ORIGINAL ARTICLE Modeling desorption kinetics of the native and applied zinc in biochar-amended calcareous soils of different land uses M. Zahedifar 1 • A. A. Moosavi 2 Received: 30 August 2016 / Accepted: 10 August 2017 Ó Springer-Verlag GmbH Germany 2017 Abstract Soil components including organic matter (OM) are of vital importance in sorption/desorption kinetics of potentially toxic trace elements (PTEs), e.g., zinc (Zn). Nowadays, biochars as a source of OM have received increased attention because of their potential for improving soil properties. Effect of wheat straw biochar (0, 1.5 and 3% w/w) and zinc levels (0 and 10 mg Zn kg -1 soil as ZnSO 4 Á7H 2 O) on Zn desorption kinetics was evaluated in an incubation experiments with agricultural, rangeland and forest soils. There was a rapid desorption rate during the first 2 h, followed by a slower rate during the next 14 h in all soil types. High rates of Zn desorption were observed in Zn-treated soils. In all soil types, biochar reduced Zn desorption, whereas, Zn increased it. The highest amounts of Zn desorption in both no Zn-treated and Zn-treated soils corresponded to the forest soil followed by the rangeland and agricultural soils. The simple Elovich and two-constant rate models were the best models to describe Zn desorption from the soils. Biochar decreased the release of Zn to the soil solutions. Therefore, it may reduce the probable excessive amount of Zn uptake by plant root, transfer to food chain, Zn leaching to surface and subsurface waters and their possible risks to human health. These issues should be considered in management practices for different land uses under various Zn application strategies. Fur- thermore, evaluation of other levels/sources of biochar and Zn on desorption kinetics of Zn in soils of various land use types is recommended. Keywords Kinetic models Á Rangeland Á Forest Á Agriculture Á Zinc sulfate Introduction The fate and bioavailability of potentially toxic trace ele- ments (PTEs) are mainly controlled by the following pro- cesses: (a) sorption onto the soil solid particles from the soil solution, (b) desorption from the soil solid particle into the soil solution and (c) their precipitation–dissolution (Strawn and Sparks 2000). Understanding the kinetics of these processes is important for prediction of PTEs behavior in the environment. Soil consists of different components which are responsible for PTEs binding. Organic matter (OM), as a soil component, is the dominant phase controlling the PTEs (e.g., zinc, Zn and copper, Cu) sorption/desorption kinetics. Weng et al. (2001) reported that OM is of the major sorbent controlling PTEs reactions in the soils. At different conditions such as different land uses the importance of different soil attributes such as OM, pH, amount of PTEs for their sorption/desorption process may differ. On the one hand, it is reported that about 30% of the global agricultural soils and human population is Zn-defi- cient due to low soil Zn content/bioavailability (Mertens and Smolders 2013). On the other hand, the mobility, bioavailability and toxicity of PTEs (e.g., Zn) in polluted soils are controlled by applying soil conditioners. Soil pH, OM, clay content, cation exchange capacity (CEC) and Fe/ & M. Zahedifar mzahedifar@gmail.com A. A. Moosavi aamousavi@gmail.com 1 Department of Rangeland and Watershed Management, College of Agriculture and Natural Resources, Fasa University, Fasa, Iran 2 Department of Soil Science, College of Agriculture, Shiraz University, Shiraz, Iran 123 Environ Earth Sci (2017)76:567 DOI 10.1007/s12665-017-6895-z