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.

Microplastics (MPs) in sediments from the complex lagoon-channel of Bizerte were investigated, for the first time, to evaluate the occurrence and abundance of MPs in Tunisia. After density separation in saline solution, MPs were counted by a stereomicroscope. The number of MPs was at the range of 3–18 items/g sediment (3000–18,000 items/kg dry sediment) and the most contaminated site was of Menzel Abderrahmane (MA) followed by Carrier Bay (CB), Menzel Jemil (MJ) and Channel of Bizerte (C). The MPs gathered during the survey varied in size from 0.3 to 5 mm, and appear in a variety of shapes and colours. The dominant shape was fibre (88.88% in MA, 91.00% in CB, 82.35% in C and 21.05% in MJ). The rest of MPs are fragments whilst no micro beads were found. Colours are clear, white, blue, green, red and black. Cities discharges, fishing activity and industrial production sites are the most likely sources of MPs. This first work provides original data on the presence of MPs that determines their bioavailability to organisms as seafood, and then possibly transfers of to human. The high MP concentrations registered in the complex lagoon-channel of Bizerte suggest that this site is a hotspot for MP pollution and there is an urgency to understand their origins and effects on marine life. The results will provide useful background information for further investigations.

In this study, a process has been proposed whereby the sulfide required for autotrophic denitrification is supplied by reducing the sulfate of influent water without the need to add an external sulfide source. The molar ratio of nitrate-to-sulfide was maintained at 1.6. The proposed system was operated continuously for 6 months, including two anoxic and anaerobic reactors with upward flow. The results indicate that the average amount of nitrate declined by 74%. The pH of 7–8 was more effective than a pH of 6 in removing the nitrate. As the hydraulic retention time was prolonged from 1.5 to 3 and was further prolonged to 5 h, the system efficiency was enhanced by removing the nitrate. An alkalinity consumption rate of 1.15 mg (as CaCO₃) per mg of removed NO₃ ⁻-N was achieved. In the effluent water, the increased sulfate was 6.7 mg per mg of removed NO⁻ ₃-N, while the hardness was diminished by 2.85 mg (as CaCO₃).

Cadmium and lead are some of several heavy metals that present a great concern for the environment because even in non-toxic concentrations for plants, their toxicity can affect animals and humans. Three different concentrations of sodium chloride solution were employed as pretreatment agents in order to increase the bioavailability of heavy metals and to analyze the interaction between heavy metals under saline soil conditions. The biomass production presented a remarkable increase for plants grown in soil pretreated with a 0.3 M NaCl solution, whereas the growth curve response of Arabidopsis thaliana in all samples showed a clear alteration compared with the control system. The conclusion was reached that saline solution pretreatment used in soil containing heavy metals produced an apparent stimulation of plant growth. In regards to the uptake of heavy metals by plants, lead and especially cadmium were the most favored metals by NaCl application.

Due to intensive agricultural activities to meet the growing needs for food, large volumes of water are consumed and an increasing amount of agrochemicals are released into the environment threatening the aquatic ecosystem. In order to ensure a sustainable agricultural management, it is crucial to develop an integrated water assessment plan that includes not only water quantity and quality but also toxicological assessments. The Pergamino River basin (province of Buenos Aires, Argentina) was selected as a representative case of study to monitor and assess the impact of both the long-term intensification of soybean production and fast-growing urban development on surface and groundwater sources. Physicochemical analyses and a Water Quality Index were determined and showed that water quality falls into the marginal category, compromising the irrigation purposes and threatening aquatic life. Glyphosate and aminomethylphosphonic acid were detected at least once in all sites. Caenorhabditis elegans toxic bioassays were performed and a toxicological ranking was developed. This analysis proved to be useful to detect toxicity even when water parameters met regulatory requirements and water quality seemed to be satisfactory. This research constitutes a valuable model to be replicated in other river basins that have been impacted by intensive agriculture and growing urban development in order to assess water quality conditions and ensure sound water resources management.

The sorption of three organic contaminants with different structure and polarity including non-polar phenanthrene (PHEN), 1,2,4,5-tetrachlorobenzene (TeCB), and polar 1,2-dichlorobenzene (DCB) onto original kaolinite, smectite, vermiculite, and fulvic acid (FA)/humic acid (HA)–clay complexes were investigated, and possible sorption mechanisms were inferred from sorption isotherms and characteristics of humic substances (HS) and HS–mineral complexes. Results showed smectite and vermiculite had stronger sorption ability than kaolinite, and the adsorbed amount of DCB was much higher than that of PHEN and TeCB on each clay. Due to FA/HA-facilitated hydrophobic interaction, FA/HA–clay complexes except FA–vermiculite complex showed a stronger affinity for PHEN and TeCB than the original clays, particularly for HA–clay complexes. The non-linearity parameter values of n for all the Freundlich sorption isotherms of DCB were greater than 1, indicating that clays possessed some unique sites with strong affinity and capacity to sorb DCB from aqueous solutions. FA/HA did not significantly affect the sorption of polar DCB on clays, implying sorption of DCB on clays was probably due to polar interactions between the polar group of DCB and clays. Cation-π bonding between PHEN and iron cation was directly evidenced by X-ray photoelectron spectroscopy, and FA impeded the sorption of PHEN on vermiculite by occupation of iron cation sites. This study will benefit understanding behaviors of contaminants in the soil environments.

Atrazine degradation in soil microbial fuel cells (MFCs) under different anode depths and initial concentrations is investigated for different redox soil conditions, and the microbial communities in the anode and different layers are evaluated. Atrazine degradation is fastest in the upper layer (aerobiotic), followed by the lower layer (anaerobic). A removal efficiency and a half-life of 91.69% and 40 days, respectively, are reported for an anode depth of 4 cm. The degradation rate is found to be dependent on current generation in the soil MFCs rather than on electrode spacing. Furthermore, the degradation rate is inhibited when the initial atrazine concentration is increased from 100 to 750 mg/kg. Meanwhile, the exoelectrogenic bacteria, Deltaproteobacteria and Geobacter, are enriched on the anode and the lower layer in the soil MFCs, while atrazine-degrading Pseudomonas is only observed in very low proportions. In particular, the relative abundances of Deltaproteobacteria and Geobacter are higher for lower initial atrazine concentrations. These results demonstrate that the mechanism of atrazine degradation in soil MFCs is dependent on bioelectrochemistry rather than on microbial degradation.

Biochar amendment can alter soil properties, for instance, the ability to adsorb and degrade different chemicals. However, ageing of the biochar, due to processes occurring in the soil over time, can influence such biochar-mediated effects. This study examined how biochar affected adsorption and degradation of two herbicides, glyphosate (N-(phosphonomethyl)-glycine) and diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea) in soil and how these effects were modulated by ageing of the biochar. One sandy and one clayey soil that had been freshly amended with a wood-based biochar (0, 1, 10, 20 and 30% w/w) were studied. An ageing experiment, in which the soil-biochar mixtures were aged for 3.5 months in the laboratory, was also performed. Adsorption and degradation were studied in these soil and soil-biochar mixtures, and compared to results from a soil historically enriched with charcoal. Biochar amendment increased the pH in both soils and increased the water-holding capacity of the sandy soil. Adsorption of diuron was enhanced by biochar amendment in both soils, while glyphosate adsorption was decreased in the sandy soil. Ageing of soil-biochar mixtures decreased adsorption of both herbicides in comparison with freshly biochar-amended soil. Herbicide degradation rates were not consistently affected by biochar amendment or ageing in any of the soils. However, glyphosate half-lives correlated with the Freundlich Kf values in the clayey soil, indicating that degradation was limited by availability there.

Bodies of water contaminated by cyanobacteria and their neuro- and hepatotoxins have caused environmental and public health issues all over the world. Therefore, determining safe concentrations in water for multiple uses to protect aquatic biota and identify forms of remediation are of broad interest. In this study, we isolated strains of the cyanobacteria Microcystis aeruginosa and Cylindrospermopsis raciborskii, which produce microcystin (MC) and saxitoxin (STX), respectively. Ecotoxicological tests using suspensions of lysed lyophilizated cells with concentrations of toxins equivalent to those permitted by legislation for potability (1 μg L⁻¹ for MC and 3 μg L⁻¹ for STX) did not result in significant mortality of the model organism, Ceriodaphnia dubia, where as concentrations five times greater resulted in decreased survival for both toxins. However, reproduction was significantly reduced even in the lower concentrations, indicating that the currently permitted standards are not safe for environmental protection. When cyanotoxins were treated with ultrasound, mortalities were no longer significant, independent of concentrations. Although reproduction was still lower in relation to the control, it was significantly higher when compared to the results obtained before ultrasound. Ultrasound has been previously applied to cyanobacteria cell lysis, but this is the first study to investigate the ecotoxicological effects of ultrasound on cyanotoxins. Using new test organisms and different times and potency of sonication will permit the development of more efficient techniques for the remediation of these toxins and the development of more adequate parameters for the protection of aquatic life.