Assessing Calibration Uncertainty and Automation for Estimating Evapotranspiration from Agricultural Areas Using METRIC

Agricultural irrigation accounts for a large fraction of the total water use in the western United States. The Mapping Evapotranspiration at high Resolution with Internalized Calibration (METRIC) remote sensing energy balance model is being used to estimate historical agricultural water use in western Nevada to evaluate basin‐wide water budgets. Each METRIC evapotranspiration (ET) estimate must be calibrated by a trained user, which requires some iterative time investment and results in variation in ET estimates between users. An automated calibration algorithm for the METRIC model was designed to generate ET estimates comparable to those from trained users by mimicking the manual calibration process. Automated calibration allows for rapid generation of METRIC ET estimates with minimal manual intervention, as well as uncertainty and sensitivity analysis of the model. The variation in ET estimates generated by the automated calibration algorithm was found to be similar to the variation in manual ET estimates. Results indicate that uncertainty was highest for fields with low ET levels and lowest for fields with high ET levels, with a seasonal mean uncertainty of approximately 5% for all fields. In addition, in a blind comparison, automated daily and seasonal ET estimates compared well with flux tower measurement ET data at multiple sites. Automated methods can generate first‐order ET estimates that are similar to time intensive manual efforts with less time investment.     

Road Traffic Pollution Monitoring and Modelling Tools and the UK National Air Quality Strategy

This paper provides an assessment of the tools required to fulfil the air quality management role now expected of local authorities within the UK. The use of a range of pollution monitoring tools in assessing air quality is discussed and illustrated with evidence from a number of previous studies of urban background and roadside pollution monitoring in Leicester. A number of approaches to pollution modelling currently available for deployment are examined. Subsequently, the modelling and monitoring tools are assessed against the requirements of local authorities establishing air quality management areas. Whilst the paper examines UK-based policy, the study is of wider international interest.     

The case for nuclear electric power

Summary What role should the United States play in the energy economy of the world? Do we want to be uninvolved? Do we sit back and let the other industrial countries supply the rest of the world with nuclear power? Already, the world with four billion people and too high a growth rate is headed for trouble that could engulf us all. Four of five decades from now, when the population will have doubled to eight billion, the low sophistication level of today's energy users will very likely have run the total energy use very high. We in the United States will not only have our own energy problems; there will be an imperative need for a world energy policy, and we should be part of the negotiation. The United States will have to be more than self-sufficient. Power from uranium and thorium will expectably be our backbone. both at home and abroad. Among other things, Americans cannot afford to have profligate worldwide use of fossil fuel, with the expected movement of good crop weather northward, away from the best food-producing areas. American agriculture might be hit the hardest. Problems like these are world problems, and they just won't go away. We are part of them. Is it not to our own interest to have our own energy situation under control, so we can help shape the global outcome? This article is reprinted (excerpted) with the permission of Education Development Center, Inc., from “The Case for Nuclear Electric Power”, Occasional Paper No. 1 by Saville R. Davis and Jerrold R. Zacharias of the Energy in Perspective Project, funded by the Business Roundtable, the John D. and Catherine T. MacArthur Foundation, and Massachusetts Institute of Technology, For Biographic sketches of the Authors please see pages 305–306.     

Control strategies for particulate emissions from vehicular diesel exhaust

The advantages and disadvantages of several possible control strategies for particulate emissions from vehicular diesel exhaust are discussed. The evaluation of the potential usefulness of the various control strategies is based on available data concerning the mass loading and particle size distribution and on anticipated control standards. Several studies have been made on devices for removing particulate emissions from vehicular diesel exhaust. These studies, which include the techniques of filtration, wet scrubbers, and electrostatic precipitation, are summarized. A comparison of the various control devices is made based on such factors as size, efficiency, and maintenance requirements.     

Statistical Evaluation of Variables Affecting Occurrence of Hydrocarbons in Aquifers Used for Public Supply,California

The variables affecting the occurrence of hydrocarbons in aquifers used for public supply in California were assessed based on statistical evaluation of three large statewide datasets; gasoline oxygenates also were analyzed for comparison with hydrocarbons. Benzene is the most frequently detected (1.7%) compound among 17 hydrocarbons analyzed at generally low concentrations (median detected concentration 0.024 μg/l) in groundwater used for public supply in California; methyl tert‐butyl ether (MTBE) is the most frequently detected (5.8%) compound among seven oxygenates analyzed (median detected concentration 0.1 μg/l). At aquifer depths used for public supply, hydrocarbons and MTBE rarely co‐occur and are generally related to different variables; in shallower groundwater, co‐occurrence is more frequent and there are similar relations to the density or proximity of potential sources. Benzene concentrations are most strongly correlated with reducing conditions, regardless of groundwater age and depth. Multiple lines of evidence indicate that benzene and other hydrocarbons detected in old, deep, and/or brackish groundwater result from geogenic sources of oil and gas. However, in recently recharged (since ~1950), generally shallower groundwater, higher concentrations and detection frequencies of benzene and hydrocarbons were associated with a greater proportion of commercial land use surrounding the well, likely reflecting effects of anthropogenic sources, particularly in combination with reducing conditions.     

联合基于野外的代谢组学和化学分析手段筛选优先关注新兴污染物：在五大湖流域的案例研究

由于毒性评估项目很难与日渐增长的需要测试的污染物保持同步,所以较难将关注点集中在影响水生生态系统的最为生物相关的污染物上。由于评估潜在毒性污染物所造成的生物影响已被证明是有效的,内生性代谢物的研究（代谢组学）对于剔除那些较低可能造成生物影响的污染物或许有一定帮助,从而找出生物重要性最高的污染物。本研究在北美五大湖流域的18个地点针对置于笼中的黑头软口鲦（Pimephales promelas）进行实验。我们测定了水体温度和水样中的污染物浓度（目标污染物132种,检出86种）,并使用1H-NMR谱测量了肝极性提取物中的内生性代谢物。利用偏最小二乘法回归来比对内生性代谢物的相对丰度与污染物浓度和环境温度。结果表明内生性极性代谢物的指标与最多49种污染物存在共同变化。因此我们认为至多52%的检出污染物与内生性代谢物变化的共同变化不显著,表明这些污染物很可能不会在这些地点造成可以检测到的影响。这是通过缩短对于实验地点有着潜在影响的污染物列表从而扫描出检出污染物生物相关性的第一步。类似的信息有助于风险评估者区分不同污染物的重要性并将重点毒性测试放在最为生物相关的污染物上。
精选自Nicol Janecko, Lucie Pokludova, Jana Blahova, Zdenka Svobodova, Ivan Literak. Linking field-based metabolomics and chemical analyses to prioritize contaminants of emerging concern in the Great Lakes basin. Environmental Toxicology and Chemistry: Volume 35, Issue 10, pages 2493–2502, October 2016. DOI: 10.1002/etc.3409
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.3409/full
     

Uptake and transformation of perchlorate by vascular plants

Phytoremediation is a promising new method that uses green plants to cleanse soil and water contaminated with organic or inorganic pollutants. In this study, the uptake and transformation of sodium perchlorate (NaClO₄) using four vascular plant species were examined in batch experiments. The species include two trees, cabbage gum (Eucalyptus amplifolia) and eastern cottonwood (Populus deltoides), a herbaceous wetland plant, perennial glasswort (Salicornia virginica), and a herbaceous aquatic plant, waterweed (Elodea canadensis). Perchlorate was depleted from solution in the presence of all but one species (waterweed). Depletion was calculated as a first‐order kinetics reaction with k values in the range of 0–0.013 per day and accumulation of perchlorate was between 3.2 and 3138 mg/kg. Perchlorate and transformation metabolites (chlorate, chlorite, chloride) were observed in all plant tissues (e.g., roots, stems, leaves) analyzed. Results suggest that significant influences on perchlorate uptake include: (1) plant species present, (2) concentration of perchlorate, (3) sand versus hydroponic treatments, (4) the presence or absence of plant nutrients or competing ions, (5) stage of plant maturity.