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 congener-specific degradation pattern of polychlorinated biphenyls (PCBs) in Aroclor 1254 was investigated using a novel bacterial strain, Stenotrophomonas sp. JSG1, and it was accelerated by the surfactant, β-cyclodextrin. In addition, 4-chorobenzoic acid (CBA) degradation was also confirmed by the estimation of CBA depletion rate, microbial growth, and release of free chloride ion in mineral medium. Metal ions such as Ni²⁺, Hg²⁺ Ba²⁺, Cu²⁺, and NaCl (>4 %) were found greatly influencing the PCB degradation. However, Ca²⁺, Mg²⁺, Fe²⁺, and Mn²⁺ have not shown any impact on biodegradation. The bphC gene, which encodes an extradiol aromatic ring cleavage dioxygenase was successfully amplified and cloned. Phylogeny-based pairwise alignment of nucleotide sequences suggested that the cloned gene belongs to the extradiol dioxygenase family, but it showed high diversity to the traditional bphC gene. Results of the present investigation revealed that the Stenotrophomonas sp. JSG1 is an effective novel bacterium, which can be used in the PCB remediation studies.

This study examined the potential for regrowth of Escherichia coli in laboratory-incubated microcosms spiked with ultraviolet (UV)-disinfected sewage effluent and extracts derived from turfgrass or leaf litter. A second part of the study examined the potential of nutrients for predicting E. coli in two urban streams with point source effluent. Microcosms containing effluent and vegetation extracts were incubated for 72 h, samples were withdrawn over six time periods for measurement of E. coli. Streams were sampled every 2 weeks and E. coli and nutrients measured. E. coli counts in the microcosms exceeded the Texas state secondary contact recreation standard for surface water quality within 12 h for the turfgrass and within 18 h for leaf litter extracts. Univariate analysis of variance found that the interaction between vegetation extract source and concentration was more important than source of vegetation or concentration of extract alone. In the two streams sampled downstream of a point source effluent discharge, between 82 and 92 % of the variance in annual E. coli during high stream flow and between 55 and 57 % of the variance in annual E. coli during low stream flow was described by stream water-dissolved organic carbon (DOC) and dissolved organic nitrogen (DON), NH₄-N, NO₃-N, or PO₄-P. Once effluent is discharged to surface water, particularly during high flow conditions, DOC and DON derived from the landscape and nitrogen and PO₄-P derived from the effluent will provide ideal conditions for E. coli regrowth in surface waters downstream of the point source discharge.

Enzymatic precipitation provides a novel cost-effective and eco-friendly method for remediation of heavy metals from different industrial effluents such as tannery, electroplating, dye industries, and many more. This study has paid attention to bacterial alkaline phosphatase (BAP) from Eschericia coli C90 which catalyzes para-nitrophenyl phosphate (pNPP) and produces inorganic phosphate (Pi) that helps in the precipitation of heavy metals as metalphosphates. The kinetic behavior of BAP with pNPP in Tris-HCl was studied for pH regimes 8, 8.5, 9, 9.5, 10, 10.5, and 11 in detail. The results showed that the maximum activity of the enzyme was at pH 8.5 with an incubation period of 300 min at 37 C. Based on the kinetic data, experiments were performed at pH 8.5 and pH 10 to precipitate Cr3+, Cr6+, Cd2+, Ni2+, and Co2+ from single-ion solutions (250 and 1,000 ppm concentrations) as well as industrial effluents, and the amount of metal precipitated as metalphosphate was derived by determining the amount of metal reduced in the supernatant of the reactions employing atomic absorption spectrophotometer. The precipitation of metals from single-ion solutions at pH 8.5 for 300 min incubation period followed the order Cd2+ > Ni2+ > Cr3+ > Cr6+ > Co2+. In the experiments involving effluents from tannery and electroplating industries, precipitation of 35.1 % of Cr6+, 77.80 % of Ni 2+, and 57.42 % of Cd2+ was achieved from initial concentrations of 621, 97, and 122 ppm, respectively. © 2013 Springer Science+Business Media Dordrecht.

This paper discusses the effects of breakwaters on the Rimini coastal environment over the last half century. Sediment cores of 50 cm thick were collected in various seasons from 2002 to 2005 and were subsampled at surface and subsurface levels at 20 inshore and offshore stations in order to take account of various freshwater and wastewater inputs. A 240-cm sediment core was collected in the most impacted area in order to reconstruct the evolution of the marine ecosystem since the time of the breakwaters’ construction. Sediment grain size, physico-chemical parameters, nutrients and inorganic and organic contaminants were determined. The breakwaters have stopped coastal erosion but have given rise to a worsening of environmental quality. No impacts were detected outside the breakwaters. The integrated approach, using biogeochemical markers to reconstruct spatial and historical environmental trends within the sheltered area, proved to be very useful in highlighting its capacity for recovery and providing indications for coastal management.

Bottom slag and sewage sludge discharged from municipal solid waste incineration and sewage treatment plants were co-sintered for use as a cost-effective adsorbent for phosphate removal from aqueous solutions. The Langmuir isotherm model (which gives a better description of phosphate sorption than the Freundlich model) was adopted to describe the action of the synthesized adsorbent and also for phosphate sorption by either zeolite or ironstone. The model showed that the maximum sorption capacity of the synthesized adsorbent (27,030 mg kg-1) was 38.2 greater than for zeolite and 70.6 times greater than for ironstone. Desorption of phosphate from the synthesized adsorbent at different initial concentrations was about 4.98 %, which was several times lower than for zeolite. The phosphate removal capacity of the synthesized adsorbent remained constant for solution pH values ranging from 3 to 10, which was an improvement on the capacity of the other two adsorbents; its buffering capacity was also superior. The immobilization of phosphate on the synthesized adsorbent might be attributed mainly to complexation with Fe, Al, and Ca ions. Heavy metal ion concentrations in the leachate of the synthesized adsorbent were negligible. © 2013 Springer Science+Business Media Dordrecht.