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

Sylwia Siebielec,Piotr Sugier,Tomasz Stuczyński,Grzegorz Siebielec,Jarosław Grządziel,Małgorzata Woźniak,Anna Gałązka

doi:10.3390/molecules25235638

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.

Highlights

The mining and smelting of zinc (Zn) and lead (Pb) has contributed to the creation of a large number of solid waste deposit sites as its legacy
The analysis revealed more intense processes of Zn, Cd, and Pb solubilisation in the root zone of all plants growing on flotation waste (FW), as opposed to slag waste (SW) where metal extractability was generally lower in soils affected by plants
Our study puts a new light on the complexity of survival and adaptation mechanisms of pioneer plant species colonizing metalliferous waste, which initiates the soil formation process

Summary

Introduction

The mining and smelting of zinc (Zn) and lead (Pb) has contributed to the creation of a large number of solid waste deposit sites as its legacy. Network for Soil (EIONET-SOIL), there are 2.5 million potentially contaminated sites caused by point pollution, and 342,000 identified contaminated sites [2] In many regions, such as Silesia in Southern Poland, Zn and Pb slag waste piles are distributed across a mosaic of various land use types, including urbanised areas, arable lands, hobby gardens, forests, and recreational areas. In the Silesian Voivodship, metalliferous waste heaps are spread over an area of about 160 km2 [1] These waste piles are often characterised by harsh physical and water conditions, which result in extremely unfavourable conditions for plant growth due to a lack of nutrients, high concentration of phytotoxic metals, and limited access to water. The secondary dispersion of PTTEs from smelter waste piles causes further pollution of adjacent soils, which are often used as arable lands or for hobby gardening [3]

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