How Hybrid Aspen Trees Clean Up Industrial and Farm Pollution

Jenn Hoskins
23rd March, 2024

How Hybrid Aspen Trees Clean Up Industrial and Farm Pollution

Image Source: Natural Science News, 2024

Key Findings

  • In Estonia, hybrid aspen trees can absorb heavy metals from contaminated soils
  • Trees absorb more metals in their first 10 years than in the following 11-21 years
  • Despite some success, 20 years is not enough for full soil restoration in polluted areas
In recent years, the issue of soil contamination by heavy metals has become a pressing concern. These toxic substances, which include elements like arsenic, cadmium, and lead, can persist in the environment, accumulate in plant tissues, and ultimately enter the human food chain, posing significant health risks[2]. The process of phytoremediation, using plants to absorb and contain these metals, has emerged as a promising solution to mitigate the impact of soil pollution[2]. However, the effectiveness of different plant species in various environmental conditions remains an area of active research. A study conducted by the Estonian University of Life Sciences has shed new light on the phytoremediation capabilities of hybrid aspen (Populus tremula × Populus tremuloides Michx.) in Estonia's hemiboreal climate, characterized by cold temperatures and mixed forest vegetation[1]. This research is particularly important because, until now, there was no information on how effectively these fast-growing trees could restore soil contaminated by heavy metals in this specific region. The study focused on assessing soil contamination and the uptake of heavy metals by mature hybrid aspen plantations situated near industrial pollution sources, such as a cement factory and an oil shale mining area. These polluted sites were contrasted with a reference plantation that had been established on former agricultural land, which had been subjected to fertilization and liming before being converted into forestland. After twenty-one years, researchers collected soil samples from the top 10 cm layer and analyzed the aboveground biomass of the trees, separating wood formed during the trees' early (1-10 years) and late (11-21 years) growth stages. The results showed that the soil in industrially polluted areas had higher concentrations of heavy metals compared to the reference plantation and standard levels for unpolluted soils. Interestingly, the highest levels of these metals in the tree biomass were found in the oil shale quarry spoil, although the poor growth in this area meant that the overall accumulation in the biomass was low. One notable finding was that cadmium behaved differently from other heavy metals, accumulating less in the wood and more in the bark. Additionally, the concentration of several heavy metals, including cadmium, chromium, copper, iron, manganese, nickel, and zinc, was higher during the first decade of the trees' growth compared to the second decade. This suggests that the trees were more effective at absorbing heavy metals from the soil during their earlier stages of development. The study also revealed that the reference plantation had high pools of heavy metals in the aboveground biomass, indicating that the trees were effective in removing the residue of heavy metals from the previous agricultural practices. This demonstrates the potential of hybrid aspen to clean up soils that have been contaminated by past activities such as fertilization and liming[3]. Despite these promising results, the researchers concluded that two decades of afforestation with hybrid aspen is insufficient for complete ecosystem restoration from heavy metals in areas with industrial pollution. This implies that while hybrid aspen can contribute to the reduction of heavy metals in the soil, a longer period or additional measures may be necessary to fully restore these contaminated environments. The findings of this study are significant as they contribute to the understanding of how different soil conditions, such as pH, can influence the uptake and accumulation of heavy metals by plants[3]. The detailed soil maps produced by the LUCAS topsoil survey, which identify areas with elevated heavy metal concentrations, can be used to target phytoremediation efforts more effectively[4]. In conclusion, the research from the Estonian University of Life Sciences offers valuable insights into the viability of using hybrid aspen for soil restoration in hemiboreal climates. It also highlights the need for long-term monitoring and management strategies to address soil contamination, an issue that continues to be a major environmental challenge in Europe and around the world.

EnvironmentPlant ScienceAgriculture


Main Study

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

Published 20th March, 2024

Related Studies

2) Phytoremediation of heavy metals--concepts and applications.

3) The Impact of Soil pH on Heavy Metals Uptake and Photosynthesis Efficiency in Melissa officinalis, Taraxacum officinalis, Ocimum basilicum.

4) Maps of heavy metals in the soils of the European Union and proposed priority areas for detailed assessment.

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