Assessment of heavy metals contamination in soils in the Beskidy mountain forests and their potential impact on soil enzyme activities and microbial community

The research was carried out in the Beskid Śląski and Beskid Żywiecki mountains which were affected, among others, by air pollution from the Upper Silesian Industrial Region, the largest industrial zone in Poland. The aim of the study was to assess the heavy metal load in the soils of the studied area and to determine their potential impact on soil metabolism. The research was carried out on 6 permanent sites. For each site, the total content of zinc (Zn), lead (Pb) and cadmium (Cd) was determined for three soil levels (A, B and C). Moreover, the following were determined: total nitrogen, organic carbon, pH and soil moisture and the amount of heavy metals in soil solutions. The metabolic activity of the soil was assessed by measuring: soil enzymes activity, soil respiration and by studying community-level physiological profiling (CLPP) using Biolog ECO-plates. In the case of Pb and Cd their increased content in the topsoil was found, which indicates their anthropogenic origin. Statistical analysis showed that in the case of very acidic forest soil even slightly elevated lead level probably can affect the functional biodiversity of soil microorganisms. The study showed that it is not easy to assess the impact of heavy metals on soil metabolism. Some indicators such as the activity of soil enzymes used individually may not be sufficient to illustrate the changes occurring in the soil environment.

Monitoring Soil Enzymes Activity before and after Animal Manure Application

Soil enzymes (urease, invertase, acid and alkaline phosphatase) activity in the rhizosphere of field-grown tomato plants were used to monitor the impact of soil amendments (SA) and SA mixed with biochar on soil microbial activity four months after addition of amendments. The soil treatments were sewage sludge (SS); horse manure (HM); chicken manure (CM); vermicompost (worm castings); commercial inorganic fertilizer; commercial organic fertilizer; and no-mulch (NM) native soil used for comparison purposes. Soil treatments also were mixed with 10% (w/w) biochar to investigate the impact of biochar on soil enzymes activity. The results showed a significant increase in soil urease and invertase activities after incorporation of SA to native soil. Vermicompost and HM were superior in increasing urease and invertase activity four months after their addition to native soil. Alkaline phosphatase activity fluctuated among the soil treatments, revealing some obstruction of its activity. SS amended with biochar increased acid phosphatase activity by 115% four months after SS addition. Other than alkaline phosphatase, organic manure enhanced soil biological activity (microbial biomass and release of enzymes), indicating that the use of manures, rather than inorganic fertilizers, in crop production is an affordable and sustainable agricultural production system.