One of the important areas of interest for the Geological Surveys of Estonia (EGT) is geochemical mapping in local urban areas. These studies aim to identify contamination hotspots, assess potential risks to human health, and provide information for land use planning and environmental management. This assignment holds great significance in understanding the complex chemical interactions between contaminants, water, soil, and air.

EGT has recently initiated geochemical mapping services, with thorough mapping of soil geochemistry completed only in the country's capital, Tallinn. However, the process is just beginning, and mapping in other urban areas will commence soon. The next city in line is Tartu, Estonia's second-largest city, which will be sampled and analysed geochemically over the next few years.

(Read about EGT's various environmental projects here).

Geochemical mapping is a challenging task that involves multiple phases, starting from the design of the study and determination of sampling strategies to the collection and processing of samples, laboratory analyses, and interpretation of data before the actual map creation.

The initial step of study design requires careful consideration of various variables. The specific focus of the study must be narrowed down, and the most suitable target area for investigation must be delineated. It is also crucial to determine the elements or contaminants of interest and the environmental compartments to be sampled—whether it's soil, sediments, water, or all of them.

Selecting the most representative sampling methodology across the target area can pose questions such as whether to follow a grid pattern, stratified sampling, or hotspot identification for obtaining reliable results. Accessibility to planned sampling sites, including geological factors and restrictions on private property, needs to be considered. Special permits may be required for access, and collecting multiple samples from each location might be necessary to capture variability. In the case of contamination sites, following specific sampling protocols becomes essential to prevent further contamination and ensure the safety of the samplers.

The challenges persist even after the collection of samples. Often, the samples need to undergo processing such as drying, sieving, homogenisation, and removal of organic matter or unwanted substances before the actual analysis can take place. Various common methods like X-ray fluorescence (XRF), chromatography for organic compounds, atomic absorption spectroscopy (AAS), and inductively coupled plasma mass spectrometry (ICP-MS) may be used to determine the chemical composition of the samples.

Despite the time-consuming and costly nature of the process, geochemical mapping is crucial for understanding the quality of our living environment. It helps identify direct or indirect hazards to human health, such as unseen toxins like radon in the soil that slowly infiltrate homes and cause serious health issues over time. It also helps address issues like excessive exposure to exhaust gases, polluted drinking water, and more. Geochemical mapping minimises the risk of such unfortunate occurrences.

In addition to global challenges like urbanisation, increasing traffic, deteriorating air quality, and waste issues related to consumerism, Estonia faces a specific environmental hazard linked to abandoned industrial and military sites from the Soviet Era. These sites, often located in no-man's-lands, can contain severe residual pollution that poses a high toxicity risk to surrounding nature and settlements. While many such remnants have been analysed and cleaned over the past decades, a significant amount of work remains. Estonia has over 260 potentially hazardous sites associated with residual pollution, both military and non-military, which is a substantial number considering its small area. The Geological Survey of Estonia will join the investigation of these sites, working with other environmental institutions to find remediation solutions. 

Geochemical mapping is one of the top priorities for EGT, enabling the detection of potential pollution sources and determining contaminant distribution in soil. Estonia can create a healthier living environment by making more environmentally conscious decisions regarding land use, infrastructure planning, and even consulting on safe urban agriculture initiatives and effective green spaces.