The quality of atmospheric air in the Białe Zagłębie is primarily determined by the type of economy carried out in its area. The rock raw material mining and processing industry and, additionally, communal and living sector and road transportation are the largest sources of emissions there. Moreover, air masses from the Upper Silesian Industrial District and even the Czech Moravia, periodically occurring in the Białe Zagłębie and identified on the basis of NOAA Hysplit backward trajectories, may be an additional environmental burden (Fig. 3). The largest share of dust emissions to the atmosphere belonged to the Trzuskawica Lime Industry Plant located in the central part of the Białe Zagłębie, which emitted annually 131.7 Mg of dust, on average and the Lafarge Cement Plant in Małogoszcz, which emitted annually 129.75 Mg, on average in the years 2002–2018 (Fig. 2). During the analysed period, only the cement plant in Bukowa decreased its volume of emissions. In total, 263.3 Mg of dust from the plants monitored by the Provincial Inspectorate of Environmental Protection got into the atmosphere in 2016, 302.2 Mg in 2017, and 293.0 Mg in 2018. According to the regulation of the Minister of Environment (Journal of Laws of 2018, item 799), the permissible level of dust with a fraction of 10 microns - PM10 in the air is 50 µg.m− 3(daily average), and the limit of permissible exceedances during the year amounts to 35 days. The permissible annual PM10 level amounts to 40 µg.m− 3.
The analysis of suspended PM10 concentrations from the Provincial Inspectorate of Environmental Protection’s station in the Białe Zagłębie, meteorological data and the NOAA Hysplit model showed that:
- the highest average annual PM10 concentrations were recorded in 2017, i.e. 85.3 µg.m− 3 for Nowiny and 35.8 µg.m− 3 for Małogoszcz,
- the biggest number of days with exceedances of the permissible level was recorded in 2017 in Nowiny, i.e. 198 days, in total,
- the values above the permissible level and the highest values were recorded for the cool half-year periods,
- the maximum value of PM10 concentrations at both stations (274.6 µg.m− 3 in Nowiny and 175.7 µg.m− 3 in Małogoszcz) fell on 8th and 9th January 2017, with such minimum temperatures on those days as: -25.2 oC and − 26.3 oC, respectively,
- the maximum values of concentrations were recorded during the period of air inflow from the south-west direction, along with the lowest air temperature during the year.
Chemical analysis of dust samples from the Dyckerhoff Nowiny and Lafarge Małogoszcz cement plants showed a significant share of heavy metals in their composition (Table 1). The largest share was reported for iron and aluminium, lead and zinc (Table 1). The pH of both samples was alkaline, its value in H2O and KCl was pHH2O = 13.21 and pHKCl = 13.02 for the sample from Małogoszcz and pHH2O = 12.61 and pHKCl = 12.38 for the sample from Nowiny.
Analysis of PM10 showed variable values throughout the year. Dust concentrations in the air correlate with the increase in cement and lime production (Fig. 4a). Increased values in winter periods could be related to the release of pollutants from domestic heating installations and the inflow of air from local and remote sources of industrial emissions , (Fig. 4b).
The hourly values of sulphur dioxide and nitrogen dioxide concentrations in the whole analysed period did not exceed the permissible values at both Provincial Inspectorate of Environmental Protection’s measuring stations. In the case of sulphur dioxide and PM10, there was an increase in pollution during the cold half-year and a decrease during the warm half-year with lower concentration values.
The relationship between SO2 and PM10 concentrations and air temperature was noticeable (Fig. 5).
Based on the conducted research, it was found that the weighted average pH value of precipitation in 2016 was 5.91 (normal precipitation according to the classification by Jansen et al. ) with fluctuations from 5.30 (January 2016) to 6.57 (May 2016). Electrolytic conductivity (EC) was 4.50 mS.m− 1 (significantly elevated). In 2017, the average pH value was 6.47 (slightly elevated) and conductivity − 7.12 mS.m− 1 (extremely elevated). The lowest pH for precipitation was recorded in December 2017. In 2018, the slightly elevated pH (6.15) and extremely elevated electrolytic conductivity (9.95 mS.m− 1) were found. The lowest pH values were recorded in the winter months (January - pH 5.77, December - pH 5.39).
The analysis of heavy metal content showed the highest concentrations of iron, copper, aluminium and nickel in precipitation. Concentrations of other heavy metals did not exceed 100 µg.dm− 3 in average monthly precipitation samples. The highest concentrations of iron in the monthly sample was found in January 2016 (580 µg.dm− 3). The highest concentrations for copper (180 µg.dm− 3) and aluminium (57.5 µg.dm− 3) were found, in turn, in September 2018. To compare to the entire study period, two months (January and September 2018) were distinguished due to elevated concentrations of all tested heavy metals. Such a situation could have been affected by the weather conditions. Low temperatures in January and February 2016 and the extremely dry summer of 2018 were favouring high concentrations of heavy metals in the air and their deposition, and after precipitation - due to leaching - were increasing their values in the analysed water samples. Statistically significant relationships (p < 0.05) were found among the individual elements being analysed, marked with an asterisk in Table 2.
High coefficients were accompanying Pb, Fe, Co and Al with all analysed heavy metals. The relationships of chromium with nickel and cadmium with copper were marked. The increased mineralisation (EC) could be associated with the presence of cadmium, copper, iron and aluminium.
Transplantation of lichens in the south-western part of the Świętokrzyskie Mountains indicated the accumulation of trace elements of anthropogenic origins. The amount of accumulated metals was calculated for each control point based on the difference between the concentrations of metals in the biota of lichens transplanted into the Białe Zagłębie and the concentrations of metals in the blank sample tested immediately after taking it from the Borecka Primeval Forest. The average content of accumulated heavy metals was the highest for aluminium (about 900 mg.kg− 1 d.m.) and iron over 400 mg.kg− 1 d.m.; and, both elements reached the highest concentrations during the third series of transplantation. The lowest concentrations of aluminium in the lichen thallus were recorded during the fourth series of transplantation (325.6 mg.kg− 1 d.m.), while for iron - during the first series (222.6 mg.kg− 1 d.m.). The highest concentrations of these metals were observed in Bolechowice (11), Bukowa (13) and Lipowica (21), located in the immediate vicinity of the cement plant . The increased content of iron and aluminium in the air, apart from the emission from cement plants, was also associated with the weathering process of rocks and minerals . The next largest element in the six-month series was zinc. Its values were the highest during the second series of transplantation, with an average of 41.7 mg.kg− 1 d.m. The highest concentrations were recorded in thalli exposed in Bolechowice (11) and Lipowica (21), and the lowest ones were found in Chorężów (7) (in three series below 5 mg.kg− 1 d.m.). Copper and lead concentrations in lichen were similar to each other in all analysed periods. Visible differences occurred during the fourth series in which an average of 12.7 mg.kg− 1 d.m. was recorded for lead and 19.56 mg.kg− 1 d.m. - for copper (Fig. 6). The highest concentrations of lead (up to 64 mg.kg− 1 d.m.) were recorded for the lichen samples from Bolechowice (11) and Lipowica (21), while the highest ones of copper (up to 56 mg.kg− 1 d.m.) were found in the samples collected from Jaworznia (1), Wymysłów (22), Brzeziny (17), and Milechowy (6).
Chromium, cobalt, cadmium and nickel concentrations in all exposure series did not exceed 1 mg.kg− 1 d.m. During the first year of research, there was a noticeable increase in the accumulation of the analysed elements for the cold half-year in comparison with their accumulation in the warm half-year. It was the largest for zinc - by 50%, lead and copper by 23%, aluminium by 17%, and iron and nickel by 10%. Only concentrations of cobalt, chromium and cadmium slightly decreased. During the second year of lichen transplantation, the concentrations of accumulated elements were higher in the samples exposed in the cold half-year in comparison with the elements accumulated in the warm half-year for: copper (by 83%), cadmium (by 64%), lead (by 57%), cobalt (by 54%), and chromium (by 51%). A decrease in concentrations was noted for other heavy metals. It was the highest for aluminium (by 174%), zinc (by 97%), iron (by 50%), and nickel (by 9%).
Needle pH determinations showed the average values of pHH2O 5.62 and pHKCl 5.28. The highest values of pHH2O 6.38 and pHKCl 5.81 were recorded in the central part of the study area, i.e. in Polichno (15).
Average content of the analysed metals in the samples of needles was the highest in the case of aluminium (over 400 mg.kg− 1 d.m.), iron (270 mg.kg− 1 d.m.) and zinc (65 mg.kg− 1 d.m.). The content of lead, copper, nickel and strontium did not exceed 10 mg.kg− 1 d.m. The content of iron and aluminium found in the air, apart from the emission from cement plants, was also associated with the weathering process of rocks and minerals . In 2018, pine needle samples for physico-chemical and chemical tests were collected again. The analysis of results showed a significant increase in heavy metal concentrations, especially for chromium (3.3-fold), aluminium (3-fold), manganese (2-fold), and nickel (1.4-fold), compared to the samples from 2016. Other heavy metals (lead, copper, cobalt, zinc, strontium, and iron) had a similar level as that in the previous study period. Considering the small changes in the volume of emissions, the fact of increased concentrations should be associated with favourable conditions for deposition of dust on pine needles (high air temperature, low annual precipitation). Depending on the location, and above all, the distance from the emitter, the volume of accumulated elements by the pine needles varied considerably; while the highest concentrations of lead, zinc, chrome, iron, aluminium and copper were recorded in the control sites located within 5 km from the industrial plants and nearby quarries (Fig. 7).
There was a spatial pattern of concentrations of selected trace elements (Pb, Cu, Ni) observed in a latitudinal system, i.e. higher in the area of lime and cement plants within 2 km from the emission source, and lower east of them, located in the vicinity of forest complexes within more than 2 km from rock processing plants. A source of heavy metals in the vicinity of lime plants in Bukowa may be the co-combustion of car tires in a process of lime production. Particles deposited inside the inter-cellular structure of needle may penetrate it and thus cause its capping which disturbs a gas exchange [43, 44, 45]. SEM/EDS analysis of the chemical composition confirmed the presence of metals (Pb, Fe and Al) as well as Ca, K and Mg (Fig. 8). The most important elements included in the cement-lime dust comprise of Pb, Fe, Al, and Ca. It may therefore be concluded that the direct source of emissions of elements found on the surface of the needles were the cement and lime plants operating in the study area.
Using the PCA (principal component analysis) method, three main components were distinguished, i.e. PC1 – PC3 (Table 3). In total, they generated 64% of cumulative total variance of trace elements in the samples from the analysed area of the Białe Zagłębie, regardless of bio-indicator’s location. They take into account the conditions associated with the cement and lime industry operating in this area (PC1-PC3) and transportation resulting from the course of the S7 express way at a distance of about 1 km from the study area (PC3).
The first component (PC1) generated 34% of total variance and showed high weight (≤ -0.87) for Fe and Pb (Table 3). The second component (PC2), in turn, formed 17% of total variance with the highest weight for Zn and Cr. Also important is the PC3 analysis (13% of variance) which indicated high weight for Cu (Fig. 9).