Nitrate contamination of shallow groundwater in the Carpathian Foothills (Southern Poland)

Skażenie azotanami płytkich wód podziemnych Pogórza Karpackiego

Summary: This study, based on a rural area in the Carpathian Foothills, aimed to assess the extent of contamination to a shallow aquifer by nitrates. The aquifer is composed of flysch and molasse sediments deposited during the Alpine orogeny, dominantly fine to medium grained sandstones. Nearly all the sediments are folded, faulted or deformed. This makes the hydrogeology very complicated since there is a lack of continuity and hydraulic connectivity, but the aquifer has been simplified to a single unit approximately 20 m thick. Fine-grained loess overlies the flysch and molasse deposits. This wind blown deposit which was later reworked sub-aqueously, varies in thickness between zero and 15 m. The hydraulic conductivity of the loess is low, so it acts as a confining layer. The range in nitrate content varied from to zero to almost 90 mg l-1. The WHO limit is 50 mg l-1. Nitrate can cause methemoglobinemia in babies and has been linked to stomach cancer. The highest nitrate concentrations were found in samples taken from wells situated in relatively high terrain. These areas have the lowest loess cover which protects the aquifer from contaminants. The nitrate concentration may also relate to the proximity to septic tanks. In most areas there are no sewage pipes and when a septic tank is placed up flow of a well there is high potential for contamination. Currently the farming practices in Southern Poland are non-intensive. However Poland is developing very rapidly and practices may change. The potential for contamination by pesticides and other agro-chemicals must be assessed. Through investigating the vulnerability of the aquifer to nitrate contamination, future problems can be predicted and possibly prevented. A vulnerability assessment on this area concluded that the aquifer has very little protection from contaminants where there is no loess cover. Where the aquifer is confined, the aquifer is not very vulnerable to contamination. Recommendations include that farming practices take account of the need to protect drinking water sources and that where septic tanks are the source of pollution, either the tank or the well is re-sited, or an alternative supply is found.

Słowa kluczowe (w języku angielskim): Carpathian Foothills, groundwater pollution, nitrates, wells

Prace Geograficzne, 1998, z. 103, s. 147-158.

Instytut Geografii i Gospodarki Przestrzennej UJ

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