In this study, various metal concentrations were determined in environmental samples from rivers in the vicinity of mining areas of the Northwest Province, South Africa. These metal concentrations were also determined in various crustacean organs viz., hepatopancreas, flesh and muscle of the freshwater crab, Potamonautes warreni. The highest metal concentrations obtained in the freshwater samples were Ni (0.022 mg/l), Pb (0.02 mg/l), Cu (0.011 mg/l), Cd (0.009 mg/l), Pt (0.017 μg/l), Pd (0.011 μg/l) and Rh (0.008 μg/l). The highest metal concentrations obtained in the sediment samples were Ni (85.1 mg/kg dry weight (d.wt)), Pb (25.4 mg/kg d.wt), Cu (75.5 mg/kg d.wt), Cd (64.9 mg/kg d.wt), Pt (0.38 ng/g d.wt), Pd (0.74 ng/g d.wt) and Rh (0.23 ng/g d.wt). The results obtained for the bioavailability studies of all the metals investigated in the sediment have revealed no definite patterns for the fractionation results of the metal concentrations. In the case of the crab samples collected in the Elands River, the Pb, Cd, Pt, Pd and Rh concentrations indicate that the mining activities may have had an influence in the uptake of these metals in the crab samples analysed. In the case of the Hex River, the Ni, Cu, Pb, Cd, Pd and Rh concentrations in the crab samples may be attributed to mining activities. The bioaccumulation results indicated that the Ni and Cu concentrations show partly bioaccumulation in the tissues of the crab samples evaluated. For the Pd, Cd, Pt, Pd and Rh concentrations evaluated, definite signs of bioaccumulation were found.

With the gradual depletion of high-grade copper ore deposits, secondary wastes are gaining importance as a source for metal recovery. However, the alkalinity and low copper concentration in some of these resources underscore the need for selective leaching agents. In this work, indigenous alkaliphiles from a fly ash landfill site with inherent pH tolerance, metal tolerance and copper leaching capability were isolated and investigated. Four isolates, namely Agromyces aurantiacus TRTYP3, Alkalibacterium pelagium TRTYP5, Alkalibacterium sp. TRTYP6 and Bacillus foraminis TRTYP17, each selectively leached about 50 % copper from 1 % (w/v) of fly ash. Mixed culture of these bacteria resulted in higher leaching of copper. The optimal combination was TRTYP3, TRTYP5, TRTYP6 and TRTYP17 in the ratio 1:1:3:1, which leached 88, 81, 78, 76, 70 and 55 % Cu from 1, 2.5, 5, 10, 15 and 20 % (w/v) of fly ash. While Cu and Pb were bioleached into solution, Fe and Zn were precipitated.

The application of biochar as a sustainable material in biofilters to remove volatile compounds from the air provides a lot of advantages in relation to equipment maintenance and efficiency and ensures a zero-emission process. This work has analysed the morphology of biochar produced from birch and pine at different temperatures, its pore structure and changes depending on the type of pollutant and microorganisms used in biofiltrating media. Biochar morphology was investigated by scanning electron microscopy, while biochar pore structure was analysed by mercury intrusion porosimetry and nitrogen absorption at 77 K. Performed tests have shown that the biggest surface area of pores is in the biochar from pine that underwent thermal treatment at 750 °C. It has been determined that the pore volume of pine biochar decreases when acetone, xylene and ammonia pollutants are being removed from air during biofiltration. The biggest changes occurred in the pores with a diameter of 2–20 μm. Meanwhile, after the treatment with the studied volatile compounds, the surface area of pine biochar mesopores with a diameter smaller than 0.05 μm increased.

Sorption is commonly agreed to be the major process underlying the transport and fate of polycyclic aromatic hydrocarbons (PAHs) in soils. However, there is still a scarcity of studies focusing on spatial variability at the field scale in particular. In order to investigate the variation in the field of phenanthrene sorption, bulk topsoil samples were taken in a 15 × 15-m grid from the plough layer in two sandy loam fields with different texture and organic carbon (OC) contents (140 samples in total). Batch experiments were performed using the adsorption method. Values for the partition coefficient Kd(L kg⁻¹) and the organic carbon partition coefficient KOC(L kg⁻¹) agreed with the most frequently used models for PAH partitioning, as OC revealed a higher affinity for sorption. More complex models using different OC compartments, such as non-complexed organic carbon (NCOC) and complexed organic carbon (COC) separately, performed better than single KOCmodels, particularly for a subset including samples with Dexter n < 10 and OC <0.04 kg kg⁻¹. The selected threshold revealed that KOC-based models proved to be applicable for more organic fields, while two-component models proved to be more accurate for the prediction of Kdand retardation factor (R) for less organic soils. Moreover, OC did not fully reflect the changes in phenanthrene retardation in the field with lower OC content (Faardrup). Bulk density and available water content influenced the phenanthrene transport mechanism phenomenon.

Henry’s law constant is an essential parameter for the estimation of the environmental prevalence of pollutants. Here, we present two improved methods for measuring Henry’s law constant deploying inert gas stripping (IGS). The methods are targeted at compounds with high gamma coefficients (activity coefficient at infinite dilution) corresponding to large infinite dilution coefficients, such as monoterpenes and sesquiterpenes. We deploy a highly sensitive PTR-MS (proton transfer reaction-mass spectrometer) (low limit of detection, wide linear range, split-second time resolution) as detector. We use suited off-equilibrium conditions to extrapolate to equilibrium conditions. The first method is based on the observed linear correlation between gas flow and off-equilibrium experimental Henry’s law constant value. The second method is based on the linear dependence of the gas holdup on volumetric flow. We report HLC constants for six monoterpenes, isoprene and even, as a proof of concept, the sesquiterpene farnesene. The new methods allow for measuring HLC of nearly insoluble compounds at a new accuracy and precision.

Leachate from unlined or leaky landfills can create groundwater contaminant plumes that last decades to centuries. Understanding the dynamics of leachate movement in space and time is essential for monitoring, planning and management, and assessment of risk to groundwater and surface-water resources. Over a 23.4-year period (1986–2010), the spatial extent of the Norman Landfill leachate plume increased at a rate of 7800 m²/year and expanded by 878 %, from an area of 20,800 m²in 1986 to 203,400 m²in 2010. A linear plume velocity of 40.2 m/year was calculated that compared favorably to a groundwater-seepage velocity of 55.2 m/year. Plume-scale hydraulic conductivity values representative of actual hydrogeological conditions in the alluvium ranged from 7.0 × 10⁻⁵to 7.5 × 10⁻⁴ m/s, with a median of 2.0 × 10⁻⁴ m/s. Analyses of field-measured and calculated plume-scale hydraulic conductivity distributions indicate that the upper percentiles of field-measured values should be considered to assess rates of plume-scale migration, spreading, and biodegradation. A pattern of increasing Cl⁻concentrations during dry periods and decreasing Cl⁻concentrations during wet periods was observed in groundwater beneath the landfill. The opposite occurred in groundwater downgradient from the landfill; that is, Cl⁻concentrations in groundwater downgradient from the landfill decreased during dry periods and increased during wet periods. This pattern of changing Cl⁻concentrations in response to wet and dry periods indicates that the landfill retains or absorbs leachate during dry periods and produces lower concentrated leachate downgradient. During wet periods, the landfill receives more recharge which dilutes leachate in the landfill but increases leachate migration from the landfill and produces a more concentrated contaminant plume. This approach of quantifying plume expansion, migration, and concentration during variable hydrologic conditions provides increased understanding of plume behavior and migration potential and may be applied at less monitored landfill sites to evaluate potential risks of contamination to downgradient receptors.

Featured with biodegradability and biocompatibility properties, gelatin (GE) was selected as the backbone to graft poly(acrylic acid) (PAA) to fabricate a granular hydrogel at room temperature in air. Using attapulgite (APT) as an inorganic component, the resulting GE-g-PAA/APT hydrogel was characterized by means of Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and zeta potential analysis and then used as the adsorbent to be applied in a mixed dye solution containing malachite green and orange G. The addition of APT can significantly reduce the swelling degree during the adsorption process, though its influences on the adsorption capacity are not so expectable. The as-prepared hydrogel shows a wide pH-independent adsorption from 3.0 to 10.0, with the maximum adsorption capacity of 1370 mg/g for GE-g-PAA and 1190 mg/g for GE-g-PAA/APT (5 wt%). More importantly, the as-prepared hydrogel shows high adsorption selectivity for cationic dyes and the dye-loaded hydrogel can be easily regenerated and recovered for successive adsorption cycles. Graphical Abstract Gelatin-based granular hydrogel for selective removal of MG in a mixed dyes containing MG and OG-G.

We analysed nutrients and basic ions (Na, Cl, K, Mg, Si, Ca, and SO₄) for a period of 1 year, including every precipitation event, and sampled stream water every 2 weeks from a forest catchment in Shimane Prefecture, Japan. Backward-trajectory analysis revealed that some air masses originated within Japan, but did not affect the precipitation chemistry. Air masses originating from northern China were positively correlated with nutrients and all basic ions. Concentrations of ammonium and dissolved organic nitrogen were much lower in stream water than in precipitation, while those of nitrate and particulate nitrogen were similar in stream water and precipitation. Unlike nitrogen, the dissolved phosphorus concentration was much higher in stream water than in precipitation. Both phosphate and dissolved organic phosphorus (DOP) levels were higher in stream water than in precipitation. Particulate phosphorus (PP) concentrations were very similar in precipitation and stream water. PP showed stronger correlations than potassium with suspended solids (SS) and flow rate, while phosphate and DOP were more strongly correlated with potassium than with SS or flow rate. Stream silica concentrations were not correlated with phosphate but did exhibit a significant negative correlation with DOP. Neither phosphate nor DOP was correlated with calcium. These results suggest that phosphorus is not leaching with silica or calcium as a paired cation, but rather with potassium in this area. Lower nitrogen concentrations in stream water than in precipitation can be attributed to an enhanced uptake of nitrogen by forest soils owing to the increased atmospheric deposition of phosphorus.

In this study, high-load compost leachate was successfully treated in a hybrid anaerobic baffled reactor (ABR)/electrocoagulation-flotation (ECF) system. The interaction effects of operational factors in ABR, i.e., influent chemical oxygen demand (COD), hydraulic retention time (HRT), and COD/nitrogen (N) ratio on the efficiency of COD removal and biogas production rate (BPR) were analyzed and correlated by response surface methodology (RSM). The optimum conditions of ABR were found at COD = 8250 mg/L, HRT = 46 h, COD/N ratio = 70, where COD removal and BPR reached 84 % and 76 mL/mg h, respectively. COD/N ratio and HRT were found to be the most effective parameters, respectively, on COD removal and BPR. The organic loading rate (OLR) values varied from 0.45 to 5.66 kg/m³ day. The data presented indicate that the ECF reactor successfully satisfies the discharge criteria for most of the experimental domain. The outcomes have exposed that sequential ABR/ECF reactors are a competent system in treating low- and high-strength compost leachate.

Inorganic N fertilizer and irrigation water types on the C and N dynamics are poorly understood. This work aimed to evaluate the effect of different N fertilizer and irrigation water types on soil C and N mineralization. The farmland experiment was conducted with three types of N fertilizer (urea, ammonium sulfate, and slow-release urea) and drip irrigation with two types of water (groundwater and reclaimed water) for a summer maize-winter wheat crop rotation. Soil samples were collected from the experimental farmland for incubation experiments. The results showed that the average cumulative mineralization of soil C (incubation 20 days) and N (incubation 14 weeks) in different treatments ranged from 73.50 to 91.37 mg kg⁻¹ and 52.65 to 64.04 mg kg⁻¹, respectively. N fertilization significantly increased dissolved organic carbon (DOC), dissolved organic nitrogen (DON), soil organic carbon (SOC), and soil organic nitrogen (SON) contents in the soils, but N fertilizer and irrigation water types had no significant influence on them. Correspondingly, N fertilization significantly enhanced the mineralization of C by 14.14–21.22 % and N by 15.81–22.16 % in soils but no significant difference among different N fertilizer types. Compared with groundwater, reclaimed water irrigation enhanced the mineralization of C by 3.33 % and N by 1.01 %, but the difference was not statistically significant. The cumulative mineralization of C and N in soils after DOM removal average significantly decreased 9.83 and 14.83 %, respectively, which indicates that DOM plays an important role in soil C and N mineralization. Our results indicate that inorganic N fertilization promotes soil C and N mineralization, which may inevitably aggravate global warning. Reclaimed water irrigation had similar influence on soil C and N mineralization as groundwater irrigation; thus, we recommend irrigation with reclaimed water in water shortage areas.