Getting the baseline concentrations of harmful substances in control
Is there natural arsenic, antimony, or lead in the soil? Have the concentrations of harmful substances in the city’s surface soil increased over a long period of time as the result of industry, traffic, or heat production? These are some of the questions that GTK’s Geochemical baselines service answers. The map contains almost 90,000 sample points from all over Finland, and more detailed information from 10 cities.
“GTK produces data for this service that is used frequently by authorities, landowners and consulting companies,” says GTK’s senior researcher Timo Tarvainen.
“We have also received material from the city of Helsinki and the Natural Resources Institute of Finland. We have collected samples particularly from areas, where we have estimated on the basis of the geology that there may be larger concentrations in the soil,” Tarvainen says.
The Government Decree concerning the evaluation of soil contamination and the need to clean it sets threshold values for substances that may be harmful. If even the concentration of even one substance exceeds the threshold value in a location that is suspected to be contaminated, the landowner must have soil evaluated for contamination. The map service indicates, whether the baseline concentration exceeds the threshold. In this case, the baseline concentration can be used as the evaluation threshold.
Pirkanmaa is known to have high concentrations of arsenic
According to Tarvainen, the research data about baseline concentrations is beneficial, for instance, in the Pirkanmaa region.
The soil in the Pirkanmaa region has a high natural concentration of arsenic. Its baseline concentration is 26 milligrams per kilogram, and the allowed threshold value is five milligrams per kilogram. Because we know this, there is no need to survey the soil or try to clean it. When it is known that there is arsenic in a certain location, it is not a problem but can be controlled.
The map service contains geochemical survey data produced by GTK from the beginning of the 1980s. Since 2000, GTK has focused on surveying population centres and their surroundings.
The service includes information about the baseline concentration levels of antimony, arsenic, mercury, cadmium, cobalt, copper, lead, nickel, zinc, vanadium, thallium, boron, barium, molybdenum, selenium, tin, and beryllium. From some areas, information is also available about the background concentrations of PAH and PCB compounds.
The Geochemical baselines map service is available at www.en.gtk.fi/informationservices/map_services