G5 Remediation and control technologies

Tuesday, 26 July, 2011

TG5-O1 — 15:30-15:45
Authors: HIGUERAS, Pablo1, ESBRÍ, José M2, OYARZUN, Roberto3, LORENZO, Saturnino4, CARRASCO, F. Javier5, LLANOS, Wiilians R4, MARTÍNEZ-CORONADO, Alba6, LÓPEZ-BERDONCES, Miguel A6, GARCÍA-NOGUERO, Eva M6
(1)Universidad de Castilla-La Mancha, pablo.higueras@uclm.es; (2) Instituto de Geología Aplicada, Universidad de Castilla-La Mancha. 13400 Almadén (Ciudad Rea), Spain; (3) Departamento de Cristalografía y Mineralogía, Universidad Complutense de Madrid. 28071 Madrid, Spain; (4) Instituto de Geología Aplicada, UCLM. Pl. Manuel Meca, 1, 13400 Almadén (Ciudad Real); (5) Instituto de Geología Aplicada, Universidad de Castilla-La Mancha; (6) Instituto de Geología Aplicada, UCLM. Pl. Manuel Meca, 1, 13400 Almadén (Ciudad Real), Spain;

The Almadén mercury mining district has delivered one third of total mercury human production. This has caused an important dissemination of mercury in the local environment. Of particular importance are the atmospheric mercury emissions, historically coming from metallurgy, open mines, mine dumps and contaminated soils from mining and metallurgical precincts. At 2003 all the mining and metallurgical activity ceased, and some remedial works have been carried out in the area, causing an important reduction of such emissions. We have monitored and present here these reductions, measuring mercury concentrations both in the regional and local scenarios before, during and after these remedial works.

Measurements have been carried out by means of a LUMEX RA-915+ Zeeman effect Atomic Absorption Spectrometer, during a number of surveys carried out from 2002, with the mines and metallurgical plant in activity, to present day. They correspond to car-driven surveys, with GPS georeferenciation and with continuous measurements every second.

Our first survey was carried out in March 2002, with one of the four metallurgical furnaces in operation, and geometric average concentrations (GAC) were 39 and 82 ng m-3 for regional and local scale surveys respectively. In June 2002, with summer temperatures and with the metallurgy inactive these concentrations were 49 and 61 ng m-3, again respectively for the regional and local surveys: there is an increment in the regional concentrations, due to the difference in temperatures, and an important local decrease due to the metallurgical activity cessation.

Another important milestone was the reclamation of the main Almadén mine dump, producing GAC of 57.3 ng m-3 during the process, which reduced to 22.6 ng m-3 after it. In February 2011 these concentrations were of 11 ng m-3.

In 2004 El Entredicho open pit was completely filled with water, what caused a descent of GAC from 74 ng m-3 in June 2002 to 36 in February 2011.

Some sites still deserve some reclamation measures, such as Almadenejos metallurgical precinct, which is nowadays the main source of mercury to the atmosphere, with GAC of 13, 23 and 24 ng m-3 in June 2002, November 2008 and February 2011, measured in an area including the village of Almadenejos (468 inhabitants), affected by concentrations close the WHO limit for chronic exposure of 200 ng m-3.

TG5-O2 — 15:45-16:00
Authors: WANG, Jianxu1, FENG, Xinbin2, ANDERSON, Christopher W. N. 3, WANG, Heng1, YIN, Runsheng1, BAO, Zhengduo1
(1) (1)Institute of Geochemistry, Chinese Academy of Sciences; (2)Graduate University of the Chinese Academy of Sciences, wjx19861217@126.com; (2) Institute of Geochemistry, Chinese Academy of Sciences; (3) Massey University, New Zealand;

The ammonium thiosulphate assisted phytoextraction has been proved to be an effective tool to extract mercury from soil. Rarely studies, however, have examined the practicality of this method in a field environment. In addition, no study has tested the transport of mercury to the underground due to the application of the chelate. In this work, the thiosulphate assisted phytoextraction by four local Brassica juncea Czern. et Coss plant species(Brassica juncea Czern. et Coss.var. ASKYC, Brassica juncea Czern. et Coss.var.DPDH, Brassica juncea Czern. et Coss.var.CHBD, Brassica juncea Czern. et Coss.var.LDZY) from mercury polluted soil were evaluated in the field trial at Wanshan mercury mining district, SW China.The transport of mercury in the soil section plane was subsequently investigated as a function of thiosulphate amendment. Mean mercury concentration of the soil was 280 mgkg-1 for the 0-30 cm horizon. The results indicated that the mercury concentration in the roots and shoots of the plant were significantly increased through the application of thiosulphate to the soil. In the non-thiosulphate treated plants, the root and shoot mercury concentration of the four plant species were below 1 mgkg-1 which were significantly lower than the thiosulphate treated plants.In the thiosulphate treated plants, the shoot of the four plant species extracted mercury with mercury concentration reaching up to 101mgkg-1 for Brassica juncea Czern. et Coss.var.DPDH. The mercury concentration in the shoots of the four plants followed the trend: Brassica juncea Czern. et Coss.var.DPDH, Brassica juncea Czern. et Coss.var.CHBD, Brassica juncea Czern. et Coss.var. ASKYC and Brassica juncea Czern. et Coss.var.LDZY, while no significant differences were observed among the roots. Considering the plant biomass, the mercury phytoextraction yield of Brassica juncea Czern. et Coss.var. ASKYC, Brassica juncea Czern. et Coss.var.DPDH, Brassica juncea Czern. et Coss.var.CHBD, Brassica juncea Czern. et Coss.var.LDZY were 140g ha-1, 80g ha-1, 28g ha-1, 540g ha-1 respectively. The analysis of the bioavailable mercury concentration in the soil setion plane showed that the application of ammonium thiosulphate would not cause mercury to leach from soil. Results presented here indicated that Brassica juncea Czern. et Coss.var.DPDH had great potential in phytoextraction of mercury polluted soil assisted by ammonium thiosulphate.

TG5-O3 — 16:00-16:15
Authors: BEUTEL, Marc1, MOORE, Barry1, SHALLENBERGER, Ed2
(1) Washington State University, mbeutel@wsu.edu; (2) Confederated Tribes of the Colville Indian Reservation.

The accumulation of mercury in freshwater aquatic food webs is a widespread and growing health concern as nearly one-third of lakes in the US have fish consumption advisories in place due to elevated concentrations of mercury in fish tissue. Ionic mercury deposition, primarily sourced from coal fired power plants, enter aquatic ecosystems within freshwater lakes, and given the right anaerobic conditions is converted to the more toxic and bioavailable methylmercury (MeHg). MeHg can partition to organic seston such as algae, and subsequently biomagnify up the aquatic food web, where seemingly harmless levels in the water can concentrate into potentially toxic levels in fish tissue. North and South Twin Lakes, WA, are moderately deep (Zmean ~10 m; Zmax ~ 15 m), meso-eutrophic, dimictic lakes that exhibit seasonal hypolimnetic anoxia during summer thermal stratification . Beginning in 2009, a hypolimnetic oxygenation system was operated in North Twin to help improve the lakes coldwater fishery. The objective of this study was to evaluate spatial and temporal patterns of the total and methyl mercury in the water column and zooplankton before and after the implementation of hypolimnetic oxygenation in North Twin Lake in 2009, using South Twin as a untreated nearby reference lake. In 2008 prior to oxygenation, peak levels of methylmercury in anaerobic bottom waters of North and South Twin Lakes were 0.4-0.6 ng/L. In 2009 levels were < 0.05 ng/L in oxygenated North Twin Lake, but were again elevated in anaerobic bottom waters of South Twin Lake. Metals analysis shows a decrease in iron and manganese above the sediment water interface but an increase in the upper hypolimnion in response to oxygenation. This may be due to a still anoxic sediment water interface, as seen in the dissolved oxygen profiles, and the upward advective movement of the bubble plume. Regarding zooplankton, total mercury was significantly higher towards the end of the season in zooplankton from oxygenated North Twin Lake relative to non-oxygenated South Twin Lake in both 2009 and 2010. Methylmercury data for zooplankton and other pending results will be presented. This study sheds light on the complex, and at times counterintuitive nature of mercury’s biogeochemistry and bioaccumulation in freshwater lakes.

TG5-O4 — 16:15-16:30
Authors: HENRY, Betsy1, GLAZA, Edward2, BABCOCK, David2, MATTHEWS, Dave3, EFFLER, Steve3, DRISCOLL, Charles4, TODOROVA, Svetla4
(1)Exponent, henryb@exponent.com; (2) Parsons; (3) Upstate Freshwater Institute; (4) Syracuse University;

Onondaga Lake in Syracuse, NY has been impacted by a long history of municipal and industrial activity, including two former mercury cell chlor-alkali plants. In addition to nearshore sediment dredging and capping to address sediment toxicity concerns, the Consent Decree for the Onondaga Lake Superfund Site includes performance of a pilot study to evaluate the potential effectiveness of nitrate at reducing the formation of methylmercury in bottom waters of the lake where oxygen becomes depleted during summer stratification (i.e., the hypolimnion), while preserving normal stratification within the lake. Nitrate concentrations in Onondaga Lake have approximately doubled since implementation of a nitrification system (to reduce ammonia discharges) at the Metropolitan Syracuse Wastewater Treatment Plant in 2004.

From 2006 through 2010, redox species (including oxygen, nitrate, and sulfide), total mercury, and methylmercury were monitored in the water column of Onondaga Lake to evaluate the roles of oxygen and nitrate in controlling methylmercury concentrations in lake water. In addition, mercury concentrations in bulk zooplankton, Daphnia, and fish were monitored. Data show that both oxygen and nitrate control methylmercury accumulation in the hypolimnion during summer stratification. There is now an approximate two week delay relative to 2006 in the depletion of oxygen and nitrate at the deepest depths in the lake, and sulfide is only rarely detected. Maximum mass of methylmercury in the hypolimnion in 2007-2010 (19 – 60 g) is approximately 3-10 times lower than that observed in 2006 (199 g) and 5-17 times lower than in 1992 (318 g). Current water quality conditions in the lake, including epilimnetic nitrate concentrations of approximately 2 mgN/L, have resulted in a significant decrease in methylmercury concentrations in the hypolimnion and epilimnion, even during non-stratified periods. Tissue concentrations are also responding to the decreased methylmercury release from profundal sediment. Stable carbon and nitrogen isotope analysis of tissue indicates that the carbon source to upper level fish (i.e., smallmouth bass, walleye) is predominantly plankton, therefore decreases in water column concentrations should eventually be reflected in fish tissue. To further assess the utility of nitrate addition, a 3-year pilot test with extensive monitoring begins in 2011. The pilot test will include addition of liquid nitrate diluted with lake water at a water depth approximately 1 to 2 m above the lake bottom in order to maintain a nitrate concentration of 1 mgN/L and minimize the release of methylmercury to overlying water.

TG5-O5 — 16:30-16:45
Authors: MALCOLM, Elizabeth G.1, SCHAUS, Maynard H.1, REESE, Margaret L.1
(1) Virginia Wesleyan College, emalcolm@vwc.edu

Green roofs are a popular stormwater management strategy because they are effective in reducing runoff volume from buildings. Other benefits may include mitigation of heat island effects, added building insulation, increased roof lifespan and added aesthetic appeal. However, a reduction in stormwater volume does not necessarily result in a reduced pollutant load. There has been little research on the impact of green roofs on runoff quality and no published research on mercury in runoff from green roofs. As part of a multi-year study we have been evaluating the mercury and nutrient (nitrogen and phosphorus) content of green roof runoff as compared to that from traditional gravel-covered roofs. Our study sites in Southeastern Virginia are located within the Chesapeake Bay Watershed, which has mercury fish advisories and seasonal anoxia due to high anthropogenic nutrient loads. Samples were collected from experimental gravel and green roof plots and two sets of real gravel and green roofs. Alum and PhosFilter (UltraTechInternational Inc.) were also tested for their potential to reduce the phosphorus in the runoff when added as green roof amendments. Our results indicate that green roofs can leach significantly higher concentrations of nutrients than gravel roofs. Our chosen chemical amendments were not effective in lowering the nitrogen and phosphorus from the green roof runoff. Although mercury concentrations in runoff were sometimes higher from green roofs than gravel roofs, there was not a large difference in the total load of mercury coming off the roofs. Based on our nitrogen and phosphorus results, we recommend that fertilizer not be added during installation or maintenance of green roofs. When choosing green building technology, materials and methods must be carefully chosen to match the most critical needs of the local environment.

TG5-O6 — 16:45-17:00
Authors: MATHEWS, Teresa1, SOUTHWORTH, George 1, KETELLE, Richard 2, PETERSON, Mark1
(1) Oak Ridge National Laboratory, mathewstj@ornl.gov; (2) Bechtel Jacobs Co.;

Several streams on the U.S Department of Energy Reservation in Oak Ridge, Tennessee receive continuous inputs of dissolved inorganic mercury from contaminated storm drain systems within industrial facilities near their headwaters. Remedial actions taken over the past two decades have reduced waterborne inorganic mercury in two of these streams. In upper East Fork Poplar Creek, the reduction in average baseflow waterborne total mercury concentration from over 1000 ng/L in the 1990’s to approximately 400 ng/l in 2005 produced no discernable decrease in mercury concentrations in fish immediately downstream from the facility. In 2005, an activated carbon-based treatment system further reduced waterborne mercury by another 100 ng/L by removing mercury from an artesian spring that added 2 - 4 g/d of dissolved mercury to the stream. Removal of this source resulted in no change in mercury in fish, which remained above 0.8 mg/kg over the next four years. In White Oak Creek, a smaller stream similar in water chemistry to East Fork Poplar Creek, the response to source reduction measures was more encouraging. Re-routing a mercury-contaminated sump to a waste treatment system decreased average waterborne mercury from 50 - 110 ng/L to ~25 ng/L at sites downstream. Addition of a sorbent-based pre-treatment system a year later produced further improvement, with mercury averaging 15 - 20 ng/L downstream. Average mercury concentrations in sunfish in the year following each action decreased, from a maximum of 0.47 mg/kg prior to treatment to less than 0.25 mg/kg after completion of both. Data from these long-term monitoring programs indicate that the relationship between total waterborne mercury concentrations and mercury bioaccumulation in fish is very non-linear in these well buffered warm water streams. Remedial efforts will likely need to reduce waterborne mercury concentrations below 100 ng/L before changes in bioaccumulation are evident, and below 30 ng/L to meet the 0.3 mg/kg tissue-based water quality criterion.

TG5-O7 — 17:00-17:15
Author: FAULCONER, Emily1
(1) University of Florida, embem171@yahoo.com

Activated carbon is known to adsorb Hg(II)aq and Hg(0)(g). No known research has been performed to investigate the role of carbon-oxygen surface complexes in Hg(0)(aq) adsorption by activated carbon. Based on vapor phase research, it is possible that the removal mechanisms involve redox chemistry as well as physical adsorption and chemisorption, with the nature and quantity of the surface oxygen groups influencing adsorption capacity. Lactone and carbonyl have been suggested as potential adsorption sites or, being reducible functional groups, sites for Hg0 oxidation and subsequent adsorption. It is possible to tailor these surface groups through thermal or chemical oxidation, thus allowing for targeted contaminant removal. Hg-removal performance was verified by mercury mass balance, calculated by quantifying residual aqueous mercury, adsorbed mercury extracted by HF digestion, and volatilized mercury. The batch reactor contained a sealed Teflon mercury-carbon contact chamber with mixing and constant headspace N2 flow to a KMnO4 trap. Mercury adsorption was performed using spiked Nanopure water (~50 µg/L Hg). Mercury concentrations were obtained using EPA method 245.1 and CVAA spectroscopy. The surface chemistry of a commercially available bituminous-based powdered activated carbon was chemically modified using various concentrations of HNO3, NaOH, and H2O2. Humic substances formed during oxidation were removed using a NaOH and subsequent HCl rinse to prevent pore blockage and subsequent reduction in adsorption capacity. Samples were characterized using N2 adsorption-desorption, Boehm titration, pHpzc, X-ray photoelectron spectroscopy, and elemental analysis. It is hypothesized that activated carbon modification with NaOH will provide the ideal surface chemistry for Hg0(aq) adsorption due to the large proportion of lactone surface groups formed and the minimal pore degradation during the modification process. Metal catalysts impregnated on the carbon surface have the potential to enhance aqueous Hg0 removal through oxidation; future studies will investigate the potential redox reactions between magnetite in magnetic powdered activated carbon and aqueous Hg0.

TG5-O8 — 17:15-17:30
Authors: TAKAOKA, Masaki1, FUKUDA, Naomichi1, OSHITA, Kazuyuki1, MIZUNO, Tadao1, SHIOTA, Kenji1
(1)Kyoto University, takaoka.masaki.4w@kyoto-u.ac.jp

International programs are being designed to control mercury emissions and manage mercury products and waste globally. In response to this, the EU and USA plan to prohibit the export of elemental mercury. In many countries including Japan, management of recovered mercury from industries etc. will be required in the near future. Some technologies such as Sulfur Polymer Stabilization/Solidification (SPSS) method have been developed, but many of them require a heating process. Because elemental mercury has high volatility, the release of mercury is of concern in their technologies. Therefore, in this study, a mercury stabilization technology without heating process was investigated. Elemental mercury and sulfur were mixed using planetary ball milling with various experimental conditions. According to experimental results, it was confirmed that mercury sulfide was synthesized without heating process by X-ray diffraction and X-ray absorption fine structure methods. The release of mercury to atmosphere during the milling was not observed. The labile intermediate of mercury sulfide was observed in the early stage of milling, which has relatively high water leachability. At later stage, the intermediates were pulverized into mercury sulfide powder. These phenomena were significantly influenced with the diameter of ball (19.04mm, 9.52mm and 4.76 mm) in the vessel of 250mL. The larger diameter gave better mercury stabilization. In the case of ball diameter with 19.04mm, Japanese leaching test (JLT-46) value for the synthesized mercury sulfide became less than 0.5µg/L after almost 20 min. When the molar ratio of sulfur to mercury was 1.05, both TCLP(Toxicity Characteristic Leaching Procedure) and the JLT-46 values were 0.26 µg/L and 0.059µg/L respectively, which suggests that mercury leachability is strictly controlled. Also, the volatility of the synthesized mercury sulfide was evaluated employing head space analysis. The mercury concentration in the head space was less than 1µg/Nm3 at 20°C, which was equivalent to the level of pure reagent. Compared with other mercury stabilization technologies, the stability of mercury sulfide synthesized by planetary ball mill at optimal conditions was as well or better. The running cost of this technology was estimated to be 13,250 Yen (160 USD)/ ton- Hg and lower than that of SPSS method. Therefore, this stabilization technology is cost-effective and environmentally-sound for long term safe management of mercury.

Tuesday, 26 July, 2011