙烯酸丁酯(PBA)接枝改性物在自然环境中的微生物降解性能,比较了二者在不同土壤中的失重率、形貌变化和分子量变化.研究表明,在自然环境中PHBV由于微生物的作用而发生降解,导致其重量损失和分子量下降,其降解程度与外界环境中微生物的数量、种类及湿度等条件有关.PBA接枝PHBV后复合物的生物降解性能有所下降.      

20世纪末期我国农地退化的经济损失估值

土地退化是自然过程与社会经济活动共同作用的现象。本文在分析中国农地退化基本态势的基础上，运用货币估值技术，对农地退化的各种损失进行了定量或半定量估算。估算表明：在1999年，中国由于农地退化所造成的经济损失达3268．1亿元，占当年GNP的4．1％，与1992年相比，经济损失占GNP的比重上升了1．5个百分点。     

果园地面覆盖管理的生态经济效益分析

分析了果园地面覆盖管理的生态和经济效益，并对果园地面管理方式在果树产量、质量、营养、病虫害和土壤有机质、肥力、水分、侵蚀以及生态环境上的影响进行了赋分综合评价。评价的有利效应顺序是：有机物覆盖〉间作〉生草带状覆盖〉生草覆盖〉除草剂除草〉翻耕。据此，针对我国生态环境、人口、经济状况，提出了在山区的经济林果园内应推广应用秸杆地面覆盖技术，对于减少水土流失，提高果树产量具有显著的生态和经济效益。     

长江上游区的坡面土壤流失及侵蚀防治

长江上游区的嘉陵江流域、金沙江渡口至屏山河段流域、三峡库区及库周区,土壤坡面流失量都超过3000t/a·km~2,属长江上游流失严重之最,应列为首批治理重点区;三峡区长江主航道及近主航道支流两岸的重力侵蚀十分严重,给长江输入大量难以排除的砂石物质,应重点加强此区域的重力侵蚀防治。最后对此区的水土保持提出了6条意见。     

Regional Ontogeny of New England Salt Marsh Die‐Off

Coastal areas are among the world's most productive and highly affected ecosystems. Centuries of human activity on coastlines have led to overexploitation of marine predators, which in turn has led to cascading ecosystem‐level effects. Human effects and approaches to mediating them, however, differ regionally due to gradients in biotic and abiotic factors. Salt marsh die‐off on Cape Cod, Massachusetts (U.S.A.), triggered by a recreational‐fishing‐induced trophic cascade that has released herbivorous crabs from predator control, has been ongoing since 1976. Similar salt marsh die‐offs have been reported in Long Island Sound and Narragansett Bay (U.S.A.), but the driving mechanism of these die‐offs has not been examined. We used field experiments to assess trophic interactions and historical reconstructions of 24 New England marshes to test the hypotheses that recreational fishing and predator depletion are a regional trigger of salt marsh die‐off in New England and that die‐offs in Long Island Sound and Narragansett Bay are more recent than those on Cape Cod. Predator depletion was the general trigger of marsh die‐off and explained differences in herbivorous crab abundance and the severity of die‐off across regions. Die‐offs in Long Island Sound and Narragansett Bay are following a trajectory similar to die‐off on Cape Cod, but are approximately 20 years behind those on Cape Cod. As a result, die‐off currently affects 31.2% (SE 2.2) of low‐marsh areas in Long Island Sound and Narragansett Bay, less than half the severity of die‐off on Cape Cod. Our results contribute to the growing evidence that recreational fishing is an increasing threat to coastal ecosystems and that studying the effects of human activity at regional scales can provide insight into local effects and aid in early detection and potential remediation. Ontogenia Regional de un Incremento en la Mortandad en una Marisma Salada de Nueva Inglaterra     

LUMP SUM TAX LOSS REIMBURSEMENT UNDER THE THAMES RIVER FLOOD CONTROL COMPACT1

ABSTRACT: Under the terms of the Thames River Valley Flood Control Compact, Connecticut has been paying Massachusetts 40 percent of the annual property tax losses suffered by seven Massachusetts towns where four flood control structures were located. The permissable alternative of a single lump sum payment was investigated in the study summarized here. The lump sum payment should be the proportion of total benefits (flood control and recreation) from the four structures which Connecticut receives, multiplied by the present value of projected tax losses in the seven tom Flood control benefits and their distribution between the two states were fixed in the Compact, but a survey was necessary to determine recreational benefits and their distribution. Regression analysis of 1957 to 1978 tax loss data provided equations used to project future tax losses. Resent values of projected tax low were calculated using discount rates ranging from 6 to 12 percent. A plausible range of lump sum reinbursements as of 1979 was identified.     

Spatial and temporal changes in Louisiana's Barataria Basin marshes, 1945–1980

A computerized geographic information system with site-specific change-detection capabilities was developed to document amounts, rates, locations, and sequences of loss of coastal marsh to open water in Barataria Basin, Louisiana, USA. Land-water interpretations based on 1945, 1956, 1969, and 1980 aerial photographs were used as input, and a modified version of the Earth Resources Laboratory Applications Software developed by the National Aeronautics and Space Administration was used as a spatial data base management system. Analysis of these data sets indicates that rates of marsh loss have increased from 0.36% per year in the 1945–56 period, to 1.03% per year in 1956–69, and to 1.96% per year in 1969–80. The patterns of marsh loss indicate that the combination of processes causing degradation of the marsh surface does not affect all areas uniformly. Marsh loss rates have been highest where freshwater marshes have been subject to saltwater intrusion. The increase in the wetland loss rates corresponds to accelerated rates of subsidence and canal dredging and to a cumulative increase in the area of canals and spoil deposits.