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Heavy metal and nutrient loading of River Rwizi by effluents from Mbarara Municipality, Western Uganda

  • January 2014
Authors:
Moses Egor at Busitema University (BSU)
Moses Egor
Jolocam Mbabazi
Jolocam Mbabazi
Jolocam Mbabazi
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Muhammad Ntale at Makerere University
Muhammad Ntale
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Abstract and Figures

This study, carried out in the wet annual April seasons during the period 2010-2011, was geared towards the quantification of heavy metal and nutrient levels in the surface water of River Rwizi, the main Mbarara municipal drainage system. The effect of Mbarara municipal effluents on heavy metal and nutrient (phosphate, nitrite, nitrate and ammonium) loading of River Rwizi was investigated along with the changes in some basic water quality parameters, i.e., pH, conductivity and hardness. The filtered water samples were digested with a perchloric acid/nitric acid/hydrochloric acid mixture. Total heavy metals Cu, Zn, Cd and Pb were determined by flame atomic absorption spectrophotometry. Nutrients were determined by standard Wagtech methods. The results showed that there was a significant difference in concentration of lead (p = 0.047) and zinc (p = 0.018) between 2010 and 2011, with average concentrations being higher downstream. The concentrations of lead and cadmium were much higher than the WHO guideline values in drinking water (0.01 μg ml-1 and 0.003 μg ml-1, respectively). There was no significant difference in concentration of cadmium in 2010 along River Rwizi around Mbarara Township (p = 0.180). Nutrient loading in the domestic water source also indicated a gradual annual increase - hence a call for early pollution control measures by the relevant authorities.
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International Journal of Chemistry and Materials Research, 2014, 2(5): 36-47
36
HEAVY METAL AND NUTRIENT LOADING OF RIVER RWIZI BY
EFFLUENTS FROM MBARARA MUNICIPALITY, WESTERN UGANDA
Moses Egor
Department of Chemistry, Busitema University, Tororo, Uganda
Jolocam Mbabazi
Department of Chemistry, Makerere University, Kampala, Uganda
Muhammad Ntale
Department of Chemistry, Makerere University, Kampala, Uganda
ABSTRACT
This study, carried out in the wet annual April seasons during the period 2010-2011, was geared
towards the quantification of heavy metal and nutrient levels in the surface water of River Rwizi,
the main Mbarara municipal drainage system. The effect of Mbarara municipal effluents on heavy
metal and nutrient (phosphate, nitrite, nitrate and ammonium) loading of River Rwizi was
investigated along with the changes in some basic water quality parameters, i.e., pH, conductivity
and hardness. The filtered water samples were digested with a perchloric acid/nitric
acid/hydrochloric acid mixture. Total heavy metals Cu, Zn, Cd and Pb were determined by flame
atomic absorption spectrophotometry. Nutrients were determined by standard Wagtech methods.
The results showed that there was a significant difference in concentration of lead (p = 0.047) and
zinc (p = 0.018) between 2010 and 2011, with average concentrations being higher downstream.
The concentrations of lead and cadmium were much higher than the WHO guideline values in
drinking water (0.01 μg ml-1 and 0.003 μg ml-1, respectively). There was no significant difference in
concentration of cadmium in 2010 along River Rwizi around Mbarara Township (p = 0.180).
Nutrient loading in the domestic water source also indicated a gradual annual increase - hence a
call for early pollution control measures by the relevant authorities.
© 2014 Pak Publishing Group. All Rights Reserved.
Keywords: Heavy metals, Nutrients, Drinking water, River rwizi, Mbarara municipality, Uganda.
Contribution/ Originality
This study documents an early warning to the relevant policy makers in the country as to the
rapidly growing urban population and the attendant domestic water problems leading to an ill-
health population. This would in turn lead to undue annual medical expenditures that drain heavily
on the national financial resources.
International Journal of Chemistry and Materials
Research
journal homepage: http://pakinsight.com/?ic=journal&journal=64
International Journal of Chemistry and Materials Research, 2014, 2(5): 36-47
37
1. INTRODUCTION
The population of Mbarara Municipality has more than doubled since the 1970s, currently
estimated to stand at 83,700 [1]. As the population increases, so do the domestic and industrial
activities, leading to increased volumes of wastewater as well as anthropogenic pollution. Mbarara
Municipality draws its piped water from River Rwizi and despite the purification processes, some
pollutants such as heavy metals remain in the final running water. Some of the poor people even
draw water from the river banks and use it directly for domestic use. The water in this stream has a
permanent dirty-brown colour and carries a not too pleasant smell. It is feared that the increasing
volume of untreated municipal effluent discharge finds its way, directly or indirectly, into the river.
Knowledge of the current state of the quality of water at specific points in the town is therefore
essential, especially with regard to the soluble and invisible inorganic pollutants, notably heavy, or
trace metals. Some of the heavy metals most commonly linked to human poisoning are lead,
copper, zinc and cadmium. There is increasing evidence that lead poisoning causes permanent
neurological, developmental [2] and behavioral disorders, particularly in children [3] and it poisons
thousands of people in urban areas annually [4].
The leaching of the heavy metals from the drainage systems into the river may cause a serious
deterioration of its water quality [5, 6] and a probable poisoning of the aquatic life [7] such as the
marketed mud fish caught from the banks of the river. Consequently, there was need to initiate
systematic studies to evaluate the levels of the more likely heavy metal pollutants Cu, Cd, Zn and
Pb in the river water system in an effort to establish the full extent of the problem. The results from
the study are considered to be an indirect but confirmatory indicator of pollution in the waterway,
from which Mbarara Municipality draws its water for domestic and industrial use yet there is
limited information on the state of purity of this water in terms of metal and nutrient loading. Such
studies may prove of great value in matters of public health, and help instigate the putting of early
counter-measures in place [8].
The general objective of this study was to assess the extent of heavy metal concentration as
well as the nutrient levels of the waters of River Rwizi, with the specific objectives of determining
the physical water parameters; pH, hardness and electrolytic conductivity of River Rwizi water as
indicators of pollution due to the Mbarara municipal settlements and other human activities along
the river valley, as well as the concentrations of lead, copper, cadmium and zinc in River Rwizi
waters before and after flowing through Mbarara Municipality. It was also deemed necessary to
measure the levels of nutrients, i.e., nitrite, nitrate, ammonium and phosphate in the waters of River
Rwizi before and after drainage through Mbarara Township. It is also hoped that the data herein
provided on the trace metal loading of River Rwizi shall be used as a benchmark for decision-
making on pollution control. The results of this study would also enrich the existing database on
the extent of heavy metal pollution of surface water in Uganda.
2. EXPERIMENTAL
2.1. Study Area
Mbarara Municipality is the largest urban centre in Western Uganda with a population of about
83,700 people [1], one of the fastest growing towns in Uganda. It is located approximately
International Journal of Chemistry and Materials Research, 2014, 2(5): 36-47
38
270 kilometres, southwest of Kampala, Uganda's capital city. The coordinates of the municipality
are 00° 36’S, 30° 36’ERiver Rwizi is a tributary of Lake Victoria transecting five districts of
Mbarara, Bushenyi, Ntungamo, Isingiro and Kiruhuura. It is the source of domestic water supply
and drainage system of Mbarara Municipality [9].
2.2. Water Sampling
Sampling was done twice, in March 2010 and April 2011. Surface water samples were
collected from twelve different locations. Four samples from sites 2 km upstream, labelled U1, U2,
U3 and U4 (figure 1); in the town area (mid-town, labelled M1, M2, M3, M4) and 2 km
downstream (D1, D2, D3, D4), the sampling sites were 200 m apart along River Rwizi on the
southern outskirts of Mbarara Municipality (Figure 1). The samples were collected using 10-litre
plastic containers. At each sampling site the containers were cleaned with detergent solution,
rinsed several times with dilute nitric acid solution to avoid metal contamination, and finally rinsed
with distilled deionised water, before use. The collected water was filtered within a few hours of
sampling, transferred to 5-litre polythene containers and stored at room temperature (25oC) until
analysis.
2.3. Analytical Procedures
All the chemicals named and used in this study, including the deionised water, were supplied
by British Drug Houses (BDH), Wagtech and were of analytical reagent grade (AnalaR).
2.3.1. Determination of Heavy Metals Cu, Zn, Pb and Cd
These were investigated using different methods for comparison and completeness. Water
samples were digested using the following methods:
a) The filtered water samples were analysed directly [10] for copper, zinc, cadmium and
lead, using a flame atomic absorption spectrophotometer, FAAS (Perkin_Elmer GmbH,
Uberlingen, Germany, Model 2380).
b) To 500 ml of the filtered water samples was added 10 ml of concentrated hydrochloric
acid (analytical reagent grade) and evaporated under gentle heat to 50 ml. The concentrate
was quantitatively transferred to a 100 ml volumetric flask and made up to the mark with
distilled deionised water.
c) 500 ml of the water samples from each site were evaporated to near dryness. To the
residue, concentrated nitric acid (10 ml) and hydrochloric acid (4 ml) were added. This
was then be evaporated to near dryness. The final residue was reconstituted with 2 ml of
2M hydrochloric acid, transferred to a 25 ml volumetric flask and made up to the mark
with distilled water.
d) 1 litre of the water samples from each site was evaporated to dryness. To the residue, the
triple acid system, viz. concentrated nitric acid (10 ml), perchloric acid (2 ml) and
hydrofluoric acid (4 ml), was added. Then this was reheated to dryness. The final residue
was reconstituted in 2 ml of hydrochloric acid (2M), transferred to a 25 ml volumetric
flask and made up to the mark with distilled, deionised water.
International Journal of Chemistry and Materials Research, 2014, 2(5): 36-47
39
The resultant aqueous solutions were analysed for each of the heavy metals Zn, Cu, Cd and Pb
using a Flame Atomic Absorption Spectrophotometer, FAAS (Perkin-Elmer GmbH, Uberlingen,
Germany, Model 2380). In each case a read-out from the screen was taken as the concentration of
the selected metals.
2.3.2. Determination of Nutrient Loading
Nutrients were determined by a standard Wagtech procedure using the CP1000 Physico-
Chemical Kit as described in the Wagtech manual, that has been specifically designed for testing a
wide range of physical and chemical water quality parameters, including phosphate, nitrate and
nitrite. The kit contained a carefully selected range of high quality digital instruments that made it
suitable for field work. The kit was used in conjunction with the Photometer 7100, capable of
analysing over 40 different chemical parameters.
The total hardness in the water was determined by EDTA titration as follows. 50 ml of sample
was put into a 250 ml conical flask followed by 1 ml of ammonia buffer solution of pH 10 and two
drops of Eriochrome black T indicator. The mixture was titrated with 0.01M EDTA solution until
the colour changed from red- wine to blue. Hardness was subsequently calculated using the
formula [11]:
Hardness 

2.3.3. Statistical Analysis
The results were subjected to one way ANOVA, Kruskal-Wallis test, independent samples t-
test or Mann-Whitney U-test, using SPSS version 17 and Minitab version 14 statistical software
with confidence interval of 95%.
3. RESULTS AND DISCUSSION
Tables 1and 2 show the mean total of heavy metal levels (±SD) at various sites along River
Rwizi during the wet seasons of 2010 through 2011, as analysed using the four sample pre-
treatment procedures (a), (b), (c) and (d). In general, the total concentration, in μg ml−1, of the
metals in all the samples decreased in the order: Zn > Pb > Cu >> Cd.
3.1. Zinc
Comparison of Zn concentration upstream, in mid-town area and downstream in 2010 using
Kruskal-Wallis test indicated a significant difference (p = 0.018). In 2011, one way ANOVA of
zinc levels in the different locations also indicated a significant difference (p = 0.000). Comparison
of Zn concentration upstream, mid-town and downstream in 2010 versus 2011 using independent
samples t-test and Mann-Whitney U-test indicated no significant difference (t = 0.399, DF = 6, p =
0.767), (t = -0.135, DF = 6, p = 0.897), (U = 6.5, n = 4, p = 0.663), respectively. There was a
general increase in the concentration of zinc along River Rwizi around Mbarara town, with average
concentration highest in the town area. Zinc-coated corrugated iron sheets, the commonest roofing
material in the country, on corrosion release considerable amounts of zinc as its oxide or sulphide
into the soil [12], the leaching of which concentrates the metal in the water body via surface run-off
International Journal of Chemistry and Materials Research, 2014, 2(5): 36-47
40
and other processes. High demand for wall and roof paints, most of which are zinc-based, adds to
the problem [13]. Zinc is also extensively used in the manufacture of dry cells that are commonly
used as chemical sources of electrical energy.
3.2. Lead
Comparison of Pb concentration upstream, mid-town and downstream for 2010 and 2011 using
one way ANOVA indicated a significant differences (F = 4.369, DF = 11, p = 0.047) and (F =
7.105, DF = 11, p = 0.014) respectively, with figures notably higher in the town area and
downstream. When the amount of Pb upstream in 2010 and 2011 were compared using
independent samples t test, there was no significant difference (t = 0.177, DF = 6, p = 0.865). The
differences in mid-town (t = .005, DF = 6, p = 0.996) and downstream (t = -0.336, DF = 6, p =
0.748) were not significant at 95% confidence interval. Average concentration of 1.321 μg ml−1
upstream, 0.75 µg ml-1 in the town area and 1.5 μg ml−1 downstream, showed an average increase
in lead downstream. The average lead level in the river waters was found to be 0.5–2.0 μg ml−1.
Continued use of lead-based paints and their inappropriate disposal [14]; car washing and
emptying of old lead-acid accumulators regularly takes place directly along the streams and
channels leading to the river. The lower levels lead in the town area could as a result of adsorption,
chelation and sedimentation, making it less available in the filtered water, but rather in the
sediment.
Mn+(aq) + z(High RMM organic anions) [M(organic anion)z]n+ Sediment
Generally, the concentration of lead was highest downstream, which also showed an average
increase from 2010-2011, while remaining fairly constant in town area and downstream.
3.3. Copper
The concentration of Cu upstream, mid-town and downstream for 2010 and 2011 were
compared using Kruskal-Wallis test. The tests showed a significant difference (H = 9.33, DF = 2, p
= 0.009) in 2010 and (H = 8.80, DF = 2, p = 0.012) in 2011. Comparison of Cu in upstream for
2010 versus 2011 using Mann-Whitney U test gave no significant difference (U = 6.5, n = 4, p =
0.659), while in mid-town for 2010 and 2011 using Mann-Whitney U- test, Cu levels showed no
significant difference (U = 6.0, n = 4, p = 0.538). The levels of Cu were relatively constant
upstream, but steadily increased in town area and downstream in 2011 (Tables 1 and 2).
There was a visible increase in concentration going downstream with average concentrations
of 0.0437 μg ml−1, 0.0699 μg ml−1and 0.13986 μg ml−1 going downstream. The increased usage of
imported electrical copper wire and cables in the town leaves on a daily basis a considerable
amount of waste metal in the form of bits, choppings and cut-offs. Metallic copper washed down in
the run-offs subsequently dissolves in the fluctuating acidities and alkalinities of the effluent.
3.4. Cadmium
The amount of Cd was fairly constant upstream and in the town area (with the unusually high
level of up to 0,044 µg ml-1 in site D3). An increase was noticed downstream over the two years.
Comparison of Cd in upstream, mid-town and downstream for 2010 using Kruskal-Wallis test
International Journal of Chemistry and Materials Research, 2014, 2(5): 36-47
41
indicated no significant difference (p = 0.180). The concentration of Cd is higher than the WHO
guideline value in drinking water (0.003 μg ml−1), which poses a threat to living organisms using
this water directly. The relatively high level of cadmium in the municipality effluent waters may be
attributable to the activities of small-scale metal works in the town, which process even scrap metal
and run their untreated effluent directly into the drainage channels [15]. Also increased use and
poor disposal of rechargeable batteries [16], cathode ray tubes of colour TVs and photocopier
drums poorly disposed, corrode and get washed down the river [17]. Cadmium is widely used in
paints [18]; and owing to the booming construction in the town, there is a considerable release of
the metal into the environment via the associated painting and face-lifting of buildings.
3.5. Nutrients
Phosphate was the most predominant of the nutrients considered, followed by nitrates and
fluctuating low amounts of ammonium and nitrite nutrients (Figures 2 &3). The elevated nutrient
level is due to sewage and domestic wastewater as well as effluents from food processing factories
(milk and bakeries) and from runoffs from surrounding farmland where fertilizers are used in
banana plantations. Too much nutrient in domestic water might encourage the growth of toxic
bacteria [19]. The high amount of nitrogen nutrients (ammonium, nitrates and nitrites) is attributed
to a number of cattle farms at several points along the river, notably Mbarara High School farm
among others. Excreta from these animals are an obvious source of nitrogen that is directly washed
down to the river. At the point where treated sewage is channelled back to the river, we also expect
a considerable amount of nitrogen fertilizer loading into river water. Surface runoff from the town
and surrounding villages contains raw sewage, wastewater and fertilizers from gardens that
contribute to nitrogen loading [20].
Most nitrogen in River Rwizi water occurs as nitrates, whose concentration also increased
downstream throughout the sampling period (Figures 2 and 3), giving no significant concentration
difference in the sampling sites in 2010 (p = 0.062) and a significant difference in 2011 (p = 0.022).
There was also a slight increase in nitrate levels in 2011 (0.233-0.577 µg ml-1) as compared to 2010
(0.119-0.54µg ml-1) (Figure 2). A slight decrease in nitrite levels can be attributed to biochemical
(bacterial) conversion to nitrates, evidenced by increase in nitrate levels. In all sites, the levels of
nitrites were higher in 2011 (Figure 3).
These nutrients cause an increase in production and biomass of phytoplankton, attached algae
and macrophytes [19], shift in habitat characteristics due to change in assemblage of aquatic plants,
replacement of desirable fish by less desirable species, production of toxins by certain algae [21],
deoxygenation of water, especially after collapse of algal blooms [22]. Loss of recreational use of
water due to slime, weed infestation and noxious odour from decaying algae is an impediment to
navigation due to dense weed growth [23].
The main source of phosphate could be raw sewage and wastewater from that drain in the
river. Increased use of detergents as a result of relative hardness detected could accelerate the
problem. Phosphorus nutrient pollution causes enormous blooms of the algae, a form of
cyanobacteria, which can produce neurotoxins and hepatotoxins [24].
International Journal of Chemistry and Materials Research, 2014, 2(5): 36-47
42
3.6. Hardness, ph and Conductivity
Hardness of River Rwizi water remained fairly unchanged over the study period, the water not
so heavily loaded with Ca and Mg ions, but tables 3 and 4 show significantly high quantities of
these ions. There are no limestone rocks in Mbarara area, but possibly runoffs from areas as far as
Bunyaruguru, with plenty of calcium rocks, contribute to the observed relative hardness in the
water.
The pH of the filtered water samples at 25°C was in the range 6.6 - 6.8 (Tables 3 and 4),
indicative of the relative neutrality, despite the direct seepage of the untreated municipal effluent,
of the river waters. The slight reduction in pH can be attributed to the increase in the levels of
metallic cations discussed earlier.
4. CONCLUSIONS
Our results show that the levels of heavy metals in the river water are on the rise, which is
reflective of the growing anthropogenic pollution problem in Mbarara Municipality. This poses a
big threat to the only reliable source of fresh water for domestic and industrial use. It is therefore
imperative upon the relevant municipal authorities to stress the need for treatment of effluent at the
source before release into the environment. In addition, tougher laws should be put in place as a
deterrent against direct channelling of industrial effluents and dumping of wastes into River Rwizi.
Nutrient levels are rising, with phosphates being the most predominant. Nitrogenous nutrients
occur mainly as nitrates and a combination of all these seem to be the sole cause of the dirty-brown
appearance of the water and the subsequent growth of algae observed at stagnant points along the
river.
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FIGURES
Figure-1.Map of Uganda showing location of Mbarara Municipality and sampling sites on River
Rwizi
(Source: Google maps/Uganda)
International Journal of Chemistry and Materials Research, 2014, 2(5): 36-47
45
Figure-2.Relative nutrient levels in 2010
Source: (this work)
Figure-3.Relative nutrient levels in 2011
Source: (this work)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
U1 U2 U3 U4 M1 M2 M3 M4 D1 D2 D3 D4
Cocentration (µg ml-1)
Distance downstream
Ammonia-N
Nitrite-N
Nitrate-N
Phosphate
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
U1 U2 U3 U4 M1 M2 M3 M4 D1 D2 D3 D4
Concentration (µg ml-1)
Distance downstream
Ammonia-N
Nitrite-N
Nitrate-N
Phosphate
International Journal of Chemistry and Materials Research, 2014, 2(5): 36-47
46
TABLES
Table-1. Mean total heavy metal levels in River Rwizi water in 2010
April , 2010
Concentration (µg ml-1)
Sampling site
Zn
Cu
Cd
Pb
U1
1.469±0.001
0.037±0.003
0.029±0.004
1.428±0.004
U2
1.704±0.004
0.068±0.001
0.029±0.005
1.428±0.006
U3
1.453±0.004
0.036±0.003
0.029±0.003
1.283±0.006
U4
1.353±0.003
0.034±0.005
0.029±0.006
1.142±0.008
M1
2.503±0.003
0.069±0.005
0.029±0.007
0.552±0.005
M2
2.587±0.003
0.069±0.007
0.029±0.007
0.716±0.005
M3
2.394±0.006
0.107±0.006
0.044±0.006
0.545±0.006
M4
2.630±0.006
0.104±0.006
0.029±0.005
1.421±0.005
D1
2.017±0.005
0.139±0.007
0.029±0.005
1.427±0.005
D2
0.777±0.005
0.105±0.007
0.029±0.006
1.031±0.005
D3
1.855±0.005
0.139±0.004
0.029±0.005
2.058±0.006
D4
2.066±0.005
0.138±0.003
0.043±0.004
1.573±0.002
Average
1.901±0.007
0.087±0.00
0.0314±0.006
1.217±0.006
Source: (this work)
Table-2. Mean total heavy metal levels in River Rwizi waters in 2011
April, 2011
Concentration (µg ml-1)
Sampling site
Zn
Cu
Cd
Pb
U1
1.447±0.002
0.035±0.004
0.029±0.002
1.429±0.005
U2
1.605±0.004
0.068±0.003
0.029±0.003
1.423±0.006
U3
1.447±0.004
0.036±0.004
0.029±0.002
1.218±0.007
U4
1.369±0.006
0.703±0.005
0.029±0.002
1.140±0.006
M1
2.546±0.003
0.069±0.001
0.029±0.004
0.545±0.002
M2
2.535±0.005
0.069±0.002
0.029±0.004
0.716±0.003
M3
2.408±0.003
0.120±0.002
0.044±0.004
0.545±0.003
M4
2.665±0.005
0.126±0.003
0.029±0.003
1.422±0.004
D1
2.060±0.004
0.191±0.004
0.029±0.004
1.427±0.005
D2
1.689±0.004
0.099±0.007
0.029±0.004
1.385±0.004
D3
1.855±0.006
0.179±0.006
0.029±0.006
2.005±0.005
D4
2.269±0.008
0.132±0.005
0.029±0.001
1.615±0.005
Average
1.991±0.007
0.096±0.005
0.030±0.001
1.239±0.004
Source: (this work)
Table-3. Hardness, pH and conductivity of R. Rwizi water in 2010
Sample
Hardness
(mg/L as CaCO3)
pH
Conductivity (Ω-1cm-1)
U1
48
6.8
105.1
U2
48
6.8
107.4
U3
47
6.8
106.5
U4
44
6.8
105.7
M1
48
6.7
105.7
M2
46
6.7
104.2
M3
46
6.6
105.9
M4
46
6.7
106.7
D1
52
6.7
108.8
D2
46
6.6
109.5
D3
46
6.6
110.1
D4
49
6.6
107.6
International Journal of Chemistry and Materials Research, 2014, 2(5): 36-47
47
Table-4. Hardness, pH and conductivity of R. Rwizi water in 2011
Sample
Hardness
(mg/L as CaCO3)
pH
Conductivity (Ω-
1cm-1)
U1
47
6.8
106.1
U2
43
6.8
107.8
U3
46
6.7
105.6
U4
44
6.8
105.6
M1
49
6.7
106.6
M2
45
6.7
105.5
M3
44
6.6
105.7
M4
48
6.6
106.9
D1
53
6.7
109.3
D2
48
6.6
109.1
D3
55
6.6
109.1
D4
47
6.7
109.3
Source: (this work)
... For example, the River Nyamwamba-Rukoki in Uganda which originates from the Rwenzori Mountain (Mwesigye and Tumwebaze 2017) deposits 30 tons of Cu and 13 kg of Cd annually into Lake George from Kilembe mines (Hartwig et al., 2005). Rwizi River in southwestern Uganda, which has been cited to be polluted with trace metals (Egor et al., 2014;Ojok et al., 2017;Semwanga et al., 2020), drains into lakes Mburo, Kachera, Nakivale, and Victoria. ...
... Surface water pH of the downstream sites was significantly lower compared to the upstream sites. Earlier studies conducted on the Rwizi River in Uganda had similar pH ranges from 6 to 7 in the downstream areas (Egor et al., 2014;Semwanga et al., 2020). The low pH upstream could be attributed to leaching of hydrogen ions from the acidic soils of the riverbed and catchment (Banga, 2014). ...
... The pH range from 5.7 to 7.1 in the downstream part was perhaps influenced by influx of wastewaters from the urban catchment. The pH ranges were similar to Egor et al. (2014) and Semwanga et al. (2020) although sampling were conducted in different sites. ...
Trace metal concentrations in the abiotic and biotic components of River Rwizi ecosystem in Western Uganda, and the risks to human health
Article
Full-text available
  • Nov 2021
The distribution of metals in the Rwizi River ecosystem was investigated and human health risks were assessed. Samples of water, sediment, damselfly larvae (Ceriagrion glabrum ) and fish species (Brycinus sadleri and Barbus altianalis), were collected at six sites. In all samples the trace elements As, Al, Au, Cd, Co, Cu, Fe, Hg, Mn, Pb, Zn, were quantified. Sediment samples near the gold mine had significantly higher concentrations of Hg, Fe and Al although all the concentrations were below the probable effect concentrations (PEC). The dissolved concentrations of trace metals were within the European standards and WHO drinking water guidelines. However, Fe and Mn concentrations exceeded the standards at three sites. The damselfly larvae were good indicators of local metal pollution. The fish species accumulated metal levels in the order gills>liver>muscle for most metals except for Hg. Multiple regressions between accumulated metals in damselfly with environmental metal levels showed only for Au and Cd significant positive relationships. Relating environmental metal levels and physicochemical characteristics to the levels in the invertebrates, only for Cu and Pb significant relationships were found. With respect to the measured metals, the fish were safe for human consumption in most cases although Brycinus sadleri posed a potential health risk due to a As hazard quotient (HQ) of 2.2 that exceeded the critical value of 1. Similarly, the maximum edible risk-free quantity (Q) for As in Brycinus sadleri was 1.5 g (95 % CI), less than the minimum risk free quantity of 31.5 g. In conclusion, the river water was safe for drinking but the extraction of gold using Hg should be replaced with an environmentally friendly method or an effective wastewater treatment should be instituted. People should be cautioned from consuming Brycinus sadler i to avoid potential health hazards.
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... This deterioration has been attributed to both natural processes such as weathering of underlying crustal materials, erosion, precipitation and anthropogenic activities which are triggered by climate change, agricultural land use, industrial and sewage effluent discharge [1] [2]. Anthropogenic activities are major contributors of pollutants to surface water resources in developing countries such as Uganda, the most important being urban sewage, agriculture and industrial effluents which are well known for nutrient loading and heavy metal pollution of water bodies [3] [4] [5]. Moreover, river water resources are important in promoting human development as they serve as domestic water sources; provide water for agriculture, industries and transport. ...
... The studies in Uganda have shown that most water resources are easily contaminated due to anthropogenic activities especially in urban areas. A case in point is the deterioration of water quality of River Rwizi that has been reported over the past several years by a number of researchers [5] [7] [8]. River Rwizi originates from the hills of Buhweju District and crosses through several other districts of south western Uganda including Mbarara, Bushenyi, Sheema, Ntungamo, Kibingo, and Kiruhura among others, with various tributaries originating from different parts of the region. ...
... The river section in Mbarara Municipality is selected for this study because it has the highest proliferation of industrial establishments, and is likely to experience the serious consequences of pollution. Many studies have been conducted on the River Rwizi water with results indicating deterioration in its quality mainly attributable to anthropogenic activities in its water shed [5] [7]. ...
Spatial Variation in Physicochemical Surface Water Quality in River Rwizi, Western Uganda
Article
Full-text available
  • Dec 2019
River Rwizi originates from the Buhweju hills. It is a major source of water for the inhabitants of Mbarara Municipality and surrounding environment. In this study, spatial variation of water quality in River Rwizi section within Mbarara Municipality was determined using cluster analysis. Laboratory analysis was conducted on water samples from five sites along the river section using standard methods for: pH, EC, TSS, TDS, turbidity, temperature,total hardness, alkalinity, salinity, colour, NH3-N, SO42 − , BOD, COD, DO, Ca, Mg, Fe, and Mn. Cluster analysis grouped the study sites into slight pollution (Spencon, GBK), moderate pollution (Katete) and high pollution (BSU, Kakoba) for dry season. For rain season, order was: slight pollution (BSU, Spencon), moderate pollution (GBK) and high pollution (Kakoba, Katete), basing on similarity of water quality variables. These results show that water pollution resulted primarily from domestic waste water, agricultural runoff and industrial effluents. Thus, water from River Rwizi is not suitable for drinking in both dry and wet seasons.
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... This deterioration has been attributed to both natural processes such as weathering of underlying crustal materials, erosion, precipitation and anthropogenic activities which are triggered by climate change, agricultural land use, industrial and sewage effluent discharge [1] [2]. Anthropogenic activities are major contributors of pollutants to surface water resources in developing countries such as Uganda, the most important being urban sewage, agriculture and industrial effluents which are well known for nutrient loading and heavy metal pollution of water bodies [3] [4] [5]. Moreover, river water resources are important in promoting human development as they serve as domestic water sources; provide water for agriculture, industries and transport. ...
... The studies in Uganda have shown that most water resources are easily contaminated due to anthropogenic activities especially in urban areas. A case in point is the deterioration of water quality of River Rwizi that has been reported over the past several years by a number of researchers [5] [7] [8]. River Rwizi originates from the hills of Buhweju District and crosses through several other districts of south western Uganda including Mbarara, Bushenyi, Sheema, Ntungamo, Kibingo, and Kiruhura among others, with various tributaries originating from different parts of the region. ...
... The river section in Mbarara Municipality is selected for this study because it has the highest proliferation of industrial establishments, and is likely to experience the serious consequences of pollution. Many studies have been conducted on the River Rwizi water with results indicating deterioration in its quality mainly attributable to anthropogenic activities in its water shed [5] [7]. ...
Spatial Variation in Physicochemical Surface Water Quality in River Rwizi, Western Uganda
Article
Full-text available
  • Jan 2019
River Rwizi originates from the Buhweju hills. It is a major source of water for the inhabitants of Mbarara Municipality and surrounding environment.In this study, spatial variation of water quality in River Rwizi section within Mbarara Municipality was determined using cluster analysis. Laboratory analysis was conducted on water samples from five sites along the river section using standard methods for: pH, EC, TSS, TDS, turbidity, temperature, total hardness, alkalinity, salinity, colour, NH3-N, SO42 − , BOD, COD, DO, Ca, Mg, Fe, and Mn. Cluster analysis grouped the study sites into slight pollution (Spencon, GBK), moderate pollution (Katete) and high pollution (BSU, Kakoba) for dry season. For rain season, order was:slight pollution (BSU, Spencon), moderate pollution (GBK) and high pollution (Kakoba, Katete), basing on similarity of water quality variables. These results show that water pollution resulted primarily from domestic waste water, agricultural runoff and industrial effluents. Thus, water from River Rwizi is not suitable for drinking in both dry and wet seasons. Keywords River Rwizi, Cluster Analysis, Spatial Variation, Pollution
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... Assessment of water and wastewater is very crucial to safeguard the public health and environment. The population of Mbarara Municipality has been ris- ing rapidly from 69,400 in 2002 to 195,013 by August 2014 [1] [2]. As population increases, the domestic and industrial activities leading to increased volumes of wastewater and anthropogenic pollution also increases. ...
... As a result, the water in the River Rwizi has a dirty-brown colour with unpleasant smell. Due to the increased population and activities, more effluent discharge find their way directly or indirectly to the main river Rwizi, where poor people draw water from its banks for domestic purposes and this could cause water borne diseases to the surrounding community [1]. ...
... The study area was conducted in Mbarara Municipality (00˚36'S 30˚36'E), a fast-growing town and the largest in Western Uganda [1]. Traversing Mbarara Municipality is river Rwizi which originates from the hills of Buhweju transect- ing through districts of Mbarara, Sheema, Ntungamo, Isingiro, Kiruhura, and Bushenyi before it pours its waters into Lake Victoria via the network of Lake Mburo, Lake Kachera, Lake Nakivale and Kijanebalola among others. ...
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... Mbarara City is crossed by River Rwizi, and local people depend on its water as the only viable source, mainly for drinking, industry, irrigation, and other domestic purposes (Atwongyeire et al., 2018;Songa et al., 2015). Moreover, studies (Egor et al., 2014;Ojok et al., 2017;Walter et al., 2019) pointed out that River Rwizi water quality is deteriorating with time. However, their works were restricted on water samples, and no chemical data is available on the quality of bottom sediments for future monitoring of this valuable natural resource. ...
... Unfortunately, water-soluble metal fraction (F1) contains bioavailable metals and they can easily be transported to overlying water from sediment pore water. Egor et al. (2014) detected a closer concentration value of zinc in water samples of River Rwizi within Mbarara catchment sites which was above WHO permissible limit in drinking water (3 mg kg −1 ). Above this limit, zinc would be toxic to some plants (phytotoxic) causing chlorosis and stunting (Manahan, 2000;WHO, 2008). ...
Speciation of Selected Heavy Metals in Bottom Sediments of River Rwizi, Mbarara City, Uganda
Article
Full-text available
This research focused on chemical speciation of six heavy metals in the bottom sediments of River Rwizi in Mbarara City, Uganda. Heavy metals cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), and iron (Fe) and physicochemical parameters, namely pH, oxidation–reduction potential (ORP), and organic matter (OM), were assessed during wet and dry seasons. Sequential extraction procedure was applied to fractionate metals into six fractions: water-soluble, exchangeable, carbonate bound, Fe–Mn oxides bound, bound to organics, and residual fraction. Quantitative determination of heavy metals was carried out using flame atomic absorption spectrophotometer. Speciation results revealed that the potential mobility of heavy metals decreased from wet to dry season, and it was in the increasing order of Zn >\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$>$$\end{document} Cu >\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$>$$\end{document} Cd >\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$>$$\end{document} Pb >\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$>$$\end{document} Ni >\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$>$$\end{document} Fe, in both seasons. Higher concentrations of heavy metals were present in their immobile chemical forms than in their potentially mobile chemical forms. The total mean contents in mg kg⁻¹ (except Fe in %) of the metals were Cd: 1.63 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 0.21; Cu: 106.10 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 23.22; Ni: 38.17 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 6.07; Pb: 33.45 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 3.33; Zn: 108.34 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 30.51; Fe: 3.04 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 0.75, and Cd: 1.64 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 0.23; Cu: 111.10 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 27.36; Ni: 39.81 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 7.90; Pb: 33.98 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 3.63; Zn: 115.72 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 31.64; Fe: 3.08 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 0.75 during wet and dry seasons, respectively. The geochemical accumulation indices of Cd, Cu, Pb, and Zn showed that the bottom sediments of River Rwizi ranged from unpolluted to severe polluted sediments, which implied anthropogenic input. Other parameters measured from wet to dry season were, pH: 6.8 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 0.35 -\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$-$$\end{document} 6.21 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 0.08; ORP: 308.4 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 44.7 mV -\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$-$$\end{document} 342.1 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 39.6 mV; OM: 2.0 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 0.35% -\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$-$$\end{document} 1.4 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 0.31%. Conclusively, it was found that heavy metals (Zn, Cu, and Cd) were significantly present in their potential mobile fractions alarming that they may pose serious human and environmental problems.
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... The elevated levels of Pb at the various sites are basically due to leakage of oil and gasoline from the vehicles being washed and also as a result of increased surface runoff from agricultural farms. Egor et al., (2014) found that the average lead level in the river Rwizi waters was between 0.5-2.0μg/ml. In case of Zn, its levels were below the permissible level of 5.0 mg/L in the study rivers with the lowest value (0.010±0.00mg/L) recorded in rivers Mubuku and Rwimi while the highest value (0.076±0.003mg/L) was recorded from R. Nyamwamba, A (Nyamwamba river near the Kilembe mines headquarters and Kilembe hospital, near the former copper mining deposits). ...
... Zn is a naturally abundant element present as a common contaminant in agricultural, food wastes, manufacturing of pesticides as well as antifouling paints (Badr et al., 2009). However higher results of zinc were found by (Egor et al., 2014) in studies to determine heavy metal loading of river Rwizi Mbarara municipality. ...
HEAVY METAL POLLUTION IN THE MAIN RIVERS OF RWENZORI REGION, KASESE DISTRICT SOUTH-WESTERN UGANDA
Article
Full-text available
  • Sep 2020
Current study established heavy metal pollution of rivers Mubuku, Rwimi and Nyamwamba in Kasese district, Western Uganda. Their integrity is important because communities depend on them for water resources. No recent information is known on rivers' quality status yet traverse a densely populated area with agricultural activities and a history of copper/cobalt mining as heavy metals pose high health risks. The study was conducted from October 2019 to December 2019 and quantified levels of Cu, Zn, Pb and Co in water and fish to estimate the rivers quality. Water samples were randomly collected in sterilised bottle while fish samples were collected using non selective net method, dissected and dried to a constant mass. The total heavy metal load was determined using atomic absorption spectrophotometer. Results showed that, apart from Lead, the levels of Cu, Zn and Co in the waters were all within WHO limits except Co at one site on R. Nyamwamba with 0.233±0.009mg/L above the limit 0.05mg/L for drinking water. The overall mean for Pb was 0.030±0.006mg/L and 0.047±0.003mg/L at R. Nyamwamba, 0.053±0.003mg/L at R. Mubuku and 0.067±0.003mg/L at R. Rwimi, all above the WHO limit of 0.01mg/L. In fish tissues, Cu was within WHO limit; however, Pb and Zn were above limits (Pb, 2.0ppm; Zn, 100ppm) for fish. The average concentration for Pb was 29.05±4.85ppm, 69.23±9.25ppm and 32.33±5.93ppm at R. Nyamwamba, Rwimi and Mubuku respectively and for Zn, 115.05±8.12ppm, 117.47±8.65ppm and 118.69±8.79ppm at R. Nyamwamba, Rwimi and Mubuku respectively. Similarly, for all the three rivers, physico-chemical parameters; pH, temperature, electro-conductivity and dissolved oxygen were within the WHO limits but turbidity, 12.02±0.39NTU was above the limit of 5.0NTU. Therefore, there is need for management intervention to control further contamination of rivers with heavy metals and controlled use of water bodies as washing bays.
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... A recent print indicated that more than 21 million (51% of) Ugandans do not have access to safe drinking water [12]. In tandem with the sanitation crisis, both the physicochemical and microbiological profiles of water in some areas in Uganda have been indicated to be unfit for drinking and other purposes [13][14][15][16][17][18][19][20][21][22]. ...
Physicochemical Quality of Water from Chuho Springs, Kisoro District, Uganda
Article
Full-text available
  • Dec 2021
In the current study, water from Chuho springs used as the main water source in Kisoro municipality, Uganda were assessed for their suitability as drinking water. The temperature, turbidity, conductivity, total dissolved solids, dissolved oxygen, biological oxygen demand, total hardness, total alkalinity, calcium, magnesium, phosphates, iron, copper, arsenic, chlorides and the fluoride content of the water samples were determined. Not all the parameters met World Health Organizations’ guidelines for drinking water. Temperature, dissolved oxygen and fluorides were outside the recommended limits of 15 ℃, 10-12 mg/L and 1.5 mg/L, respectively. Further studies should assess the microbiological and sanitary profile of the springs.
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... In the recent past, Rwizi river has suffered increased anthropogenic disturbances whose impact on the quality of the water is a subject of inquiry in the region. Some information on the quality of Rwizi river is available (Atwebembeire et al., 2018(Atwebembeire et al., , 2019Egor & Mbabazi, 2014;Ojok, et al., 2017). However, previous assessments were largely based on the water chemistry and in the main river only. ...
The biological integrity of streams and channels draining into the Rwizi River system in Western Uganda
Article
Full-text available
  • Oct 2019
Rwizi River, often called the life-line river, supports over five million people in Western Uganda and is a major contributor of freshwater to Lake Victoria. Surrounded by a large and rapidly growing population, the river has suffered anthropogenic disturbances whose impact on the integrity of the system is a subject of concern. Aquatic macroinvertebrates, used globally to monitor both short- and long-term environmental conditions, were thus used to assess the biological integrity of streams and channels draining into the river system. Macroinvertebrates were sampled for six months in 2017 encompassing the wet and dry seasons using the kick net sampling method. The macroinvertebrates were identified morphologically using peer reviewed identification keys and their pollution sensitivity scored using the Tanzanian River Scoring System (TARISS). The Shannon diversity index was computed per site and related to average score per taxon (ASPT). We collected a total of 5442 macroinvertebrates belonging to 54 families dominated by Chironomidae (29.1%). Macroinvertebrate diversity increased with ASPT (r = 0.57; N = 131; P = 0.000). The water quality was generally poor and was not affected by the season (t = 1.03; df = 64; P = 0.303) though sites had different water quality (F = 11.32; df = 20; P = 0.000) attributed the degree of anthropogenic disturbance. We concluded that river Rwizi system is highly degraded and thus recommend restoration of the entire catchment. Aquatic macroinvertebrates are good indicators of long-term conditions but less sensitive to short-term changes. Multiple approaches, biological and chemical, are encouraged during the restoration process.
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... Different studies have been done on River Rwizi mainly for a small part of the River in Mbarara Municipality with results indicating higher physicochemical parameters of the river than the NEMA standards attributable to pollution from domestic, waste water, agricultural runoff and industrial effluents [12] [13]. ...
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Effect of Different Poultry Manure on the Performance of Tomatoes (Lycopersicon esculentum mill)
Article
Full-text available
  • Jan 2023
Purpose: Tomato is one of the most popular and versatile vegetables in the world and organic production with high yields of desirable quality are a target of many producers. However, the yield of tomatoes in Uganda are low compared to other parts of the world. The reason is that most soils in Uganda are low in fertility. There is widespread soil degradation, due to massive soil erosion resulting into loss of organic matter, high soil acidity and nutrient imbalance hence low crop yields. This study aimed at establishing the effect of different poultry manure on the performance of tomatoes. Methodology: The field trials were conducted in the mid altitude environment at BSU farm. Four treatments which included broiler, Layer, combination of Broiler and Layer chicken manure and the control were applied. The study was carried out in a randomized complete block design replicated four times. Measurements were made on number of leaves, number of flowers, plant height, fruit weight, fruit size, number of tomatoes and yield per hectare. Broiler and layer chicken manure increased the number of leaves, plant height number of flowers, number of fruits, fruit weight and fruit size significantly. Findings: The results indicate that poultry manure is very rich in macro nutrients. Among the treatments, broiler and layer chicken manure gave the highest fruit yield of 13.8 and 13.4 tons per hectare (t/ha) respectively. A combination of the manure produced 12.8 t/ha and the control treatment gave the lowest yield of 8.1 tons per hectare (t/ha). There was no significant difference between broiler and layer chicken manure. Both manures were equally good and enhanced yield. Therefore, farmers may opt for either of the two depending on the availability. Recommendation: The study recommend that either broiler or layer chicken manure can be used for production of tomato in order to achieve high yields.
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Nitrate reductase for nitrate analysis in water
Article
Full-text available
  • Jun 2006
Nitrate analysis in water is one of the most frequently applied methods in environmental chemistry. Current methods for nitrate are generally based on toxic substances. Here, we show that a viable alternative method is to use the enzyme nitrate reductase. The key to applying this Green Chemistry solution for nitrate analysis is plentiful, inexpensive, analytical grade enzyme. We demonstrate that recombinant Arabidopsis nitrate reductase, expressed in the methylotrophic yeast Pichia pastoris, is a highly effective catalyst for nitrate analysis at 37C. Recombinant production of enzyme ensures consistent quality and provides means to meet the needs of environmental chemistry.
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Assessment of cyanobacteria toxins in freshwater fish: A case study of Murchison Bay (Lake Victoria) and Lake Mburo, Uganda
Article
Full-text available
  • Aug 2009
There is little information on the distribution of microcystins (MCs) in Oreochromis niloticus (ON) and Lates niloticus (LN) obtained from L. Mburo and Murchison Bay of L. Victoria. These fishes are harvested and sold both for local human consumption and for export. The presence of MC-RR, MC-LR and MC-YR in different organs (gut, muscle and liver) was determined using Liquid Chromatography coupled with a Mass Spectrometry Detector (LC/MS/MS). The total MCs in ON gut, muscle and liver were 1312.08, 208.65 and 73.10 ng g(-1) from L. Mburo and 1479.24, 9.65 and 48.07 ng g(-1) from Murchison Bay, respectively, while for LN from Murchison Bay they were 27.78, 1.86 and 3.74 ng g(-1). Generally, in both lakes, MC-RR was the most dominant followed by MC-YR and MC-LR, respectively. Gut showed a high MC content, followed by liver and muscle, in that order. The presence of MCs in muscle indicated possible fish contamination, which implied that it was possible to transfer the toxins to humans who are at the end of the food chain. This poses a risk to them since the MCs are heat stable. The local authorities should warn the public of the risk of possible poisoning by eating the contaminated fish.
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The effects of nitrate, nitrite and N-nitroso compounds on human health: A review
Article
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The effects of nitrate, nitrite, and N-nitroso compounds on human health are reviewed. Special emphasis has been placed on the role of these compounds on infant methemoglobinemia and gastric cancer. The discussion on methemoglobinemia includes the source of nitrate or nitrite, diagnosis, treatment, prevention and the contributions of age, gastric pH, gastrointestinal illness, and ingestion of vitamin C to this illness. The maternal transfer of these compounds and the potential effect on fetal death and malformation are also described. The etiology and development of gastric cancer is reviewed as well as the roles of nitrate, nitrite, and N-nitroso compounds in this disease. Endogenous nitrosation and the experimental and epidemiologic evidence linking these compounds to gastric cancer is examined. Other sections include adult methemoglobinemia and acute toxicity, hypo- and hypertension, Balkan nephropathy, slowing of motor reflexes in children, nitrate esters dependence. Sources of nitrate, nitrite, and N-nitroso compounds are detailed. Future areas of research are given.
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COOPERATION IN MANAGEMENT OF WATER RESOURCES IN THE RUIZI CATCHMENT, SOUTHWESTERN UGANDA
Article
Transboundary water resources management is one of the new areas in the sustainable management of water resources in Uganda. The area of lakes shared between Uganda and neighboring countries is approximately 79,000 sq. kilometers. Most of the water resources in the country cut across district boundaries. Cross-sectoral institutional framework for water resources management is vital to manage transboundary water resources with an enabling legal and policy framework in place. River Ruizi is one of such rivers that transect five districts in Southwestern Uganda with a weak or inadequate en- abling environment to manage the water resource across the districts. Through this study, the existing practices and weakness of the legal and policy framework are elaborated and a proposed harmonization of policies is suggested for the Districts sharing water resources in Uganda.
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Variations in the contents of heavy metals in arable soils of a major urban wetland inlet drainage system of Lake Victoria, Uganda
Article
  • Jun 2010
Little is known about the effects of urbanization on the chemical quality of soils in suburban wetland inlet drainage systems to the Uganda side of Lake Victoria, on which food crops are extensively grown. It is feared that pollution in the soils might eventually enter food chains through such crops being consumed by urban populations unaware of their occurrence. Soil samples were collected from cultivated areas of a major wetland drainage system (Nakivubo Channel), at Kampala, Ubanda, near Lake Victoria and from a rural control wetland site (Senge). The soil from this site had similar properties as those from the urban test site (i.e., soil texture; porosity; humus content). Analysis of heavy metals with atomic absorption spectrophotometry (AAS) yielded the following soil concentration ranges: manganese (190–780), cadmium (<0.001–1.0), zinc (6.0–10.0) and lead (10–20 mg kg−1) dry weight for the control site, and 450–900, 1.0–2.0, 131–185, 40–60 mg kg−1 dry weight, respectively, for the urban wetland, indicative of relatively heavy metal pollution in the suburban drainage system. Heavy metal levels in cocoyam (Colocasia Esculenta) and sugarcane (Saccharum Officinarum) grown on both wetland soils also were evaluated via AAS with a modified wet-acid-digestion technique. The results highlighted high cadium and lead levels (P ≤ 0.0003) in the crops from urban wetland cultivation. Cadmium and lead concentrations in cocoyam from urban wetland soils exceeded those from the control site by 0.17 and 3.54 mg kg−1, respectively. The corresponding results for sugarcane indicated a similar increase of 0.56 and 2.14 mg kg−1 of juice extract. Cadmium and lead levels in both urban wetland crops were higher than the maximum permissible limits of the Codex Alimentarius Commission, indicating that these concentrations pose potential health risks to urban consumers, and call for early counter-measures to combat urban pollution entering the lake.
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Zinc, lead and cadmium speciation in Dnieper water‐bodies
Article
  • Jul 2008
Data on the concentrations and movements of Zn, Pb and Cd in Dnieper reservoirs and the Dnieper-Bug estuary are considered. There is a clear trend of increasing concentrations, often two- to fourfold, of these materials from the 1960s to the end of the 1980s. Large increases may be explained as the result of increased human impact on the water-bodies and also because of reduced water discharge in the Dnieper River (discharge has been reduced by nearly 10 km3 in recent years). At present, the average concentrations of Zn, Pb and Cd in Dnieper water-bodies are 35.0–50.0, 15.0–18.0 and 0.5–1.8 μg L–1, respectively. Anodic stripping voltammetry, membrane filtration, ion-exchange and gel permeation chromatography on neutral sephadexes were methods used for analysis. The influence of adsorption and complexation processes on the mobility of Zn, Pb and Cd, and the ratio of their forms were compared. Ratios of free metal ions to ions bound in complexes with natural organic ligands were studied. The binding of metals in complexes with dissolved organic matter (DOM), or their adsorption onto suspended particles, were major processes reducing the concentration of free ions in their most toxic form. The percentage of Zn, Pb, and Cd free ions in the total balance of dissolved forms was no more than 3.6–4.8, 0.2–0.6 and 7.2–9.5%, respectively. The molecular-weight distribution of organic metal complexes and their chemical nature, as well as the potential for complexing of DOM were investigated. Most Zn, Pb and Cd was found as complex compounds with DOM of different chemical natures and molecular weights. Humic substances, particularly fulvic acids, played a major role in the migration of the metals. These ligands bind from 40 to 80% of metals in the composition of organic complexes. Metal complex compounds of relatively low molecular weight (< 5000 Da) predominated in organic complexes of Zn (38–50%), Pb (38–52%) and Cd (22–47%). The role of inorganic ligands in complexation in surface waters was less important.
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Use of TXRF and Convectional Energy Dispersive X‐ray Fluorescence Analysis (EDXRF) to determine trace metal concentrations in waters of Nakivubo Channel and Lake Victoria
Article
  • Jun 2010
To understand better the pollution levels in the waters of the Nakivubo Channel and Lake Victoria, the concentrations of manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn) and lead (Pb) were determined using convectional Energy Dispersive X-ray Fluorescence Analysis (EDXRF) and Total X-ray Fluorescence (TXRF) analysis. Particulate deposits were analysed for trace metals with a convectional EDXRF spectrometer. Extracted dissolved metals contents were analysed with Total Reflection X-Ray Fluorescence. The analyses indicated higher copper concentrations in the filtrate samples collected at the rivermouths and inshore stations than on the particulate matter. Samples from battery manufacturing industry-1 indicated copper concentrations in the filtrate exceeding the National Environmental management Authority (NEMA) drinking water standard of 1.0 mg L−1. Free zinc concentrations were measured for almost all the sampling sites, but at concentrations below the 3 mg L−1 NEMA standard. High concentrations of iron in the labile form measured at the lake shores were above NEMA drinking water standards of 0.3–3.5 mg L−1 in 2006, except for the April 2006 Murchison Bay rivermouth, and for low manganese concentrations in the lake waters. The iron and manganese concentrations on the particulate matter at the upstream end of the Channel, but were lower in the lake waters. Effluents from soap manufacturing industries exhibited elevated total iron concentrations, ranging from 19.038 ± 0.190 to 63.129 ± 6.248 mg L−1 throughout the 2-year study period. The manganese concentrations were the highest for the battery manufacturing industry-2 site in April 2006. The total iron and manganese concentrations were generally higher upstream along the Nakivubo Channel than in the lake waters. Cobalt and lead concentrations were below detection limits for most of the sampling sites. Generally, most metal concentrations along the Nakivubo Channel exceeded acceptable limits, illustrating the need for mitigation measures.
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The speciation of manganese in freshwaters
Article
The extent of current knowledge regarding the speciation of manganese in freshwaters is delineated, and the analytical methods whereby such knowledge is obtained are discussed. Particular attention is paid in the review to the use of electron paramagnetic resonance spectroscopy.
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Chemometric interpretation of heavy metal patterns in soils worldwide
Article
  • Sep 2010
Principal component analysis (PCA) was applied on data sets containing levels of six heavy metals (Pb, Cu, Zn, Cd, Ni, Cr) in soils from different parts of the world in order to investigate the information captured in the global heavy metal patterns. Data used in this study consisted of the heavy metal contents determined in 23 soil samples from and around the Novi Sad city area in the Vojvodina Province, northern part of Serbia, together with those from the city of Banja Luka, the second largest city in Bosnia and Herzegovina, and the ones reported previously in the relevant literature in order to evaluate heavy metal distribution pattern in soils of different land-use types, as well as spatial and temporal differences in the patterns. The chemometric analysis was applied on the following input data sets: the overall set with all data gathered in this study containing 264 samples, and two sub sets obtained after dividing the overall set in accordance to the soil metal index, SMI, calculated here, i.e. the set of unpolluted soils having SMIs<100%, and the set of polluted soils with SMIs>100%. Additionally, univariate descriptive statistics and the Spearman's non-parametric rank correlation coefficients were calculated for these three sets. A Box-Cox transformation was used as a data pretreatment before the statistical methods applied. According to the results, it was seen that anthropogenic and background sources had different impact on the data variability in the case of polluted and unpolluted soils. The sample discrimination regarding the land-use types was more evident for the unpolluted soils than for the polluted ones. Using linear discriminant analysis, content of Cu was determined as a variable with a major discriminant capacity. The correct classification of 73.3% was achieved for predefined land-use types. Classification of the samples in accordance to the pollution level expressed as SMI was necessary in order to avoid the "masking" effect of the polluted soil patterns over the non-polluted ones.
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