Health & Chemicals

FY2016 Results on Background Monitoring Survey for Atmospheric Mercury and Other Metal Element Concentrations

The Ministry of the Environment (MOE) of Japan has been conducting a background monitoring survey for atmospheric mercury as well as other metal element concentrations at Cape Hedo in Okinawa Prefecture, and atmospheric mercury concentration at Oga Peninsula in Akita Prefecture, where direct effect from local emission sources is minimal. The results of the survey may contribute to the global mercury management such as the global monitoring plan of the Minamata Convention on Mercury.

The results of the Fiscal Year (FY)2016 (April 1, 2016 through March 31, 2017) survey showed that mercury concentrations in the atmosphere and precipitation at Cape Hedo and Oga Peninsula were well below the national guideline values, and these values did not deviate significantly from those of the previous survey results.

The values of other metal elements in aerosols at Cape Hedo also did not significantly deviate from the previous monitoring results.

1. Background Informatio.

The United Nations Environment Programme (UNEP) has been promoting its activities on mercury pollution at the global level since 2001, and in October 2013, the Minamata Convention on Mercury was adopted at the Conference of Plenipotentiaries (Diplomatic Conference) on the Minamata Convention on Mercury, held in Minamata and Kumamoto. The number of the ratifications deposited reached 50 on 18 May 2017 and the Convention entered into force on 16 August 2017.

The government of Japan accepted the Minamata Convention in February 2016, and the "Act on Preventing Environmental Pollution on Mercury" was promulgated in June 2015 and was enforced on 16 August 2017.

The Ministry of the Environment has been conducting a background monitoring survey for atmospheric mercury concentrations at Cape Hedo in Okinawa Prefecture (hereinafter referred to as Cape Hedo) since FY2007 where the direct effect from local emission sources is minimal. Then, since FY2010, the monitoring results have been officially published each year after the reliability and the quality of the monitoring data were ensured.

In August 2014, another monitoring survey at Oga Peninsula (hereinafter referred to as Oga) in Akita prefecture commenced.

The followings are the results of the monitoring surveys at both sites from FY2016.

2.Overview of the Surve

(1) Monitoring of Atmospheric Mercury Speciation, Mercury Concentration in Precipitation and Other Metal Element Concentrations in Aerosols.

Mercury in the atmosphere exists in various forms such as Gaseous Elemental Mercury (GEM), Gaseous Oxidized Mercury (GOM) and Particle-Bound Mercury (PBM). It is known that the different forms of mercury behave differently in the atmosphere.

This survey aims to provide a basis on global mercury emissions, the trend of its concentrations, and the effect of mercury to the environment in Japan. The concentrations of atmospheric mercury, namely GEM, GOM and PBM, and of mercury deposited with precipitation were analyzed at Cape Hedo as the national background monitoring site (See Table 1).

A monitoring survey has also been conducted at Oga since August 2014 in order to monitor the background concentration level in northern Japan.

(2) Monitoring Sites (See Appendix 1)

・Cape Hedo, Okinawa Prefecture.

Cape Hedo Atmosphere and Aerosol Monitoring Station, the National Institute for Environmental Studies, located in Ginama, Kunigami-son, Kunigami-gun, Okinaw.

・Oga Peninsula, Akita Prefecture.

Adjacent to the Funakawa Ambient Air Pollution Monitoring Station, located in Izumidai, Funagawaminato-funagawa, Oga-shi, Akit.

(3) Monitoring Methods, Survey Items and Monitoring Frequency

The atmospheric monitoring was conducted by using a continuous mercury speciation analyzer. The precipitation was collected by the wet-only sampler, and the mercury concentration was analyzed based on the method specified by the United States Environmental Protection Agency (EPA).

Survey items and monitoring frequency are shown in Table 1.

Table 1 Survey items and monitoring frequenc.
CategorySurvey itemMonitoring frequencyMonitoring Site (number of no-operation periods)
Atmospheric mercury component Gaseous Elemental Mercury(GEM) Continuous (16 times/day) Cape Hedo (5 days)
Oga (0 day.
Gaseous Oxidized Mercury
(GOM)
Continuous (8 times/day) Cape Hedo (9 days)Oga (0 day)
Particle-Bound Mercury
(PBM)
Cape Hedo (9 days)
Oga (0 day)
Other Metal elements in aerosols Weekly (7-day continuous sampling) Cape Hedo (1 week)
Precipitation components Mercury concentration in precipitation Weekly (7-day continuous sampling) Cape Hedo (0 week)
Oga (0 week)

Note 1: "Gaseous Elemental Mercury" in this survey refers to gaseous, elemental mercury in the air (Hg0). "Gaseous Oxidized Mercury" refers to atmospheric gaseous oxidized mercury (Hg2+), and "Particle-Bound Mercury" is mercury suspended or bound to floating particles in the atmosphere.

Note 2: The monitoring method of this survey is different from that of the harmful air pollutant monitoring survey conducted under the Air Pollution Control Act.

3. Summary of Survey Result

(1) Atmospheric Mercury Concentratio.

Annual mean concentrations of the sum of all mercury forms in the atmosphere were 1.7 ngHg/m3 (hourly values in the range of 1.2 - 3.5 ngHg/m3) at Cape Hedo, and 1.6 ngHg/m3 (hourly values in the range of 0.7 - 20.3 ngHg/m3) at Oga, both of which were well below the guideline value for reduction of health risk by harmful air pollutants (i.e. annual mean value 40 ngHg/ m3).

Mercury in the atmosphere is mostly composed of GEM, and the average percentage of GOM and PBM were less than 1% at both sites.

While annual mercury concentrations of both total and each mercury form at Cape Hedo have remained largely unchanged, the concentrations in FY2016 were slightly lower than the ones in the previous fiscal years, following FY2015 (See Table 2).

It should be noted that the monitoring data during trial survey period up to FY2009 should be referred to with care (i.e. the monitoring was conducted only in limited period).

Table 2 Atmospheric mercury concentrations at Cape Hedo by fiscal year (annual mean)

(Unit: ngHg/m3)
Measured itemFY2007FY2008FY2009FY2010FY2011FY2012FY2013FY2014FY2015FY2016
Gaseous Elemental Mercury 1.5 1.8 2.2 1.9 2.1 2.0 1.7 1.7 1.6 1.7
Gaseous Oxidized Mercury - - 0.001 0.002 0.002 0.001 0.002 0.002 0.001 0.002
Particle-Bound Mercury - - 0.002 0.002 0.002 0.002 0.004 0.004 0.002 0.003
Total - - 2.2 1.9 2.1 2.0 1.7 1.7 1.7 1.7

Note: The FY2007 mean value is calculated from the data starting on 16 October when the monitoring program began. The annual mean is obtained using the total concentration of oxidized mercury, and particle-bound mercury is calculated from the data in October 2009 and onward when stable monitoring was established.

Annual mercury concentrations of both the total and each mercury form at Oga have remained at virtually similar level as the values from FY2015 (see Table 3).

Table 3 Atmospheric mercury concentration in Oga (annual mean)

(Unit: ngHg/m3)
Measured itemFY2014FY2015FY2016
Gaseous Elemental Mercury
(GEM)
1.6 1.6 1.6
Gaseous Oxidized Mercury
(GOM)
0.002 0.003 0.002
Particle-Bound Mercury
(PBM)
0.009 0.009 0.011
Total 1.6 1.6 1.6

Note: FY2014 values were calculated from data starting on 8 August, 2014, when the monitoring program began.

(2) Mercury Concentration in Precipitation

Based on discussion at "the expert committee for hazardous metal monitoring survey" and the results of comparative test for this one year, an improved analytical procedure for measuring mercury concentration in precipitation was adopted. In detail, the analytical procedure was improved so that bromine monochloride was added to sampling vessels before the precipitation sample was sampled, to avoid adsorption of mercury to the wall of sampling vessels, whereas before, the bromine monochloride was added after the precipitation sampling.

From the results of one year comparative test carried out from February 2016 to February 2017, it was revealed that the measured values obtained from improved analytical procedure were approximately 1.3 to 1.4 times larger than those obtained from conventional analytical procedure.

Annual mean mercury concentration in precipitation at Cape Hedo was 6.6 ng/L (weekly values in the range of 2.7 - 19.4 ng/L) by using improved analytical procedure. By using conventional analytical procedure, it was 4.3 ng/L and did not significantly deviate from the previous monitoring results. There are no guideline values established for mercury in precipitation. However, for reference, the result was well below the drinking water standard in Japan of 500 ng/L for mercury. (See Table 4.

Annual mean mercury concentration in precipitation at Oga was 6.3 ng/L (weekly values in the range of 1.6 - 17.7 ng/L) by using improved analytical procedure. By using conventional analytical procedure, it was 4.7 ng/L, higher than the value of FY2015. For reference, the result of Oga was also well below the drinking water standard for mercury (See Table 5).

Table 4a Mercury concentration in precipitation at Cape Hedo by fiscal year (annual mean.

[Improved Analytical Procedure]

(Unit: ngHg/L)
Measured itemFY2016
Mercury concentration 6.6

Table 4b Mercury concentration in precipitation at Cape Hedo by fiscal year (annual mean.
[Conventional Analytical Procedure]

(Unit: ngHg/L)
Measured itemFY2008FY2009FY2010FY2011FY2012FY2013FY2014FY2015FY2016
Mercury concentration 3.4 3.1 2.4 3.0 1.9 2.2 1.4 2.0 4.3

Table 5a Mercury concentration in precipitation at Oga (annual mean)
[Improved Analytical Procedure]

(Unit: ngHg/L)
Measured itemFY2016
Mercury concentration 6.3

Table 5b Mercury concentration in precipitation at Oga (annual mean)
[Conventional Analytical Procedure]

(Unit: ngHg/L)
Measured itemFY2014FY2015FY2016
Mercury concentration 2.5 2.9 4.7

Note: FY2014 average value was calculated from the data starting on 25 August, 2014, when the monitoring program began.

(3) Metal Element Concentration in Aerosol.

In this monitoring survey, to understand the relationship between atmospheric mercury concentrations and other metallic element concentrations in aerosols, 17 hazardous elements and six index elements have been observed since FY2009 at Cape Hedo. (See Appendix 2 for details) Among the above elements, the results of six major metal elements (nickel, arsenic, manganese, lead, cadmium, and chromium) are shown in Table 6.

In FY2016, the annual mean concentrations of nickel, arsenic, manganese, lead, cadmium, and chromium in aerosols at Cape Hedo were 0.73 ngNi/m3, 0.75 ngAs/m3, 3.0 ngMn/m3, 3.2 ngPb/m3, 0.13 ngCd/m3, and 0.67 ngCr/m3, respectively. The weekly values were in the range of 0.18-1.9 ngNi/m3, 0.054-2.5 ngAs/m3, 0.21-10 ngMn/m3, 0.088-10 ngPb/m3, 0.0098-0.39 ngCd/m3, and nd* -2.4 ngCr/m3, respectively.

* "nd" indicates values less than the minimum limit of determinatio.

These values did not significantly deviate from the previous monitoring results but were slightly lower among the past 10 years. The results of nickel, arsenic, and manganese were well below the "guideline value for reduction of health risk by harmful air pollutants".

Table 6 Metal element concentrations in aerosols at Cape Hedo by fiscal year (annual mean)

(Unit: ng/m3)
Measured itemGuideline
value
FY2007FY2008FY2009FY2010FY2011FY2012FY2013FY2014FY2015FY2016
Nickel
(Ni)
25 0.76 0.59 0.87 0.95 0.99 1.1 1.8 1.5 1.2 0.73
Arsenic
(As)
6 1.4 0.68 0.85 0.83 0.76 0.99 0.98 1.1 0.77 0.75
Manganese (Mn) 140 6.0 3.4 6.7 5.5 4.6 7.4 4.9 6.6 3.8 3.0
Lead
(Pb)
- 12 4.6 5.2 5.7 5.0 7.3 6.9 6.5 3.5 3.2
Cadmium
(Cd)
- 0.25 0.13 0.17 0.16 0.12 0.17 0.19 0.20 0.13 0.13
Chromium
(Cr)
- 0.83 0.52 1.1 1.1 0.87 1.3 1.2 1.4 0.70 0.67

Note: "guideline value" indicates the "guideline values for reduction of health risk by harmful air pollutants" in Japan.

4. Future Action

The results obtained through this monitoring survey are meaningful as a basis of understanding the behavior and status of atmospheric mercury in Asia-Pacific region and also in evaluating the effectiveness of the Minamata Convention on Mercury in the future. Therefore, the MOE of Japan will continue to conduct monitoring surveys and to widely provide data and report on the results.

Appendix 1 Outline of monitoring sites

Table Outline of monitoring site.
site Cape Hedo Atmosphere and Aerosol Monitoring Station:CHAAMS
address Naganehara 1000, Ginama , Kunigami-son, Kunigami-gun, Okinawa
location 26.87°N, 128.26°E
overview CHAAMS is the monitoring station established and operated by the National Institute for Environmental Studies, Japan, for aerosols and gases in the atmosphere in order to understand transboundary air pollution.
It is located in the north end of the Okinawa island, where no anthropogenic pollution source of hazardous metals is in the surrounding area.
Cape Hedo is the optimum location in Japan from which to monitor the atmospheric conditions in East Asia, as air masses from Japan, Korea, China, and Southeast Asia, can be sampled, depending on the season.
site Oga peninsula
address Izumidai 3-2, Funagawaminato-funagawa, Oga-shi, Akita
location 39.89°N, 139.85°E
overview Oga peninsula site is set up adjacently to Funakawa Ambient Air Pollution Monitoring Station operated by Akita prefecture.
It is located in the south side of the Oga peninsula that protrudes into Japan Sea.
There is no source of mercury in surrounding area. Therefore, it is suitable for observing background mercury concentration in the northern part of Japan.

Appendix 2 Sampling and analytical method of different mercury forms, mercury concentration in precipitation, and other metal elements in aerosols

ComponentMeasurement itemsSampling and analytical methodsSite
Atmosphere Mercury Mercury forms
(GEM, GOM, PBM)
Continuous measurement with TekranR mercury speciation system Cape Hedo Oga
Particulate matter 17 hazardous elements Pb, Cd, Cu, Zn, As, Cr, V, Ni, Se, Sb, Ba, Co, Mn, Sn, Te, Tl, Be 7 days continuous sampling by using a low-volume sampler and. analyzed by ICP/MS Cape Hedo
6 index elements
Al, Fe, Ca, Na, Mg, K
Precipitation Hg Sampling by using an automatic
wet-only sampler and analyzed by CVAAS (EPA method 1631)
Cape Hedo Oga

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