Chemical composition and hygroscopic properties of size-segregated aerosol particles collected at the Adriatic coast of Slovenia

The chemical composition as well as the water uptake characteristics of aerosols was determined in size-segregated samples collected during November 2002 on the Slovenian coast. Major ions, water-soluble organic compounds (WSOC), short-chain carboxylic acids and trace elements were determined in the water-soluble fraction of the aerosol. Total aerosol black carbon (BC) was measured from filter samples. Our results showed that the origin of air masses is an important factor that controls the variation in the size distribution of the main components. Very high concentrations of WSOC as well as higher concentrations of BC were found under mostly continental influence. Besides the main ionic species (SO4(2-), NH4(+), K+) in the finest size fraction (0.17-0.53 microm), the concentration of NO3(-) was also high. The difference between the two different air mass origins is particularly expressed for Cl-, Na+, Mg2+ and Ca2+ determined in particles larger than 1.6 microm. As expected, a very good correlation was found between Na+ and Cl-. A good correlation was found between sea salt elements and elements of crustal origin (Na+, Cl-, Mg2+, Ca2+, Sr). A good relationship between typical anthropogenic tracers (K, V and Pb) was also observed. The mass growth factors, for all size fractions of aerosols collected under continental influence were very low (maximum 2.23 at 94%, 1.6-5.1 microm), while under marine influence the mass growth factors increased significantly with the particle size. At 97% humidity, the mass growth factors were 6.95 for the size fraction 0.53-1.6 microm and 9.78 for larger particles (1.6-5.1 microm).     

PM10 source apportionment in a Swiss Alpine valley impacted by highway traffic

Although trans-Alpine highway traffic exhaust is one of the major sources of air pollution along the highway valleys of the Alpine regions, little is known about its contribution to residential exposure and impact on respiratory health. In this paper, source-specific contributions to particulate matter with an aerodynamic diameter?<?10 μm (PM₁₀) and their spatio-temporal distribution were determined for later use in a pediatric asthma panel study in an Alpine village. PM₁₀ sources were identified by positive matrix factorization using chemical trace elements, elemental, and organic carbon from daily PM₁₀ filters collected between November 2007 and June 2009 at seven locations within the village. Of the nine sources identified, four were directly road traffic-related: traffic exhaust, road dust, tire and brake wear, and road salt contributing 16 %, 8 %, 1 %, and 2 % to annual PM₁₀ concentrations, respectively. They showed a clear dependence with distance to highway. Additional contributions were identified from secondary particles (27 %), biomass burning (18 %), railway (11 %), and mineral dust including a local construction site (13 %). Comparing these source contributions with known source-specific biomarkers (e.g., levoglucosan, nitro-polycyclic aromatic hydrocarbons) showed high agreement with biomass burning, moderate with secondary particles (in winter), and lowest agreement with traffic exhaust.     

Phytotoxic effects of phenolic acids from <Emphasis Type="Italic">Merostachys riedeliana,</Emphasis> a native and overabundant Brazilian bamboo

Merostachys riedeliana Rupr. is a native and overabundant bamboo species in the Brazilian Atlantic Forest. Moderate to strong allelopathic activity may be one mechanism that explains this super-dominance and the changes in structure and composition of forest areas occupied by bamboo. This study evaluated the phytotoxic effect of M. riedeliana extracts and fractions and identified their putative allelochemicals. We investigated the presence of allelochemicals in soil collected from stands occupied by M. riedeliana. Furthermore, we evaluated the putative effect of tree allelochemicals, individually and combined, on germination and growth. The aqueous extract of leaves and its ethyl acetate fraction presented the highest inhibitory effects on seed germination and seedling growth. The effect of the extracts and fractions on the target species was species-specific. Neither the individual nor the combined phenolic acids significantly inhibited seed germination; however, a pronounced growth inhibition was observed in M. bimucronata seedlings treated with vanillic acid and in E. verna and M. bimucronata seedlings treated with combined phenolic acids. Isovitexin, vitexin, isoorientin, orientin, and their O-glycoside derivatives, the lactonic dimer of the p-hydroxybenzoic acid and 3,4-methylenedioxymandelic acid were identified in the aqueous extracts and ethyl acetate fraction by Liquid Chromatography-Diode Array Dectector/Electrospray Ionization/Mass Spectrometry (LC-DAD/ESI–MS/MS). The Gas Chromatography-Mass Spectrometer (GC–MS) profile of the same extract and fraction showed the presence of benzoic, benzeneacetic, salicylic, p-hydroxybenzoic, p-hydroxyphenylacetic, vanillic, p-coumaric, protocatechuic, syringic, gallic, m-coumaric vanillylmandelic, 4-methylmandelic, 3,4-methylenedioxymandelic and trans-ferulic acids. The p-benzoic acid and the apigenin 6-C-glucoside (isovitexin) were identified in the soil extract collected from under bamboo-growing areas. Even though laboratory bioassays are not completely predictive of the allelopathic effects that occur in nature, the results of this study provide preliminary evidence of allelopathy as a possible species-specific inhibition mechanism of native species that explain the impoverishment of floristic richness and the functional groups in areas where M. riedeliana is overabundant.     

Design and cost estimation of permeable reactive barriers

Cost-effective use of permeable reactive barriers for groundwater treatment requires properly estimating the amount of reactive material required and choosing the best means of emplacing it. The weight of reactive material per unit cross section of the plume can be estimated from laboratory reaction kinetics data and basic knowledge of the plume and the remediation goals. This parameter has implications regarding the choice of permeable barrier design and emplacement method. The use of tremie tubes, trenching machines, high-pressure jetting, and deep soil mixing may be appropriate for different situations depending on the amount of reactive material required, the dimensions of the plume, and other factors. The specific application considered here is the use of granular iron to treat groundwater contaminated with chlorinated solvents.     

Optimizing the removal of carbon phases in soils and sediments for sequential chemical extractions by coulometry

We have developed a coulometric technique to optimize the removal of the carbonate and organic fractions for sequential chemical extractions of soils and sediments. The coulometric system facilitates optimizing these two fractions by direct real-time measurement of carbon dioxide (CO2) evolved during the removal of these two fractions. Further analyses by ICP-MS and alpha-spectrometry aided in interpreting the results of coulometry experiments. The effects of time, temperature, ionic strength and pH were investigated. The sensitivity of the coulometric reaction vessel/detection system was sufficient even at very low total carbon content (< 0.1 mol kg-1). The efficiency of the system is estimated to be 96% with a standard deviation of 8%. Experiments were carried out using NIST Standard Reference Materials 4357 Ocean Sediment (OS), 2704 Buffalo River Sediment (BRS), and pure calcium carbonate. Carbonate minerals were dissolved selectively using an ammonium acetate-acetic acid buffer. Organic matter was then oxidized to CO2 using hydrogen peroxide (H2O2) in nitric acid. The carbonate fraction was completely dissolved within 120 min under all conditions examined (literature suggests up to 8 h). For the OS standard, the oxidation of organic matter self-perpetuates between 45 and 50 degrees C, a factor of two less than commonly suggested, while organic carbon in the BRS standard required 80 degrees C for the reaction to proceed to completion. For complete oxidation of organic matter, we find that at least three additions of H2O2 are required (popular methods suggest one or two).     

Cytotoxic and genotoxic effects of silver nanoparticle/carboxymethyl cellulose on <Emphasis Type="Italic">Allium cepa</Emphasis>

Several mutagenic agents may be present in substances released in the environment, which may cause serious environmental impacts. Among these substances, there is a special concern regarding the widespread use of silver nanoparticles (AgNP) in several products due to their widely known bactericidal properties, including in the medical field and the food industry (e.g., active packaging). The assessment of the effects of AgNP released in the environment, having different concentrations, sizes, and being associated or not to other types of materials, including polymers, is therefore essential. In this research, the objective was to evaluate the genotoxic and cytotoxic effects of AgNP (size range between 2 and 8 nm) on root meristematic cells of Allium cepa (A. cepa). Tests were carried out in the presence of colloidal solution of AgNP and AgNP mixed with carboxymethylcellulose (CMC), using distinct concentrations of AgNP. As a result, when compared to control samples, AgNP induced a mitotic index decrease and an increase of chromosomal aberration number for two studied concentrations. When AgNP was in the presence of CMC, no cytotoxic potential was verified, but only the genotoxic potential for AgNP dispersion having concentration of 12.4 ppm.