Health & Chemicals

FY2018 Results on Background Monitoring Survey for Atmospheric Mercury and Other Metal Element Concentrations 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 Fiscal Year (FY) 2018 (April 1, 2018 through March 31, 2019) survey 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.

The results of this background monitoring survey for atmospheric mercury at Cape Hedo were compiled and published as an academic article.

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 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 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, 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 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).

Table 1 Survey items and monitoring frequency

CategorySurvey itemMonitoring frequencyMonitoring 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)

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 both 1.6 ngHg/m3 at Cape Hedo and Oga, both of which were well below the guideline value for reduction of health risk by hazardous 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 (see Annex Table 4 and 6).

Annual mercury concentrations of GEM and total atmospheric mercury at Cape Hedo have been decreasing from FY2008 or FY2009 to FY2018, but have remained at virtually similar level after FY2013 (see Table 2 and Annex Table 5).

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

(Unit: ngHg/m3)

Measured
item

FY2007FY2008FY2009FY2010FY2011FY2012FY2013FY2014FY2015FY2016FY2017FY2018

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

Gaseous
Oxidized
Mercury

0.001 0.002 0.002 0.001 0.002 0.002 0.001 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

Total

2.2 1.9 2.1 2.0 1.7 1.7 1.7 1.7 1.6 1.6

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 mercury concentrations of both the total and each mercury form at Oga have remained at virtually similar level as the values from the past surveys (see Table 3 and Annex Table 7 for further detail)

Table 3 Atmospheric mercury concentration at Oga (annual mean)

(Unit: ngHg/m3)

Measured
item

FY2014

FY2015

FY2016

FY2017

FY2018

Gaseous Elemental Mercury

1.6 1.6 1.6 1.6 1.6

Gaseous Oxidized Mercury

0.002 0.003 0.002 0.003 0.003

Particle-Bound Mercury

0.009 0.009 0.011 0.009 0.008

Total

1.6 1.6 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

Annual mean mercury concentration in precipitation was 3.9 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 drinking water standard in Japan of 500 ngHg/L for mercury. (See Table 4, and Annex Table 9 and 11 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

Cape Hedo

6.6 4.8 3.9

Oga

6.3 5.7 6.0

(3) Metal Element Concentration 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 Annex Table12 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 FY2018, the annual mean concentrations of nickel, arsenic, and manganese in aerosols at Cape Hedo were 0.97 ngNi/m3, 0.70 ngAs/m3, and 4.9 ngMn/m3, respectively, which were below the "guideline values for reduction of health risk by hazardous air pollutants".
The annual average concentration of lead, cadmium and chromium, of which the "guideline values" have not been established, were 2.7 ngPb/m3, 0.096 ngCd/m3 and 1.8 ngCr/m3, respectively in FY2018.

The concentrations of lead and cadmium showed the lowest values of the whole observation period, while the concentration of arsenic is the second lowest value of the whole observation period. On the other hand, the concentration of chromium (Total chromium) measured as the sum of metallic chromium (chromium (0)), trivalent chromium (chromium (III)), and hexavalent chromium (chromium (VI)), recorded the highest value among surveys since FY 2007.

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

(Unit: ng/m3)

Measur-
ed item

Guide-line
value

FY2007FY2008FY2009FY2010FY2011FY2012FY2013FY2014FY2015FY2016FY2017FY2018

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

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

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

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

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

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

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

4. Publication

The results of this background monitoring survey for atmospheric mercury at Cape Hedo were compiled into an academic article and were published in MDPI online journal "Atmosphere" on June 30, 2019.

Title: Long-Term Observation of Atmospheric Speciated Mercury during 2007-2018 at Cape Hedo, Okinawa, Japan.

Atmosphere 2019, 10(7), 362; https://doi.org/10.3390/atmos10070362

5. 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 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 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
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
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, Revision E)

Cape
Hedo
Oga

Attached Documents

平成30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)

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