Atmospheric mercury emissions from waste combustions measured by continuous monitoring devices

Atmospheric mercury emissions have attracted great attention owing to adverse impact of mercury on human health and the ecosystem. Although waste combustion is one of major anthropogenic sources, estimated emission might have large uncertainty due to great heterogeneity of wastes. This study investigated atmospheric emissions of speciated mercury from the combustions of municipal solid wastes (MSW), sewage treatment sludge (STS), STS with waste plastics, industrial waste mixtures (IWM), waste plastics from construction demolition, and woody wastes using continuous monitoring devices. Reactive gaseous mercury was the major form at the inlet side of air pollution control devices in all combustion cases. Its concentration was 2.0-70.6 times larger than elemental mercury concentration. In particular, MSW, STS, and IWM combustions emitted higher concentration of reactive gaseous mercury. Concentrations of both gaseous mercury species varied greatly for all waste combustions excluding woody waste. Variation coefficients of measured data were nearly equal to or more than 1.0. Emission factors of gaseous elemental mercury, reactive gaseous mercury, and total mercury were calculated using continuous monitoring data. Total mercury emission factors are 0.30 g-Hg/Mg for MSW combustion, 0.21 g-Hg/Mg for STS combustion, 0.077 g-Hg/Mg for STS with waste plastics, 0.724 g-Hg/Mg for industrial waste mixtures, 0.028 g-Hg/Mg for waste plastic combustion, and 0.0026 g-Hg/Mg for woody waste combustion. All emission factors evaluated in this study were comparable or lower than other reported data. Emission inventory using old emission factors likely causes an overestimation.     

Absorption of atmospheric phenol by various tree species and their tolerance to phenol

To assess the effect of tree planting on atmospheric phenol, a study was made on the absorption of phenol by various tree species and the tolerance of these species to phenol. The absorption rates ranged from 21.3 (camellia) to 129 ng dm^‐2h^‐1 ppb^‐1 (Japanese elm) at 1000 μmol of photons m^‐2 s^‐1, and the absorption rate increased in the following order: coniferous tree species ? evergreen broad‐leaved tree species < deciduous broad‐leaved tree species. When the light intensity was varied, a linear relationship between the phenol absorption rate and the transpiration rate was observed for three tree species. In comparison with the absorption rate estimated from a simplified gas diffusive resistance model, we conclude that phenol is absorbed through the stomata and is metabolized fairly rapidly within the leaf tissue, although the absorption rate is less than the estimated potential absorption rate. At phenol concentrations below 200 ppb, the tree can absorb atmospheric phenol for at least 8 h without any visible foliar injury. Trees in general could act as an important sink for atmospheric phenol at phenol concentrations less than 200 ppb, a concentration about twenty times higher than normal ambient levels.     

Black carbon concentrations in a goods-movement neighborhood of Philadelphia,PA

Communities along the Delaware River in Philadelphia, USA such as Port Richmond, are subject to traffic associated with goods movement to and from port facilities and local industry. Air pollution associated with this traffic poses an environmental health concern in this and other urban areas. Our study measures black carbon (BC) in Port Richmond and examines its relationship to expected sources such as truck traffic. We used a participatory sampling method to conduct 1-min measurements over 8-hour periods at 14 homes, a school and park, during a 4-week period in June 2012. Measurements over 9 sampling days had a 30-min average BC concentration of 1.2 μg m^?3, and a maximum of 12 μg m^?3. Statistical analyses showed some effect of traffic, but greater association between BC concentrations and weather and time of day. BC concentrations varied more by location than by day, and distance to traffic arterials and interstate freeway was a predictor of this variance. While our dataset is limited by number and variety of observations, major findings indicate that BC concentration varies more by location than by day, there is a decrease in median BC concentration with increased distance from an interstate highway, and an expected effect of diesel traffic on average daily BC concentrations. Our findings are an important step towards understanding patterns and determinants of BC concentration in communities colocated with major ports. Our study also demonstrates that participatory methods in air pollution monitoring can help increase awareness of local air pollution levels.     

Characterization of chlorine and heavy metals for the potential recycling of bottom ash from municipal solid waste incinerators as cement additives

Bottom ash is an inevitable by-product from municipal solid waste (MSW) incineration plants. Recycling it as additives for cement production is a promising disposal method. However, the heavy metals and chlorine are the main limiting factors because of the potential environmental risks and corrosion of cement kilns. Therefore, investigating heavy metal and chlorine characteristics of bottom ash is the significant prerequisite of its reuse in cement industries. In this study, a correlative analysis was conducted to evaluate the effect of the MSW components and collection mode on the heavy metal and chlorine characteristics in bottom ash. The chemical speciation of insoluble chlorine was also investigated by synchrotron X-ray diffraction analysis. The results showed that industrial waste was the main source of heavy metals, especially Cr and Pb, in bottom ash. The higher contents of plastics and kitchen waste lead to the higher chlorine level (0.6 wt.%–0.7 wt.%) of the bottom ash. The insoluble chlorine in the MSW incineration bottom ash existed primarily as AlOCl, which was produced under the high temperature (1250°C) in incinerators.

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生活垃圾焚烧飞灰差异性特征对脱氯除盐效果影响研究——以重庆和天津飞灰为例

随着生活垃圾焚烧技术的普及,垃圾焚烧飞灰的资源化利用迫在眉睫,然而飞灰中的高浓度氯元素严重阻碍了其资源化进程.水洗技术作为常用的脱氯除盐技术,得到越来越多的应用,但除氯效果受飞灰自身性质特征影响较大.本研究从重庆和天津采集了两种理化性质具有较大差异的垃圾焚烧飞灰,在对其粒径分布、化学组成、矿物组成、pH值和浸出毒性等基本特征进行分析表征的基础上,采用水洗技术和碳酸化水洗技术对两种飞灰进行了脱氯处理.结果表明,重庆飞灰氯元素的赋存形态包括NaCl、KCl等可溶性氯盐,还含有较高浓度的难溶氯盐(如CaClOH、Friedel盐和Ca₆(CO₃)₂(OH)₇Cl),因此,水洗技术难以达到理想的脱氯效果,氯盐去除率最高为88%.在水洗过程中通入CO₂可以显著降低反应体系的pH值,促进难溶盐的转化和溶解,进而提高飞灰氯盐的去除率.重庆飞灰采用加速碳酸化水洗技术,氯盐去除率最高可达94%.天津飞灰中氯元素主要以可溶性氯盐的形式存在,难溶盐占比很少,因此,水洗技术可以达到较高的脱盐率(96%).采用加速碳酸化技术对天津飞灰进行处理,发现氯盐去除率较纯水洗技术反而有所降低,分析其主要原因可能与加速碳酸化过程中碳酸钙等物质的再沉淀对氯盐的裹挟作用有关.由此可知,飞灰自身性特征尤其是氯盐的赋存形态对于脱氯除盐技术的选择有重要影响.因此,实际资源化利用过程中,可根据飞灰性质来决定预处理手段,从而最大化提升效率和节约成本.     

Detoxification of hexachlorobenzene by dechlorination with potassium-sodium alloy

Dechlorination of hexachlorobenzene (HCB) was achieved by a liquid potassium–sodium (K–Na)-alloy. HCB in a cyclohexane/benzene solution (22 mmol/l, 4.67 g/l as chlorine) was dechlorinated by almost 100% after a 30-min reaction, indicating high reactivity of K–Na alloy and high proton donating power of cyclohexane. Decreasing orders of chlorobenzenes identified after a 15-min reaction, by amount were 1,2,3,4- > 1,2,3,5- > 1,2,4,5- for tetrachlorobenzenes, 1,2,4- > 1,2,3- > 1,3,5- for trichlorobenzenes, and 1,4- > 1,3- > 1,2- for dichlorobenzenes. It was hypothesized that once one chlorine atom in HCB was replaced with a proton, the adjacent chlorine atom to the proton tended to be replaced with another hydrogen atom. A total of 63 PCBs formed via the Wurtz–Fittig reaction were identified as by-products in the sample after a 15-min reaction. Among PCBs found, 2,3^′,4^′,5-tetrachlorobiphenyl, which was a product from 1,2,4-trichlorobenzene formed via the Wurtz–Fittig reaction, was detected in relatively high concentration (48.9 nmol/ml). The sample obtained from a reaction mixture after 30 min contained only 14 PCBs in trace amounts, indicating that the PCBs formed were also further dechlorinated by K–Na alloy. Non-chlorinated compounds––such as methylbenzene, dimethylbenzene, dimer of tetrahydrofuran, and dicyclohexyl (dimer of cyclohexane)––were also identified in the samples. A method using K–Na alloy developed in the present study dechlorinated satisfactorily HCB at room temperature.     

Difference in concentration trends of airborne particulate matter during rush hour on weekdays and Sundays in Tokyo,Japan

Suspended particulate matter (SPM) and fine particulate matter (less than or equal to 2.5 μm: PM_2.5) have generally been decreasing for the last decade in Tokyo, Japan. To elucidate the major cause of this decrease, the authors investigated the different trends of airborne particulates (both SPM and PM_2.5 concentrations) by evaluating comparisons based on the location of the monitoring stations (roadside vs. ambient), days of the week (weekdays vs. Sundays), and daily fluctuation patterns (2002 vs. 2010). Hourly mean SPM and PM_2.5 concentrations were obtained at four monitoring stations (two roadside stations, two ambient stations) in Tokyo, Japan. Annual mean concentrations of each day of the week and of each hour of the day from 2002 to 2010 were calculated. The results showed that (1) the daily differences in annual mean concentration decreased only at the two roadside monitoring stations; (2) the high hourly mean concentrations observed on weekdays during the daily rush hour at the two roadside monitoring stations observed in 2002 diminished in 2010; (3) the SPM concentration that decreased the most since 2002 was the PM_2.5 concentration; and (4) the fluctuation of hourly concentrations during weekdays at the two roadside monitoring stations decreased. A decreasing trend of airborne particulates during the daily rush hour in Tokyo, Japan, was observed at the roadside monitoring stations on weekdays since 2002. The decreasing PM_2.5 concentration resulted in this decreasing trend of airborne particulate concentrations during the daily rush hours on weekdays, which indicates fewer emissions were produced by diesel vehicles.

ImplicationsThe authors compared the trends of SPM and PM_2.5 in Tokyo by location (roadside vs. ambient), days of the week (weekdays vs. Sundays), and daily fluctuation patterns (2002 vs. 2010). The high hourly mean concentrations observed at the roadside location during rush hour on weekdays in 2002 diminished in 2010. The SPM concentration that decreased during rush hour the most was the PM_2.5 concentration. This significant decrease in the PM_2.5 concentration resulted in the general decreasing trend of SPM concentrations during the rush hours on weekdays, which indicates fewer emissions were produced from diesel vehicles.     

Separation and characterization of magnetic fractions from waste-to-energy bottom ash with an emphasis on the leachability of heavy metals

Environmental Science and Pollution Research - Magnetic fractions were extracted from pulverized waste-to-energy (WTE) bottom ashes using a combined wet-dry extraction method. The resulting...     

Metal mobilization from municipal solid waste incineration bottom ash through metal complexation with organic and inorganic ligands

As a first step in the development of ligand-assisted removal of heavy metals from municipal solid waste incineration bottom ash under alkaline conditions, ammonium nitrate, ammonium sulfate, ammonium acetate, ammonium oxalate, ammonium citrate, urea, and mixtures of ammonium salts and urea were examined to find which ligands could promote the leachability of elements, including heavy metals, and which elements could be mobilized through complexation. Ammonium citrate promoted the mobilization of Cr, Cu, Mn, P, Sb, and especially Fe. Ammonium nitrate accelerated Mg leachability significantly. Under the conditions used in this study, counter anions seemed to contribute mainly to the complexation. When a mixture of ammonium citrate and urea was utilized, a coexistence effect appeared on Fe mobilization. Although the correlation analysis of leaching test results showed a strong correlation among Cr, Cu, Fe, Mn, and P, X-ray diffraction analysis partially supported the correlation between Fe and Mn only.     

SARS-CoV-2: a systematic review of indoor air sampling for virus detection

Environmental Science and Pollution Research - In a post-pandemic scenario, indoor air monitoring may be required seeking to safeguard public health, and therefore well-defined methods, protocols,...