(173ak) Phytoremediation of soils contaminated using Phaseolus vulgaris L and amendments

In response to this pressing challenge, the current study focuses on evaluating the effects of these contaminants on Phaseolus vulgaris L. (common bean). The study aims to explore the efficacy of enhancing the remediation capabilities of Phaseolus vulgaris L. through the integration of biochar, compost, and mycorrhizae amendments. This innovative approach to phytoremediation holds promise as a sustainable solution for mitigating soil contamination by Hg and CPF, offering a multifaceted strategy that addresses both organic and inorganic pollutants.

The soil was removed from Segovia, Colombia, a municipality known for its heavy mining activity (more than 9000 hectares), heavily contaminated soils from Hg use, and agricultural use. pH 5.85, CEC of 158 cmol(+)·kg-1, CRA of 50.04%, humidity of 4.50%, and organic matter content of 19.73% were the original soil's measurements. To determine the Hg content and confirm the amount of metal in the soil, three arbitrary samples were taken. The average Hg concentration of the entire soil was found to be 24.56 mg·kg-1. After the soil was added to a rizhobox, seedlings of Phaseolus vulgaris L. that had already germinated and measured on average 9 cm in height were planted. Throughout days 15, 30, and 45, chemical and physical properties like pH, electrical conductivity, and organic matter were observed, along with the bioavailability of Hg and CPF. The soil has been contaminated with different concentrations of chlorpyrifos (CPF), an organophosphate pesticide, at three specific levels: 40 mg·kg-1, 80 mg·kg-1, and 120 mg·kg-1. These values were selected to represent a range of contamination conditions that may be encountered in agricultural settings and other areas impacted by pesticide use. By employing these varied concentrations, the objective is to comprehensively evaluate the effects and efficacy of the proposed remediation methods, allowing for a detailed comparative analysis.

It has been found that the combination of biochar with mycorrhiza has the highest efficiency in CPF degradation, while biochar has the lowest bioavailability of Hg. Although the control treatment shows a degradation of CPF over time, the application of amendments favors a greater degradation of this pollutant. While in the case of Hg, the control also decreases the bioavailability of Hg over time, it is the application of amendments that considerably decreases the bioavailability of Hg. In the case of the application of mycorrhiza alone, it shows that the bioavailable concentration of Hg is higher than in the other amendments, and this is reflected in the concentration of the metal in the plant, which presents a greater amount of the contaminant in the root, showing similar results to those reported in the literature (Cruz et al., 2021; Leudo et al., 2020; Saldarriaga et al., 2023).

The study offered thorough insights into mycorrhizae and biochar's (B+M) remediation potential for CPF and Hg-contaminated soils. The results consistently showed that a combination of biochar and mycorrhizae was the most effective treatment for lowering the amounts of these contaminants. The degradation process was greatly accelerated by the synergistic effect of this combination. The B+M treatments demonstrated impressive reduction levels; at 80 mg/kg concentrations, they routinely achieved about 70% reduction, and at 120 mg/kg doses, they frequently approached 90% reduction. The important role these amendments play in the bioremediation process is highlighted by their great efficacy. Natural deterioration caused a slight drop in CPF concentrations in the control samples, but throughout the trial, the control group's CPF levels were always the highest when compared to the other treatment groups. This result emphasizes the benefits of employing mycorrhizae and biochar over natural degradation alone, since the latter is unable to achieve appreciable reductions in pollutant levels in a reasonable amount of time.

References

Cruz, Y., Villar, S., Gutiérrez, K., Montoya-Ruiz, C., Gallego, J.L., Delgado, M. del P., Saldarriaga, J.F., 2021. Gene expression and morphological responses of Lolium perenne L. exposed to cadmium (Cd2+) and mercury (Hg2+). Sci Rep 11, 11257. https://doi.org/10.1038/s41598-021-90826-y

Leudo, A.M., Cruz, Y., Montoya-Ruiz, C., Delgado, M. del P., Saldarriaga, J.F., 2020. Mercury Phytoremediation with Lolium perenne-Mycorrhizae in Contaminated Soils. Sustainability 12, 3795. https://doi.org/10.3390/su12093795

Saldarriaga, J.F., López, J.E., Díaz-García, L., Montoya-Ruiz, C., 2023. Changes in Lolium perenne L. rhizosphere microbiome during phytoremediation of Cd- and Hg-contaminated soils. Environmental Science and Pollution Research 30, 49498–49511. https://doi.org/10.1007/S11356-023-25501-Y/METRICS