Health & Chemicals

FY2014 Result on Background Monitoring Survey for Atmospheric Mercury Concentration, etc. (notice)

Since fiscal year 2007, Ministry of the Environment (MOE) has been conducting a background monitoring survey for atmospheric mercury concentration, etc. at Cape Hedo in Okinawa where the direct effect from domestic emission sources is minimal, the results of which will contribute to the international mercury management plan.

The results of the FY2014 survey showed mercury concentrations in the air and precipitation at Cape Hedo well below the national guideline values, and these values were lower than those of the previous years. Since August 2014, monitoring in OGA Peninsula, Akita Prefecture has been started. The result values on mercury concentration in atmosphere and precipitation at the Oga station did not have significant deviation from previous monitoring results at Cape Hedo.

1. Background

The United Nations Environment Programme (UNEP) has initiated its activities on mercury pollution at global level and has since then continued the international responses on mercury pollution. The recent development includes the establishment of the Intergovernmental Negotiating Committee (INC) in 2009, and its five sessions which made the agreement of the name and its text of the Convention by January 2013. Following it, the Diplomatic Conference on the Minamata Convention on Mercury took place in Minamata, Kumamoto in October the same year.

Act on Preventing Environmental Pollution on Mercury and the amendment of the Air Pollution Control Act were promulgated in June 2015 in order to promote the early conclusion and the comprehensive measures on mercury management.

Ministry of the Environment (MOE) has been conducting, since fiscal year 2007, a background monitoring survey for atmospheric mercury concentration, etc. at Cape Hedo in Okinawa where the direct effect from domestic emission sources is minimal, the results of which will contribute to the international mercury management plan . Since FY2010, the annual monitoring results have been published when the reliability of monitoring data was ensured due to the accumulation of the data.3

Since August 2014, another monitoring site in Oga Peninsula, Akita prefecture has started its operation. The following is the result of the monitoring survey in FY2014.

2. Survey overview

(1) Speciation of mercury

Mercury in atmosphere exists in various forms: the majority of it accounts for elemental (or metallic) mercury, and the remaining in other forms such as oxidized mercury and the particles in suspension (particle-bound mercury). The different forms of mercury behave differently in the air.

This survey aims to provide a basis on international mercury emission and trend of its concentration, and the effect of such mercury to the environment in Japan. The concentration of atmospheric mercury in different forms, and mercury deposited with precipitation were analyzed at Cape Hedo as the national background monitoring site (See Table 1).

A survey point in Oga Peninsula in Akita prefecture was added in August 2014 for monitoring the background level in Northern part of Japan.

(2) Monitoring sites

- Okinawa: Cape Hedo
Cape Hedo Atmosphere and Aerosol Monitoring Station, The National Institute for Environmental Studies
(Ginama, Kunigamison-aza, Kunigami, Okinawa Prefecture)

- Akita: Oga Peninsula
(adjacent to the Akita Funakawa Monitoring Station, Izumidai, Funagawa-aza, Funakawaminato, Oga city, Aikta Prefecture)

(3) Monitoring methods, survey items, and monitoring frequency

Atmospheric monitoring was conducted continuously by the ambient air monitor equipped with speciation feature. The rain-water was captured by the a precipitation collector and the mercury concentration was analyzed based on a method specified by the United States Environmental Protection Agency (EPA).

Table 1 Monitoring items and frequency
Category Survey item Measurement frequency
Gaseous Metallic mercury (GEM) Continuous (16 times per day)
Oxidized mercury (GOM) Continuous (8 times per day)
Particle-bound mercury (PBM)
Mercury concentration in precipitation Weekly (7-day continuous sampling)

* "Metallic mercury" in this survey refers to gaseous, elemental mercury in the air (Hg0). "Oxidized mercury" refers to atmospheric gaseous oxidized mercury (Hg2+), and "particle-bound mercury" describes mercury which is suspended or bound to floating particles in the air.

* The monitoring method in this survey is different from the one for mercury monitoring in the air pollutant monitoring survey based on the Air Pollution Control Act.

3. Summary of survey result

(1) Atmospheric mercury concentration

Annual average concentration values of total mercury in atmospherewere 1.7 ngHg/m3 in Cape Hedo, and 1.6 ngHg/m3 in Oga Peninsula, which were well below the guideline value of atmospheric mercury concentration (i.e. annual average value 40 ngHg/ m3)

Mercury in the atmosphere is mostly composed of metallic mercury, and the percentage of oxidized mercury and particle-bound mercury were less than 1%.

While annual mercury concentrations of both total and each species at Cape Hedo have remained largely unchanged, the results of this fiscal year were slightly lower than the results of previous years, consecutively from last year (see Table 2 for details).

It should be noted that the trial period up to fiscal 2003 includes limited number of days for monitoring.

Table 2 Atmospheric mercury concentration at Cape Hedo by fiscal year
(Unit: ngHg/m3)
FY2007 FY2008 FY2009 FY2010 FY2011 FY2012 FY2013 FY2014
Average 1.5 1.8 2.2 1.9 2.1 2.0 1.7 1.7
Average 0.001 0.002 0.002 0.001 0.002 0.002
-bound mercury
Average 0.002 0.002 0.002 0.002 0.004 0.004
Total Average 2.2 1.9 2.1 2.0 1.7 1.7

* The fiscal 2007 average value is calculated from data starting on 16 October when the monitoring program began. The annual average is obtained using the total concentration of oxidized mercury and particulate mercury calculated from the data in October 2009and onward when stable monitoring was established.

Table 3 Atmospheric mercury concentration in Oga Peninsula (unit ngHg/m3)
Measured items Statistical value From August 2014 to March 2015
Metallic mercury Average 1.6
Oxidized mercury Average 0.002

* Average values are calculated from data starting on 8 August, 2014 when the monitoring program began.

(2) Mercury concentration in precipitation

Annual average of mercury concentration in precipitation in Cape Hedo is 1.4 ng/L, which was a lower than the values in previous years. The average value in OGA Peninsula was 2.5 ng/L. Though no guideline value is established for mercury in rain water, the result is well below the drinking water standard of 500 ng/L for mercury as a reference.

Table 4 Precipitation mercury concentration measured at Cape Hedo by year (unit: ng/L)
FY2008 FY2009 FY2010 FY2011 FY2012 FY2013 FY2014
Average 3.4 3.1 2.4 3.0 1.9 2.2 1.4
Page top