ATMOSPHERIC DEPOSITION OF MERCURY SPECIES IN GWANGJU, A RURAL AREA IN SOUTH KOREA
Wet deposition is a significant contributor to the total Hg (THg) and methylmercury (MeHg) in terrestrial and aquatic ecosystems as a process for scavenging atmospheric Hg. While the wet deposition of Hg has been monitored at numerous sites worldwide, only a few studies have been conducted in Asian countriesdespite the fact that Asian countries contribute to ~70% of global anthropogenic Hg emissions with increasing temporal trends. Weekly precipitation samples were collected in a rural area of South Korea, Gwangju, and THg and MeHg concentrations were measured in these samples, from April to present. Ambient concentrations of gaseous oxidized mercury (GOM) and particulate-bound mercury (PBM) were calculated using the statistical model constructed by Chen et al. (2013), based on wet deposition data. The THg in precipitation ranged from 1.7 to 13 ng L-1 (volume weighted mean [VWM] of 4.5 ng L-1), and MeHg ranged from 18 to 98 pg L-1 (VWM of 38 pg L-1). The MeHg fraction in THg (%MeHg) was averaged to 0.85% (0.192.7%). The high degree of precipitation depth in summer contributed to significant wet deposition flux for MeHg (r2 = 0.65, p < 0.0001), while the correlation between precipitation depth and THg wet deposition flux was not significant (r2 = 0.23, p = 0.05). Furthermore, modeled GOM + PBM concentrations showed a significant negative correlation (r2 = 0.59, p = 0.0005) with MeHg wet deposition flux whereas no correlation was found between modeled GOM + PBM model and THg wet deposition flux (r2 = 0.04, p = 0.43). These results suggest that the concentration of MeHg in precipitation is relatively constant, and, therefore, its deposition flux is largely dependent on precipitation depth, while THg in precipitation shows a typical washout trend. Stable MeHg concentrations in rainwater could be maintained by rapid methylation and demethylation processes in the atmosphere.
WET DEPOSITION AND AIR CONCENTRATIONS OF MERCURY AT A RURAL SITE IN THAILAND
Mercury has been regarded to be one of the extremely hazardous metals due to its toxicity, volatility and low vapor pressure even at ambient temperature. As such, Mercurys existence is actually everywhere. It is noted that atmosphere is the foremost transport pathway of mercury emission and wet deposition is the most efficient at removing divalent mercury (a soluble form) from the air to the environment. However, there are still limited accessible data of air concentration and wet deposition of mercury in Thailand due to lack of measurements. Therefore, it is important to develop appropriate methods suitable for atmospheric and wet deposition mercury measurements in Thailand.
The poster presents the implementation of atmospheric and wet deposition of mercury measurements laboratory and the initial mercury results at a rural area in Thailand. With guidance and technical supports of Asia-Pacific Mercury Monitoring Network (APMMN), we conduct research and development on methodologies. The sampling and analysis of mercury in ambient air was utilizing Cold Vapor Atomic Fluorescence Spectrometry (CVAFS) based on the Compendium Method IO-5. The determination of mercury in precipitation was by Oxidation, Purge and Trap, and CVAFS based on the Method 1631, Revision E. It is well known that preventing samples from becoming contaminated during the sampling, transport and analysis process constitutes one of the greatest difficulties encountered in trace mercury determinations. The collaboration with APMMNs experts enabled us to improve facilities and analytical techniques that should minimize contamination and maximize the ability of the laboratory to make reliable trace mercury determinations. We conducted measurement of mercury in air and precipitation at the Environmental Research and Training Center which is located in a rural area of Pathumthani province, the suburb of Bangkok. The results showed that mercury in ambient air during June 2016 ranged 1.5-1.7 ng/m3. The mercury level in precipitation samples of one year sampling were varied from 1.0 - 24.5 ppt with the field blank below 0.5 ppt. Continuous monitoring program of mercury in air and precipitation in different areas in Thailand is necessary to understand the characteristic of mercury transport and deposition as well as determining source-oriented mercury changes in Thailand.
NETWORK MONITORING OF MERCURY WET DEPOSITION ACROSS ASIA
One of the most critical measurements needed to understand the mercury biogeochemical cycle is the rate of atmospheric mercury deposition. Atmospheric mercury is thought to be the largest input of mercury to most rivers and lakes globally. Consistent monitoring of mercury deposition provides a method to understand an essential component of the mercury problem at many locations. Tracking long-term deposition trends is particularly important as emissions reductions are realized under the Minamata Convention.
Several cooperators (Environmental Protection Administration-Taiwan, National Central University-Taiwan, National Atmospheric Deposition Program of the U.S., U.S. Environmental Protection Agency, and Environment Canada) have launched the Asia-Pacific Mercury Monitoring Network (APMMN) to systematically monitor mercury in wet deposition and in the air to estimate dry deposition. The APMMN seeks to promote sharing of information, data, and technologies to expand coordinated mercury monitoring capacity, cultivate a common understanding of policy-relevant mercury scientific topics, and develop mercury datasets useful for modeling. APMMN will provide technical assistance to Asia-Pacific countries that have mercury environmental concerns, but have limited mercury monitoring capabilities. Current membership includes ministries in Vietnam, Thailand, Indonesia, Sri Lanka, Philippines, Mongolia, Korea, and Japan. Key network design features include: a common, written standard operating procedure, a quality assurance plan and data flagging procedures, one regional laboratory, and regular operations meetings (http://apmmn.org.tw/). Cooperation in monitoring and data sharing among all participating groups would promote a better scientific understanding of the mercury issue, and would benefit all countries.
Basic observations, thus far, for APMMN will be presented, with comparisons to established networks, and future directions for the APMMN.
CONTINUOUS MONITORING ON ATMOSPHERIC GEM, GOM AND PBM CONCENTRATIONS AND WET HG DEPOSITION FLUXES AT FUKUOKA IN THE NORTHERN KYUSHU OF JAPAN
Atmospheric GEM, GOM and PBM2.5 were observed using the Tekran continuous monitor from December 2013 to November 2014 at Fukuoka City, located in the northern Kyushu islands, Japan. Their concentrations were lower than those at the urban cities in the East Asian region. GEM concentrations had no diurnal and seasonal variations. However, some pollution events were observed more frequently in winter and spring. The pollution events were sometimes occurred when the low pressure system or cold front and the travelling anticyclone passed over Fukuoka City. Back trajectory analysis showed that almost of these events were influenced by the substances transported from the Asian Continent. On the other hand, GOM concentrations were higher in the daytime than in nighttime, especially in spring, which has strong UV irradiation. Therefore, GOM might be mainly produced by photochemical reactions between GEM and air pollutants such as OH radical. PBM2.5 concentrations were higher in winter than in other seasons. Long-range transport from the Asian Continent mainly contributes to the pollution events of PBM2.5. In this study, the Hg in coarse particles (more than 2.5 μm) was also monitored by analyzing Hg in the impactor frit put into the air inlet of the Tekran monitor. About 30% of total PBM was in the coarse particles. Using these observation data, the annual dry deposition flux was calculated at around 10 μg/m2/yr. In addition, it is indicated that the dry deposition flux of PBMcoarse could not be negligible. The annual wet Hg deposition flux was 11.3 μg/m2/yr by calculating from the volume weighted mean concentration (7.7 ng/L) and annual precipitation depth. Thus, the total atmospheric deposition flux at Fukuoka was about 20 μg/m2/yr, which was almost equal with those in the other Japanese urban cities and industrial area.
GENERAL TRENDS OF TOTAL MERCURY (TM) WET DEPOSITION IN URBAN AND RURAL AREAS IN KOREA: LOCAL URBAN ACTIVITIES AND REGIONAL-SCALE TRANSPORT OF MERCURY
Total mercury (TM) was determined in weekly precipitation samples collected in Northern (Seoul, urban), Middle (Taean, rural), and Southern (Jeju Island, rural) Korea, from April 2015 to November 2016, to determine the seasonal variations in TM wet deposition and to assign sources and their contribution to mercury wet deposition. The monthly volume weighted mean (VWM) TM concentrations in Seoul, Taean, and Jeju Island were 22 ± 16, 13 ± 8.4, and 5.6 ± 4.7 ng L−1, respectively and the monthly TM wet deposition flux in Seoul, Taean, and Jeju Island were 1.5 ± 2.0, 0.85 ± 0.60, and 0.66 ± 0.47 μg m−2, respectively. The high VWM TM and TM wet deposition flux levels in Seoul were probably a result of local urban activity. Seasonal VWM TM concentrations in Seoul were highest in winter followed by summer, fall, and spring. The high VWM TM concentration in winter probably reflects the higher coal consumption in winter due to high demands for residential heating in China. The TM wet deposition concentrations in Seoul were influenced by both local urban activities and regional-scale transport. The large seasonal wet deposition fluxes observed in the summers were possibly due to intense monsoon rainfalls. The long-term measurement of TM wet deposition in Korea will go far toward achieving the goal of an Asia-Pacific Mercury Monitoring Network – APMMN.
CONCENTRATIONS AND POSSIBLE SOURCES OF ATMOSPHERIC SPECIATED MERCURY IN A REMOTE ISLAND OF KOREA
Atmospheric mercury mainly exists in three operationally defined inorganic forms: gaseous elemental mercury (GEM, Hg0), gaseous oxidized mercury (GOM, Hg2+), and particulate bound mercury (PBM, Hgp). Sum of GEM and GOM is often called as total gaseous mercury (TGM). GEM accounts for approximately 98% of total Hg in ambient air because its wet and dry deposition velocities are much lower than those of GOM and PBM. On the other hand, GOM is readily removed within a short distance from emission sources. PBM is either directly emitted from natural and anthropogenic sources or formed by gas-particle conversion from GOM. In this study, atmospheric speciated Hg concentrations were measured in a remote island of Korea, located between China and Korea peninsula in order to identify the relative importance of Chinese and domestic sources as well as possible secondary formation. Mercury samples were collected during six intensive sampling periods including August 18-21 in 2015, January 7-13, March 22-26, May 11-17, July 25-August 1, and November 1-8 in 2016. TGM, GOM, and PBM concentrations showed different diurnal and seasonal patterns. TGM and PBM concentrations were high in spring and winter while GOM concentration was enhanced in summer. Conditional Probability Function (CPF) analysis was performed to determine the predominant wind direction associated with high Hg concentration. Backward trajectories using HYSPLIT 4 were also calculated to depict a synoptic wind patterns during sampling periods, and potential source contribution function (PSCF) based on back-trajectories were applied to locate possible source areas. TGM and PBM concentrations generally increased with the winds blown from China in spring and winter. Short-term peaks of PBM concentration were also observed when the winds were directly passed through North Korea. However, high GOM concentration was associated with winds originating from ocean in summer, possibly indicating active oxidation reactions in marine boundary layer. More detailed results on major source/pathway identification will be shown at the conference.
PARTICIPATION OF TAIWAN TO THE ASIA-PACIFIC MERCURY MONITORING NETWORK (APMMN)
East, Southeast, and South Asia are the major anthropogenic mercury (Hg) emission source regions globally. While atmospheric and rainwater Hg monitoring activities have been steady in East Asia (China, Korea, Japan and Taiwan), such activities are limited in Southeast and South Asia due to the lack of monitoring capacity. Regional scientists and decision-makers must rely on limited information to understand and quantify the critical linkages between mercury emissions, environmental response, and potential human health concerns. As such, the Environmental Protection Administration Taiwan (EPAT), National Central University (NCU), U.S. Environmental Protection Agency (USEPA) and National Atmospheric Deposition Program (NADP) worked together since 2012 for the establishment of the Asia-Pacific Mercury Monitoring Network (APMMN) to assist regional countries for capacity building and to systematically monitor wet deposition and atmospheric concentrations of Hg in a network of stations throughout the Asia-Pacific region. EPAT and NCU are committed to this effort and network development. EPAT, with the assistance of NCU, has been supporting regional atmospheric Hg workshops and APMMN workshops in Taipei (2012), D.C. (2013), Hanoi (2014), Minamata (2015), and Bangkok (2016). EPAT funded NCU to establish the Center for Environment Monitoring and Technology and to employ a site liaison to support the coordination and operation of APMMN. The site liaison will travel to partner countries to provide assistance and services if necessary. The Atmospheric Trace Element Laboratory (ATEL) of NCU helps the analysis of total Hg in wet deposition samples from partner countries. To accommodate to future demand, EPAT helped ATEL to expand its analytical capacity by expanding the lab area and equipping the lab with 2 new class-1000 cleaning rooms, a new DI system, 2 Tekran 2600 Hg analyzers, and an autosampler in 2016. EPAT will provide wet deposition samplers (MIC-B type) to support rainwater sampling at sites in partner countries. Besides, ATEL will conduct a side-by-side intercomparison between the MIC-B and N-CON samplers on NCU campus in 2017 to assure comparable data quality between APMMN and NADP/MDN. To assist partner countries in developing their mercury monitoring and assessment capacity, training workshop will be arranged and held by NCU in 2017 to provide training on methods of sampling and analysis of mercury in air and rainwater and may expand to include other media (e.g, water, biota).
MERCURY MONITORING IN VIETNAM
Vietnam has signed the Minamata Convention on Mercury. The Vietnam goverment has approved the convention. A number of plans have been issued for the monitoring of Mercury, as well as the reduction of Mercury production. Vietnam Environment Protection Agency is currently a participant of the APMMN. One sampler has been installed in Hanoi for wet deposition and Mercury monitoring in the Atmospheric. Vietnam is going to establish a Mercury mornitoring network in the future.
ESTABLISHING STANDARDIZED PROTOCOL FOR ATMOSPHERIC MERCURY NETWORKS WORLDWIDE
To compare regional and global atmospheric mercury, standardized methodology, operating practices and data quality assurance needs to be established.
In October 2007, an atmospheric mercury best practices and standard operating procedure (SOP) workshop was held in Chicago, Illinois, USA. The workshop produced an atmospheric mercury speciation SOP distributed internationally for comments. All comments were merged into the document. In 2011, the National Atmospheric Deposition Program quality assurance manager and Atmospheric Mercury Network (AMNet) site liaison separated the document into several smaller, user friendly manuals and SOPs. In Brussels, April 2011, the AMNet site liaison presented the documents to the Global Mercury Observation System (GMOS) where the documents were adopted for use within the network. In November 2016, the Asia Pacific Mercury Monitoring Network (APMMN) organized a workshop on continuous atmospheric mercury monitoring. The APMMN workshop compared Asian Pacific SOPs to those used in AMNet/GMOS (See Suzuki APMMN poster). This poster will outline the development of the AMNet SOPs, manuals, and review the quality assurance and control used to evaluate atmospheric mercury data providing an opportunity to discuss the development and criteria with the NADP AMNet site liaison.
CANADIAN ATMOSPHERIC MERCURY MONITORING: ACHIEVING HIGH QUALITY DATA AND DATA COMPARABILITY
Atmospheric mercury has been monitored in Canada since the 1990s through both ongoing networks and independent research programs. Canada has been part of the Asia Pacific Mercury Monitoring Network (APMMN) since 2012. While many sites have come and gone over the years in Canada, Environment and Climate Change Canada currently monitors total gaseous mercury (TGM) at 11 sites and speciated atmospheric mercury at 5 sites. The mercury data is collected using the TekranTM 2537 and TekranTM 2537/1130/1135 system for TGM and gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particulate mercury (PHg), respectively. The measurements at each site across the country are collected using the standard procedures developed by the Canadian Atmospheric Mercury Measurement Network (CAMNet). Once collected, the mercury dataare processed through a quality control program that was developed at Environment Canada called the Research Data Management Quality system (RDMQ). All sitesapply the same system and procedures to the collected data. This system is designed to standardize QA/QC procedures by applying predetermined criteria to collected data to identify concentration and instrument fluctuations. The criteria were developed by the users of the Tekran instruments over time and include a variety of instrument, site and operator flags. There are 14 possible different flags applied to the TGM/GEM data and an additional 9 flags applied to the GEM/RGM/PHg data. The RDMQ system was compared with NADPs AMNet QC system and little difference was reported in the final data sets and thus it was concluded that either program could be applied to data emerging from the Tekran instruments.
Considerable atmospheric mercury monitoring data has been collected in Canada for over 20 years. The mercury levels at all but one of the current monitoring sites in Canada are decreasing. These decreases have been, for the most part, attributed to declines in emissions of mercury to the atmosphere. The trends reported in Canada are from high quality data as a result of the efforts that Canadian researchers have made to follow the standard protocols and procedures. Temporal and spatial trends of this monitoring data will be presented to provide an overview of the success of the Canadian mercury monitoring program. The treatment of the data collection and analysis will be discussed and recommendations on the application of this methodology to other potential networks, such as the APMMN, will be discussed.
EXPLORING POSSIBILITY OF COORDINATED ATMOSPHERIC MERCURY MONITORING IN ASIA-PACIFIC REGION
The National Atmospheric Deposition Program, the United States Environmental Protection Agency, and National Institute for Environmental Studies of Japan, co-organized the Asia-Pacific Expert Workshop on Continuous Atmospheric Mercury Monitoring at Minamata city, Japan, from November 28 to December 2, 2016. The objective of the workshop was to share monitoring practices and develop a common understanding of the operation and quality assurance procedures of automatic atmospheric mercury monitoring across the Asia-Pacific region. Researchers and environmental regulatory agencies operating Tekran(r) speciated/continuous monitoring system in NADP/AMNet in North America, and in Australia, Japan, Republic of Korea, Philippines, Taiwan, and Thailand discussed in detail the SOPs (Standard Operating Procedures) and QA/QC processes of their individual monitoring programs. As the result of the discussion, we found that SOPs and QA/QC processes are essentially common in at least 5 programs analyzed. We analyzed QA actions on operation practices in terms of procedures, intervals and other necessary standpoint among the 5 programs. We found that QA practices are essentially common and also action intervals are essentially similar for the purpose to achieve comparable monitoring outputs among the programs. This means that the major part of the actions used by all 5 programs/networks is very consistent each other. Although some procedures need to be discussed further to achieve better consistency, we found no substantial discrepancies among programs that may significantly affect data comparability among all the programs represented. This finding would be a starting point to explore possibility of coordinated atmospheric mercury monitoring in Asia-Pacific region.