The effect of leachate seepage from a landfill site on the quality of an urban river, Densu, that is the one of the main sources of water abstracted for treatment for most residents in the Accra Metropolitan area was determined by measuring the levels of heavy metals (As, Pb, Hg, and Cd) in the seepage and in the river itself using Atomic Absorption Spectrometry methods.
Heavy metal concentration upstream before leachate contamination was low and within WHO limits. The mean concentrations of arsenic, lead, mercury and cadmium were 0.026mg/l, 0.957mg/l, 0.025mg/l and 0.005mg/l, respectively in the leachate. Mean heavy metal concentration, two hundred metres downstream from the leachate discharge point (where water is drawn for domestic and drinking purpose) was 0.008mg/l for arsenic, 0.393mg/l for lead, 0.001mg/l for mercury while cadmium was not detected. Lead exceeded the WHO acceptable limit of 0.01mg/l for drinking water. Mean levels in the corresponding sediment samples were 0.015mg/kg for arsenic, <0.001mg/kg for lead, 0.004mg/kg for mercury and cadmium 0.151mg/kg.
Contamination factors computed were less than one (CF<1) for arsenic and lead in the sediments which imply low contamination and moderate contamination for cadmium (1 ≥ CF ≥ 3). Seepage of leachate from the landfill site into Densu must be monitored to ensure the quality of River Densu especially when it is being used as a drinking water source by downstream communities.
Table of Contents
1.0 INTRODUCTION
1.1 PROBLEM STATEMENT
1.2 JUSTIFICATION OF THE STUDY
1.3 OBJECTIVE OF THE STUDY
2.0 LITERATURE REVIEW
2.1 WATER QUALITY
2.2 ANTHROPOGENIC IMPACTS ON WATER QUALITY
2.3 PHYSICAL INDICATORS OF WATER QUALITY
2.3.1 CONDUCTIVITY
2.3.2 TOTAL DISSOLVED SOLIDS
2.3.3 TURBIDITY
2.3.4 COLOR, ODOR AND TASTE
2.4 CHEMICAL INDICATORS OF WATER QUALITY
2.4.1 pH
2.4.2 HARDNESS
2.4.3 SULPHATES
2.4.4 NITRATES
2.4.5 PHOSPHATES
2.5 BIOLOGICAL INDICATORS
2.6 HEAVY METALS
2.7 ARSENIC
2.7.1 EXPOSURE ROUTE FOR ARSENIC TO THE ENVIRONMENT
2.7.2 HEALTH EFFECTS OF ARSENIC
2.8 LEAD
2.8.1 EXPOSURE ROUTE FOR LEAD TO THE ENVIRONMENT
2.8.2 EFFECT OF LEAD ON AQUATIC LIFE
2.8.3 HEALTH EFFECTS OF LEAD
2.9 MERCURY
2.9.1 EXPOSURE ROUTE FOR MERCURY TO THE ENVIRONMENT
2.9.2 HEALTH EFFECT OF MERCURY
2.10 CADMIUM
2.10.1 EXPOSURE ROUTE FOR CADMIUM TO THE ENVIRONMENT
2.10.2 HEALTH EFFECT OF CADMIUM
2.11 SURFACE WATER IN GHANA
3.0 MATERIALS AND METHODS
3.1 STUDY AREA
3.1.1 SAMPLING SITES
3.1.2 SAMPLING
3.1 3 SAMPLE PREPARATION
3.1.4 MEASUREMENT OF pH, CONDUCTIVITY AND TDS
3.2 ANALYSES OF SAMPLES
3.2.1 DIGESTION PROCEDURE FOR WATER
3.2.2 DIGESTION PROCEDURE FOR SEDIMENT
3.4 CONTAMINATION FACTOR
3.3 STATISTICAL ANALYSIS
4.0 RESULTS
4.1 QUALITY OF LEACHATE FROM LANDFILL
4.2 QUALITY OF RIVER DENSU UPSTREAM
4.3 QUALITY OF RIVER DENSU AT LEACHATE ENTRY POINT
4.4 QUALITY OF RIVER DENSU DOWNSTREAM
4.5 PHYSICAL PARAMETERS OF RIVER DENSU
5.0 DISCUSSION
5.1 QUALITY OF RIVER DENSU UPSTREAM
5.2 QUALITY OF LEACHATE.
5.3 QUALITY OF RIVER DENSU DOWNSTREAM
6.0 CONCLUSION
6.1 RECOMMENDATIONS
Research Objectives and Core Themes
This thesis aims to assess the levels of specific heavy metals (Lead, Cadmium, Mercury, and Arsenic) in the Densu River to evaluate the impact of leachate discharge from a decommissioned landfill on the water quality, particularly for its use as a drinking water source.
- Analysis of heavy metal concentrations in landfill leachate.
- Evaluation of water and sediment quality at the point of leachate entry into the Densu River.
- Measurement of heavy metal levels at various distances upstream and downstream from the discharge point.
- Comparison of recorded heavy metal concentrations with established World Health Organization (WHO) and international safety guidelines.
Excerpt from the Book
2.6 HEAVY METALS
Heavy metals are chemical elements with a specific gravity at least 5 times that of water. The specific gravity of water is 1 at 4°C. Specific gravity is a measure of density of a given amount of a solid substance when it is compared to an equal amount of water. Some well-known toxic metals with a specific gravity 5 or more times that of water are cadmium (8.65), iron (7.9), lead (11.34), and mercury (13.546) (Lide, 1992).
In small quantities, certain heavy metals are nutritionally essential for a healthy life. Some of these elements (eg, iron, copper, manganese, and zinc) or some forms of them are commonly found naturally in foodstuffs, fruits and vegetables, and in commercially available multivitamin products. Diagnostic medical applications include direct injection of gallium during radiological procedures, dosing with chromium in parenteral nutrition mixtures, and the use of lead as a radiation shield around x-ray equipment (Roberts, 1999). Heavy metals are also common in industrial applications.
Heavy metals become toxic when they are not metabolized by the body and accumulate in the soft tissues. They may enter the human body via food, water, air, or absorption through the skin in agriculture, manufacturing, pharmaceutical, industrial, or residential settings. Industrial exposure is common in adults and ingestion the most common route in children (Roberts, 1999). Children may develop toxic levels from normal hand-to-mouth activity (ie, coming in contact with contaminated soil or eating objects that are not food such as dirt or paint chips). Less common routes of exposure include a radiological procedure, inappropriate dosing or monitoring during intravenous (parenteral) nutrition, a broken thermometer or a suicide or homicide attempt (Lupton, 1985; Smith, 1997).
Summary of Chapters
1.0 INTRODUCTION: This chapter highlights the importance of the Densu River as a water resource and identifies the challenge of increasing pollution from urbanization and landfill leachate.
2.0 LITERATURE REVIEW: This section provides an overview of water quality indicators, both physical and chemical, and details the toxicological and environmental profiles of arsenic, lead, mercury, and cadmium.
3.0 MATERIALS AND METHODS: This chapter outlines the study area, sampling strategy for water and sediments, and the analytical procedures used, including atomic absorption spectrometry, to determine heavy metal concentrations.
4.0 RESULTS: This section presents the empirical data regarding heavy metal concentrations found in leachate, upstream, at the entry point, and downstream of the Densu River, including physical parameters.
5.0 DISCUSSION: This chapter interprets the findings, comparing observed levels with regulatory standards and discussing the implications of leachate contamination on the ecosystem and human health.
6.0 CONCLUSION: This concluding chapter summarizes the study's findings regarding heavy metal contamination and provides actionable recommendations for monitoring and sanitation education.
Keywords
Densu River, heavy metals, leachate, landfill, water quality, arsenic, lead, mercury, cadmium, atomic absorption spectrometry, sediment, pollution, environmental contamination, human health, Ghana
Frequently Asked Questions
What is the primary objective of this research?
The primary goal is to assess the level of lead, cadmium, mercury, and arsenic in the Densu River to ascertain its water quality in relation to leachate discharge from a nearby decommissioned landfill.
Which pollutants are primarily investigated in this study?
The study focuses on four specific heavy metals categorized as hazardous: Arsenic (As), Lead (Pb), Mercury (Hg), and Cadmium (Cd).
What scientific methodology was employed?
The study utilized field sampling of water and sediment at five specific sites, followed by laboratory analysis using Atomic Absorption Spectrometry to measure metal concentrations, alongside the calculation of contamination factors.
How does landfill leachate affect the Densu River?
The research demonstrates that landfill leachate introduces high concentrations of toxic heavy metals into the river, significantly impacting water quality, particularly at the discharge point and nearby downstream areas used by communities.
Are the heavy metal levels in the river safe for drinking?
The study found that while some metals are within limits upstream, concentrations—particularly of lead—frequently exceed international safety guidelines (such as those from the WHO) in areas affected by leachate discharge.
Why is the Oblogo landfill site considered a critical factor in this study?
The Oblogo landfill is a decommissioned waste disposal site that is situated near the river; the study identifies it as the source of leachate that currently degrades the quality of the Densu River.
What were the specific findings regarding Lead?
Lead levels downstream were found to significantly exceed the WHO limit of 0.01 mg/l, posing a persistent health risk to downstream communities who rely on the river for domestic use.
How do sediments interact with heavy metals in the river?
The study notes that heavy metal concentrations are generally higher in sediments than in the overlying water, as sediments act as a major depository for metals, holding them in the system.
- Quote paper
- Anonym (Author), 2012, Assessment of Heavy Metal Contamination of the Densu River, Weja from Leachate, Munich, GRIN Verlag, https://www.grin.com/document/508368
