Investigation of calcareous beach sands in the Akumal and Tulum areas for use in constructed wetlands,Eastern Yucatan Peninsula |
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Authors: | Mark P S Krekeler Erin P Argyilan Jill Lepp Lance E Kearns |
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Institution: | (1) Department of Geology, Miami University, Hamilton, OH 45011, USA;(2) Department of Geosciences, Indiana University Northwest, 3400 Broadway, Gary, IN 46408, USA;(3) Geology Program, George Mason University, Fairfax, VA 22030, USA;(4) Department of Geology and Environmental Sciences, James Madison University MSC7703, Harrisonburg, VA 22807, USA |
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Abstract: | Constructed wetlands can be a low-cost, ecologically based technology to locally treat domestic wastewater prior to discharge.
Wetland systems implemented in the resort village of Akumal in the state of Quintana Roo, in the Yucatan Peninsula of Mexico
have been considered moderately successful over approximately 10 years of operation. Yet the wide-scale implementation of
constructed wetlands has not occurred in the region nor throughout Mexico due largely to the cost of the crushed aggregate
used in these systems. Variation in the geotechnical and mineralogical properties of 29 samples of local calcareous beach
sands collected from the tourist areas of Akumal and Tulum in the Yucatan, Mexico were analyzed and compared to those of crushed
aggregate currently used in constructed wetland systems in Akumal. Powder X-ray diffraction on beach sand samples from Akumal
and Tulum indicates that the proportion of aragonite varies from 24 to 84%, calcite varies from 7 to 38% and Mg-calcite varied
from 8 to 57% compared to crushed aggregate which consists of 0–25% aragonite and 75–100% calcite. Compared to crushed aggregate
beach sands are unimodal and have better uniformity coefficients, making them a better geotechnical choice than crushed sands
with respect to these properties. Grain-size of the beach sands is much smaller compared to that of the crushed aggregate
currently used in the constructed wetland systems in Akumal which should enhance the efficiency of the filtration of organic
matter and bacteria. The average hydraulic conductivity measurements of 0.010 and 0.016 cm/s for beach sands from Akumal and
Tulum, respectively are comparable or less than the average of 0.016 cm/s for crushed aggregate currently used in engineered
wetland systems. Yet a combination of high bulk porosity, intragranular pores, and the presence of Mg-calcite observed in
beach sands may likely result in higher dissolution rates versus the crushed aggregate. Preliminary assessment suggests that
the use of local sand may be a technical, economic, and perceptual enhancement to the systems. Still a careful and thorough
analysis of the potential environmental and aesthetic impacts of mining beach sands is necessary. |
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