Project Number: WVA00138
CRIS Number: 0180958
OXYGEN RELEASE FROM PLANT ROOT SYSTEMS IN CONSTRUCTED WETLANDS
Investigators: Garbutt, K., Sexstone, A.
Performing Department: BIOLOGY (not on the list) -- 0480
Start Date: 11/15/1998
Termination Date: 11/30/2001
Reporting period: 11/15/1998 to 11/30/2001
Termination Report:
Knowledge of how much oxygen various wetland plant species leak through their
roots into the rhizosphere may assist in the design of effective constructed
wetlands for wastewater treatment. We used an agar medium containing a redox
indicator, as well as microelectrode measurements of oxygen gradients near roots
to compare radial oxygen loss (ROL) from eight species: Acorus calamus, Iris
pseudoacorus, Juncus effusus, Phalaris arundinacea, Pontideria cordata, Schoenoplectus
tabernaemontani, Typha latifolia, and Zea maize as a non-wetland control. ROL
ranged from 0 to 9.6 picomoles oxygen per cm of measured root per second. The
ratio of oxidized fine root to coarse roots ranged from 2 % to 25 %. Some species
could oxidize the redox indicator in the agar medium, but did not produce oxygen
gradients that could be detected with the microelectrode. We found that plants
have differing anatomical patterns of ROL, and that those patterns vary with
conditions in the rooting environment. For example, when grown in drained conditions,
Acorus calamus had the highest proportions of coarse roots oxidizing the redox
indicator, and the highest oxygen flux detected by the microelectrode method.
Acorus grown in strongly anaerobic sediments (reduced treatment) decreased the
length of oxidizing roots compared to the same plant grown in drained conditions.
Similar patterns were observed in the other species tested with the exception
of Typha, which responded to the reduced treatment with an increase in oxidizing
root length. However oxygen gradients adjacent to roots of Typha were few and
weak, even though this species often is chosen for wetland plantings and is
known to reduce biological oxygen demand in constructed wetlands. Our data highlight
the difference in effective oxygen supply to wetland plant roots which allow
their survival in anoxic environments, and leakage of this oxygen to create
an aerobic rhizosphere which might enhance pollutant remediation in constructed
wetlands.
Publications:
Coleman, J., K. Hench, A. Sexstone, G. Bissonnette, J. Skousen, and K. Garbutt.
2001. Treatment of domestic wastewater by three plant species in constructed
wetlands. Water, Air and Soil Pollution 128:283-295
Christ, M., A. Sexstone, and K. Garbutt. 2002. Testing plant roots for radial
oxygen loss. Journal of Applied Ecology. in preparation.
Stover, D., K. Garbutt, and A. Sexstone. 2002. Response of clonal genotypes
of Juncus effusus to differing nutrient regimes. Journal of Enviornmental Quality.
in preparation.
Impact:
Acorus and Juncus might be effective in combined plantings because of their relatively high rates of radial oxygen loss and their differening root architecture which would supply oxygen to different strata of the constructed wetlands.