Chemical characterization and factor analysis of PM2.5 in two sites of Monterrey, Mexico

The Monterrey Metropolitan Area (MMA) has shown a high concentration of PM2.5 in its atmosphere since 2003. The contribution of possible sources of primary PM2.5 and its precursors is not known. In this paper we present the results of analyzing the chemical composition of sixty 24-hr samples of PM2.5 to determine possible sources of PM2.5 in the MMA. The samples were collected at the northeast and southeast of the MMA between November 22 and December 12, 2007, using low-volume devices. Teflon and quartz filters were used to collect the samples. The concentrations of 16 airborne trace elements were determined using x-ray fluorescence (XRF). Anions and cations were determined using ion chromatography. Organic carbon (OC) and elemental carbon (EC) were determined by thermal optical analysis. The results show that Ca had the maximum mean concentration of all elements studied, followed by S. Enrichment factors above 50 were calculated for S, Cl, Cu, Zn, Br and Pb. This indicates that these elements may come from anthropogenic sources. Overall, the major average components of PM2.5 were OC (41.7%), SO4(2-) (22.9%), EC (7.4%), crustal material (11.4%), and NO3- (12.6%), which altogether accounted for 96% of the mass. Statistically, we did not find any difference in SO4(2-) concentrations between the two sites. The fraction of secondary organic carbon was between 24% and 34%. The results of the factor analysis performed over 10 metals and OC and EC show that there are three main sources of PM2.5: crustal material and vehicle exhaust; industrial activity; and fuel oil burning. The results show that SO4(2-), OC, and crustal material are important components of PM2.5 in MMA. Further work is necessary to evaluate the proportion of secondary inorganic and organic aerosol in order to have a better understanding of the sources and precursors of aerosols in the MMA.     

Biodegradation of the herbicide glyphosate by filamentous fungi in platform shaker and batch bioreactor

The biodegradation conducted by microorganisms on herbicide glyphosate (N-phosphonomethylglycine) was investigated. Five strains of filamentous fungi belonging to the Fusarium genre were grown on Czapeck medium without phosphorous and supplemented with the addition of glyphosate. The assays were conducted to determine the ability of use as a phosphorous source, the inhibition caused by presence of herbicide, and the biodegradation in shaker and bioreactor by Fusarium strains. It was observed that the herbicide did not show any negative effect on microrganisms by quantity of the biomass. Among the strains tested, no inhibition was noted by the addition of glyphosate even at a high concentration. All strains studied were able to biodegrade it and use the herbicide as a phosphorous source. The formation of consortium was not better than the strains tested in pure culture. The biodegradation in the bioreactor was better than in the shaker. However, there wasn't any influence on biodegradation rate by changing the amount of oxygen in the system.     

Effects of probiotic bacteria on the bioaccessibility of aflatoxin B1 and ochratoxin A using an in vitro digestion model under fed conditions

In the present study, we aimed at determining the release of aflatoxin B₁ (AFB₁) and ochratoxin A (OTA) from different food products in the gastro-intestinal tract in the absence and presence of probiotics, a possible adsorbent. The average bioaccessibility of AFB₁ and OTA without probiotics was about 90%, and 30%, respectively, depending on several factors, such as food product, contamination level, compound and type of contamination (spiked versus naturally contaminated). The six probiotic bacteria showed varying binding capacity to AFB₁ and OTA depending on the bacterial strain, toxin studied, type of food and contamination level. A reduction to a maximum of 37% and 73% as observed for the bioaccessibility of AFB₁ and OTA in the presence of probiotic bacteria, respectively. This is the first report on the effect of probiotic bacteria on reducing the fraction of mycotoxins available for absorption in the gastrointestinal tract from different food products.     

Enhancing phytoextraction of Cd by combining poplar (clone “I-214”) with Pseudomonas fluorescens and microbial consortia

The plant–microorganism combinations may contribute to the success of phytoextraction of heavy metal-polluted soil. The purpose of this study was to investigate the effects of cadmium (Cd) soil concentration on selected physiological parameters of the poplar clone “I-214” inoculated at root level with a strain (BT4) of Pseudomonas fluorescens and a commercial product based on microbial consortia (Micosat F Fito®). Plants were subjected to Cd treatment of 40 mg kg^?1 in greenhouse. The effects of plant–microbe interactions, plant growth, leaf physiology, and microbial activity were periodically monitored. Metal concentration and translocation factors in plant tissues proved enhanced Cd uptake in roots of plants inoculated with P. fluorescens and transfer to shoots in plants inoculated with Micosat F Fito®, suggesting a promising strategy for using microbes in support of Cd uptake. Plant–microbe integration increased total removal of Cd, without interfering with plant growth, while improving the photosynthetic capacity. Two major mechanisms of metal phytoextraction inducted by microbial inoculation may be suggested: improved Cd accumulation in roots inoculated with P. fluorescens, implying phytostabilization prospective and high Cd transfer to shoots of inoculated plants, outlining enhanced metal translocation.     

Pharmaceuticals in the environment: an educational perspective

Purpose  

Pharmaceuticals are an integral part of a dignified life. However, a lack of degradability and threats to the welfare of living beings cause concern due to their emission into the environment. There is also a lack of knowledge about cause and consequence. Therefore, we intend to contribute to the development of educational programmes which should increasingly include the topic ‘pharmaceuticals in the environment’.     

Anthropogenic NOx emissions alter the intrinsic water-use efficiency (WUEi) for Quercus cerris stands under Mediterranean climate conditions

We investigated the effect of N deposition (Ndep) on intrinsic water-use efficiency (WUE_i), the ratio of photosynthesis (A) to stomatal conductance (g_s), for two Quercus cerris stands at different distances to an oil refinery in Southern Italy. We used δ¹³C in tree rings for assessing changes in WUE_i; while the influence of climate and NO_x emission was explored through δ¹⁸O and δ¹⁵N, respectively. Differences in WUE_i between the two sites were significant, with trees exposed to different degrees of NO_x emissions showing an abrupt increase with the onset of pollution. Assuming similar g_s at the two sites, as inferred through δ¹⁸O, the higher N availability at the polluted site caused the shift of the A/g_s ratio in favour of A. Overall, our result suggests that an increase of Ndep may enhance tree WUE under a scenario of reduction of precipitation predicted for Mediterranean area.     

Hyperaccumulation of vanadium in the Antarctic polychaete Perkinsiana littoralis as a natural chemical defense against predation

Background, aim, and scope  

Exceptionally high levels of trace metals have been reported in specific tissues of certain polychaetes. In the present study, the Antarctic fan worm Perkinsiana littoralis was shown to hyperaccumulate vanadium in the branchial tissues, and the hypothesis of an antipredatory strategy has been investigated     

Spatial and statistical assessment of factors influencing nitrate contamination in groundwater

The weights of evidence (WofE) modeling technique has been used to analyze both natural and anthropogenic factors influencing the occurrence of high nitrate concentrations in groundwater resources located in the central part of the Po Plain (Northern Italy). The proposed methodology applied in the Lodi District combines measurements of nitrate concentrations, carried out by means of a monitoring net of 69 wells, with spatial data representing both categorical and numerical variables. These variables describe either potential sources of nitrate and the relative ease with which it may migrate towards groundwater. They include population density, nitrogen fertilizer loading, groundwater recharge, soil protective capacity, vadose zone permeability, groundwater depth, and saturated zone permeability. Once conditional dependence problems among factors have been solved and validation tests performed, the statistical approach has highlighted negative and positive correlations between geoenvironmental factors and nitrate concentration in groundwater. These results have been achieved analysing the calculated statistical parameters (weights, contrasts, normalized contrasts) of each class by which each factor has been previously subdivided. This has permitted to outline: the overall influence each factor has on the presence/absence of nitrate; the range of their values mostly influencing this presence/absence; the most and least critical combination of factor classes existing in each specific zone; areas where the influence of impacting factor classes is reduced by the presence of not impacting factor classes. This last aspect could represent an important support for a correct land use management to preserve groundwater quality.     

Concentration statistics for mixing-controlled reactive transport in random heterogeneous media

Uncertainty in the distribution of hydraulic parameters leads to uncertainty in flow and reactive transport. Traditional stochastic analysis of solute transport in heterogeneous media has focused on the ensemble mean of conservative-tracer concentration. Studies in the past years have shown that the mean concentration often is associated with a high variance. Because the range of possible concentration values is bounded, a high variance implies high probability weights on the extreme values. In certain cases of mixing-controlled reactive transport, concentrations of conservative tracers, denoted mixing ratios, can be mapped to those of constituents that react with each other upon mixing. This facilitates mapping entire statistical distributions from mixing ratios to reactive-constituent concentrations. In perturbative approximations, only the mean and variance of the mixing-ratio distribution are used. We demonstrate that the second-order perturbative approximation leads to erroneous or even physically impossible estimates of mean reactive-constituent concentrations when the variance of the mixing ratio is high and the relationship between the mixing ratio and the reactive-constituent concentrations strongly deviates from a quadratic function. The latter might be the case in biokinetic reactions or in equilibrium reactions with small equilibrium constant in comparison to the range of reactive-constituent concentrations. When only the mean and variance of the mixing ratio is known, we recommend assuming a distribution that meets the known bounds of the mixing ratio, such as the beta distribution, and mapping the assumed distribution of the mixing ratio to the distributions of the reactive constituents.