To assess strategies for mitigating Pb and As transfer into leafy vegetables from contaminated garden soils, we conducted greenhouse experiments using two field-contaminated soils amended with materials expected to reduce metal phytoavailability. Lettuce and mustard greens grown on these soils were analyzed by ICP-MS, showing that some Pb and As transfer into the vegetables occurred from both soils tested, but plant Pb concentrations were highly variable among treatment replicates. Soil-to-plant transfer was more efficient for As than for Pb. Contamination of the leaves by soil particles probably accounted for most of the vegetable Pb, since plant Pb concentrations were correlated to plant tissue concentrations of the immobile soil elements Al and Fe. This correlation was not observed for vegetable As concentrations, evidence that most of the soil-to-plant transfer for this toxic metal occurred by root uptake and translocation into the above-ground tissues. A follow-up greenhouse experiment with lettuce on one of the two contaminated soils revealed a lower and less variable foliar Pb concentration than observed in the first experiment, with evidence of less soil particle contamination of the crop. This reduced transfer of Pb to the crop appeared to be a physical effect attributable to the greater biomass causing reduced overall exposure of the above-ground tissues to the soil surface. Attempts to reduce soil Pb and As solubility and plant uptake by amendment at practical rates with stabilizing materials, including composts, peat, Ca phosphate, gypsum, and Fe oxide, were generally unsuccessful. Only Fe oxide reduced soluble As in the soil, but this effect did not persist. Phosphate amendment rapidly increased soil As solubility but had no measurable effect on either soil Pb solubility or concentrations of Pb or As in the leafy vegetables. The ineffectiveness of these amendments in reducing Pb transfer into leafy vegetables is attributed in this study to the low initial Pb solubility of the studied soils and the fact that the primary mechanism of Pb transfer is physical contamination.

Soil vapor extraction (SVE) is one of the most effective remediation technologies for soil and groundwater contamination. Soil particles can be mobilized by air perturbation during SVE, resulting in the differentiation of porous media, which has not been well addressed. This paper developed a numerical method to study the flow pattern and quantify the change of porous media for the first time. Based on the mass equilibrium and Darcy’s law, a two-phase water–air flow model was constructed with integration of saturation, relative permeability, and capillary pressure during SVE. Relationship between porosity and saturation was deduced and coupled with the two-phase flow model for quantifying change of porous media in real time. Results reveal that both porosity and permeability increase sharply in the early stage of SVE then gradually to a quasi-steady state. These increases in vadose zone tapered off with distance from the SVE screen and the steady period occurred later as well. The influence radius of a single SVE well and the change degree in porosity and permeability of media were proportional to the extraction vacuum and the driving coefficient C, which is more sensitive than extraction vacuum according to the simulation results. Knowledge from this modeling exercise provides a useful tool to estimate the change of remediated zone and assess the environmental risk of remedial activities at real-world contamination sites.

Synthetic hydroxyapatite (HA) and natural phosphate rock (PR) were applied to heavy metal-contaminated soils from sulfide mine areas in Sardinia and Tuscany (Italy). The application of phosphate amendments to the polluted mine waste soils reduced water-soluble concentrations of Co and Ni by about 99 %. In general, phosphate treatment was slightly more effective in reducing water solubility of Co and Ni in the Sardinian soils than in the Tuscan ones. This result suggests that the mineralogical composition of the mine waste soils may impact the effectiveness of metal immobilization. The formation of complexes of the heavy metals on the surface of phosphate grains and partial dissolution of the amendments and precipitation of heavy metal-containing phosphates are the dominant immobilization mechanisms. Between the phosphate amendments, PR was slightly less effective than HA in immobilizing Co and Ni. This result could be attributed to PR inability to provide soluble phosphate. Although with lower effectiveness, the use of PR to immobilize heavy metals from contaminated soils may reduce the risk of phosphate-induced eutrophication due to the application of amendments with highly soluble phosphate.

Reduction of bulk organic matter, nitrogen, and pharmaceutically active compounds from primary effluent during managed aquifer recharge was investigated using laboratory-scale batch reactors. Biologically stable batch reactors were spiked with different concentrations of sodium azide to inhibit biological activity and probe the effect of microbial activity on attenuation of various pollutants of concern. The experimental results obtained revealed that removal of dissolved organic carbon correlated with active microbial biomass. Furthermore, addition of 2 mM of sodium azide affected nitrite-oxidizing bacteria leading to accumulation of nitrite-nitrogen in the reactors while an ammonium-nitrogen reduction of 95.5 % was achieved. Removal efficiencies of the hydrophilic neutral compounds phenacetin, paracetamol, and caffeine were independent of the extent of the active microbial biomass and were >90 % in all reactors, whereas removal of pentoxifylline was dependent on the biological stability of the reactor. However, hydrophobic ionic compounds exhibited removal efficiency >80 % in batch reactors with the highest biological activity as evidenced by high concentration of adenosine triphosphate. © 2013 Springer Science+Business Media Dordrecht.

The aim of this work was to investigate the susceptibility of the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to biodegradation in a range of soils and to identify RDX-degrading organisms using stable isotope probing (SIP). RDX degradation was examined in ten soils, primarily from agricultural areas. RDX biodegradation was observed in six samples and only when the microcosms were not aerated. For one soil, 15N-and 13C-based DNA SIP was used to identify the microorganisms responsible for RDX degradation. Two RDX concentrations were examined (10 and 20 mg/L), however, only the higher concentration resulted in a significant SIP signal. In these ultracentrifugation fractions, one terminal restriction fragment length polymorphism (TRFLP) fragment (260 bp) showed a reliable trend of label uptake. This fragment was of higher relative abundance in the heavier fractions from labeled samples compared with the heavier fractions from the unlabeled control samples, indicating that the organism producing this fragment was responsible for label uptake (hence RDX degradation). Partial 16S rRNA gene sequencing indicated the organisms represented by fragment 260 bp belonged to either Sphingobacteria (phylum Bacteroidetes) or the phylum Acidobacteria. To date, these organisms have not previously been directly linked to RDX degradation. The 16S rRNA sequences were compared with the NCBI database and, in all cases, were most similar to uncultured bacteria. The results suggest SIP is a viable method for discovering novel, previously uncultured, RDX degraders. © Springer Science+Business Media Dordrecht 2013.

Biodegradation of chlorpyrifos was studied in mineral medium and soil with a novel fungal strain JAS1 isolated from a paddy field soil. The molecular characterization based on 18S rRNA sequence homology confirmed its identity as Aspergillus terreus. The 300-mg L⁻¹ chlorpyrifos and its major metabolite 3,5,6-trichloro-2-pyridinol (TCP) were completely degraded within 24 h of incubation in the mineral medium. In soil enriched with chlorpyrifos and nutrients (carbon, nitrogen, and phosphorous), A. terreus JAS1 was able to degrade chlorpyrifos and its metabolite TCP (300 mg kg⁻¹ soil) in 24 and 48 h, respectively. The soil was spiked with chlorpyrifos (300 mg kg⁻¹ soil) devoid of nutrients and the fungal strain was capable of degrading both chlorpyrifos and TCP in 24 and 48 h, respectively. The course of the degradation process was studied using high-performance liquid chromatography and Fourier transform infrared analyses. These results showed that the chlorpyrifos-degrading fungal strain had the potential to degrade the pesticide-contaminated agricultural soils even without addition of nutrients.

The use of peracetic acid (PAA) in the disinfection of sanitary effluents has been proposed by various authors. However, there are still doubts about its influence on the physical-chemical characteristics of the effluent after application. In the present study, it was observed that the composition of PAA leads to an increase in organic material, resulting in an increase of approximately 20 mg/L in the chemical oxygen demand of the effluent for every 10 mg/L of PAA applied. According to the kinetic tests, the degradation of PAA in the effluent was represented by a first-order reaction and its half-life in the effluent was estimated at 79 min. The formation of by-products resulting from degradation of PAA in the effluent was evaluated by considering by-products already detected by other authors in disinfection trials, these being nonanal, decanal, chlorophenols, and 1-methoxy-4-methylbenzene, which were not observed in the effluent being studied after application of PAA at a dosage of 10 mg/L. © 2013 Springer Science+Business Media Dordrecht.

The volatile monoterpene alpha-pinene has been measured in sediments of a selected area at "Carlos Anwandter" Nature Sanctuary, a Ramsar protected wetland located at the northwest of Valdivia City, south-central Chile. The ecosystem was seriously damaged by an uncontrolled liquid emission of a pulp mill (CELCO-Arauco) located about 15 km upstream of Rio Cruces during 2004. Exploratory data analysis was applied to analytical data collected from sediment samples, having found alpha-pinene as a reiterative chemical at relatively high concentrations in some specific areas of the wetland. The decrease of the total concentration of alpha-pinene in the area under study is coincident with a point contamination that occurred during 2004 (12,240 ng g(-1)) showing a decay in 2005 (7,890 ng g(-1)) and middle of 2006 (4,060 ng g(-1)). The following years, last 2006, 2008, and 2009, show a relatively constant concentration with a clear tendency toward baseline levels (2,460-2,640 ng g(-1)). Since the decrease of concentrations of alpha-pinene in sediments in the period 2004-2009 shows an opposite trend as compared to the surface area increase of pine and eucalyptus plantation in Region de Los Rios, and not having found potential sources of alpha-pinene by anthropogenic activities other than the pulp mill in the area under study, it may be finally concluded that this compound did not enter the bodies of water from a gradual and natural process; instead there is a base to sustain anthropogenic input. alpha-Pinene in sediments may be a plausible chemical tracer capable of detecting pollution events over time and its impacts in aquatic ecosystems as well as changes in aquatic ecosystems produced by improperly treated pulp mill liquid emissions that use pine and eucalyptus species.

The effectiveness of activated carbon sample (Carbonₑₓₚ) prepared by KOH chemical activation in hampering oligomerization of multicomponent adsorption was systematically examined. Anoxic (absence of molecular oxygen) and oxic (presence of molecular oxygen) adsorption isotherms of single-solute (2,4-dimethylphenol), binary solute (2-methylphenol/2,4-dimethylphenol), and ternary solute (phenol/2-methylphenol/2,4-dimethylphenol) were studied, using Carbonₑₓₚ and commercial granular activated carbon F400. Both binary solute adsorption and ternary solute adsorption on Carbonₑₓₚ indicated no impact of the presence of molecular oxygen on the adsorptive capacity. No significant differences between oxic and anoxic environment were noticed for any multicomponent adsorption systems, which indicated the effectiveness of Carbonₑₓₚ in hampering the oligomerization of phenolic compounds. On the other hand, in F400, which has lower microporosity and acidic functional groups, significant increases in the adsorptive capacity had been observed when molecular oxygen was present.

Heavy metals occur naturally in soil, at concentrations that depend on the parent material from which the soil was formed, the processes of formation, and the composition and the proportion of the components of its solid phase. Quantifying these concentrations is important for environmental studies of soil contamination and pollution, and choosing the methods for doing so is a key step in establishing heavy metal contents in soil samples. We evaluated two digestion methods (aqua regia and EPA 3051, both microwave oven-assisted) for assessing pseudo-total concentrations of Cd, Co, Cr, Cu, Ni, Pb and Zn in the surface layer (0–20 cm) of soil samples from the Brazilian agricultural frontier in the southwestern Amazon. Nineteen composite samples of the most representative soil classes for the states of Mato Grosso and Rondônia were collected under native vegetation undisturbed by human intervention. Canonical discriminant analysis and principal component analysis were used for multivariate exploration of the data. Aqua regia extracted higher amounts of Co, Ni, Pb, and Zn than EPA 3051, while levels of Cr and Cu did not differ between methods. In general, aqua regia recovered more of the metals when compared to reference soil samples.