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Determining follow-up measures

Step 9

The previous steps predict the extent of contamination and the risks associated with it. Before taking actions that are often expensive it is wise to check whether the predictions made using this manual, based on generic rules and models, are true for the specific site and conditions.

Two questions must be asked:

Step 9 describes what needs to be done to answer these two questions and what needs to be done if the results are different from those predicted.


Take samples from the soil and groundwater and have them analysed in a chemical laboratory. It is important, however, that the samples are taken in the right manner and in the right places, otherwise the results will be unreliable and therefore useless for checking purposes.

Where to sample

The places where sampling will be most useful are those places where humans are most exposed to the soil or water. These include wells used for drinking-water (by humans or cattle), fields used for agriculture (in particular the growing of vegetables) and the topsoil near houses or schools. Of course, a sampling spot should be within the parameters of contamination predicted by the manual. In selecting these spots, it is essential to take into account the prevailing wind direction and the direction of groundwater flow. Take the samples downwind or downstream (the groundwater flow direction will normally be known by the given country's Ministry of Agriculture, Land Use Planning or Water Supply department). Sample those spots that are nearest to where the obsolete pesticides have been stored.

Sampling is not useful when contamination by other activities may have occurred. Examples of unsuitable spots are roads, areas where other waste has been stored, areas near factories and spots where wastewater is discharged.

How to sample water

The sampling of groundwater is not difficult. Fill a clean bottle, preferably of glass, with water. As a rule, sample one litre.

How to sample soil

Aim. To obtain soil samples by employing a uniform, high-quality method.

Principle. Soil excavated during boring should be sampled in such a manner that the sample obtained is sufficiently representative of the soil layer concerned and that the contaminant concentrations have not suffered evaporation or contamination caused by the packaging or the sampling equipment.

Three main types of soil samples should be distinguished:

  1. Undisturbed soil samples. Split-spoon samplers, thin-wall tube samplers and core barrels can be used to obtain undisturbed soil samples. The sampling tubes are pressed, hammered or rotated into the soil and can be shipped to the laboratory or subsampled in the field. Undisturbed sampling is recommended for the analysis of volatile compounds.

  2. Semi-undisturbed soil samples. Undisturbed drill cuttings can be obtained by using gouges or piston samplers. The exposed surface of the cuttings can be removed with a spatula and the inner cuttings can be placed immediately in a sampling jar.

  3. Disturbed samples. The soil samples obtained by using edelman augers and solid-stem augers will be moderately disturbed during the drilling activities but in most cases can be used for chemical analysis purposes. The exposed surface of the cuttings can be removed with a spatula and the inner cuttings can be collected in a sampling jar. It should be noted that high-quality samples of the shallow soil could be obtained by excavating profile pits, using a spatula to take samples directly from the pit walls.


Survey of sample quantities and data on the filtration and preservation of groundwater samples in the field

Analysis BottleTo be topped upFiltrPreservation
Volume (litre)ColourAgentAmountHolding time
Aromatic solvents, chlorinated solvents, volatile chlorobenzenes0.25GreenYes HNO3 pH<20.2 ml7 days
Chlorophenols, phenols (GC)0.5GreenYes   24 h
Chromium VI0.5GreenYes   24 h
Cyanide0.25GreenYesYesNaOH pH=120.25 ml24 h
BOX1GreenYes   48 h
Phenols (volatile)0.25GreenYes H3PO4 pH<4 CuSO43 drops 0.25 g24 h
GC-MS volatile1GreenYes   24 h
GC-MS semivolatiles1GreenYes   24 h
Mercury0.25WhiteNoYesHNO3 pH<1 K3Cr2O72 ml 0.05 g1 month
Heavy metals0.25WhiteNoYesHNO3pH<20.2 ml1 month
Non-volatile chlorobenzenes1GreenYes HNO3pH<20.75 ml7 days
Nitrophenols1GreenYes   24 h
Oil (GC)0.5GreenYes HNO3 or HCI pH<2 7 days
Organophosphorus pesticides, organonitrogen pesticides1GreenYes   24 h
PAH (polycyclic aromatic hydrocarbons)1GreenYes HNO3 pH<20.75 ml24 h
PCBs, organochlorine pesticides1GreenYes   7 days
Vinyl chloride*0.02WhiteNo   ASAP (24 h)
Volatile hydrocarbons (C4-G4)0.5GreenYes HNO3 pH<20.4 ml7 days
VOX0.25GreenYes HNO3 pH<20.2 ml7 days
Water-soluble solvents and acrylates (headspace)0.25GreenYes   24 h

* Prescription used by Tauw Laboratory: inject 15 ml of sample into a 20-ml headspace phial; deliver three phials for each well.

Equipment required:

General procedures:

When volatile components are to be analysed:

When non-volatile components are to be analysed:

Note that direct sampling from the boring system generally reduces the representativeness of the sample in comparison with sampling from a foil. In the case of volatile contaminants, however, this effect is negligible compared with the effects of volatilization.

Instructions for filling a jar:

Coding of soil samples. The jars containing the soil samples should be marked with the following data: site name, bore hole number, section depth and date of sampling.

Storage and shipment of soil samples. For the duration of the fieldwork, sampling jars and sampling tubes filled with soil must be stored at a location that is as cool as possible (approximately 2–4°C) and protected from sunlight. The soil samples must be transported to the laboratory as soon as possible after the fieldwork is completed.

Note that cuttings and samples not kept for analysis should be stored and disposed of in agreement with the responsible site manager.

Holding time. The holding time of soil samples is limited due to volatilization and biodegradation. A sample should be extracted in the laboratory within the holding time. The holding times are summarized in Table 9.2.

Reporting. Enter in the bore log the codes marked on the sampling jars and the depths at which the samples were taken. At the completion of the fieldwork, enter in the boring order form the total number of soil samples taken.

How to analyse the samples

All samples need to be analysed for the presence of the pesticides that were predicted in the manual, as well as for the presence of harmful pesticides other than those predicted. Since there are many hundreds of different pesticides, however, checking all of them would be far too expensive. A good solution is to request that the laboratory screen the samples for the five to ten pesticides that show the highest concentrations. Most laboratories are able to carry out this screening with the help of gas chromotography-mass spectrometry (GC-MS) or atomic absorption (AAS) equipment.


Concentrations are lower than predicted

The manual predicts the contamination and risks caused by improper pesticide storage based on a worst-case scenario. This means that the manual predicts a contaminated area as wide as realistically possible and assumes that the pesticide concentrations are as high in this entire area as the highest concentration predicted.

In reality, concentrations will be smaller based on prevailing wind or water distribution patterns. Therefore, during checking, concentrations lower than those predicted will often be found. In this case, ignore the results of the check and proceed as if the predicted values had been found. Or, sample and analyse again to confirm the first analysis. If the results of the second sample are also lower than the predicted values, use the average results of the samples rather than the values predicted with this manual.


Holding time for soil samples

ParametersHolding time
Solvents24 h
Phenols24 h
Chlorinated pesticides and PCB7 days
TPH24 h
PAH7 days
Chromium VI48 h
Mercury (total)15 days

Concentrations are higher than predicted

If the concentrations found through sampling and analysis are higher than those predicted with the manual, it is important to repeat the sampling and analysis, since the results of one sample are considered to be reliable only if confirmed by a second sample. If the second sample also shows higher-than-predicted values, take the average of the two sample results, rather than the values predicted with the manual. If the second sample is lower than the predicted one, either take the predicted value, or sample for a third time.

Step 10
Measures for addressing contamination


When deteriorated packaging of obsolete pesticides has caused contamination to occur, measures (sometimes simple, sometimes elaborate and expensive) must be taken to prevent further damage.

First, the cause of the problem (improperly stored pesticides) needs to be addressed. The pesticides, their deteriorated packaging and the severely contaminated soil must be packed in proper containers.

To prevent a recurrence of the problem, the pesticides need to be removed and treated properly, which generally means incinerated in a dedicated waste incinerator. Some types of pesticides may be incinerated also in cement kilns, provided that those kilns are managed properly. This solution, however, is still the subject of debate.


Measures may also be necessary to treat the area that has been contaminated by the pesticides. There are three basic types of measures:

Removing the contamination also means that the material removed needs to be put somewhere else. Contaminated soil is usually disposed of in a controlled landfill, whereas contaminated groundwater is treated (contamination is removed) and then discharged. Landfilling should be avoided as much as possible. Note that in-situ measures (e.g. treating the contamination at the spot without removing it) are generally not possible with obsolete pesticides because of their characteristics (low degradation, low volatility, low leachability). More modern pesticides generally degrade much more easily.

For soil contaminated with organochlorine pesticides such as HCH, on-site biological treatment may be a cost-effective alternative. The treatment includes an initial phase in which the soil is covered with a layer of water to which nutrients are added. This stimulates anaerobic biological degradation. Subsequently, the soil is laid to dry and is ploughed or turned over, in order to stimulate aerobic biological activity. The treatment may take a few years but is relatively cheap.

Generally speaking, removing contamination is more expensive than containing it, which in turn is more expensive than taking protective measures. On the other hand, removing it is a more final solution (all contamination is gone), whereas containment measures must be maintained forever. Protective measures are effective only for as long as they are maintained, which may be difficult to ensure over a longer period.


The choice of measures depends on the seriousness of the contamination (whether contamination poses risks and whether those risks are high; the higher the risks, the longer-lasting the solution must be). It also depends on the vulnerability of the surroundings: a higher level of contamination may be more acceptable in industrial areas than in agricultural or residential areas. It also depends on the budgets available for direct investments and recurring costs. Also important is whether measures are needed for the immediate protection of human beings only or to prevent contamination from spreading and causing damage in the future.

When choosing which measures to take, the following guidelines apply:

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