Arsenic uptake and accumulation in curly endives (Cichorium endivia L.) irrigated with contaminated water

Arsenic accumulation in vegetables for direct human consumption represents a concern for food safety purposes. This potential problem can be of economic importance particularly in much appreciated, high-quality horticultural products. In this work, a greenhouse set of experiments were conducted to evaluate possible phytotoxic effects and arsenic accumulation in the production of curly endives with arsenic contaminated water.Two concentration levels (0.5 mg/L and 1.0 mg/L) and two arsenic species (As+3 and As+5) were considered. Dry mass production tended to be reduced as As+3 concentration increased in irrigation water. However, As+5 treatments did not show significant dry mass production differences with a blank (control experiment). As accumulation in plant increased with As concentration in irrigation waters, following a linear trend. Nevertheless, the increase of accumulated As was not statistically significant for As+5 at 0.5 mg/L. Calculated biological absorption coefficients resulted in higher than previous values reported in the literature, which was attributed here to the source of arsenic (irrigation water). Considering field values for As+5/As+3 ratio and averaged concentrations in water, the obtained results support that there is not a short-or medium-term risk to food safety in the curly endive crop in the region of Castilla y León (Spain).     

Carcinogenic and co-carcinogenic potential of 2,3,7,8-tetrachlorodibenzo-p-dioxin in a host-mediated in vivo/in vitro assay

In an in vivo/in vitro assay system (Massa et al., 1990) we have detected the carcinogenic activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The carcinogenic potential measured in this system is concentration-dependent. Experiments with other carcinogenic compounds have revealed that TCDD at low doses can act as co-carcinogen. At higher concentrations TCDD induces TNF-α production.     

Characterization of the organic matter of sludge: determination of lipids, hydrocarbons and PAHs from road retention/infiltration ponds in France

This paper presents the results of the organic matter characterization of sludge from two ponds (retention and infiltration) located in France. Special focus was placed on studying hydrocarbons and PAHs. This investigation is part of a global project on road and urban sludge with the aim of identifying a better means for managing these materials. Gas chromatographic and GC/MS analyses indicate that the main component of the organic fraction stems from petroleum-derived products like diesel fuel and motor oil. This finding was confirmed by the presence of biomarkers from the hopane series, as well as by pyrolytic and alkylated PAHs. Results from this study clearly show that the contaminants are mainly generated from anthropogenic petroleum sources. Due to their levels of hydrocarbon contamination, these sludge deposits must be considered as waste and cannot therefore be disposed anywhere, especially within the current context of sustainable development.     

Changes in soil quality and below-ground carbon storage with conversion of traditional agricultural crop lands to bioenergy crop production

Berm-isolated (0.5 ha) plots have been used since 1995 to quantify changes in soil and water quality with conversion from agricultural to bioenergy crops. Soil quality improvements, including increases in soil carbon storage, have occurred on sites planted to woody or herbaceous species, and no-till corn compared with tilled corn or cotton. Initial increases in soil carbon occurred within the upper 10 cm of the soil profile. Soil carbon on plantings of switchgrass, no-till corn, and sweetgum with a cover crop between the rows increased over the first 3 years. Soil carbon decreased by 6% on the sweetgum plantings without a cover crop and remained lower through the fifth growing season. Overall, the greatest increases in below ground carbon storage have occurred primarily within the upper 40 cm. Former land use, growth characteristics, management practices, and soil characteristics appear to be the primary factors determining the timing, depth. and extent of changes in soil carbon storage for bioenergy and no-till crops.     

Reducing Interference Effects in the Chemiluminescent Measurement of Nitric Oxides from Combustion Systems

Experiments were carried out to determine the relative chemiluminescence quenching efficiencies as a function of third body concentration for each of the common combustion products, H₂O, CO₂, CO, H₂, O₂ and Ar. These results are compared with those of other investigators. The effect of reaction chamber pressure on analyzer response and the development of an analyzer design which incorporates an adjustable sample capillary inlet capable of maintaining a constant molar flow rate of sample gas to the reaction chamber are discussed. The effect of carbon monoxide interference on chemiluminescent NO_x measurement has been isolated and found to be significant. A means of correcting NO, measurements for these CO interference effects is described. Quantification of NO and NO₂ absorption in liquid water in NO_x sampling systems has been made. Recommendations for sample system designs to handle the presence of water in the sample gas are made.     

Nitrogen deposition in California forests: a review

Atmospheric concentrations and deposition of the major nitrogenous (N) compounds and their biological effects in California forests are reviewed. Climatic characteristics of California are summarized in light of their effects on pollutant accumulation and transport. Over large areas of the state dry deposition is of greater magnitude than wet deposition due to the arid climate. However, fog deposition can also be significant in areas where seasonal fogs and N pollution sources coincide. The dominance of dry deposition is magnified in airsheds with frequent temperature inversions such as occur in the Los Angeles Air Basin. Most of the deposition in such areas occurs in summer as a result of surface deposition of nitric acid vapor (HNO3) as well as particulate nitrate (NO3-) and ammonium (NH4+). Internal uptake of gaseous N pollutants such as nitrogen dioxide (NO2), nitric oxide (NO), HNO3, peroxyacetyl nitrate (PAN), ammonia (NH3), and others provides additional N to forests. However, summer drought and subsequent lower stomatal conductance of plants tend to limit plant utilization of gaseous N. Nitrogen deposition is much greater than S deposition in California. In locations close to photochemical smog source areas, concentrations of oxidized forms of N (NO2, HNO3, PAN) dominate, while in areas near agricultural activities the importance of reduced N forms (NH3, NH4+) significantly increases. Little data from California forests are available for most of the gaseous N pollutants. Total inorganic N deposition in the most highly-exposed forests in the Los Angeles Air Basin may be as high as 25-45 kg ha(-1) year(-1). Nitrogen deposition in these highly-exposed areas has led to N saturation of chaparral and mixed conifer stands. In N saturated forests high concentrations of NO3- are found in streamwater, soil solution, and in foliage. Nitric oxide emissions from soil and foliar N:P ratios are also high in N saturated sites. Further research is needed to determine the ecological effects of chronic N deposition, and to develop appropriate management options for protecting water quality and managing plant nutrient resources in ecosystems which no longer retain excess N.     

Survival of Escherichia coli in stormwater biofilters

Biofilters are widely adopted in Australia for stormwater treatment, but the reported removal of common faecal indicators (such as Escherichia coli (E. coli)) varies from net removal to net leaching. Currently, the underlying mechanisms that govern the faecal microbial removal in the biofilters are poorly understood. Therefore, it is important to study retention and subsequent survival of faecal microorganisms in the biofilters under different biofilter designs and operational characteristics. The current study investigates how E. coli survival is influenced by temperature, moisture content, sunlight exposure and presence of other microorganisms in filter media and top surface sediment. Soil samples were taken from two different biofilters to investigate E. coli survival under controlled laboratory conditions. Results revealed that the presence of other microorganisms and temperature are vital stressors which govern the survival of E. coli captured either in the top surface sediment or filter media, while sunlight exposure and moisture content are important for the survival of E. coli captured in the top surface sediment compared to that of the filter media. Moreover, increased survival was found in the filter media compared to the top sediment, and sand filter media was found be more hostile than loamy sand filter media towards E. coli survival. Results also suggest that the contribution from the tested environmental stressors on E. coli survival in biofilters will be greatly affected by the seasonality and may vary from one site to another.     

Aerosol speciation and mass prediction from toluene oxidation under high NOx conditions

A kinetically based gas-particle partitioning box model is used to highlight the importance of parameter representation in the prediction of secondary organic aerosol (SOA) formation following the photo-oxidation of toluene. The model is initialized using experimental data from York University's indoor smog chamber and provides a prediction of the total aerosol yield and speciation. A series of model sensitivity experiments were performed to study the aerosol speciation and mass prediction under high NO_x conditions (VOC/NO_x = 0.2). Sensitivity experiments indicate vapour pressure estimation to be a large area of weakness in predicting aerosol mass, creating an average total error range of 70 μg m^?3 (range of 5–145 μg m^?3), using two different estimation methods. Aerosol speciation proved relatively insensitive to changes in vapour pressure. One species, 3-methyl-6-nitro-catechol, dominated the aerosol phase regardless of the vapour pressure parameterization used and comprised 73–88% of the aerosol by mass. The dominance is associated with the large concentration of 3-methyl-6-nitro-catechol in the gas-phase. The high NO_x initial conditions of this study suggests that the predominance of 3-methyl-6-nitro-catechol likely results from the cresol-forming branch in the Master Chemical Mechanism taking a significant role in secondary organic aerosol formation under high NO_x conditions. Further research into the yields and speciation leading to this reaction product is recommended.