# Composting as a Sustainable Approach for Managing Mercury-Contaminated Aquatic Biomass

## TL;DR

This study explores composting as a way to manage mercury-contaminated aquatic plants from gold mining areas, showing some stabilization of mercury but not meeting fertilizer standards.

## Contribution

The study evaluates composting as a sustainable method for mercury-contaminated biomass and provides insights into mercury stabilization and compost quality.

## Key findings

- Composting reduced total mercury content in biomass over 170 days.
- Final compost had higher mercury concentration due to biomass reduction.
- Mercury stabilized in less bioavailable forms, suggesting low risk to biota.

## Abstract

In this study, composting as an alternative approach for managing mercury-contaminated biomass in water bodies affected by gold mining in the Choco department was evaluated. A single-factor experiment with three treatments containing varying amounts of Eleocharis interstincta biomass sourced from mercury-contaminated sites was designed. During the composting process, physicochemical parameters were monitored such as temperature, pH, and electrical conductivity, while analyzing the behavior of mercury through mass balance assessments. Additionally, we determined the bioavailability of mercury in the final compost and characterized the physicochemical parameters of each compost sample. The mercury mass balance indicated a decrease in the total mercury content in the initial biomass over the composting period of 170 days. However, the total mercury concentration in the final compost increased due to the transformation and subsequent reduction of the original biomass. Mercury speciation analysis revealed that mercury was predominantly associated with the less bioavailable fractions (F4 and F5), suggesting its stabilization and low availability to biota. Therefore, the final compost has the potential to restore degraded soils by improving moisture retention, porosity, and soil fertility, thereby promoting plant growth. However, it does not fully meet the national and international technical standards for solid organic fertilizers or compost.