Rhizobacteria possess a wide variety of qualities governing their pollutant-catabolic and rhizospheric competences. We investigated how the abilities to degrade phenanthrene and other polycyclic aromatic hydrocarbons (PAHs), to synthesize surfactants and the phytohormone indole-3-acetic acid (IAA), to be motile, and to perform chemotaxis toward phenanthrene and some potential root-exudate components were manifested in rhizobacteria isolated from oil-polluted sites. We observed that most of the examined rhizobacteria had the abilities under consideration and that in some strains, these were strongly affected by the bacterial environment. Only one strain--Sinorhizobium meliloti P221--exhibited increased PAH-degrading, surfactant-producing, and IAA-synthesizing activities, as well as distinct behavioral responses. We conclude that S. meliloti P221 can be used as a model to assess the contributions of all these activities to plant-inoculation-induced reduction in the soil PAH contents. This strain also may be useful for phytoremediation applications.

The chemical, mineralogical, and leaching behavior of three dominant Greek forest species ashes (Pinus halepensis, Pistacia lentiscus, and Olea europaea), before and after treating forest species with diammonium phosphate (DAP) 5% and 10% weight to weight, have been studied using a new five-step shake leaching method at pH = 6. For the analysis of ashes (prior and after leaching) and leachants, the following analytical techniques were used: atomic absorption spectroscopy, X-ray diffraction, and scanning electron microscopy with energy dispersive X-ray fluorescence analysis. The presence of DAP obstructs the extraction process of some metal ions (i.e., Na, K) contained in ashes by converting the soluble carbonate salts to the less soluble phosphates (i.e., Na₂CO₃ [rightward arrow] Na₃PO₄). On the contrary, DAP enhances the mobility of some other metals (i.e., Ca) by forming more soluble compounds [i.e., CaCO₃ [rightward arrow] Ca₃(PO₄)₂]. In addition, the presence of DAP lowers the pH of leachates, causing dissolution of some toxic elements (i.e., Mn, Pb, Zn). Unexpectedly, DAP prevents the leachability of Cr from ash. The above study concerns the environmental effects (soil and ground and underground water streams) caused by the use of chemical retardants on forest fires.

All commercial gasoline fuels build up deposits on the spark plugs, injectors, oxygen sensors, catalytic converter, and inside the combustion chamber, which will lower the engine's performance and increase air pollution. As a result, fuel-based detergents have been developed to prevent and remove unwanted deposits. Unfortunately, many of the detergents use high amounts of aromatic solvents, which result in a greater risk of exposure to aromatic compounds like benzene. In this study, car exhaust was analyzed for benzene, toluene, ethylbenzene, and xylenes (BTEX), as well as formaldehyde and acetaldehyde during engine cleaning service using different chemical cleaners. A special device was designed for sampling from car exhaust using solid phase microextraction. The extracted compounds were analyzed using a gas chromatograph with flame ionization detector. The cleaning products were rated with regard to the amount of pollutants produced during the cleaning service.

Hydrophobic modified vermiculite mixed with soil was investigated in biodegradation experiments of naphthalene and anthracene. The experiments had been carried out on mixtures of soil and vermiculite at a proportion of 2%, 10%, and 15% and also in the absence of clay used for control. Biodegradation of the pollutants was followed by the decline of naphthalene and anthracene concentration, measured by CG. Compound mineralization was also proved by the evolution of CO₂. The results showed that in the mixture with a higher proportion of vermiculite biodegradation is enhanced compared to that performed in the absence of vermiculite. In general, when vermiculite proportions are increased, the rate of degradation increases, which may account for the bioavailability of compounds. Bioavailability is an important factor for the degradation of compounds with low solubility. Comparison of biodegradation rates shows that naphthalene is degraded faster than anthracene. The chemical structure could be responsible for this observation. However, although we did not identify the microorganism that was in the soil, we can conclude that vermiculite could be an alternative for the bioavailability of such compounds. Vermiculite in the modified form could also be very useful as a barrier to retain organic pollutants in accidental spills.

A commercial strain of the fungus Pleurotus ostreatus was used to mediate the degradation of lindane, by landfarming technology during a 4 weeks statistical experiment. The Multilevel Factorial Design was used with two design factors, namely, straw content X ₁ (%) and lindane content X ₂ (ppm). The optimization parameters (responses) investigated were: biodegradation rate Y ₁ (μg d⁻¹), biomass growth rate Y ₂ (mg d⁻¹), biodegradation/biomass Y ₃ (μg mg⁻¹), total organic carbon Y ₄ (%), total organic nitrogen Y ₅ (%) and total organic carbon/total organic nitrogen Y ₆. The optima of the adequate models obtained for the period of 2 and 4-weeks were found. An overall kinetic study, conducted in this work with the aid of experimental design, determined the optimum (maximum) specific lindane degradation rate to be 0.16 g kg⁻¹ month⁻¹.

Desorption of Cu, Cr, Pb, and Zn from industrially polluted soils as a result of acidification is in focus. The eight soils of the investigation vary greatly in composition and heavy metal concentration/combination. Three soils had elevated concentrations of Cu, Pb, and Zn; regardless of pollution level, pollution origin, and soil type, the order for desorption as pH decreased was Zn > Cu > Pb. Turning to a single heavy metal in different soils, there was a huge difference in the pH at which the major desorption started. The variation was most significant for Pb where, e.g., less than 10% was desorbed at pH 2.5 from one soil, whereas in another soil 60% Pb was desorbed at this pH. Sequential extraction was made and the soils in which a high percentage of Pb was found in the residual phase (adsorbed strongest) was also the soils where less Pb was desorbed at low pH in the desorption experiments. It was evident that Cu, Pb, and Zn started to desorb at a higher pH from calcareous soils than from soils with low carbonate content. The mechanism responsible for this is co-precipitation of heavy metals in the carbonates. When the carbonates are dissolved at a relatively high pH of about 5, the co-precipitated heavy metals are released. The sequential extraction pattern for Cr differed generally much from the other heavy metals since the majority of Cr was extracted in the last two steps. Cr was also the heavy metal that desorbed the least at high acidification.

This study was initiated to explore the effects of ozone (O₃) exposure on potted wheat roots and soil microbial community function. Three treatments were performed: (1) Air with daily averaged O₃ concentration of 4-10 ppb (control situation, CK), (2) Air plus 8 h averaged O₃ concentration of 76.1 ppb (O₃-1), and (3) Air plus 8 h averaged O₃ concentration of 118.8 ppb (O₃-2). In treatments with elevated O₃ concentration (O₃-1 and O₃-2), the root and shoot biomass were reduced by 25% and 18%, respectively, compared to the control treatment (CK). On the other hand, root activity was significantly reduced by 58% and 90.8% in the O₃-1 and O₃-2 treatments, respectively, compared to CK. The soil microbial biomass was significantly reduced only in the highest O₃ concentration (O₃-2 treatment) in the rhizosphere soil. Soil microbial community composition was assessed under O₃ stress based on the changes in the sole carbon source utilization profiles of soil microbial communities using the Biolog[trade mark sign] system. Principal component analysis showed that there was significant discrimination in the sole-carbon source utilization pattern of soil microbial communities among the O₃ treatments in rhizosphere soil; however, there was none in the bulk soil. In rhizosphere soil, the functional richness of the soil microbial community was reduced by 27% and 38% in O₃-1 and O₃-2 treatments, respectively, compared to CK. O₃-2 treatment remarkably decreased the Shannon diversity index of soil microbial community function in rhizosphere soil, but the O₃-1 treatment did not. In the dominant microorganisms using carbon sources of carbohydrates and amino acids groups were significantly reduced by an elevated O₃ concentration in the rhizosphere soil. Our study shows that the elevated ozone levels may alter microbial community function in rhizosphere soil but not in the bulk soil. Hence, this suggests that O₃ effects on soil microbes are caused by O₃ detriments on the plant, but not by the O₃ direct effects on the soil microbes.

Automobile traffic pollutes roadside environments with a range of contaminants. In this study, we investigate the distribution patterns of different contaminant classes in topsoils across a highway-forest interface north-east of Vienna, Austria, in order to assess spatial pollutant distribution and evaluate the filtering effect of roadside forests. We collected soil samples along transects perpendicular to the highway, and analyzed the soils for road salt residues (Na), total and mobile heavy metals (Pb, Cd, Cu, Zn, Ni, Cr) as well as polycyclic aromatic hydrocarbons (PAHs). Roadside soil pollution was highly heterogeneous. All contaminants followed an exponential-like decrease with distance from the road, reaching background levels at 5 to 10 m from the road curb. Traffic-born heavy metals in the immediate roadside zone tended to be more mobile than heavy metals of predominantly geogenic origin at greater distances from the road; the presence of road salt residues could have contributed to the elevated heavy metal mobility near the road. The forest vegetation acted as filter for PAHs shown by a sharp concentration increase at the forest edge. PAHs are likely transported with airborne soot particles that are scavenged by the wax-coated coniferous needles at our study site.

This study examines the relationship between dissolved inorganic nitrogen (DIN: NH₄ ⁺ + NO₂ ⁻ + NO₃ ⁻) and dissolved organic nitrogen (DON) in river water and groundwater in an agriculturally-dominated catchment in south-east Spain, and estimates the contribution of DON to the total dissolved nitrogen (TDN) concentrations. The studied aquifer-dependent river system consists of Quaternary alluvial sediments deposited by the Guadalquivir River and its tributaries, with both river water and groundwater in the catchment being aerobic. DON is the predominant form of nitrogen in river water (72-97% of the TDN), whereas its proportion to TDN varies considerably in groundwater (<1-99%). A seasonal pattern in the concentration of dissolved nitrate in river water was observed, whereas DON concentrations showed no significant change during the study period. The export of DON from the Guadalquivir River is approximately 2 kg N ha⁻¹ year⁻¹ and is an order of magnitude higher than the export of DON from pristine catchments. Dissolved nitrate concentrations in groundwater were slightly higher in winter and DON concentrations were significantly lower (p < 0.05) in summer. It is found that agricultural soils constitute the main storage of organic nitrogen in the catchment with a steady leaching of high DON concentrations into the alluvial aquifer system (mean value 19.1 mg N L⁻¹), and so indicating that DON should not be overlooked in the nitrogen budgets of agriculturally-dominated catchments.

The present research reproduces the chemical and microbiological reactions that occur naturally when a metal sulfide is discharged onto a natural soil, with special emphasis on iron cycle. The role of indigenous microbiota from an extremely acidic site on both weathering and attenuation processes related to the iron mobilization has been studied and the iron cycle has been reproduced at laboratory scale. In the first stage, the weathering phase, a residual sulfide mineral was bioleached using a mixed culture of iron-oxidizing bacteria isolated from the own substrate. The acid liquor obtained (pH 2), with a high metal concentration (160 mM in total iron), was filtered and neutralized. Solids obtained from the two sources (from the weathering process and after the neutralization stage) were characterized by X-ray and scanning electron microscope/energy dispersive X-ray spectroscopy, resulting ferric iron precipitates such as jarosites, goethites, and ferrihydrites with different crystalline properties. The contribution of ferric iron-reducing bacteria on the attenuation of high-content iron effluents was also studied. Mixed cultures of ferric iron-reducing bacteria, isolated from those acidic substrates, were active in reducing soluble ferric iron (60 mM in concentration), and a 66% of bioreduction was reached after 15 days. Dissimilatory ferric iron reduction has been achieved with adapted cultures at pH values from 7 to 4.