海水入侵污水放流系统及其清除研究

研究海水入侵污水放流系统及其清除特性有助于系统优化设计和运行保护。运用水力学一般原理推导了清除流量和入侵临界流量的估算公式,并根据数学模型模拟结果讨论了部分系统参数对清除和入侵的影响,指出系统沿程阻力的增加及扩散器主管截面逐渐减小对减小清除流量作用不大,而立管在主管底部与主管联结与在顶部联结相比一般可减小清除流量10％以上。系统清除流量和人侵临界流量与立管个数成正比。还介绍了鸭嘴阀,文丘里喉管等几种限制入侵和帮助清除的技术措施。介绍的方法与结果可供工程实际应用。     

Behavioral Traits and Airport Type Affect Mammal Incidents with U.S. Civil Aircraft

Wildlife incidents with aircraft cost the United States (U.S.) civil aviation industry >US$1.4 billion in estimated damages and loss of revenue from 1990 to 2009. Although terrestrial mammals represented only 2.3 % of wildlife incidents, damage to aircraft occurred in 59 % of mammal incidents. We examined mammal incidents (excluding bats) at all airports in the Federal Aviation Administration (FAA) National Wildlife Strike Database from 1990 to 2010 to characterize these incidents by airport type: Part-139 certified (certificated) and general aviation (GA). We also calculated relative hazard scores for species most frequently involved in incidents. We found certificated airports had more than twice as many incidents as GA airports. Incidents were most frequent in October (n = 215 of 1,764 total) at certificated airports and November (n = 111 of 741 total) at GA airports. Most (63.2 %) incidents at all airports (n = 1,523) occurred at night but the greatest incident rate occurred at dusk (177.3 incidents/hr). More incidents with damage (n = 1,594) occurred at GA airports (38.6 %) than certificated airports (19.0 %). Artiodactyla (even-toed ungulates) incidents incurred greatest (92.4 %) damage costs (n = 326; US$51.8 million) overall and mule deer (Odocoileus hemionus) was the most hazardous species. Overall, relative hazard score increased with increasing log body mass. Frequency of incidents was influenced by species relative seasonal abundance and behavior. We recommend airport wildlife officials evaluate the risks mammal species pose to aircraft based on the hazard information we provide and consider prioritizing management strategies that emphasize reducing their occurrence on airport property.     

Ripping Improves Tree Survival and Growth on Unused Reclaimed Mined Lands

There is renewed interest in re-establishing trees on 0.6 million ha of mining-disturbed lands in the Appalachian mountains of Eastern United States. Many coal-mined lands reclaimed to meet requirements of US federal law have thick herbaceous vegetation and compacted soils which impede tree establishment. Mitigation practices were applied on three mine sites and evaluated for success in enabling planted trees to become established. Eastern white pine (Pinus strobus), hybrid poplar (Populus deltoids × Populus trichocarpa), and mixed Appalachian hardwoods were established using weed control only and weed control with subsoil ripping. Trees were measured in October of 2008 after 5 years of growth. Subsoil ripping increased mixed hardwood survival from 43 to 71 %, hybrid poplar biomass index from 1.51 to 8.97 Mg ha^?1, and Eastern white pine biomass index from 0.10 to 0.32 Mg ha^?1. When restoring trees to unused mined sites, subsoil ripping can aid survival and growth to an extent that will result in a valuable forest.     

Assessment of public exposure to naturally occurring radioactive materials from mining and mineral processing activities of Tarkwa Goldmine in Ghana

Studies have been carried out in a Goldmine in Ghana to determine the exposure of the public to naturally occurring radioactive materials from processing of gold ore. Direct gamma spectrometry and neutron activation analysis techniques were used to analyse soil, rock, water and dust samples from the mining environment. The mean activity concentrations measured for (238)U, (232)Th and (40)K in the soil/rock samples were 15.2, 26.9 and 157.1 Bq kg(?-?1), respectively. For the water samples, the mean activity concentrations were 0.54 and 0.41 Bq l(?-?1)) and 7.76 Bq l(?-?1) for (226)Ra, (232)Th and (40)K, respectively. The mean activity concentrations measured in the dust samples were 4.90 and 2.75 μBq m(?-?3) for (238)U and (232)Th, respectively. The total annual effective dose to the public was estimated to be 0.69 mSv. The results in this study compared well with typical world average values. The results indicate an insignificant exposure of the public from the activities of the Goldmine.     

Assessing possible visitor-use impacts on water quality in Yosemite National Park, California

There is concern that visitor-use associated activities, such as bathing, dish washing, wastewater production, and stock animal use near lakes and streams, could cause degradation of water quality in Yosemite National Park. A study was conducted during 2004-2007 to assess patterns in nutrient and Escherichia coli (E. coli) concentrations in the Merced and Tuolumne Rivers and characterize natural background concentrations of nutrients in the park. Results indicated that nutrient and E. coli concentrations were low, even compared to other undeveloped sites in the United States. A multiple linear regression approach was used to model natural background concentrations of nutrients, with basin characteristics as explanatory variables. Modeled nitrogen concentrations increased with elevation, and modeled phosphorus concentrations increased with basin size. Observed concentrations (±uncertainty) were compared to modeled concentrations (±uncertainty) to identify sites that might be impacted by point sources of nutrients, as indicated by large model residuals. Statistically significant differences in observed and modeled concentrations were observed at only a few locations, indicating that most sites were representative of natural background conditions. The empirical modeling approach used in this study can be used to estimate natural background conditions at any point along a study reach in areas minimally impacted by development, and may be useful for setting water-quality standards in many national parks.     

Hydrologic disturbance reduces biological integrity in urban streams

The impact of urbanization on stream ecosystems is linked by land cover changes to the alteration of the natural hydrology and subsequent physical disruption of stream biota and habitat. Seasonal floods are part of the natural disturbance regime of many streams, but urbanization increases their frequency and magnitude. This study evaluated the impact of hydrologic disturbance on fish and aquatic macroinvertebrates in 81 (56 urban/25 reference) Ohio streams. Hydrologic variables included annual and monthly 24-h rainfall maxima and computed annual peak discharge, with computation supported by GIS-based drainage area delineation and land cover characterization. Ohio biological criteria for fish and macroinvertebrates measured during the late spring and summer were negatively impacted by annual peak discharge in urban streams as compared to reference streams. Results support the application of stormwater best management practices as part of stream restoration efforts to mitigate urbanization impacts to fish and macroinvertebrates.     

Reduction of Baltic Sea Nutrient Inputs and Allocation of Abatement Costs Within the Baltic Sea Catchment

The Baltic Sea Action Plan (BSAP) requires tools to simulate effects and costs of various nutrient abatement strategies. Hierarchically connected databases and models of the entire catchment have been created to allow decision makers to view scenarios via the decision support system NEST. Increased intensity in agriculture in transient countries would result in increased nutrient loads to the Baltic Sea, particularly from Poland, the Baltic States, and Russia. Nutrient retentions are high, which means that the nutrient reduction goals of 135 000 tons N and 15 000 tons P, as formulated in the BSAP from 2007, correspond to a reduction in nutrient loadings to watersheds by 675 000 tons N and 158 000 tons P. A cost-minimization model was used to allocate nutrient reductions to measures and countries where the costs for reducing loads are low. The minimum annual cost to meet BSAP basin targets is estimated to 4.7 billion €.     

Flow-injection analysis with fluorescence detection for the determination of trace levels of ammonium in seawater

A method using flow-injection, gas-diffusion, derivatisation and then fluorescent detection has been established for ammonium ion determination in seawater. The fluorescent derivative formed by reacting ortho-phthaldialdehyde (OPA) and sulfite with ammonia gives high sensitivity while removing potential interferences. This is required to measure the low concentrations of ammonium often seen in the open ocean. The experimental conditions (flow-rate, reagent concentrations, membrane configurations, etc.) were manipulated to improve performance. For a sample throughput of 30 samples h(-1), the limit of detection was 7 nM, the coefficient of variation was 5.7% at 800 nM, and the calibration curve was linear to at least 4 micromol L(-1). Interferences were minimised by a gaseous diffusion step. Volatile small molecular-weight amines as interferents were discriminated against by this method. They neither passed through the membrane as efficiently as ammonia, nor reacted as readily with OPA when sulfite was the reductant. Contamination by ammonia from laboratory and shipboard sources complicates application of the method to natural waters, especially measurement of low concentrations (<100 nM) in open-ocean waters. Steps to overcome contamination are described in detail. Some results are presented for ammonium determination in Southern Ocean and Huon Estuary (Tasmania) waters.     

Application of a checklist for quality assistance in environmental modelling to an energy model

Large, complex energy models present considerable challenges to develop and test. Uncertainty assessments of such models provide only partial guidance on the quality of the results. We have developed a model quality assistance checklist to aid in this purpose. The model checklist provides diagnostic output in the form of a set of pitfalls for the model application. The checklist is applied here to an energy model for the problem of assessing energy use and greenhouse gas emissions. Use of the checklist suggests that results on this issue are contingent on a number of assumptions that are highly value-laden. When these assumptions are held fixed, the model is deemed capable of producing moderately robust results of relevance to climate policy over the longer term. Checklist responses also indicate that a number of details critical to policy choices or outcomes on this issue are not captured in the model, and model results should therefore be supplemented with alternative analyses.     

An exploratory study of air emissions associated with shale gas development and production in the Barnett Shale

Information regarding air emissions from shale gas extraction and production is critically important given production is occurring in highly urbanized areas across the United States. Objectives of this exploratory study were to collect ambient air samples in residential areas within 61 m (200 feet) of shale gas extraction/production and determine whether a “fingerprint” of chemicals can be associated with shale gas activity. Statistical analyses correlating fingerprint chemicals with methane, equipment, and processes of extraction/production were performed. Ambient air sampling in residential areas of shale gas extraction and production was conducted at six counties in the Dallas/Fort Worth (DFW) Metroplex from 2008 to 2010. The 39 locations tested were identified by clients that requested monitoring. Seven sites were sampled on 2 days (typically months later in another season), and two sites were sampled on 3 days, resulting in 50 sets of monitoring data. Twenty-four-hour passive samples were collected using summa canisters. Gas chromatography/mass spectrometer analysis was used to identify organic compounds present. Methane was present in concentrations above laboratory detection limits in 49 out of 50 sampling data sets. Most of the areas investigated had atmospheric methane concentrations considerably higher than reported urban background concentrations (1.8–2.0 ppm_v). Other chemical constituents were found to be correlated with presence of methane. A principal components analysis (PCA) identified multivariate patterns of concentrations that potentially constitute signatures of emissions from different phases of operation at natural gas sites. The first factor identified through the PCA proved most informative. Extreme negative values were strongly and statistically associated with the presence of compressors at sample sites. The seven chemicals strongly associated with this factor (o-xylene, ethylbenzene, 1,2,4-trimethylbenzene, m- and p-xylene, 1,3,5-trimethylbenzene, toluene, and benzene) thus constitute a potential fingerprint of emissions associated with compression.

Implications: Information regarding air emissions from shale gas development and production is critically important given production is now occurring in highly urbanized areas across the United States. Methane, the primary shale gas constituent, contributes substantially to climate change; other natural gas constituents are known to have adverse health effects. This study goes beyond previous Barnett Shale field studies by encompassing a wider variety of production equipment (wells, tanks, compressors, and separators) and a wider geographical region. The principal components analysis, unique to this study, provides valuable information regarding the ability to anticipate associated shale gas chemical constituents.