Tributyltin (TBT) is a species of organotin compound (OTC), used as antifouling biocide in boat and ship paints to prevents the attachment of marine organism on their hull surfaces. Tributyltin was found to be very toxic to a variety of targeted and non-targeted organisms and has high persistence in sediments even after the total global ban by the International Maritime Organization (IMO) in 2008. Therefore, there is an urgent need to clean up TBT-polluted environments after the global banning due to the significant risks it poses to the human and aquatic organisms for its slow degradation rate. In selecting bioremediation agents, indigenous bacteria were documented to be of great potentials compared to non-indigenous. In this study, comparison was made between a bacterial isolate Klebsiella sp. FIRD 2, isolated from TBT-contaminated surface sediment and Pseudomonas specie isolated from non-TBT-contaminated soil. Previously, we isolated, screened, and identified Klebsiella sp. FIRD 2 as a TBT-resistant bacterium from TBT-contaminated surface sediment of Kong Kong Laut, Johor, Malaysia. The isolate was able to resist TBT up to 1500 μg/L without addition of carbon source in minimal salt medium (MSM). Pseudomonas sp., isolated from non-TBT-contaminated soil was tested in MSM treated with different concentration of TBT. The bacterium did not endure to survive in TBT-treated media without addition of carbon source; thus, the strain has no ability to utilize TBT as source carbon. Growth of Pseudomonas sp. was observed in MSM treated with TBT at concentration of 500 μg/L and 1000 μg/L along with addition of glucose as carbon source. No growth of Pseudomonas sp. was observed in MSM with higher TBT concentration even with additional of carbon source. This study equally endorses the potentials of indigenous bacteria in bioremediation of TBT contamination.

This study investigates the importance of the organic matter characteristics of several organic amendments (i.e., buffalo manure, food and kitchen waste, fruit and vegetables waste, and activated sewage sludge) and their influence in the bioremediation of a polycyclic aromatic hydrocarbons (PAH)-contaminated soil. The removal of low molecular weights (LMW) and high molecular weights (HMW) PAHs was monitored in four bioremediation reactors and used as an indicator of the role of organic amendments in contaminant removal. The total initial concentration of LMW PAHs was 234 mg kg⁻¹ soil (dry weight), while the amount for HMW PAHs was 422 mg kg⁻¹ soil (dry weight). Monitoring of operational parameters and chemical analysis was performed during 20 weeks. The concentrations of LMW PAH residues in soil were significantly lower in reactors that displayed a mesophilic phase, i.e., 11 and 15 %, compared to reactors that displayed a thermophilic phase, i.e., 29 and 31 %. Residual HMW PAHs were up to five times higher compared to residual LMW PAHs, depending on the reactor. This demonstrated that the amount of added organic matter and macronutrients such as nitrogen and phosphorus, the biochemical organic compound classes (mostly soluble fraction and proteins), and the operational temperature are important factors affecting the overall efficiency of bioremediation. On that basis, this study shows that characterization of biochemical families could contribute to a better understanding of the effects of organic amendments and clarify their different efficiency during a bioremediation process of PAH-contaminated soil.

Photolysis or photocatalysis may provide a process for mitigating ecological risks of naphthenic acids (NAs) contained in energy-derived waters such as refinery effluents and process waters. If effective, fixed-film TiO₂ photocatalysis of NAs could decrease operational expenses as well as capital costs for water treatment. The overall objective of this study was to measure rates and extents of photolysis and photocatalytic degradation of commercial NAs using bench-scale fixed-film TiO₂ and confirm changes in NA concentrations using sensitive vertebrate (fish = Pimephales promelas) and invertebrate (Daphnia magna) species. Specific objectives were to (1) measure rates and extents of degradation of commercial (Fluka) NAs throughout an 8-h duration of natural sunlight (“photolysis”) and natural sunlight in the presence of fixed-film TiO₂ (“photocatalysis”) and (2) measure changes in toxicity in terms of mortality with sentinel fish and microinvertebrate species. Bench-scale chambers using thin-film TiO₂ irradiated with natural sunlight were used to measure photocatalysis, and HPLC was used to quantify NAs. After 4 h in photocatalysis treatments, >92 % decline was observed with an average removal rate of 15.5 mg/L/h and half-life of 2 h. After 5 h of photocatalysis, there was no measurable NA toxicity for fish (P. promelas) or microinvertebrates (D. magna). Photocatalytic degradation achieved efficacious rates and extents of removal of Fluka NAs and eliminated acute toxicity to sentinel aquatic organisms, indicating the potential for application of this technology for mitigating ecological risks. Coupled with existing treatment processes (i.e., aerobic biodegradation), photocatalysis can augment rates and extents of NA removal from impacted waters.

Compost or composting has been widely investigated under the background of heavy metal pollution of agricultural soils and rapid growth of organic wastes. Compost is rich in nutrients, humic matter, and microorganisms; it may be added to agricultural soil as a fertilizer to improve soil fertility and promote the growth of crops and microorganisms, and as a soil amendment to relieve heavy metal pollution. However, the effectiveness and security of compost application in agricultural soil continue to generate concern. In this review, the efficacy and mechanisms of compost remediation technologies for heavy metal-contaminated agricultural soil are presented. Poor quality, unsuitability for multiple heavy metal-contaminated soils, and potential long-term risks are the main limitations of the effectiveness and security of compost application to soils. Therefore, improving the quality of the compost, adding amendments, or combining with phytoremediation may be considered when adopting compost to remediate polluted agricultural soil. In addition, we propose several approaches to optimize these strategies and render the remediation of heavy metal-contaminated agricultural soil using compost safer and more effective. The findings of this review will help support the large-scale application of compost in agriculture in the future.

Controlling water and air pollution by photocatalysts is an advanced technique and has aroused great interest. TiO₂/hydroxyapatite (HAP) composites were successfully prepared via a one-step hydrothermal route that add a certain weight of tetrabutyl titanate to a mixed solution of Ca(NO₃)₂ and (NH₄)₂HPO₄, and then put into a Teflon-lined autoclave for hydrothermal reaction. The surface morphology, chemical composition, crystalline structure, and optical property of the TiO₂/HAP composites were characterized. The field emission-scanning electron microscopy (FE-SEM) observed the cube-like structure of crystal with the size of 10–20 μm. Energy dispersive X-ray spectrometry (EDS) and X-ray diffraction (XRD) demonstrated that Ti ₓ Ca₅₋ₓ (PO₄)₃(OH) was a unit of the crystal. UV–visible diffuse reflectance spectra show that the optical absorbance edge appeared at long wavelength (∼400 nm). Both higher temperature and longer time could contribute to the complete crystallization. Photocatalytic activity was evaluated by the degradation of rhodamine B (RhB) under visible light irradiation and found that the TiO₂/HAP composites exhibited excellent photocatalytic activity. Therefore, these TiO₂/HAP composites were expected to become one of advanced materials removing dyes from water.

The 2′,7′-dichlorofluorescin (DCFH) assay is widely used to measure particle-bound reactive oxygen species (ROS), which are considered as a major contributor leading to the adverse health effects upon exposure to atmospheric particulate matter. DCFH, a non-fluorescent substance that can be oxidized to highly fluorescent dichlorofluorescein (DCF) in the presence of horseradish peroxidase (HRP), is usually used as a probe for ROS determination due to its response to diverse and relevant oxidant species. However, there is limited literature that reports the effects of different experimental conditions in the performance of this assay. In our work, various experimental conditions, such as pH value, incubation temperature, reagent concentration and stability, reaction time, linearity range, and extraction method, were examined and optimized as a pilot study for developing an online system for atmospheric ROS measurement. The results showed that pH value, reagent concentration, and extraction method significantly affect the performance of DCFH assay, while incubation at a specified temperature (37 °C) did not increase the oxidization extent of DCFH. After optimization, some practical samples were measured using different experimental parameters to check the performance of the optimized assay. The comparisons of these measurements showed that optimization can greatly improve the detection limit and reproducibility of the DCFH assay, which can then be employed to better the accuracy of offline and online ROS measurement.

Embryonic and early postembryonic development of the cuttlefish Sepia officinalis (a cephalopod mollusk) occurs in coastal waters, an environment subject to considerable pressure from xenobiotic pollutants such as pharmaceutical residues. Given the role of serotonin in brain development and its interaction with neurodevelopmental functions, this study focused on fluoxetine (FLX), a selective serotonin reuptake inhibitor (SSRI, antidepressant). The goal was to determine the effects of subchronic waterborne FLX exposure (1 and 10 μg L⁻¹) during the last 15 days of embryonic development on neurochemical, neurodevelopmental, behavioral, and immunological endpoints at hatching. Our results showed for the first time that organic contaminants, such as FLX, could pass through the eggshell during embryonic development, leading to a substantial accumulation of this molecule in hatchlings. We also found that FLX embryonic exposure (1 and 10 μg L⁻¹) (1) modulated dopaminergic but not serotonergic neurotransmission, (2) decreased cell proliferation in key brain structures for cognitive and visual processing, (3) did not induce a conspicuous change in camouflage quality, and (4) decreased lysozyme activity. In the long term, these alterations observed during a critical period of development may impair complex behaviors of the juvenile cuttlefish and thus lead to a decrease in their survival. Finally, we suggest a different mode of action by FLX between vertebrate and non-vertebrate species and raise questions regarding the vulnerability of early life stages of cuttlefish to the pharmaceutical contamination found in coastal waters.

A granular hydrogel of chitosan-g-poly(vinylimidazole-co-2-acrylamido-2-methyl propane sulfonic acid) was successfully synthesized by one-step free radical polymerization based on the grafting backbone of chitosan and the monomers of vinylimidazole and 2-acrylamido-2-methyl propane sulfonic acid. The resulting hydrogel could be used as the adsorbent for the efficient and selective removal of Hg²⁺ ions from the aqueous solution. The adsorption results could be well described by the pseudo-second-order kinetic mode and the Langmuir isotherm model with a maximum adsorption capacity of 363.55 mg/g for Hg²⁺. Furthermore, the as-prepared granular hydrogel exhibited an excellent cycling stability for the adsorption of Hg²⁺ after multiple repeated adsorption-desorption process. It suggested that the obtained granular hydrogel has potential application for Hg²⁺ removal and recovery from wastewater. Graphical Abstract A kind of granular hydrogel with excellent selectivity adsorption of Hg2+ ions was successfully synthesized by grafting polymerization of VIM and AMPS onto the CTS backbone via a facile free radical polymerization.

This study investigates the effectiveness and mechanism of decreasing the bioavailability of Pb in bacterial culture and in pot experiments of Pb-contaminated paddy soil by Alishewanella sp. WH16-1. The WH16-1 strain was isolated from mine soil and exhibited high resistances to many heavy metals, especially to Pb²⁺ (2070 mg/L) and Cr (VI) (2340 mg/L). During cultivation of the WH16-1 strain with the addition of 100 mg/L Pb²⁺, Pb²⁺ was precipitated, and 84.13 % of Pb²⁺ was removed in 72 h. The precipitant was observed by transmission electron microscopy (TEM) and further confirmed to be PbS by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The WH16-1 strain was incubated in Pb²⁺-added paddy soil pot experiments for 60 days and compared with the uninoculated Pb²⁺-added paddy soil. Comparison showed that the exchangeable and carbonate-bound Pb in the paddy soil decreased by 14.04 and 10.69 % (P < 0.05), respectively. The Fe-Mn oxide-bound Pb, organic matter-bound Pb and the residual Pb increased by 4.47, 19.40, and 22.78 % (P < 0.05), respectively. Compared with the uninoculated Pb²⁺-added paddy soil, the dry weight of rice significantly increased by 28.59 %, and the Pb concentrations in rice, husk, leaves, and culms in Pb²⁺-added paddy soil pot experiment incubated with the WH16-1 strain significantly decreased by 26.18, 26.94, 26.61, and 25.56 % (P < 0.05), respectively. These results suggest that Alishewanella sp. WH16-1 can reduce the bioavailability of Pb in soil. This bacterium may be applicable for the biological stabilization of Pb in Pb-contaminated paddy soil.

Within the last few years, the presence of bentazone herbicide has been observed in many water resources. For the first time, removal of bentazone using mesoporous silica was investigated revealing reversible adsorption. The adsorption isotherm was well described using the Freundlich model. The affinity towards bentazone is strongly affected by pH in the range of 2–7, decreasing with the increase of the pH, becoming negligible at the neutrality. Regeneration of the adsorbent was possible, and a recovery as high as 70 % was obtained using CH₃OH-NaOH solution. Furthermore, appreciable recovery (47 %) was also obtained using water. Applications on the purification of lake water and wastewaters, both characterized by a significant organic carbon load, spiked with 2 mg L⁻¹ bentazone were tested, observing removal yields in the range of 61–73 %. Taking advantage of the fast adsorption kinetics observed, an in-flow purification treatment was set-up, with quantitative removal of bentazone from polluted water.