Generation of internal waves by sheared turbulence: experiments

A series of experiments is presented that model the generation of internal gravity waves in the ocean by the forcing of turbulent eddies in the surface mixed layer.The experimental setup consists of a shallow mixed upper layer and a deep continuously stratified lower layer. A source of turbulence is dragged through the upper layer. Internal waves can freely propagate in the lower layer. The internal waves are measured using synthetic schlieren to determine the frequencies of the generated waves. Consistent with other studies, it is found that the characteristic frequencies of internal waves generated by turbulence are an approximate constant fraction of the buoyancy frequency.     

不同种类有机肥施用对稻田CH4和N2O排放的综合影响

以麦茬稻田为对象,研究基肥施用不同有机肥对稻田CH4和N2O排放的综合影响.结果表明:有机肥施用对稻田CH4和N2O排放的季节变化模式无明显影响,但影响其排放量.与施用化肥(化肥处理)相比,施用菜饼+化肥(菜饼处理)促进CH4和N2O的排放,其季节排放总量分别增加了252%和22%;施用小麦秸秆+化肥(秸秆处理)和牛厩肥+化肥(牛厩肥处理)明显增加CH4排放,增加量分别为250%和45%,同时却减少N2O排放,分别减少18%和21%;施用猪厩肥+化肥(猪厩肥处理)降低CH4和N2O的排放,分别降低4%和18%.对CH4和N2O排放的综合温室效应分析表明,菜饼和秸秆处理的全球增温潜势(GWP)约为化肥处理的2.5倍,牛厩肥和化肥处理基本持平,但施用猪厩肥可减少10%～15%.各处理的GWP从高到低依次为菜饼、秸秆、牛厩肥、化肥和猪厩肥.单位产量的GWP以秸秆处理最高,菜饼次之,牛厩肥比化肥处理略高,猪厩肥处理最低.从本生长季来看,猪厩肥的施用对于实现环境效益与生产效益的协调发展具有一定作用.     

INTERSTATE AND INTERNATIONAL AQUIFERS1

Many important groundwater aquifers cross state and national boundaries. The flow of water in these aquifers is not influenced by the boundaries but may be materially influenced by mans activities on one or both sides of a boundary. Interstate and international problems may develop because of excessive groundwater lowering on one side of a boundary affecting water users on the opposite side of the line. Similarly, intensive groundwater development along a surface stream may influence the amount of surface water that flows across a boundary. A third type of problem may develop when pumping on one side of the boundary induces poor quality water into an aquifer on the other side of the boundary. Several specific interstate and international aquifer problems are briefly described.     

A multi-process phytoremediation system for removal of polycyclic aromatic hydrocarbons from contaminated soils

To improve phytoremediation processes, multiple techniques that comprise different aspects of contaminant removal from soils have been combined. Using creosote as a test contaminant, a multi-process phytoremediation system composed of physical (volatilization), photochemical (photooxidation) and microbial remediation, and phytoremediation (plant-assisted remediation) processes was developed. The techniques applied to realize these processes were land-farming (aeration and light exposure), introduction of contaminant degrading bacteria, plant growth promoting rhizobacteria (PGPR), and plant growth of contaminant-tolerant tall fescue (Festuca arundinacea). Over a 4-month period, the average efficiency of removal of 16 priority PAHs by the multi-process remediation system was twice that of land-farming, 50% more than bioremediation alone, and 45% more than phytoremediation by itself. Importantly, the multi-process system was capable of removing most of the highly hydrophobic, soil-bound PAHs from soil. The key elements for successful phytoremediation were the use of plant species that have the ability to proliferate in the presence of high levels of contaminants and strains of PGPR that increase plant tolerance to contaminants and accelerate plant growth in heavily contaminated soils. The synergistic use of these approaches resulted in rapid and massive biomass accumulation of plant tissue in contaminated soil, putatively providing more active metabolic processes, leading to more rapid and more complete removal of PAHs.     

氮肥水平对不同土壤CH4排放的影响

鉴于氮肥施用对农田CH₄排放的影响还有很大不确定性,室外盆栽试验于2002年在南京农业大学实施.选取3个供试土壤,各土壤设置对照和低、中、高3个不同氮肥水平,施入尿素量分别为0 g/盆钵(对照) ,0.64g/盆钵,(低氮水平) ,1.28g/盆钵(中氮水平) ,1.93g/盆钵(高氮水平) .结果表明在水稻生长季,不同氮肥(尿素)施用量对稻田土壤CH₄排放影响表现为不同土壤之间,及不同氮肥水平之间CH₄排放均存在显著差异.无氮肥施入的情况下,3种土壤的CH₄季节性累积排放量存在显著差异,分别为6.7g/m²,12.6g/m² 和8.3g/m².施加氮肥后,3种土壤的CH4排放量随氮肥施入量的增加,均表现为降低趋势,不同土壤CH₄排放量存在差异,土壤背景氮含量最高的F(江苏溧水)土壤的CH4排放都比相应氮肥水平下的G(江苏涟水)和H(江苏农科院)土壤的CH₄排放低1倍左右.更进一步发现从低氮到中氮水平,3种土壤CH₄排放量随氮肥用量的增加降低幅度最大,而此时各土壤的NH₄-N含量随氮肥用量增加明显提高,推断造成CH₄排放降低的主要可能原因是各土壤的氨态氮含量的增加所致.从中氮到高氮水平3种土壤的CH₄排放量的变化不尽相同,G和H土壤的CH₄排放量随氮肥用量的增加而降低,而F土壤在中氮和高氮水平下的CH4排放量没有明显变化,值分别为30g/m².     

Assessing Landscape Condition Relative to Water Resources in the Western United States: A Strategic Approach

The Environmental Monitoring and Assessment Program (EMAP) is proposing an ambitious agenda to assess the status of streams and estuaries in a 12-State area of the western United States by the end of 2003. Additionally, EMAP is proposing to access landscape conditions as they relate to stream and estuary conditions across the west. The goal of this landscape project is to develop a landscape model that can be used to identify the relative risks of streams and estuaries to potential declines due to watershed-scale, landscape conditions across the west. To do so, requires an understanding of quantitative relationships between landscape composition and pattern metrics and parameters of stream and estuary conditions. This paper describes a strategic approach for evaluating the degree to which landscape composition and pattern influence stream and estuary condition, and the development and implementation of a spatially-distributed, landscape analysis approach.     

Compassionate versus consequentialist conservation

Ethical treatment of wildlife and consideration of animal welfare have become important themes in conservation, but ethical perspectives on how best to protect wild animals and promote their welfare are diverse. There are advantages to the consequentialist harms ethical framework applied in managing wild herbivores for conservation purposes. To minimize harms while achieving conservation goals, we argue that overabundant wild herbivores should in many cases be managed through consumptive in situ killing. Advantages of this policy are that the negative welfare states imposed on animals last only a short time; remaining animals are not deprived of positive welfare states (e.g., linked to rearing offspring); poor welfare states of animals in overabundant populations are avoided (e.g., starvation); negative welfare impacts on heterospecifics through resource depletion (i.e., competition) are prevented; harvesting meat reduces the number of (agricultural) animals raised to supply meat; and minimal costs maximize funding for other wildlife management and conservation priorities. Alternative ethical approaches to our consequentialist framework include deontology (containing animal rights) and virtue ethics, some of which underpin compassionate conservation. These alternative ethical approaches emphasize the importance of avoiding intentional killing of animals but, if no population reduction occurs, are likely to impose considerable unintentional harms on overabundant wildlife and indirectly harm heterospecifics through ineffective population reduction. If nonlethal control is used, it is likely that overabundant animals would be deprived of positive welfare states and economic costs would be prohibitive. We encourage conservation stakeholders to consider animal-welfare consequentialism as an ethical approach to minimize harms to the animals under their care as well as other animals that policies may affect while at the same time pursuing conservation goals.     

Monitoring the fate of chlorine from MSW sampling through combustion Part II: Combustion studies

Combustion measurements were carried out in a multi-kilogram capacity flow calorimeter on cellulose and cellulose/sand samples in 100% oxygen and several oxygen/nitrogen mixtures. Some measurements were made on cellulose/sand samples, which had 1 mass % of polyvinylchloride (PVC) as part of their composition, to study the conditions related to the formation/destruction of chlorinated organic compounds as combustion products. Qualitative identifications of a significant variety of chlorinated organic compounds have been made.