Mercury Levels in Groundwater Near Artisanal Small-Scale Gold Mines in Migori County, Kenya.
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Date
2024-11
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Kenyatta University
Abstract
In Migori County, Artisanal and small scale gold mining (ASGM) is an economic
activity that uses mercury during the amalgamation process to obtain gold. The waste
generated in form of soil tailings and pan-pond water contains mercury and is located
close to community boreholes. The waste from the mines can lead to mercury
contamination in groundwater. Boreholes are one of the most used sources of drinking
water in Migori County. Ingestion of contaminated water is one of the ways mercury
can get into the human body. A research done by Center of Environmental Justice and
Development in 2017 showed that mercury is present in human hair from people around
Masara mine, Migori County. Therefore, the study sought to establish the mercury
levels in groundwater near Artisanal Small-Scale Gold Mines in Migori County.
Specifically, the study determined mercury concentration in groundwater from
boreholes, soil tailings and pan-pond water located near five mine sites during dry and
wet seasons. The five mines were: -Masara, Osiri Matanda, Macalder, Kitere and
Kehancha. The study used cross sectional-analytical study design. The research focused
on boreholes found within a distance of 6 km from the five mines. Out of the 46
boreholes mapped, 15 (32% of 46) were proportionately sampled to obtain groundwater
samples during dry and wet seasons. From the five mines targeted, 20 pan-pond water
and soil tailings were collected in both dry and wet season as per respective sampling
protocols applied. Mercury level from the samples was determined by use of
Inductively Coupled Plasma –Mass Spectroscopy (7900 ICP-MS) at KEPHIS
laboratory. Paired t-test was used to compare the means of the levels of mercury in
groundwater obtained within the two different seasons. Measures of central tendency
was used to describe the sets of data obtained after laboratory analysis of samples. The
study established that during the dry season, all of the boreholes had groundwater
mercury levels higher than the recommended limit by KEBS of 0.001 mg/L. There was
a decrease in the levels of mercury in groundwater as distances from the mine increases.
However, during the wet season, all of the boreholes had mercury levels below the limit
of detection. The study established a significant difference on the levels of mercury in
groundwater between wet and dry seasons at a 95% confidence level. In the mines, the
study found that mercury levels in soil tailings and pan-pond water were above the
NEMA effluents discharge standards of 0.05 mg/kg and 0.05 mg/L respectively in the
dry season. During the wet season, all pan-pond water achieved the recommended
mercury level of NEMA effluents discharge limits while the soil tailings had mercury
levels above the recommended limit. This study recommends a need to implement mine
waste remediation and, the borehole owners, licensed water service providers near the
mines to continuously conduct groundwater heavy metal analysis during the dry season
to protect their health. The county government to develop water related policies to
ensure safe water services to the community.
Description
A Thesis Submitted In Partial Fulfillment of the Requirements for the Award of the Degree of Master of Environmental Health in the School of Health Sciences, Kenyatta University. November, 2024
Supervisors;
1.Jackim Nyamari
2.Judy Mugo.