离子色谱法测定PM_(2.5)中硫酸根离子含量不确定度评议

准确测定大气颗粒物中水溶性组份对分析污染物来源及身体健康具有重要意义。本文采用离子色谱法测定PM2.5中硫酸根离子含量,并对测定的不确定度进行分析。分析过程不确定度来源是样品重复性测量引入不确定度,样品测量准确性引入不确定度和标准曲线的不确定度。应用不确定度评定理论,计算硫酸根离子的合成不确定度。结果表明,滤膜中硫酸根离子本底浓度高低与剪裁滤膜环节是不确定度的主要来源。为了提高分析的准确性,建议使用本底低的滤膜,并取整张滤膜进行分析。     

Fungal biodegradation and removal of cyanobacteria and microcystins: potential applications and research needs

Environmental Science and Pollution Research - Harmful cyanobacterial blooms (HCB) have severe impacts on marine and freshwater systems worldwide. They cause oxygen depletion and produce potent...     

Incorporating Uncertainty Into the Ranking of SPARROW Model Nutrient Yields From Mississippi/Atchafalaya River Basin Watersheds1

Abstract: Excessive loads of nutrients transported by tributary rivers have been linked to hypoxia in the Gulf of Mexico. Management efforts to reduce the hypoxic zone in the Gulf of Mexico and improve the water quality of rivers and streams could benefit from targeting nutrient reductions toward watersheds with the highest nutrient yields delivered to sensitive downstream waters. One challenge is that most conventional watershed modeling approaches (e.g., mechanistic models) used in these management decisions do not consider uncertainties in the predictions of nutrient yields and their downstream delivery. The increasing use of parameter estimation procedures to statistically estimate model coefficients, however, allows uncertainties in these predictions to be reliably estimated. Here, we use a robust bootstrapping procedure applied to the results of a previous application of the hybrid statistical/mechanistic watershed model SPARROW (Spatially Referenced Regression On Watershed attributes) to develop a statistically reliable method for identifying “high priority” areas for management, based on a probabilistic ranking of delivered nutrient yields from watersheds throughout a basin. The method is designed to be used by managers to prioritize watersheds where additional stream monitoring and evaluations of nutrient‐reduction strategies could be undertaken. Our ranking procedure incorporates information on the confidence intervals of model predictions and the corresponding watershed rankings of the delivered nutrient yields. From this quantified uncertainty, we estimate the probability that individual watersheds are among a collection of watersheds that have the highest delivered nutrient yields. We illustrate the application of the procedure to 818 eight‐digit Hydrologic Unit Code watersheds in the Mississippi/Atchafalaya River basin by identifying 150 watersheds having the highest delivered nutrient yields to the Gulf of Mexico. Highest delivered yields were from watersheds in the Central Mississippi, Ohio, and Lower Mississippi River basins. With 90% confidence, only a few watersheds can be reliably placed into the highest 150 category; however, many more watersheds can be removed from consideration as not belonging to the highest 150 category. Results from this ranking procedure provide robust information on watershed nutrient yields that can benefit management efforts to reduce nutrient loadings to downstream coastal waters, such as the Gulf of Mexico, or to local receiving streams and reservoirs.     

Micropollutants in urban stormwater: occurrence,concentrations, and atmospheric contributions for a wide range of contaminants in three French catchments

This study aimed at: (a) providing information on the occurrence and concentration ranges in urban stormwater for a wide array of pollutants (n?=?77); (b) assessing whether despite the differences between various catchments (land use, climatic conditions, etc.), the trends in terms of contamination level are similar; and (c) analyzing the contribution of total atmospheric fallout (TAF) with respect to sources endogenous to this contamination. The studied contaminants include conventional stormwater contaminants (polycyclic aromatic hydrocarbons (PAHs), Zn, Cu, Pb, etc.), in addition to poorly or undocumented pollutants such as nonylphenol and octylphenol ethoxylates (NPnEO and OPnEO), bisphenol A (BPA), polybrominated diphenyl ethers (PBDEs), a wide variety of pesticides, and various metals of relevance (As, Ti, Sr, V). Sampling and analysis were performed using homogeneous methods on three urban catchments with different land use patterns located in three distinct French towns. For many of these pollutants, the results do not allow highlighting a significant difference in stormwater quality at the scale of the three urban catchments considered. Significant differences were, however, observed for several metals (As, Cr, Cu, Ni, Sr and Zn), PAHs, and PBDEs, though this assessment would need to be confirmed by further experiments. The pollutant distributions between dissolved and particulate phases were found to be similar across the three experimental sites, thus suggesting no site dependence. Lastly, the contributions of TAF to stormwater contamination for micropollutants were quite low. This finding held true not only for PAHs, as previously demonstrated in the literature, but also for a broader range of molecules such as BPA, NPnEO, OPnEO, and PBDEs, whose high local production is correlated with the leaching of urban surfaces, buildings, and vehicles.     

宝钢厂区植被碳储量及其固碳效益评价

以著名钢铁企业上海宝钢为例,基于厂区植被调查、航片数字化解释、优势种生物量测定及模型建立,对宝钢厂区植被碳储量和固碳能力进行估算,并通过碳税法对其固碳效益进行评价,以期为城市工业区绿地群落配置和绿化树种选择、企业绿化建设的费用效益分析提供更为科学的依据。结果表明:宝钢厂区植被总碳储量为3992.99～4736.17 t,固碳效益为13507.33～16185.85万元;平均碳密度为45.82～53.27 t/hm2,固碳能力为5.91～6.87t/(hm2.a),高于上海城市森林平均值,但小于中国森林平均值,一定程度上受平均胸径、郁闭度及群落密度等因素影响。厂区在进行绿化建设时,应考虑选择防污且固碳能力强的植物,构建防污固碳兼有型群落,发挥植被的多元功能。     

Small towns in the united states: a perspective

Small towns are an important part of the rural settlement fabric in the United States, but there is very little substantive research into their capacity to survive or their intrinsic importance. However, recently there has been increasing interest shown by social scientists in these problems. This paper looks at features of this research from the point of view of the population and economic structure of small towns. It concludes by arguing that the problems of small towns are not indigenous to the towns, and calls for a comprehensive national urban policy.     

Sorption of strontium on bentonite

Sorption of Sr on bentonite was studied using the batch technique. Distribution coefficients (K_d) were determined as a function of contact time, pH, sorbent and sorbate concentration and temperature. The data were interpreted in terms of Freundlich, Langmuir and Dubinin-Radushkevich isotherms. Thermodynamic parameters for the sorption system were determined at three different temperatures. The positive value of the heat of sorption, ΔH° = 30.62 kJ/mol at 298 K, shows that the sorption of strontium on bentonite is endothermic. The negative value of the free energy of sorption, ΔG° = −10.69 kJ/mol at 298 K, shows the spontaneity of the reaction. ΔG° becomes more negative with increasing temperature, which shows that the sorption process is more favorable at higher temperatures. The mean free energy for sorption, E 9 kJ/mol, suggests that ion exchange is the predominant mode of sorption in the Sr concentration range studied, i.e. 0.01 – 0.3 mol/dm³. The presence of complementary cations depresses the sorption of strontium on bentonite in the order Ca²⁺>Mg²⁺>K⁺>Na⁺. Some organic complexing agents and natural ligands also affect the sorption of strontium. The desorption studies with ground water at low strontium loadings on bentonite show that about 90% of Sr is irreversibly sorbed on the bentonite.     

Linking ground-water age and chemistry data along flow paths: implications for trends and transformations of nitrate and pesticides

Tracer-based ground-water ages, along with the concentrations of pesticides, nitrogen species, and other redox-active constituents, were used to evaluate the trends and transformations of agricultural chemicals along flow paths in diverse hydrogeologic settings. A range of conditions affecting the transformation of nitrate and pesticides (e.g., thickness of unsaturated zone, redox conditions) was examined at study sites in Georgia, North Carolina, Wisconsin, and California. Deethylatrazine (DEA), a transformation product of atrazine, was typically present at concentrations higher than those of atrazine at study sites with thick unsaturated zones but not at sites with thin unsaturated zones. Furthermore, the fraction of atrazine plus DEA that was present as DEA did not increase as a function of ground-water age. These findings suggest that atrazine degradation occurs primarily in the unsaturated zone with little or no degradation in the saturated zone. Similar observations were also made for metolachlor and alachlor. The fraction of the initial nitrate concentration found as excess N2 (N2 derived from denitrification) increased with ground-water age only at the North Carolina site, where oxic conditions were generally limited to the top 5 m of saturated thickness. Historical trends in fluxes to ground water were evaluated by relating the times of recharge of ground-water samples, estimated using chlorofluorocarbon concentrations, with concentrations of the parent compound at the time of recharge, estimated by summing the molar concentrations of the parent compound and its transformation products in the age-dated sample. Using this approach, nitrate concentrations were estimated to have increased markedly from 1960 to the present at all study sites. Trends in concentrations of atrazine, metolachlor, alachlor, and their degradates were related to the timing of introduction and use of these compounds. Degradates, and to a lesser extent parent compounds, were detected in ground water dating back to the time these compounds were introduced.