МЕЛИОРАЦИЯ ТЕХНОГЕННО ЗАГРЯЗНЕННЫХ ПОЧВ С ИСПОЛЬЗОВАНИЕМ ГИПСА: НЕЖЕЛАТЕЛЬНЫЕ ВОЗДЕЙСТВИЯ НА ОКРУЖАЮЩУЮ СРЕДУ

In the present study, we have grown perennial ryegrass on untreated and gypsum-treated soils under laboratory conditions. We found that gypsum represents an inadequate soil remediation option, as it aggravates environmental risks.В данном исследовании мы изучали влияние гипсования техногенно загрязненных почв на развитие райграса пастбищного в лабораторных условиях. Было выявлено, что добавление гипса в почву является неудовлетворительной техникой при ремедиации почв, так как приводит к экологическим рискам

CHALLENGES IN REDUCING PHYTOTOXICITY OF METALS IN SOILS AFFECTED BY NON-FERROUS SMELTER OPERATIONS

Lime is one of the effective agents for reducing the phytoavailability of metals in contaminated acidic soils. However, previous studies have shown that lime alone cannot reduce metal phytotoxicity to the desired extent in such soils. The goal of this study was to evaluate the effect of different amendment combinations (lime with and without Feand/or Mn-based amendments) on plant growth. A sample of Histosol (0-5 cm) was collected around a Cu/Ni smelter near Monchegorsk, Murmansk region, exhibiting total Cu and Ni concentrations in the soil of 6418 and 2293 mg kg-1, respectively. Likewise, a sample of forest litter (0-15 cm) was collected around a Cu smelter near Revda, Sverdlovsk region, exhibiting total Cu concentration in the soil of 5704 mg kg-1. Fe-Mn oxides were sourced from ferromanganese nodules in the Gulf of Finland, and iron powder was used as a precursor for iron oxides. Perennial ryegrass was grown in pots for 21 days under controlled laboratory conditions. Two dolomite doses were tested: 5% w/w (giving a soil pH of 6.5) and 20% w/w (giving a soil pH of 7.4). Over-liming stunted plant growth; therefore, the dolomite dose was set at 5% in the further experiments of the study. Importantly, the addition of 0.5% and 1% of Fe-Mn-oxides or iron powder did not improve the efficacy of the lime amendment in promoting plant growth in the soils. Therefore, the issue of reducing plant exposure to metals remained unresolved in the soils under study. © 2022, Russian Geographical Society. All rights reserved

Root Elongation Method for the Quality Assessment of Metal-Polluted Soils: Whole Soil or Soil-Water Extract?

Root elongation method may be implemented using two internationally accepted protocols: exposing plants to either soil-water extract or whole soil. But which of the two protocols is more suitable for root elongation analysis undertaken for the quality assessment of metal-polluted soils? Soils were sampled at various distances from the site of the Middle Urals Copper Smelter located in Russia. White mustard was used as a bioindicator. We observed considerable differences in root elongation under the two protocols. In plants grown in whole soil, root length inversely correlated with pollution index, but in soil-water extract, metal concentrations had no effect on root length. Nutrient and metal concentrations in the soil-water extract were not buffered, due to the absence of the solid soil phase. It is for this reason that in highly polluted soils, root growth was greater in soil-water extracts rather than in whole soils, whereas in background soils (in the absence of toxicity), root growth was greater in whole soils compared with soil-water extracts. The quantity, intensity, and capacity factors are a plausible explanation for the differences in root length between the two protocols. The soil-water extract does not represent actual soil with respect to the desorption-dissolution reactions that take place between the soil solid phase and the soil solution. For this reason, whole soil protocol should be used for measuring root elongation given that only under this protocol, direct contact between metal-polluted soil and test organisms correctly replicates the risks inherent in the actual soil habitat. © 2020, Sociedad Chilena de la Ciencia del Suelo