We highlighted some of the key problems associated with the use of beneficial microorganisms for improving adaptation of plants to soils, polluted with heavy metals (HMs), especially Cd. Inoculation of pea line SGE and its Cd-tolerant mutant SGECdᵗ with nodule bacteria Rhizobium leguminosarum bv. viciae demonstrated that nodulation process may be disturbed at Cd concentrations below threshold toxicity levels for each partner and the plant genotype plays a major role in nodulation under Cd stress. A comparative mathematical analysis of available information about Cd tolerance, accumulation of HMs (Cd, Cr, Cu, Ni, Pb, Sr and Zn), response to mycorrhizal fungus Glomus sp. and 15 phenotypic traits of 99 pea varieties revealed that (1) the Cd-sensitive varieties were more efficient in exploring the protective potential of symbiosis to compensate their deficit in Cd tolerance and (2) correlations between the studied traits exist and can be helpful for selection of plant-microbe systems adapted to polluted soils. In pot experiment with 11 varieties of Indian mustard, the plant growth-promoting effect of rhizobacterium Variovorax paradoxus 5C-2 negatively correlated with Cd tolerance and shoot Cd concentration of the plants grown in Cd-supplemented soil. In an outdoor pot experiment, inoculation of willow with the ectomycorrhizal fungus Pisolithus tinctorius and a cocktail of rhizobacteria stimulated root exudation, decreased soil pH and increased Cd mobilization in soil and Cd uptake by plants, but decreased plant growth at a moderate contamination level (25 mg Cd kg⁻¹). Opposite effects were observed in highly contaminated soil (77 mg Cd kg⁻¹). We propose a preliminary systematic framework of interactions between these factors that determine the success of microbial inoculation aimed at improving crop performance on HM-polluted soils or enhancing phytoremediation.

This work describes the experimental determination of the major degradation and sorption parameters of polycyclic aromatic hydrocarbons (PAHs) in a sensitive marine environment, the Northern Adriatic Sea (Mediterranean Sea). The persistence and sorption of complex PAH mixtures were analysed in the laboratory in conditions mimicking open-sea and coastal sediments, which differ in grain size and organic carbon content and are characterized by different oceanographic conditions including abiotic influences. The study investigated how sediment type and texture and salinity, temperature and solar irradiation conditions affect the partitioning of low molecular weight (LMW) and high molecular weight (HMW) PAHs into aqueous and solid phase, which critically influence their behaviour. With regard to the change from offshore to coastal conditions, HMW PAHs were found to be more sensitive to the increased salinity (from 21 to < 37 parts per thousand), whereas LMW PHAs were more sensitive to the temperature increase (from 11 to 22 °C). HMW PAHs were more affected by sediment type changes in terms of distribution coefficient (K d). Since the physicochemical properties of organic pollutants affect their distribution, transport, bioavailability and toxicity, analysing the accumulation and persistence of dissolved pollutants can provide useful information for environmental risk assessment and management.

Nutrient enrichment is considered one of the most important causes for summer hypoxic conditions in the northern Gulf of Mexico (NGOM) off the Louisiana coast. While many studies on nutrient inputs from the large Mississippi-Atchafalaya River System have been conducted, little is known about nutrient inputs from other coastal rivers in Louisiana. In this study, we utilized long-term (1980–2009) records on river discharge and nutrient concentrations of four major Louisiana coastal rivers—the Sabine, Calcasieu, Mermentau, and Vermilion—to estimate daily, monthly, and annual inflows of nitrate and nitrite nitrogen (NO₃ + NO₂), total Kjeldahl nitrogen (TKN), and total phosphorus (TP) into the NGOM. The three-decade-long nutrient inflows from these rivers were analyzed for their seasonal fluctuations, interannual variabilities, and decadal trends. Fluxes of NO₃ + NO₂, TKN, and TP for these river basins were estimated to assess land use effects on riverine nutrients. Our study found that the four coastal rivers discharged each year a considerably large amount of NO₃ + NO₂ (total of 1755 t), TKN (12,208 t), and TP (1833 t) into the NGOM, with a peak input of nitrogen during the spring. The Mermentau and Vermilion Rivers, which drain intensive agriculture areas, had significantly higher NO₃ + NO₂, TKN, and TP concentrations when compared with the Sabine and Calcasieu Rivers, which drain forest-pasture-dominated lands. The fluxes of NO₃ + NO₂, TKN, and TP from the Mermentau River Basin (156 kg km⁻² year⁻¹ NO₃ + NO₂, 942 kg km⁻² year⁻¹ TKN, and 206 kg km⁻² year⁻¹ TP) and the Vermilion River Basin (374, 1078, and 360) were much higher than those combined from the Sabine and Calcasieu River Basins (66, 710, and 62). These findings fill a major knowledge gap concerning the quantity and characteristics of nitrogen and phosphorus transport from coastal watersheds to North America’s largest hypoxic zone.

Dense nonaqueous-phase liquids (DNAPLs) spilled on the soil migrate vertically depending upon gravity and capillary forces through the unsaturated zone of the porous aquifer, forming a vapour plume. These volatile organic compounds (VOCs) can be transferred by advection-diffusion to the groundwater or to the atmosphere. Evaluating DNAPL vapour fluxes at the soil-air interface is one of the key challenges in the remediation of contaminated sites. This work discusses the results of a large-scale vapour plume experiment with a well-defined trichloroethylene (TCE) spill, including a sequential raising and lowering of the water table, where the TCE vapour fluxes at the soil surface were experimentally quantified in two ways: (i) directly, with measurements at the soil-air interface using different flux chambers at various operational modes under both transient and steady-state conditions of the vapour plume, and (ii) indirectly, using a quasi-analytical approach based on soil gas measurements. It was shown that upward displacement of the water-air front during the controlled raising of the water table (approximately 10 cm h⁻¹) increased the TCE vapour flux measured at the soil surface by factors of 4 to 10. Under steady-state transport conditions, TCE vapour fluxes measured using five types of flux chambers and three operational modes were similar. The effects of the flux chamber geometry, the accumulation of TCE vapours in the chamber headspace or the air recirculation at a low flow rate on the measured TCE vapour fluxes were low. At steady-state transport conditions, TCE vapour fluxes measured with the flux chambers and estimated using the quasi-analytical approach were of the same order of magnitude. However, under transient conditions of the vapour plume, the TCE vapour flux predicted by the quasi-analytical approach greatly underestimated or overestimated the real TCE vapour flux at the soil-air interface.

The cyanobacterial bloom in water has adversely affected water quality, local economies, and human health. Therefore, the removal and restricting the growth of harmful algae are of particular interest. In this study, ZnO–montmorillonite that could flocculate and restrict the growth of Microcystis aeruginosa, used as a probe of cyanobacterial, was prepared by hydrothermal solution intercalation method and characterized by means of XRD, IR, and TEM. In ZnO–montmorillonite, ZnO nanoparticles were either embedded in the interlayer space of montmorillonite or dispersed on montmorillonite surface. The determinations of chlorophyll a levels, total soluble protein content, and malondialdehyde concentration demonstrated that ZnO–montmorillonite had stronger flocculation effect on M. aeruginosa compared with natural montmorillonite and ZnO under visible light and had a better photocatalytic degradation effect on M. aeruginosa than ZnO under UV irradiation after 1 h. Under UV, 95 % removal efficiency was achieved for M. aeruginosa in 1 h using 50 mg L⁻¹ZnO–montmorillonite, and the proliferation of M. aeruginosa was totally inhibited due to the high photocatalytic activity and absorption flocculation ability of ZnO–montmorillonite. Furthermore, the cell structure was irreversibly damaged and the cell lysed. The synergy of absorption flocculation and photocatalysis of ZnO–montmorillonite promoted the removal of M. aeruginosa.

Metalaxyl, an important phenylamide fungicide, is widely used for controlling fungal diseases caused by pathogens of the orders Peronosporales and Pythiales. Under laboratory conditions, metalaxyl was applied to soil samples at the recommended field rate (1×FR) and double of recommended field rate (2×FR) for two and three times. Soil subsamples were taken at 0, 1, 3, 7, 14, 28, and 45 days after the last application of metalaxyl for determination of metalaxyl residues and 7, 14, 28, and 56 days for enumeration of cultivable microorganisms and DGGE profile of soil microbial community. Soil incubation experiments revealed that metalaxyl was degraded faster in the third application than in the second application of the fungicide, half-lives of metalaxyl decreasing from 16.2 to 9.9 days for recommended field rate and 22.1 to 20.0 days for double of recommended field rate. Soil bacterial and fungal populations decreased in the first 14 days and then recovered to the control levels; population of actinomycetes did not alter in the first 28 days but increased at the end of the experiment after the second application. However, after the third treatment, temporary increase in soil bacteria population, nonsignificant inhibition effect on fungal population, and obvious stimulation effect on actinomycetes number were observed. DGGE results showed that successive inputs of metalaxyl altered the bacterial community structure. There were differences in the persistence and effects of metalaxyl on microbial community between the second and the third metalaxyl treatments.

A simple, cost-effective, and efficient pretreatment method, namely, vortex- and shaker-assisted liquid–liquid microextraction (VSA-LLME) coupled with gas chromatography and mass spectrometry (GC-MS), is developed for determining 16 trace-level polycyclic aromatic hydrocarbons (PAHs) in offshore produced water. The parameters affecting the VSA-LLME performance including solvent volume, ion strength, shaking time, and centrifuge speed were optimized. Under the optimized condition, the enrichment factors range between 68 and 78. The method linearities (R ²) for all 16 PAHs were above 0.99 at concentration range between 10 and 200 ng/L. The recoveries of the method were 74–85 %, and the limits of detection were as low as 2 to 5 ng/L. The relative standard deviations (RSD%) were 6~11 %. The developed method was also validated in industrial wastewater sample and showed good capability in determination of 16 PAHs in offshore produced water. The developed method offers advantages including simplicity of operation, low cast, and high sensitivity.

Peatlands serve as important stores of organic matter and regulators of nutrient and metal export to surface waters, yet relatively little is known regarding the impact of more than a century of metal, sulfur, and acid deposition on microbial activity in acidic, nutrient-poor peatlands that are common features around Sudbury, Ontario. In this study, eight peatlands were selected at varying distances from the Copper Cliff Smelter that was once the largest point source of sulfur dioxide and sampled for analysis of nutrient and metal content. Basal microbial respiration, relative response to substrate addition (four synthetic and four natural substrates) assessed as CO₂production rates and microbial biomass were assessed in surface (0–10 cm) peat samples. Bacterial and fungal communities within the peat samples were profiled using terminal restriction fragment length polymorphism analysis. Basal respiration (i.e., carbon mineralization in absence of substrate addition) was lowest and Cu and Ni concentrations and the degree of humification (assessed by the von Post scale) in surface peat samples were highest close to the smelter. Each peatland had a unique bacterial community when assessed using non-metric multidimensional scaling, whereas the fungal community was variable with no consistent patterns across the sites. Despite differences in microbial communities, substrate-induced respiration rates did not differ among peatlands as sites generally responded similarly to carbon substrate additions. Basal respiration rates were related to the humification status of the peat, which was potentially related to environmental degradation in the peatlands or surrounding terrestrial systems closer to the Sudbury smelters.

The diversity and spatial structure of soil fungi (SF) and arbuscular mycorrhizal fungi (AMF) communities in the southern taiga forest litter were studied in sites with two contrasting contamination levels with copper smelter emissions. The operational taxonomic unit richness and evenness in the communities of both target groups decreased under contamination. The community structure of contaminated and control areas differed for SF, whereas they were similar for AMF. According to spatial structure analysis results on a scale of tens of meters, a gradual change of composition with distance was revealed for the SF community within 30-m intervals in the control sites. No spatial autocorrelation was found for AMF in the control sites. However, pronounced patchiness was characteristic of both SF and AMF communities within 10 m of contaminated sites. In the contaminated area, no specific spatial structure determinants of the studied communities was found among environmental factors such as water content, heavy metal concentrations in the forest litter, sample plot localization relative to canopy density, and herb vegetation diversity and abundance. However, in the control sites, AMF richness depended on herb abundance and litter chemistry.

Accumulations of mass loads of selected chemicals in roadside snowbanks were studied at five sites with various traffic densities in the city of Trondheim (Norway) by collecting snow samples throughout the winter period and analyzing them for 13 water quality constituents: pH, electrical conductivity (EC), alkalinity, Cl, Na, total suspended solids (TSS), Cd, Cr, Cu. Ni, Pb, W, and Zn. The resulting dataset was then supplemented by similar data collected earlier in the city of Luleå (Sweden). Regression analyses for individual sites indicated linear trends in unit-area constituent accumulations with time (0.65 < R ² < 0.95) and supported the assumption of linearity in further analyses. Principal component analysis (PCA) of the combined Luleå/Trondheim data revealed cause-effect relationships between the chemical mass loadings (TSS and trace metals) and three predictors: snow age (snow residence time (SRT)), traffic density (annual average density of traffic (AADT), and cumulative traffic volume (CTV = SRT × AADT). Cl and Na loads, originating from road salt applications in Trondheim only, did not display this trend. Two types of parsimonious models for predicting trace metal accumulations in winter-long roadside snowbanks were developed: (a) a linear regression model using CTV as a single predictor and predicting metal accumulations with a moderate certainty (0.37 < R ² < 0.66) and (b) multiple regression models using SRT, AADT, and snow water equivalent (SWE) as predictors. The latter models indicated good correlations between the mass loads and the predictors (0.64 < R ² < 0.77) and produced slightly better prediction accuracies (0.44 < R ² < 0.67) than the simpler model.