Passive Samplers Project

A new air quality measurement program using passive sampler is about to begin. This activity actually combines component of three separate studies

1) A pilot study funded by NOAA-US Weather Service, to use passive samplers at selected WMO-GAW stations.
2) A continuation of the use of passive samplers as part of the RAINS-Asia Phase II project funded by the Japan Trust Fund at the World Bank.
3) A pilot study demonstrating the use of passive sampler at both regional and urban scales, funded by  The Swedish Consultancy Fund at the World Bank.

These 3 elements are being coordinated together and collectively comprise a network of ~50 stations and are being done in collaboration and as a component of the IGAC-DEBITS programme.

This project aims are: 1) to repeat a previous network for sulfur dioxide(SO2) in Asia in background air; and 2) to extend the capacity to monitor more pollutants in background as well as urban air. The network will spread out to GAW's network in South America and Africa to provide a wide,exclusive and valuable data set that can be used for variety of purposes including model evaluation and inter-comparision with other methods. Several stations from previous studies in Asia and GAW's network will be used together with some newly established sites. Sulfur dioxide(SO2), ammonia(NH3 ) and ozone(O3 ) will be monitored monthly at background sites and with short sampling peroids in urban site. The precursors of ozone such as formaldehyde(HCHO) and VOCS (volatile organic components) will be monitor in urban sites. This project is proposed to begin in this coming August and will run for twelve months.

Further details are presented below in The new air quality measurement project. In addition this website contains valuable infromation regarding the use of passive sampler.
We are interested in further collaborations and in dissemination of information regarding the use of passive samplers. If you have any question or comments or if you would like to contribute information to this site please contact our group.


The passive sampler is  a  simple device consisting  of an  impregnated filter or molecular sieve which  preferentially sorbs the gas to be analysed and a diffusion barrier to keep the sampling rate constant(usually an entrapped air volume) .  The samplers  provide a time-integrated loading of gases  and  are excellent for field measurement  since  no electricity, pumps, or other supporting equipment are needed.


Table of Contents
1)  Background
2)  Available informations from previous studies
3)  The new air quality measurement project
4)  Data Sharing


1) Background
The passive sampler was designed based on molecular diffusion of principles. The gas molecules  diffuse into the sampler and are collected on an impregnated filter or an absorbant material specific to each pollutants. measured and was kept sampling rate constant by a diffusion barrier. To ensure that gas is transported to the filter by molecular diffusion, the inlet region of the sampler covering with a fine mesh( stainless steel mesh with a thread diameter of 0.08 mm and mesh aperture of 0.125 mm) that can minimize the convective transport. Therefore, the sampling rate can be calculated using Fick's first law of diffusion across the entrapped air volume  from the perpendicular cross section area to transport direction and the distance that the gas has to diffuse.

Passive sampler have a variety of forms. For example,  long and narrow samplers(eg. diameter 10 mm and length 50 mm) provide a higher detection limit, while wider and shorter samplers ( eg.  diameter of 20 mm and length of 10 mm) provide a lower detection limit. At the same ambient concentrations the latter sampler has 20 fold increase in sampling rate.
It is crucial to impregnate the collective filter with proper chemical. It must be a solid and stable reagent that selectively and quantively chemisorbed the target species, and transforms it to another stables form in which other pollutants do not interfere is carefully selected.

The measurement of SO2 is done using passive sampler with  a sodium hydroxide(NaOH) impregnated cellulose filter.The sulphite is oxidised to sulphate during sampling and the sulphate amount is analyzed using suppressed ion chromatography.

For measurement of NO2 , a mixture of iodide,arsenite, and ethylene glycol  is  recommended as a sorbent. On  the filter  NO2 is converted to nitrite and then analyzed using FIA( flow injection analysis) spectrophotometry.

The measurement of NH3 is done using  a citric acid as an absorbent. Ammonia is converted to ammonium ion and then analyzed  using FIA( flow injection analysis) spectrophotometry.

The passive samplers have been developed for monitoring non-methane hydrocarbons(NMHCs). They are being used to measure C6 to C9 hydrocarbons in urban air quality monitoring networks in Europe. The sampler consists of swagelock fitting tubes with Tenax TA, a 35-60 mesh, and a porous polymer based on 2,6, diphenyl oxide adsorbent packing that can be directly analyzed by gas chromatograph.

Further   informations  can be obtained  from the WMO report written  by  Prof. Gregory R. Carmichael.  It's in an Adobe acrobat PDF file. If you didn't have this program, plz  down load  program from here.


2) Available information from previous studies

There are several air pollution monitoring projects using passive samplers.

2.1) Sweden's Experience
The passive samplers are used widely in Sweden. Passive sampling activities are an integral component and are used in conjunction with active sampling in the  Swedish monitoring network.

2.2) RAINS-Asia
A pilot monitoring program was conducted  as part of the RAINS-Asia projected funded by the World Bank and the Asian Development Bank.  The passive samplers deveoped by Martin Ferm at the Swedish Environment Research Institute(IVL) were used  to  obtain base-level data for future model evaluation., surface sulfur dioxide was monthly monitored  for a year  at  forty-five locations in Asia. The first sites staring  in December 1993 and February 1994  for others. Detail discussion of this project is available on WMO report. Extensive information such as  map of the sites, geographical location and monthly data  are now  available.

2.3) Other Acitivites
Dr. Greg Ayers ( CSIRO  Atmospheric research, Australia) is  using  a Ferm-type passive sampler to study  acid depostion in SE asia and tropical Australia.  There are some information about gas passive samplers, such as highlight, and method  of used.

Arun B. Shrestha and et. al are using Ferm-type passive sampler to monitor SO2 in Nepal.

There are some private companies that produce passive samplers.  The  SKC, Inc USA   have extensive information about passive sampler for organic vapors. The Ogawa & Co, USA inc have an ambient air passive sampler for NO-NO2 , NOx, SO2 , O3.

Dr. Martin Hooper( Monash University, Australia) and his group are using passive samplers to monitor  nitrogen oxide and formadehyde in an indoor environment in Australia. They are also  working on  8 passive sampler sites in Bangkok, Thailand.
Lynn Salmon( California Institue of Technology,USA) and her group have global ozone passive monitoring project. The first test peroid was performed on March 1999. They  will send passive sampler to ~ 500 stations around the world  for their second  test peroid in this coming August. They need some more coordinators and ask for help.

NPS ozone passive sampling program is using passive sampler from Ogawa & Co., USA, Inc.  Ozone is monitorted weekly  in severals US National Parks since 1995. Some information such as map of location, minitoring support documents, data from 1995-1998,
Spatial distribution studies, and seasonal ozonesummary  map are also available.

2.4) List of recent publish papers on passive samplers

2.4.1) G.P. Ayers, M.D. Keywood, R. Gillett, P.C. Manins, H. Malfroy and T. Bardsley.:1998, Validation of Passive Diffusion Samplers for SO2 and NO2. Atmospheric Environment, vol  32, no. 20, p 3587-3592.
2.4.2) Martin Ferm and Per-Arne Svanberg.:1998, Cost-efficient Techniques for Urban- and Background Measurement of SO2 and NO2. Atmospheric Environment , vol  32, no. 8, p 1377-1381.

2.4.3) Arun B. Shrestha, Cameron P. Wake, Jack E. Dibb, Pual A. Mayewski, Sallie I. Whitlow,
Gregory R. Carmichael and Martin Ferm.: 2000, Seasonal Variations in aerosol Concentrations and composition in the Nepal Himalaya.
Atmospheric Environment , 34, p 3349-3363.

2.4.4) A.K. Azad and T. Kitada.:1998, Characteristics of the air pollution in the city of Dhaka, Bangladesh in winterAtmospheric Environment, vol 32, no. 11,   p 1991-2005.

2.4.5) M.H. Garrett, M. A. Hooper and B. M. Hopper.:1999, Nitrogen Dioxide in Australian homes; Levels and Sources, Journal of the Air & Waste Management Association, vol 49, p76-81.

2.4.6) M.H. Garrett, M. A. Hooper and B. M. Hopper.:1997, Formaldehyde in Australian homes; Levels and Sources, Clean Air: The Journal of Clean Air and Environmental Quality, Vol 31, No 2, p28-32.

2.4.7) M.H. Garrett, M. A. Hooper and B. M. Hopper.:1997, Indoor Air Pollutants-Low levels Influence the Health of Children: Some Preliminary Results, Clean Air: The Journal of Clean Air and Environmental Quality, Vol 31, No 4, p37-40.

2.4.8)Shigehissa Uchiyama, Masae Asai,Shuji Hasegawa.:1999,A sensitive diffusion sampler for the determination of volatile organic compounds in ambient air, Atmospheric Environment, vol  33,  p 1913-1920.

2.4.9)Shigehissa Uchiyama,Shuji Hasegawa.:1999,A reactive and sensitive diffusion sampler for the determination of aldehydes and ketones in ambient air, Atmospheric Environment, vol  33,  p 1999-2005.

2.4.10) Ferm M. and Rodhe H.:1997 Measurements of air concentrations of SO2,  NO2,  and NH3 at rural and remote sites in Asia. Journal of Atmospheric Chemistry, vol 27, p 17-29.

Some available information  will be updated frequently  in this section


3) The new air quality measurement project

Totally ,  50 stations  in twelve Asian  countries ( China, India, Indonesia, Japan, Korea, Malaysia, Nepal, Philiphines, Singapore, Thailand, Laos and  Vietnam),  five African countries ( Algeria, Cameroon, Ivory Coast, Niger and South Africa), five South American countries ( Argentina, Brazil, Chile, Peru and  French Guyana) and an European country(Turkey) will be used  as  background and urban stations. Two types of sites are identified: regional and global; and urban/sub-urban. At the regional/global sites passive samplers will be used to obtain  1 year of data at each location using monthly exposure protocol. Ozone, SO2 and NH3will be measured at most stations. At many stations there will be the opportunity to perform an intercomparison with active ozone measurements.   At the urban/sub-urban sites additional species will be measured, including VOCs. The intensive set of measurements will be conducted using  shorter exposure times and will be done at selected intensive periods throughout the year. Details are presented below:

3.1)Map of proposed monitoring sites
3.2) Contact person and site details
3.2.1) GAW's contact person
3.2.2) CGRER's contact person
3.3) Operational details

3.3.1) Station information
a) French Guiana station
b) India station
c) Indonesia stations
d) Iovory Coast station
e) Kenya station
f) Lao stations
g) Malaysia stations
h) Nepal stations
i) Niger station
j) Peru station
k) Philiphines stations
l) South Africa station
m) Taiwan stations
n) Thailand stations
o) Turkey station
3.3.2) Instruction for regional site
a) English Version
b) Spanish Version
3.3.3) Instruction for urban site(English)

The overall project management will be carried out by Prof. Gregory R. Carmichael, at the University of Iowa, Center for Global & Regional Environmental Research, Iowa City, Iowa, USA. The sampler preparation and analysis will be conducted by This email address is being protected from spambots. You need JavaScript enabled to view it. , Swedish Environmental Research Institute(IVL), Goteburg, Sweden.The proposed begining of this project is September 1, 1999.


4) Data Sharing
The data obtain in this project will be shared among all participants within the project. It is envisioned that joint papers will be prepared.


1) WMO-GAW report  no 122 on Passive Samplers for Atmospheric Chemistry Measurements and their ROLE in GAW
2) The "Air Quality in Hong Kong 1986-1997" CD-ROM  from  The Air Service Group, Environmental Protection Department, Hong Kong