Salinity and salt fluxes in a polluted tropical river: The case study of the Athi river in Kenya

Kitheka, Johnson U.

doi:10.1016/j.ejrh.2019.100614

Cited by 8 publications

(12 citation statements)

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“…Environmental variables at the coral reefs sampled fell mostly within the ranges considered suitable for coral growth in tropical oceans ( Kannapiran et al, 2008 ; Henkel, 2010 ; Guan et al, 2015 ; Roik et al, 2016 ), except for salinity which was low (i.e., 27.6 – 30.1 ppt) compared to previous estimates (32 – 33 ppt) ( Obura, 2001 ). This may have been due to high rainfalls during sampling and, especially for Malindi which had the lowest salinity occasioned by River Sabaki’s discharge into the ocean ( Kitheka, 2019 ). During heavy rainfalls, salinity has been known to decrease down to 12 ppt in shallow reef flats ( Obura, 2001 ).…”

Section: Discussionmentioning

confidence: 99%

“…This marine park is popular for glass bottom boat tours and snorkeling among other recreational touristic activities. It also experiences significant year-round discharge of freshwater and sediments with different types of nutrients from the Sabaki River which runs through a catchment area dominated by agricultural settlements ( Katwijk et al, 1993 ; Munyao et al, 2003 ; Kitheka, 2019 ; Wanjeri et al, 2021 ). KWS wardens administering the MPA advised that there is considerable illegal fishing in the park at night spilling over from the “reserve,” an area adjoining the park where artisanal fishing is allowed.…”

Section: Methodsmentioning

confidence: 99%

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Cross-Sectional Variations in Structure and Function of Coral Reef Microbiome With Local Anthropogenic Impacts on the Kenyan Coast of the Indian Ocean

et al. 2021

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Coral reefs face an increased number of environmental threats from anthropomorphic climate change and pollution from agriculture, industries and sewage. Because environmental changes lead to their compositional and functional shifts, coral reef microbial communities can serve as indicators of ecosystem impacts through development of rapid and inexpensive molecular monitoring tools. Little is known about coral reef microbial communities of the Western Indian Ocean (WIO). We compared taxonomic and functional diversity of microbial communities inhabiting near-coral seawater and sediments from Kenyan reefs exposed to varying impacts of human activities. Over 19,000 species (bacterial, viral and archaeal combined) and 4,500 clusters of orthologous groups of proteins (COGs) were annotated. The coral reefs showed variations in the relative abundances of ecologically significant taxa, especially copiotrophic bacteria and coliphages, corresponding to the magnitude of the neighboring human impacts in the respective sites. Furthermore, the near-coral seawater and sediment metagenomes had an overrepresentation of COGs for functions related to adaptation to diverse environments. Malindi and Mombasa marine parks, the coral reef sites closest to densely populated settlements were significantly enriched with genes for functions suggestive of mitigation of environment perturbations including the capacity to reduce intracellular levels of environmental contaminants and repair of DNA damage. Our study is the first metagenomic assessment of WIO coral reef microbial diversity which provides a much-needed baseline for the region, and points to a potential area for future research toward establishing indicators of environmental perturbations.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Cross-Sectional Variations in Structure and Function of Coral Reef Microbiome With Local Anthropogenic Impacts on the Kenyan Coast of the Indian Ocean

et al. 2021

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“…The area experiences significant urbanization with population growth and extensive industrial development. Urbanization and industrialization have resulted in increased environmental pollution from the discharge of untreated domestic and industrial wastewater in the river network (32,33). Various horticultural activities are conducted year-round along the rivers owing to the availability of irrigation water.…”

Section: Study Area and Sampling Sitesmentioning

confidence: 99%

Heavy metals and trace elements contamination risks in peri-urban agricultural soils in Nairobi city catchment, Kenya

et al. 2023

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IntroductionWith urbanization and industrialization in the developing world, urban and peri-urban agriculture is increasingly contributing to urban food systems, employment, and income generation opportunities. However, urbanization and industrialization may release harmful pollutants, including heavy metals and trace elements into agricultural soils, posing ecological, environmental and public health concerns. This paper assessed the potential risks of soil contamination with heavy metals and trace elements in peri-urban farmlands in Nairobi city catchment in Kenya. MethodsA total of 60 soil samples were collected from ten vegetable farming zones (S1-S10) and processed following standard protocols. The concentrations of As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn were analyzed in the samples using inductively coupled plasma-mass spectrometry (ICP-MS). Results and discussionResults revealed that the soil samples have elevated concentrations of As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn, with some elements including As (1.7%), Cd (13.3%), Mn (80%), Pb (1.7%) and Zn (11.7%) exceeding the permissible thresholds for agricultural soils. The spatial distribution of the elements exhibited three similar distribution patterns with slight variations between the hotspot sites of the different elements: (i) Co and Mn, (ii) Cu and Cr and (iii) As, Cd, Fe, Hg, Pb and Zn, while Ni and V exhibited singular spatial distributions compared to other elements. Elements such as As, Cd, Co, Fe, Hg, Mn, Pb and Zn appeared to be of anthropogenic enrichment, while Cr, Cu, Ni and V appeared to originate mainly from lithogenic and natural sources. The elements As, Cd, Hg and Pb exhibited high ecological risks, with Cd contributing about 46-66% of the overall ecological risk. The sampling sites S1, S5, S7, S9 and S10 depicted the highest ecological risks of 145, 103, 146, 121 and 146, respectively. The findings call for proper zoning of suitable agricultural areas and sound waste management protocols in urban and peri-urban landscapes. Further, remediation of contaminated soils and farmers’ sensitization are recommended for ecological and public health risk alleviation.

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“…The salinization of rivers might be amplified by droughts, periods of less than normal precipitation, streamflow reduction, and damming (Cañedo-Argüelles et al, 2013;Fakouri et al, 2019;Jalali et al, 2019;Jones & van Vliet, 2018;Kitheka, 2019). During hydrological drought periods, the salinity of rivers in the southern USA increases compared to non-drought periods (Jones & van Vliet, 2018).…”

Section: Introductionmentioning

confidence: 99%

Influences of natural salinity sources and human actions on the Shapour River salinity during the recent streamflow reduction period

Mohammadzadeh‐Habili

Khalili

Zand‐Parsa

et al. 2021

Environ Monit Assess

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and industrial purposes, the ratio of saline-outflow of Shekastian tributary and Boushigan spring to freshoutflow of upper Shapour River increased by ~ 3 times; consequently, river salinity fluctuation domain at the Khesht plain inlet dramatically increased from 2.1-4.0 dS m −1 to 3.7-26.0 dS m −1 . It resulted in major economic damages to the agricultural sector of middle Shapour River. On the seasonal timescale, consecutive processes of salt accumulation during irrigation season of the Khesht plain date orchards and then salt drainage during the rainy season have adjusted salinity fluctuation domain from 3.7-26.0 dS m −1 at the plain inlet to 5.2-8.9 dS m −1 at the plain outlet. In the lower Shapour River, storage/mixing of fresh/saline inflow waters in the Raeisali-Delvari reservoir has adjusted strong river salinity fluctuation domain from 0.9-10.7 dS m −1 at the reservoir inlet to 3.6-5.5 dS m −1 at the reservoir outlet. The success of the Raeisali-Delvari reservoir for salinity adjustment is due to its suitable location on the Shapour River, by being situated downstream of all main river tributaries with natural saline/fresh sources of water.

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Salinity and salt fluxes in a polluted tropical river: The case study of the Athi river in Kenya

Cited by 8 publications

References 9 publications

Cross-Sectional Variations in Structure and Function of Coral Reef Microbiome With Local Anthropogenic Impacts on the Kenyan Coast of the Indian Ocean

Cross-Sectional Variations in Structure and Function of Coral Reef Microbiome With Local Anthropogenic Impacts on the Kenyan Coast of the Indian Ocean

Heavy metals and trace elements contamination risks in peri-urban agricultural soils in Nairobi city catchment, Kenya

Influences of natural salinity sources and human actions on the Shapour River salinity during the recent streamflow reduction period

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