The impoundment of the Three Gorges Reservoir (TGR) in China influences the quality of the water supply. Surface sediment samples from the TGR mainstream and three tributaries were collected. Acid volatile sulfide (AVS), simultaneously extractable metals (SEMs), and the fraction of organic carbon (fₒc) were used to assess the toxicity of heavy metals. Sediment quality guidelines (SQGs) were established using the equilibrium partitioning approach. The results showed that the surface sediments were found to be oxic or suboxic. AVS concentrations in sediments were relatively low, below SEM concentrations. The [SEM] − [AVS] model indicated that all sediments possibly have adverse effects on aquatic life. However, ([SEM] − [AVS])/fₒc predicted no adverse biological effects in some areas of the Meixi and Caotang Rivers, while adverse effects to aquatic life were uncertain for the other sediments. The partitioning coefficients, water quality criteria, and residual metals in the sediments were the main factors influencing the SQGs for the TGR, while the metals bound to AVS had a negligible effect. The normalized TGR SQGs were all much higher than the existing standards except for cadmium and copper. The differences might be attributed to the approaches used for derivation of SQGs and the physical and chemical characteristics of the sediments.

Cultivars of hot pepper (Capsicum annuum L.) have different abilities to accumulate Cd in their fruits. Previously, we suggested that low-Cd cultivars take up more Cd, but can better prevent the Cd translocation from roots to aerial parts. However, the mechanisms involved in those processes are still unclear. In this study, we explored the roles of rhizosphere soil Cd fractions and root secretions of low molecular weight organic acids in the uptake, translocation, and accumulation of Cd in a low-Cd and high-Cd cultivar. The results showed that there was no significant difference in exchangeable Cd between rhizosphere soils of the two cultivars, which might be related to their similar root’s Cd uptake ability. The total content of low molecular weight organic acids released from roots of the low-Cd cultivar was almost equal to that released from roots of the high-Cd cultivar at the same Cd level; however, the composition of low molecular weight organic acids were determined by cultivars and Cd exposure levels. In the higher Cd (10 μM) treatment, the roots of the low-Cd cultivar excreted significantly less tartaric acid and more oxalic and acetic acids than those of the high-Cd cultivar. Additionally, there was no difference in the concentration of citric or succinic acid between the two cultivars. These results indicate that some kinds of low molecular weight organic acids efflux from hot pepper roots played an important role in the difference of Cd accumulation between low- and high-Cd cultivars.

The purposes and intent of the authorities in establishing water quality standards are to provide enhancement of water quality and prevention of pollution to protect the public health or welfare in accordance with the public interest for drinking water supplies, conservation of fish, wildlife and other beneficial aquatic life, and agricultural, industrial, recreational, and other reasonable and necessary uses as well as to maintain and improve the biological integrity of the waters. In this way, water quality controls involve a large number of variables and observations, often subject to some outliers. An outlier is an observation that is numerically distant from the rest of the data or that appears to deviate markedly from other members of the sample in which it occurs. An interesting analysis is to find those observations that produce measurements that are different from the pattern established in the sample. Therefore, identification of atypical observations is an important concern in water quality monitoring and a difficult task because of the multivariate nature of water quality data. Our study provides a new method for detecting outliers in water quality monitoring parameters, using turbidity, conductivity and ammonium ion as indicator variables. Until now, methods were based on considering the different parameters as a vector whose components were their concentration values. This innovative approach lies in considering water quality monitoring over time as continuous curves instead of discrete points, that is to say, the dataset of the problem are considered as a time-dependent function and not as a set of discrete values in different time instants. This new methodology, which is based on the concept of functional depth, was applied to the detection of outliers in water quality monitoring samples in the Nalón river basin with success. Results of this study were discussed here in terms of origin, causes, etc. Finally, the conclusions as well as advantages of the functional method are exposed.

Soils sampled from different locations of China were used to manipulate soil microbial diversity and to assess the effect of the diversity of the soil nitrifying community on the recovery of the soil nitrification to metal stress (zinc). Ten treatments were either or not amended with ZnCl₂. Subsequently, a spike-on-spike assay was set up to test for the tolerance of soil nitrification to zinc (Zn) and copper (Cu). Initially, Zn amendment completely inhibited nitrification. After a year of Zn exposure, recovery of the potential nitrification rate in Zn-amended soils ranged from 28 to 126 % of the potential nitrification rate in the corresponding Zn-nonamended soils. This recovery was strongly related to the potential nitrification rate before Zn amendment and soil pH. Increased Zn tolerance of the soil nitrification was consistently observed in response to corresponding soil contamination. Co-tolerance to Cu was obtained in all 1,000-mg kg⁻¹ Zn-amended soils. This tolerance was also strongly related to the potential nitrification rate before Zn amendment and soil pH. Our data indicate that inherently microbial activity can be a significant factor for the recovery of soil functioning derived from metal contamination.

Olive oil agrifood industry generates large amounts of waste whose recycling as organic amendment represents an alternative to their disposal. The impact of de-oiled two-phase olive mill waste (DW) on the fate of 4-chloro-2-methylphenoxyacetic acid (MCPA) in Mediterranean agricultural soils was evaluated. Furthermore, the effect of the transformation of organic matter from this waste under field conditions was assessed. Four Mediterranean agricultural soils were selected and amended in laboratory with fresh DW and field-aged DW (DW and ADW treatments, respectively). Adsorption capacity increased by factors between 1.18 and 3.59, for the DW-amended soils, and by factor of 4.93, for ADW-amended soil, with respect to unamended soils, when 5 % amendment was applied. The DW amendment had inhibitory effect on dehydrogenase activity and slowed herbicide dissipation, whereas the opposite effect was observed in ADW treatments. In the field-amended soil, the amount of MCPA leached was significantly reduced from 56.9 % for unamended soil to 15.9 % at the 5 % rate. However, leaching losses of MCPA increased in the laboratory-amended soils, because of their high water-soluble organic carbon values which could enhance MCPA mobility, especially in the acidic soils. Therefore, the application of DW as organic amendment in Mediterranean agricultural soils could be an important management strategy to reduce MCPA leaching, especially if the organic matter had been previously transformed by ageing processes.

The overuse of antibiotics in livestock farms is general, leading to a wide distribution of antibiotic resistance genes (ARGs) in aquatic environment adjacent to livestock farms. However, researches of the distribution and types of ARGs in aquatic environment of China are still in the initial stage. In this study, wastewater and surface water samples were collected from 12 livestock farms (four pig farms, four cattle farms, and four chicken farms) in Jiangsu Province of China. The prevalence, abundance, and distribution of 22 ARGs were investigated, which were categorized into six groups, including nine tetracyclin resistance genes, three sulfonamides resistance genes, three quinolone resistance genes, two macrolide resistance genes, three aminoglycoside resistance genes, and two multidrug resistance genes, employing quantitative real-time PCR (qPCR). The results suggested that all of the 22 ARGs were detected in samples. Sul1, sul2, and tetM were the most abundant with the average concentration of 3.84 × 10¹ copies/16S recombinant RNA (rRNA) gene copies, 1.62 × 10¹ copies/16S rRNA gene copies, 2.33 × 10¹ copies/16S rRNA gene copies, respectively. Principle component analysis revealed that the comprehensive pollution of ARGs in northern Jiangsu was more serious. ARGs in wastewater were more abundant when compared to that in surface water. A preliminary study regarding the fate of ARGs after an aerobiotic process showed that tetA, tetC, sul1, sul2, oqxB, and qnrS were significantly increased. And, among the tetracycline resistance genes, the efflux pump genes were enriched while the ribosomal protection protein encoding genes were decreased in the aerobiotic process. The prevalance of ARGs in water environment is of concern; more surveillance is required to determine the pollution level and pattern of antibiotic resistance genes.

Preparation of novel nanocomposite particles (NCPs) with high visible-light-driven photocatalytic activity and possessing recovery potential after advanced oxidation process (AOP) is much desired. In this study, pure anatase phase titania (TiO₂) nanoparticles (NPs) as well as three types of NCPs including nitrogen-doped titania (TiO₂-N), titania-coated magnetic silica (Fe₃O₄ cluster@SiO₂@TiO₂ (FST)), and a novel magnetically recoverable TiO₂ nanocomposite photocatalyst containing nitrogen element (Fe₃O₄ cluster@SiO₂@TiO₂-N (FST-N)) were successfully synthesized via a sol–gel process. The photocatalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM) with an energy-dispersive X-ray (EDX) spectroscopy analysis, X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), and vibrating sample magnetometer (VSM). The photocatalytic activity of as-prepared samples was further investigated and compared with each other by degradation of phenol, as a model for the organic pollutants, in deionized (DI) water under visible light irradiation. The TiO₂-N (55 ± 1.5 %) and FST-N (46 ± 1.5 %) samples exhibited efficient photocatalytic activity in terms of phenol degradation under visible light irradiation, while undoped samples were almost inactive under same operating conditions. Moreover, the effects of key operational parameters, the optimum sample calcination temperature, and reusability of FST-N NCPs were evaluated. Under optimum conditions (calcination temperature of 400 °C and near-neutral reaction medium), the obtained results revealed efficient degradation of phenol for FST-N NCPs under visible light irradiation (46 ± 1.5 %), high yield magnetic separation and efficient reusability of FST-N NCPs (88.88 % of its initial value) over 10 times reuse.

The enhanced H₂ production from maize straw had been achieved through the two-stage process of integrating H₂ fermentation and microbial electrolysis cells (MECs) in the present work. Several key parameters affecting hydrolysis of maize straw through subcritical H₂O were optimized by orthogonal design for saccharification of maize straw followed by H₂ production through H₂ fermentation. The maximum reducing sugar (RS) content of maize straw reached 469.7 mg/g-TS under the optimal hydrolysis condition with subcritical H₂O combining with dilute HCl of 0.3 % at 230 °C. The maximum H₂ yield, H₂ production rate, and H₂ content was 115.1 mL/g-TVS, 2.6 mL/g-TVS/h, and 48.9 % by H₂ fermentation, respectively. In addition, the effluent from H₂ fermentation was used as feedstock of MECs for additional H₂ production. The maximum H₂ yield of 1060 mL/g-COD appeared at an applied voltage of 0.8 V, and total COD removal reached about 35 %. The overall H₂ yield from maize straw reached 318.5 mL/g-TVS through two-stage processes. The structural characterization of maize straw was also carefully investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) spectra.

This paper estimated the mercury (Hg), emission factor, and mass balance from caged fish farming in the Castanhão Reservoir, NE Brazil, based on monitoring of a typical farm of Nile tilapia (Oreochromis niloticus). The total Hg input to the farm reached 1.45 gHg ha⁻¹ year⁻¹, from which 0.21 gHg ha⁻¹ year⁻¹ was exported out as fish biomass, ultimately resulting in an emission factor of 1.24 gHg ha⁻¹ year⁻¹ for the reservoir or approximately 8.27 mgHg ton fish⁻¹ year⁻¹ produced. Most of the input came from aquafeeds with concentrations varying from 1.4 to 31.1 ng g⁻¹, depending on the type of aquafeed. The Hg concentrations in fish were very low and varied from 1.0 to 2.9 ng g⁻¹. These values are two orders of magnitude lower than the legal limit for human consumption. The estimated total annual discharge of Hg from farming into the reservoir is 174 g for 18,000 tons of fish produced and may reach 387 g when the reservoir reaches its total capacity (40,000 tons), which is expected to occur in 2020. The mass balance, considering the deposition and accumulation rates, showed that approximately 40 % of the total Hg input accumulate in farm sediments (0.72 g ha⁻¹ year⁻¹), which is approximately 60 % of the deposition rate estimated through the sediment traps and suggests that 0.54 gHg ha⁻¹ year⁻¹ could eventually be transported out of the farm to the reservoir. Notwithstanding these facts, the total annual input of Hg from fish farming to the Castanhão Reservoir is less than 1.0 % of the total input from anthropogenic sources.

Soil contamination by heavy metals, due to human activities, is not often limited to a single contaminant. The objective of this study was to develop a simple model for phytoextracting separate and combined Ni and Cd from contaminated soils. The study was further aimed to study phytoextraction potential of ornamental kale and land cress grown in soils contaminated with separate and combined Ni and Cd metals. The results indicated that elevated Ni and Cd concentrations in soil inhibit growth of both ornamental kale and land cress plants. In Ni + Cd treatments, growth and development of both plants were more affected than in either Ni or Cd treatments. Further, in Ni + Cd treatments, Ni concentration in tissues of both plants was increased by increasing soil Ni concentration under various Cd concentrations. At constant Ni concentration, addition of Cd did not appreciably changed Ni content of plant tissues. Land cress demonstrated higher tolerance to soil contamination by Ni and Cd compared to ornamental kale. It also demonstrated higher phytoextraction potential for soil Cd than ornamental kale. Enhanced bioavailability of Ni and Cd ions, due to competitive adsorption and desorption reactions, had no reasonable effect on metal ion accumulation in plant tissues. This indicates that at relatively high soil contamination, metal ion adsorption is no longer a limiting factor for phytoremediation. The newly proposed model, which assumes that metal uptake rate inversely depends on total soil metal ion concentration, reasonably well predicted the cleanup time of Ni, Cd, and Ni at the presence of Cd from the contaminated soils. The model also predicts that phytoremediation process takes much longer time when soil is contaminated by multi-metal ions.