Variations of ambient temperature impacting chemical and biological attributes of a sediment contaminated with zinc and cadmium and remediated with biochar

Author(s)

Mariana Pezzatte Pollo

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2024-07-23

Examining board members

Luis Reynaldo Ferracciú Alleoni; Cristiano Alberto de Andrade; Letícia de Pierri

• Advisor: Luis Reynaldo Ferracciú Alleoni

Abstract

Biochar ’s ability to immobilize contaminants is well-known, but it is important to evaluate it under climate change conditions. Our objective was to evaluate the impact of ambient temperature variation (20°C and 30°C) on the chemical properties of a mine tailing contaminated with zinc (Zn) and cadmium (Cd) and treated with sugarcane straw (Saccharum officinarum) biochars pyrolyzed at 350°C (B350) and 750°C (B750). To evaluate the bioavailability of the contaminants, the characterization of the tailing and biochars, sequential chemical extraction, chemical speciation and desorption experiment were performed. Sequential extraction was separated into: exchangeable (F1), bound to organic matter (F2), bound to Fe and Al oxides (F3), and residual (F4). To explore the effects of temperature increase on soil organic matter decomposition, we evaluated total organic carbon (TOC) and dissolved organic carbon (DOC), CO2 e missions, tailing sensitivity to temperature changes, and βglucosidase activity. The addition of biochar was efficient in immobilizing Zn and Cd under simulated global warming conditions. With the increase in temperature, the control sample (without biochar) decreased the concentration in F2 and increased in readily available contaminants (F1). The addition of biochar reduced thermal decomposition and increased the percentage of contaminants bound to organic matter. B750 was more effective at retaining Zn at F2, while B350 was better at preserving organic matter and preventing Zn desorption after increasing ambient temperature. The elements were, predominantly, in the bioavailable forms (Zn²&#43 and Cd²&#43). Both metals released their soluble fractions in the first 5 min, but samples treated with biochar showed lower total desorption of the elements. The addition of biochar reduced the DOC content but increased the TOC content. The amount of DOC increased at 30°C in all treatments. The biochar also increased the sensitivity of the tailing to temperature changes, and the effect on the enzymatic activity varied with the pyrolysis temperature of the biochar, with B350 increasing the enzymatic activity, while B750 had no effect at 20°C. The application of biochar influenced the soil carbon content and microbial activity. (AU)

• FAPESP's process: 23/04271-0 - Impact of temperature variations on chemical and biological attributes of a zinc and cadmium contaminated soil remediated with biochar
• Grantee: Mariana Pezzatte Pollo
• Support Opportunities: Scholarships in Brazil - Master