Due to their increasing use, the residues of anti-neoplastic drugs have become emerging pollutants in aquatic environments. Most of them directly or indirectly interfere with the cell’s genome, which classifies them into a group of particularly dangerous compounds. The aim of the present study was to conduct a comparative in vitro toxicological characterisation of three commonly used cytostatics with different mechanisms of action (5-fluorouracil [5-FU], cisplatin [CDDP] and etoposide [ET]) towards zebrafish liver (ZFL) cell line, human hepatoma (HepG2) cells and human peripheral blood lymphocytes (HPBLs). Cytotoxicity was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and acridine orange/ethidium bromide staining. All three drugs induced time- and dose-dependent decreases in cell viability. The sensitivity of ZFL and HepG2 cells towards the cytotoxicity of 5-FU was comparable (half maximal inhibitory concentration (IC₅₀) 5.3 to 10.4 μg/mL). ZFL cells were more sensitive towards ET- (IC₅₀ 0.4 μg/mL) and HepG2 towards CDDP- (IC₅₀ 1.4 μg/mL) induced cytotoxicity. Genotoxicity was determined by comet assay and cytokinesis block micronucleus (CBMN) assay. ZFL cells were the most sensitive, and HPBLs were the least sensitive. In ZFL cells, induction of DNA strand breaks was a more sensitive genotoxicity endpoint than micronuclei (MNi) induction; the lowest effective concentration (LOEC) for DNA strand break induction was 0.001 μg/mL for ET, 0.01 μg/mL for 5-FU and 0.1 μg/mL for CDDP. In HepG2 cells, MNi induction was a more sensitive genotoxicity endpoint. The LOEC values were 0.01 μg/mL for ET, 0.1 μg/mL for 5-FU and 1 μg/mL for CDDP. The higher sensitivity of ZFL cells to cytostatic drugs raises the question of the impact of such compounds in aquatic ecosystem. Since little is known on the effect of such drugs on aquatic organisms, our results demonstrate that ZFL cells provide a relevant and sensitive tool to screen genotoxic potential of environmental pollutant in the frame of hazard assessment.

Adsorption by activated alumina is considered to be one of the most practiced methods for defluoridation of freshwater. This study was conducted, therefore, to investigate the effect of natural organic matters (NOMs) on the removal of fluoride by activated alumina using response surface methodology. To the authors’ knowledge, this has not been previously investigated. Physico-chemical characterization of the alumina was determined by scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), and X-ray diffractometer (XRD). Response surface methodology (RSM) was applied to evaluate the effect of single and combined parameters on the independent variables such as the initial concentration of fluoride, NOMs, and pH on the process. The results revealed that while presence of NOM and increase of pH enhance fluoride adsorption on the activated alumina, initial concentration of fluoride has an adverse effect on the efficiency. The experimental data were analyzed and found to be accurately and reliably fitted to a second-order polynomial model. Under optimum removal condition (fluoride concentration 20 mg/L, NOM concentration 20 mg/L, and pH 7) with a desirability value of 0.93 and fluoride removal efficiency of 80.6 %, no significant difference was noticed with the previously reported sequence of the co-exiting ion affinity to activated alumina for fluoride removal. Moreover, aluminum residual was found to be below the recommended value by the guideline for drinking water. Also, the increase of fluoride adsorption on the activated alumina, as NOM concentrations increase, could be due to the complexation between fluoride and adsorbed NOM.

Dissolved trace elements and heavy metals in the Dan River drainage basin, which is the drinking water source area of South-to-North Water Transfer Project (China), affect large numbers of people and should therefore be carefully monitored. To investigate the distribution, sources, and quality of river water, this study integrating catchment geology and multivariate statistical techniques was carried out in the Dan River drainage from 99 river water samples collected in 2013. The distribution of trace metal concentrations in the Dan River drainage was similar to that in the Danjiangkou Reservoir, indicating that the reservoir was significantly affected by the Dan River drainage. Moreover, our results suggested that As, Sb, Cd, Mn, and Ni were the major pollutants. We revealed extremely high concentrations of As and Sb in the Laoguan River, Cd in the Qingyou River, Mn, Ni, and Cd in the Yinhua River, As and Sb in the Laojun River, and Sb in the Dan River. According to the water quality index, water in the Dan River drainage was suitable for drinking; however, an exposure risk assessment model suggests that As and Sb in the Laojun and Laoguan rivers could pose a high risk to humans in terms of adverse health and potential non-carcinogenic effects.

The reuse of deinking paper mill effluent based on reverse osmosis is limited by silica scaling on the membranes. The removal of silica during softening processes is one of the most used approaches as it can treat large volumes of water at low cost, but when the water hardness is low, the addition of magnesium compounds is necessary. In the present investigation, MgCl₂·6H₂O was selected as magnesium source to analyze the effect of pH, dosage, temperature, and contact time on silica removal. Moreover, the silica removal mechanism was analyzed under different operational conditions. The results show that it is possible to obtain high silica removal rates (>70 %) at an intermediate dosage (750 mg/L of MgCl₂·6H₂O) either at high pH (12.0) and ambient temperature (20 °C) or lower pHs, i.e., pH = 10.5, but at higher temperatures 35–50 °C. The kinetic study demonstrates that contact times lower than 30 min are enough for silica removal with independence of the temperature. SEM-energy-dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR) analysis of the solids obtained confirms that silica is removed through the formation of magnesium silicates. The EDX analysis showed that, independently of the operational conditions, the atomic Si/Mg ratio was around 0.7 which indicates that antigorite (Mg₃Si₂O₅(OH)₄) is the predominant specie formed.

A miniaturized screen-printed electrode (SPE) modified with a carbon black-gold nanoparticle (CBNP-AuNP) nanocomposite has been developed as an electrochemical sensor for the detection of inorganic mercury ions (Hg²⁺). The working electrode surface has been modified with nanocomposite constituted of CBNPs and AuNPs by an easy drop casting procedure that makes this approach extendible to an automatable mass production of modified SPEs. Square wave anodic stripping voltammetry (SWASV) was adopted to perform Hg²⁺ detection, revealing satisfactory sensitivity and detection limit, equal to 14 μA ppb⁻¹ cm⁻² and 3 ppb, respectively. The applicability of the CBNP-AuNP-SPE for the determination of inorganic mercury has been assessed in river water by a simple filtration and acidification of the sample as well as in soil by means of a facile acidic extraction procedure assisted by ultrasound.

This study is the first to investigate the simultaneous presence of NH₄ ⁺ and fluorescent organic matter components (FOCs) from a fluvio-lacustrine aquifer in Central Jianghan Plain. Sediment, groundwater, and surface water samples were collected for the sediment organic matter extraction, 3D fluorescence spectroscopy characterization, and/or hydrochemical analysis. NH₄ ⁺ and dissolved organic carbon was ubiquitous in the groundwater. The fluorescence spectroscopy revealed good relationships between NH₄ ⁺ and fulvic acid-like components (FALCs) in the groundwater and sediment-extracted organic matter (SEOM) solutions. NH₄ ⁺ also exhibited significant positive correlation with protein-like component (PLC) (p < 0.001), with the stronger in the SEOM solutions than that in groundwater. Comparisons of spectroscopic indices [e.g., humification index (HIX), biological index (BIX), spectra slope (S₂₇₅–₂₉₅), and specific UV absorbance (SUVA₂₅₄)] between the groundwater and SEOM solutions revealed more labile properties of SEOM. This result indicates that the decreasing NH₄ ⁺–FOCs correlations of groundwater relative to sediments may be attributed to microbial degradation. Factor analysis identifies important factors that cause NH₄ ⁺ occurrence in the groundwater. The accompanying increase of FALC (C1) and NH4–N with the mole concentration of the normalized HCO₃ ⁻/(Ca²⁺+Mg²⁺) and [H⁺] suggests that couple effects of various biodegradations simultaneously occur in the aquifer, promoting the occurrence of NH₄–DOMs.

Spatial and temporal variability in nitrous oxide and methane emissions were quantified in three seasons using closed chambers in three riparian zone locations of three branches of the Pearl River, Guangzhou, China. The sampling sites were selected in a rapidly developing urban area of Guangzhou and represented a pollution gradient. The results show that urban riparian landscapes can be large source areas for CH₄ and N₂O, with fluxes of −0.035 ∼ 32.30 mg m⁻² h⁻¹ and −5.49 ∼ 37.31 μg m⁻² h⁻¹, respectively. River water quality, sediment texture, and NH₄-N and NO₃-N concentrations correlated with N₂O and CH₄ emission rates. The riparian zones of the more seriously polluted tributaries showed higher greenhouse gas fluxes than that of the less polluted main stem of the Pearl River. Rain events increased emissions of CH₄ by 6.5 ∼ 21.3 times and N₂O by 2.2 ∼ 5.7 times. The lower concentrations of heavy metals increased the activity of denitrifying enzymes while inhibited the methane producing pathways. This work demonstrates that rapidly developing urban areas are an important source of greenhouse gas emissions, which is conditioned by various environmental factors.

Soil salinity is a stringent abiotic constraint limiting crop growth and productivity. The present study was carried out to appraise the role of xylo-oligosaccharides (XOSs) in improving the salinity tolerance of Chinese cabbage. Salinity stress (0.5 % NaCl solution) and four levels (0, 40, 80, 120 mg L⁻¹) of XOSs were imposed on 20-day-old plants cultured under controlled conditions. Salinity stress decreased the aboveground fresh biomass, photosynthesis, transpiration rate, stomatal conductance, internal CO₂ concentration, water use efficiency, and chlorophyll contents but increased the stomatal limitation value of Chinese cabbage compared with control. Such physiological interferences, disturbances in plant water relations, and visually noticeable growth reductions in Chinese cabbage were significantly alleviated by the addition of XOSs under salinity stress. Under salinity stress, application of XOSs significantly enhanced the activities of enzymatic (superoxide dismutase, peroxidase, catalase) and non-enzymatic (ascorbate, carotene) antioxidants and reduced the malondialdehyde content in the leaves of Chinese cabbage. The XOS-applied plants under salinity stress also recorded higher soluble sugars, proline, and soluble protein content in their leaves. Exposure of salinity stress increased the ratio of Na⁺/K⁺, Na⁺/Ca²⁺, and Na⁺/Mg²⁺ in shoot as well as root of Chinese cabbage, however, XOS application significantly reduced these ratios particularly in shoot. Lower levels of XOSs (40 or 80 mg L⁻¹) were more effective for most of the studied attributes. The greater salinity tolerance and better growth in these treatments were related with enhanced antioxidative defense system, reduced lipid peroxidation, increased osmolyte accumulation, and maintenance of ionic balance.

The feasibility of using biochar as a sorbent to remove nine halogenated phenols (2,4-dichlorophenol, 2,4-dibromophenol, 2,4-difluorophenol, 2-chlorophenol, 4-chlorophenol, 2-bromophenol, 4-bromophenol, 2-fluorophenol, and 4-fluorophenol) and two pharmaceuticals (triclosan and ibuprofen) from water was examined through a series of batch experiments. Types of biochar, synthesized using various biomasses including fallen leaves, rice straw, corn stalk, used coffee grounds, and biosolids, were evaluated. Compared to granular activated carbon (GAC), most of the biochar samples did not effectively remove halogenated phenols or pharmaceuticals from water. The increase in pH and deprotonation of phenols in biochar systems may be responsible for its ineffectiveness at this task. When pH was maintained at 4 or 7, the sorption capacity of biochar was markedly increased. Considering maximum sorption capacity and properties of sorbents and sorbates, it appears that the sorption capacity of biochar for halogenated phenols is related to the surface area and carbon content of the biochar and the hydrophobicity of halogenated phenols. In the cases of triclosan and ibuprofen, the sorptive capacities of GAC, graphite, and biochars were also significantly affected by pH, according to the point of zero charge (PZC) of sorbents and deprotonation of the pharmaceuticals. Pyrolysis temperature did not affect the sorption capacity of halogenated phenols or pharmaceuticals. Based on the experimental observations, some biochars are good candidates for removal of halogenated phenols, triclosan, and ibuprofen from water and soil.