Effects of ethanol and nitrate on linear alkyl benzene sulfonate (LAS) degradation were investigated using central composite design. At experimental design, removal of 99.9% was observed in batch reactors (1 L) with 9.8 to 41.2 mg L⁻¹ of LAS. The batch reactors were kept under agitation at 120 rpm and 30 °C. Ethanol (co-substrate) and nitrate (electron acceptor) were statistically significant factors (p < 0.05) in surfactant removal. Optimal values were 97.5 and 88 mg L⁻¹ for ethanol and nitrate, respectively. LAS removal was kinetically investigated by varying surfactant concentration while using optimal values. Batch I (27 mg L⁻¹ LAS) exhibited greater degradation rate (KᴸᴬS) (0.054 h⁻¹) in the presence of ethanol and nitrate. Nonetheless, in Batch II (60 mg L⁻¹ LAS), the KᴸᴬS values decreased in those reactors probably due to inhibition by excess substrate for same concentrations of nitrate and ethanol added in reactors. As LAS concentration increased, the dominance of bacterial populations also increased, whereas diversity index decreased from 2.8 (inoculum) to 2.4 and 2.5 for reactors with both added nitrate and ethanol and those with only added ethanol, respectively. Probably, a selection of microbial populations occurred in relation to LAS concentration. The nitrate and ethanol, at able concentration, made it possible the induction of denitrifying microrganisms foward to LAS removal.

A novel quaternary nanocomposites consisting of Ag/AgCl decorated TiO₂ introduced on graphene oxide (GO) sheets with high loading of GO (50 wt.%) were prepared for photocatalytic application. The composite powders were synthesized by a facile sol–gel method utilizing polyvinylpyrrolidone (PVP) as a reducing agent to obtain Ag particles and a modified Hummers’ method to acquire GO sheets. The influence of reducing agent concentration and type of TiO₂ was investigated. The adsorption properties of the GO/TiO₂/Ag/AgCl nanocomposites were examined, and photocatalytic activity was investigated under UV light applying methylene blue (MB) as a model pollutant. The composites displayed great adsorption capability up to 112.6 mgg⁻¹ due to GO. It is shown that the GO/TiO₂/Ag/AgCl samples prepared by Degussa P25 TiO₂ and with a reduced amount of PVP have the best photocatalytic activity, reaching up to 55% decolorization of methylene blue under UV light. The photocatalytic activity is enhanced by approximately 80% with the addition of GO to the quaternary GO/TiO₂/Ag/AgCl composites.

Fungus Pleurotus ostreatus HAAS can tolerate and remove heavy metals from water. Among three heavy metals tested, the removal of Pb was the most efficient (99.9–100.0%), followed by Cd (45.9–61.1%), and Cr (29.4–64.5%). The uptake of heavy metals by the fungus varied and was dependent on the element. Pb was found to be transported primarily into the fungal cell wall (68.2–91.2% of the total), which was much higher than the insoluble form (20.1–32.7%), and the maximum intracellular concentration of Pb was found to be 119,830.4 mg kg⁻¹. In the cases of Cd and Cr, their insoluble forms were the main products of the reaction with the fungus, which accounted for 30.0–39.1 and 19.6–37.4% of the total. P. ostreatus HAAS produces oxalic acid, and this production is stimulated by Pb and Cr but inhibited by Cd. Parallel experimental results indicated that the concentration of the soluble metals in solution decreased with the increase of oxalic acid, which further suggested that oxalic acid played a partial role in the removal of the soluble heavy metals by chelation. These results revealed that this species of fungus has a variety of response mechanisms to the presence of heavy metals in solution.

Vanadium has the potential to be released as a by-product of the combustion of fossil fuels such as oil and coal in the aquatic system. Presence of tailing ponds and other mining operations may pose the largest threat to downstream users and to the long-term aquatic health of the Mackenzie River Basin (MRB, Canada). The need for developing a solid baseline for the MRB aquatic ecosystem against which future changes can be measured is urgent. In this study, 36 sets of triplicate diffusive gradients in thin films (DGT) samplers were deployed in MRB during the 2012–2014 ice-free seasons to investigate temporal and spatial changes in the concentration of DGT-labile vanadium (V) as part of a Northwest Territories community-based project. Average DGT-labile V concentration (5.9 ± 0.9 nmol L⁻¹) was comparable with non-contaminated aquatic systems, suggesting no significant impact of human activities on V speciation in MRB in 2012–2014. The V concentrations reported in this study constitutes a baseline that can be used to enhance ongoing monitoring efforts. Although the DGT samplers were deployed in collaboration with northern communities, the absence of temporal changes in DGT-labile V indicated that in situ DGT passive samplers constitute a reliable and robust alternative for community-based monitoring programs. Excitation emission matrix (EEM) fluorescence combined with parallel factor analysis (PARAFAC) validated three humic-like (C1–C3) and one protein-like (C4) fluorescent component. However, no significant relationships were apparent between DGT-labile V and dissolved organic carbon (DOC), the PARAFAC loadings, and composition (p > 0.05). Hierarchical cluster analysis revealed that DGT-labile V concentration was negatively correlated with aromatic and humified DOM (r = − 0.70 to − 0.84, p < 0.05).

Acid deposition and temperature variation could lead to changes of physiological characteristics of plants in response to stress. In this paper, Medicago sativa CV. Dongmu–1 was investigated to test the effects of freeze-thaw circle and acid deposition upon the changes of osmotic adjustment substances, biological membrane permeability, and antioxidant enzymes. The experiment was conducted under laboratory conditions, and the seedlings were divided into four groups (group I: no treatment, group II: acid stressed only, group III: freeze-thaw stressed only, group IV: both freeze-thaw and acid stressed). Results indicated that under freeze-thaw circle and acid deposition, the contents of malondialdehyde (MDA) and proline increased respectively by 0.6~203.4 and 19.3~68.8% when compared with group I, while protein content declined by 4.1~31.7%, and the effects were even significant than freeze-thaw-only stressed groups. In the freeze-thaw process, superoxide dismutase (SOD) activity dropped at first and then increased with the increase of temperature, peaking at − 3 °C by 1118.45 U g⁻¹; peroxidase (POD) activity showed a brief rise and declined rapidly below 0 °C. By increasing the potentials of antioxidant enzymes and MDA, the membrane lipid peroxidation inside alfalfa was prevented; meanwhile, several indexes changed adaptively in resisting hurts. Variation of SOD and POD was induced by the defense mechanism, which showed alfalfa’s satisfactory cold resistance and acid tolerance. Further research on acid deposition and freeze-thaw circle would be beneficial for the global cultivation of forage grass.

In this study, five different fillers: coal ash, fiber-ball, polypropylene, ceramic, and polyhedron empty ball were used for cultivating nitrifying bacteria by increasing influent ammonia concentration gradually in sequencing batch reactors (SBRs). The results of ammonia removal performance showed that the reactor with coal ash has the highest NH₄⁺-N removal rate all the time. The ammonia removal rate of it averagely reached ≥ 95% under the condition of hydraulic retention time (HRT), dissolved oxygen (DO), pH was 12 h, 4.5 ± 0.5 mg/L, 7.5–8.5, respectively, even when the ammonia nitrogen loading reached 1000 mg/L. MiSeq Highthrough sequence was used for analyzing microbial community. The results revealed that obvious variation have occurred among the reactors after 48 days of operation; however, Nitrosomonas was enriched in large amount and became the dominant genus except in the reactor with polypropylene. Compared with other carriers, coal ash can enrich more nitrifying bacteria, the cell biomass of Nitrosomonas increased from 12.25 to 384.18 mg/L, which was 5.5 times more than the negative control. The use of coal ash as filler realizes the enrichment of a large amount of nitrifying bacteria in a short period, which guarantees a highly efficient nitrification.

It is now acknowledged that aromatic hydrocarbons present in contaminated soils occur in mixtures. The effect of single, binary and quinary mixtures of phenanthrene and selected nitrogen-containing polycyclic aromatic hydrocarbons (N-PAHs) were investigated on the survival, growth and behavioural index of earthworms (Eisenia fetida) over a 21-day incubation in soil. The results showed that the LC₅₀ values ranged from (not detected) ND–329.3 mg kg⁻¹ (single mixture), ND–219.8 mg kg⁻¹ (binary mixtures) to 148.4 mg kg⁻¹ (quinary mixture), while the EC₅₀ values (based on weight loss) ranged from 13.3–148.4 mg kg⁻¹ (single mixture), 63.8–148.4 mg kg⁻¹ (binary mixture) to 24.2 mg kg⁻¹ (quinary mixture). Greater impacts were recorded where N-PAHs are present with phenanthrene. Further, behavioural index of E. fetida was affected after 24-h exposure to N-PAH-amended soils. Among the N-PAHs however, benzo[h]quinoline recorded the greatest impact on the survival, growth and behavioural index of E. fetida in soil. Findings from this study showed that three ring-N-PAHs are more toxic than phenanthrene as expected from their physico-chemical properties. The binary and quinary mixtures of phenanthrene and N-PAHs in soil intensified toxicity, suggesting that PAHs-N-PAHs mixtures represent greater risk to soil biota.

This work is dedicated to study the potential application of char byproducts obtained in the gasification of rice husk (RG char) and rice husk blended with corn cob (RCG char) as removal agents of two emergent aquatic contaminants: tetracycline and caffeine. The chars presented high ash contents (59.5–81.5%), being their mineral content mainly composed of silicon (as silica) and potassium. The samples presented a strong basic character, which was related to its higher mineral oxides content. RCG char presented better textural properties with a higher apparent surface area (144 m² g⁻¹) and higher micropore content (V ₘᵢcᵣₒ = 0.05 cm³ g⁻¹). The alkaline character of both chars promoted high ecotoxicity levels on their aqueous eluates; however, the ecotoxic behaviour was eliminated after pH correction. Adsorption experiments showed that RG char presented higher uptake capacity for both tetracycline (12.9 mg g⁻¹) and caffeine (8.0 mg g⁻¹), indicating that textural properties did not play a major role in the adsorption process. For tetracycline, the underlying adsorption mechanism was complexation or ion exchange reactions with the mineral elements of chars. The higher affinity of RG char to caffeine was associated with the higher alkaline character presented by this char.

Elevated bacteria concentrations have led to the impairment (e.g., closures of shellfisheries and recreational beaches) of coastal waters. Although many previous studies have suggested that wastewater inputs can lead to elevated fecal indicator bacteria (FIB) concentrations in surface waters, few studies have quantified wastewater-associated FIB exports at the watershed scale. The goal of this study was to estimate bacterial exports at the watershed scale based on wastewater management approach (septic vs. sewer). Six watersheds (three exclusively on septic and three exclusively served by a sewer system) were selected for water quality assessment and comparison. Streams were monitored approximately monthly from August 2011 to June 2012 during baseflow conditions. Additionally, three storms were monitored. Samples were collected in sterile 100-mL bottles and analyzed for Escherichia coli concentrations. Discharge from streams was measured and bacterial exports were estimated by multiplying discharge by E. coli concentration. The results revealed that (1) during baseflow conditions, septic watersheds contained elevated stream discharge and E. coli concentrations and exports as compared to sewer watersheds; (2) warmer months had elevated E. coli watershed exports compared to colder months in both septic and sewer watersheds; and (3) storms significantly increased watershed E. coli exports in both septic and sewer watersheds. Storms significantly increased watershed E. coli exports in both septic and sewered watersheds, but E. coli counts in sewered watersheds were considerably greater likely due to greater impervious surface coverage and or leaky sewer infrastructure. These findings in conjunction with previous studies suggest that septic systems may play a pivotal role in the delivery of FIB to receiving waters, particularly during baseflow conditions.

Pyrene is a dominant PAH in urban environments. It can combine with airborne particulates and accumulate on plant leaves. To investigate pyrene’s biodegradation potential, this study initially monitored the abundance of airborne and phyllosphere bacteria. The number of airborne pyrene-degrading bacteria ranged from 22 to 152 CFU m⁻³ air, and more bacteria were found in the proximity of the ornamental plant swath than along the roadside. Pyrene-degrading bacteria averaged 5 × 10⁴ CFU g⁻¹ on the leaves of all tested plant species and accounted for approximately 7% of the total population. Four pyrene-degrading bacteria were isolated from I. coccinea to use as model phyllosphere bacteria. To increase the bioavailability of pyrene, a lipopeptide biosurfactant was applied. Kocuria sp. IC3 showed the highest pyrene degradation in the medium containing biosurfactant. The removal of deposited pyrene at 30 μg g⁻¹ leaf was monitored in a glass chamber containing I. coccinea twigs. After 14 days, leaves containing both Kocuria sp. IC3 and 0.1× CMC biosurfactant showed 100% pyrene removal with the most abundant bacteria. The system with biosurfactant alone also enhanced the activities of phyllosphere bacteria with 94% pyrene removal. Consequently, the bioremediation of deposited pyrene could be achieved by spraying biosurfactant on ornamental shrubs.