an overview by Ramon Guardans (original text, not updated)
1 Introduction
The growing interest in international fora(1) that have carried out advanced research on the potential impacts on health and ecosystems of the long range transport of air pollution has promoted several international co-operative efforts to establish with as much detail and accuracy as possible the main magnitudes characterising the processes of emission, transport, deposition and potential damage to human health and the environment resulting from an increased exposure to heavy metals and persistent organic pollutants.
Table 1 Simplified layout of the main elements that participate in the process of assessing and responding to potential risks to the environment and health. 2 The items of principal interest for ICP IM are in bold type and refer to ecosystems.
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Research
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Risk assessment
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Integrated Assessment
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Lab.&field data on effects
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Hazard identification
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Extrapolation
Characterization/abatement from high to low doses
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Dose-response
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Risk
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Field measurement of
exposure and characterization of populations
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Exposure assessment
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The regional and global nature of the processes make international efforts to generate comparable measurements the only basis on which further knowledge on the pools and fluxes can rest. A recent UNECE workshop(3) concluded that while the number of measurements of HM was large the intercomparability was low and that only a few POPs had been measured at a few sites.
To achieve a better quantitative understanding of the relative impact of ongoing, past and natural emissions of heavy metals it is important to improve the coverage and resolution of the assessment of the current pools and fluxes of these substances in the environment.
For persistent organic pollutants and some metals the reversibility of deposition processes and the consequent re-emission make soils and vegetation relevant sinks and sources as well as receptors at risk and therefore the assessment of existing concentrations in different media is an important step to develop effective control measures based on an improved understanding the current status of the relevant pathways and potential effects of the different substances under consideration in different environments.
The objective of the cooperative effort in ICP IM is to compile and review physicochemical properties and environmental measurements of POPs and HMs and assemble these data in a form suitable for input to CLRTAP and global scale modelling used to identify long term and large scale trends in concentration in the environment of the different pollutants and assess the occurring and potential effects on ecosystems of the long range atmospheric transport heavy metals and persistent organic pollutants. This is a difficult task given the very large number of substances of potential interest.
The contribution of ICP IM in the forthcoming years could be very significant if comparable and simultaneous measurements of atmospheric concentrations, wet, bulk and dry deposition, concentration in soils, sediments, water and vegetation (lichens, mosses, needles, leafs, bark) could be obtained for a range of different ecosystems in different regions such as the ICP IM network.
Such information would be of very great value to a) enhance the precision of vegetation samples as indicators, b) improve the estimates of local pools and fluxes and of uncertain, substance and site specific parameters on which exposure estimates can be developed and c) by reporting these information's to the modelling community improve the accuracy of extensive regional modelling of long range atmospheric transport of HM and POPs.
An other line of work, that at that stage should be of a lower priority but in the long term is a key element to assess the potential impacts on ecosystems and health, is the measurement of concentrations in the nodes of the trophic web, the quantitative assessment of pathways by which pollutants bioaccumulate and ultimately accumulate in sensitive tissues of individuals in human and animal populations.
2 List of priority elements and substances.
Concerning heavy metals the priority elements identified by the Preparatory Working Group for an initial protocol are Pb, Cd and Hg.
Future developments might include Cu, Zn, As, Cr and Ni.
Among the priorities that have been identified (Pacyna 1993, De Leeuw 1996) are the evaluation of Hg re-emission from aquatic and terrestrial environments, and the natural emissions of Hg. As well as the chemical forms in which metals are found in the environment.
Concerning Persistent Organic Pollutants, there are two kinds of lists to be considered on the one hand the list arrived at in the UN/ECE/Preparatory Working Group by applying a series of screening criteria and aimed at focusing policy action on the abatement of transboundary fluxes of these substances and on the other hand there is the list of compounds that existing networks and laboratories have been measuring and that from a practical and analytical point of view are recommended for an initial phase of a measuring effort.
The Executive Body of LRTAP at its 14th session (Nov 1996) indicates the following 16 substances to be considered in the negotiations, starting in January 1997, for a UNECE/LRTAP binding protocol:
aldrin, chlordane, chlordecone, DDT, dieldrin, dioxins and furans, endrin, heptachlor, hexabromobiphenyl , hexaclorobenzene, mirex, PAHs(*), PCBs, pentachlorophenol, toxaphene, lindane and short chain chlorinated paraffins.
The workshop (EMEP 1996) recommended for an initial phase of measurements
- PAHs (Benzo(a)pyrene)
- Polychlorinated biphenyls PCB IUPAC-28 52, 101, 118, 153, 138, 180.
- Hexachlorobenzene HCB
- gamma and alpha Chlordane
- Lindane
- a-Hexachlorocyclohexane HCH
- DDT/DDE
It is understood that the main focus of this manual is to inform interested laboratories on how to prioritize and plan the sampling strategy and carry out the field work, the analytical work will only be considered by reference inasmuch as it is assumed that users of the manual will in most cases rely on experienced laboratories to do the measurements on the samples.
Several kinds of measurements are of great relevance, in the first place to obtain direct, comparable and simultaneous measurements in different media (air/water/soil/biota) is necessary to establish seasonal variation, and temporal and spatial trends on a regional and global basis, second to interpret those measurements and to improve the precision of models (Pacyna 1996, De Leeuw 1996) there is urgent need for field information on the chemical forms and characteristic coefficients (i.e. Vapour-particle partitioning, Octanol air partition coefficient, Octanol water partition coefficient, Water solubility, Henry's law constant) for different substances in different environmental conditions (Bidleman 1988, Mackay et al 1995 Sánchez-Camazano 1993a, b, Sánchez Martin 1993, Mackay 1981, Suntio 1988, Murray 1996)
3 Methods, guidance on how to measure them in the field.
3.1 Air
These aspects are also covered in other sections of the manual dealing with other subprogrammes but repeating some of it here helps to have the wide picture.
HM Air sampling (AMAP 93, NILU and IVL 1993)
Cd and Pb: Most frequently used method is by particle filtration on an appropriately low background filter.
Hg (gas-phase): Recommended (with pre-concentration) two sequential collectors using gold-amalgamation technique.
Hg (particulate): Air filtration using quartz fibre filter or quartz-wool plugs.
Sampling frequency: 24 hour measurements during 3-4 weeks campaigns.
The detection limit of Pb/Cd will determine if it is possible to measure on a daily basis at a specific site.
Analysis (Maenhaut 89)
Extraction from filter
Inductively Coupled Plasma -Mass Spectrometry (ICP-MS) is recommended (Iverfeldt 1996) as reference method for Pb, Cd, Cu, Zn, As, Cr and Ni in air.
Hg (both phases): recommended cold-vapour atomic fluorescence spectrometry (CVAFS)
POPs Air sampling
Recommended (AMAP 1993) high volume sampler (20-25 m3h-1 and a volume of 1000-2000 m3 per sample are common values) with glass or quartz filter and solid absorbent trap (polyurethane foam) for both the gas and particle phases of: three chlorine and higher PCBs, DDTs, Chlordanes, Dieldrin, Toxaphene, three ring and higher PAHs, Dioxins, Dibenzofurans and Mirex.
HCB, HCH: Recommended use of amberlite XAD-4 and XAD-8 macroporous resins instead of polyurethane (polyurethane foam is acceptable for HCB only in winter Arctic conditions)
Analysis
Extraction from filter and trap: Soxhlet apparatus with solvents
PCB and pesticides: GC-ECD
Dioxin, Toxaphene, Dibenzofurans: GC-MS
PAHs: GC-MS or HPLC with fluorescence detection.
3.2 Deposition
Dry deposition estimates come from measurements of the gaseous and particulates in air monitoring with the high volume samplers coupled to a deposition velocity (obtained from other experiments or theory). Wet deposition are more direct. For both organics and trace metals in precipitation, collection of rain and snow is done with large aperture wet-only collectors. Since the volume of water required to make an accurate determination of organics in water is on the order of litters, the aperture of the organics collectors are bigger than for inorganics or trace metals in precipitation.
HM Deposition sampling
Sampling for trace metals in precipitation is not an easy measurement to make as there are a number of problems that can distort the real concentration in rain. Two major problems are that many elements have affinity for the collection bucket or bag, and the very real possibility of contamination from the many metal surfaces in the vicinity. Obtaining Bulk collector technique is preferred, compared to the wet only collector, as the reference method for deposition sampling for trace metals. The same type of bulk collector should be used at all stations. (Barrie 1989, IAND 1994. Iverfeldt 1996).
Analysis
Pb, Cd: ICP-MS
Hg: CVAFS
POPs Deposition sampling
The National Waters Research Institute, Canada in the Integrated Atmospheric Deposition Network, uses MIC organic precipitation collector that consist of a coated metal funnel of 0.2 m2 area which drains to a wetted column of XAD-2 resin. The column removes the organics from the precipitation passing through it by gravity flow. The column is kept wet by use of a U-Tube at the column outlet. The collection columns are kept in place for 14-day periods. The columns are removed, placed in teflon bags, stored in a cooler and shipped to the laboratory with the comment sheets. (Burniston 1994, Kawamura 1986, Farmer 1986, Mazurek 1987, McVeety 1988, Murray 1992, Leister 1994, Brorström-Lundén. 1996, )
Analysis
Extraction from filter and trap: Soxhlet apparatus with solvents
PCB and pesticides: GC-ECD
Dioxin, Toxaphene, Dibenzofurans: GC-MS
PAHs: GC-MS or HPLC with fluorescence detection.
As a good and complete illustration and as base to (dis) agree on recommended methods we quote from (Iwata 1994):
"Polyurethane foam plugs (31 mm, length 50 mm) were used as adsorbents for air sampling.(...) Six precleaned plugs were packed in a glass column ( 27 mm, 390 mm) with polyethylene caps at both ends and sealed in polyethylene bags until sampling. Air sampling was carried out using the prepared glass column connected with a low volume air pump. About 26-115 m3 of air (flow rate 35-38 litters/min) was collected for from several hours to two days. The flow rate was monitored at the beginning and the end of the sample.
"For water sampling, precleaned Amberlite XAD-2 (styrenedivinylbenzene copolymer macroreticular) resin packed in a glass column (i.d. 18 mm, length 50 mm) was used as adsorbent. Five to 75 litters of river and estuarine water were collected in polyethylene containers, which were washed previously with acetone, and immediately passed through the XAD-2 resin column by siphonage at a flow rate of less than 0.3 liters/min. After adsorption of organochlorines in the column, several ml of formalin were added to the column to avoid biological degradation of these compounds.
"Surface sediment samples (0 - 5 cm) were collected using a stainless-steel grab sampler. Sediments were well mixed in a precleaned aluminium plate and preserved in a polyethylene bag with several ml of formalin.
"The air, water, and sediment samples were transported to the laboratory and stored at -20ºC until analysis.
The methods to extract the substances from the samples and to analyse them are also well described in the literature (Murray 1996, Leister 1994, Brorström-Lundén. 1996, Iwata 1993) and are beyond the scope of this chapter now.
3.3 Soil
There is no general agreement on a reference method for sampling and measurement specifically for HM or POPs a frequent reference is (NCM 1988). The section in this manual for soil water and soil matrix sampling is a starting point but the corresponding provisions to avoid contamination of the samples should be implemented. The following laboratory methods for HM are cited by (AMAP 1993): ISO/CD 11466, ISO/TC 190/SC 3/WG 1 N 24.
There is much work to be done to generate comparable quantitative information on the influence of soil properties and environmental conditions on HM and POPs mobility and bioavailability in soils (i.e. Sánchez-Camazano 1993a, b, Sánchez Martin 1993, Mackay 1981, Suntio 1988, Torstenson, 1992, Schinner 1993)
3.4 Plant material
Many efforts have been carried out over the last decades to interpret measurements of HM from plant material, the relative scarcity of comparable and simultaneous air, deposition and plant measurements over extended periods has hindered the accuracy of these methods, however several large scale surveys (NCM 1992) have been carried out successfully.
HM
Humus
NCM 1988, Field Manual Nat. Board of Waters and Env., Finland 1989, ICP Forests Manual.
Lichens
ISO/CD 11466, ISO/TC 190/SC 3/WG 1 N 24.
Mosses
NCM 1992
Mushrooms
NCM 1988
ISO/CD 11466, ISO/TC 190/SC 3/WG 1 N 24.
Leaf/needle
ICP Forests
POPs
A review (Simonich 1995a) and several papers (Simonich 1994, Calamari 1991, Simonich 1995b) present the great potential and the limitations of vegetation samples to carry out regional surveys. The following processes are listed in a simplified uptake model (Simonich 1995a)
Vapour-particle partitioning
Octanol air partition coefficient
Octanol water partition coefficient
Water solubility
Henry's law constant
Organic content of the soil
Plant species
Plant surface area
Plant lipid concentration
Most of these coefficients are substance specific and will vary with environmental conditions and have been identified as important sources of uncertainty in models (Wania 1995, Murray 1996, De Leeuw 1996). It must be stressed that the interpretation of measurements obtained from plant material are still subject to many sources of uncertainty, the work in this program could help significantly in reducing some of them and consequently improving the accuracy of the assessments of pools and fluxes from a local to a regional and global scale.
It is also important to underline that the information on the atmosphere-water-soil-vegetation exchange of Persistent Organic Pollutants is relevant to understand the potential impact climate change in the long range transport of POPs.
3.5 Animal tissues
Many sampling programs and reference methods have been developed to sample animal tissues and small marine and freshwater organisms. We refer the reader at that stage to good summaries such as (Muir 1988, Murray 1994 and 96, SEPA).
3.6 Paleoenvironments
Many interesting attempts have been made (Valette-Silver 1992) at using sediments and peat bog cores to establish the long term record of deposition for heavy metals and persistent organic pollutants, historic samples in museum collections have also been to establish deposition levels in the recent past (Jones 1992). Sampling and analytical methods are similar to what has been described, the interpretation of these data present many problems that configure a worthy challenge for future research.
4 QA/QC
The complexity of the sampling and analytical procedures, the low concentrations that are measured and the large risk of artefact and contamination make an careful and tight QA/QC set of procedures absolutely necessary to achieve any kind of meaningful results on a regional basis. Recent work in existing networks ( EMEP 1993, Ebinghaus 1996, Cuisson 1994) provides ample base to develop appropriate QA/QC guidance in a later phase (of the drafting process).
5 Data pre-treatment
There are several distinct phases from the filed to the laboratory in the obtention of measurements of environmental concentrations of HM and POPs and the later use of them to assess physico chemical parameters and effective exposures rate coefficient. The pretreatment and QA/QC will have to be designed in a way to ensure the best use of available information and resources. (i.e. Blackwood 1992, Brown 1978, Crump 1979) and to enable advanced statistical treatment and accurate estimates. (AMAP 1993, Burniston 1994) provide a complete description of the data flow provisions in existing large-scale networks.
6 Reporting
AMAP 1993, Burniston 1994 provide extensive examples.
7 List of variables + suggested units
Site
Date (in out)
Sampler/analytical method
Substance
Air concentration
Deposition
Wet
Bulk
Dry
Soil and surface water
Sediment
Vegetation lipid fraction
Animal tissue lipid fraction
8 References
AMAP, Arctic Monitoring and Assessment Programme, http://www.amap.no/
AMAP 1993. The Monitoring Programme for the Arctic Monitoring and Assessment Programme.
AMAP Report 93.3 AMAP, P.O Box 8100 , 0032 Oslo.
Barrie, L. A. and R. S. Schemenauer 1989. Wet deposition of Heavy Metals, pp 203-231 in Control and Fate of Atmospheric Trace Metals, Kluwer Academic, Dordrecht.
Bidleman, T. F. 1988. Atmospheric processes, Wet and dry deposition of organic compounds are controlled by their vapour / particle partitioning. Environ. Sci. Technol., 22 361-367.
Blackwood, L. G. 1992. The lognormal distribution, environmental data, and radiological monitoring. Environmental Monitoring and Assessment 21: 193-210.
Brorström-Lundén, E. 1996. Atmospheric Deposition of Persistent Organic Compounds to the Sea Surface. Journal of Sea Research 35,81-90.
Brown, C. 1978. Statistical aspects of extrapolation of dichotomous dose-response data. J.Natl. Cancer Inst, 60, 101-108.
Burniston, D. A. 1994. Integrated Atmospheric Deposition Network, Standard Operating Procedures Rev.2. Lakes Research Branch, NWRI, Burlington, Ontario.
Calamari, D. E. Bacci, S. Focardi, C. Gaggi, M. Morosini and M. Vighi 1991. Role of Plant Biomass in the Global Environmental Partitioning of Chlorinated Hydrocarbons. Environ. Sci Technol. 25, 1489-1495.
Crump, K. S. and D. Masterman, 1979. Review and evaluation of methods of determining risk for chronic low-level carcinogenic insult. In Environmental Contaminants in Food. Office of technology Assessment, U.S. Congress, Washington D.C.
Cuisson, S 1994. Integrated Atmospheric Deposition Network, Quality Assurance Program Plan. Environment Canada, US EPA, Ontario Ministry of Environment and Energy. IADN. Canada/US Great Lakes Water Quality Agreement.
De Leeuw,F.A.A.M. 1996. Proceedings of the EMEP workshop on European Monitoring Modelling and Assessment of Heavy Metals and Persitent Organic Pollutants. RIVM report 722401013.
Ebinghaus,R. et al 1996. International field intercomparison of measurements of atmospheric mercury species at Mace Head, Ireland. 5Th International Conference on Mercury as a Global pollutant, Hamburg August 5-8, 1996. GKSS Research Center,Geesthacht, Germany.
EMEP Manual http://www.nilu.no/projects/ccc/manual/
EMEP 1993. Long term plans, Annex 1:Measurement programme For Heavy Metals (Toxic Trace Elements) EMEP/CCC-note 2/93. NILU.
EMEP-MSCE Workshop on Assessment of EMEP Activites Concerning Heavy Metals and Persistent Organic Pollutants and their Further Development,Moscow 24-26 Sept. 1996., (proceedings in progress).
FAO 1993 Codex alimentarius vol 2: pesticide residues in food. second edition FAO, Rome pp 475.
FAO 1993 Codex alimentarius vol 13: methods of analysis and sampling. second edition FAO, Rome pp 134.
Farmer, W. T. and Wade, T. 1986. Relationship of Ambient Atmospheric Hydrocarbon (C12-C32) Concentrations to Deposition, Water Air and Soil Pollution, 29, 439-452.
Foreman, W. T. and Bidleman, T. F. 1990. Semivolatile Organic Compounds in the Ambient air of Denver, Colorado. Atmos. Environ 24 A, 2405-2416.
Hart, K., I. Loran and J. Pankow 1992. High-Volume Air Sampler for Particle and Gas Sampling Performance. Environ. Sci. Technol.. 26, 1048-1052.
Hoff, R. M., W. M. Strachan, C. W. Sweet, C. H. Chan, M. Shackleton, T. F. Bidleman, K. A Brice, D. A. Burniston, S. Cussion, D. F. Gatz, K. Harlin and W. H. Schroeder 1996. Atmospheric deposition of toxic chemicals to the Great Lakes: a review of data through 1994. Atmospheric Environment 30, 3505-3527.
IAND 1994. Standard Operation Procedures. AES SPM Rev2.
Iverfeld, A., E. Brorström-Lundén, J. Schaug and T. Berg 1996. Measurement program for Heavy Metals and Persistent Organic Pollutants in Air and Deposition in Europe. Background document for the workshop on Assessment of EMEP Activities Concerning Heavy Metals and Persistent Organic Pollutants and their Further Development, Moscow 24-26 Sept. 1996.
Iwata, H., S. Tanabe, N. Sakai and R. Tatsukawa 1993. Distribution of Persistent Organochlorines in the Oceanic Air and Surface Seawater and the Role of the Ocean on Their Global Transport and Fate. Environ. Sci. Technol. 27, 1080-1098.
Iwata, H., S. Tanabe, N. Sakai, A. Nishimura and R. Tatsukawa. 1994. Geographical distribution of persistent organochlorines in air, water and sediments from Asia and Oceania and their implications for global redistribution from lower latitudes. Environmental Pollution 85 15-33.
Jones, K. C., G. Sanders, S. R. Wild, V. Brunett, A. E. Johnston 1992 . Nature 356, 137-139.
Kawamura, K. and I. R. Kaplan 1986. Biogenic and Anthropogenic Organic Compounds in Rain and Snow Samples Collected in Southern California. Atmos. Environ. 20, 115-124.
Leister, D and J. Baker 1994. Atmospheric deposition of Organic Contaminants to the Chespeake Bay. Atmos. Environ. 28,1499-1520.
Maenhaut, W. 1989.Analytical Techniques for Atmospheric Trace Elements. pp 259-301 in Control and Fate of Atmospheric Trace Metals, Kluwer Academic Publishers. Dordrecht.
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Mazurek, M., B. R. T. Simoneit, L. Standley, D. Firedman and C. Beeman 1987. Design and Use of a Collector for In Situ Isolation of Particulate Trace Organic Species in Precipitation. Water Air and Soil Pollution 36,193-206.
McVeety, B. and R. Hites 1988. Atmospheric Deposition of Polycyclic Aromatic Hydrocarbons to Water Surfaces: a Mass Balance Approach. Atmos. Environ.22,511-536.
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Comments:
1Oslo and Paris Commission (OSPARCOM) that has assessed the situation for the Norht Sea and the Atlantic the Helsinki Commission (HELCOM) that has assessed the situation in the Baltic, the IGAC (International Global Air Chemistry) programme form IGBP and the Arctic Monitoring and Assessment Programme (AMAP) among others.
2 Based on Nat.Acad.Sci 1983, Risk assessment in the federal government:Managing the process. Nat.Acad.Press, Washington.
3 Oslo and Paris Commission (OSPARCOM) that has assessed the situation for the Norht Sea and the Atlantic the Helsinki Commission (HELCOM) that has assessed the situation in the Baltic, the IGAC (International Global Air Chemistry) programme form IGBP and the Arctic Monitoring and Assessment Programme (AMAP) among others.