Phytoremediation of leachate, erosion control, and slope stabilization with [Vetiveria zizanioides (L). NASH] in Fajardo, Puerto Rico.

Abstract

This study assessed the use of Vetiveria Zizanioides (L.) Nash as a viable alternative to reduce excess of final disposal volume of leachate and soil erosion from a landfill sideslope. A total area of 4-acres was planted with contour hedgerows of Vetiveria Zizanioides (L.) Nash. Moreover, the vetiver system was supplemented with a drip irrigation system which allowed the application of gradual mixes of leachate to water ratio. Thirty-one (31) erosion events were recovered from the treated slope using six collectors localized between a known number (3 or 6) of vetiver hedgerows. Monthly precipitation was recorded by a Campbell Scientific weather station (ET107) and used to (1) calculate the kinetic energy (EI30) of specific storms and (2) develop RUSLE soil loss estimates per each storm event. Vetiver’s growth was also monitored to access its survivability under leachate rich conditions, poor soil fertility and a high degree compaction. An application rate of 219 gallons/acre (876 gallons for the entire 4-acres) proved enough to reduce excess volume of leachate, significantly. Treatment A presented the largest reduction of soil erosion, from 295.3 ton/acre-sampling event, to 0.06 ton/acre-sampling event. However, mean measured soil erosion did not exceed 30.53 ton/acre-sampling event for treatment B. It became apparent that at rain intensities greater than 4 foot-ton/acre-sampling event, soil erosion was inevitable.

Soil loss seemed to be more affected by slope gradient than slope length. A set of three (3) vetiver hedges was enough to reduce soil erosion on slopes between 30 and 40% gradient. Results suggest that the implementation of a vetiver system for phytoremediation purposes, is a solution for controlling excess volume of leachate and reducing soil erosion; thus, extending the useful life of landfills across Puerto Rico.