Investigations of subsurface flow constructed wetlands and associated geomaterial resources in the Akumal and Reforma regions,Quintana Roo,Mexico |
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Authors: | Mark P S Krekeler Pete Probst Misha Samsonov Cynthia M Tselepis William Bates Lance E Kearns J Barry Maynard |
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Institution: | (1) Department of Environmental Science and Policy, George Mason University, Fairfax, VA 22030, USA;(2) Department of Earth and Environmental Sciences, University of Illinois at Chicago, 845 W. Taylor St., Chicago, IL 60607, USA;(3) United States Environmental Protection Agency, Region 5, Water Division, 77 West Jackson Boulevard (WU-16J), Chicago, IL 60604, USA;(4) Department of Geology and Environmental Sciences, James Madison University, MSC 7703, Harrisonburg, VA 22807, USA;(5) Department of Geology, University of Cincinnati, Cincinnati, OH 45221-0013, USA |
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Abstract: | Subsurface flow constructed wetlands in the village of Akumal, Quintana Roo, Mexico were surveyed to determine the general
status of the wetland systems and provide baseline information for long term monitoring and further study. Twenty subsurface
flow wetlands were surveyed and common problems observed in the systems were overloading, poor plant cover, odor, and no secondary
containment. Bulk mineral composition of aggregate from two subsurface flow constructed wetlands was determined to consist
solely of calcite using bulk powder X-ray diffraction. Some soil structure is developed in the aggregate and aggregate levels
in wetlands drop at an estimated rate between 3 and 10 cm/year for overloaded wetlands owing to dissolution. Mineral composition
from fresh aggregate samples commonly is a mixture of calcite and aragonite. Trace amounts of Pb, Zn, Co, and Cr were observed
in fresh aggregate. Coefficients of permeability (k) varied from 0.006 to 0.027 cm/s with an average values being 0.016 cm/s. Grain size analysis of fresh aggregate samples
indicates there are unimodal and multimodal size distributions in the samples with modes in the coarse and fine sand being
common. Investigations of other geologic media from the Reforma region indicate that a dolomite with minor amounts of Fe-oxide
and palygorskite is abundant and may be a better aggregate source that the current materials used. A Ca-montmorillonite bed
was identified in the Reforma region as well and this unit is suitable to serve as a clay liner to prevent leaks for new and
existing wetland systems. These newly discovered geologic resources should aid in the improvement of subsurface flow constructed
wetlands in the region. Although problems do exist in these wetlands with respect to design, these systems represent a successful
implementation of constructed wetlands at a community level in developing regions. |
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Keywords: | Constructed wetlands Mineralogy Carbonate aggregate Akumal |
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