A survey of contaminated soils is carried out at sites where contamination has been discovered or a soil contamination has been suspected. The purpose of the survey is to find out the types of pollutants, the concentration of pollutants, the spatial extent of the pollution, the dangers inherent in it and the possibilities for treating and rehabilitating the site.
Soil pollution in Israel is mostly caused by industrial activity and the activity of the fuel economy. According to data from the Ministry of Environmental Protection, about 1,250 contaminated land sites have been found in Israel to date, and it is estimated that there are many other pollution sites. The main substances that cause pollution are fuels, metals, oils and chloro-organic compounds. In cases where the ability of the soil to adsorb and absorb large amounts of fuels from the environment is large, the contaminants are only discovered at a later stage when a large amount of fuels has already leaked to the soil.
Contaminated soil can endanger human health and the environment following exposure to the pollutants, which occurs through direct contact, inhalation of soil gases emitted from it, and sand and dust particles from the contaminated soil. In addition, the pollutants can reach water sources (especially groundwater).
The soil survey is carried out with the help of a series of drillings, which also includes the collection and sampling of soil gases. In the design of the survey, measurement methods are selected, samples are selected that will be transferred for analysis in the laboratory, the appropriate analyzes are selected to identify the pollutants, the drilling method and the method of sampling from the ground.
Stages of contaminated soil surveys
The soil survey consists of several main stages. A historical survey is first conducted, which aims to gather all the existing information about the potential pollution on the site and various parameters that characterize the site (such as infrastructure, leaks, etc.). At this stage, a comprehensive inspection is conducted in front of government ministries and authorities, a tour of the area itself, and a review of photographs and maps of the site. A hydrological survey of the groundwater condition and a geological section for characterizing the soil layers is conducted.
In the next step, in order to identify the points of contamination in the soil, soil gases are collected and the components are analyzed (in the case of volatile and semi-volatile fuel components).
Based on soil sampling and analysis of sample results by analytical methods in the laboratory, the extent of the contaminated area can be estimated and demarcated.
The soil survey itself is then carried out, which includes the series of In addition to the concentration of pollutants (fuels, oils and metals), other parameters are also examined, such as the level of acidity of the soil, the percentage of water permeability, electrical resistance and more. Accordingly, the expected costs of treatment and the duration of soil restoration are estimated.
Finally, a rehabilitation program is tailored to the site, and the selection of optimal technologies for treatment. In a situation where the pollution poses a risk to public health, it is recommended that an excavation, evacuation and burial of the land be carried out, or local treatment.
Awareness of land pollution is growing today, and regulatory and enforcement measures are being taken. The Ministry of the Environment requires the following steps: conducting a historical land survey and examining the current state of the land, determining land ownership (landowners are responsible for treating and preventing pollution), assessing the budgets required for treatment, and assessing changes in land economic value. In 2008, a bill was enacted banning soil contamination and charging for periodic inspections, requiring inspection of suspicious lands and treatment of those found contaminated.
Conducting a soil survey is necessary at sites where a toxin permit is issued, or when a serious contamination is discovered in the groundwater and / or in the soil. Also in the real estate business and the transfer of ownership of land, it is recommended to conduct a survey of the presence of pollutants before making the transaction.
Isotope conducts soil surveys and historical surveys with the help of soil pollution experts, and using analysis services in laboratories approved by the Ministry of Environmental Protection.
Isotope and its affiliates conduct soil gas surveys to detect VOC, MTBE, ETBE, DIPE, TAME TBA and ethanol for the purpose of characterizing and identifying soil gas contaminants.
Ground gas is a gas located between the soil grains in the unsaturated medium. This gas may contain oxygen, nitrogen, carbon dioxide and water vapor, in addition to various pollutants capable of moving to the surface and even to structures in the processes of diffusion and convection. The main pollutants are radon and methane. There are also many contaminants in toxic organic matter that evaporate from soil or groundwater contaminants.
There are two main methods for sampling soil gas – active sampling and passive sampling.
If there is a suspicion of contamination at a particular site, it is necessary to carry out a preliminary survey (SCREENING) in order to locate the centers of contamination with volatile contaminants. This preliminary survey is an active soil gas survey. The survey will be conducted at any center where there is a concern about gas inventions. In each center where a gas survey was conducted, soil drilling will be carried out as part of the soil survey
Another major goal is to examine the possibility of ground gas intrusion into buildings and the potential risk inherent in public health.
The quantitative findings of the survey are compared to threshold values corresponding to the ground gas.drillings and the determination of the pollution concentrations.
As a pollutant vapor in the soil
When examining the pollutant vapor in the soil, the following two factors must be taken into account:
Hydraulic permeability or permeability – the ability of the soil to conduct fluids. The smaller the particles, the lower the conductivity.
Moisture content – the percentage of the volume of voids in the soil filled with water. The presence of liquids in the soil limits the movement of pollutant vapors. Therefore ground gas sampling after a rain event does not represent.
Risk survey through a land gas survey
When ground gas pollution is suspected, a risk survey should be conducted using a ground gas survey, which is carried out in one of two ways:
Passive sampling – sample collection using a material capable of absorbing such as cellulose fibers. This method is not recommended for risk surveys as it does not allow the volume of soil gas collected in a unit of time to be measured. The gases can also be collected using an insulated flux chamber that surrounds a confined and known area. Clean air flows into the cell and draws the gas vapor being tested. The samples are used to determine the pollutant flux in the field.
Active sampling – a sample extracted with the help of a probe deep in the ground.