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Recent Submissions
Evaluation of Wetland Loss in Maragua Watershed, Murang’a County, Kenya
(Journal of Sustainable Research in Engineering, 2018) Jacinta M. Muema, J.W. Kaluli, J.M. Gathenya and B.M. Mwangi
Wetlands are habitat to a wide range of biodiversity and thus accommodate some of the world’s most valuable resources.
Unfortunately, their ecosystem services are continuously being lost to destructive anthropogenic activities. Systematic wetland
mapping and inventorying to establish wetland status is necessary. A study was therefore done to determine the wellness of
wetlands; and the temporal and spatial changes in wetlands in Maragua watershed. Normalized Difference Water Index (NDWI),
Normalized Difference Vegetation Index (NDVI) and Topographic Wetness Index (TWI) were used to extract wetlands areas.
Additionally, interviews, storytelling events, stakeholder workshop, focus group discussions and personal observations were used
to obtain qualitative data on human activities in wetlands and the challenges facing wetlands in the study site. In 1987 the area
under wetlands in Maragua was 24.1 ha, in 1999 it was 12.8 ha and by 2018 wetlands covered only 10.1 ha. Further, the wetlands
are more concentrated on the downstream side of catchment. Additionally, wetland cultivation, planting of exotic trees and fodder
grass farming are the main human activities taking place within the wetlands. It was observed that the local communities are neither
aware of the adverse effects of their activities on the wetlands nor the potential benefits of conserved wetlands. With the help of
various stakeholders, the County Government of Murang’a has opportunities to create awareness and educate the residents of the
study area about the potential benefits of conserving their wetlands.
Effects of Land Use and Land Cover Change on Potential Ecosystem Service Value in Mathioya Watershed, Murang’a County, Kenya
(Journal of Sustainable Research in Engineering, 2022) Movin O. Oginga, James W. Kaluli, Benson M. Mwangi and James M. Raude
Wetlands in Mathioya watershed are declining due to continued alterations caused by human and natural factors.
This study assessed the effects of spatiotemporal changes in Land Use and Land Cover (LULC), on potential ecosystem service
value in Mathioya watershed, Murang’a County, Kenya. We considered the period between 1987 and 2020. Supervised
classification using maximum likelihood classifier was performed in ERDAS imagine v.15. The values obtained from the
analysis of LULC maps were then used together with the global data for habitats to approximate the ecosystem service value
(ESV) change within the watershed. Six LULC classes namely, forestland, wetlands, agricultural land, water bodies, built-up
areas and barren lands, were identified. Analysis of Landsat images revealed that between 1987 and 2020, human activity led
to decrease in the area covered by wetlands, forestland, water bodies, and barren land. Area under these land cover classes
decreased by 45%, 34%, 50% and 27%, respectively. During the study period, agricultural land and built-up areas increased
by 43% and 85%, respectively. Changes in LULC resulted in decline of ESV from $368.5 million/ha/year in 1987 to $337.7
million/ha/year in 2020. With respect to individual ecosystem services, regulating services declined. Between 1987 and 2020,
water regulation and climate regulation declined by 48% and 16%, respectively. However, provisioning services such as food
production increased by 34%. Wetlands play a critical role in the provision of ecosystem services. The loss of wetlands
translated to decline of critical ecosystem services such as water regulation. Eventually, this will lead to poor water quality
within the watershed and the entire County, thus impacting negatively on the health of the locals. Hence, there is a need for
urgent action to prevent the current trend of wetland loss within Mathioya watershed.
Effects of Catchment Land Use on Nutrients and Heavy Metals Inflows into Maragua and Mathioya Wetlands in Murang’a County, Kenya
(International Journal of Research and Innovation in Applied Science (IJRIAS), 2025-05-08) Evans Kipkemoi, Warren Andrew Andayi, B.M. Mwangi, Eric C. Njagi and Margaret W. Kariuki
etland ecosystems in Murang’a County are diminishing due to increased catchment land use practices. Part of
wetlands have been converted into farmlands where various agricultural activities are carried out while some
parts have been converted into settlement points. Agricultural practices carried out along wetland ecosystems
involve the use of excessive agrochemicals during crop production which later contribute to wetland pollution
through nutrients and heavy metals inflows. This study aimed at assessing the effects of catchment land use on
nutrient and heavy metals inflows into Maragua and Mathioya river basins in Murang’a County. Water samples
were collected using the Grab technique, packed in plastic containers, kept in cool boxes, and transported to the
research laboratory for analysis. Phosphate and nitrate concentrations were analyzed across different seasons,
sampling stations, and sampling levels. During dry season, the mean phosphate concentration was 0.0259 ±
0.0051 mg/L with a standard deviation of 0.0124 mg/L. In wet conditions, the mean phosphate concentration
increased to 0.1631 ± 0.1509 mg/L with a standard deviation of 0.3697 mg/L. For nitrate, the mean concentration
during dry conditions was 9223.37 ± 2672.33 mg/L with a standard deviation of 6545.84 mg/L, and during wet
conditions, it remained the same at 9223.37 ± 2008.17 mg/L with a standard deviation of 4919.00 mg/L.
Elemental analysis was performed using Microwave Plasma-Atomic Emission Spectroscopy (MP-AES)
instrument. Mean concentrations of lead during dry seasons were 0.005 ± 0.002 mg/L and during wet season,
they increased to 0.012 ± 0.004 mg/L. Zinc concentrations were 0.01 ± 0.003 mg/L during dry season and
increased to 0.015 ± 0.004 mg/L during the wet season.
The mean concentrations of zinc in the water samples were significantly lower than the maximum residue
concentrations set for drinking water by the World Health Organization (WHO). However, lead (Pb)
concentrations were above the WHO recommended maximum residue level. ANOVA analysis indicated no
significant seasonal differences in phosphate (F=0.825, p=0.385) and nitrate (F=3.090, p=0.109) levels.
Similarly, no significant differences were found between different sampling stations for phosphate (F=1.081,
p=0.323) and nitrate (F=0.478, p=0.505). Analysis by sampling levels showed no significant differences noted
for phosphate (F=0.979, p=0.412) and nitrate (F=1.949, p=0.198). For heavy metals, no significant differences
were found for lead (F=1.234, p=0.271), cadmium (F=0.893, p=0.348), and zinc (F=1.567, p=0.223) across
different seasons and sampling stations.
These findings suggest that nutrient and heavy metal inflows into the wetlands are relatively stable and uniform
across different spatial and temporal scales. The study highlights the importance of consistent land use practices
and the effective buffering capacity of wetlands in maintaining ecological balance.
Removal of Nitrites from Wetland Waters Based on Diazonium Silica
(American Journal of Chemistry, 2025) Aquiline Kathambi, Peter W. Njoroge, Sylvia A. Opiyo, Isaac Waweru, Benson M. Mwangi
Diazonuim silica was prepared and used to remove nitrites in wetland waters. Raw silica was chlorinated using
phosphorous pentachloride (PCl5). Chlorinated silica was further reacted with ethylenediamine (EDA) under reflux to give
aminated silica. Thereafter, aminated silica was protonated to yield diazonium silica which was used as the adsorbent. The
prepared diazonium silica material was characterized using Fourier Transform Infrared (FT-IR) showing bands at
wavenumbers 1049 and 791 cm-1 of the anti-symmetric and symmetric stretching modes (Si-O-Si) of SiO4. The shift in
spectra band of Si-O-Si from 1051cm-1 in raw silica to 1049cm-1, was attributed to diazonium silica. Additionally, a new open
chain azo (N=N) group band was found in the region 1575cm-1 -1630cm-1. The physical adsorption parameters examined
using batch adsorption system including: pH, initial concentration, contact time and temperature were made using sorption
models, adsorption kinetics and thermodynamics. The results obtained showed 3.0 as the optimal pH for adsorption of NO2-,
303K as the optimal temperature, optimum contact time as 60 minutes and optimal initial concentration as 20ppm. The
adsorption capacity of nitrites using diazonium silica adsorbent was achieved at 16.45mg/g. For sorption of nitrites in
diazonuim silica, Langmuir isotherm model was obeyed according to correlation coefficient R2 = 0.97182 close to unity.
Adsorption kinetics of nitrites in diazonium silica pseudo second order was best obeyed while, thermodynamic parameters
revealed that the sorption of nitrites into diazonium silica was exothermic in nature. From the results obtained, diazonium
silica is an efficient adsorbent for adsorption of nitrites compared to raw silica.
Adsorptive removal of phosphates from wetland waters using silica molyb date adsorbent
(Journal of Emerging Technologies and Innovative Research, 2025-02) Aquiline Kathambi, Peter W. Njoroge, Sylvia A. Opiyo, Isaac Waweru, Benson M. Mwangi
World’s most productive and valuable ecosystem is the wetlands. Quality and functions of wetlands have been
affected adversely by deforestation, fertilizers, and pesticides among others. Pollution by phosphates affect aquatic
life as they have serious side effects at very low levels. Silica molybdate was prepared by first chlorinating silica
sand using phosphorous pentachloride (PCl5) to give chlorinated silica. Amination of chlorinated silica was done
using Ethylenediamine (EDA) and later molybdate was chemically grafted to the aminated silica to yield silica
molybdate. Silica molybdate was used to reduce the levels of PO4 3- residues from wetland ecosystem.. Molecular
structure of the silica molybdate material was characterized using Fourier Transform Infrared (FT-IR). FT-IR results
showed Adsorption bands at 854cm-1 and 542cm-1 which were attributed to Mo=O and Mo-O stretching in
molybdate. Peaks observed at 1388 and 1662cm-1 were attributed with the vibration mode of Mo-OH bond and
bending mode of adsorbed water. Spectra peaks observed at 542, 634.58 and 898.97 cm-1 were attributed to the
adsorption of molybdate. The physical adsorption parameters which were examined using batch adsorption system
were; temperature, pH, contact, time, initial concentration using sorption models, adsorption kinetics and
thermodynamics. Results showed that optimum pH for biosorption of PO4 2- was 6.0, optimal contact time was 30
minutes, optimum temperature was 45 ℃. The experimental results obtained showed that the maximum phosphate
adsorption of silica molybdate was achieved at 194.93mg/g at adsorption optimal conditions of pH, temperature
and contact time. The phosphate removal based on silica molybdate will offer several benefits such as low cost,
effectiveness and reliability to lower the levels of phosphates in wetland waters as compared to commercial
activated carbon. Based on the adsorption efficiency values obtained from this study and comparing them with
adsorption efficiency reported in the literature, it can be concluded that silica molybdate is super adsorbent for the
removal of phosphates from wetland waters.
