Incineration of kitchen waste with high nitrogen in vortexing fluidized-bed incinerator and its NO emission characteristics

Some municipal solid waste (MSW) can be used as the fuel. Combustion of MSW with high nitrogen content is successfully conducted in a lab-scale vortexing fluidized-bed incinerator (VFBI). Pigskin with 16.5 wt.% nitrogen content was used to simulate the high nitrogen content kitchen waste, and silica sand was used as the bed material. The effects of operating conditions, such as the bed temperature, freeboard temperature, excess oxygen ratio, and static bed height on the CO and NO concentrations at the exit of combustor and cyclone were investigated. The experimental results show that the freeboard temperature is the most important factor for CO emission. The order of operating conditions impact on the NO emission is: (1) excess oxygen ratio; (2) bed temperature; (3) freeboard temperature; and (4) static bed height. Utilizing cyclone can significantly reduce the CO emission concentration when the CO concentration released from the freeboard is higher than 50 ppm. On the other hand, the cyclone has no significant effect on the NO emission. Despite having high nitrogen content, a low conversion from fuel-N to NO was attained. Compared with other types of combustors, VFBI reduces the CO and NO emission concentrations much better when burning MSW with high nitrogen content.     

Review on recent progress in on-line monitoring technology for atmospheric pollution source emissions in China

Emissions from mobile sources and stationary sources contribute to atmospheric pollution in China, and its components, which include ultrafine particles (UFPs), volatile organic compounds (VOCs), and other reactive gases, such as NH₃ and NO_x, are the most harmful to human health. China has released various regulations and standards to address pollution from mobile and stationary sources. Thus, it is urgent to develop online monitoring technology for atmospheric pollution source emissions. This study provides an overview of the main progress in mobile and stationary source monitoring technology in China and describes the comprehensive application of some typical instruments in vital areas in recent years. These instruments have been applied to monitor emissions from motor vehicles, ships, airports, the chemical industry, and electric power generation. Not only has the level of atmospheric environment monitoring technology and equipment been improving, but relevant regulations and standards have also been constantly updated. Meanwhile, the developed instruments can provide scientific assistance for the successful implementation of regulations. According to the potential problem areas in atmospheric pollution in China, some research hotspots and future trends of atmospheric online monitoring technology are summarized. Furthermore, more advanced atmospheric online monitoring technology will contribute to a comprehensive understanding of atmospheric pollution and improve environmental monitoring capacity.     

Differentiated emission control strategy based on comprehensive evaluation of multi-media pollution: Case of mercury emission control

In order to comprehensively evaluate the environmental impact of multi-media mercury pollution under differentiated emission control strategies in China, a literature review and case studies were carried out. Increased human exposure to methylmercury was assessed through the dietary intake of residents in areas surrounding a typical coal-fired power plant and a zinc(Zn) smelter, located either on acid soil with paddy growth in southern China, or on alkaline soil with wheat growth in northern Chi...     

Rapid field testing of mercury pollution by designed fluorescent biosensor and its cells-alginate hydrogel-based paper assay

With increasing industrial activities, mercury has been largely discharged into environment and caused serious environmental problems. The growing level of mercury pollution has become a huge threat to human health due to its significant biotoxicity. Therefore, the simple and fast means for on-site monitoring discharged mercury pollution are highly necessary to protect human beings from its pernicious effects in time. Herein, a “turn off” fluorescent biosensor (mCherry L199C) for sensing Hg²⁺ was successfully designed based on direct modification of the chromophore environment of fluorescent protein mCherry. For rapid screening and characterization, the designed variant of mCherry (mCherry L199C) was directly expressed on outer-membrane of  Escherichia coli cells by cell surface display technique. The fluorescent biosensor was characterized to have favorable response to Hg²⁺ at micromole level among other metal ions and over a broad pH range. Further, the cells of the fluorescent biosensor were encapsulated in alginate hydrogel to develop the cells-alginate hydrogel-based paper. The cells-alginate hydrogel-based paper could detect mercury pollution in 5 min with simple operation process and inexpensive equipment, and it could keep fluorescence and activity stable at 4?°C for 24 hr, which would be a high-throughput screening tool in preliminarily reporting the presence of mercury pollution in natural setting.     

Combined pollution of arsenic and Polymyxin B enhanced arsenic toxicity and enriched ARG abundance in soil and earthworm gut microbiotas

Polymyxin B (PMB) is considered as the last line of antibiotic defense available to humans. The environmental effects of the combined pollution with PMB and heavy metals and their interaction mechanisms are unclear. We explored the effects of the combined pollution with PMB and arsenic (As) on the microbial composition of the soil and in the earthworm gut, as well as the spread and transmission of antibiotic resistance genes (ARGs). The results showed that, compared with As alone, the combined addition of PMB and As could significantly increase the bioaccumulation factor and toxicity of As in earthworm tissues by 12.1% and 16.0%, respectively. PMB treatment could significantly increase the abundance of Actinobacteria in the earthworm gut (from 35.6% to 45.2%), and As stress could significantly increase the abundance of Proteobacteria (from 19.8% to 56.9%). PMB and As stress both could significantly increase the abundance of ARGs and mobile genetic elements (MGEs), which were positively correlated, indicating that ARGs might be horizontally transferred. The inactivation of antibiotics was the main resistance mechanism that microbes use to resist PMB and As stress. Network analysis showed that PMB and As might have antagonistic effects through competition with multi-drug resistant ARGs. The combined pollution by PMB and As significantly promoted the relative abundance of microbes carrying multi-drug resistant ARGs and MGEs, thereby increasing the risk of transmission of ARGs. This research advances the understanding of the interaction mechanism between antibiotics and heavy metals and provides new theoretical guidance for the environmental risk assessment and combined pollution management.     

Response of PM2.5-bound elemental species to emission variations and associated health risk assessment during the COVID-19 pandemic in a coastal megacity

The coronavirus (COVID-19) pandemic is disrupting the world from many aspects. In this study, the impact of emission variations on PM_2.5-bound elemental species and health risks associated to inhalation exposure has been analyzed based on real-time measurements at a remote coastal site in Shanghai during the pandemic. Most trace elemental species decreased significantly and displayed almost no diel peaks during the lockdown. After the lockdown, they rebounded rapidly, of which V and Ni even exceeded the levels before the lockdown, suggesting the recovery of both inland and shipping activities. Five sources were identified based on receptor modeling. Coal combustion accounted for more than 70% of the measured elemental concentrations before and during the lockdown. Shipping emissions, fugitive/mineral dust, and waste incineration all showed elevated contributions after the lockdown. The total non-carcinogenic risk (HQ) for the target elements exceeded the risk threshold for both children and adults with chloride as the predominant species contributing to HQ. Whereas, the total carcinogenic risk (TR) for adults was above the acceptable level and much higher than that for children. Waste incineration was the largest contributor to HQ, while manufacture processing and coal combustion were the main sources of TR. Lockdown control measures were beneficial for lowering the carcinogenic risk while unexpectedly increased the non-carcinogenic risk. From the perspective of health effects, priorities of control measures should be given to waste incineration, manufacture processing, and coal combustion. A balanced way should be reached between both lowering the levels of air pollutants and their health risks.     

Deactivation of Cu-SAPO-34 by urea-related deposits at low temperatures and the regeneration

Selective catalytic reduction(SCR) with urea catalyzed by Cu-SAPO-34 is an effective method to eliminate NO_x from diesel exhaust. However, urea-related deposits may form during cold-start and urban driving due to low exhaust temperatures. The activity of CuSAPO-34 at 175°C is significantly degraded by urea exposure, and 300°C is required for regeneration. Through in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS) and temperature-programmed hydrolysis studies, the dominant stable deposit at 175°C is identified as biuret, which can be eliminated at 300°C. The urea-derived deactivation and regeneration mechanisms of Cu-SAPO-34 were compared with those of anatase-supported catalysts.     

Physicochemical analysis of individual atmospheric fine particles based on effective surface-enhanced Raman spectroscopy

Fine particles associated with haze pollution threaten the health of more than 400 million people in China. It is therefore of great importance to thoroughly investigate and understand their composition. To determine the physicochemical properties in atmospheric fine particles at the micrometer level, we described a sensitive and feasible surface-enhanced Raman scattering(SERS) method using Ag foil as a substrate. This novel method enhanced the Raman signal intensities up to 10,000 a.u. for ν(NO_3~-) in fine particles.The SERS effect of Ag foil was further studied experimentally and theoretically and found to have an enhancement factor of the order of ～10~4. Size-fractionated real particle samples with aerodynamic diameters of 0.4–2.5 μm were successfully collected on a heavy haze day,allowing ready observation of morphology and identification of chemical components, such as soot, nitrates, and sulfates. These results suggest that the Ag-foil-based SERS technique can be effectively used to determine the microscopic characteristics of individual fine particles, which will help to understand haze formation mechanisms and formulate governance policies.     

Improved activity and durability of Rh-based three-way catalyst under diverse aging atmospheres by ZrO2 support

The catalytic activity and durability of Rh/ZrO_2 catalyst were investigated compared with Rh/Al_2O_3 catalyst under diverse aging atmospheres, including lean, rich and lean–rich cyclic aging atmospheres, to simulate the real working conditions of three-way catalyst.Oxidation states and microstructures of rhodium species were investigated to correlate with the catalytic performance of the catalysts. The catalytic performance and durability of the Rh catalyst under diverse aging atmospheres were drastically enhanced by ZrO_2 support. ZrO_2 support was confirmed to be able to effectively inhibit rhodium sintering even under diverse aging conditions. It can also successfully keep Rh species in an active low-valence state on the surface of the catalyst. The superiority of ZrO_2 support compared to Al_2O_3 was verified by the Rh-based monolith catalyst.     

Rapid degradation of carbon tetrachloride by commercial micro-scale zinc powder assisted by citric acid

We developed an effective method for degradation of carbon tetrachloride (CT) in contaminated water. Zinc metal as a reducing agent for CT in aqueous solutions has been previously studied in some detail, but the rapid corrosion of zinc surface usually reduces its efficiency in removing CT. We assumed that citric acid could enhance the degradation of CT by zinc powder due to the elimination of a passivation layer of Zn(II) (hydr)oxides on the surface of zinc powder through chelating of organic ligands with Zn(II) produced from the reaction and keeping the exposure of active sites to targets. Here the influence of citric acid on the decomposing of CT by commercial micro-scale zinc powder was investigated in a pH range of 3.5–7.5 at 25°C in batch experiments. Reaction mixtures were analysed by gas chromatography/headspace analysis, and Cl⁻ concentration was determined by turbidimetry. The results demonstrate that the degradation of CT by zinc metal alone is very weak, but the addition of citric acid can assist zinc powder to decompose CT more completely and rapidly at all pHs. Degradation of CT took place mainly in the first 10 min of reaction, coupled with 75–95% of CT removal. Maximum dechlorination percentage (82.4%) of CT was obtained at pH 5.5. In that case, chloroform and dichloromethane, as main intermediates, were found at low levels during the whole reaction, suggesting that CT may be sequentially and multiply degraded so quickly that methane is yielded before the intermediates can be desorbed and released to aqueous solution. When compared with the current methods of nano-scale zinc and bimetallic systems, the application of commercial micro-scale zinc particles assisted by organic ligands is of environmental significance since it allows decontamination of aqueous chlorinated organic compounds at low cost and with high efficiency.