Effect of arbuscular mycorrhizal fungi on treatment of heavy metal under different N:P ratios in constructed wetlands

B.Sc. Carlos René Cárdenas Muñoz

Master's thesis

Abstract:

The bioremediation of heavy metal pollution assisted by arbuscular mycorrhizal fungi (AMF) is one of the new natural approaches to enhance water treatment, moreover, the effect of the AMF in the removal of metals from wastewater has been widely studied. However, the influence of different ratios of N:P on the effectiveness of this removal has not been much evaluated even knowing that agricultural or industrial usage of compounds of nitrogen and phosphorus is growing with the increase of economic activities. The purpose of this thesis is to assess the effect of AMF on the treatment of heavy metal under different N:P ratios in constructed wetlands (CWs). The experimental setup consisted of 12 different CWs made out of PVC pipes that worked as subsurface vertical flow CW, vegetated with Iris Wilsonii and the AMF was Rhizophagus irregularis. From these experimental systems, there were treatments with and without the presence of AMF, with and without heavy metal pollution and three different N:P ratios (1:1, 1:5 and 1:10). Water samples were taken for further analysis of pH, Rh, NH4+, Total Organic Carbon (TOC), Total Nitrogen (TN), PO43, NO2-, NO3-, copper (Cu) and lead (Pb) every five days starting from September 16th to November 15th, 2020 Furthermore, samples from plant roots, shoots and stems were taken to analyze AMF colonization and heavy metal distribution in the systems. The results show that the highest intensity of AMF colonization with 26.8% is from the system M_P1_HM corresponding to the system with mycorrhiza presence under a N:P ratio of 1:1 and treated with heavy metal polluted water, the intensity was decreasing when the N:P ratio was changing to 1:5 and 1:10. Regarding the metal distribution in the experimental CW, the concentrations were analyzed in the laboratory for each part (substrate, plant roots, shoots and water). The highest concentration was found in the roots for both Cu and Pb, and the concentrations were decreasing with the increase of N:P ratio. The heavy metal removal efficiency was also assessed and the results were that the impressive efficiencies of more than 95% in all the systems were possible to the complex reactions between different aspects of the SSVF CW such as soil, plants and microbiota. The presence of the AMF had a positive influence on the difference of these efficiencies and it was related also to the different N:P ratios and their effect on AMF colonization.

Keywords

Heavy metals, Constructed wetlands, Arbuscular Mycorrhizal Fungi, N, P ratios, Water pollution

Language used: English

Date on which the thesis was submitted / produced: 30. 3. 2021

Thesis defence

• Supervisor: doc. Zhongbing Chen

Czech University of Life Sciences Prague

Faculty of Environmental Sciences

Master programme:
Environmental Geosciences