Heterogeneous photocatalytic degradation of prometryn in aqueous solutions under UV-Vis irradiation

In this study, the heterogeneous photocatalytic degradation of prometryn using TiO(2) as photocatalyst was investigated. The main objectives of the study were: (I) to evaluate the kinetics of the pesticide disappearance, (II) to compare the photocatalytic efficiency of two different types of TiO(2), (III) to examine the influence of various parameters such as initial concentration of pesticide or catalyst and presence of oxidants (H(2)O(2) and K(2)S(2)O(8)), (IV) to evaluate the degree of mineralization and (V) to assess the detoxification efficiency of the studied processes. The experiments were carried out in a 500 ml pyrex UV reactor equipped with a 125 W high-pressure mercury lamp surrounded by a pyrex filter blocking wavelengths below 290 nm. Prometryn concentration was determined using HPLC. It was found that the degradation of the pesticide follows the first order kinetics according to the Langmuir-Hinshelwood model. Parameters like the type and concentration of the catalyst affect the degradation rate. A synergistic effect was observed when an oxidant was added in the TiO(2) suspensions increasing the reaction rate of photodegradation. In order to examine the extent of pesticide mineralization, DOC measurements were carried out. After 6h of illumination, mineralization was achieved up to almost 70%. The toxicity of the treated solution was evaluated using the Microtox test based on the luminescent bacteria Vibrio fisheri, in order to compare the acute toxicity of prometryn and its photoproducts. The detoxification efficiency was found to be dependent on the studied system and it did not follow the rate of pesticide disappearance.     

Immersion frying for the thermal drying of sewage sludge: an economic assessment

This paper presents an economic study of a novel thermal fry-drying technology which transforms sewage sludge and recycled cooking oil (RCO) into a solid fuel. The process is shown to have significant potential advantage in terms of capital costs (by factors of several times) and comparable operating costs. Three potential variants of the process have been simulated and costed in terms of both capital and operating requirements for a commercial scale of operation. The differences are in the energy recovery systems, which include a simple condensation of the evaporated water and two different heat pump configurations. Simple condensation provides the simplest process, but the energy efficiency gain of an open heat pump offset this, making it economically somewhat more attractive. In terms of operating costs, current sludge dryers are dominated by maintenance and energy requirements, while for fry-drying these are comparatively small. Fry-drying running costs are dominated by provision of makeup waste oil. Cost reduction could focus on cheaper waste oil, e.g. from grease trap waste.     

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.     

Eutrophication conditions and ecological status in typical bays of Lake Taihu in China

Sampling was conducted at three site groups, group E (in East Taihu Bay), G (in Gonghu Bay) and M (in Meiliang Bay) in Lake Taihu. TN and TP concentrations among site groups was in the increasing order of E < G < M. TP level at G sites is at the critical threshold for loss of submersed macrophytes. Mean values of DO and Transparence showed different trend, i.e., E > G > M. The mean phytoplankton fresh-weight biomass at M sites was 5.81 mg/l, higher than that at E sites (4.96 mg/l) and G sites (5.18 mg/l). Mean zooplankton fresh-weight biomass was in the decreasing order of M (6.4 mg/l) > G (4.9 mg/l) > E (2.7 mg/l). However, Rotifera density was in the sequence of E > G > M. Both zooplankton biomass and phytoplankton biomass increased with the rise of TN and TP concentrations. Relationships between zooplankton biomass and phytoplankton biomass showed that zooplankton played a limited role in the control of algae in eutrophic lakes. Nutrient availability is much more important than zooplankton grazing pressure in controlling phytoplankton growth in lakes. For most sites in Lake Taihu, reduction of nutrient loading, as well as macrophyte conservation, zappears to be especially important in maintaining high water quality and regulating lake biological structure, but for M sites, it’s urgent to control nutrient inputs rather than to restore macrophyte community.     

Comparative on Causes and Accumulation of Selenium in the Tree-rings Ambient High-selenium Coal Combustion Area from Yutangba, Hubei, China

Toxic trace elements emitted during coal combustion are the main sources of air pollution. They are released into the atmosphere mainly in the forms of fine ash, smoke and flue, and thus adversely affect plant, animal and human health. Selenium is one of toxic and the most volatile in coal. Large amount of atmospheric emission of selenium, as well as selenium present and scrubber stockpiles in ash may create serious environmental problems. In the paper, on the basis of investigating the abundance and distribution of selenium in plant-rings during recent 20 years, the bioaccumulation of selenium is explained that selenium in plant, which were collected from the village of selenium-rich coal combustion, is much higher than that in plants collected away from the village of selenium-rich coal combustion. The main origins of selenium are selenium-rich coal combustion and high-selenium rock weathered. The selenium recycle by food chain and selenium will accumulate and redistribute in environments.     

Food aid and food crisis in Sub-Saharan Africa: Statistical trends and implications*

This paper documents the rapid expansion and changes in food aid flows to Sub-Saharan Africa up to mid-1985. Trends for Sub-Saharan Africa as a whole and for the more seriously affected countries are examined, as are the comparative experiences of food aid of individual countries in the region. Table 11 lists the Sub-Saharan African countries and indicates the most seriously affected food-short countries, as defined by the WFP/FAO task force. It should be borne in mind that some practical problems exist in compiling data on food aid. These include lack of availability of reliable data, especially of most recent data; lack of common terminology and definitions; and different accounting systems. These data problems are sometimes a source of confusion. However, the basic facts are clear: food aid gradually emerged during the early 1980s as a resource too often of considerable significance to many countries of Sub-Saharan Africa. These trends were only accelerated with the crisis of 1984-1985. These facts provide a point of reference for further analysis of the sources of the crisis, its actual dimensions and consequences.     

Treatability studies of naphthalene in soil,water and air with persulfate activated by iron(Ⅱ)

Chemical oxidation was applied to an artificially contaminated soil with naphthalene (NAP). Evaluation of NAP distribution and mass reduction in soil, water and air phases was carried out through mass balance. Evaluation of NAP distribution and mass reduction in soil, water and air phases was carried out through mass balance. The importance of the air phase analysis was emphasized by demonstrating how NAP behaves in a sealed system over a 4 hr reaction period. Design of Experiments method was applied to the following variables: sodium persulfate concentration [SP], ferrous sulfate concentration [FeSO₄], and pH. The system operated with a prefixed solid to liquid ratio of 1:2. The following conditions resulted in optimum NAP removal [SP] = 18.37 g/L, [FeSO₄] = 4.25 g/L and pH = 3.00. At the end of the 4 hr reaction, 62% of NAP was degraded. In the soil phase, the chemical oxidation reduced the NAP concentration thus achieving levels which comply with Brazilian and USA environmental legislations. Besides the NAP partitioning view, the monitoring of each phase allowed the variabilities assessment over the process, refining the knowledge of mass reduction. Based on NAP distribution in the system, this study demonstrates the importance of evaluating the presence of semi-volatile and volatile organic compounds in the air phase during remediation, so that there is greater control of the system as to the distribution and presence of the contaminant in the environment. The results highlight the importance of treating the contaminant in all its phases at the contaminated site.     

Characterization of atmospheric aerosol (PM10 and PM2.5) from a medium sized city in São Paulo state, Brazil

Air pollution causes deleterious effects on human health with aerosols being among the most polluting agents.The objective of this work is the characterization of the PM_(2.5) and PM_(10) aerosol mass in the atmosphere.The methods of analysis include WD-XRF and EDS.Data were correlated with meteorological information and air mass trajectories(model HYSPLIT)by multivariate analysis.A morphological structural analysis was also carried out to identify the probable sources of atmospheric aerosols in the city of Sao Jose do Rio Preto,Brazil.The mean mass concentration values obtained were 24.54 μg/m~3 for PM_(10),above the WHO annual standard value of 20 μg/m~3 and 10.88 μg/m~3 for PM_(2.5) whose WHO recommended limit is10 μg/m~3.WD-XRF analysis of the samples revealed Si and Al as major components of the coarse fraction.In the fine fraction,the major elements were Al and S.The SEM-FEG characterization allowed identifying the morphology of the particles in agglomerates,ellipsoids and filaments in the PM_(10),besides spherical in the PM_(2.5).The analysis by EDS corroborated WD-XRF results,identifying the crustal elements,aluminosilicates and elements of anthropogenic origin in the coarse fraction.For the fine fraction crustal elements were also identified;aluminosilicates,black carbon and spherical particles(C and O) originating from combustion processes were predominant.The use of multivariate analysis to correlate air mass trajectories with the results of the morpho-structural characterization of the particulate matter allowed confirmation of the complex composition of the particles resulting from the combination of both local and long-distance sources.     

Assessment of uncertainty of NO2 measurements by the chemiluminescence method and discussion of the quality objective of the NO2 European Directive

Hereafter, an assessment of the ability of the chemiluminescence method to measure ambient NO2 with an accuracy within 15%, as requested by the data quality objective of European directive 1999/30/CE, is presented. In general, uncertainty is evaluated using the response to reference materials or by means of inter-comparisons used to determine some statistics like repeatability, reproducibility and calibration bias. These are incomplete approaches and the method of the Guide to the Expression of Uncertainty in Measurement, advised by the Directive, should be preferred. In fact, even if it requires a large data set, it allows the relative influence of all possible sources of uncertainty to be studied. The extent of NO2 uncertainty is mainly dependent on the level of NO. It is decreased by NOx and the correlation between NOx and NO. Furthermore, the uncertainty budget reveals that the contribution of accuracy of calibration standard, linearity, converter efficiency and drift of the analyser between calibration checks to the overall uncertainty is less important than the contribution of interference, mainly humidity and PAN in rural areas. The relative expanded uncertainty of the NO2 hourly average exceeds 30% for NO2 concentrations lower than 40 microg m(-3). Nevertheless, the data quality objective of 15% is reached for 200 microg m(-3), the hourly limit value of the European directive. On the contrary, at the limit value on the annual average, 40 microg m(-3), the data quality objective is not met if NO is higher than 100 microg m(-3). However, the data quality objective could be reached by correcting the measurements with the bias due to interference.