Increasing prevalence of antibiotic resistance genes in manured agricultural soils in northern China Abstract Land application of manure tends to result in the dissemination of antibiotic resistance in the environment. In this study, the influence of long-term manure application on the enrichment of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) in agricultural soils was investigated. All the analyzed eight ARGs (tetA, tetW, tetX, sulI, sulII, ermF, aac(6′)-Ib-cr and blaTEM) and two MGEs (intI1 and Tn916/1545) were detected in both the manured and control soils, with relative abundances ranging from 10−6 to 10−2. Compared with the control soil, the relative abundances of ARGs and MGEs in manured soils were enriched 1.0–18.1 fold and 0.6–69.1 fold, respectively. High-throughput sequencing analysis suggested that at the phylum level, the bacteria carrying intI1 and ermF might be mainly affiliated with Proteobacteria and Bacteroides, respectively. The dominant genera carrying intI1 and ermF could be Pseudomonas and Bacteroides, independent of manure application. Correlation analysis revealed that ARGs had strong links with soil physicochemical properties (TC, TN, and OM), heavy metals (Cu, Zn and Pb) and MGEs, indicating that the profile and spread of ARGs might be driven by the combined impacts of multiple factors. In contrast, soil pH and C/N exhibited no significant relationships with ARGs. Our findings provide evidence that long-term manure application could enhance the prevalence and stimulate the propagation of antibiotic resistance in agricultural soils.

Optimization and modeling of coagulation-flocculation to remove algae and organic matter from surface water by response surface methodology Abstract Seasonal algal blooms of Lake Yangcheng highlight the necessity to develop an effective and optimal water treatment process to enhance the removal of algae and dissolved organic matter (DOM). In the present study, the coagulation performance for the removal of algae, turbidity, dissolved organic carbon (DOC) and ultraviolet absorbance at 254 nm (UV254) was investigated systematically by central composite design (CCD) using response surface methodology (RSM). The regression models were developed to illustrate the relationships between coagulation performance and experimental variables. Analysis of variance (ANOVA) was performed to test the significance of the response surface models. It can be concluded that the major mechanisms of coagulation to remove algae and DOM were charge neutralization and sweep flocculation at a pH range of 4.66–6.34. The optimal coagulation conditions with coagulant dosage of 7.57 mg Al/L, pH of 5.42 and initial algal cell density of 3.83 × 106 cell/mL led to removal of 96.76%, 97.64%, 40.23% and 30.12% in term of cell density, turbidity, DOC and UV254 absorbance, respectively, which were in good agreement with the validation experimental results. A comparison between the modeling results derived through both ANOVA and artificial neural networks (ANN) based on experimental data showed a high correlation coefficient, which indicated that the models were significant and fitted well with experimental results. The results proposed a valuable reference for the treatment of algae-laden surface water in practical application by the optimal coagulation-flocculation process.

Anaerobic phenanthrene biodegradation with four kinds of electron acceptors enriched from the same mixed inoculum and exploration of metabolic pathways Abstract Polycyclic aromatic hydrocarbons (PAHs) are widespread and persistent contaminants worldwide, especially in environments devoid of molecular oxygen. For lack of molecular oxygen, researchers enhanced anaerobic zones PAHs biodegradation by adding sulfate, bicarbonate, nitrate, and iron. However, microbial community reports of them were limited, and information of metabolites was poor except two-ring PAH, naphthalene. Here, we reported on four phenanthrene-degrading enrichment cultures with sulfate, bicarbonate, nitrate, and iron as electron acceptors from the same initial inoculum. The high-to-low order of the anaerobic phenanthrene biodegradation rate was the nitrate-reducing conditions>sulfate-reducing conditions>methanogenic conditions>iron-reducing conditions. The dominant bacteria populations were Desulfobacteraceae, Anaerolinaceae, and Thermodesulfobiaceae under sulfate-reducing conditions; Moraxellaceae, Clostridiaceae, and Comamonadaceae under methanogenic conditions; Rhodobacteraceae, Planococcaceae, and Xanthomonadaceae under nitrate-reducing conditions; and Geobacteraceae, Carnobacteriaceae, and Anaerolinaceae under iron-reducing conditions, respectively. Principal component analysis (PCA) indicated that bacteria populations of longtime enriched cultures with four electron acceptors all obtained significant changes from original inoculum, and bacterial communities were similar under nitrate-reducing and iron-reducing conditions. Archaea accounted for a high percentage under iron-reducing and methanogenic conditions, and Methanosarcinaceae and Methanobacteriaceae, as well as Methanobacteriaceae, were the dominant archaea populations under iron-reducing and methanogenic conditions. The key steps of phenanthrene biodegradation under four reducing conditions were carboxylation, further ring system reduction, and ring cleavage.

Impacts of emissions and meteorological changes on China’s ozone pollution in the warm seasons of 2013 and 2017 Abstract We have quantified the impacts of anthropogenic emissions reductions caused by the Air Pollution Control Action Plan and changes in meteorological fields between 2013 and 2017 on the warm-season O3 concentration in China using a regional 3D chemical transport model. We found that the impact on daily maximum eight-hour (MDA8) O3 concentration by the meteorological variation that mostly increased O3 was greater than that from emission reduction, which decreased O3. Specifically, the control measures implemented since 2013 in China have reduced SO2, NOx, PM2.5, and VOC emissions by 33%, 25%, 30%, and 4% in 2017, while NH3 emissions have increased by 7%. The changes in anthropogenic emissions lowered MDA8 O3 by 0.4–3.7 ppb (0.8%–7.6%, varying by region and month), although MDA8 O3 was increased slightly in some urban areas (i.e. North China) at the beginning/end of warm seasons. Relative to 2013, the average 2 m temperature in 2017 shows increments in North, North-east, East, and South China (0.34°C–0.83°C) and decreases in Central China (0.24°C). The average solar radiation shows increments in North, North-east, and South China (7.0–9.7 w/m2) and decreases in Central, South-west, and North-west China (4.7–10.3 w/m2). The meteorological differences significantly change MDA8 O3 by −3.5–8.5 ppb (−8.2%–18.8%) with large temporal variations. The average MDA8 O3 was slightly increased in North, North-east, East, and South China. The response surface model suggests that the O3 formation regime transfers from NOx-saturated in April to NOx-limited in July on average in China.

Influence of phosphate on deposition and detachment of TiO 2 nanoparticles in soil Abstract The widespread use of TiO2 nanoparticles (NPs) makes inevitable their release into the soil. Phosphate is also widespread within soil, and is likely copresent with TiO2 NPs. However, the influence of phosphate on deposition/release— and thereby on transport— of TiO2 NPs in soil is yet to be elucidated. In this study we conducted saturated column experiments to systematically examine the transport of TiO2 NPs in soil amended with phosphate at different ionic strengths (ISs) (1, 10, 100 mmol/L NaCl) and pHs (4 and 9). Results show that the deposition of TiO2 NPs decreased with decreasing IS, increasing pH, and when soil absorbed phosphate. These observations are qualitatively in agreement with Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy calculations, because the repulsive energy barrier is larger and secondary minimum depth is smaller at a lower IS, higher pH, and in the presence of phosphate. Accordingly, both primary- and secondary-minimum deposition were inhibited. Interestingly, although the deposition was less at higher pH and in the presence of phosphate, the subsequent spontaneous detachment and detachment by reduction of solution IS in these cases were greater. In addition, the presence of phosphate in the solution can cause a small quantity of attached TiO2 NPs to detach, even without perturbations of physical and chemical conditions. Our study was the first to investigate the influence of phosphate on detachment of TiO2 NPs and the results have important implication for accurate prediction of fate and transport of TiO2 NPs in subsurface environments.

Enhanced activation of peroxymonosulfate by CNT-TiO 2 under UV-light assistance for efficient degradation of organic pollutants Abstract In this work, a UV-light assisted peroxymonosulfate (PMS) activation system was constructed with the composite catalyst of multi-walled carbon nanotubes (CNT) — titanium dioxide (TiO2). Under the UV light irradiation, the photoinduced electrons generated from TiO2 could be continuously transferred to CNT for the activation of PMS to improve the catalytic performance of organic pollutant degradation. Meanwhile, the separation of photoinduced electron-hole pairs could enhance the photocatalysis efficiency. The electron spin resonance spectroscopy (EPR) and quenching experiments confirmed the generation of sulfate radical (SO4•−), hydroxyl radical (•OH) and singlet oxygen (1O2) in the UV/PMS/20%CNT-TiO2 system. Almost 100% phenol degradation was observed within 20 min UV-light irradiation. The kinetic reaction rate constant of the UV/PMS/20%CNT-TiO2 system (0.18 min−1) was 23.7 times higher than that of the PMS/Co3O4 system (0.0076 min−1). This higher catalytic performance was ascribed to the introduction of photoinduced electrons, which could enhance the activation of PMS by the transfer of electrons in the UV/PMS/CNT-TiO2 system.

Effects of cultivation strategies on the cultivation of Chlorella sp. HQ in photoreactors Abstract The effects of cultivation strategies (including autotrophic cultivation (AC), heterotrophic cultivation (HC), fed-batch cultivation (FC), heterotrophic + autotrophic two-stage cultivation (HATC), and heterotrophic + mixotrophic two-stage cultivation (HMTC)) on the growth and lipid accumulation of Chlorella sp. HQ and its total nitrogen (TN) and total phosphorus (TP) removal in secondary effluent were investigated in column photoreactors. The results showed that the TN and TP removal rates ranged between 93.72%–95.82% and 92.73%–100%, respectively, under the five different strategies. The microalgal growth potential evaluated by the maximal growth rate (Rmax) was in the order of HMTC>HC>FC>AC>HATC. The values of biomass, total lipid yield, triacylglycerols (TAGs) yield, and total lipid content of the microalga cultivated in the last 5 d increased significantly, but the TAGs productivities of the five strategies were lower than those in the first 7 d. Compared with all the other cultivation strategies, the TAGs productivity and yield after 12 d of cultivation under the heterotrophic condition reached the highest values accompanying the highest level of intracellular reactive oxygen species (ROS), in which the TAGs yield reached 40.81 mg/L at the end of the cultivation period. The peaks in TAGs yield and ROS level suggested that HC was beneficial for lipids accumulation via regulating the cellular redox status and exerting ROS stress on microalgal cells. In summary, HMTC was the best cultivation strategy for improving the microalgal biomass and HC was the best strategy for microalgal TAGs accumulation to produce biodiesel.

An integrated optimization and simulation approach for air pollution control under uncertainty in open-pit metal mine Abstract Open-pit metal mines contribute toward air pollution and without effective control techniques manifests the risk of violation of environmental guidelines. This paper establishes a stochastic approach to conceptualize the air pollution control model to attain a sustainable solution. The model is formulated for decision makers to select the least costly treatment method using linear programming with a defined objective function and multi-constraints. Furthermore, an integrated fuzzy based risk assessment approach is applied to examine uncertainties and evaluate an ambient air quality systematically. The applicability of the optimized model is explored through an open-pit metal mine case study, in North America. This method also incorporates the meteorological data as input to accommodate the local conditions. The uncertainties in the inputs, and predicted concentration are accomplished by probabilistic analysis using Monte Carlo simulation method. The output results are obtained to select the cost-effective pollution control technologies for PM25, PM10, NOx, SO2 and greenhouse gases. The risk level is divided into three types (loose, medium and strict) using a triangular fuzzy membership approach based on different environmental guidelines. Fuzzy logic is then used to identify environmental risk through stochastic simulated cumulative distribution functions of pollutant concentration. Thus, an integrated modeling approach can be used as a decision tool for decision makers to select the cost-effective technology to control air pollution.

Electrocoagulation process for the treatment of metal-plating wastewater: Kinetic modeling and energy consumption Abstract It is known that wastewater produced by the metal-plating industry contains several heavy metals, which are acidic in nature and therefore toxic for the environment and for living creatures. In particular, heavy metals enter the food chain and accumulate in vital organs and cause serious illness. The precipitation of these metals is mostly achieved by pH adjustment, but as an alternative to this method, the electrocoagulation process has investigated in this study using iron and aluminum electrodes. The effects of the pH adjustment on removal before and after the electrocoagulation process were investigated, and cost analyses were also compared. It was observed that a high proportion of removal was obtained during the first minutes of the electrocoagulation process; thus, the current density did not have a great effect. In addition, the pH adjustment after the electrocoagulation process using iron electrodes, which are 10% more effective than aluminum electrodes, was found to be much more efficient than before the electrocoagulation process. In the process where kinetic modeling was applied, it was observed that the heavy metal removal mechanism was not solely due to the collapse of heavy metals at high pH values, and with this modeling, it was seen that this mechanism involved adsorption by iron and aluminum hydroxides formed during the electrocoagulation process. When comparing the ability of heavy metals to be adsorbed, the sequence was observed to be Cr>Cu>Ni>Zn, respectively.

Pesticides in stormwater runoff—A mini review Abstract Recently, scientific interest has grown in harvesting and treating stormwater for potable water use, in order to combat the serious global water scarcity issue. In this context, pesticides have been identified as the key knowledge gap as far as reusing stormwater is concerned. This paper reviewed the presence of pesticides in stormwater runoff in both rural and urban areas. Specifically, the sources of pesticide contamination and possible pathways were investigated in this review. Influential factors affecting pesticides in stormwater runoff were critically identified as: 1) characteristics of precipitation, 2) properties of pesticide, 3) patterns of pesticides use, and 4) properties of application surface. The available pesticide mitigation strategies including best management practice (BMP), low impact development (LID), green infrastructure (GI) and sponge city (SC) were also included in this paper. In the future, large-scale multi-catchment studies that directly evaluate pesticide concentrations in both urban and rural stormwater runoff will be of great importance for the development of effective pesticides treatment approaches and stormwater harvesting strategies.