Analyzing soil quality

1996/03/01 Bargos, Txomin Iturria: Elhuyar aldizkaria

• Ingurumena

Industrial activity, directly related to the development of our economy in the immediate past, showed no great concern for the environment. In some cases it can be said that he acted negligently. This situation leads us to find everywhere a lot of pollutants emitted to the environment and especially the soil. So things, today it is essential to develop expensive research projects.

The objectives of the projects are multiple and varied: study to what extent pollution can affect our environment, characterize pollutants, etc. And if we want to know what type of future use the soil will have, we must know in detail all the features that have been mentioned, which will entail recovery or definitive loss of the soil.

In order to carry out the study of soil quality, the points that the Basque Government, through its Ihobe Public Society, determines the project called “Master Plan for Soil Protection” are taken into account. Based on these considerations, the basic steps outlined below are taken when analyzing soil quality.

Identification of potentially contaminated sites

Carrying out research work known as Inventory of potentially contaminated soils makes the road easier. In fact, in order to know if the original chemical physical characteristics of the soil have changed and to what extent they have changed, this is an essential tool and, therefore, is the first step to detect contamination.

Collection of information

Although the types of pollutants that can be found in the soil are very varied, in practice they can be divided into seven large groups and so we do in Gaiker.

This second step is to collect all the information necessary to understand the current situation. The methodology to follow is the realization of a detailed study of the environment: documentation work, direct visits, historical study, etc. The collection of information is done before the chemical study of the soil or the sampling campaign is started. In fact, it allows to know in advance the economic viability of expensive research projects. Once we have carried out a historical study, we can know, for example, the potentiality of the soil and, in some cases, some of the programs that were considered necessary cannot be carried out with the consequent economic savings.

Local research

When data obtained in previous phases confirm that the analyzed soil is contaminated, local research is usually initiated. This is the most important time for soil quality analysis and the phase that more human and material resources require.

The starting point of the study should be very clear. Needless to say, we would start working among hundreds of parameters and/or study areas if we do not define in advance what we should investigate and how we will do it. As already mentioned, there are many resources at stake and their incorrect or correct use will largely depend on the transparency of the study.

Although the types of pollutants that can be found in the soil are very varied, in practice they can be divided into seven large groups and so we do in Gaiker: metals, inorganic compounds, volatile aromatic compounds, polycyclic aromatic hydrocarbons, chlorinated hydrocarbons, pesticides and others.

The correct classification and characterization of these seven groups of pollutants is based on the importance of material resources and the need to have a laboratory equipped with high-level equipment and, of course, on the performance of the functions of a team of qualified technicians.

As for soils contaminated by HGH residues generated in lindane production, the most commonly used technique is High Definition Gas Chromatography (HRGG). Although the components of this technique can be very numerous, two are basically very precise analytical methods for the quantification of halogenated compounds, the Electron Detection Detector (ECD) and the Selective Mass Detector (MS) that allows the correct identification of the contaminant.

Data analysis and assessment

When analyzing the results obtained in previous phases, the values established by the Master Plan of the Basque Government are used. Thus, the data obtained are divided into three levels.

A value or reference level: if results above this value are obtained, it is confirmed that the soil is contaminated.

Value B or lower limit of the level of risk acceptability: if the results obtained exceed that value, it can be said that it has associated an unacceptable level of risk.

Maximum risk level C or acceptable: When results exceed this limit, soil pollution is assumed to harm human health and ecosystem functioning. This involves the implementation of soil recovery projects.

Risk analysis

In this last phase the potential and real risks arising from the alteration of soil characteristics are analyzed. In fact, we try to predict the impact of the new situation on basic performances. Thus, due to the defined risks, in human health, in the functioning of different ecosystems, in the dispersion of pollutants or in the usual uses of soil (agricultural, forestry, building, etc.) possible dysfunctions are analyzed.