COMPARATIVE ANALYSIS OF HEAVY METALS IN BRASSICA OLERACEA FROM KENYATTA MARKET, NAIROBI AND KAGOCHI, KARATINA

ABSTRACT

Vegetables has been an integral part of day to day diet for so many people in Kenya. It is used in 

the form of raw fruits, dried, powdered or cooked vegetables. This is a research that addresses this 

way of living to act as a precaution towards making the food healthier. It is with a significant concentration in Kenyatta market than Kagochi while chromium’s level was higher in Kagochi 

compared to Kenyatta market.

From the above figures of heavy metals, it was concluded that they are beyond the permissible 

levels instituted by FAO/WHO/EU which stands at 0.3ppm for lead and 1.3ppm for chromium 

(Narain & Rajastan, 2011)

KEY WORDS: Heavy metals, Kales, Permissible levels, Phytoaccumulation, AAS 

concern that we need to highlight the effect of environmental pollution on the well-being of 

agricultural consumption, and this project is an eye opener towards that. Most pollutants are 

considered to be harmful to the biosphere but not much interest has been given to heavy metals as 

one. This project focuses on the phytoaccumulation of these heavy metals and ascertain their levels 

in different samples collected from Kenyatta market, Nairobi and Kagochi, Karatina.

Used an experimental design in that, two samples from spread-apart places were collected from 

Kenyatta market, Nairobi and two-spread apart places in Kagochi, Karatina with respect to their 

source. This was later subjected to analytical techniques carried out at the Karatina University 

Laboratories. Prepared in the chemistry laboratory at Karatina University by a process called wet 

digestion. The products of the digestion process of all the samples provided were then taken to the 

AAS room for the analysis of heavy metals and the readout containing the heavy metals 

concentration was displayed on the computer and a printout obtained for data analysis. The data 

was analyzed using Microsoft excel to the mean and standard error of the mean was subjected to 

statistical test of significance using ANOVA (p=0.05).

From the analysis of the digestion of the samples obtained from the sample areas, it was found that 

there is no apparent pollution of nickel and arsenic. However, the levels of lead and chromium was 

found to be higher clocking at 2.7779ppm and 5.6783ppm respectively for the samples collected 

from Kenyatta market. Those from Kagochi were 1.4470ppm and 12.6607ppm of lead and 

chromium respectively. Statistically, their presence differs significantly with lead marking a higher .

Table of Content

-DECLARATION........................................................................................................................... ii

ACKNOWLEDGEMENT.............................................................................................................iii

LIST OF TABLES................................................................................................................. vii

ACRONYMS AND ABBREVIATIONS............................................................................. viii

ABSTRACT ............................................................................................................................ x

CHAPTER ONE ......................................................................................................................... 1

1.0 INTRODUCTION ............................................................................................................... 1

1.1 BACKGROUND INFORMATION .................................................................................... 1

1.2 PROBLEM STATEMENT.................................................................................................. 2

1.3 JUSTIFICATION ................................................................................................................ 2

1.4 OBJECTIVES...................................................................................................................... 3

General objective..................................................................................................................... 3

Specific objectives................................................................................................................... 3

1.5 HYPOTHESIS ..................................................................................................................... 3

1.6 Limitation of the study......................................................................................................... 4

CHAPTER TWO......................................................................................................................... 5

2.0 LITERATURE REVIEW .................................................................................................... 5

2.1 INTRODUCTION .................................................................................................................... 5

2.2 THE EFFECTS OF SELECTED METALS TO THE ENVIRONMENT .......................... 6

2.2.0 CADMIUM................................................................................................................. 6

2.2.1 CHROMIUM .............................................................................................................. 7

2.2.2 LEAD.......................................................................................................................... 7

2.2.3 MERCURY................................................................................................................. 8

2.2.4 NICKEL...................................................................................................................... 9

2.2.5 ARSENIC ................................................................................................................... 9

2.3 MECHANISM OF TOXICITY OF DIFFERENT HEAVY METALS ............................ 10

2.3.0 LEAD........................................................................................................................ 10

Mechanism............................................................................................................................. 10

2.3.1 MECURY ................................................................................................................. 11

Mechanism............................................................................................................................. 11

2.3.2 CADMIUM............................................................................................................... 12

Mechanism............................................................................................................................. 12

2.3.3 CHROMIUM ............................................................................................................ 12

Mechanism............................................................................................................................. 13

2.4 KALES............................................................................................................................... 14

CHAPTER THREE................................................................................................................... 17

3.0 METHODOLOGY ................................................................................................................. 17

3.1 APPARATUS AND MATERIALS........................................................................................ 17

ANALYTICAL INSTRUMENTS..................................................................................... 17

3.2 SAMPLE PREPARATION............................................................................................. 18

3.3 REASEARCH DESIGN......................................................................................................... 18

3.4 STUDY AREA .................................................................................................................. 18

3.5 SAMPLING METHODS and sample aquisition.................................................................... 19

3.6 THE ANALYSIS OF THE HEAVY MEATALS IN ALL THE SAMPLES ........................ 19

3.6.1 THE WET/ACID ASHING PROCEDURE ON THE SAMPLES .............................. 19

3.6.2 AAS ANALYSIS ......................................................................................................... 20

3.6.3 Principle........................................................................................................................ 20

3.6.4 Instrumentation............................................................................................................. 20

3.7 DATA COLLECTION AND TOOLS.................................................................................... 21

3.7.0 PROCEDURE FOR WET ASHING ........................................................................ 21

3.7.1 Standards preparation................................................................................................ 21

3.8 DATA ANALYSIS............................................................................................................ 22

CHAPTER FOUR..................................................................................................................... 23

4.0 RESULTS AND DISCUSSION........................................................................................ 23

4.1 Statistical analysis of variance of samples from sampling areas in Kenyatta market and 

Kagochi......................................................................................................................................... 25

4.2 DISCUSSION.................................................................................................................... 27

4.2.0 Lead contamination................................................................................................... 27

4.2.1 Chromium contamination ......................................................................................... 28

4.2.2 Arsenic and Nickel contamination............................................................................ 28

CHAPTER FIVE....................................................................................................................... 29

5.0 CONCLUSION AND RECOMMENDATION...................................................................... 29

5.1 Conclusion .............................................................................................................................. 29

5.2 Recommendation .................................................................................................................... 29