Transient mass transfer modeling and simulation of polybrominated diphenyl ethers combustion in incinerators

In this paper, modeling and simulation of combustion process for polybrominated diphenyl ethers in rotary kilns has been investigated. Proper formula is found for the solid wastes which contain polybrominated diphenyl ethers and then combustion process is simulated by considering possible reactions, appropriate dimensions and operating conditions for rotary kiln and necessary relations for reaction rates. The software of MATLAB is used for the simulation. The mass variations for solid waste, outlet gas and its components are calculated during 20 h. The results show that the reaction rate is high for the first 2 h, thus the value of solid waste and oxygen decrease quickly while value of produced gases increases. The mass increase of polychlorinated dibenzo-p-dioxins/furans and polybrominated dibenzo-p-dioxins/furans during the whole time of the process is linear with mild slope but for the other compounds, including steam, carbon dioxide, nitrogen, nitrogen oxide, sulphur dioxide, hydrogen chloride and hydrogen bromine, the slope of variations becomes mild after 3 h. The process becomes steady state almost after 9 h.     

广州不同季风期近地面大气气溶胶中7Be与持久性有机污染物的同步观测

2006年8月-2007年7月,在广州市天河区以每周采集2～3天的采样频率连续12个月采集近地面大气气溶胶样品,同步测定近地面气溶胶中7Be和有机氯农药(OCPs)、多氯联苯(PCBs)、多溴联苯醚(PBDEs)等持久性有机污染物的浓度值.7Be浓度全年平均值为2.59 mBq/m3,最高值出现在5月(8.5 mBq/...     

Potential of groundwater contamination by polybrominated diphenyl ethers (PBDEs) in a sensitive bedrock aquifer (Canada)

It is necessary to understand the presence, movement, and persistence of contaminants in aquifers to develop adequate groundwater protection plans. Fractured bedrock aquifers with thin overburden cover are very sensitive to contamination, and little is known about transport processes from the ground surface to depth in this setting. This study was undertaken to investigate the potential of groundwater contamination by polybrominated diphenyl ethers (PBDEs), which are flame retardants, in a natural fractured bedrock aquifer in Canada proven to be sensitive to contamination. PBDEs, which had not been previously measured in groundwater in detail, were detected in the study aquifer at concentrations greater than those observed in surface-water bodies. Potential sources include manure, septic tanks, and the atmosphere. From this scoping study, it is evident that additional surveys of PBDE concentrations in groundwater are warranted, especially in settings with high potential source concentrations coupled with sensitive aquifers.     

青藏高原中部地区表层土壤中多溴联苯醚的分布特征及影响因素

从青藏高原中部地区采集16个表层土壤样品,并对土壤中42种多溴联苯醚(PBDEs)同系物含量、有机碳含量、矿物含量及土壤粒径分布进行了测试分析,主要研究该区域土壤理化性质对PBDEs的含量、分布及同系物构成的影响。结果表明,PBDEs的含量范围为17.03～298.29 ng/kg(干重),其中低溴联苯醚(1～6溴)占总量的90%以上。研究还发现BDE-3在同系物中含量最高,其次为BDE-2和BDE-1。在所有42个样品中BDE-209均被检出,但平均含量仅为1.25 ng/kg。PBDEs成分组成表明它们主要来源于长距离的大气运移。研究还发现粘土矿物对PBDEs的影响结果与土壤有机碳相似,但影响效果更显著。相关性分析结果表明,在高原地区土壤粘土矿物是影响PBDEs分布的主要因素之一。     

环境中溴系阻燃剂六溴环十二烷的水平及分析进展

六溴环十二烷(HBCDs)是一种添加型溴系阻燃剂,被广泛应用于建筑隔热材料、纺织用品及少量电子产品中。2006年欧盟、国际公约等组织相继停止生产和使用多溴联苯醚后,HBCDs也曾在某些用途中作为替代品使用。在各环境介质中,空气和水体是HBCDs的主要释放空间。点源附近的环境介质中通常能够检测出较高浓度的HBCDs,远高于没有明显点源的地区。工业合成的HBCDs以γ-HBCD异构体为主,大多数生物体内的HBCDs以α-HBCD所占比例最大,可能与化合物结构、环境条件及生物代谢过程等均有关。气相色谱-质谱分析技术对HBCDs有较高的检测灵敏度,但由于HBCDs存在热重排、热降解等现象,使得化合物的异构体分析受限。液相色谱-质谱分析技术弥补了上述缺陷,不但可以区分HBCDs化合物的对映与非对映异构体结构,还可以借助串联质谱(MS/MS)联用技术降低化合物的检出限。文章综述了环境中HBCDs的水平及分析进展,认为在HBCDs的立体结构以及各异构体之间的转化过程和转化条件等方面有很大的探索空间,指出在环境背景区开展HBCDs的环境行为、演变趋势、控制措施及替代技术研究,是今后应该深入研究的领域。     

不同土壤类型多氯联苯土壤残留特征变化分析

为了解多氯联苯（PCBs）在不同土壤类型中的环境分布行为,在“中国网格化农药排放残留模型”的基础上,开发了“中国网格化工业污染物排放残留模型”,并用以对PCBs的研究。进行了PCBs的单源排放和包括城市土壤、旱田、水田、草地、林地及荒地等6种不同类型的土壤残留特征的数值模拟,并对土壤残留特征的变化进行了分析。研究结果表明：PCBs在土壤中的残留浓度与土壤的含气和含水率及其理化性质有关,对排放期末6种类型土壤质量分数与土壤含水体积作相关分析,其相关系数为R=-0.999 5,显著性水平P<0.000 1;PCB同系物在不同土壤层的残留浓度的变化与其理化性质有关。低氯取代的PCB同系物由于其水溶解度高,更容易向深层土壤迁移,其在土壤纵向分布随时间变化较快;随着土壤深度的增加,高氯取代的PCB同系物向深层土壤的扩散能力较弱,其在土壤纵向分布较为稳定。     

Polybrominated diphenyl ethers and its methoxylated analogues in biota and sediment samples from two freshwater lakes in Yangtze River delta

In the present study, sediments and biotas from two freshwater lakes in Yangze delta area were collected and analyzed for polybrominated diphenyl ethers (PBDEs) and methoxylated PBDEs (MeO–PBDEs). The concentrations of PBDEs in sediments and biotas ranged from 0.41 to 5.8 ng/g dry weight and from 4.6 to 100 ng/g lipid weight, respectively, while those of MeO–PBDEs were much lower (sediment: <LOQ-0.014 ng/g dry weight, biota: <LOQ-2.1 ng/g lipid weight). The levels of both brominated substances in sediments and biotas were in the moderate to low range compared with other studies. Different BDE congeners were found between two lakes probably due to the different exogenous sources and metabolic stages. Similar occurrence of higher brominated congeners (e.g., BDE-209) in sediments and biotas indicated sediments as a possible source of PBDEs for biotas. The different contribution of lower and higher brominated congeners between sediments and biotas may be due to the combined effect of biotransformation and bioavailability.     

Influence of transboundary air pollution on air quality in southwestern China

Air pollution is a grand challenge of our time due to its multitude of adverse impacts on environment and society,with the scale of impacts more severe in developing countries,including China.Thus,China has initiated and implemented strict air pollution control measures over last several years to reduce impacts of air pollution.Monitoring data from Jan 2015 to Dec 2019 on six criteria air pollutants(SO2,NO2,CO,O3,PM2.5,and PM1o)at eight sites in southwestern China were investigated to understand the situation and analyze the impacts of transboundary air pollutants in this region.In terms of seasonal variation,the maximum concentrations of air pollutants at these sites were observed in winter or spring season depending on individual site.For diurnal variation,surface ozone peaked in the afternoon while the other pollutants had a bimodal pattern with peaks in the morning and late afternoon.There was limited trans-port of domestic emissions of air pollutants in China to these sites.Local emissions enhanced the concen-trations of air pollutants during some pollution events.Mostly,the transboundary transport of air pollution from South Asia and Southeast Asia was associated with high concentrations of most air pollu-tants observed in southwestern China.Since air pollutants can be transported to southwestern China over long distances from the source regions,it is necessary to conduct more research to properly attribute and quantify transboundary transport of air pollutants,which will provide more solid scientific guidance for air pollution management in southwestern China.     

土壤温室气体昼夜变化及其环境影响因素研究

通过对北京东灵山草地和桦树林土壤气体CO₂,N₂O和CH₄浓度及其排放通量的昼夜连续观测,探讨了生长季节草地和森林土壤温室气体昼夜变化及其环境影响因素。研究表明:1)土壤CO₂排放通量昼高夜低,N₂O排放通量有明显小时尺度波动,但昼夜变化不突出;土壤CO₂和N₂O浓度昼夜变化不明显,且与排放通量波动不一致;土壤是大气CH₄的一个汇,相对厌氧的环境可能有利于土壤吸收CH₄。2)无雨时气温昼夜变化通过影响土壤表层的气体扩散和CO₂产生过程,来影响土壤CO₂和N₂O的地表排放通量,而对土壤10cm以下CO₂和N₂O的产生影响不大。小时尺度的土壤CO₂和N₂O浓度波动则可能还有其他影响因素或机制。3)降雨时土壤渗水引起的土壤空气对流取代气体浓度扩散成为土壤与大气空气交换的主要方式,导致土壤CO₂和N₂O排放通量的同步波动。降雨渗水较多时,较多的溶解氧随着雨水进入土壤内,会促进土壤CO₂的生成和抑制N₂O的产生。4)土壤CO₂与N₂O浓度存在显著的正相关关系,反映出土壤CO₂和N₂O有相对稳定的产率比。土壤有效碳可能是造成土壤CO₂与N₂O浓度正相关的主要原因,土壤空气的氧分压则可能是造成土壤CO₂和N₂O浓度波动不一致的重要因素。     

Identifying semi-volatile contaminants in fish from Niyang River, Tibetan Plateau

This study investigated the contamination levels and profiles of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), organochlorine pesticides (OCPs) including dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) in fish from the Niyang River, Tibetan Plateau. The total concentrations of ∑PCB, ∑PBDE and ∑OCP were in the range of 0.246–1.056 ng/g (mean 0.540 ± 0.289 ng/g), 0.280–2.220 ng/g (mean 0.914 ± 0.643 ng/g) and 7.24–13.80 ng/g (mean 10.70 ± 2.31 ng/g), respectively. The total mercury concentration (HgT) in fish ranged from 85 to 217 ng/g dw with an average of 129 ng/g dw, and the concentrations of methyl mercury (MeHg) ranged from 61 to 160 ng/g dw with an average of 102 ng/g dw. The proportion of MeHg contributed to 66–91 % (average 80 %) of HgT for all samples, indicating that organic mercury was the predominant form of mercury in fish muscle. The results revealed that the fish from the Niyang River were contaminated with various persistent toxic pollutants and the potential influencing factors on the bioaccumulation concentration in fish were analyzed using Pearson’s correlation analysis.     

徐州市区多环芳烃的环境地球化学特征

选择江苏徐州城市生态系统中水、土、植物等不同环境介质进行多环芳烃的定量分析,研究并探讨了多环芳烃在城市环境中的地球化学特征。研究结果显示:多环芳烃在徐州土壤、地表水、地下水以及生长作物中均广泛存在,主要集中在以钢铁厂为中心的城区约20 km2范围内。由此提示人们:由大量工业活动等人为因素造成的徐州城市环境有机污染不容忽视。     

土壤-水混合实验同位素变化研究

土壤是一个复杂的系统,研究土壤对输入水分中氢氧稳定同位素组成的影响对了解水分在土壤中的运移机理及流域径流分割等具有重要作用。通过两种不同土壤与同一种输入水之间和同一种土壤与两种不同输入水之间的两组混合实验,研究土壤水与输入水达到同位素平衡的时间和引起二者同位素变化的原因。实验结果表明,土壤水与输入水之间同位素变化主要由混合作用引起;土壤对输入水氢氧同位素的吸附现象较难观测到,易被氢氧同位素测样误差掩盖,有待进一步研究;土壤水和输入水在混合搅拌条件下最快能在0.5～1h达到同位素平衡。     

Significant seasonal variation in the hydrogen isotopic composition of leaf-wax lipids for two deciduous tree ecosystems (Fagus sylvativa and Acerpseudoplatanus)

Compound specific hydrogen isotope ratios (δD) of long chain sedimentary n-alkanes, which mostly originate from the leaf waxes of higher terrestrial plants, are increasingly employed as paleoclimate proxies. While soil water is the ultimate hydrogen source for these lipids and the isotopic fractionation during biosynthesis of lipids is thought to remain constant, environmental parameters and plant physiological processes can alter the apparent hydrogen isotopic fractionation between leaf-wax lipids and a plant’s source water. However, the magnitude and timing of these effects and their influence on the isotopic composition of lipids from higher terrestrial plants are still not well understood. Therefore we investigated the seasonal variability of leaf-wax n-alkane δD values for two different temperate deciduous forest ecosystems that are dominated by two different tree species, Beech (Fagus sylvatica) and Maple (Acerpseudoplatanus).We found significant seasonal variations for both tree species in n-alkane δD values of up to 40‰ on timescales as short as one week. Also, the isotopic difference between different n-alkanes from the same plant species did vary significantly and reached up to 50‰ at the same time when overall n-alkane concentrations were lowest.Since δD values of soil water at 5 and 10 cm depth, which we assume represent the δD value of the major water source for the investigated beech trees, were enriched in autumn compared to the spring by 30‰, whereas n-alkane δD values increased only by 10‰, we observed variations in the apparent fractionation between beech leaf derived n-alkanes and soil water of up to 20‰ on a seasonal scale. This observed change in the apparent fractionation was likely caused by differences in leaf water isotopic enrichment. Based on mechanistic leaf water models we conclude that changes in the isotopic difference between water vapor and soil water were the most likely reason for the observed changes in the apparent fractionation between n-alkanes and soil water.The large variability of n-alkane concentrations and δD values over time implies a continuous de novo synthesis of these compounds over the growing season with turnover times possibly as short as weeks. The signal to reach the soil therefore represents an integrated record of the last weeks before leaf senescence. This holds true also for the sedimentary record of small catchment lakes in humid, temperate climates, where wind transport of leaf-wax lipids is negligible compared to transfer through soil and the massive input of leaves directly into the lake in autumn.     

2012—2013年重庆雪玉洞洞穴系统碳循环特征

重庆雪玉洞洞内CO₂浓度之高,在国内外皆罕见,但此洞穴系统碳循环特征及控制因素仍不清楚.利用土壤二氧化碳分压(P_CO2-soil)、洞内大气二氧化碳分压(P_CO2-cave)、地下河水二氧化碳分压(P_CO2-eq)、方解石饱和指数(SIc)、地下河水溶解无机碳同位素(δ13C_DIC)等指标来研究雪玉洞洞内CO₂浓度变化、控制因素以及地下河对洞内碳循环的影响.结果表明:雪玉洞上覆P_CO2-soil雨季高,旱季低;降雨量是控制上覆P_CO2-soil的重要因子.雪玉洞P_CO2-cave变化规律明显,暖季高,冷季低;温度变化导致洞内外气流频繁交换是P_CO2-cave突变的重要原因,地下河水CO₂脱气能够在短时间内让P_CO2-cave上升到较高值.雨季由于土壤CO₂效应,地下河水具有低SIc、高P_CO2-eq特性,矿化度较高,并且部分月份地下河水具有溶蚀性;旱季由于土壤CO₂效应及降雨较少,地下河水呈现高SIc、低P_CO2-eq特性,矿化度较低,以沉积为主.      

Mercury concentrations in environmental media at a hazardous solid waste landfill site and mercury emissions from the site

Mercury (Hg) concentrations in air, effluent water, landfill gas, leachate, groundwater, and soil at a hazardous solid waste landfill site in Korea were measured along with air–soil surface Hg exchange fluxes at the site. The concentrations and fluxes were considerably higher than have been found elsewhere in Korea. Gaseous Hg concentrations in the air peaked during the day, coinciding with Hg being released from the landfill surface. This suggests that air–soil exchange increased the Hg concentrations in the atmosphere. The air–soil exchange flux increased abruptly when solar radiation reached the soil surface. The Hg flux peaked about 3 h before the solar radiation peaked, possibly because reducible Hg was abundant at the soil surface. The Hg emission flux activation energy (E _a) was low, indicating that the Hg species present and Hg–soil binding were probably not as important (because of the high Hg content of the soil) as in previous studies. The methylmercury to total Hg ratios in the discharged effluent, groundwater, and leachate was clearly higher than typically found in coastal water and freshwater, suggesting bacteria caused active methylation to occur under the reducing conditions in the anaerobic landfill. The results suggested that considerable amounts of Hg are probably transported from the landfill to nearby environmental media and that this will continue if waste with a high Hg content continues to be added to the landfill without being pretreated.     

Distributions of branched GDGTs in soils and lake sediments from western Uganda: Implications for a lacustrine paleothermometer

Bacterially produced branched glycerol dialkyl glycerol tetraethers (GDGTs) are ubiquitous in soils and lake sediments and can potentially be used to reconstruct past temperatures. In lakes, however, it is still unclear if these compounds are derived from eroded soils or if they are produced in situ. To better understand environmental controls on the distributions of these compounds and the sources of branched GDGTs to lake sediments, we compare branched GDGT distributions and concentrations in lake sediments and catchment soils within a 3600 m altitudinal transect in western Uganda. Reconstructed mean annual air temperature (MAAT), determined from the degree of methylation (MBT) and cyclisation (CBT) of branched GDGTs in soils, decreases with increasing altitude, as is expected from the air temperature gradient in our transect. However, we observe significant offsets between observed and reconstructed temperatures in soils from wet, high elevation soils but not in most dry, low elevation soils. Branched GDGT distributions differ significantly between lake sediments and soils at all elevations, with greater differences at low elevations than at high elevations. These data support previous hypotheses that branched GDGTs are produced in situ in lakes and suggest that the abundance of water in soil environments may play a role in controlling the distribution of branched GDGTs. While branched GDGTs in lacustrine sediments can be used to reconstruct temporal temperature variations in lakes, we urge caution in utilizing this proxy in lacustrine systems with high soil loadings, especially if there is evidence of changing clastic fluxes through time.     

Polybrominated diphenyl ethers in combusted residues and soils from an open burning site of electronic wastes

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental contaminants due to their extensive use. Combusted residue from electronic waste (e-waste) combustion is one of the contamination sources because PBDEs may be deposited in the soil and transported to remote locations. The transport and deposition behaviors of PBDEs released from burning were evaluated by analyzing their concentrations and congener distributions. Total PBDE concentrations were detected in the range from 2379 to 6238 ng/g (dry weight) in the combusted residue samples collected from a large open burning site and from 247.4 to 1422.3 ng/g in soil samples collected from different locations close to the open burning site. BDE-209, 183, 153, 99, and 47 were detected in relative high concentrations in both combusted residue and soil samples. The interpretation of the PBDEs concentrations and congener patterns in the combusted residue and soil samples indicated that PBDEs contamination in soil might be a result of e-waste burning and transportation, and deposit of the combusted residue. The total PBDE concentrations decreased significantly with increasing distance from the burned site, suggesting that the combusted activities were the major source of PBDEs in the region and the transportation behavior of lower brominated congeners might not differ from that of higher brominated congeners for short distances.     

Atmospheric pollutants transport tracks revealed from 131I, 137Cs,and 134Cs leaked from Fukushima accident and 7Be and 210Pb observed at Guiyang of China

A massive earthquake measuring 9.0 on the Richter scale that occurred on March 11, 2011, on Honshu Island, Japan, caused radioactivity leakage from the Fukushima Nuclear Power Plant, which led to the leakage of artificial nuclides （131I, 137Cs, and 134Cs） and their global transportation by atmospheric circulation. This paper re- ports a systematic comparative observation on radioactive concentrations of natural nuclides （7Be and 210Pb） and artificial nuclides （131I, 137Cs, and 134Cs） at the surface level, measured in weekly continuous aerosol sampling at Mount Guanfeng, Guiyang, China, from March 17, 2011 to April 28, 2011. During this period, the variations in the nuclide concentrations associated with their transport paths were analyzed with 315 hour back-trajectories of air mass initialized 500 m above the surface level at Guiyang. The results show that the pollutants of nuclear leakage from the Fukushima accident were transported to the Guiyang region of China via two significant pathways. In the first pathway the first wave of nuclear pollutants were transported from west to east in air masses at higher altitudes via global atmospheric circulation. The nuclear pollutants encircled the Earth almost once and after about 10 days to two weeks, between March 24 and March 31,2011, intruded Guiyang from the northwestern region of China. In the second pathway, the nuclear pollutants from the Fukushima region arrived at Guiyang between April 7 and April 14, 201 l, via air masses at lower altitudes that moved southwards because of the squeezing of the northeast Asian weather system and then by the influence, in succession, of the northeastern and southeastern air currents in the low-latitude region. The first transport pathway for atmospheric pollutants is on a global scale and based on air masses at higher altitudes, and the second transport pathway is on an eastern Asia regional scale and based on the air masses at lower altitude.     

Hydrologic and geochemical influences on the dissolved silica concentration in natural water in a steep headwater catchment

The dissolved silica concentrations in groundwater, springwater, and streamwater were measured on an unchanneled hillslope in the Tanakami Mountains of central Japan. The effects of preferential flowpaths, including lateral and vertical flow in the soil layer and flow through bedrock fractures, on the variation in the dissolved silica concentrations in runoff and groundwater were examined, as were the effects of the mixing of water from geochemically diverse water sources on the dissolved silica concentrations. The mean dissolved silica concentrations in water sampled from 40 cm below the soil surface and in transiently formed groundwater above the soil-bedrock interface during rainfall events were relatively constant, independent of the variation in the mixing ratio of pre-event water and incoming throughfall. These waters were mostly supplied by the vertical infiltration of water in soil. The mean dissolved silica concentrations were similar, regardless of sampling depth, although the mean residence time of the water increased with depth. These results indicated that the dissolved silica concentrations in soil water and transient groundwater were independent of contact time between the water and minerals. The mean dissolved silica concentration in perennially saturated groundwater above the soil-bedrock interface, which was recharged by water infiltrating through soil, and water emerging from bedrock in an area near the spring was more than twice that of transient groundwater, and the variation was relatively large. The mean dissolved silica concentration increased significantly downslope, from perennial groundwater to spring from soil matrix to stream, and the spring and stream concentrations also showed large variations. The dissolved silica concentration was highest in the spring from a bedrock fracture and was relatively constant. The mixing of water from two geochemically diverse water sources, soil and bedrock, controlled the dissolved silica concentrations of the perennial groundwater, the spring from soil matrix, and the stream. Our results demonstrated that in most areas of this headwater catchment, the preferential flowpaths have only a small effect on the dissolved silica concentrations. In a small area, which was < 2% of the total catchment area near the spring, the dissolved silica concentration was controlled by the mixing of water from geochemically diverse water sources.     

Atmospheric pressure dielectric barrier discharge for the remediation of soil contaminated by organic pollutants

The remediation of soil, contaminated by organic pollutants, in a cylinder-to-plane dielectric barrier discharge reactor at atmospheric air pressure was reported. Two model organic pollutants were selected; a solid pollutant (2,6-dichloropyridine) and a liquid pollutant (n-dodecane). The effects of the contaminant’s initial concentration and state, the energy consumption, and the soil type on the pollutant removal efficiency were investigated. To that scope, various contaminated samples of both quartz sand and loamy sandy soil were treated by plasma for various treatment times and initial 2,6-dichloropyridine/n-dodecane concentrations. The results revealed that (1) the removal efficiency of 2,6-dichloropyridine was higher compared to that of n-dodecane at a given plasma treatment time and (2) the removal efficiency increased with the energy density increasing, but decreased as the soil heterogeneity, organic matter and pollutant concentration were enhanced. The main removal mechanism proposed is the evaporation of pollutant molecules coupled with their oxidation by plasma species in the gas and solid/liquid phase.