Soil is currently producing much of the food we eat. Inside its profile we find a compound made out of organic matter, minerals and living organisms. The role of soil is essential to our well being and even though we also require certain amounts of heavy metals such as iron, cobalt, copper or zinc, excessive amounts of many metals could cause soil degradation, reduction of crop yield or reduction of the quality of agricultural products. Heavy metals are classified as non-biodegradable and therefore they can persist in the soil for a long period of time and cause it‘s contamination.
By soil contamination we mean a potential, irreversible or not, threat to the environment. Soil contamination is a serious issue particularly if we observe a rise of a contaminant above a certain level. After this, the soil stops acting like a protector and could cause adverse effects to the human health, water systems, atmosphere or other organisms.
In order to assess the potential harm of the soil pollution, we need to be able to identify it. To this moment, we distinguish hundreds of pollutants within the European environment. We can outline some of them using classes. Related to their origin, the prominent classes consist of pharmaceuticals, pesticides, disinfection by-products, wood preservatives and industrial chemicals.(1)
Constant period of industrialization in Europe has contributed to prolonged extraction of natural resources from their initial deposits by the activity of mining and smelting. Europe’s exposure to industrialization has revealed a new threat and it is the contamination of the soil by non-biodegradable heavy metals. These substances are of particular concern, because a human activity can directly impact their dispersion.
To set a clear picture, we will look at the former mining area of Rudňany (Slovakia), where the soil pollution is demonstrable. In 2011 a research has been established to show the impact of long time mining and processing of mercury within the area. At times when the largest amounts of mercury were mined and processed in Rudňany, up to 4 tons of mercury were being released annually into the air.
The research was conducted in the village of Rudňany(2), where the area had been touched by soil and water pollution due to historical binding to mining and processing of mercury. In order to determine the consequences, a several soil samples were taken at 8 different locations within the village. For example soil samples were taken from places near the mercury processing plant, from area out of potential pollution sources and at the heap of waste material. Looking at the results, the level of mercury exceeded the limit value 141 times at the locality of mercury processing plant. The level of mercury at the least polluted locality within the measured area was 5.7 times more than the permissible limit value. The results also connect an increased concentration of heavy metals with reduced activity of enzymes within the soil.
The main reason why we need to understand the concept of soil contamination is because of its direct interaction with the human body. Soil contamination may be connected to health problems such as neurological damage, lowered cognitive abilities, skeletal and bone diseases and cancer.
Due to the lack of research available, no human data ties mercury exposure to cancer. Nonetheless, mercury is a neurotoxin(3). Neurotoxins are poisonous or destructive toxins that can cause damage to the nerve tissue. Where the impacts of exposure to mercury depend on number of factors such as the amount of mercury a person is exposed to and the period the exposure lasts for. For an instance, if a person is exposed to mercury throughout a vapour and for a long-time, the effects can vary from an innocent fatigue to more serious issues like anxiety, forgetfulness, and changes in vision or loss of appetite.
So the question is, ‘Can we recover a soil contaminated by mercury?‘ There is a possibility that mercury could be removed from soil by chemical separation, which can be only done in a small scale and at the laboratory(4). However, there is also another possibility. Trees can now be engineered to absorb a number of heavy metals from the environment. These trees were modified to include a gene, found in bacteria, which can convert toxic mercury ions into elemental mercury. The only problem is, these processes only exchanges one pollution for another. A plant can extract mercury from the soil and transfers it to the air in a form of less toxic elemental mercury(5).
There are many ways how we can face post-industrial wastelands. Current debates on whether the genetic modification of organisms is the right or wrong way, makes the decision quite sensitive. In my opinion, using innovation to alleviate what could not be effectively solved before is the appropriate way. The conclusion is clear; we are dealing with serious environmental issue that will have to be addressed very soon, unless we want to cause irreversible damage to our living environment.