Health & Chemicals

FY2019 Results on Background Monitoring for Mercury in Atmosphere and Precipitation, and other Elements in Aerosols

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

The results of the survey in the Fiscal Year (FY) 2019 (April 1, 2019 through March 31, 2020) showed that mercury concentrations in the atmosphere and precipitation at Cape Hedo and Oga 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 and were well below for those having the guideline values.

1. Background Information

The MOEJ has been conducting a background monitoring survey for atmospheric mercury concentrations at 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.

Since August 2014, another monitoring survey at Oga has commenced.

2．Overview of the Survey

(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), which is the predominant form of mercury in the atmosphere, 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 basic information on the status of global mercury emission, the trend of atmospheric mercury concentrations, and the effects of these on the environment in Japan. The concentrations of atmospheric mercury, namely GEM, GOM, and PBM, mercury deposited with precipitation, and selected metal elements other than mercury were analyzed at Cape Hedo as the national background monitoring site where the direct effect from local emission sources is minimal (see Table 1).

A monitoring survey has also been conducted at Oga (see also Table 1) in order to monitor the background concentration level in northern Japan.

(2) Monitoring Sites (See Appendix 1 for detail)

・Cape Hedo, Okinawa Prefecture:

Cape Hedo Atmosphere and Aerosol Monitoring Station (CHAAMS), the National Institute for Environmental Studies, located in Ginama, Kunigami-son, Kunigami-gun, Okinawa

・Oga, Akita Prefecture:

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

(3) Monitoring Methods, Survey Items and Monitoring Frequency (See Appendix 2 for detail)

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

Table 1 Survey items and monitoring frequency

Category	Survey item	Monitoring frequency	Monitoring site
Atmospheric mercury component	Gaseous Elemental Mercury (GEM)	Continuous (16 times/day)	Cape Hedo, Oga
	Gaseous Oxidized Mercury (GOM)	Continuous (8 times/day)
	Particle-Bound Mercury (PBM)	Continuous (8 times/day)
	Other metal elements in aerosols (17 hazardous elements and 6 index elements)	Weekly (7-day continuous sampling)	Cape Hedo
Precipitation components	Mercury concentration in precipitation	Weekly (7-day continuous sampling)	Cape Hedo, Oga

Note 1: "Gaseous Elemental Mercury" in this survey refers to the elemental mercury existing in the air (Hg⁰). "Gaseous Oxidized Mercury" refers to the oxidized mercury (Hg²⁺) in gaseous form, 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 hazardous air pollutant monitoring survey conducted under the Air Pollution Control Act. (refer to Annex)

3. Summary of Survey Result

(1) Atmospheric Mercury Concentration

Annual mean concentrations of the sum of all mercury forms in the atmosphere were 1.7 ngHg/m³ at Cape Hedo and 1.5 ngHg/m³ at Oga, both of which were well below the guideline values for hazardous air pollutants to reduce health risks (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 (see Table 4 and 6 in the Annex).

Annual mean concentrations of GEM and total atmospheric mercury at Cape Hedo had decreased until FY2013 from FY2008 and FY2009, respectively. From FY2013 to FY2019, the concentrations have remained at similar levels. (see Table 2 and Table 5 in the Annex for detail).

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

(Unit: ngHg/m³)

Measured item	FY2007	FY2008	FY2009	FY2010	FY2011	FY2012	FY2013	FY2014	FY2015	FY2016	FY2017	FY2018	FY2019
Gaseous Elemental Mercury	1.5	1.8	2.2	1.9	2.1	2.0	1.7	1.7	1.6	1.7	1.6	1.6	1.7
Gaseous Oxidized Mercury	－	－	0.001	0.002	0.002	0.001	0.002	0.002	0.001	0.002	0.002	0.002	0.002
Particle- Bound Mercury	－	－	0.002	0.002	0.002	0.002	0.004	0.004	0.002	0.003	0.002	0.002	0.002
Total	－	－	2.2	1.9	2.1	2.0	1.7	1.7	1.7	1.7	1.6	1.6	1.7

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

Annual mean concentrations of both the total and each mercury form at Oga have remained at similar levels from FY2014 but were slightly lower in FY2019 (see Table 3 and Table 7 in the Annex for further detail).

Table 3 Atmospheric mercury concentration at Oga (annual mean)

(Unit: ngHg/m³)

Measured item	FY2014	FY2015	FY2016	FY2017	FY2018	FY2019
Gaseous Elemental Mercury	1.6	1.6	1.6	1.6	1.6	1.5
Gaseous Oxidized Mercury	0.002	0.003	0.002	0.003	0.003	0.002
Particle-Bound Mercury	0.009	0.009	0.011	0.009	0.008	0.006
Total	1.6	1.6	1.6	1.6	1.6	1.5

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

(2) Mercury Concentration in Precipitation

Annual mean concentration of mercury in precipitation was 5.6 ngHg/L at Cape Hedo and 6.0 ngHg/L at Oga. There are no guideline values established for mercury in precipitation, however, for reference, the result was well below the Environmental Quality Standards for Water Pollution in Japan of 500 ngHg/L for mercury. (See Table 4, and Table 9 and 11 in the Annex for detail)

Table 4 Mercury concentration in precipitation at Cape Hedo and Oga
by fiscal year(annual mean)

(Unit: ngHg/L)

Monitoring site	FY2016	FY2017	FY2018	FY2019
Cape Hedo	6.6	4.8	3.9	5.6
Oga	6.3	5.7	6.0	6.0

(3) Metal Element Concentrations in Aerosols excluding Mercury

In this monitoring survey, 17 hazardous elements and six index elements have been monitored since FY2009 at Cape Hedo in order to understand the relationship between atmospheric mercury concentrations and other metallic element concentrations in aerosols. (See Table12 in the Annex for details) Among the above elements, the results of six major metal elements (nickel, arsenic, manganese, lead, cadmium, and chromium) are shown in Table 5.

In FY2019, the annual mean concentrations of manganese, nickel, and arsenic in aerosols at Cape Hedo were 3.7 ngMn/m³, 0.86 ngNi/m³, and 0.66 ngAs/m³, respectively, which were below the guideline values for hazardous air pollutants to reduce health risks.

The annual average concentration of chromium, cadmium and lead, of which the guideline values have not been established, were 2.1 ngCr/m³, 0.083 ngCd/m³ and, 2.1 ngPb/m³respectively in FY2019.

The concentrations of arsenic, cadmium and lead showed the lowest values of the whole observation period. On the other hand, the concentration of chromium recorded the highest value of the whole observation period.

Table 5 Metal element concentrations in aerosols at Cape Hedo by fiscal year (annual mean)

(Unit: ng/m³)

Measur- ed item	Guide-line value	FY2007	FY2008	FY2009	FY2010	FY2011	FY2012	FY2013	FY2014	FY2015	FY2016	FY2017	FY2018	FY2019
Chromium (Cr)	－	0.83	0.52	1.1	1.1	0.87	1.3	1.2	1.4	0.69	0.65	0.91	1.8	2.1
Manganese (Mn)	140	6.0	3.4	6.7	5.5	4.6	7.4	4.9	6.6	3.7	2.9	4.0	4.9	3.7
Nickel (Ni)	25	0.76	0.59	0.87	0.95	0.99	1.1	1.8	1.5	1.1	0.74	0.98	0.97	0.86
Arsenic (As)	6	1.4	0.68	0.85	0.83	0.76	0.99	0.98	1.1	0.74	0.73	0.73	0.70	0.66
Cadmium (Cd)	－	0.25	0.13	0.17	0.16	0.12	0.17	0.19	0.20	0.13	0.13	0.11	0.096	0.083
Lead (Pb)	－	12	4.6	5.2	5.7	5.0	7.3	6.9	6.5	3.4	3.1	2.9	2.7	2.1

Note:"guideline value" indicates the "guideline values for hazardous air pollutants to reduce health risks" 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 MOEJ 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 sites

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 expected in the surrounding area. Cape Hedo is the optimum location in Japan 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

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 expected in the surrounding area.

Cape Hedo is the optimum location in Japan 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 was 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 the Sea of Japan. There is no source of mercury in the surrounding area. Therefore, it is suitable for observing background mercury concentration in the northern part of Japan.

Site

Oga Peninsula

Address

Izumidai 3-2, Funagawaminato-funagawa, Oga-shi, Akita

Location

39.89°N, 139.85°E

Overview

Oga peninsula site was 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 the Sea of Japan.

There is no source of mercury in the surrounding area. Therefore, it is suitable for observing background mercury concentration in the northern part of Japan.

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

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

Attached Documents

平成31年度大気中水銀バックグラウンド濃度等のモニタリング調査結果について（別添）

FY2019 Results on Background Monitoring Survey for Atmospheric Mercury and Other Metal Element Concentrations (attachment) [PDF 2.0 MB] (in Japanese)