Influence of anthropogenic activities and seasons on heavy metals in spring water along Amala and Nyangores tributaries of the Mara River Basin

Anthropogenic activities, including replacing natural forests with human settlements and increased agricultural activities have environmental impacts. The activities can contaminate aquatic ecosystems including spring waters that are sources of major rivers like the Amala and Nyangores, tributaries of Mara River in Mau Complex. In the complex, forestlands have been converted to human settlements and agricultural lands. Although residents of the Mara River Basin use the spring waters for domestic and animal watering purposes, evaluation of the impact the activities have on the spring water quality has not been done. This study evaluated the site and seasonal variations of zinc, copper, selenium, manganese, chromium, cadmium and lead concentrations in spring waters within the Mau Complex where forests have been cleared and converted to anthropogenic activities. The study covered areas along Amala and Nyangores rivers. There were variations (p≤0.05) in the heavy metals levels with sites and seasons. Except for Mn, Cu and Cd which were lower, the levels of the other heavy metals in water from the control points (undisturbed forest areas) were higher in downstream areas that had undergone massive anthropogenic activities. Although there were seasonal variations (p≤0.05), the pattern was not clear. Some heavy metals levels were higher in wet seasons while others were higher in dry season. But the heavy metals levels were within the recommended international standards for domestic/animal use. These results demonstrate that the anthropogenic activities were not yet causing pollution of the spring waters. Maintaining the anthropogenic activities at present levels is recommended. However, periodic monitoring to ascertain the quality of the spring water is necessary to mitigate increase to detrimental levels with time. These results contribute knowledge helping regulatory agencies and management of Lake Victoria basin to formulate monitoring polices to curb water quality deterioration.


INTRODUCTION
Mara River basin, especially on the high highlands, where the main tributaries (Rivers Amala and Nyangores) traverse used to be part of the Mau Forest (McCartney, 2010).The area has undergone massive deforestation (Defersha and Melesse, 2012, Mango et al., 2010, 2011).Between 1973 and2008, the Mau Forest and range land conversion to agriculture was over 203% (Mati et al., 2008).Such conversion to anthropogenic activities cause environmental, soil and water quality degradation problems that affect human, animal and aquatic life (UNEP, 2006).Studies within the Mara River basin have demonstrated that deforestation and human settlement have increased soil erosion and sedimentation and caused extreme water flow events (Dessu and Melesse, 2012, 2013, Mango et al., 2011).The changes these anthropogenic activities can cause in the spring water quality, especially the levels of heavy metals in ground water have not been quantified.
Springs are susceptible to contamination since water feeding them flows through the ground for only a short distance, thus limiting possible natural filtering.Consequently, springs may not be good choice for a water supply if the area uphill has industrial, agricultural, or other activities that can be sources of pollution (Varol and Şen, 2012).In many parts of the world, decline in water quality has been associated with anthropogenic activities uphill of the waters sources.Examples of such incidences include decline in water quality in China (Huang et al., 2015;Yang et al., 2015); Turkey (Varol, 2011;Varol and Şen, 2012), Taiwan (Chen et al., 2015), India (Jain, 2004), Sweden (Loefgren et al., 2014), and Nigeria (Akintoye et al., 2014).The anthropogenic activities in water catchment areas destroy the forest cover necessary in preventing soil erosion and sediment deposition into the water bodies (Foley et al., 2005;Liu et al., 2007).The activities also cause deterioration of underground water quality (Almeida et al., 2007;Duruibe et al., 2007;Micó et al., 2006).Such quality deterioration can be high when the anthropogenic activities are close to springs.In the Mara River basin, forest lands have been converted into human use activities (McCartney, 2010;UNEP, 2006).The basin has witnessed increase in human settlement (McCartney, 2010), agriculture (Matano et al., 2015;McCartney, 2010), urban centers development (McCartney, 2010;UNEP, 2006) and tourist activities, which are possible sources of contamination (McCartney, 2010;Nyairo et al., 2015;UNEP, 2006).
The Mara River drains into Lake Victoria, which thereafter flows into the River Nile and the Mediterranean Sea.The water is a source of livelihood for many people in Kenya, Tanzania, Southern Sudan, Sudan and Egypt.Consequently, its water contamination/quality deterioration can affect lives of many people together with animals and aquatic life.Changes in the water quality of the Mara River water basin have been documented (McCartney, 2010;Nyairo et al., 2015;Wafula et al., 2017).The Mara River sources are mainly the rivers Amala and Nyangores, which are fed by springs in the Mau Forest and former Mau Forest areas within the River Mara basin.There has been no documentation of the contribution of the springs forming sources of Amala and Nyangores Rivers to the Mara River water quality.The objective of this study was to assess the levels on heavy metals in the spring waters feeding the Amala and Nyangores rivers.
Seasonal variations in anthropogenic activities usually influence quality of river water downstream (Ma et al., 2005;Chang, 2008;Li et al., 2009;Simeonov et al., 2003).The water quality changes can be variable where there are seasonal variations in agricultural (Micó et al., 2006), industrial (Ma et al., 2005, Simeonov et al., 2003) and tourist (Almeida et al., 2007) activities.Within the Mara River basin, these economic activities vary with seasons.Usually, tourist activities are high when it is winter season in the northern hemisphere.Agricultural activities within the basin are mainly rain fed and most agricultural activities are undertaken during the long rains in April-June and short rains in October-November (Jaetzold et al., 2007).The main industry within the Mau Complex, is tea production that runs throughout the year.Although, the influence of these activities on the water quality on Rivers Amala and Nyangores were recently demonstrated (Nyairo et al., 2015), their influence on spring water quality have not been established.This study also evaluated the variations in heavy metals (Mn, Cu, Zn, Pb, Cr, and Cd) and Se in springs at the catchment of Rivers Amala and Nyangores with site and seasons.

Study area
The springs were randomly selected in the catchment of Nyangores and Amala rivers located in the Mau Forest Complex within Narok and Bomet counties, Kenya (Figure 1).Mara River basin is a transboundary basin shared by Kenya and Tanzania and is part o the larger Nile River Basin.The basin lies between latitudes 0°38' and1° 03' south and between longitudes 35° 01' and 35° 33' east(Figures 1 and 2).The area was heavily forested (UNEP, 2006, *Corresponding author.E-mail: pokindao@gmail.comor okindaowuor@maseno.ac.ke. Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License  2009) with typical equatorial natural forest trees, but parts have been converted to large and small scale farming and a buffer zone of tea plantation introduced by the government to stop encroachment into the forest.It is an important water tower for the Kenya (GOK, 2008a, b).The small scale farming crops in the area are dominated by maize, beans, peas, potatoes, tea, wheat and A total of sixteen (Table 1) springs were randomly selected, of which two (Tenganda (M2) and Kebenet (M14)) were located in the forest, were used as controls.Springs (Kapsosrurwa (M6), Silbwet (M11), Sotionik 1 (M12), Sotionik 2 (M20), Ainabsabet (M15), Kapsoen 1 (M17), Kapsoen 2 (M18), Chepudonge (M21), Motiok (M22), Chepkesoi (M23), Kapangas 1 (M24), Kapangas 2 (M26), Ndong Ndong (M27) and Siongiroi (M28)) were located in sections of the river where small scale farming of tea, maize and potatoes interspersed with agro-forestry and animal husbandry.

Sampling design and collection
Water sampling was done in two seasons, dry and wet season, using a pre-cleaned water sampler.The water samples were collected just below the water surface and stored in pre-cleaned amber colored 2.5 L glass bottles.The bottles had been precleaned by soaking in 10% nitric acid overnight and rinsed with distilled water on the day of sampling.Each sample was treated with 10 ml of 6N HNO3 solution for preservation.The samples were then transported to the laboratory and filtered immediately using Whatman filter paper then stored at -20°C pending extraction (AOAC, 2000;APHA, 1995).

Determination of parameters
The water samples were filtered through a 1 µm cellulose acetate millipore filter, acidified by 1% (2 ml) concentrated nitric acid, and then pre-concentrated by evaporating 200 to 30 ml on a hot plate at 60°C (Mzimela et al., 2003).The evaporated samples were transferred to a 50 ml volumetric flask and made-up to the volume with double distilled water after addition of 1.5 mg/ml of strontium chloride.
The extracts were analyzed for Pb, Cu, Zn, Mn, Se, Cd and Cr using an atomic absorption spectrophotometer, Shimadzu Atomic Absorption Flame Spectrophotometer, Model AA-6200 (Kyoto, Japan).

Statistical analysis
The data were subjected to statistical analysis of variance (ANOVA) using a two factor completely randomized design.SAS statistical package and GraphPad Prism for students't-test (p≤0.05) was used to check the variations.

RESULTS AND DISCUSSION
All the heavy metals (Tables 2 and 3) significantly (p≤0.05)varied with site for both springs flowing into Amala and Nyangores.Mn, Cu and Cd were lower (p≤0.05) in water from springs that water still under natural forest (Kebenet and Teganda) than springs in areas that had been subjected to anthropogenic activities.For some heavy metals, the levels in spring waters were similar to or higher than those of the control sites, which were in virgin forest areas.The spring water heavy metals ranged from 0.009 to 0.602 ppb for Pb in  All the heavy metals (Tables 2 and 3) varied significantly (p≤0.05) with seasons, with the exception of Cd on the Nyangores River sode.For the springs flowing into Amala River Mn, Cu, Fe, Zn, Cr, and Cd concentrations were higher in wet seasons while Pb and Se were levels were higher in the dry season.Only levels of Mn and Cu were higher while Fe, Zn, Pb, and Cr were lower in wet season than dry season in water flowing into the Nyangores River.Variations in the distribution of heavy metals appeared to be controlled by hydrobiological/geological conditions (Sankar et al., 2010) than the anthropogenic activities.Seasonal variations in heavy metals concentrations in the spring waters may have arisen from the rapid growth of population and increased agricultural activities (Abdel-Baki et al., 2011).The level of heavy metals recorded in water in this study are generally low when compared with the environmental limits suggested by WHO (WHO, 2014) (Table 5), and USEPA (USEPA, 2014).These results demonstrate that the anthropogenic activities in the upper Mau River Complex in the catchment of rivers Amala and Nyangores are not yet causing serious spring water quality deterioration.
Comparison of the mean data from Amala and Nyangores (Table 4) reveals that levels Mn, Cu, Zn, Pb, Cr and Se were not different (p≤0.05),while Fe and Cd were higher in spring waters draining into the Amala River than Nyangores River.The lack of differences in most heavy metals levels were attributed to the fact that these areas were deforested within the same time range and have been subjected to similar anthropogenic activities.Differences in Fe and Cd could have arisen from variations in hydrobiological/geological differences (Tables 6 to 8).
In conclusion, the anthropogenic activities at the catchment of Amala and Nyangores, tributaries of Mara River have not caused serious increase in    interests.

Figure 1 .
Figure 1.A map of Mara River Basin.

Figure 2 .
Figure 2. A Google earth map of Mara River Basin and sampling points.

Table 1 .
Coordinates and local names of springs.

Table 2 .
Heavy metals concentration levels in water from springs flowing in Amala (µg/L).

Table 3 .
Heavy metals concentration levels in water from springs flowing into Nyangores River (µg/L).

Table 4 .
Comparison of Water quality parameters of springs flowing in Amala and Nyangores (Student t test of Amala and Nyangores data for heavy metals in water samples).

Table 5 .
Permissible limits for heavy metals of drinking water set by WHO.

Table 6 .
Levels of physicochemical parameters of water from springs of Amala and Nyangores Rivers.

Table 7 .
Concentration levels of Nutrients in water from springs flowing into Amala (ppb).
*Means with the same letters are not significantly (p≤0.05)different.

Table 8 .
Concentration levels of nutrients (ppb) in water from springs flowing into Nyangores.Commission (LVBC) and the Department of Chemistry of Maseno University.
*Means with the same letters are not significantly (p≤0.05)different.Basin