Methane and heavy metals levels from Leachates at Dandora dumpsite, Nairobi county, Kenya

Abstract

Rate of urbanization in Kenya has increased, resulting to increased generation of solid and liquid wastes. This has increased the use of landfills and dumpsites to manage wastes as well to reduce pollution. Landfills and dumpsites are the contributing sources of methane into the atmosphere and heavy metals in the environment. This study was to quantify the levels of methane and heavy metals in leachates from Dandora dumpsite, in Nairobi County. Methane and leachates samples were collected from twenty and ten sampling sites representative of the Dandora dumpsite, in a period of six months from November 2012 to April 2013. The sampling periods presented the short, dry and wet rainy seasons. This was to determine the effect of seasons on the level of analytes. Leachates were scooped from ten sampling trenches in Dandora dumpsite to analyse level of heavy metals viz Zn, Cu, Cd, Cr, Ni and Pb. Methane was collected using head space chambers. The levels of zinc metal were highest, at 3.58x105 µg/kg in November and lowest at 4.6x104 µg/kg in April. Levels of lead were also considerably high, ranging from 4.65x104 µg/kg in November to 9.58x103 µg/kg in April. Copper metal levels ranged from 1.61x104 µg/kg in November to 5.57x103 µg/kg in April. Nickel metal levels ranged from 7.92x103 µg/kg in November to 1.18x103 µg/kg in April. Levels of chromium metal were between 7.04x103 µg/kg in March to 1.43x103 µg/kg in November.Cadmium was only found at three sampling sites in December with total mean concentration 9.0x101 µg/kg. The part of dumpsite covered by vegetation, the inactive sites had lowest level of methane. The levels of methane ranged from below detectable level to as high as 3.78x106 µg/kg. Methane flux ranged from 0 ≤4.89x104 µg C m-2 h-1. It was found that the part of the dumpsite covered by vegetation, bear dry ground or/and the inactive site had lowest levels of methane or no methane was detected.