Seyed Mohammad Hojjati

Increased CO₂ levels caused by human activities (e.g., fossil fuel consumption and deforestation) has become a major concern for climate change and caused environmental problems. Afforestation/reforestation can help mitigate CO₂ emission in the atmosphere by sequestering atmospheric carbon (C) in tree biomass. Herein, the above- and below-ground C sequestration of two pioneer tree species, including Acer velutinum Bioss and Alnus glutinosa L plantation stands of 25 (A25) and 35 (A35) years old were studied. The mean annual growth of diameter at breast height (cm/year) was significantly higher in A35 than A25, while the mean growth of height (m/year) was significantly higher in A25. The total and mean annual growth of the tree biomass and C storage (root and trunk) was significantly higher in A35. The amount of soil C sequestration in A35 was also significantly higher than in A25. The above-ground C sequestration and the annual average of C sequestration of the trees were positively correlated with soil moisture, pH, nitrogen, and phosphorus. Our study illustrates the benefits of considering stand age in the growth and developmental patterns of forest ecosystems in estimating terrestrial C stocks.

The rehabilitation of heavy metal-contaminated lands is a challenging issue worldwide. The application of effective eco-friendly techniques and materials is necessary for amending the contaminated soils, and the in-situ results should be examined. The present study investigated the effect of zero-valent iron-nanoparticles (Fe0-NPs) and cellulosic wastes (CW) on the lead (Pb) and cadmium (Cd) uptake and nutrients’ (N, P, K) concentration of maple seedlings in contaminated soil. First, one-year-old seedlings were planted in pots containing unpolluted soil (volume = 3 Kg), and then the soil was contaminated by adding Pb (0, Pb100, Pb200, and Pb300 mg kg-1) and Cd (0, Cd10, Cd20, and Cd30 mg kg-1) solutions. The CW (0, 10, 20, 30 g/100g soil) and Fe0-NPs (0, 1, 2, 3 mg kg-1) treatments were applied to the soil before and after Pb and Cd addition, respectively. The biomass of seedlings and the concentration of nitrogen, potassium, and phosphorus in leaves were measured. Leaves, stems, and roots were digested to measure the Pb and Cd concentrations. Results showed that CW and Fe0-NPs improved N, P, and K concentrations in leaves at all levels of contamination. The lowest concentration of Pb and Cd in all organs and treatments was observed in the highest level of Fe0-NPs. The cellulosic waste and Fe0-NPs (the highest level only) significantly increased the soil pH at all levels of contamination. Our findings suggested that the use of Fe0-NPs (3 mg kg-1) and CW (30g/100g soil) could be appropriate for reducing the bioavailability of Pb and Cd in contaminated soil and improving the growth of maple seedlings.

The purpose of this study is to investigate the effect of cellulosic wastes and nanoscale zero-valent iron (nZVI) on the soil properties and the nutrient uptake by Quercus castaneifolia C.A.Mey seedlings. The seedlings were planted in pots (unpolluted soil) and cadmium (Cd) was added to the pots in three concentrations (10, 20, 30 mg.kg⁻¹). Cellulosic wastes were mixed with the soil (at the same time as the planting) in four levels (W: 0, 10, 20, 30 g.100g⁻¹ soil). The reduction method was used to prepare nZVI, then the nanoparticles were injected into the polluted pots in four levels (N: 0, 1, 2, and 3 mg.kg⁻¹). The lowest concentration of Cd in leaves, stems and roots and for all the contamination levels was observed in N3. All the cellulosic wastes and N3 significantly increased the soil pH at all the levels of contamination. An increasing trend of the soil carbon (C) content was observed by adding the cellulosic wastes. The highest pH and C content were observed in W3. The lowest bioavailable Cd contents for all the contamination levels was observed in N3. According to the results, nZVI and cellulosic wastes could help the plants establishing in heavy metal-polluted lands.

Today, it is very important to protect plants in soils contaminated with metals. We investigated the behavior of cadmium during the establishment of oak seedlings (Quercus castaneifolia C.A. Mey.) under biochar influence. This study was conducted in pots with loamy soil. Cadmium was added to soil at 0, 10, 30, and 50 mg per kg of soil, indicated by Control, Cd10, Cd30 and Cd50. Biochar was produced at 500–550 °C from rice husk and added at 1, 3, and 5% (wt/wt) levels, indicated by B1, B3, B5, and mixed with soil at planting in three replications. Generally, increasing biochar rates had significant effects on seedling height, diameter, and biomass. This coincided with Cd immobilization in the contaminated soil which reflects a decrease in Cd concentrations in the plant bioavailability of Cd. The tolerance index increased significantly, by 40.9%, 56%, and 60.6% in B1, B3, and B5 with Cd50, respectively, compared to polluted soil. The percent of Cd removal efficiency for Cd50 was 21%, 47%, and 67% in B1, B2, and B5, respectively. Our study highlights that biochar can reduce Cd bioavailability and improve the growth of oak seedlings in contaminated soil.