Trace analysis for aromatic hydrocarbons in natural waters

A method for trace analysis of volatile aromatic hydrocarbons in natural water is described. The method is based on sparging water samples with nitrogen, adsorption of hydrocarbons on activated charcoal, followed by desorption into carbon disulfide and gas chromatographic analysis. The sensitivity of the method reaches into the 0.1 to 0.2 μg/L concentration range for individual aromatic hydrocarbons. The accuracy and reliability of the method was validated. The method was used in three field studies: dispersion of aromatic hydrocarbons discharged from the Trans-Alaska Pipeline southern terminal throughout Port Valdez; survey of the Atigun River Watershed after oil spill on June 10, 1979; and chemical characterization of treated effluents from offshore oil extraction platforms in the Gulf of Mexico.     

Information-theory approach to allometric growth of marine organisms

Allometric growth investigations are usually conducted by fitting the allometric model (L) (y, x are morphometric characters and b the allometric exponent), which is quite simple both conceptually and mathematically, and its parameters are easy to estimate by linear regression. However b is not necessarily constant and it may change either continuously or abruptly at specific breakpoints; thus, the simple L model quite often fails to describe allometric growth successfully. In the current context, a better alternative is proposed, based on Kullback–Leibler (K-L) information theory and multi-model inference (MMI). Allometric growth was investigated in eight marine species: the bivalves Pecten jacobaeus and Pinna nobilis, the squids Todarodes sagittatus and Todaropsis eblanae, the crab Pachygrapsus marmoratus (females), the ghost shrimp Pestarella tyrrhena (males), and the fishes Trachurus trachurus and Sparus aurata. In each of the eight species, a pair of body parts was measured and the allometric growth of one body part in relation to the other (reference dimension) was studied, by fitting five different candidate models including: the simple allometric model, two models assuming that b changed continuously and two other assuming that b had a breakpoint. For each species, the ‘best’ model was selected by minimizing the small-sample, bias-corrected form of the Akaike Information Criterion. To quantify the plausibility of each model, given the data and the set of five models, the ‘Akaike weight’ w _i of each model was calculated; based on w _i the average model was estimated for each case. MMI is beneficial, more robust, and may reveal more information than the classical approach. As demonstrated with the given examples, estimation of b from the linear model, when it was not supported by the data, revealed some characteristic pitfalls, such as concluding positive allometry when there is actually negative or vice versa, or reporting allometry when the data in reality support isometric growth or vice versa.     

新型循环流化床硝化-反硝化启动试验研究

利用新型循环流化床进行清水实验及硝化、反硝化启动试验研究,考察了系统对有机物和氮的去除效果,并分析了曝气量对系统启动的影响。结果表明,将输送床和传统流化床工艺进行有机结合,技术上可行,可以在系统内不同区建立缺氧、好氧条件,通过硝化和反硝化作用完成脱氮。     

Dissipation kinetics and effect of different decontamination techniques on the residues of emamectin benzoate and spinosad in cowpea pods

Dissipation and decontamination of the semisynthetic macrolide emamectin benzoate and the natural insecticide spinosad on cowpea pods were studied following field application at single and double doses of 11.0 and 22 and 73 and 146 g ai ha^?1, respectively. Residues of these naturalytes were estimated using LC-MS/MS. The initial deposit of 0.073 and 0.153 mg kg^?1 of emamectin benzoate dissipated below quantitation level on the fifth and seventh day at single and double dosage, respectively. For spinosad, the initial deposits of 0.94 and 1.90 mg kg^?1 reached below quantitation level on the 7th day and 15th day at single and double dosage, respectively. The half-life of emamectin benzoate and spinosad was 1.13–1.49 and 1.05–1.39 days with the calculated safe waiting period of 2.99–6.12 and 1.09–3.25 days, respectively, for single and double dosage. Processing of the harvestable pods with different decontamination techniques resulted in 33.82 to 100 % removal 2 h after the application of emamectin benzoate and 100 % removal 3 days after spraying, while the removal was 42.05 to 87.46 % 2 h after the application of spinosad and 38.05 to 68.08 % 3 days after application.     

基于多源数据的PM2.5浓度时空分布预测与制图

随着我国经济、工业化、城市化进程迅速发展,PM_(2.5)污染在中国已经成为一个极端的环境和社会问题,并引起广泛关注.采用新技术估算的地表PM_(2.5)质量浓度,收集并处理了遥感反演的气溶胶光学厚度(AOD),气象数据,其他地理数据和污染物排放数据,采用贝叶斯最大熵(BME)结合地理加权回归(GWR)来分析2015年冬季的PM_(2.5)暴露在我国东部大范围区域的时空变异特征.结果表明,BME模型的十折交叉验证结果的决定系数R~2为0.92,均方根误差(RMSE)为8.32μg·m~(-3),平均拟合误差(MPE)为-0.042μg·m~(-3),平均绝对拟合误差(MAE)为4.60μg·m~(-3),与地理加权回归模型的结果相比(R~2=0.71,RMSE=15.68μg·m~(-3),MPE=-0.095μg·m~(-3),MAE=11.14μg·m~(-3)),BME的预测结果有极大的提高.空间上,PM_(2.5)高浓度地区主要集中在华北、长江三角洲、四川盆地,低浓度地区主要集中在中国的最南部如珠江三角洲和云南的西南部;时间上,不同月份的研究区域PM_(2.5)空间分布所有差别,2015年的12月、2016年1月PM_(2.5)污染最为严重,2015年的11月,2016年的2月污染相对较低.     

Western Land Managers will Need all Available Tools for Adapting to Climate Change,Including Grazing: A Critique of Beschta et al.

In a previous article, Beschta et al. (Environ Manag 51(2):474–491, 2013) argue that grazing by large ungulates (both native and domestic) should be eliminated or greatly reduced on western public lands to reduce potential climate change impacts. The authors did not present a balanced synthesis of the scientific literature, and their publication is more of an opinion article. Their conclusions do not reflect the complexities associated with herbivore grazing. Because grazing is a complex ecological process, synthesis of the scientific literature can be a challenge. Legacy effects of uncontrolled grazing during the homestead era further complicate analysis of current grazing impacts. Interactions of climate change and grazing will depend on the specific situation. For example, increasing atmospheric CO₂ and temperatures may increase accumulation of fine fuels (primarily grasses) and thus increase wildfire risk. Prescribed grazing by livestock is one of the few management tools available for reducing fine fuel accumulation. While there are certainly points on the landscape where herbivore impacts can be identified, there are also vast grazed areas where impacts are minimal. Broad scale reduction of domestic and wild herbivores to help native plant communities cope with climate change will be unnecessary because over the past 20–50 years land managers have actively sought to bring populations of native and domestic herbivores in balance with the potential of vegetation and soils. To cope with a changing climate, land managers will need access to all available vegetation management tools, including grazing.     

Enhanced biological phosphorus removal using thermal alkaline hydrolyzed municipal wastewater biosolids

This study reports the feasibility of using municipal wastewater biosolids as an alternative carbon source for biological phosphorus removal. The biosolids were treated by a lowtemperature, thermal alkaline hydrolysis process patented by Lystek International Inc.(Cambridge, ON, Canada) to produce short-chain volatile fatty acids and other readily biodegradable organics. Two sequencing batch reactors(SBRs) were operated with synthetic volatile fatty acids(Syn VFA) and readily biodegradable organics produced from the alkaline hydrolysis of municipal wastewater biosolids(Lystek) as the carbon source, respectively.Municipal wastewaters with different strengths and COD:N:P ratios were tested in the study. The reactors' performances were compared with respect to nitrogen and phosphorus removal. It was observed that phosphorus removal efficiencies were between 98%–99% and 90%–97% and nitrogen removal efficiencies were 78%–81%, and 67% for the Syn VFA and Lystek, respectively. However, the kinetics for phosphorus release and uptake during the anaerobic and aerobic stages with Lystek were observed to be significantly lower than Syn VFA due to the presence of higher order VFAs(C4 and above) and other fermentable organics in the Lystek.     

Monitoring Fish Contaminant Responses to Abatement Actions: Factors that Affect Recovery

Monitoring of contaminant accumulation in fish has been conducted in East Fork Poplar Creek (EFPC) in Oak Ridge, Tennessee since 1985. Bioaccumulation trends are examined over a twenty year period coinciding with major pollution abatement actions by a Department of Energy facility at the stream’s headwaters. Although EFPC is enriched in many contaminants relative to other local streams, only polychlorinated biphenyls (PCBs) and mercury (Hg) were found to accumulate in the edible portions of fish to levels of human health concern. Mercury concentrations in redbreast sunfish were found to vary with season of collection, sex and size of individual fish. Over the course of the monitoring, waterborne Hg concentrations were reduced >80%; however, this did not translate into a comparable decrease in Hg bioaccumulation at most sites. Mercury bioaccumulation in fish did respond to decreased inputs in the industrialized headwater reach, but paradoxically increased in the lowermost reach of EFPC. As a result, the downstream pattern of Hg concentration in fish changed from one resembling dilution of a headwater point source in the 1980s to a uniform distribution in the 2000s. The reason for this remains unknown, but is hypothesized to involve changes in the chemical form and reactivity of waterborne Hg associated with the removal of residual chlorine and the addition of suspended particulates to the streamflow. PCB concentrations in fish varied greatly from year-to-year, but always exhibited a pronounced downstream decrease, and appeared to respond to management practices that limited episodic inputs from legacy sources within the facility.