Metal Accumulation and Biomass Production in Young Afforestations Established on Soil Contaminated by Heavy Metals

Abstract

The restoration of forest ecosystems on metal-contaminated sites can be achieved whilst producing valuable plant biomass. Here, we investigated the metal accumulation and biomass production of young afforestations on contaminated plots by simulating brownfield site conditions. On 16 3-m2 plots, the 15 cm topsoil was experimentally contaminated with Zn/Cu/Pb/Cd = 2854/588/103/9.2 mg kg−1 using smelter filter dust, while 16 uncontaminated plots (Zn/Cu/Pb/Cd = 97/28/37/< 1) were used as controls. Both the calcareous (pH 7.4) and acidic (pH 4.2) subsoils remained uncontaminated. The afforestations consisted of groups of conifers, deciduous trees, and understorey plants. During the four years of cultivation, 2254/86/0.35/10 mg m−2 Zn/Cu/Pb/Cd were extracted from the contaminated soils and transferred to the aboveground parts of the plants (1279/72/0.06/5.5 mg m−2 in the controls). These extractions represented 3/2/3% of the soluble soil Zn/Cu/Cd fractions. The conifers showed 4–8 times lower root-to-shoot translocation of Cu and Zn than the deciduous trees. The contamination did not affect the biomass of the understorey plants and reduced that of the trees by 23% at most. Hence, we conclude that the afforestation of brown field sites with local tree species is an interesting option for their reclamation from an ecological as well as economic perspective.

Responses to Airborne Ozone and Soilborne Metal Pollution in Afforestation Plants with Different Life Forms

“…Cd and Zn even reached higher concentrations than in roots and therefore exceeded the toxicity threshold. This finding outlines the possible dissemination threat posed by spontaneous ruderal vegetation at e.g., brownfield sites, when primarily a phytostabilisation effect is targeted [ 47 ]. Zn contaminants retranslocated to nutrient stores over the winter [ 33 ] could have contributed to the greater Zn accumulation in the second year of the experiment compared with in the first year.…”

“…However, it remains unclear how plants react to elevated levels of airborne ozone and soilborne heavy metals in combination, as found at brownfield sites in populated regions. Antagonism or additivity of effects represents an important research gap, considering the potential consequences on the phytoremediation performance of spontaneously emerging or planted afforestations at brownfield sites [ 47 ].…”

Phytoremediation capacity of hybrid aspen at sites affected by industry and agriculture

“…The use of woody plants in polluted sites to reduce toxicants is considered a low cost and environmentally friendly method (Ali et al, 2013;Bhat et al, 2022). Trees can absorb and immobilise metal pollutants, as well as metabolise or accumulate organic and nutrient contaminants into biomass (Sherene, 2010;Bhat et al, 2022, Grünthardt-Georg, et al, 2022.…”

Cadmium up Taking and Allocation in Wood Species Associated to Cacao Agroforestry Systems and Its Potential Role for Phytoextraction

“…and Populus sp. in phytoextraction [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ], showing that these species could be used as an efficient and cost-effective method to remove Cd contamination from agricultural soils [ 22 , 36 ]. On the one hand, the benefits associated with accompanying trees in cacao agroforestry systems have been widely studied in terms of carbon capture, water use efficiency and other nutritional benefits [ 18 , 19 , 38 ].…”