2.2. Sampling Site

The samples were collected between 1 January 2011 and 26 December 2012 in Racibórz, a town located in the south-western part of the Śląskie (Silesian) Province in south Poland, close to the Czech-Polish border. The sampling point (50°5′ N and 18°14′ E) was located approximate 6 km south of the center of Racibórz. The Racibórz area is an agricultural region (Figure 1), where farmlands cover approximate 66.30% of the area. The entire industry (a few chemical, power, agricultural, and food-processing plants) as well as commercial centers are located in the town center. The population density is approximate 220 people/km² in the whole area, and about 700 people/km² in Racibórz itself. It is 3–5 times less than in other cities and towns in southern Poland. The majority of the inhabitants live in Racibórz. Low buildings with individual heating systems (fed with biomass, coal, or natural gas) dominate the landscape. The building development is compact in the center of Racibórz and scattered in the vicinity of the sampling site. The mean annual temperature in the region is +8.0 °C. January is the coldest month (−2.1 °C), whereas July is the warmest one (+18.0 °C). During the year, there are 100–110 frost days and 170 days with precipitation (including 45 snowy days) in the region. South winds prevail in autumn and winter and north winds are common in spring and summer. Calms are frequent.

Sampling point location.