Activity and Diversity of Microorganisms in Root Zone of Plant Species Spontaneously Inhabiting Smelter Waste Piles

Abstract

The aim was to assess plant driven changes in the activity and diversity of microorganisms in the top layer of the zinc and lead smelter waste piles. The study sites comprised two types (flotation waste—FW and slag waste—SW) of smelter waste deposits in Piekary Slaskie, Poland. Cadmium, zinc, lead, and arsenic contents in these technosols were extremely high. The root zone of 8 spontaneous plant species (FW—Thymus serpyllum, Silene vulgaris, Solidago virgaurea, Echium vulgare, and Rumex acetosa; and SW—Verbascum thapsus; Solidago gigantea, Eupatorium cannabinum) and barren areas of each waste deposit were sampled. We observed a significant difference in microbial characteristics attributed to different plant species. The enzymatic activity was mostly driven by plant-microbial interactions and it was significantly greater in soil affected by plants than in bulk soil. Furthermore, as it was revealed by BIOLOG Ecoplate analysis, microorganisms inhabiting barren areas of the waste piles rely on significantly different sources of carbon than those found in the zone affected by spontaneous plants. Among phyla, Actinobacteriota were the most abundant, contributing to at least 25% of the total abundance. Bacteria belonging to Blastococcus genera were the most abundant with the substantial contribution of Nocardioides and Pseudonocardia, especially in the root zone. The contribution of unclassified bacteria was high—up to 38% of the total abundance. This demonstrates the unique character of bacterial communities in the smelter waste.

Testing Combined Effect of Amendments and Inoculation with Bacteria for Improving Phytostabilisation of Smelter Waste Extremely Contaminated with Trace Elements

“…Plantavailable forms of N are very low and therefore they have to be provided in phytostabilisation systems with soil amendments or with fertilizers. Nitrates in Ctrl were slightly greater than their levels measured in a study with smelter waste collected from the same waste deposit [6]. Nitrates were almost fully acquired by plants in soils where compost was not added (L-0 combinations).…”

“…The latter was likely one of key mechanisms in case of L-0 and L-CFe soils, both variants were characterized by a deficiency of plant-available phosphorus. As documented by Siebielec et al [6], the interaction of plants and rhizosphere bacteria strongly improves the phytoavailability of nutrients for plants spontaneously inhabiting smelter wastelands. Therefore, improving the nutritional status of plants is definitely one of major mechanisms in supporting plant growth by bacteria in extremely metal-contaminated soils and wastes.…”

“…Even the soil without amendments but inhabited by plants had bacteria in much more abundance than the control without plants. Plantmicrobial interactions result in a higher population density of microorganisms, even under stressful conditions such as soil metal contamination [6]. These interactions lead to heavy metal tolerance, as well as the stimulation of normal plant growth and development [9,35].…”

“…Recent studies have shown that complex interactions between plants and their microbiomes lead to the transformation of smelter waste into soil-like material, much better suited to plant growth [6]. Therefore, the application of selected bacterial strains appears to be an additional component of phytostabilisation technology, worthy of wider analysis.…”

Phylloplane Biodiversity and Activity in the City at Different Distances from the Traffic Pollution Source

“…Exposure to environmental pollution is harmful to humans, animals, and vegetation, with health consequences depending on the pollution type, severity of the exposure, and species-specific tolerance [14]. In the worst-case scenarios, long-term pollution can lead to complete degradation of vegetation, resulting in so-called "industrial barrens" [15,16]. A common approach to evaluate the effect of pollutants on biological systems is gradient studies, representing gradual changes in pollution level, e.g., across the sites located at different distances from the pollution source [17,18].…”