Impact of temperature variations on chemical and biological attributes of a zinc and cadmium contaminated soil remediated with biochar

Abstract

The ability to immobilize contaminants and recover soil functionality with the use of biochar is already known, however it is necessary to assess whether this ability is maintained in conditions of climate change. In this project, we aim to evaluate the effect of ambient temperature variation on chemical and biological attributes in technosoil contaminated with zinc (Zn) and cadmium (Cd) and remediated with biochar pyrolysed at two temperatures. Contaminated soil collected from a mining area in Vazante (MG) will be used, which will receive the addition of pyrolyzed sugarcane straw biochar at 350 and 750 °C, and incubated in controlled environments under two temperatures (20 and 30 °C). Chemical analyzes will be carried out for soil characterization, speciation of the soil solution, sequential chemical extraction of Zn and Cd; thermogravimetric analysis; and microbiological analyzes involving respirometry, b-glucosidase enzyme quantification and genetic sequencing of the microbial community (gene 16S V4). It is expected that the application of biochar as well as the heating of the environment alter the biogeochemistry of Zn and Cd in order to change their distribution in the soil and in the solution. From the chemical point of view, it is expected that the application of pyrolyzed biochar at 350ºC will favor the immobilization of Zn and Cd to the point of reducing the levels of these elements in the exchangeable fraction and increasing their levels in the fractions linked to carbonate and organic matter. Furthermore, it is expected that these alterations in the soil solid phase reflect in the soil solution, to the point of increasing the Zn and Cd species associated with carbonate and hydroxide [(ZnCOƒ, CdCO3, Zn(OH)‚, Cd(OH )2] From a microbiological point of view, the exogenous addition of chemically stable carbon is expected to reduce the decomposition of soil organic matter to the point of preserving the immobilization of Zn and Cd in the soil organic phase. of pyrolyzed biochar at 750ºC will reduce heat conduction in the soil to the point of preserving the microbial community and its ecosystem services.