PAH emissions from coal combustion and waste incineration

Simultaneous removal of naphthalene and NOx over V-Ce/Ti catalyst: Design of separated active sites for naphthalene degradation and SCR reaction

V-Ce/Ti catalysts were prepared for the removal of naphthalene and NOx in the flue gas. The adverse effects of NH3 and NO on the naphthalene degradation were weakened on V-Ce/Ti, resulting in a decrease of only 2.5 % in COx selectivity. The formation of high molecular weight byproducts was also reduced. Besides the acid sites on the catalysts, Ce introduced new Brønsted basic sites, which could also adsorb and degrade naphthalene into naphthol effectively. With the separated active sites for naphthalene degradation and NO removal, the reaction between NH3 and the intermediates during the naphthalene degradation was also inhibited, decreasing the formation and accumulation of phthalimide. The oxidation of the intermediates was promoted by active V5+ introduced by Ce, inhibiting the transformation of the intermediates to higher molecular weight byproducts. Nearly 100 % conversion of naphthalene and NO, as well as 40.1 % of the COx selectivity were obtained on V-Ce/Ti.

The modification of surface basicity and its role in naphthalene oxidation: The effect of the basic sites introduced by Ce

A series of V-xCe/Ti catalysts was prepared by a step impregnation method with gradual increased Ce amount. Compared to the commercial V-W/Ti catalysts, the V-xCe/Ti catalysts exhibited considerably higher COx selectivity during the oxidation of naphthalene (Nap), and less intermediates or by-products were detected both in gas phase and on the surface of the catalysts. Through a series of characterizations, it was found that abundance of weak basic sites in the form of OH was introduced by Ce, as well as the oxygen vacancies caused by the redox cycle of V4++Ce4+↔V5++Ce3+. The weak basic sites introduced by Ce could greatly enhance the Nap adsorption, and the Nap adsorbed was quickly converted to naphthol on Ce-OH. Furthermore, V existed at a high valence with the interaction of V and Ce, and the oxygen vacancies also increased the Oads and OOH. It improved the redox ability and the regeneration of Ce-OH on V-xCe/Ti catalysts. The intermediates could be further oxidized, and the Ce-OH consumed in the reaction could recover quickly. Therefore, almost 100% Nap conversion and a high COx selectivity was observed in the V-xCe/Ti catalysts system.

Potential Strategy to Control the Organic Components of Condensable Particulate Matter: A Critical Review

More and more attention has been paid to condensable particulate matter (CPM) since its emissions have surpassed that of filterable particulate matter (FPM) with the large-scale application of ultralow-emission reform. CPM is a gaseous material in the flue stack but instantly turns into particles after leaving the stack. It is composed of inorganic and organic components. Organic components are an important part of CPM, and they are an irritant, teratogenic, and carcinogenic, which triggers photochemical smog, urban haze, and acid deposition. CPM organic components can aggravate air pollution and climate change; therefore, consideration should be given to them. Based on existing methods for removing atmospheric organic pollutants and combined with the characteristics of CPM organic components, we provide a critical overview from the aspects of (i) fundamental cognition of CPM, (ii) common methods to control CPM organic components, and (iii) catalytic oxidation of CPM organic components. As one of the most encouraging methods, catalytic oxidation is discussed in detail, especially in combination with selective catalytic reduction (SCR) technology, to meet the growing demands for multipollutant control (MPC). We believe that this review is inspiring for a fuller understanding and deeper exploration of promising approaches to control CPM organic components.

Enhanced mitigation of inhalable particles and fine particle-bound PAHs from a novel hazardous waste-power plant candidate

Emissions of the inhalable particle (dp < 10 μm, PM10) and their harmful compositions from combustion sources have high potential on health risk with nearly no regulation. This study investigates the particle size distribution (PSD), as well as the removal mechanism of PM10 and fine particle (FP)-bound polycyclic aromatic hydrocarbons (PAHs) from the flue gas of a hazardous waste thermal treatment system. It has ultralow regulated emission and becomes a candidate of power generation module. A series of the advanced scrubbers, cyclonic demister, and baghouse was equipped for multi-pollutant control. The moderate or intense low oxygen dilution (MILD) combustion effectively inhibited the PM2.5 generation by volumetric oxidation. Advanced scrubbers removed PM1, PM2.5, and PM10 by 85.24, 68.68, and 97.60%, respectively, which achieved by local supersaturation, heterogeneous condensation of water vapor, and the growth of fine PM. Moreover, the scrubbers effectively scavenged the course PM10 containing the high-molecular-weight PAH homologs onto the water phase but promoted the condensation and absorption of the lighter homologs onto the fine particle surface (dp ∼5.3 μm). The size window (dp = 0.3-1.0 μm) of the minimum efficiency reporting value of a BH filtration led to the peak of FP-PAH mass and BaP equivalent (BaPeq) toxicity at dp = 0.1-0.4 and 0.1-0.8 μm, respectively. Consequently, the synergy of MILD combustion and the SCB-CYC-BH system effectively inhibited the PM2.5, PM10, PM2.5-PAHs, and FP-PAH levels from a waste thermal treatment process and further mitigated the potential health risk.

Voltammetric determination of flufenamic acid and adsorption studies with biochar in the absence / presence of cetyltrimethylammonium bromide

In this article, a novel method for the determination of Flufenamic acid (FFA, pharmaceutical pollutant) is presented based on voltammetric oxidation at a carbon paste electrode (CPE) in-situ modified with cetyltrimethylammonium bromide (CTAB). The experimentally proved "erosion effect" of this surfactant enhanced the sensitivity of detection in the SWASV mode allowing us to quantify the analyte down to the low nanomolar level (with a LOD of 5.5 × 10-9 mol L-1 FFA). The respective (electro)analytical procedure has been shown to be applicable in monitoring the residua of FFA in model aqueous solutions simulating polluted and then purified industrial wastewater. Furthermore, the process of removal of FFA via adsorption onto selected carbonaceous materials was studied in detail, when two conventional active carbon adsorbents were compared with biochar (BC) - a cheaper alternative. It has been found that although the latter as such does not attain the adsorption capacities of both active carbons, in-situ modification of BC with CTAB enhances its adsorption capacity up to 40% (from 125 mg g-1 to ca. 175 mg g-1), as well as fastens the adsorption process (3x); both under conditions of testing. When considering the final procedure for removal of residual pollutant from model water samples with BC and the method of choice for quantification of the corresponding change(s) of FFA before and after purification, the principal role of CTAB has been revealed and defined. Namely, the functioning of CTAB had, in fact, double benefit: (i) enhancement of adsorptive capabilities of the BC adsorbent and (ii) improved sensitivity of the voltammetric detection with in-situ modified CPE.

Longitudinal association of polycyclic aromatic hydrocarbons and genetic risk with lung function

To quantify the association of polycyclic aromatic hydrocarbons (PAHs) and the polygenic risk score (PRS) with lung function decline, we developed a repeated-measures study with 4681 observations from baseline and 6-year follow-up of the Wuhan-Zhuhai cohort. Lung function and urinary monohydroxylated PAH metabolites (OH-PAHs) were measured for each observation. The PRS was derived from 246 lung function-associated genetic variants weighted by the effect size of the decreasing ratio of forced expiratory volume in 1 s by forced vital capacity (FEV1/FVC). Linear mixed models were used to estimate the longitudinal exposure-response relationships between OH-PAHs and lung function, and to evaluate the interactions between OH-PAHs and PRS on the longitudinal change of lung function. We found that each 1-unit increase in log-transformed values of 9-hydroxyfluorene, 2-hydroxyfluorene, 4-hydroxyphenanthrene, 9-hydroxyphenanthrene, 2-hydroxyphenanthrene, 1-hydroxyphenanthrene, 1-hydroxypyrene, low molecular weight OH-PAHs (ΣLMW-OH-PAHs), and total OH-PAHs (ΣOH-PAHs) was associated with an annual change in FEV1/FVC of -0.140, -0.112, -0.260, -0.300, -0.159, -0.220, -0.145, -0.156, and -0.177 %/year, respectively. Interactions on the annual decline of FEV1/FVC were detected between ΣLMW-OH-PAHs and PRS (-0.010 %/year, 95% confidence interval -0.018 to -0.001, Pint = 0.0228), and between ΣOH-PAHs and PRS (-0.010 %/year, -0.018 to -0.001, Pint = 0.0203). These results indicated that specific and total urinary OH-PAHs were associated with the longitudinal FEV1/FVC decline, and ΣLMW-OH-PAHs as well as ΣOH-PAHs interacted with PRS on the annual decline of FEV1/FVC.

Polycyclic aromatic hydrocarbons in the sediments of highly polluted coastal area in the Red Sea: levels, spatial distribution, and risk assessment

The southern part of the Jeddah coast faces a range of pollution challenges that can impact the water quality and ecosystem in the area. Pollution sources are represented mainly by treated wastewater (TWW), harbor activities, and atmospheric deposition from vehicle exhaust emissions. Polycyclic aromatic hydrocarbons (PAHs) are among the persistent organic pollutants that interfere with all environmental matrices and could cause humane mutagenic and carcinogenic effects. In the present study, 16 priority parent and 21 methylated PAHs (∑37PAHs) were assessed in the sediments of three hot spot coastal sites (Islamic Jeddah port, Al-Arbaeen, and Al-Shabab lagoons) to evaluate the factors affecting their spatial distribution, examine their probable sources and potential adverse effects. The total detected concentrations of ∑37PAHs ranged from 785.9 to 8359.8 ng/g dw (average: 2296.3 ± 2017.3 ng/g dw). The highest levels of ∑37PAHs were detected near TWW stations. The highest individual PAH congeners observed were phenanthrene, anthracene, and pyrene. PAH molecular diagnostic ratios pointed out different pyrogenic sources. In some specific stations, there was an overlap of petrogenic origin. The sediment samples contained high concentrations of methylated PAHs, with concentrations ranging from 558.42 to 6321.21 ng/g dw and an average concentration of 1679.1 ± 1430.7 ng/g dw. The sediment quality guidelines indicated that adverse biological effects are likely to occur at least at the two TWW disposal stations and the sediments in these stations are at risk. The values of the mutagenic equivalence quotient (MEQ) and toxic equivalence quotient (TEQ) of carcinogenic PAHs were recorded at 39.88 and 33.17 ng/g, respectively.

Molecular distribution, sources and potential health risks of fine particulate-bound polycyclic aromatic hydrocarbons during high pollution episodes in a subtropical urban city

Abundance of fine particulate-bound 16 priority polycyclic aromatic hydrocarbons (PAHs) was investigated to ascertain its sources and potential carcinogenic health risks in Varanasi, India. The city represents a typical urban settlement of South Asia having particulate exposure manyfold higher than standard with reports of pollution induced mortalities and morbidities. Fine particulates (PM2.5) were monitored from October 2019 to May 2020, with 32% of monitoring days accounting ≥100 μgm-3 of PM2.5 concentration, frequently from November to January (99% of monitoring days). The concentration of 16 priority PAHs varied from 24.1 to 44.6 ngm-3 (mean: 33.1 ± 3.2 ngm-3) without much seasonal deviations. Both low (LMW, 56%) and high molecular weight (HMW, 44%) PAHs were abundant, with Fluoranthene (3.9 ± 0.4ngm-3) and Fluorene (3.5 ± 0.3ngm-3) emerged as most dominating PAHs. Concentration of Benzo(a)pyrene (B(a)P, 0.5 ± 0.1ngm-3) was lower than the national standard as it contributed 13% of total PAHs mass. Diagnostic ratios of PAH isomers indicate predominance of pyrogenic sources including emissions from biomass burning, and both from diesel and petrol-driven vehicles. Source apportionment using receptor model revealed similar observation of major PAHs contribution from biomass burning and fuel combustion (54% of source contribution) followed by coal combustion for residential heating and cooking purposes (44%). Potential toxicity of B[a]P equivalence ranged from 0.003 to 1.365 with cumulative toxicity of 2.13ngm-3. Among the PAH species, dibenzo[h]anthracene contributed maximum toxicity followed by B[a]P, together accounting 86% of PAH induced carcinogenicity. Incremental risk of developing cancer through lifetime exposure (ILCR) of PAHs was higher in children (3.3 × 10-4) with 56% contribution from LMW PAHs, primarily through ingestion and dermal contact. Adults in contrast, were more exposed to inhale airborne PAHs with cumulative ILCR of 2.2 × 10-4. However, ILCR to PM2.5 exposure is probably underestimated considering unaccounted metal abundance thus, require source-specific control measures.

A nationwide survey of polycyclic aromatic hydrocarbons (PAHs) in household dust in China: spatial distribution, sources, and health risk assessment

As a carrier of toxic substances, household dust has a great impact on human health. Here we collected 73 household dust samples from 27 provinces and 1 municipality in China to investigate the levels, spatial distribution, sources, and carcinogenic risk of 16 polycyclic aromatic hydrocarbons (PAHs). The total concentrations of 14 detected PAHs (∑₁₄ PAHs) ranged from 3.72 to 60,885 ng g^-1. High ∑₁₄ PAHs were found in Northeast and Southwest China. High molecular weights (HMW) PAHs (4-6 rings) were predominant PAHs in most dust samples, accounting for 93.6% of ∑₁₄ PAHs. Household fuel, cooking frequency, air conditioning, and smoking were the main factors influencing PAH concentrations in household dust. Principal component analysis model indicated that fossil combustion (81.5%) and biomass combustion and vehicle exhaust (8.1%) are the primary sources of PAHs. Positive matrix factorization model suggested that household cooking and heating contributed about 70% of ∑₁₄ PAHs, and smoking contributed another 30%. The values of benzo[a]pyrene equivalent in rural dust were found to be higher than those in urban dust. The sum of toxic equivalents (TEQs) of 14 PAHs were in range of 0.372-7241 ng g^-1, in which 7 HMW PAHs accounted for 98.0 ± 1.98% of the total TEQs. Monte Carlo Simulation showed a low to moderate potential carcinogenic risk of PAHs in household dusts. This study documents comprehensive information on human exposure to PAHs in household dust at a national-scale.

Health risk assessment of inorganic and organic constituents of the coarse and fine PM in an industrialized region of Brazil

A health risk assessment of inorganic and organic species associated with coarse and fine particulate matter (PM) was conducted in Southeastern Brazil. TSP, PM₁₀, and PM_2.5 samples were collected, and their elemental (metals/metalloids) and organic (PAHs) composition were determined by EDXRF and GC-MS. The health risks were determined through hazard quotient (HQ) and cancer risk (CR). It was found that different elements and routes of exposure lead to different health risks, even for the PM concentration in compliance with air quality standards. The major routes of exposure for adults were inhalation and dermal contact whereas for children were ingestion and dermal contact. High non-cancer risks (HQ) caused by Cl and Fe exposure were associated with coarser fractions, PM₁₀ and TSP, respectively, whereas high HQ for Se, Sb, and V exposure were associated with PM_2.5. HQ values for children were near twice that for adults, and CR values were 65 % to 130 % higher for children than for adults. CR posed by PAHs was negligible. The results highlighted that the HQ might be over- or underestimated depending on the form in which the element Cl is determined (elemental or ion), reinforcing the need for an embracing chemical characterization of the PM. High HQ values were found related to the exposure to some elements present in the TSP, showing that this PM fraction should not be neglected.

Review on distribution, fate, and management of potentially toxic elements in incinerated medical wastes

Medical wastes include all solid and liquid wastes that are produced during the treatment, diagnosis, and immunisation of animals and humans. A significant proportion of medical waste is infectious, hazardous, radioactive, and contains potentially toxic elements (PTEs) (i.e., heavy metal (loids)). PTEs, including arsenic (As), cadmium (Cd), lead (Pb) and mercury (Hg), are mostly present in plastic, syringes, rubber, adhesive plaster, battery wastes of medical facilities in elemental form, as well as oxides, chlorides, and sulfates. Incineration and sterilisation are the most common technologies adopted for the safe management and disposal of medical wastes, which are primarily aimed at eliminating deadly pathogens. The ash materials derived from the incineration of hazardous medical wastes are generally disposed of in landfills after the solidification/stabilisation (S/S) process. In contrast, the ash materials derived from nonhazardous wastes are applied to the soil as a source of nutrients and soil amendment. The release of PTEs from medical waste ash material from landfill sites and soil application can result in ecotoxicity. The present study is a review paper that aims to critically review the dynamisms of PTEs in various environmental media after medical waste disposal, the environmental and health implications of their poor management, and the common misconceptions regarding medical waste.

Adsorption characteristic analysis of PAHs on activated carbon with different functional groups by molecular simulation

As widespread organic pollutants in the environment, polycyclic aromatic hydrocarbons (PAHs) greatly threaten human health. The adsorption technology has become one of the main methods to deal with PAHs because of its low cost, simple design, and no secondary pollution. Among them, solid media have strong adsorption capacities for PAHs and are widely used. In this work, activated carbon was chosen as the solid adsorbent. The adsorption behavior of three PAHs (naphthalene, anthracene, and phenanthrene) on activated carbon was investigated at the molecular level by Grand Canonical Monte Carlo (GCMC) method. The effects of different functional groups (amino, carboxyl, hydroxyl, carbonyl, and hydrogen groups) and temperature effect on the adsorption isotherms and heat of adsorption of PAHs on activated carbon were calculated. The results showed that the carbonyl functional group increased the adsorption of PAH molecules by the most considerable amount among all the functional groups. Acid functional groups were more favorable to the adsorption of PAHs than alkali functional groups. The adsorption capacity and heat of adsorption of PAHs decreased when the temperature increased. The adsorption performance of bicyclic aromatic hydrocarbons was more influenced by temperature than that of tricyclic aromatic hydrocarbons.

Emission and distribution profiles of polycyclic aromatic hydrocarbons in solid residues of municipal and industrial waste incinerators, Northern Vietnam

The concentrations and profiles of 18 polycyclic aromatic hydrocarbons (PAHs) in particulate matter (PM₁₀), fly ash (FA), and bottom ash (BA) were examined in three incineration residues. Samples were collected from different municipal and industrial solid waste incinerators in Northern Vietnam. The average concentrations of total PAHs in PM₁₀, fly ash, and bottom ash were 9.55 × 10³ ng/Nm³, 215 × 10³ ng/g, and 2.38 ng/g, respectively. Low-molecular-weight PAHs (2 to 3 rings) were predominant in most samples. The emission factor of total PAHs decreased in the order of FA > BA > PM₁₀. A higher concentration of total PAHs was found in industrial facilities than that in municipal ones. The high carcinogenic proportion of PAHs together with significantly high annual emissions reflect the high pollution risk to the ecosystem by PAHs in the case of reuse of incineration ashes (e.g., brick production). Regarding the carcinogenic risk of PAH-bounded ashes or particles, calculations from this study imply the significant threat for workers who have been manipulated in the incineration facilities, directly exposed to fly and bottom ashes. Meanwhile, the risk from PAH-bound particulate was not considered a significant threat for both normal adults and children. Further study on PAHs contained in incinerator waste dumps should be conducted in Vietnam to assess the potential contamination risk of these incineration by-products.

The Effects of Trash, Residential Biofuel, and Open Biomass Burning Emissions on Local and Transported PM2.5 and Its Attributed Mortality in Africa

Long-term exposure to ambient fine particulate matter (PM_2.5) is the second leading risk factor of premature death in Sub-Saharan Africa. We use GEOS-Chem to quantify the effects of (a) trash burning, (b) residential solid-fuel burning, and (c) open biomass burning (BB) (i.e., landscape fires) on ambient PM_2.5 and PM_2.5-attributable mortality in Africa. Using a series of sensitivity simulations, we excluded each of the three combustion sources in each of five African regions. We estimate that in 2017 emissions from these three combustion sources within Africa increased global ambient PM_2.5 by 2%, leading to 203,000 (95% confidence interval: 133,000-259,000) premature mortalities yr^-1 globally and 167,000 premature mortalities yr^-1 in Africa. BB contributes more ambient PM_2.5-related premature mortalities per year (63%) than residential solid-fuel burning (29%) and trash burning (8%). Open BB in Central Africa leads to the largest number of PM_2.5-attributed mortalities inside the region, while trash burning in North Africa and residential solid-fuel burning in West Africa contribute the most regional mortalities for each source. Overall, Africa has a unique ambient air pollution profile because natural sources, such as windblown dust and BB, contribute strongly to ambient PM_2.5 levels and PM_2.5-related mortality. Air pollution policies may need to focus on taking preventative measures to avoid exposure to ambient PM_2.5 from these less-controllable sources.

Characteristics, secondary transformation and odor activity evaluation of VOCs emitted from municipal solid waste incineration power plant

Volatile organic compounds (VOCs) emitted from municipal solid waste incineration power plant (MSWIPP) plays a significant role in the formation of O₃ and PM_2.5 and odor pollution. Field test was performed on four MSWIPPs in an area of the North China Plain. Nonmethane hydrocarbons (NMHCs) and 102 VOCs were identified and quantified. Ozone formation potential (OFP), secondary organic aerosol formation potential (SOAFP), and odor activity of the detected VOCs were evaluated. Results showed that the average concentration of NMHCs and VOCs were 1648.6 ± 1290.4 μg/m³ and 635.3 ± 588.8 μg/m³, respectively. Aromatics (62.1%), O-VOCs (16.0%), and halo hydrocarbons (10.0%) were the main VOCs groups in the MSWIPP exhaust gas. VOCs emission factor of MSWIPP was 2.43 × 10³ ± 2.27 × 10³ ng/g-waste. The OFP and SOAFP of MSWIPP were 960.18 ± 2158.17 μg/m³ and 1.57 ± 3.38 μg/m³, respectively. Acrolein as the dominant VOC species was the major odor contributor with a percentage of odor contribution of 65.9%. Benzene and 1,2,4-trimethylbenzene as the dominant VOC species were the main contributors of O₃ formation potentials, in which 1,2,4-trimethylbenzene was also the main contributors of SOA formation potential.

Cancer risk assessment and source apportionment of the gas- and particulate-phase of the polycyclic aromatic hydrocarbons in a metropolitan region in Brazil

A risk assessment and a source apportionment of the particulate- and gas-phase PAHs were conducted in a high vehicular traffic and industrialized region in southeastern Brazil. Higher concentrations of PAHs were found during summer, being likely driven by the contributions of PAHs in the vapor phase caused by fire outbreaks during this period. Isomer ratio diagnostic and Principal Component Analysis (PCA) identified four potential sources in the region, in which the Positive Matrix Factorization (PMF) model confirmed and apportioned as gasoline-related (31.8%), diesel-related (25.1%), biomass burning (23.4%), and mixed sources (19.6%). The overall cancer risk had a tolerable value, with ∑CR = 4.6 × 10^-5, being ingestion the major via of exposure (64% of the ∑CR), followed by dermal contact (33% of the ∑CR) and inhalation (3%). Mixed sources contributed up to 45% of the overall cancer risk (∑CR), followed by gasoline-related (up to 35%), diesel-related (up to 15%), and biomass burning (up to 10%). The risk assessment for individual PAH species allowed identifying higher CR associated with BaP, DBA, BbF, BaA, and BkF, species associated with gasoline-related and industrial sources. Higher risks were associated with PM_2.5-bound PAHs exposure, mainly via ingestion and dermal contact, highlighting the need for measures of mitigation and control of PM_2.5 in the region.

Removing BaP from soil by biochar prepared with medicago and corn straw using batch and solid-phase extraction method

Low-cost materials with a highly efficient adsorption capability prepared from corn straw and medicago (abbreviated to CB and MB), which can effectively remove benzo(a)pyrene (BaP) from contaminated soil, were prepared at a temperature of 350 °C under limited-oxygen conditions. The appearance traits, contents of C, H, N and functional group types of CB and MB were obtained by SEM, elemental analysis and FT-IR. Through the batch method, it was found that the adsorption of BaP by CB and MB was in accordance with pseudo-secondary kinetics because the correlation coefficients are 0.855 with CB and 0.948 with MB, respectively, and the maximum adsorption capacity in the fitting (CB: 78.2 mg kg^-1, MB: 88.8 mg kg^-1) was consistent with the actual measurement (CB: 79.8 mg kg^-1, MB: 89.3 mg kg^-1). Freundlich and Langmuir equations can well describe the isothermal adsorption data of CB and MB due to the correlation coefficients all being greater than 0.87. Soil samples treated with ASE were separated by solid-phase extraction (SPE) with different biochar contents in packed columns. It was found that the contributions of CB and MB to the removal of BaP increased from 58.5% and 60.4% to 80.6% and 82.1%, respectively, which could effectively reduce BaP in polluted soil.

Exposure to polycyclic aromatic hydrocarbons and the associations with oxidative stress in waste incineration plant workers from South China

Waste incineration is one of the most common emission sources of polycyclic aromatic hydrocarbons (PAHs), causing potential occupational exposure in waste incineration workers. However, relative investigations among waste incineration plant workers are still very limited, particularly in China. Therefore, we collected urine specimens from 77 workers in a waste incineration plant as the exposed group, and 101 residents as the control group in Shenzhen, China. Nine mono-hydroxylated PAH metabolites (OH-PAHs) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were measured, and their internal relationships were explored. The urinary levels of most OH-PAHs and 8-OHdG in the exposed group exhibited high levels versus another group (p < 0.05). We found negative associations between OH-PAHs and 8-OHdG in the control group (p < 0.05), while most of OH-PAHs were not associated with 8-OHdG in the exposed group, which indicated that the exposure to waste incineration could enlarge the level of individual oxidative stress damage. Nevertheless, PAHs were less likely to trigger obvious health risks in exposed workers through estimation of human intake and exposure risks. This study provides a reference for occupational PAH exposure and strengthen the need of health monitoring among incineration workers.

Characteristics of PM and PAHs emitted from a coal-fired boiler and the efficiencies of its air pollution control devices

Sampling and analysis of filterable particulate matter (FPM), FPM_2.5, condensable particulate matter (CPM), polycyclic aromatic hydrocarbons (PAHs), sulfur oxides (SO_x), and nitrogen oxides (NO_x) emitted from a coal-fired boiler equipped with selective catalytic reduction (SCR)+ electrostatic precipitator (ESP) + wet flue gas desulfurization (WFGD) + wet electrostatic precipitator (WESP) as air pollution control devices (APCDs) are conducted. The results show that NO_x concentration emitted from the coal-fired boiler is 56 ± 2.17 ppm (with the NO_x removal efficiency of 47.2%), which does not meet the best available control technology (BACT) emission standard (≤ 30 ppm). On the other hand, the WFGD adopted has a good removal efficiency for SO_x and HCl. Both SO_x and HCl emission concentrations are < 1 ppm, and removal efficiencies are > 99%. The FPM and FPM_2.5 emitted from the coal-fired boiler are 0.9 ± 0.06 mg/Nm³ and < 0.09 ± 0.006 mg/Nm³, respectively. The overall removal efficiency of FPM achieved with ESP+WFGD+WESP+MGGH is 99.98%. However, high concentration of CPM (37.4 ± 6.3 mg/Nm³) is measured, which is significantly higher than FPM and FPM_2.5. The concentrations of 27 PAHs at the WESP inlet and stack are measured as 667 ng/Nm³ and 547 ng/Nm³, respectively while the removal efficiencies of gas- and solid-phase PAHs are 9% and 58%, respectively. The results show that APCDs adopted are not effective in removing PAHs (only 18%), and gas-phase PAHs contribute the most in the total PAH emission. In addition, the benzo(a)pyrene equivalent (BaP_eq) concentration emitted from the stack is 28.8 ng-BaP_eq/Nm³, and most of it is contributed by 4-6 ring PAHs with high toxic equivalent factors (TEFs). Furthermore, the emission factors of air pollutant emitted from coal-fired boilers equipped with different combinations of APCDs are compiled and compared. The results show that except for CPM and NO_x, the emission factors of air pollutant calculated for this coal-fired boiler are lower if compared with other studies.Implications: Primary particles discharged from coal-fired processes include filterable particulate matter (FPM) and condensable particulate matter (CPM). PM_2.5 emissions would be greatly underestimated if CPM is ignored. Polycyclic aromatic hydrocarbons (PAHs) are semi-volatile organic compounds (SVOCs) formed by two or more fused benzene rings. PAHs have attracted much public attention because of toxicity and carcinogenicity. This study selects one coal-fired boiler with the best available control technology (BACT) to simultaneously measure the concentrations of PM, PAHs, and gaseous pollutants at the inlet and outlet of air pollution control devices (APCDs) to understand the efficacy of APCDs adopted and pollutant emission intensity.

A comprehensive review of domestic-open waste burning: recent trends, methodology comparison, and factors assessment

Open burning is a waste management practice performed by many people worldwide, especially in developing countries. Lack of detailed data of open burning practices may lead to a misinterpretation during data analysis, especially when estimating global/local emissions and assessing risks. This study presents a comprehensive review of current research trends, methodological assessments, and factors behind open waste burning practices from published literature. This review used systematic methods such as PRISMA 2020 methodology, a bibliometric approach, and qualitative content analysis to determine and assess 84 articles related to open burning. The results show that environmental risks and emission factors related to open burning incidents at the landfill or residential level are preferable topics that will be rising in the years to come. Coupling methods such as a transect-based approach with a questionnaire survey and mobile-static plume sampling to determine the activities and incidents as baseline data for risk assessment will help researchers gain a robust dataset of open burning emission inventory. In addition, it was found that environmental knowledge and awareness levels influence open burning practices, thereby opening up opportunities for future research.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10163-022-01430-9.

Air Quality in Africa: Public Health Implications

This review highlights the importance of air quality in the African urban development process. We address connections between air pollution and (a) rapid urbanization, (b) social problems, (c) health impacts, (d) climate change, (e) policies, and (f) new innovations. We acknowledge that air pollution levels in Africa can be extremely high and a serious health threat. The toxic content of the pollution could relate to region-specific sources such as low standards for vehicles and fuels, cooking with solid fuels, and burning household waste. We implore the pursuit of interdisciplinary research to create new approaches with relevant stakeholders. Moreover, successful air pollution research must regard conflicts, tensions, and synergies inherent to development processes in African municipalities, regions, and countries. This includes global relationships regarding climate change, trade, urban planning, and transportation. Incorporating aspects of local political situations (e.g., democracy) can also enhance greater political accountability and awareness about air pollution.

Emission of PM2.5-Bound Polycyclic Aromatic Hydrocarbons from Biomass and Coal Combustion in China

Field measured PAH emissions from diverse sources in China are limited or even not available. In this study, the PM2.5-bound PAH emission factors (EFs) for typical biomass and coal combustion in China were determined on-site. The measured total PAH EFs were 24.5 mg/kg for household coal burning, 10.5–13.9 mg/kg for household biofuel burning, 8.1–8.6 mg/kg for biomass open burning, and 0.021–0.31 mg/kg for coal-fired boilers, respectively. These EF values were compared with previous studies. The sources profiles of PAHs for four sources were developed to use in chemical mass balance receptor modelling. BaP equivalent EFs (EFBaPeq) were calculated to evaluate PAH emission toxicity among different combustion sources, and were 6.81, 2.94–4.22, 1.59–3.62, and 0.0006–0.042 mg/kg for those four types of sources, respectively.

Leaching characteristics and hazard evaluation of bottom ash generated from common biomedical waste incinerators

India has more than 202 biomedical waste incinerators, however, knowledge on the chemical characteristics of incinerator ash is lacking. The objective of this study was to evaluate the lecahablility characteristics of bottom ash and to study the levels of incineration by-products viz. polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). Bottom ash samples from 13 common biomedical waste treatment facilities (CBMWTF) were colleted and subjected to leachig test, sequential extraction procedure (SEP) and PAHs and PCBs analysis. Among metals, cadmium, chromium, manganese, lead and zinc were found higher than the regulatory limits indicating its hazardous nature. SEP showed that substantial fraction of Cd (30%) and Zn (25%) were associated with leachable fractions, whereas metals such as Cr, Fe, Mn, and Ni were mainly associated with reducible, organics and residual fractions. Concentrations of USEPA 16 priority PAHs ranged between 0.17-12.67 mg kg^-1 and the total toxic equivalents (TEQ) were in the range of 0.9-421.9 ng TEQ/g. PAHs with 4-rings dominated all the samples and accounted for 68% to total PAHs concentrations. Concentration of Σ₁₉ PCB congeners ranged from 420.4 to 724.3 µg kg^-1. PCBs homologue pattern was dominated by mono- to tetra chlorinated congeners (60-86%). The findings indicate the need for segregation of plastics from biomedical waste, improvement of combustion efficiency, and efficient air pollution control devices for the existing incinerators in CBMWTFs.

Century-long record of polycyclic aromatic hydrocarbons from tree rings in the southeastern Tibetan Plateau

Limited studies have been carried out on the historical variations of atmospheric polycyclic aromatic hydrocarbons (PAHs), especially in remote regions of the world. In this study, century-long record of PAHs (1916-2018) were reconstructed from tree rings in the remote southeastern Tibetan Plateau (TP). The total concentrations of 15 PAHs varied from 27.5 to 6.05 × 10² ng/g dry weight (dw), with a mean value of 1.40 × 10² ng/g dw. Higher levels of PAHs were observed during World War Ⅱ and the Peaceful Liberation of Tibet, and increasing trends were observed starting from rapid industrialization in India. Both the isomer ratios and the positive matrix factorization model results indicated biomass and coal combustion were the dominant sources of PAHs. The carcinogenic risk of PAHs to local residents was assessed, which might have been negligible in most past periods and lower than in other regions of the world. Nevertheless, since the beginning of the 21st century, the cancer risk has been increasing year by year, indicating more actions are needed to reduce emissions of PAHs. This study provides an idea for reconstructing the pollution history of PAHs at the global scale.

A review of the main strategies used in the interpretation of similar chemical profiles yielded by receptor models in the source apportionment of particulate matter

Receptor models have been widely used for the source apportionment of airborne particulate matter. However, in the last 10 years, the use of factor analysis-based models, such as PMF and UNMIX, has increased significantly. The results yielded by these models must be interpreted by users who must know all variables influencing the modeling, and without this knowledge, the probability of incorrect interpretation of the source profiles may increase, especially when two or more sources have similar chemical profiles. Concerning the quality of data, this work shows that a broad characterization of PM composition, including inorganic, organic, and mineralogical species can improve this process, avoiding misinterpretation and the attribution of mixed or unidentified sources. This work aims to provide readers with some answers for a question often risen during source apportionment studies: Which source markers should be used for better separation and interpretation of source profiles? This review shows there is no right answer for this because different strategies can be used for this purpose. Therefore, this review aims to compile and highlight qualitatively the key strategies already used by several experienced receptor models users, combining the use of inorganic, organic, and mineralogical markers of PM for better separation and interpretation of the profiles yielded by receptor models. Also, this work presents a compilation in tables of the main chemical species reported in the literature as markers for interpreting the source profiles.

Removal and transformation of unconventional air pollutants in flue gas in the cement kiln-end facilities

To understand the removal and transformation behaviors of unconventional air pollutants (polycyclic aromatic hydrocarbons, heavy metals and carbonyl compounds) in the flue gas in cement kiln-end facilities, including SP boiler, a slide stream SCR-DeNO_x system, raw mill and baghouse filter, the gas and particle matter samples at the inlets and outlets of each kiln-end installation were collected and the contents of the unconventional air pollutants were measured. The results showed that the concentrations of the polycyclic aromatic hydrocarbons (PAHs) in particulate and gas-phase, heavy metals in the particulate matter were 17.5 μg m^-3, 48.7 μg m^-3 and 3113.1 μg m^-3 at the inlet of the SP boiler, and decreased to 0.6 μg m^-3, 17.7 μg m^-3 and 39.7 μg m^-3, respectively, while the concentrations of carbonyl compounds in gas-phase increased from 1988.5 μg m^-3 to 2844.5 μg m^-3 after flue gas successively passed through the kiln-end facilities. The cooling of flue gas and the precipitation of coarse particulate matter in the SP boiler resulted in a significant decrease of PAHs concentration in both gas-phase and particulate-phase, as well as the heavy metal concentration in the particulate-phase, while the SP boiler hardly had any influence on the removal and transformation of carbonyl compounds. Grinding and heat exchange in the raw mill accelerated the volatilization of compounds with the low boiling point in the raw meal, which increased concentrations of gas-phase PAHs and carbonyl compounds. When flue gas passed through the baghouse filter, almost all particulate-phase PAHs, heavy metals and most of the gas-phase PAHs, were removed while the carbonyl compounds concentration maintained unchanged. Furthermore, some portion of gas-phase PAHs and carbonyl compounds were removed by the SCR-DeNO_x system.

Magnetic polyamidoamine dendrimer grafted with 4-mercaptobenzoic acid as an adsorbent for preconcentration and sensitive determination of polycyclic aromatic hydrocarbons from environmental water samples

Polyamidoamine dendrimer decorated Fe₃O₄ magnetic nanoparticles was synthesized and grafted with 4-mercaptobenzoic acid (4-MBA). The resulting material was utilized to develop an effective magnetic solid phase extraction method in combination with high performance liquid chromatography for trace determination of polycyclic aromatic hydrocarbons including phenanthrene (PHE), anthracene (ANT), fluoranthene (FLT), pyrene (PYR) and benzo(a)pyrene (BaP). The MNPs@G3.0@4-MBA exhibited to be an efficient extracting medium due to the existence of terminal benzene ring groups, the internal pores, and strong hydrophobic interactions and π-π interactions. The experiments demonstrated that the proposed method possessed excellent linearity in the concentration range of 0.1-300 μg L^-1 with correlation coefficients (R) larger than 0.997, and the limits of detection (LODs, S/N = 3) according to the ratio of signal to noise equal to three of PHE, ANT, FLT, PYR and BaP were 0.014 μg L^-1, 0.032 μg L^-1, 0.055 μg L^-1, 0.027 μg L^-1 and 0.039 μg L^-1, respectively. The proposed method was applied to real water samples and the spiked recoveries were over the range of 92-99%. The results showed that the method earned good repeatability and high sensitivity, and the as-prepared materials were stable and reusable, which displayed that the proposed method would have a wonderful application prospect.

Construction of a regional inventory to characterize polycyclic aromatic hydrocarbon emissions from coal-fired power plants in Anhui, China from 2010 to 2030

The infrastructures of coal-fired power plants in China have changed significantly since 2010, but the magnitude and characteristics of polycyclic aromatic hydrocarbon (PAH) emissions remain to be updated. In the present study, a unit-based PAH emission inventory for coal-fired power plants between 2010 and 2017 was constructed for Anhui Province, China. Atmospheric PAH emissions from pulverized coal (PC) and circulating fluidized bed (CFB) units in 2017 were 8600 kg and 7800 kg, respectively. The emission rates and intensities for CFB units (7.2 kg ton^-1 and 2.1 kg MW^-1) were significantly higher than those for PC units (1.1 kg ton^-1 and 0.19 kg MW^-1), primarily because CFB boilers were operated at lower combustion temperatures and poor combustion conditions compared to PC boilers. The distribution patterns of PAH emissions across different age groups largely reflected the time periods for constructing coal-fired units in Anhui and for the transition of small units to large ones. The accomplishment of ultralow emission technologies and phase-out of outdated coal-fired units were responsible for the decreasing trend of PAH emissions between 2012 and 2017. The warmer summer in 2013 and 2017 and colder winter in 2011 compared to other years probably caused increased use of air conditioners, resulting in increased electricity consumption and PAH emissions. Future PAH emissions would decrease by 45-57% during 2017-2030, benefitting from power plant fleet optimization, i.e., phasing out outdated coal-fired units and replacing them with large ones. With the best available optimized power plant fleets and end-of-pipe control measures accomplished in Anhui's CFPPs, PAH emissions in 2030 would potentially be reduced by 56-65%.

Coordinated effects of air pollution control devices on PAH emissions in coal-fired power plants and industrial boilers

Coal-fired power plants are important sources of polycyclic aromatic hydrocarbon (PAH) emissions in the world. The effects of various air pollution control devices (APCDs) on PAH emissions were investigated by analyzing samples from inlets and outlets of APCDs in six coal-fired power plants (A-F) and two coal-fired industrial boilers (G and H). The APCDs were electrostatic precipitators (ESPs), wet flue gas desulfurization systems (WFGDs), and wet ESPs (WESPs). The PAH congener patterns for the coal-fired plants were similar. Gas-phase PAHs were dominant in flue gases, and the most abundant PAH was naphthalene. Three- and four-ring PAHs were dominant in fly ash. Positive correlations were found between the PAH and total organic carbon contents of fly ash (R² 0.87) and slag (R² 0.92). Plants D-F, equipped with low-low-temperature ESPs (LLT-ESPs) and WESPs discharged the lowest PAHs. Circulating water was an important source of PAHs in the desulfurization except in plant A, which used desalinated seawater rather than circulating water in the desulfurization process. WESPs decreased PAH concentrations by an average of 20.67%, which can be spread to other plants to reduce PAHs.

Primary Carbonaceous Particle Emission from Four Power Plants with Ultralow Emission in China

Particulate matters (PMs) were collected in stacks from two types of ultralow emission coal-fired power plants by a heated electrical low-pressure impactor (HT-ELPI⁺), including ultralow emission pulverized combustion technology boilers (ULPCBs) and ultralow emission circulating fluidized bed boilers (ULCFBs). The characteristics of organic carbon (OC) and elemental carbon (EC) in size-resolved particles were analyzed. The ultralow emission technologies significantly decreased the mass concentrations of the carbonaceous content, and the emission concentrations of OC and EC ranged from 5.64 to 17.9 μg/m³ for ULPCBs and from 0.57 to 1.85 μg/m³ for ULCFBs. However, the number concentration of particles was not significantly decreased in the four ultralow emission power plants. The OC in the particle emission of ULPCBs presents a bimodal size distribution with the particle size, while three successive unimodal distributions were observed in the ULCFB emission. Compared to ULPCBs, much more char-EC and soot-EC condensed in the particles, which were collected from ULCFBs. Furthermore, the char-EC/soot-EC in the particle fractions of ULPCBs characterized by the "V" type with the sequence of PM_1.0 > PM_2.5-10 > PM_1.0-2.5, differing from the PM_1.0 > PM_1.0-2.5 > PM_2.5-10 of ULCFBs. The ratios of OC/EC in the stacks from two types of boilers did not show obvious variations in particle size distributions, and the mean OC/EC was far higher than those for non-ultralow emission power plants. Considering the impact of OC₁, OC₄, and EC₁, the ratio of high-temperature organic carbon (HTOC, defined as OC₂ + OC₃) and soot-EC was studied. The HTOC/soot-EC increased with the increase of RH in the stack, and the highest HTOC/soot-EC values were obtained from ULPCBs (33.0% (PM_1.0), 11.4% (PM_1.0-2.5), and 23.9% (PM_2.5-10)). Meanwhile, strong correlations (0.69-0.85, p < 0.001) between HTOC and soot-EC were obtained, implying that HTOC and soot-EC probably simultaneously condensed in the purification equipment.

Review on polycyclic aromatic hydrocarbons (PAHs) migration from wastewater

Rapidly increasing global population and increased civilization has increased burden on potable water resources and results in larger volumes of wastewater. Physical wastewater management techniques has advanced for domestic usage and commercial effluent new conceptions about imminent wastewater treatment have been acclaimed for highly carcinogenic polycyclic aromatic hydrocarbon (PAH) compounds. The present review study emphasis on the assessment of several accessible PAHs treatment methods used in wastewater management. The elementary principles, contextual remediation mechanisms and recent development in PAHs removal practices have also been precisely explained. The comprehensive information regarding sources, dispersal, classification, physicochemical properties, PAHs toxicity for humans and aquatics life, conventional treatment procedures, and advanced oxidation processes specified can assist us to identify the PAHs problem and their intensity. The performance evaluation of different removal techniques are discussed in details and found that highest PAHs' reduction for 5-or 6-ring (99%,) while 3-ring (79% reduction) with oxidant dose of 1.64 mL/L using titanium catalyst. In case of MWTPs, with secondary techniques, the average removal efficiency found in the range of 81.1-92.9% while for AOPs are 32-99.3%. Here, overall yield through AOPs most suitable if process used with some catalyst enhanced the yield as well and suitable for high ring as well as low ring PAHs. Among various processes, advanced oxidation and catalytic oxidation processes are the most valuable and promising techniques for PAHs removal. Based on the given evidences, the AOPs coupled with catalysts have been decided as the most competent design for wastewater PAHs treatment.

Air Pollution Measurements and Land-Use Regression in Urban Sub-Saharan Africa Using Low-Cost Sensors—Possibilities and Pitfalls

Air pollution is recognized as the most important environmental factor that adversely affects human and societal wellbeing. Due to rapid urbanization, air pollution levels are increasing in the Sub-Saharan region, but there is a shortage of air pollution monitoring. Hence, exposure data to use as a base for exposure modelling and health effect assessments is also lacking. In this study, low-cost sensors were used to assess PM2.5 (particulate matter) levels in the city of Adama, Ethiopia. The measurements were conducted during two separate 1-week periods. The measurements were used to develop a land-use regression (LUR) model. The developed LUR model explained 33.4% of the variance in the concentrations of PM2.5. Two predictor variables were included in the final model, of which both were related to emissions from traffic sources. Some concern regarding influential observations remained in the final model. Long-term PM2.5 and wind direction data were obtained from the city’s meteorological station, which should be used to validate the representativeness of our sensor measurements. The PM2.5 long-term data were however not reliable. Means of obtaining good reference data combined with longer sensor measurements would be a good way forward to develop a stronger LUR model which, together with improved knowledge, can be applied towards improving the quality of health. A health impact assessment, based on the mean level of PM2.5 (23 µg/m3), presented the attributable burden of disease and showed the importance of addressing causes of these high ambient levels in the area.

Reduction of polycyclic aromatic hydrocarbons (PAHs) emission from household coal combustion using ferroferric oxide as a coal burning additive

Household coal combustion is identified to be the second largest emission source of polycyclic aromatic hydrocarbons (PAHs) in China. In this study, ferroferric oxide (Fe₃O₄) was used as a coal burning additive to reduce PAHs emission from coal combustion in a household coal stove. The results showed that Fe₃O₄ participated in the coal combustion process. The addition of Fe₃O₄ reduced the release of PAHs during the coal combustion process, and could improve the residence capacity of ash residue to these PAHs. Toxic equivalent quantity (TEQ) of PAHs in flue gas from combustion of coal mixed with Fe₃O₄ was less than that from the raw coal combustion. For a typical combustion temperature of 850 °C, the TEQ of PAHs for the mixture of coal and 2.0 wt% Fe₃O₄ decreased 21.98% compared to that for the raw coal. The abundant active surface oxygen species originated from the phase transformation of iron oxides probably accelerated the cracking of PAHs, and hence led to the reduction of PAH emissions and their TEQ. The study could help to develop new technology for reduction of PAHs emission from household coal combustion.

Reduction of polychlorinated naphthalenes (PCNs) emission from municipal waste incinerators in Taiwan: Recommendation on control technology

Emission factor and removal efficacy of PCNs are evaluated via the flue gas sampling of two MWIs equipped with different air pollution control devices (APCDs) in Taiwan. MWI-A is equipped with ESP, wet scrubber (WS) and selective catalytic reduction (SCR), while cyclone (CY), semi-dry absorber (SDA), activated carbon injection (ACI) and baghouse (BH) are employed in MWI-B. The average concentrations of PCNs measured at stacks of MWI-A and MWI-B are 2.1 ng Nm^-3 (0.218 pg TEQ Nm^-3) and 23.2 ng Nm^-3 (0.425 pg TEQ Nm^-3), respectively. The emission factors of PCNs calculated from feeding rates of waste and stack sampling results range from 6.7 to 6.95 μg t^-1 (0.790-1.45 ng TEQ t^-1). PCNs are formed in ESP via chlorination, while SCR and SDA + ACI + BH are effective in removing PCNs with the overall efficacies of 97.6% and 94.3%, respectively. PCN removal efficiencies achieved with SCR and SDA + ACI + BH increase as chlorination level increases. Specifically, around 72% and 82% of Mono-CN are removed by SCR and SDA + ACI + BH, respectively. The removal efficacies of other homologues achieved with SCR are consistently high (96-100%). Dominances of Mono-to Tri-CNs in scrubbing liquid collected from WS and higher removal efficacies of these homologues achieved with WS + ESP compared with ESP alone indicate that WS can capture low chlorinated PCNs to some extent. The results suggest that CY + SDA + ACI + BH should be equipped in MWI for effective removal of PCNs, while ESP, WS and SCR should be utilized with precaution to eliminate PCNs formation and enhance the PCNs removal efficiency.

Emission characteristics and potential toxicity of polycyclic aromatic hydrocarbons in particulate matter from the prebaked anode industry

The emission factors (EFs) and source profiles of polycyclic aromatic hydrocarbons (PAHs) in particulate matter (PM₁₀ and PM_2.5) from the prebaked anode industry were studied to fill the knowledge gap and provide data for emission inventory and source resolution. In 2018, three prebaked anode plants were selected in Central China, each having one calcining chimney as well as one baking chimney, and then 92 samples were collected from the stack gas of the six chimneys. The results of the study are as follows. (1) PM₁₀ and PM_2.5 from the prebaked anode industry contained 37-42% water-soluble ions, 16-20% elements, 11-17% organic carbon, and 9.2-14% elemental carbon. (2) The EFs for PAHs of PM₁₀ and PM_2.5 were 1146.1 ± 899.7 and 866.2 ± 1179.8 mg/(t aluminum produced), respectively. The EF for BaP was seven times lower than that given by the European Environment Agency (EEA), whereas those of BbF, BkF, and IcdP were 2-13 times higher than those given by the EEA. (3) Seven diagnostic ratios for PAHs, including Ant/(Ant+Phe), Flua/(Flua+Pyr), BaA/(BaA + Chr), IcdP/(IcdP+BghiP), Flu/(Flu+Pyr), Phe/Ant and BaA/Chr were discussed. Just by diagnostic ratio, it is hard to precisely distinguish between calcining and baking in prebaked industry. (4) The toxic equivalence of PMs in the baking stack gas in the prebaked anode industry was five times higher than that in the calcining stack gas, and PM_2.5 showed higher potential toxicity risk than PM₁₀.

The bibliometric analysis and review of dioxin in waste incineration and steel sintering

Facing the common treatment problems of dioxin whose major sources come from waste incineration and steel sintering, we handled a massive literature dataset from the Web of Science database and analyzed the research hotspot and development trend in this field in the past 40 years by bibliometric method. The result indicates that the field of dioxins generated from waste incineration and steel sintering has entered a stage of rapid development since 1990. China occupies a leading position in terms of comprehensive strength with the largest publications output as well as a greater influence in recent years. The most productive institutions and journals are Zhejiang University and Chemosphere, respectively. In addition, the most commonly used keywords in statistical analysis are "fly ash," "emission control," "risk assessment," "congener profile," "formation mechanisms," "sources," "catalysis," and "inhibition," which reflects the current main research direction in this field. The similarities and differences of dioxins generated in waste incineration and steel sintering are reviewed in this paper, which will provide guidance for the future research.

Ultrasensitive detection of polycyclic aromatic hydrocarbons in coastal and harbor water using GC-APLI-MS

Polycyclic aromatic hydrocarbons (PAH) are a group of ubiquitous environmental pollutants among which some compounds show carcinogenic properties. The emission of PAH from anthropogenic and natural sources to the aquatic environment demands monitoring. In this study, ten different surface water samples were collected and analyzed for 48 different PAH compounds by gas chromatography-atmospheric-pressure-laser-ionization coupled to mass spectrometry (GC-APLI-MS) after liquid-liquid extraction. Results varied from 9.22 ng/L for fluoranthene in harbor water to 0.01 ng/L for 4-methylchrysene in Rhine river water. Overall low PAH concentrations were found in the samples. Toxic equivalent (TEQ) calculations were used to assess the potential environmental impact of the analyzed compounds. The results showed higher concentrations and TEQ for the samples from harbors in comparison to riverine and estuarine sampling locations. Suspected target analysis indicated the occurrence of alkylated PAH in the surface water samples.

Landfill Impacts on the Environment— Review

Waste management (WM) is a demanding undertaking in all countries, with important implications for human health, environmental preservation, sustainability and circular economy. The method of sanitary landfilling for final disposal of waste remains a generally accepted and used method but the available scientific evidence on the waste-related environmental and health effects is not conclusive. Comparative studies of various WM methods (landfilling, incineration, composting etc.) show that among the municipal solid waste (MSW) treatment and disposal technological options, sanitary landfilling or open dumping is popular in most countries because of the relative low cost and low-technical requirement. The European Union (EU) Directive on waste landfills has introduced specific goals for reducing the volume of disposed waste and very strict requirements for landfilling and landfill sites. Evaluation of the impact of landfills on the environment is a crucial topic in the literature and has received increased attention recently, given growing environmental concerns. The main goal of this survey was to conduct a comprehensive assessment of possible impacts of MSW landfills on the environment. The main conclusion of the overall assessment of the literature is that the disposal of MSW in landfills entails a number of environmental risks but with respect to the current situation and rich style of living adopted in industrially developed countries, the idea of WM systems functioning without landfilling—at least in the foreseeable future within one generation—seems to be somewhat unreal. The results also provided important information of landfills as a source of environmental risk. Results of this research may have an important impact on landfill management and the disposal of waste. From the literature review, it is evident that even if high levels of waste avoidance, reuse and recycling are achieved, some waste materials will always need to be forwarded for disposal.

Polycyclic aromatic hydrocarbon (PAHs) geographical distribution in China and their source, risk assessment analysis

In China, the huge amounts of energy consumption caused severe carcinogenic polycyclic aromatic hydrocarbon (PAHs) concentration in the soil and ambient air. This paper summarized that the references published in 2008-2018 and suggested that biomass, coal and vehicular emissions were categorized as major sources of PAHs in China. In 2016, the emitted PAHs in China due to the incomplete combustion of fuel was about 32720 tonnes, and the contribution of the emission sources was the sequence: biomass combustion > residential coal combustion > vehicle > coke production > refine oil > power plant > natural gas combustion. The total amount of PAHs emission in China at 2016 was significantly decreased due to the decrease of the proportion of crop resides burning (indoor and open burning). The geographical distribution of PAHs concentration demonstrated that PAHs concentration in the urban soil is 0.092-4.733 μg/g. At 2008-2012, the serious PAHs concentration in the urban soil occurred in the eastern China, which was shifted to western China after 2012. The concentration of particulate and gaseous PAHs in China is 1-151 ng/m3 and 1.08-217 ng/m3, respectively. The concentration of particle-bound PAHs in the southwest and eastern region are lower than that in north and central region of China. The incremental lifetime cancer risk (ILCR) analysis demonstrates that ILCR in the soil and ambient air in China is below the acceptable cancer risk level of 10-6 recommended by US Environmental Protection Agency (EPA), which mean that there is a low potential PAHs carcinogenic risk for the soil and ambient air in China.

Emission characteristics of parent and halogenated PAHs in simulated municipal solid waste incineration

With a self-designed small-scale waste incinerator, emission behaviors of parent and halogenated polycyclic aromatic hydrocarbons (PAHs and HPAHs) were simulated and visualized. According to our results, the 2-3 ring PAHs have higher emission factors (EFs) than those of the 4-6 ring PAHs during waste incineration. The EFs of individual HPAHs are comparable in all incineration products. Overall, the EFs of Ʃ₁₆PAH and Ʃ₃ClPAH decreased in the order of gas > bottom ash > particle > fine particle while the EF order for Ʃ₆BrPAH is bottom ash > particle > gas > fine particle. Based on qualitative observation, the size distributions of Σ₁₆PAH, Σ₃ClPAH, and Σ₆BrPAH were characterized by trimodal peaks. Coagulation of fine particles in air may lead to enrichment of target compounds in the coarse particle fraction. The gas-particle partition did not reach theoretical equilibrium and most PAHs and HPAHs were absorbed inside the organic carbon. Estimated mass emission of target compounds in Shenzhen suggests that the gaseous phase from MSW incineration is the major contributor to the urban environment. However, automotive emissions contribute more to urban air pollution than MSW incineration in Shenzhen. Generally, compared with other real waste treatment, waste incineration is a more efficient method for waste-to-energy recovery and produces fewer pollutants, although the resultant carcinogenic substances are never truly harmless.

Atmospheric levels, variations, sources and health risk of PM2.5-bound polycyclic aromatic hydrocarbons during winter over the North China Plain

PM_2.5-bound polycyclic aromatic hydrocarbons (PAHs) during winter 2015 at three urban sites, including Beijing, Tianjin and Shijiazhuang, and one background site (Xinglong) over the North China Plain (NCP) were investigated. The spatial variations of PAHs showed the same trends with PM_2.5 mass concentrations, i.e. the highest PAHs concentrations was in Shijiazhuang, followed by Tianjin, Beijing and the lowest PAHs concentrations was in Xinglong. The diurnal variations of PAHs exhibited PAHs concentrations during nighttime were higher than those during daytime. The dominant species in PAHs were fluranthene and benzo[b + k]fluoranthene, indicating that diesel vehicle emission, coal combustion and biomass burning could be important and potential sources for PAHs over the NCP. There results were supported by diagnostic ratios analysis. But coefficient of divergence analysis showed that a high extent of spatial contrast among four sampling sites, except between Beijing and Tianjin. Analysis of toxicity equivalent quantities (TEQ) and the lifetime excess cancer risk (ECR) from inhalation exposure to PAHs showed that 818, 1517, 5129 and 182 cases per 100,000 people exposed in Beijing, Tianjin, Shijiazhuang and Xinglong, respectively, which were much higher than the threshold value suggested by US-EPA, i.e. 1 case per 100,000 people, and indicating that the NCP suffered from very serious health risk from PAHs, especially in Shijiazhuang.

An experimental and kinetic study of thermal decomposition of phenanthrene

Polycyclic aromatic hydrocarbons (PAHs) have enormous potential hazards. It is necessary for China to propose more internationally stricter standards for PAHs, in order to improve the country's pollutant prevention and control policy system, and ultimately, provide institutional guarantees for implementing PAH emissions prevention and control. In this study, phenanthrene, a typical PAHs generated during municipal solid waste (MSW) to energy system, was applied as a model compound to study the thermal degradation mechanism during the combustion process. Combustion kinetics for the three major gaseous products, including hydrogen, methane, and carbon dioxide, were determined. Experimental results indicated that hydrogen was promoted compared to methane and carbon dioxide during the combustion of phenanthrene, especially in high oxygen concentrations. The apparent activation energy (E_a) of 8.299-11.51, 13.10-23.07, and 9.368-15.29 kJ/mol, pre-exponential factor (A) of 0.219-1.579, 5.034-10.12, and 6.553-15.51 s^-1, and the reaction order (n) of 1.160-1.234, 1.059-1.305, and 1.636-1.774 were obtained for hydrogen, methane, and carbon dioxide, respectively. Research on combustion behavior of phenanthrene and reaction kinetics provides the theoretical basis for the high-temperature removal of PAHs as byproducts during the combustion of MSW in oxygen-rich atmosphere.

Reducing polycyclic aromatic hydrocarbon and its mechanism by porous alumina bed material during medical waste incineration

In this paper, porous alumina was used as an alternative bed material to reduce polycyclic aromatic hydrocarbon (PAH) and monocyclic aromatic hydrocarbons (MAH) emission during medical waste incineration in a fluidized bed combustor (FBC). In order to understand the reduction mechanisms of MAH and PAH, porous alumina, nonporous alumina, and silica sand (180-250 μm and 250-320 μm) were used as the bed materials. In comparison to the silica sand (180-250 μm) bed material, the reduction efficiencies of ∑MAH, ∑PAH and ∑PAH toxic equivalent (TEQ) by porous alumina bed material were in sequence as 91.57%, 58.90% and 73.23% during medical waste incineration under 800 °C. There were three mechanisms for the reduction of PAH under porous alumina bed materials. Firstly, the evolution rate of hydrocarbon was reduced by porous alumina due to its low heat transfer coefficient. Secondly, porous alumina bed materials could absorb more gaseous hydrocarbon and prolong the residence time of hydrocarbon in the diluted zone of FBC due to its higher BET. Lastly, the oxidization of the gaseous hydrocarbon was accelerated by porous alumina due to its catalytic effect. Thus, less light hydrocarbon, MAH and PAH were formed during medical waste incineration. The experimental results also indicated that the heat transmission, catalytic effect, and adsorption effect of porous alumina bed materials respectively accounted for 22.8%, 29.2% and 20.9% of the ∑PAH reduction.

Characteristics and Treatment Methods of Medical Waste Incinerator Fly Ash: A Review

Medical waste incinerator fly ash (MWIFA) is quite different from municipal solid waste incinerator fly ash (MSWIFA) due to its special characteristics of high levels of chlorines, dioxins, carbon constituents, and heavy metals, which may cause irreversible harm to environment and human beings if managed improperly. However, treatment of MWIFA has rarely been specifically mentioned. In this review, various treatment techniques for MSWIFA, and their merits, demerits, applicability, and limitations for MWIFA are reviewed. Natural properties of MWIFA including the high contents of chlorine and carbonaceous matter that might affect the treatment effects of MWIFA are also depicted. Finally, several commendatory and feasible technologies such as roasting, residual carbon melting, the mechanochemical technique, flotation, and microwave treatment are recommended after an overall consideration of the special characteristics of MWIFA, balancing environmental, technological, economical information.

Plant uptake and translocation of contaminants of emerging concern in soil

The advent of industrialization has led to the discovery of a wide range of chemicals designed for multiple uses including plant protection. However, after use, most of the chemicals and their derivatives end up in soil and water, interacting with living organisms. Plants, which are primary producers, are intentionally or unintentionally exposed to several chemicals, serving as a vehicle for the transfer of products into the food chain. Although the exposure of pesticides towards plants has been witnessed over a long time in agricultural production, other chemicals have attracted attention very recently. In this review, we carried out a comprehensive overview of the plant uptake capacity of various contaminants of emerging concern (CEC) in soil, such as pesticides, polycyclic aromatic hydrocarbons, perfluorinated compounds, pharmaceutical and personal care products, and engineered nanomaterials. The uptake pathways and overall impacts of these chemicals are highlighted. According to the literature, bioaccumulation of CEC in the root part is higher than in aerial parts. Furthermore, various factors such as plant species, pollutant type, and microbial interactions influence the overall uptake. Lastly, environmental factors such as soil erosion and temperature can also affect the CEC bioavailability towards plants.

Heavy Exposure of Waste Collectors to Polycyclic Aromatic Hydrocarbons in a Poor Rural Area of Middle China

Manual collection and open-air incineration of waste materials is a common practice in rural regions of China and beyond. Low-temperature combustion of rubber and plastic waste generates high levels of airborne polycyclic aromatic hydrocarbons (PAHs). We investigated ten urinary hydroxylated PAH metabolites (OH-PAHs), the oxidative damage biomarker (8-hydroxy-deoxyguanosine, 8-OHdG), and four serum biomarkers including gamma-glutamyl transferase (GGT) and alanine aminotransferase (ALT) in 41 waste collectors and 122 control subjects residing in the same or a distant rural village in Henan Province. The level of PAH metabolites in urine (median: 17.24 μg/g Cre) was twice that of controls living in the same area without an occupational history involving waste collection (median: 8.16 μg/g Cre) and thrice that of controls living 30 km away (median: 6.07 μg/g Cre). The concentrations of OH-PAHs were positively associated with urinary 8-OHdG levels (β = 0.283, p < 0.05). Serum GGT and ALT were slightly increased in waste collectors. Urinary 8-OHdG levels were similar in one-year and longer-term workers, suggesting that rubber and plastic waste collection/incineration carries a high PAH exposure risk. These data provide solid baseline information, emphasizing the importance of monitoring the long-term health outcomes of waste collectors and changes in exposure patterns associated with rural development and regulation of waste disposal.

Emission characteristics for gaseous- and size-segregated particulate PAHs in coal combustion flue gas from circulating fluidized bed (CFB) boiler

The partitioning behavior of polycyclic aromatic hydrocarbons (PAHs) between gaseous and particulate phases from coal-fired power plants (CFPPs) is critically important to predict PAH removal by dust control devices. In this study, 16 US-EPA priority PAHs in gaseous and size-segregated particulate phases at the inlet and outlet of the fabric filter unit (FFs) of a circulating fluidized bed (CFB) boiler were analyzed. The partitioning mechanisms of PAHs between gaseous and particulate phases and in particles of different size classes were investigated. We found that the removal efficiencies of PAHs are 45.59% and 70.67-89.06% for gaseous and particulate phases, respectively. The gaseous phase mainly contains low molecular weight (LMW) PAHs (2- and 3-ring PAHs), which is quite different from the particulate phase that mainly contains medium and high molecular weight (MMW and HMW) PAHs (4- to 6-ring PAHs). The fractions of LMW PAHs show a declining trend with the decrease of particle size. The gas-particle partitioning of PAHs is primarily controlled by organic carbon absorption, in addition, it has a clear dependence on the particle sizes. Plot of log (TPAH/PM) against logD_p shows that all slope values were below -1, suggesting that PAHs were mainly adsorbed to particulates. The adsorption effect of PAHs in size-segregated PMs for HMW PAHs is more evident than LMW PAHs. The particle size distributions (PSDs) of individual PAHs show that most of PAHs exhibit bi-model structures, with one mode peaking in the accumulation size range (2.1-1.1 μm) and another mode peaking in coarse size range (5.8-4.7 μm). The intensities of these two peaks vary in function of ring number of PAHs, which is likely attributed to Kelvin effect that the less volatile HMW PAH species preferentially condense onto the finer particulates. The emission factor of PAHs was calculated as 3.53 mg/kg of coal burned, with overall mean EF_PAH of 0.55 and 2.98 mg/kg for gaseous and particulate phase, respectively. Moreover, the average emission amount of PAHs for the investigated CFPP was 1016.6 g/day and 371073.6 g/y, respectively.

Size-dependent emission characteristics of airborne parent and halogenated PAHs from municipal solid waste incinerators in Shenzhen, China

Two waste incinerators were selected for investigation of size-dependent emission characteristics of airborne parent and halogenated PAHs (PAHs and HPAHs) and incidence of these pollutants from trash incineration. The concentrations of total PAHs (gas and particles with aerodynamic diameter 0.43-10 μm) in ambient air of Shenzhen incinerators were at the lower end of the global range while those of HPAHs were higher than those of urban air in other studies. High-ring PAHs dominated in PM_2.5 (66%-86%), while low-ring PAHs dominated in PM₁₀ (83%-86%). As for PAHs in gaseous phase, low-ring PAHs were collectively account for 86%-97%. ΣHPAH mainly enriched in coarse particles (>83%). The size distributions of ΣPAH and ΣHPAH were both characterized by bimodal peaks dominate in 9.0-10 μm and subordinate in 4.7-5.8 μm. PAHs and HPAHs enrichment in the coarse particles indicates that particle-bound PAHs and HPAHs from incinerators cannot travel great distances. Model simulation results showed the peak of airborne PAHs and HPAHs occurred in approximate 300 m from incinerator, then their concentrations reduced sharply. The extent of affected areas by municipal solid waste incinerators (MSWIs) seem very large, intensity of impacts can be neglected for the very low level of pollutants. Although waste incineration is perceived as most polluting way to manage waste, our study found the damage from incinerator to be far less than originally feared.