Biodegradation of wastewater nitrogen compounds in fractures: laboratory tests and field observations

Throughout several coastal regions in the Mediterranean where rainfalls rarely exceed 650 mm per year municipal treated wastewater can be conveniently reused for soil irrigation. Where the coastal aquifer supplies large populations with freshwater in such area, an assessment of ground water quality around spreading sites is needed. In this study, the efficacy of natural filtration on nitrogen degradation in wastewater spreads on the soil covering the Salento (Southern Italy) fractured limestone was quantified by using laboratory tests and field measurements. In the laboratory, effluent from municipal wastewater treatment plants was filtered through a package of fractures made by several slabs of limestone. An analysis of wastewater constituent concentrations over time allowed the decay rates and constants for nitrogen transformation during natural filtration to be estimated in both aerated and non-aerated (i.e., saturated) soil fractures. A simulation code, based on biodegradation decay constants defined in the laboratory experiments, was then used to quantify the total inorganic nitrogen removal from wastewater injected in an aquifer in the Salento region (Nardò). Here the water sampled in two monitoring wells at 320 m and 500 m from the wastewater injection site and downgradient with respect to groundwater flow was used to verify the laboratory nitrification and denitrification rates.     

Distribution of volatile organic compounds in Madrid (Spain)

From November 1995 to October 1996, airborne concentrations of VOCs were measured in the Madrid area to study the organic pollution in general, and the correlation between different pollutants in relation to such parameters as location and season. Mean concentrations for up to 90 compounds were measured at four test sites, including both urban and suburban areas. At the urban sites, maximum concentrations occurred in the autumn and winter, whereas minimum concentrations were reached in summer and spring. Similar changes were obtained for the lesscontaminated site located in the SE of the city, whereas a different pattern was found at the site in the NW of the city due to meteorological aspects. Mean levels of hydrocarbons in Madrid were quite similar to those found in other European cities. Chemometrical techniques were applied to the set of data in order to assess the influence of such factors as traffic, temperature and seasonal variations on the VOC levels.     

工作场所手传振动测量

在职业卫生领域中,振动加速度有效值是最常用的测量值,振动加速度级的运用方便了运算和表述。给出频率计权和时间加权的计算公式和方法、加速度与加速度级间的换算。测量中强调了传感器定位和紧固方法会影响测量结果。     

Evaluation of Monte Carlo-based calibrations of HPGe detectors for in situ gamma-ray spectrometry

The aim of this work was to evaluate the use of Monte Carlo-based calibrations for in situ gamma-ray spectrometry. We have performed in situ measurements at five different sites in Sweden using HPGe detectors to determine ground deposition activity levels of ¹³⁷Cs from the 1986 Chernobyl accident. Monte Carlo-calculated efficiency calibration factors were compared with corresponding values calculated using a more traditional semi-empirical method. In addition, results for the activity ground deposition were also compared with activity densities found in soil samples. In order to facilitate meaningful comparisons between the different types of results, the combined standard uncertainty of in situ measurements was assessed for both calibration methods. Good agreement, both between the two calibration methods, and between in situ measurements and soil samples, was found at all five sites. Uncertainties in in situ measurements for the given measurement conditions, about 20 years after the fallout occurred, were found to be in the range 15–20% (with a coverage factor k = 1, i.e. with a confidence interval of about 68%).     

Characterization of phosphogypsum wastes associated with phosphoric acid and fertilizers production

The present work is directed to characterize the phosphogypsum (PG) wastes associated with phosphoric acid produced by the wet process in industrial facility for the production of fertilizers and chemicals in Egypt. The PG waste samples were characterized in terms of spectroscopic analysis (X-ray diffraction, X-ray fluorescence, IR spectra) and radiometric analysis (γ- and α-measurements). The γ-ray measurements showed that the average activity concentrations are 140 ± 12.6, 459 ± 36.7, 323 ± 28.4, 8.3 ± 0.76 and 64.3 ± 4.1 Bq/kg for U-238, Ra-226, Pb-210, Th-232 and K-40, respectively. The α-particle measurements of uranium isotopes showed that the average activity concentrations of U-238, U-235 and U-234 were 153 ± 9.8, 7 ± 0.38, 152 ± 10.4 Bq/kg, respectively. The average radiochemical recovery (%) of the destructive α-particle measurements is ∼70% with a resolution (FWHM) of ∼30 keV. Activity ratios of U-238/Ra-226 and U-238/Pb-210 were less than unity (i.e., <1) and equal to 0.31 ± 0.02 and 0.47 ± 0.16, respectively. The isotopic ratios of U-238/U-235 and U-238/U-234 (in PG and PR samples) were close to the normal values of ∼21.7 and ∼1, respectively and are not affected by the wet processing of phosphate rock (PR). The obtained results of PG waste samples were compared with phosphate rock (PR) samples. The radiation hazard indices are namely, radium activity index (Ra-Eq > 370 Bq/kg), total absorbed gamma dose rate (D_γr > 5 nGy/h) and radon emanation fraction (Rn-EF > 20%). Uncertainty of the sample counting was 95% confidence level of σ. The results indicated the necessity to find suitable routes to decrease and/or redistribute the radionuclide of environmental interest (i.e., Ra-226) in PG wastes, consequently to reduce its radiation impacts in the surrounding environment.     

Integrating Large Wood Jams into Hydraulic Models: Evaluating a Porous Plate Modeling Method

Large wood (LW) jams are key riverine habitat features that affect hydraulic processes and aquatic habitat. The hydraulic influence of LW jams is poorly understood due to the complexity of fluid dynamics around irregular, porous structures. Here we validated a method for two‐dimensional hydraulic modeling of porous LW jams using the open‐source modeling software Delft3D‐FLOW. We sampled 19 LW jams at three reaches across the Columbia River Basin in the United States. We used computer‐generated porous plates to represent LW jams in the modeling software and calibrated our modeling method by comparing model outputs to measured depths and velocities at validation points. We found that modeling outputs are error‐prone when LW jams are not represented. By representing LW jams as porous plates we reduced average velocity root mean square error (RMSE) values (i.e., improved model accuracy) by 42.8% and reduced average depth RMSE values by 5.2%. These differences impacted habitat suitability index modeling. We found a 15.1% increase in weighted useable area for juvenile steelhead at one test site when LW jams were simulated vs. when they were ignored. We investigated patterns in average RMSE improvements with varying jam size, bankfull obstruction, porosity, and structure type, and river complexity. We also identified research gaps related to field estimation of LW jam porosity and porous structure modeling methods.     

普光气田开发对地下水环境的影响分析

为最大程度缓解工程实施对当地地下水环境的破坏,文章在综合分析普光气田地质和水文地质特征的基础上,开展现场水质监测工作,选用内梅罗指数法评价区域地下水质量现状。结果表明:普光气田开发建设工程对区域地下水环境质量影响较小,地下水水质良好。在此基础上,探讨项目建设过程中的地下水环境影响因素,据此提出针对性的环境保护措施,以期为研究区地下水环境保护提供科学参考依据。     

An approach to the subslab depressurization remedial action in a high Rn concentration dwelling

Galicia (NW Spain) is a radon-prone area in the Iberian Peninsula. Measurements were carried out at a rural dwelling, with an annual average of radon concentration over 4000 Bq m⁻³ and a maximum of 9000 Bq m⁻³, found during a radon screening campaign held in the Autonomous Community of Galicia. We performed a detailed study to identify the main contamination source and the behaviour of the radon concentration, in which a linear dependence with temperature was verified, once corrected for relative humidity. We used different passive methods (charcoal canisters and two types of etched track detectors) as well as a radon concentration monitor that provided continuous measurement. Subsequent to this characterization, and in order to reduce the high radon concentration, a remedial action was developed using different passive and forced ventilation methods. A modified subslab depressurization technique was found to be the most effective remedy, providing a radon concentration reduction of around 96%. This method also has the advantages of being inexpensive and reliable over time.     

Evaluation of the International Vehicle Emission （IVE） model with on-road remote sensing measurements

Intemational Vehicle Emissions （IVE） model funded by U.S. Environmental Protection Agency （USEPA） is designed to estimate emissions from motor vehicles in developing countries. In this study, the IVE model was evaluated by utilizing a dataset available from the remote sensing measurements on a large number of vehicles at five different sites in Hangzhou, China, in 2004 and 2005. Average fuel-based emission factors derived from the remote sensing measurements were compared with corresponding emission factors derived from IVE calculations for urban, hot stabilized condition. The results show a good agreement between the two methods for gasoline passenger cars＇ HC emission for all 1VE subsectors and technology classes. In the case of CO emissions, the modeled results were reasonably good, although systematically underestimate the emissions by almost 12%-50% for different technology classes. However, the model totally overestimated NOx emissions. The IVE NOx emission factors were 1.5-3.5 times of the remote sensing measured ones. The IVE model was also evaluated for light duty gasoline truck, heavy duty gasoline vehicles and motor cycles. A notable result was observed that the decrease in emissions from technology class State II to State I were overestimated by the IVE model compared to remote sensing measurements for all the three pollutants. Finally, in order to improve emission estimation, the adjusted base emission factors from local studies are strongly recommended to be used in the IVE model.     

典型喀斯特区侵蚀性降雨特征及坡面生物措施水土流失防控效应

降雨类型和生物措施是坡面水土流失的重要影响因素.为研究喀斯特区降雨类型和不同坡面生物措施共同作用下的水土保持效益,以贵州蚂蟥田小流域水土保持监测站2014—2018年5年的径流小区实测数据为基础,分析了112场次的侵蚀性降雨特征,并以降雨量、降雨历时、平均降雨强度为指标对其进行分类.同时,分析了不同侵蚀性降雨类型下6个...