The purpose of the present research work is to investigate the stability and dissolution of magnetite (Fe₃O₄) nanoparticles (NPs) and thiol-functionalised mesoporous silica-coated magnetite NPs (TF-SCMNPs). The state of NPs in an aqueous environment was investigated under different pH conditions. Changes in the NPs’ mean diameter due to aggregation were measured over a specific time. The effects of contact time and pH on the dissolution of NPs were also investigated. In order to avoid possible aggregation, Fe₃O₄NPs were coated with silica and functionalised further with thiol organic groups. These methods imparted excellent stability to magnetite NPs in an aqueous medium over a wide range of pH values with reasonable hydrodynamic size. The organic group bound magnetite NPs allowed these particles to circulate over a long time in the aqueous system, and particle aggregation and sedimentation did not occur. The trend of decreasing zeta potential was observed after grafting thiol onto the surface of the SCMNPs. The results also revealed that silica exhibited a noteworthy efficient in eliminating the pH dependence and enhancing the NP stability of SCMNPs and SH-SCMNPs in aqueous medium. On the other hand, the dissolution of Fe₃O₄NPs was found to be detrimental at pH 2.0 and 4.0 or had a long contact time.

This paper studies the effects of the implementation of wastewater treatment (WWT) on the water quality of small urban river systems by considering as an extreme case study (volumetric contribution of wastewaters >50 %) the evolution of the Zenne River waters (Belgium) over the last 40 years. In urban rivers, organic matter (OM), oxygen, and nutrients are primarily controlled by wastewater releases which depend on the population and the WWT capacity in the river basin, the latter being dependent on environmental policy decisions. We introduce a novel basin-scale evaluation method that considers the evolution of annual pollutant loads at the outlet of the river basin directly as a function of WWT capacity. Based on this approach, we could prove that the load reductions observed after the implementation of WWT in the river basin was a good indicator of the global treatment efficiency of the WWT plants. We also show that high self-purification processes within the river basin may lead to reach minimum levels of OM before the completion of WWT. In addition, the effects of wet weather conditions did also change as a function of the WWT capacity going from positive effects at low capacity to negative effects at high capacity. Finally, the full implementation of WWT in urban river basins does not necessarily guarantee a good status for water quality, mostly because of the high volumetric proportion of treated wastewaters, which do not have the quality standards of river waters.

The major objective of this study was to evaluate the human health risks of agricultural land use conversion to other purposes in Hong Kong, based on the levels of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD/Fs) and determined dioxin-like activity in soil using ethoxyresorufin-O-deethylase (EROD) bioassay. Hazard quotient showed soils of open burning site (OBS) and electronic waste open burning site (EW (OBS)) exert a relatively higher non-cancer risk on adults (50.9 and 8.00) and children (407 and 64.0) via the pathway of accidental ingestion of soil particles than other types of land use. In addition, the levels of 17 PCDD/Fs congeners in OBS and EW (OBS) soils indicated high and moderate (1654 and 260 in one million people) cancer risks through the above pathway. Furthermore, the biologically derived TCDD concentrations (TEQbᵢₒ) were also significantly correlated to the chemically derived toxic equivalent concentrations of dioxin-like chemicals (TEQcₐₗ(sum of chemically derived 2,3,7,8-TeCDD toxic equivalent concentrations (TEQPCDD/F) and chemically derived dioxin-like PAHs toxic equivalent concentrations (TEQPAH)) (r = 0.770, p <0.05). PCDD/Fs (95.4 to 99.9 %) were the major stressor to the TEQcₐₗin the soil samples, indicating higher concentrations of PCDD/Fs derived from chemical analyses may reflect a higher potency of inducing EROD activity.

Compared to soil pollution by heavy metals and organic pollutants, soil pollution by fluorides is usually ignored in China. Actually, fluorine-contaminated soil has an unfavorable influence on human, animals, plants, and surrounding environment. This study reports on electrokinetic remediation of fluorine-contaminated soil and the effects of this remediation technology on soil fertility. Experimental results showed that electrokinetic remediation using NaOH as the anolyte was a considerable choice to eliminate fluorine in contaminated soils. Under the experimental conditions, the removal efficiency of fluorine by the electrokinetic remediation method was 70.35 %. However, the electrokinetic remediation had a significant impact on the distribution and concentrations of soil native compounds. After the electrokinetic experiment, in the treated soil, the average value of available nitrogen was raised from 69.53 to 74.23 mg/kg, the average value of available phosphorus and potassium were reduced from 20.05 to 10.39 mg/kg and from 61.31 to 51.58 mg/kg, respectively. Meanwhile, the contents of soil available nitrogen and phosphorus in the anode regions were higher than those in the cathode regions, but the distribution of soil available potassium was just the opposite. In soil organic matter, there was no significant change. These experiment results suggested that some steps should be taken to offset the impacts, after electrokinetic treatment.

Effective dehalogenation by nanoscale zerovalent iron (nZVI) has been reported. In this study, the effects of Ni²⁺, Cu²⁺ ions, and the nonionic surfactant Tween-80 on dechlorination of 2,2’,5,5’-tetrachlorinated biphenyl (PCB-52) by nZVI were investigated in aqueous solution. The rate of dechlorination was significantly enhanced by Ni²⁺, while Cu²⁺ had a less significant catalytic effect. Ni²⁺ and Tween-80 used in combination synergistically enhanced dechlorination of PCB-52 by nZVI, although the enhancement by Tween-80 was inhibitory in the presence of Cu²⁺ and insignificant in the absence of both metal ions. Congener specificity in the dechlorination pathway resulted from the preferential retention of ortho-chlorine, which restricted the formation of environmentally toxic coplanar PCB congeners. The application of nZVI dehalogenation enhanced by Ni²⁺ and Tween-80 is a promising technique for posttreatment of PCB-contaminated soil washing solutions.

This paper reports the connections between red blood cells abnormality risk of petrochemical workers and their exposure to airborne polycyclic aromatic hydrocarbons (PAHs). Urinary 1-hydroxypyrene (1-OHP), as the biomarker of PAHs exposure, was adopted to assess the exposure risk of the petrochemical workers to PAHs in Xigu, the west suburb of Lanzhou where petrochemical industries are located. Fifty-three workers, sub-grouped to 36 petrochemical workers and 17 office workers, participated in this investigation. Logistic regression model and spearman correlation analysis were performed to estimate the associations between PAHs exposure levels and red blood cells abnormality risk of petrochemical workers. Strong associations between some red cell indices (MCH, MCHC, RDW) and 1-OHP concentration were found. Results also show that the red blood cells abnormality risk increased with increasing PAHs exposure level. Compared with office workers, risk level of red blood cells abnormality in petrochemical workers was higher by 41.7 % (OR, 1.417; 95 % CI: 0.368–5.456) than that in office workers. This result was verified by the tissue-to-human blood partition coefficient for pyrene and 1-OHP. The quantitative assessments of the potential health risk through inhalation exposure to PAHs were conducted using the Incremental Lifetime Cancer Risk (ILCR) model. It was found the ILCR from inhalation exposure to PAHs for the petrochemical workers ranged from 10⁻⁵ to 10⁻⁴ with 95 % probability, indicating that petrochemical plant workers were under a high potential cancer risk level.

Nitrogen-fixing microorganisms (diazotrophs) play important roles in aquatic biogeochemistry and ecosystem functioning. However, little is known about the spatiotemporal variation of diazotrophic microbial communities in deep subtropical reservoirs. In this study, denaturing gradient gel electrophoresis (DGGE), clone libraries, quantitative PCR, and quantitative reverse transcription (RT)-PCR were used together to examine the vertical and seasonal patterns of diazotrophic microbial communities based on nitrogenase (nifH) gene sequences in the Dongzhen Reservoir, China, across time (every 3 months for 1 year) and space (five different water depths). In general, the numbers of DGGE bands increased with water depth during the stratification seasons (spring, summer, and autumn), with the clone-library-based operational taxonomic unit (OTU) number and nifH gene diversity being highest in autumn (6 OTUs at depth 0 m; 15 OTUs at 33 m) and winter (12 OTUs at 0 m, 13 OTUs at 33 m) but decreasing drastically in spring (2 OTUs at 0 m, 3 OTUs at 33 m) and summer (3 OTUs at 0 m, 2 OTUs at 33 m). The nifH gene abundance was lowest in the water mixing season (winter average, 5.17 × 10⁷ copies/L) but increased in the three other seasons (9.03 × 10⁹ copies/L). Cyanobacteria (dominated by filamentous thermophilic cyanobacteria and Cylindrospermopsis raciborskii) were the most dominant diazotrophic group at all depths and seasons, while both alphaproteobacteria and gammaproteobacteria were co-dominant in the bottom waters in autumn and winter. The distinct seasonal and spatial patterns in diazotrophic communities were significantly related to total nitrogen (TN) and ammonium nitrogen (NH₄-N) in the reservoir (P < 0.01). Further, TN showed a significant positive correlation with nifH RNA copy number (P < 0.05) and DGGE band number (P < 0.01), whereas the NH₄-N was negatively correlated with nifH DNA copy number (P < 0.01) and positively with both RNA/DNA ratio (P < 0.01) and DGGE band number (P < 0.01). Our data indicated that water stratification, mixing, and nitrogen might drive the diazotrophic community structure and activity in complex ways, thereby influencing the aquatic nitrogen cycle. Therefore, adaptive reservoir management strategies should carefully consider the effects of water stratification for protecting drinking water quality and for controlling the potential for diazotrophic cyanobacteria blooms.

Tetrabromobisphenol A (TBBPA) is currently the most widely used brominated flame retardant (BFR). To date, the toxic effects of TBBPA remains poorly understood in aquatic organisms, especially in bivalves. The objective of this experiment was to examine bioaccumulation and multibiomarker responses in the scallop Chlamys farreri exposed to TBBPA under laboratory conditions. The results showed that TBBPA was rapidly accumulated in and then eliminated from the gill and digestive gland of the scallops. TBBPA exposure invoked alterations in the detoxification system and induced oxidant stress and biomacromolecule damages in the gill and digestive gland of C. farreri. Additionally, glutathione-S-transferase (GST) activity, lipid peroxidation (LPO) level, cytochrome b5 (Cyt b5) content, and DNA strand break had good correlations with TBBPA accumulation levels in the gill and digestive gland of C. farreri. Summarizing, these results enabled us to hypothesize several toxic mechanisms of TBBPA and select potential biomarkers for TBBPA pollution monitoring.

The residues of organochlorine pesticides (OCPs) in 29 pine needle samples of typical regions (including Shihezi, Beitun, and Kanas) in Northern Xinjiang was determined with a gas chromatograph equipped with an electron capture detector. Total OCPs concentrations in pine needles ranged from 2.94 to 186 ng/g dry weight, with a mean concentration of 39.63 ng/g. The results indicated that Beitun was the most polluted region while Kanas was the least polluted one. Hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) were the predominant species in samples. Analysis of the sources of contamination showed that HCHs in the needles were derived from an old mixed source of technical HCHs or lindane. For DDTs, it was suspected to have recent application at some sites, which were derived mainly from a mixture of technical DDTs and dicofol containing DDT impurities. Categorical principal component analysis was performed in finding out more about the degradation behavior of DDTs and HCHs, which was identical with the results of source analysis.

New, sustainable, and low-cost materials that can simultaneously remove a range of wastewater contaminants, such as heavy metals and pharmaceutical residues, are needed. In this work, modified biochars were produced by dip-coating hickory or bagasse biomass in carbon nanotube (CNT) suspensions with or without sodium dodecylbenzenesulfonate (SDBS)-aided dispersion prior to slow pyrolysis in a N₂ environment at 600 °C. The sulfapyridine (SPY) and lead (Pb) sorption ability of pristine hickory (HC) and bagasse (BC) biochars and the modified biochars with (HC-SDBS-CNT and BC-SDBS-CNT, respectively) and without (HC-CNT and BC-CNT) SDBS was assessed in laboratory aqueous batch single- and binary-solute system. The greatest removal of SPY and Pb was observed for HC-SDBS-CNT (86 % SPY and 71 % Pb) and BC-SDBS-CNT (56 % SPY and 53 % Pb), whereas HC-CNT, BC-CNT, and the pristine biochars removed far less. This can be attributed to the fact that surfactant could prevent the aggregation of CNTs and thus promote the distribution and stabilization of individual CNT nanoparticle on the biochar surface to adsorb the contaminants. The observation of no significant change in Pb sorption capacities of the surfactant-dispersed CNT-modified biochars in the presence of SPY, or vice versa, was indicative of site-specific sorption interactions and a lack of significant competition for functional groups by the two sorbates. These results suggest that products of hybrid technologies, such as biochars modified with CNTs, can yield multi-sorbents and may hold excellent promise as a sustainable wastewater treatment alternative.