4.6. Organic micropollution, radioactivity and microb

4.6. Organic micropollution, radioactivity and microbiology.

Organic micropollutants.

Organic micropollutants are a large group of potentially toxic or carcinogenic chemical subtances. Many are very persistent and/or degrade into secondary harmful compounds such as the DDT-derivatives DDD and DDE. These compounds tend to accumulate in the environment and biota, and it is therefore essential to assess the level of organic micropollutants, not only in the water but also in the sediment and in living organisms. Assessment of bio-accumulation is typically conducted on species exploited for consumption such as fish or mussels. In a few programmes analyses on suspended matter are undertaken (eg. NL-R1/M1, R-R1), and these are not distinguished from ordinary water samples.

Due to differences in land usage and agricultural practice, industrial type and wastewater treatment practice now and in the past, there are substantial differences in the organic micropollutant variables measured.

There are also differences in the level of details, some countries measuring a wide range of specific compounds, others relying on a few general analyses. For example, in some programmes PCBs are measured in total, in others as the concentration of a number of individual congeners (eg. PCB-28, PCB-58, etc.).

Table 4.6.1. Number of monitoring programmes measuring the most commonly occurring determinands

Variables measured.

A total of 123 variables are represented in the national monitoring programmes, but only 18 are represented in more than three programmes (Table 4.6.1). The most frequently measured compounds belong to the groups Organic solvents, Polycyclic Aromatic Hydrocarbons (PAHs), PCBs, Organo-Chloro pesticides (including DDT and its derivatives), other Halogenated compounds and Detergents.

Monitoring programmes.

Several monitoring programmes deal specifically with bioaccumulating compounds, ie. heavy metals and organic micropollutants (eg. FI-L3 and NO-M2/M3). Other programmes pay special, though not exclusive, attention to these substances, and many programmes include just a few variables, typically summary variables or significant pesticides. A few countries (Denmark and Sweden) do not include these substances in their national monitoring programmes.

Table 4.6.2. Number of determinands of various groups of compounds measured in marine and inland surface water monitoring programmes

The strategy of the countries with respect to compartments assessed and number of determinands in marine and inland surface waters is illustrated in Table 4.6.3. Amongst inland surface water programmes there is only one lake monitoring programme assessing organic micropollution (FI-L3, measuring 10 determinands), the remaining 15 being river programmes.

Germany, Spain, France and Greece analyze for relatively few substances, whereas, for instance, Norway, the UK and The Netherlands put a wide range of variables into use. The different compartments are weighed differently among the countries, Norway, for instance, concentrating on aspects of bioaccumulation reflected by detailed measurements of sediment and biota, whereas Austria mainly carries out water analyses.

Table 4.6.3. Number of determinands measured in water, sediment and biota in marine and inland surface water monitoring programmes.

Where to assess what?

There is considerable difference in the persistence of various compounds. More persistent compounds tend to accumulate in food chains. Consequently, the concentration of these compounds can be much higher in living organisms and sediment than in water. Less persistent or volatile compounds, on the contrary, tend to decompose or escape before they are assimilated by organisms, and the highest concentrations are consequently measured in water. The persistence of compounds also affects the impact of pollution in different waterbodies. Thus easily degradable compounds show the highest concentrations in close vicinity to the discharge source, whereas more persistent compounds are at least as important far from the source. These differences are reflected in the variables measured in different compartments in different kinds of waterbodies as indicated by table 4.6.4. that shows the number of monitoring programmes assessing the pollution level of various groups of substances in three compartments of marine and freshwater areas.

Table 4.6.4. Number of monitoring programmes measuring at least one determinand within various groups of compounds

Pollution by organic solvents, which are generally volatile but harmful before they escape, is almost exclusively assessed in the water phase and primarily in rivers, ie. close to the outlets from industry or wastewater treatment plants. The more persistent Polycyclic Aromatic Hydrocarbons (PAH) are primarily measured in river water or in the sediment and biota of marine areas, but also to some extent in sea water. This pattern reflects assessment of the current pollution discharge as measured in water, as well as the long-term accumulation in the final stratum, the sediment and biota of the sea.

Radioactivity determinands

Radioactive pollution is a widespread problem in marine areas and many river systems. Even though radioactive isotopes are used for a number of purposes, nuclear power plants and fuel reprocessing facilities are by far the most important contributors to radioactive pollution. Assessment of radioactive contaminants is a standard routine in marine areas and certain river systems with monitoring more intensive in areas of greater risk, eg. a major part of the IE-M3 Irish marine monitoring programme is devoted to an assessment of the discharges from Sellafield.

Radioactive pollution is assessed by measurements of the concentrations of individual radionuclides such as tritium, caesium-137 and plutonium. Total alpha and beta/gamma activity measurements may also be made (Table 4.6.5).

Accumulation in sediment and biota is an important aspect of radioactive pollution, especially where fish or mussels are exploited for human consumption. Public health care requires assessment of exploited species. This is included in the marine monitoring programmes of Norway and Ireland, whereas the river monitoring programmes of Austria, the Netherlands and the Rhine only analyze for radioactivity in the water, ie. as solute or in suspended matter. We are aware that other countries carry out extensive studies on radioactive pollution, but we have no detailed information on these programmes.

Table 4.6.5. Sampling frequency of radioactivity variables.

Sampling frequency

Usually sampling frequency of radioactivity variables corresponds to sampling frequency of other variables in a monitoring programme. In the Austrian river monitoring programmes, harmful substances including radioactive variables are sampled less frequent than the general variables.

Microbiological determinands.

The most commonly employed microbiological variables are measurement of faecal bacteria. These are not necessarily infectious to humans, but are good indicators of discharge of poorly treated urban wastewater. Thus, microbiological variables are highly related to assessment of the quality of water used for drinking, bathing or mussel production.

As soon as faecal bacteria are emitted to natural waters they rapidly become insignificant. These variables are therefore measured relatively closely to known or suspected outlets, ie. in river systems passing through inhabited areas or coastal areas. Furthermore, sampling is carried out in the water compartment, as the bacterial density in sediment rapidly declines. Most monitoring programmes in which analyses of microbiological variables are conducted are thus inland surface water programmes. The French and Irish programmes for marine environment primarily monitor coastal areas with special reference to classification of bathing waters or shellfish production areas.

The most frequently occurring variables are faecal coliforms, total coliforms, Salmonella and faecal Streptococci. Austria carries out plate counts in connection with several monitoring programmes, and a few additional variables are included in one programme.

Table 4.6.6. Sampling frequency of microbiological variables.

Sampling frequency

In most monitoring programmes sampling frequency of microbiological variables equals sampling frequency of physical/chemical variables. In programmes with special reference to microbiological pollution, however, sampling frequency varies depending on the actual situation, eventually sampling under certain conditions. This is the case in the Irish IE-M4 recreational area programme and the French FR-M2 microbiological programme.