Spatial and temporal distribution of gaseous elemental mercury in Chongqing, China

In order to investigate the spatial and temporal variability of atmospheric mercury (Hg) in Chongqing, China, gaseous elemental mercury (GEM) was measured from August 2006 to September 2007, using Lumex multifunctional mercury analyzer RA-915(+) (Lumex Ltd., Russia). The mean GEM concentration was 6.74 +/- 0.37 ng m(-3) in Chongqing, much higher than the accepted global background values (1.5-2 ng m(-3)). The GEM concentrations were different in different function areas. GEM in transport, industrial and commercial areas were 7.07 +/- 1.04, 7.05 +/- 0.96 and 6.71 +/- 1.10 ng m(-3), respectively, while GEM was 6.14 +/- 1.30 and 4.32 +/- 1.04 in the educational/recreational and nature conservation areas, suggesting that Hg emissions from mobile vehicles and industrial sources (specially coal combustion) were the most important contributors to atmospheric Hg in Chongqing. Mean Hg concentrations also had monthly variations with highest in November (8.24 +/- 0.50 ng m(-3)) and lowest values in August (5.36 +/- 0.70 ng m(-3)). Additionally, the diurnal variation of GEM concentrations was dependent on the local/regional atmospheric conditions. At Jinyun Mountain site (natural conservation area), hourly GEM concentrations had much higher values in daytime than at night. At Power Plant site, however, the hourly GEM concentrations were lower in daytime than at night. GEM concentrations in the air were correlated significantly with meteorological parameters except for barometric pressure.     

活性炭负载催化剂去除燃煤烟气中单质汞的研究

以贵州凯里褐煤进行燃烧实验,研究采用CoCl2(负载量20%)改性的活性炭去除烟气中的单质汞。颗粒态汞占烟气总汞的87%,而单质汞占气态汞的80.4%。改性活性炭吸附了气态汞中97%的单质汞,而吸收液只吸收了3%的单质汞。可见改性活性炭也能有效地吸附煤燃烧实验中的烟气汞。实验结果表明,煤中汞的释放率为59.5%,1kg的改性活性炭可以吸附208t煤所产生的烟气中的气态单质汞。     

Biomonitoring with epiphytic lichens as a complementary method for the study of mercury contamination near a cement plant

The study was focused on understanding the mercury contamination caused by a cement plant. Active and passive biomonitoring with epiphytic lichens was combined with other instrumental measurements of mercury emissions, mercury concentrations in raw materials, elemental mercury concentrations in air, quantities of dust deposits, temperatures, precipitation and other measurements from the cement plant's regular monitoring programme. Active biomonitoring with transplanted lichens Pseudevernia furfuracea (L.) Zopf was performed at seven of the most representative sites around the cement plant and one distant reference site for periods of 3, 6 and 12 months. In situ lichens of different species were collected at the beginning of the monitoring period at the same sites. Mercury speciation of the plant exhaust gas showed that the main form of emitted mercury is reactive gaseous mercury Hg2?, which is specific for cement plants. Elemental mercury in air was measured in different meteorological conditions using a portable mercury detector. Concentrations in air were relatively low (on average below 10 ng m?3). In situ lichens showed Hg concentrations comparable to lichens taken from the background area for transplantation, indicating that the local pollution is not severe. Transplanted lichens showed an increase of mercury, especially at one site near the cement plant. A correlation between precipitation and Hg uptake was not found probably due to a rather uniform rainfall in individual periods. Dust deposits did not influence Hg uptake significantly. Lichens vitality was affected over longer biomonitoring periods, probably due to some elements in dust particles, their alkalinity and the influence of other emissions. Mercury uptake measured in vital transplanted lichens was in a good correlation with the working hours (i.e. emitted Hg quantity) of the kiln. The study showed that selected lichens could be used to detect low to moderate Hg emissions from a cement plant and that the biomonitoring procedure could be further standardized and used as part of an environmental monitoring programme.     

A comparison of data quality control protocols for atmospheric mercury speciation measurements

Significant advances in the measurement of atmospheric mercury species have been made in the past 10 years yet limited protocols on quality control (QC) and assurance on this data have been published in the literature. Recently, considerable work has been done to develop quality control and assurance programs within North America. Environment Canada and the National Atmospheric Deposition Network (NADP) independently developed programs, RDMQ? and AMQC, respectively, to QC atmospheric mercury speciation data (including gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and mercury associated to particles (PHg)). These 2 programs were assessed by the criteria on which the data is QCed and comparability of the final data products. Results show that the criteria used to flag data compare well within the 4 tested sites and that the number of flags for each criterion is generally comparable. The QC programs were applied to 2 distinct data sets and the final QCed data was compared. From a mid-latitude site, the final data sets compare very well and showed there to be a 0.3, 8.6 and 15% difference in the mean GEM, RGM and PHg concentrations post QC of each program. It is recommended that either the RDMQ or the AMQC programs be employed for a typical mid-latitude site. When the QC programs were applied to highly variable data, the data do not compare as well for RGM and PHg. Results showed a 2.7, 27 and 33% difference in the mean GEM, RGM and PHg concentrations, respectively, post QC of each program. It is recommended that RDMQ be used for data that is highly variable with high RGM/PHg concentrations as it allows for more manual correction over the QCed data. This investigation of 2 QC programs produced comparable data and that either of these programs can be used as standard methods for the quality control of atmospheric mercury speciation data.     

大气中不同形态汞的采集和分析方法

作为一种环境优先污染物,汞对人体和其它生物毒性很大。大气是全球汞生物地球化学循环的重要场所。不同形态的汞由于理化性质不同,迁移转化过程及其对生态环境的影响也不同,准确测定大气环境中各种形态的汞对于了解其在大气中的行为具有重要意义。1990年以来,大气汞的采集和分析方法技术已经取得了长足进步,一些自动测汞仪、低汞空白和高时间分辨率的采样及分析技术相继出现,使得准确测定大气中不同形态的痕量汞成为可能。文章就国内外近10多年来在这些方面所取得的研究进展进行了回顾和总结,主要介绍了气态总汞、颗粒态汞、活性气态汞、甲基汞等的采集和分析方法。     

燃煤电厂煤中汞含量对烟气中汞排放水平的影响

对江苏省9家燃煤电厂入炉煤中ω（汞）及烟气中ρ（汞）进行了测试，结果表明，9家燃煤电厂入炉煤中ω（汞）为54．5～297 ng／g，平均值为139 ng／g，低于我国煤中ω（汞）的平均值（220 ng／g）。燃煤电厂排放烟气中ρ（汞）为0．08～16．97μg／m^3，远低于《火电厂大气污染物排放标准》（GB 13223－2011）汞及其化合物标准限值（30μg／m^3）。通过对燃煤电厂入炉煤中ω（汞）与最终排放的烟气中ρ（汞）进行分析，两者之间有一定的相关性。     

A comparison of speciated atmospheric mercury at an urban center and an upwind rural location

Gaseous elemental mercury (GEM), particulate mercury (PHg) and reactive gaseous mercury (RGM) were measured every other hour at a rural location in south central Wisconsin (Devil's Lake State Park, WI, USA) between April 2003 and March 2004, and at a predominantly downwind urban site in southeastern Wisconsin (Milwaukee, WI, USA) between June 2004 and May 2005. Annual averages of GEM, PHg, and RGM at the urban site were statistically higher than those measured at the rural site. Pollution roses of GEM and reactive mercury (RM; sum of PHg and RGM) at the rural and urban sites revealed the influences of point source emissions in surrounding counties that were consistent with the US EPA 1999 National Emission Inventory and the 2003-2005 US EPA Toxics Release Inventory. Source-receptor relationships at both sites were studied by quantifying the impacts of point sources on mercury concentrations. Time series of GEM, PHg, and RGM concentrations were sorted into two categories; time periods dominated by impacts from point sources, and time periods dominated by mercury from non-point sources. The analysis revealed average point source contributions to GEM, PHg, and RGM concentration measurements to be significant over the year long studies. At the rural site, contributions to annual average concentrations were: GEM (2%; 0.04 ng m(-3)); and, RM (48%; 5.7 pg m(-3)). At the urban site, contributions to annual average concentrations were: GEM (33%; 0.81 ng m(-3)); and, RM (64%; 13.8 pg m(-3)).     

Measurements of gaseous mercury exchanges at the sediment-water, water-atmosphere and sediment-atmosphere interfaces of a tidal environment (Arcachon Bay, France)

The elemental mercury evasion from non-impacted natural areas is of significant importance in the global Hg cycle due to their large spatial coverage. Intertidal areas represent a dynamic environment promoting the transformations of Hg species and their subsequent redistribution. A major challenge remains in providing reliable data on Hg species variability and fluxes under typical transient tidal conditions found in such environment. Field experiments were thus carried out to allow the assessment and comparison of the magnitude of the gaseous Hg fluxes at the three interfaces, sediment-water, sediment-atmosphere and water-atmosphere of a mesotidal temperate lagoon (Arcachon Bay, Aquitaine, France) over three distinct seasonal conditions. The fluxes between the sediment-water and the sediment-atmosphere interfaces were directly evaluated with field flux chambers, respectively static or dynamic. Water-atmosphere fluxes were evaluated from ambient concentrations using a gas exchange model. The fluxes at the sediment-water interface ranged from -5.0 to 5.1 ng m(-2) h(-1) and appeared mainly controlled by diffusion. The occurrence of macrophytic covers (i.e.Zostera noltii sp.) enhanced the fluxes under light radiations. The first direct measurements of sediment-atmosphere fluxes are reported here. The exchanges were more intense and variable than the two other interfaces, ranging between -78 and 40 ng m(-2) h(-1) and were mostly driven by the overlying atmospheric Hg concentrations and superficial sediment temperature. The exchanges between the water column and the atmosphere, computed as a function of wind speed and gaseous mercury saturation ranged from 0.4 to 14.5 ng m(-2) h(-1). The flux intensities recorded over the intertidal sediments periodically exposed to the atmosphere were roughly 2 to 3 times higher than the fluxes of the other interfaces. The evasion of elemental mercury from emerged intertidal sediments is probably a significant pathway for Hg evasion in such tidal environments exhibiting background contamination level.     

An analysis of total gaseous mercury (TGM) concentrations across the UK from a rural sampling network

Total gaseous mercury was collected at ten sites, which comprise part of the UK rural heavy metals monitoring network, between 2005 and 2008. Using the gold amalgam technique to capture total gaseous mercury, samples were analysed using a Tekran 2537A mercury vapour analyser. The data showed no upward or downward trend in atmospheric mercury concentrations over the period, with 4 year average concentrations between 1.3 and 1.9 ng m(-3), which are in line with other studies' observed northern hemispheric background concentrations of between 1.5 and 1.7 ng m(-3). Using data from nine of the sites, we were able to show seasonality within the data and through kriging we were able to interpolate the TGM concentrations over the UK, revealing a south-east to north-west declining concentration gradient. Using continuous speciated mercury measurements from one of the network sites, we show through wind sector analysis and air-mass back trajectories that this spatial trend is likely to be due to air masses moving over the UK from continental Europe on easterly winds. The levels of TGM recorded in the south-east of the UK also more closely match observed background TGM levels on the continent, which could indicate that the TGM concentrations from the north of the UK are a better reflection of the true North Atlantic atmospheric mercury background level.     

Fractions and leaching characteristics of mercury in coal

A huge amount of coal is always stored in open spaces in coal-fired power plants before combustion. Mercury released from coal by rain or flowing water is an environmental risk and can cause contamination of the soil around the storage area. To better understand mercury pollution and to control mercury emission before combustion, it is necessary to determine the mobility and leaching characteristics of mercury from coal. In this study, we collected ten coal samples from one coal-fired power plant and proposed a sequential extraction procedure to get five fractions of mercury for evaluation. Elemental Hg was found as the most dominant fraction, and sulfate Hg was shown to be the second largest fraction. The mercury in the organic and the soluble fractions were not the major fractions, but they should still be considered because of their high mobility.     

Ambient elemental, reactive gaseous, and particle-bound mercury concentrations in New Jersey, U.S.: measurements and associations with wind direction

Two and a half years of data of ambient concentrations of elemental mercury (Hg(0)), reactive gaseous mercury (RGM), and particle-bound mercury (Hg(p)) were collected at measurement sites at Elizabeth, New Jersey and New Brunswick, New Jersey with Tekran sampling units. The data were processed, summarized, and analyzed from a variety of perspectives. Data quality control and quality assurance procedures are described. Wind direction and wind speed data for each of the sites were also collected. Significant temporal variations in concentrations of all three species were observed. Some significant directional variations were also seen. The sporadic nature of many of the temporal variations is consistent with and could reflect highly variable emissions patterns from anthropogenic mercury sources. Overall mean concentrations of all species were determined. These were, for Hg(0), Hg(p), and RGM respectively; 2.25 +/- 0.04 nanograms per cubic meter (ng/m(3)), 8.21 +/- 0.39 picograms per cubic meter (pg/m(3)), and 8.93 +/- 0.31 pg/m(3) (arithmetic means and 95% confidence intervals) at Elizabeth, and 2.15 +/- 0.02 ng/m(3), 10.73 +/- 0.45 pg/m(3), and 6.04 +/- 0.30 pg/m(3) at New Brunswick. Mean concentrations were determined for 16 different sectors representing wind directions. The impact of one known large source is suggested by these data. Reasons for some directional variations are not apparent and suggest a need for further investigation.     

Measurements of fractionated gaseous mercury concentrations over northwestern and central Europe, 1995-99

Although it makes up only a few per cent. of total gaseous mercury (TGM) in the atmosphere, the fraction of oxidised (divalent) mercury plays a major role in the biogeochemical cycle of mercury due to its high affinity for water and surfaces. Quantitative knowledge of this fraction present in mixing ratios in the parts-per-10(15) (ppq) range is currently very scarce. This work is based on approximately 220 data for divalent gaseous mercury (DGM) collected during 1995-99 in ambient air. Over the course of the measurements, the sampling and analytical methods were modified and improved. This is described here in detail and includes transition from wet leaching and reduction procedures to thermo-reductive desorption, the use of annular as well as tubular denuders and adoption of an automated sampling system. The concentration of DGM exhibited a strong seasonal behaviour in contrast to atomic gaseous mercury, with low values in winter and maximum values in summer. The DGM/TGM ratios were frequently found to be below the detection limit (< or = 1%) and in the range 1-5%. A trend of diurnal DGM patterns was observed and implies photolytically induced sources. Scavenging of DGM during rain events was also noticed.     

Mercury emission and dispersion models from soils contaminated by cinnabar mining and metallurgy

The laboratory flux measurement system (LFMS) and dispersion models were used to investigate the kinetics of mercury emission flux (MEF) from contaminated soils. Representative soil samples with respect to total Hg concentration (26-9770 μg g(-1)) surrounding a decommissioned mercury-mining area (Las Cuevas Mine), and a former mercury smelter (Cerco Metalúrgico de Almadenejos), in the Almadén mercury mining district (South Central Spain), were collected. Altogether, 14 samples were analyzed to determine the variation in mercury emission flux (MEF) versus distance from the sources, regulating two major environmental parameters comprising soil temperature and solar radiation. In addition, the fraction of the water-soluble mercury in these samples was determined in order to assess how MEF from soil is related to the mercury in the aqueous soil phase. Measured MEFs ranged from less than 140 to over 10,000 ng m(-2) h(-1), with the highest emissions from contaminated soils adjacent to point sources. A significant decrease of MEF was then observed with increasing distance from these sites. Strong positive effects of both temperature and solar radiation on MEF was observed. Moreover, MEF was found to occur more easily in soils with higher proportions of soluble mercury compared to soils where cinnabar prevails. Based on the calculated Hg emission rates and with the support of geographical information system (GIS) tools and ISC AERMOD software, dispersion models for atmospheric mercury were implemented. In this way, the gaseous mercury plume generated by the soil-originated emissions at different seasons was modeled. Modeling efforts revealed that much higher emissions and larger mercury plumes are generated in dry and warm periods (summer), while the plume is smaller and associated with lower concentrations of atmospheric mercury during colder periods with higher wind activity (fall). Based on the calculated emissions and the model implementation, yearly emissions from the "Cerco Metalúrgico de Almadenejos" decommissioned metallurgical precinct were estimated at 16.4 kg Hg y(-1), with significant differences between seasons.     

Emission factor of mercury from coal-fired power stations

Mercury emission from coal-fired power stations, situated in Poland in the Silesian region was investigated. The determination methods for mercury in the consumed coal and in combustion gas, used in this research, are described. The mass of mercury emitted into the air from coal combustion in the power station is in constant relation to the mercury content in the consumed coal during the assumed period. A relationship between mercury emission into the air and the mercury content in the consumed coal in electric power stations is derived.     

Leaching Characteristics of Fly Ash from Thermal Power Plants of Soma and Tunçbilek, Turkey

Use of lignite in power generation has led to increasing environmental problems associated not only with gaseous emissions but also with the disposal of ash residues. In particular, use of low quality coal with high ash content results in huge quantities of fly ash to be disposed of. The main problem related to fly ash disposal is the heavy metal content of the residue. In this regard, experimental results of numerous studies indicate that toxic trace metals may leach when fly ash contacts water. In this study, fly ash samples obtained from thermal power plants, namely Soma and Tunçbilek, located at the west part of Turkey, were subjected to toxicity tests such as European Committee for standardization (CEN) and toxicity characteristic leaching (TCLP) procedures of the U.S. Environmental Protection Agency (U.S. EPA). The geochemical composition of the tested ash samples from the power plant show variations depending on the coal burned in the plants. Furthermore, the CEN and TCLP extraction results showed variations such that the ash samples were classified as `toxic waste' based on TCLP result whereas they were classified as `non-toxic' wastes based on CEN results, indicating test results are pH dependent.     

基于燃煤电厂超低排放的汞分布特性研究

为掌握超低排放改造后烟气处理装置对汞分布的影响,选择6台有代表性的超低排放火电机组进行现场测试。通过对火电机组入炉煤、炉渣、飞灰、脱硫石膏、末端烟气等样品的测试,得出不同燃烧产物中汞的分布:底渣和湿除出水的汞含量极微;电除尘底灰中的汞所占比重相对较大,平均汞含量占燃烧产物中总汞的比例可达57.97%。依据质量平衡原理,计算出不同超低排放改造工艺路线对汞的协同脱除效率为87.26%~95.60%,并分析了不同污染控制设备对汞排放的影响。     

贵州东部某燃煤电厂汞排放对周边环境空气及土壤的影响

结合当地气象条件,测定贵州省东部某燃煤电厂下风向环境空气汞浓度分布情况,同时测定该燃煤电厂周边表层土壤中汞含量,并对其污染程度进行评价,探讨了土壤汞与理化性质间的相关性。结果表明,该燃煤电厂下风向环境空气汞浓度远高于北半球大气气态总汞背景值,空气汞浓度在2.7 km范围内随距离的增大而增大,在2.7~5.0 km范围内汞浓度随距离的增大而减小。电厂周边表层土壤汞含量是贵州省A层土壤Hg背景值的8.5倍,存在中度到重度程度的污染,土壤Hg与土壤pH呈正相关性,但与土壤有机质未表现出相关性。     

南京某燃煤电厂汞的排放特点及分布特征

选择南京某燃煤电厂330 MW机组，对煤、炉渣、粉煤灰、烟尘、石灰石、石膏和烟气中的汞取样测量，探讨煤中汞在燃烧过程中的变化情况，并进一步分析汞的排放特点及分布特征。指出，煤经燃煤锅炉炉内高温燃烧后，炉渣中的汞对环境影响不明显；粉煤灰、烟尘中的汞存在富集现象，且随着粒径变细，富集程度加剧；燃煤锅炉燃烧后，随石膏排放的汞占比较大，应采取相应的防治措施。     

宁东能源化工基地固体废物中汞含量分布及对环境影响

通过分析宁东能源化工基地各大燃煤电厂以及煤化工厂固体废物样品,研究了固体废物中的汞分布规律及环境影响。结果表明:汞易在脱硫石膏、粉煤灰和气化粗渣中富集,汞浓度分别为0.16、0.24、0.15 mg/kg,而炉渣和气化细渣中的汞含量则相对较低,分别为0.05、0.03 mg/kg。通过化学组成及汞含量数据分析发现,出现这种情况的原因与汞本身易挥发的性质和固体废物的物化性质有关。此外,通过固体废物浸出毒性实验发现,脱硫石膏、粉煤灰、气化粗渣的浸出汞浓度小于浓度限值(0.1 mg/L),而气化细渣因锅炉回用,不参与填埋,汞又不易在炉渣中富集,故总体上宁东能源化工基地的固体废物无汞环境污染倾向。     

Effects of leachant temperature and pH on leachability of metals from fly ash. A case study: Can thermal power plant, province of Canakkale, Turkey

Lignite powered electric generation plants result in increasing environmental problems associated with gaseous emissions and the disposal of ash residues. Especially, low quality coals with high ash content cause enormous quantities of both gaseous and solid fly ash emissions. The main problem is related to the disposal of fly ash, which, in many cases, contains heavy metals. It is known that toxic trace metals may leach when fly ash is in contact with water. In this study, fly ash samples obtained from the thermal power plant in the town of Can in Turkey were investigated for leachability of metals under different acidic and temperature conditions. The experimental results show that a decrease in pH of the leachant favors the extraction of metal ions from fly ash. A significant increase in the extraction of arsenic, cadmium, chromium, zinc, lead, mercury, and selenium ions from the ash is attributed to the instability of the mineral phases. These heavy metals concentrations increase with respect to increasing acidic conditions and temperature. Peak concentrations, in general, were found at around 30°C.