Purpose

The research aimed to investigate properties and functions of soils constructed from alkaline mining wastes of different origin to remediate the industrial barren resulted from long-term emissions of the copper-nickel factory in the Subarctic region (Kola Peninsula, Russia). Conventional indicators of the remediation effectiveness (pH and metal content in geochemical fractions) were related to the indicators of soil functions such as biomass production, accumulation of organic carbon, microbial activity, and soil respiration.

Materials and methods

The experimental area included two sites with polluted and degraded Podzol and Histosol soils located in 1.5 and 0.7 km from the nonferrous (Cu-Ni) smelter, respectively. At the sites, artificial soil constructions were made from mining wastes or quarry sand covered by the vermiculite layer with lawn grasses planted on top. Plant biomass was collected every year starting from the experiment set-up. In 5 to 8 years, soil samples were collected on the layer basis, and chemical, biological, and morphological properties were analyzed. Sequential fractionation of metals was conducted using a modified Tessier’s scheme. The microbial biomass and its respiration activity were determined. Micromorphological studies were conducted using an optical microscope. Soil respiration was measured on-site by IRGA with simultaneous observations of soil moisture and temperature.

Results

The plant growth and residues' deposition at both experimental sites triggered carbon accumulation and resulted in 2–3 times higher content of organic carbon in the upper constructed soil layer compared to the initial content in mining wastes. Carbon accumulation was a key driver for the development of soil microbial communities and had a positive effect on the metal immobilization. This effect was strengthened by high pH inherited from the alkaline wastes and resulted in the performance of constructed soils as geochemical barriers. In their upper layers, where the root biomass was the highest, about 30–60% of Cu and Ni were bound by organic matter. In the underlying polluted soil, the most toxic water-soluble metal fraction was completely neutralized; and the metal concentrations in exchangeable fraction decreased by a factor of four improving the habitat conditions of the microbiome. Organic matter accumulation by clay material with the formation of organo-mineral films was found in the vermiculite-lizardite variant.

Conclusion

Soil constructions made from alkaline mining wastes in the Subarctic supported the development of plant and microbial communities, organic matter accumulation, and metal immobilization. This technology allows protecting the environment from further pollution under the continuous emissions of the copper-nickel factory.

中文翻译：

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亚弧带重金属污染区碱性构造土壤中有机质的积累

目的

这项研究旨在调查用不同来源的碱性采矿废料建造的土壤的性质和功能，以补救由于亚北极地区（俄罗斯科拉半岛）的铜镍工厂长期排放而导致的工业贫瘠。修复效果的常规指标（地球化学部分中的pH和金属含量）与土壤功能的指标相关，例如生物量的产生，有机碳的积累，微生物活性和土壤呼吸。

材料和方法

实验区域包括两个地点，分别位于距离有色金属冶炼厂1.5公里和0.7公里处的Podzol和Histosol污染土壤和退化土壤。在现场，人造土壤建筑是由采矿waste石或by石覆盖的ver石砂制成的，顶部with草。从实验设置开始，每年都会收集植物生物量。在5至8年中，逐层收集土壤样品，并对化学，生物学和形态学特性进行分析。使用改进的Tessier方案对金属进行顺序分馏。测定了微生物的生物量及其呼吸活性。使用光学显微镜进行了微观形态学研究。

结果

在两个实验地点的植物生长和残留物的沉积触发了碳的积累，并导致上部建筑土壤层中有机碳的含量是采矿废料中初始含量的2-3倍。碳积累是土壤微生物群落发展的关键驱动力，对金属固定化具有积极作用。从碱性废物中继承的高pH值增强了这种效果，并导致了人造土壤作为地球化学屏障的性能。在根生物量最高的上层，约有30-60％的Cu和Ni被有机物结合。在下面的污染土壤中，毒性最高的水溶性金属部分被完全中和；金属中可交换部分的浓度降低了四倍，从而改善了微生物组的生境。在clay石-蜥蜴石变体中发现了粘土材料中有机物积累并形成有机矿物膜的现象。

结论

在亚北极地区，由碱性采矿废料制成的土壤结构支持了植物和微生物群落的发展，有机物质的积累和金属的固定化。在铜镍工厂连续排放的情况下，这项技术可以保护环境免受进一步污染。