Effects of arbuscular mycorrhizal fungi on the removal of emerging organic pollutants in constructed wetlands

Ing. Bo Hu

Doctoral thesis

Abstract:

The symbiotic relationships between AMF (R. irregularis) and plant roots (G. maxima) could successfully establish in CWs. However, mycorrhizal status in plant roots showed differences among the four substrate systems. The addition of adsorptive substrates (perlite, vermiculite, or biochar) in CWs was more conducive to forming AM symbiosis than sand. AMF enhanced nutrient uptake by the host plant, thereby significantly promoting the growth of G. maxima. Meanwhile, AM symbiosis had an essential function in CWs, which improved host plant resistance to EOPs’ stresses by increasing antioxidant enzymes (POD and SOD) and soluble protein contents in plant tissues and decreasing oxidative damage (MDA and O2•-). The transformation of EOPs and their metabolites in plant tissues differed among the eight selected EOPs. Ibuprofen, diclofenac, hydrochlorothiazide, chloramphenicol, furosemide, gemfibrozil, and EOPs’ metabolites (2-hydroxy ibuprofen, carboxy ibuprofen, and 4’-hydroxy diclofenac) mainly accumulated in the roots, but triclosan and triclocarban are more likely to accumulate in the shoots. Surprisingly, AM symbiosis enhanced the translocation of EOPs from roots to shoots in all substrate systems, resulting in a higher amount of EOPs in the shoots of inoculated plants than that of non-inoculated plants. Meanwhile, AM symbiosis promoted the accumulation of EOPs in plant roots in sand and vermiculite systems, but an opposite effect of AMF on the accumulation of EOPs in plant roots was observed in perlite and biochar systems. The addition of adsorptive substrates (perlite, vermiculite, or biochar) promoted the removal efficiencies of EOPs in CWs because they had positive effects on enhancing the accumulation of EOPs in the rhizosphere and facilitating the uptake of EOPs by plant roots. Meanwhile, AMF might potentially influence EOPs removal in CWs, and this ability could be affected by the type of substrates. The contents of all selected EOPs (except triclosan, which the concentration was below the detection limit) and their metabolites (2-hydroxy ibuprofen and carboxy ibuprofen) in the rhizosphere soil of sand and perlite systems with AMF inoculated treatments were higher than those in non-AMF controls. However, a lower accumulation of EOPs (e.g., hydrochlorothiazide and triclocarban) was observed in the rhizosphere of vermiculite and biochar systems with AMF treatments were lower than those in non-AMF controls. The predominant removal process of EOPs in the present study could be attributed to the adsorption of substrates and the attached microbes. Consequently, AMF had positive effects on pollutant removal in sand systems but insignificant effects in perlite, vermiculite, and biochar systems. In sand systems, AM symbiosis improved the treatment performance of conventional pollutants. Compared to non-AM inoculated treatments, the removal efficiency of TOC, PO43--P, NH4+-N, TN in AMF inoculated treatments significantly improved by 6.19%, 10.92%, 14.82%, and 10.92%, respectively. For EOPs removal (ibuprofen and diclofenac as an example), the removal efficiencies of ibuprofen and diclofenac in sand systems with AMF inoculated treatments were 5.82-13.88% and 2.23-21.07% higher than those with non-AMF inoculated treatments, respectively. It is worth noting that the addition of AMF effectively reduced the concentration of EOPs’ metabolites (2-hydroxy ibuprofen, carboxy ibuprofen, and 4’-hydroxy diclofenac) in the effluent of all four substrate systems. Although the application of adsorptive substrates in CWs showed a more critical role in pollutant removal than AMF inoculation, AMF may also have the potential to enhance the performance of CWs for wastewater purification. Our results provide a good starting point for applying AMF in the phytoremediation of EOPs in full-scale wetland systems. Based on this study, additional studies are necessary to investigate the role of AMF in the purification of wastewater in more realistic c

Abstract:

onditions, such as treating real wastewater, feeding with more suitable hydraulic conditions (e.g., a long-term flooding condition or a tidal flow with more frequent water change cycle), or studying on large-scale systems. Meanwhile, further attention should be paid to the mechanisms by which AMF affects EOPs removal in CWs, for example, the impacts of AMF on EOPs’ metabolic pathways in CWs, including microbial degradation, plant uptake, adsorption and/or desorption by substrate and attached microbes.

Keywords

Constructed wetlands, Arbuscular mycorrhizal fungi, Emerging organic pollutants, Purification, Contaminant removal

Language used: English

Date on which the thesis was submitted / produced: 11. 4. 2022

Thesis defence

• Supervisor: doc. Zhongbing Chen

Czech University of Life Sciences Prague

Faculty of Environmental Sciences

Doctoral programme / field:
Environmental Sciences / Applied and Landscape Ecology