Apr 2022, Volume 16 Issue 2

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    Shansi Wang, Siwei Li, Jia Xing, Jie Yang, Jiaxin Dong, Yu Qin, Shovan Kumar Sahu

    •Strong ENSO influence on AOD is found in southern China region.

    •Low AOD occurs in El Niño but high AOD occurs in La Niña events in southern China.

    •Angstrom exponent anomalies reveals the circulation pattern during each ENSO phase.

    •ENSO exerts large influence (70.5%) on annual variations of AOD during 2002–2020.

    •Change of anthropogenic emissions is the dominant driver for AOD trend (2002–2020).

    Previous studies demonstrated that the El Niño–Southern Oscillation (ENSO) could modulate regional climate thus influencing air quality in the low-middle latitude regions like southern China. However, such influence has not been well evaluated at a long-term historical scale. To filling the gap, this study investigated two-decade (2002 to 2020) aerosol concentration and particle size in southern China during the whole dynamic development of ENSO phases. Results suggest strong positive correlations between aerosol optical depth (AOD) and ENSO phases, as low AOD occurred during El Niño while high AOD occurred during La Niña event. Such correlations are mainly attributed to the variation of atmospheric circulation and precipitation during corresponding ENSO phase. Analysis of the angstrom exponent (AE) anomalies further confirmed the circulation pattern, as negative AE anomalies is pronounced in El Niño indicating the enhanced transport of sea salt aerosols from the South China Sea, while the La Niña event exhibits positive AE anomalies which can be attributed to the enhanced import of northern fine anthropogenic aerosols. This study further quantified the AOD variation attributed to changes in ENSO phases and anthropogenic emissions. Results suggest that the long-term AOD variation from 2002 to 2020 in southern China is mostly driven (by 64.2%) by the change of anthropogenic emissions from 2002 to 2020. However, the ENSO presents dominant influence (70.5%) on year-to-year variations of AOD during 2002–2020, implying the importance of ENSO on varying aerosol concentration in a short-term period.

    Yanfei Chen, Ji Zheng, Miao Chang, Qing Chen, Cuicui Xiao

    • Quantification of efficiency and fairness of abatement allocation are optimized.

    • Allocation results are refined to the different abatement measures of enterprises.

    • Optimized allocation results reduce abatement costs and tap the abatement space.

    • Abatement suggestions are given to enterprises with different abatement quotas.

    For achieving air pollutant emission reduction targets, total pollutant amount control is being continuously promoted in China. However, the traditional pattern of pollutant emission reduction allocation regardless of economic cost often results in unreasonable emission reduction pathways, and industrial enterprises as the main implementers have to pay excessively high costs. Therefore, this study adopted economic efficiency as its main consideration, used specific emission reduction measures (ERMs) of industrial enterprises as minimum allocation units, and constructed an enterprise-level pollutant emission reduction allocation (EPERA) model with minimization of the total abatement cost (TAC) as the objective function, and fairness and feasibility as constraints for emission reduction allocation. Taking City M in China as an example, the EPERA model was used to construct a Pareto optimal frontier and obtain the optimal trade-off result. Results showed that under basic and strict emission reduction regulations, the TAC of the optimal trade-off point was reduced by 46.40% and 45.77%, respectively, in comparison with that achieved when only considering fairness, and the Gini coefficient was 0.26 and 0.31, respectively. The abatement target was attained with controllable cost and relatively fair and reasonable allocation. In addition, enterprises allocated different emission reduction quotas under different ERMs had specific characteristics that required targeted optimization of technology and equipment to enable them to achieve optimal emission reduction effects for the same abatement cost.

    Kaili Pang, Kaishan Zhang, Shuai Ma, Xiangrui Meng

    • Emissions from 53 in-use diesel-fueled off-road equipment were measured.

    • There exists a large off-road equipment variability in emissions.

    • Engine operations have significant impacts on real-world tailpipe emissions.

    • Emission inventory development should take into account job duties and operations.

    The objective of this paper is to quantify the variability in emissions of off-road equipment using a portable emission measurement system. A total of 53 commonly used equipment for agriculture, base construction, paving construction, and material handling were selected. Time-based and fuel-based emissions were quantified by different duty and engine modes. Three duty modes (idling, moving, and working) were used. Ten engine modes were defined based on normalized engine revolutions-per-minute and manifold absolute pressure, respectively. Composite emission factors taking into account both duty modes and its corresponding time percentage during a typical duty cycle were estimated. Results showed that there existed a large off-road equipment variability in emissions. Depending on duty and engine modes, time-based NO emissions ranged from 3.1 to 237.9, 29.1‒1475.6, 83.2‒681.6, and 3.2‒385.2 g/h for agriculture, base construction, paving construction and material handling equipment, respectively while for fuel-based NO emissions these ranges were 5.3‒52.0, 11.7‒69.0, 4.8‒30.8, and 11.0‒54.6 g/kg, respectively. Furthermore, emission factors derived from this study exhibited a much larger variability compared to those used in NONROAD by US EPA and National Guideline for Off-road Equipment of China. This implied that localized measurements of emissions are needed for improvement of accuracy of emission inventory. Furthermore, both equipment types and operations should be considered for development of emission inventory and control strategy.

    Keke Xiao, Zecong Yu, Kangyue Pei, Mei Sun, Yuwei Zhu, Sha Liang, Huijie Hou, Bingchuan Liu, Jingping Hu, Jiakuan Yang

    •Tryptophan protein, and aromatic protein I/II were the key identified proteins.

    •Cysteine was more correlated with methane production than other amino acids.

    •The presence of cysteine can promote methane production and degradation of VFAs.

    •The presence of cysteine can lower ORP and increase biomass activity.

    •Predominant Tissierella and Proteiniphilum were noted in pretreated sludge samples.

    Many studies have investigated the effects of different pretreatments on the performance of anaerobic digestion of sludge. However, the detailed changes of dissolved organic nitrogen, particularly the release behavior of proteins and the byproducts of protein hydrolysis-amino acids, are rarely known during anaerobic digestion of sludge by different pretreatments. Here we quantified the changes of three types of proteins and 17 types of amino acids in sludge samples solubilized by ultrasonic, thermal, and acid/alkaline pretreatments and their transformation during anaerobic digestion of sludge. Tryptophan protein, aromatic protein I, aromatic protein II, and cysteine were identified as the key dissolved organic nitrogen responsible for methane production during anaerobic digestion of sludge, regardless of the different pretreatment methods. Different from the depletion of other amino acids, cysteine was resistant to degradation after an incubation period of 30 days in all sludge samples. Meanwhile, the “cysteine and methionine metabolism (K00270)” was absent in all sludge samples by identifying 6755 Kyoto Encyclopedia of Genes and Genomes assignments of genes hits. Cysteine contributed to the generation of methane and the degradation of acetic, propionic, and n-butyric acids through decreasing oxidation-reduction potential and enhancing biomass activity. This study provided an alternative strategy to enhance anaerobic digestion of sludge through in situ production of cysteine.

    Rifeng Wu, Shanquan Wang

    •Bio-RD-PAO can effectively and extensively remove organohalides.

    •Bio-RD alone effectively dehalogenate the highly-halogenated organohalides.

    •PAO alone is efficient in degrading the lowly-halogenated organohalides.

    •The impacts of PAO on organohalide-respiring microbial communities remain elusive.

    •Bio-RD-PAO provides a promising solution for remediation of organohalide pollution.

    Due to the toxicity of bioaccumulative organohalides to human beings and ecosystems, a variety of biotic and abiotic remediation methods have been developed to remove organohalides from contaminated environments. Bioremediation employing organohalide-respiring bacteria (OHRB)-mediated microbial reductive dehalogenation (Bio-RD) represents a cost-effective and environmentally friendly approach to attenuate highly-halogenated organohalides, specifically organohalides in soil, sediment and other anoxic environments. Nonetheless, many factors severely restrict the implications of OHRB-based bioremediation, including incomplete dehalogenation, low abundance of OHRB and consequent low dechlorination activity. Recently, the development of in situ chemical oxidation (ISCO) based on sulfate radicals (SO4·) via the persulfate activation and oxidation (PAO) process has attracted tremendous research interest for the remediation of lowly-halogenated organohalides due to its following advantages, e.g., complete attenuation, high reactivity and no selectivity to organohalides. Therefore, integration of OHRB-mediated Bio-RD and subsequent PAO (Bio-RD-PAO) may provide a promising solution to the remediation of organohalides. In this review, we first provide an overview of current progress in Bio-RD and PAO and compare their limitations and advantages. We then critically discuss the integration of Bio-RD and PAO (Bio-RD-PAO) for complete attenuation of organohalides and its prospects for future remediation applications. Overall, Bio-RD-PAO opens up opportunities for complete attenuation and consequent effective in situ remediation of persistent organohalide pollution.

    Hui Hu, Lei Jiang, Longli Sun, Yanling Gao, Tian Wang, Chenguang Lv

    • A ZnO-biochar hybrid composite was prepared by solvothermal-pyrolysis synthesis.

    • The superhydrophobic composite is suitable for selective recovery of Re(VII).

    • The adsorption mechanism is elucidated by experiments and material characterization.

    The recovery of scattered metal ions such as perrhenate (Re(VII)) from industrial effluents has enormous economic benefits and promotes resource reuse. Nanoscale-metal/biochar hybrid biosorbents are attractive for recovery but are limited by their insufficient stability and low selectivity in harsh environments. Herein, a superstable biochar-based biosorbent composed of ZnO nanoparticles with remarkable superhydrophobic features is fabricated, and its adsorption/desorption capabilities toward Re(VII) in strongly acidic aqueous solutions are investigated. The ZnO nanoparticle/biochar hybrid composite (ZBC) exhibits strong acid resistance and high chemical stability, which are attributable to strong C-O-Zn interactions between the biochar and ZnO nanoparticles. Due to the advantages of its hydrolytic stability, superhydrophobicity, and abundance of Zn-O sites, the ZBC proves suitable for the effective and selective separation of Re(VII) from single, binary and multiple ion systems (pH= 1), with a maximum sorption capacity of 29.41 mg/g. More importantly, this material also shows good recyclability and reusability, with high adsorption efficiency after six adsorption-desorption cycles. The findings in this work demonstrate that a metal/biochar hybrid composite is a promising sorbent for Re(VII) separation.

    Zaishan Wei, Meiru Tang, Zhenshan Huang, Huaiyong Jiao

    Membrane bioreactor achieved mercury removal using nitrate as an electron acceptor.

    The biological mercury oxidation increased with the increase of oxygen concentration.

    Ferrous sulfide could make both Hg2+ and MeHg transform into HgS-like substances.

    Nitrate drives mercury oxidation through katE, katG, nar, nir, nor, and nos.

    Mercury (Hg0) is a hazardous air pollutant for its toxicity, and bioaccumulation. This study reported that membrane biofilm reactor achieved mercury removal from flue gas using nitrate as the electron acceptor. Hg0 removal efficiency was up to 88.7% in 280 days of operation. Oxygen content in flue gas affected mercury redox reactions, mercury biooxidation and microbial methylation. The biological mercury oxidation increased with the increase of oxygen concentration (2%‒17%), methylation of mercury reduced with the increase of oxygen concentration. The dominant bacteria at oxygen concentration of 2%, 6%, 17%, 21% were Halomonas, Anaerobacillus, Halomonas and Pseudomonas, respectively. The addition of ferrous sulfide could immobilize Hg2+ effectively, and make both Hg2+ and MeHg transform into HgS-like substances, which could achieve the inhibition effect of methylation, and promote conversion of mercury. The dominant bacteria changed from Halomonas to Planctopirus after FeS addition. Nitrate drives mercury oxidation through katE, katG, nar, nir, nor, and nos for Hg0 removal in flue gas.

    Hasti Daraei, Kimia Toolabian, Ian Thompson, Guanglei Qiu

    • ZnO-NP disrupted metabolic/catabolic balance of bacteria by affecting DHA activity.

    • ZnO-NPs toxicity was related to Zn2+ ion, interaction with cell and ROS generation.

    • Exposure to ZnO-NPs resulted in changed bacterial community structure at sludge.

    • The change in the EPS content was observed during exposure to ZnO-NPs.

    The unique properties and growing usage of zinc oxide nanoparticles increase their release in municipal wastewater treatment plants. Therefore, these nanoparticles, by interacting with microorganisms, can fail the suitable functioning of biological systems in treatment plants. For this reason, research into the toxicity of ZnO is urgent. In the present study, the toxicity mechanism of ZnO-NPs towards microbial communities central to granular activated sludge (GAS) performance was assessed over 120-day exposure. The results demonstrate that the biotoxicity of ZnO-NPs is dependent upon its dosage, exposure time, and the extent of reactive oxygen species (ROS) production. Furthermore, GAS performance and the extracellular polymeric substances (EPS) content were significantly reduced at 50 mg/L ZnO-NPs. This exposure led to decreases in the activity of ammonia monooxygenase (25.2%) and nitrate reductase (11.9%) activity. The Field emission scanning electron microscopy images confirmed that ZnO-NPs were able to disrupt the cell membrane integrity and lead to cell/bacterial death via intracellular ROS generation which was confirmed by the Confocal Laser Scanning Microscopy analysis. After exposure to the NPs, the bacterial community composition shifted to one dominated by Gram-positive bacteria. The results of this study could help to develop environmental standards and regulations for NPs applications and emissions.

    Yuan Cheng, Qinqin Yu, Jiumeng Liu, Youwen Sun, Linlin Liang, Zhenyu Du, Guannan Geng, Wanli Ma, Hong Qi, Qiang Zhang, Kebin He

    •Harbin showed relatively high threshold RH (80%) for apparent increase of SOR.

    •The observed SOR were at the lower end of the ratios from Beijing’s winter.

    •Temperature-dependent increase of NOR was sharper than that of SOR.

    • NOR increased with stronger biomass burning impact but SOR was largely unchanged.

    Formation of secondary inorganic aerosol (SIA) was investigated during a six-month long heating season in Harbin, China. Enhanced sulfate formation was observed at high relative humidity (RH), with the same threshold RH (80%) for both colder and warmer measurement periods. Compared to wintertime results from Beijing, the threshold RH was considerably higher in Harbin, whereas the RH-dependent enhancement of sulfur oxidation ratio (SOR) was less significant. In addition, the high RH events were rarely encountered, and for other periods, the SOR were typically as low as ~0.1. Therefore, the sulfate formation was considered inefficient in this study. After excluding the several cases with high RH, both SOR and the nitrogen oxidation ratio (NOR) exhibited increasing trends as the temperature increased, with the increase of NOR being sharper. The nitrate to sulfate ratio tended to increase with increasing temperature as well. Based on a semi-quantitative approach, this trend was attributed primarily to the temperature-dependent variations of precursors including SO2 and NO2. The influence of biomass burning emissions on SIA formation was also evident. With stronger impact of biomass burning, an enhancement in NOR was observed whereas SOR was largely unchanged. The different patterns were identified as the dominant driver of the larger nitrate to sulfate ratios measured at higher concentrations of fine particulate matter.

    Kun Li, Tingming Ye, Wang Zhang, Jianfeng Peng, Yaohui Bai, Weixiao Qi, Huijuan Liu

    • Chlorine addition enhanced the release of TOC, TN from the sediment.

    • Chlorine has a long-term negative effect on microbial richness.

    • Usually enzymes lose activity, and expression of genes was downregulated.

    • Carbon degradation and nitrification might be strongly inhibited.

    Chlorine is often used in algal removal and deodorization of landscape waters, and occasionally used as an emergency treatment of heavily polluted sediments. However, the ecological impact of this practice has not been fully studied and recognized. In this study, NaClO at 0.1 mmol/g based on dry weight sediment was evenly mixed into the polluted sediment, and then the sediment was incubated for 150 days to evaluate its microbial effect. Results showed that NaClO addition enhanced the release of TOC, TN, Cr and Cu from the sediment. The microbial richness in the examined sediment decreased continuously, and the Chao1 index declined from 4241 to 2731, in 150 days. The microbial community composition was also changed. The abundance of Proteobacteria and Bacteroidetes increased to 54.8% and 4.2% within 7 days compared to the control, and linear discriminant analysis (LDA) showed gram-negative bacteria and aerobic bacteria enriched after chlorination. The functional prediction with PICRUSt2 showed the functions of the microbial community underwent major adjustments, and the metabolic-related functions such as carbon metabolism, including pyruvate and methane metabolisms were significantly inhibited; besides, 15 out of 22 analyzed key enzymes involved in C cycling and 6 out of 12 key enzymes or genes involved in N cycling were strongly impacted, and the enzymes and genes involved in carbon degradation and denitrification showed remarkable downregulation. It can be concluded that chlorination posed a seriously adverse effect on microbial community structure and function. This study deepens the understanding of the ecological effects of applying chlorine for environmental remediation.

    Wanpeng Chen, Jiahui Song, Shaojie Jiang, Qiang He, Jun Ma, Xiaoliu Huangfu

    • The NPs aggregation in the electrolyte solution is consistent with the DLVO theory.

    • In NaNO3 and low Ca(NO3)2, EPS alleviates the NPs aggregation by steric repulsion.

    • In high Ca(NO3)2, EPS accelerates the NPs aggregation by exopolysaccharide bridging.

    • Ag2S NPs have stronger stability compared with Cit-Ag NPs in aqueous systems.

    Extracellular polymeric substances (EPS) in activated sludge from wastewater treatment plants (WWTPs) could affect interactions between nanoparticles and alter their migration behavior. The influence mechanisms of silver nanoparticles (Ag NPs) and silver sulfide nanoparticles (Ag2S NPs) aggregated by active EPS sludge were studied in monovalent or divalent cation solutions. The aggregation behaviors of the NPs without EPS followed the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The counterions aggravated the aggregation of both NPs, and the divalent cation had a strong neutralizing effect due to the decrease in electrostatic repulsive force. Through extended DLVO (EDLVO) model analysis, in NaNO3 and low-concentration Ca(NO3)2 (<10 mmol/L) solutions, EPS could alleviate the aggregation behaviors of Cit-Ag NPs and Ag2S NPs due to the enhancement of steric repulsive forces. At high concentrations of Ca(NO3)2 (10‒100 mmol/L), exopolysaccharide macromolecules could promote the aggregation of Cit-Ag NPs and Ag2S NPs by interparticle bridging. As the final transformation form of Ag NPs in water environments, Ag2S NPs had better stability, possibly due to their small van der Waals forces and their strong steric repulsive forces. It is essential to elucidate the surface mechanisms between EPS and NPs to understand the different fates of metal-based and metal-sulfide NPs in WWTP systems.

    Jian Lu, Cui Zhang, Jun Wu

    •Steroid hormones could be removed efficiently from mariculture system using seaweed;

    Caulerpa lentillifera was the most efficient seaweed for removal of steroid hormones;

    • More than 90% of E2 or EE2 were removed within 12 h using Caulerpa lentillifera;

    • The removal included the rapid biosorption and the slow bio-accumulation;

    •The hormones and nutrients in mariculture wastewater could be simultaneously removed.

    The removal of steroid hormones from the mariculture system using seaweeds (Caulerpa lentillifera, Ulva pertusa, Gracilaria lemaneiformis, and Codium fragile) was investigated. The results illustrated that both 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) could be removed by the seaweeds at different levels, and the Caulerpa lentillifera was the most efficient one. More than 90% of E2 or EE2 at concentration of 10 μg/L was removed by Caulerpa lentillifera within 12 h. Processes including initial quick biosorption, the following slow accumulation, and biodegradation might explain the removal mechanisms of E2/EE2 by Caulerpa lentillifera. E2/EE2 removal was positively related to the nutrient level and the initial concentration of steroid hormone. A significant linear relationship for E2 and EE2 existed between the initial pollutant concentration and the average removal rate. The highest removal kinetic constant (k) value was obtained at 30°C as 0.34 /h for E2 and at 20°C as 0.28 /h for EE2, demonstrating the promising application potential of Caulerpa lentillifera in the water purification of the industrialized mariculture system with relatively high water temperature. Simultaneous and efficient removal of E2 and EE2 by Caulerpa lentillifera was still achieved after 3 cycles in the pilot-scale experiment. The steroid hormones and nutrients in mariculture wastewater could also be simultaneously removed using Caulerpa lentillifera. These findings demonstrated that Caulerpa lentillifera was the promising seaweed for the removal of steroid hormones in mariculture systems.