Comment on "Analysis of groundwater contamination using concentration-time series recorded during an integral pumping test: Bias introduced by strong concentration gradients within the plume" by Allelign Zeru and Gerhard Schäfer

We consider the results of a recent paper in this journal [Zeru, A. and Sch?fer, G., 2005. Analysis of groundwater contamination using concentration-time series recorded during an integral pumping test: Bias introduced by strong concentration gradients within the plume. Journal of Contaminant Hydrology 81 (2005) 106-124], which addresses the field-scale characterisation of contaminant plumes in groundwater. There, it is concluded that contaminant concentration gradients can bias Integral Pumping Test (IPT) interpretations considerably, in particular if IPTs are conducted in advective fronts of contaminant plumes. We discuss implications of this setting and also argue that the longitudinal and transverse dispersivities used in the examples of Zeru and Sch?fer (2005) of up to 30 m and 3 m, respectively, are generally very high for the here relevant capture zone scale (<20 m). However, regardless of both longitudinal and transverse concentration gradients, we further show through a counter-example that IPT results are unbiased as long as the concentration attenuation along the flow direction is linear over the capture zone extent.     

Structure of Mn-Zr mixed oxides catalysts and their catalytic performance in the gas-phase oxidation of chlorocarbons

The catalytic activity and selectivity of manganese zirconia mixed oxides were evaluated for the oxidation of two common chlorinated pollutants found in waste streams, namely 1,2-dichloroethane (DCE) and trichloroethylene (TCE). Mixed oxides with varying Mn-Zr content were prepared by coprecipitation via nitrates, and subsequent calcination at 600 degrees C for 4 h in air. These catalysts were characterised by means of several techniques such as atomic emission spectrometry, N2 adsorption-desorption, powder X-ray diffraction, temperature-programmed desorption of ammonia, pyridine adsorption followed by diffuse reflectance infrared spectroscopy and temperature-programmed reduction with hydrogen. The active catalytic behaviour of Mn-Zr mixed oxides was ascribed to a substantial surface acidity combined with readily accessible active oxygen species. Hence, the mixed oxide with 40 mol% manganese content was found to be an optimum catalyst for the combustion of both chlorocarbons with a T50 value around 305 and 315 degrees C for DCE and TCE oxidation, respectively. The major oxidation products were carbon dioxide, hydrogen chloride and chlorine. It was observed that the formation of both CO2 and Cl2 was promoted with Mn loading.     

Determination of selected quaternary ammonium compounds by liquid chromatography with mass spectrometry. Part I. Application to surface, waste and indirect discharge water samples in Austria

A method for simultaneous quantitative determination of alkyl benzyl, dialkyl and trialkyl quaternary ammonium compounds (QACs) has been developed, validated and subsequently applied to real water samples in Austria. The method employs liquid-liquid extraction (LLE) followed by liquid chromatography/tandem mass spectrometry (LC-MS/MS), using electrospray ionization (ESI) in positive mode. The overall method quantification limits range from 4 to 19ng/L for the enrichment of 500mL water samples and analyte recoveries are between 80 and 99%. The method was applied to 62 of the respective water samples without filtration to avoid the loss of the analytes due to the high adsorption capacity of these compounds. Maxima in the mg/L range, especially in the wastewater of hospitals and laundries, could be detected for the selected target compounds.     

Pyrolysis of mixtures of sewage sludge and manure: a comparison of the results obtained in the laboratory (semi-pilot) and in a pilot plant

A pilot-scale pyrolysis process was carried out for the treatment of a mixture of two types of waste, sewage sludge and cattle manure, comparing the results with others obtained under laboratory conditions (semi-pilot scale). The aim of this study was to obtain the energetic valorization of the products. Owing to the specific characteristics of the plant, two products were obtained from the process: gas and carbonized solid. As no liquid fraction was obtained, the gas fraction is a greater percentage made up of both condensable and non-condensable compounds, which were obtained separately at the laboratory scale. The pilot plant was designed so that the gases produced by thermolysis were burnt continuously in a combustion chamber, while the carbonized fraction was fed in batches for co-combustion. To determine composition and combustion ability, the gas and solid products from the pilot process were characterized by chromatographic analysis of the gaseous fraction and chemical analysis and programmed-temperature combustion of the carbonized solid. The composition of the combustion gases, rich in light hydrocarbons, and the carbon present in the carbonized fraction enable the energetic valorization of these products. The combustion gases were subjected to a cleaning process and their composition analysed twice: before and after the gas cleaning treatment. The study led to a positive assessment of the possible use of the process products as fuel, provided that the combustion gases are treated. As most of the sulphur and chlorine from the original waste are mainly concentrated in the solid fraction, the use of char as a fuel will depend on the effectiveness of clean-up techniques for combustion gases. During gas cleansing, neutralizing with sodium bicarbonate proved effective, especially for the acidic compounds HCl, HF and SO(2).     

Mercury species accumulation and trophic transfer in biological systems using the Almadén mining district (Ciudad Real,Spain) as a case of study

The impact of mercury (Hg) pollution in the terrestrial environments and the terrestrial food chains including the impact on human food consumption is still greatly under-investigated. In particular, studies including Hg speciation and detoxification strategies in terrestrial animals are almost non-existing, but these are key information with important implications for human beings. Therefore, in this work, we report on Hg species (inorganic mercury, iHg, and monomethylmercury, MeHg) distribution among terrestrial animal tissues obtained from a real-world Hg exposure scenario (Almadén mining district, Spain). Thus, we studied Hg species (iHg and MeHg) and total selenium (Se) content in liver and kidney of red deer (Cervus elaphus; n?=?41) and wild boar (Sus scrofa; n?=?16). Similar mercury species distribution was found for both red deer and wild boar. Major differences were found between tissues; thus, in kidney, iHg was clearly the predominant species (more than 81 %), while in liver, the species distribution was less homogeneous with a percentage of MeHg up to 46 % in some cases. Therefore, Hg accumulation and MeHg transfer were evident in terrestrial ecosystems. The interaction between total Se and Hg species has been evaluated by tissue and by animal species. Similar relationships were found in kidney for both Hg species in red deer and wild boar. However, in liver, there were differences between animals. The possible underlying mechanisms are discussed.     

The application of regenerable sorbents for mercury capture in gas phase

Mercury is a well-known toxic element, and flue gas streams emitted from coal-fired utilities are one of the largest anthropogenic sources of this element. This study briefly reviews the proposed technologies for reducing mercury emissions from coal combustion, focusing on an emerging process which involves the use of regenerable sorbents and especially those loaded with noble metals. Among the mercury species formed during coal combustion, elemental mercury is the most difficult to remove from the flue gases due to its low reactivity and insolubility in water. The widespread interest in using regenerable sorbents with metals is due to their ability to retain elemental mercury. With this technology, not only can efficiencies of 100 % be reached in the retention of elemental mercury but also a way to avoid the generation of new wastes loaded with mercury. This study considers the main aspects that must be taken into account when developing effective regenerable sorbents for mercury capture, with special attention to sorbents containing noble metals. The characteristics of this process are compared with those of other processes in a more advanced state of development.     

Source apportionment of PM2.5 for supporting control strategies in the Monterrey Metropolitan Area,Mexico

The Monterrey Metropolitan Area (MMA) in Northeast Mexico has shown high PM_2.5 concentrations since 2003. The data shows that the annual average concentration exceeds from 2 to 3 times the Mexican PM_2.5 annual air quality standard of 12 µg/m³. In a previous work we studied the chemical characterization of PM_2.5 in two sites of the MMA during the winter season. Among the most important components we found ammonium sulfate and nitrate, elemental and organic carbon, and crustal matter. In this work we present the results of a second chemical characterization study performed during the summer time and the application of the chemical mass balance (CMB) model to determine the source apportionment of air pollutants in the region. The chemical analysis results show that the chemical composition of PM_2.5 is similar in both sites and periods of the year. The results of the chemical analysis and the CMB model show that industrial, traffic, and combustion activities in the area are the major sources of primary PM_2.5 and precursor gases of secondary inorganic and organic aerosol (SO₂, NOx, NH₃, and volatile organic compounds [VOCs]). We also found that black carbon and organic carbon are important components of PM_2.5 in the MMA. These results are consistent with the MMA emission inventory that reports as major sources of particles and SO₂ a refinery and fuel combustion, as well as nitrogen oxides and ammonium from transportation and industrial activities in the MMA and ammonium form agricultural activities in the state. The results of this work are important to identify and support effective actions to reduce direct emissions of PM_2.5 and its precursor gases to improve air quality in the MMA. Implications: The Monterrey Metropolitan Area (MMA) has been classified as the most air-polluted area in Mexico by the World Health Organization (WHO). Effective actions need to be taken to control primary sources of PM_2.5 and its precursors, reducing health risks on the population exposed and their associated costs. The results of this study identify the main sources and their estimated contribution to PM_2.5 mass concentration, providing valuable information to the local environmental authorities to take decisions on PM_2.5 control strategies in the MMA.     

Geogenic Distribution of Arsenic (As) and Antimony (Sb) in Soils of the Murcia Region in Spain

The objective of this study was to determine the As and Sb contents in soils from the Murcia Region of Spain and the possible relationship between the mineralogical composition, soil properties, and As and Sb concentrations. In this study, 490 samples were selected from areas with different characteristics in order to study As and Sb variability. Results show that As and Sb concentrations are positively correlated with the phyllosilicate and quartz content but negatively correlated with the calcite content. The generic reference level (GRL) for these elements was determined according to the Spanish legislation. Established GRL values vary according to the established mineralogical groups, suggesting that GRL has to be determined considering the lithological characteristics of the study area.     

The use of bioaccumulation, biomarkers and histopathology diseases in shape Procambarus clarkii to establish bioavailability of Cd and Zn after a mining spill

Individuals of the crayfish Procambarus clarkii (males and females) were exposed simultaneously to cadmium and zinc during 21 days. Exposure concentrations were those determined at the Guadiamar river after the Aznalcóllar mining spill (SW, Spain): 10 and 30 μg L⁻¹ of cadmium and 1000 and 3000 μg L⁻¹ of zinc. Three biomarkers (MT: metallothioneins like proteins, VTG: vitellogenin/vitellin like proteins and histopathology) together with heavy metal bioaccumulation were determined in soft tissues of male and female P. clarkii. At the concentrations tested, increasing cadmium exposure resulted in increasing cadmium bioaccumulation and increasing subletal effects (induction of MT, VTG and histopathological damage in tissues). Nevertheless, although increasing zinc exposure showed increasing VTG induction and histopathological damages, not a positive relationship was determined with MT induction. Concerning to responses determined in male and female crayfishes only differences were found between sexes at the highest cadmium exposure concentration related to bioaccumulation in hepatopancreas tissues. Biomarkers responses to heavy metal contamination in this crayfish, even VTG induction not before tested in heavy metal contamination assessment in crustaceans resulted potential tools for the monitoring of heavy metal environmental contamination.