The present study aims to compare physico-chemical parameters of Agneby and Me rivers of Côte d'Ivoire. A total of eight (8) physico-chemical parameters were determined in nine (9) localities surveyed on both the Agneby and Me Rivers. Sampling were carried out on a seasonal frequency between August 2015 and July 2016. Principal Component Analysis (PCA) of both rivers showed that Agneby River localities were characterized by warm water (27.08 ± 0.87°C), neutral pH (7.07 ± 0.26), high salinity (0.05 ± 0.04 ‰), relatively high levels of dissolved substances (58.01 ± 32.19 mg/L), and low resistivity (26.97 ± 22.46 kΩ/cm) compared to Me River localities. Bravais Pearson correlation matrix between physico-chemical parameters of both rivers showed a strongly significant positive correlation between salinity and conductivity (0.89), salinity (0.90) and TDS, conductivity (0.91) and total dissolved solids, and a negative highly correlation was observed respectively between pH and redox potential (-0.75), pH and resistivity (-0.73), resistivity and total dissolved solids (-0.64), resistivity and conductivity (-0.57) and between resistivity and salinity (-0.57).
In Côte d'Ivoire, freshwaters are divided into 1,760 km² of artificial lakes made up of hydroelectric dams (Ayamé 1 and 2, Kossou, Taabo, Buyo and Fayé) and hydro-agricultural dams, and 3,000 km of rivers (Cavally, Sassandra, Bandama, Comoe, Agnebi, Me, ... etc.). These freshwaters are an indispensable resource for life. These areas generate intense activities such as fishing and aquaculture but are also dumping sites for many pollutants related to human activities. Unfortunately, these two rivers are being disrupted by human activities, namely, beverage factories, sand extraction for construction profits. According to 1, these two rivers are subject to the discharges of agricultural practices such as coffee, cocoa, oil palm and rubber tree crops, etc. These areas are enriched by phyto-sanitary products and fertilizers that are partly found in these rivers during the rains. Furthermore, 2 reveal that the modification of the forest to the profile of agricultural activities leads to the elimination of essential components of the aquatic environment. The modification of the aquatic environment inevitably leads to the degradation of the rivers, putting at risk the existence of the species that live in them. Indeed, population growth accompanied by rapid urbanization causes many disturbances to natural environments 3. Also, rampant industrialization, unsustainable use of fertilizers and pesticides on plantations and the lack of awareness of the population towards the protection of the environment, lead eventually to an imbalance of the ecosystem and generate polluting elements which can affect the physicochemical and biological quality of the receiving aquatic environments 4, and also alter the uses of water 5.
The objective of this study aims to evaluate the physicochemical quality of surface water and the seasonal evolution of these parameters in the Agneby and Me rivers.
Agneby and Me rivers are both located in the south of Côte d'Ivoire on a cumulative area of approximately 13,200 km2. They extend between 3°30'- 4°45' longitudes West and 5°20' - 6°55' latitudes North. They are limited by the watersheds of the Bandama River in the West and the Comoe River in the East 6. Agneby River has its source in Abongoua, in Bongouanou department. This river has 200 km lenght and watershed covers an area of 8,900 km2. It flows into the Ebrie lagoon near Dabou. Me River is rises in Besso classified forest in the north-east of Adzope town and flows into the Potou lagoon. Me River has a length of 140 km for a catchment area of 4300 km2 7. The river receives four tributaries Mafou (main tributary), Bobié, Abé and Bogbo.
The physico-chemical characteristics of the Agneby and Me Rivers were studied seasonally through four (04) measurement campaigns carried out from August 2015 to December 2016. The measurement and sampling campaigns were carried out in 24 localities comprising 72 stations (Figure 1). Nine (9) environmental variables have been taken into account during this study. Water temperature, salinity, pH, redox potential, electrical conductivity of water, electrical resistivity and dissolved solids were measured in situ using a multi parameter HQ 3d. Turbidity was measured using a secchi disk.
2.3. Statistical AnalysisVariance Analysis (ANOVA), Tukey's Honest Significant Difference (HSD) Test, Principal Component Analysis (PCA) and Bravais-Pearson Correlation (r) were used to compare variation on these parameters between stations, localities, Rivers and seasons of the year (max probability retained: p-level = 0.05). All these analyses were performed using STATISTICA 7.1 software.
At the Me River, temperature values observed in the dry season range from 24.20°C in Adonkoi to 28.90°C in Zodji with an average temperature of 26.17 ± 1.53°C. During the rainy season, temperature varies between 24.89°C at Adonkoi and 28.06 ° C at Grand Akouzin with an average temperature of 26.35 ± 0.88 ° C (Table 1).
In the Agneby River, an average temperature observed in the dry season is 27.0 ± 1.04°C. It varies between 25.83°C in the locality of Offa and 28.92°C in the Arraguié locality. In the rainy season, it fluctuates between 26.4°C in Arraguié and 28.7 ° C in Attehou. The average temperature observed is 27.10 ± 0.70 ° C (Table 2).
Anova analysis and the Tukey post hoc HSD test showed a significant difference (ANOVA, p < 0.05) between spatial variation of Agneby and Me Rivers waters temperature. Water temperature is lower in the Me River (26.32°C) and higher in the Agneby River with a value of 27.16°C. In addition, no significant difference variation was observed (ANOVA, p> 0.05) between seasons in sampled localities.
In the Me River, the lowest pH value during the dry season is 5.60 at Ahoutoué and the highest at 7.06 at Grand Akouzin with an average pH of 6.71 ± 0.46. In the rainy season, pH varies from 5.66 in the locality of Ahoutoué to 7.28 in the locality of Grand Akouzin. The average pH observed during this period is 6.81 ± 0.47 (Table 1).
In Agneby River, pH value obtained in dry season is 7.05 ± 0.28. The smallest value pH = 6.53 was recorded in Attehou and the highest value pH = 7.38 was observed in Offoriguié. During rainy season, pH values fluctuate between 6.7 in Arraguié and 7.39 in Gbessé with an average pH value of 7.09 ± 0.25 (Table 2).
Anova test analysis of hydrogen potentials and Tukey's post hoc HSD test showed a highly significant spatial difference between the waters of Agneby and Me Rivers (ANOVA, p < 0.05). The low pH is observed in Me River (pH= 6.8) and higher measured in Agneby River with a value of 7.08. Between seasons and localities, analysis of variance Anova showed no significant difference (ANOVA, p > 0.05) in the two rivers.
In Me River, seasonal variations of salinity in the dry season fluctuate between 0.02 and 0.06 ‰ with an average value of the water salinity is 0.03 ± 0.01 ‰. The lowest values were observed in Ahoutoué and Diasson, and the strongest in Duquesne Cremone. In rainy season, it oscillates from 0.01 to 0.05 ‰ with an average of 0.02 ± 0.01 ‰. The lowest values in this season are noted in Ahoutoué, Great Akouzin and Adonkoi ; and the strongest at Duquesne Cremone (Table 1).
In Agneby River, during dry season, minimum value of salinity (0.02 ‰) was measured in M'brou and maximum value 0.17 ‰ was recorded in Offoriguie. In rainy season, water salinity varies from 0.01 ‰ in the locality of M'brou to 0.05 ‰ in Ottopé (Table 2).
Anova test and Tukey post hoc HSD test showed a significant spatial variation of salinity (ANOVA, p < 0.05) between Agneby and Me Rivers. Salinity of the water is low (0.03 ‰) in the Me River and hight (0.07 ‰) in Agneby.
Between seasons and localities, a significant seasonal difference (ANOVA, p < 0.05) was observed in each River. The salinity of the Agneby and Me rivers remains high during the dry season and low during the rainy season.
In Me River, during during dry season, the average conductivity is 87.52 ± 54.94 μS / cm. It oscillates between 55.65 μS / cm at Diasson and 120.50 μS / cm at Duquesne Cremone. During rainy season, it varies between 31.57 μS / cm at Ahoutoue and 116.66 μS / cm at Duquesne Cremone. The average during this season is 55.58 ± 24.96 μS / cm (Table 1).
In Agneby River, the values of the electrical conductivity in the dry season fluctuate between 53.9 μS / cm at M'brou and 325.0 μS / cm at Arraguie with an average of 169.84 ± 103.57 μS / cm. In the rainy season, water conductivity varies from 38.55 μS / cm at M'brou to 117.80 μS / cm at Offa. The average conductivity noted during this season is 85.67 ± 24.77 μS / cm (Table 2).
Anova test of comparaison between Agneby and Me Rivers showed a significant statical difference (ANOVA, p < 0.05). Electrical conductivity is low in the Me River (70.11 μS / cm) and hight in Agneby River (141.02 μS / cm). Between season and localities, in Agneby and Me Rivers Anova test showed a significant difference (ANOVA, p < 0.05).
The mean values of total dissolved solids in Me River during dry deason ranged from 26.1 mg / l in Diasson to 69.07 mg / l in Duquesne Cremone localities. An average during this season is 43.14 ± 14.88 mg / l. In rainy season, TDS ranged from 14.79 mg / l in the locality of Ahoutoue to 100.34 mg / l in the locality of Duquesne Cremone. An average recorded during rainy season is 31.65 ± 26.54 mg / l (Table 1). The variance analysis showed no significant differences (ANOVA, p > 0.05) between seasons.
In the Agneby River, an average of TDS during dry season is 82.48 ± 48.41 mg / l. The minimum value (42.50 mg / l) was recorded in Ottope and the maximum value (171.50 mg / l) in Offoriguie. During the rainy season, the lowest value of TDS (18.02 mg / l) was measured in the locality of M'brou and the highest value (57.51 mg / l) was recorded in Offoriguie locality with an average value of 41.09 ± 12.85 mg / l (Table 2).
Anova and Tukey post hoc HSD tests showed a statistical significant difference (ANOVA, p < 0.05) between Agneby and Me Rivers. The high of TDS has recorded in the Agneby River (62.24 mg / l) and low value in the Me River (37.32 mg / l). Between seasons, Anova test showed a significant difference (ANOVA, p < 0.05). TDS remains high during dry season and decreases in the rainy season.
Durin dry season in the Me River, resistivity values fluctuated between 7.27 kΩ / cm and 23.18 kΩ / cm respectively Duquesne Cremone and Ahoutoue localities. The average value recorded during this season is 13.07 ± 5.10 kΩ / cm. In rainy season, resistivity varies between 44.44 kΩ / cm in Mafa-mafou and 170.74 kΩ / cm in Ahoutoue with an average of 93.92 ± 30.3 kΩ / cm (Table 1).
In Agneby River, during dry season, an average of resistivity value noted, is 8.0 ± 2.80 kΩ / cm. The minimum value 2.80 kΩ / cm was observed in Offoriguie and the maximum 11.57 kΩ / cm was obtained in Ottope. During rainy season, resistivity values varies from 17.92 kΩ / cm to 73.59 kΩ / cm respectively in M'brou and Ehoueguie localities. An average value during this season was 45.89 ± 16.08 kΩ / cm (Table 2).
The Anova comparison test between water resistivity of Agneby and Me rivers, in addition to Tukey's post-hoc HSD test, did not reveal any spatial variation in this parameter between the two rivers (ANOVA, p > 0.05). Between seasons, anova comparison test showed a significant difference (ANOVA, p < 0.05) for each rivers. Water resistivity is hight during rainy season et low in dry season.
In Me River, during dry season, redox potential average recorded was 92.75 ± 36.57 mV. The redox potential varied from 53.6 mV in Diasson to 181.97 mV in Ahoutoue during this season. In the rainy season, redox potential fluctuated between 47.16 mV at Duquesne Cremone and 159.57 mV at Ahoutoue with an average of 95.98 ± 30.3 mV (Table 1).
During dry season, the mean value of the redox potential is 76.06 ± 24.02 mV in Agneby River. Minimum value 30.20 mV was noted at Offa and the maximum value of 102.7 mV was observed in Attehou. In the rainy season, the redox potential fluctuates between 44.9 mV at Anno and 108 mV at Arraguie with an average of 74.08 ± 20.83 mV (Table 2).
No significant statistical difference (ANOVA, p > 0.05) of Redox potential was observed between Agneby and Me Rivers localities. Also, analyse of seasonal variation by Anova test showed no significant differences (ANOVA, p > 0.05) between the two rivers.
During dry season, in Me River, water transparency varied between 10.5 cm in Zodji and 45.7 cm in Ahoutoue with an average of 23.25 ± 10.79 cm. In the rainy season, water transparency varied from 18 cm in Zodji to 43.5 cm in Apiadji localites with an average 32.57 ± 9.55 cm (Table 1). Variance analysis showed a significant difference (ANOVA, p < 0.05) between seasons. However, lower value of water transparency was noted in the dry season and high in the rainy season.
During dry season, mean value of transparency in Agneby River was 31.16 ± 11.46 cm. The low value 20.1 cm was observed in Offa and the high 50 cm observed in Gbesse. In the rainy season, water transparency oscillated between 10 cm in Attehou and 49 cm in Gbesse and M'brou with an average of 30.96 ± 14.61 (Table 2). No statistical diffence was observed between the localities sampled in Agneby River.
Between both Rivers, Anova test showed no statistical significant difference (ANOVA, p > 0.05), in localities and in seasons.
3.2. Correlation between Localities and Physico-chemical ParametersCorrelations between localities and environmental variables measured in Me River are based on a Principal Component Analysis (PCA) (Figure 2A). ACP first axis contributes to 59.47% of the cumulative variance localities environmental variables, and is expressed by temperature (0.58), salinity (0.94), conductivity (0.95), Total Dissolved Solids (0.90) on the positive side, resistivity (-0.90) and redox potential (-0.83) on the negative side. The second axis (axis 2) has a contribution to 16.84% of the variance. It is expressed by the hydrogen potential (-0.66) and water transparency (-0.57) towards its negative side.
The locality factor map (Figure 2B) attached to the correlation circle of the variables, defines four groups of localities. The first group consisted by Ahoutoue locality was characterized by high values of redox potential and would define an oxygenated area and a high electrical resistivity. The second group consisted only by Zodji locality had high temperatures. The third group represented by the locality of Duquesne Cremona was characterized by high concentrations of electrical conductivity, an average concentration of total dissolved solids and water salinity. The fourth group consisted by localities of Lobo Akouzin, Grand Akouzin, Diasson, Mafa-mafou and Apiadji, was characterized by low pH and water transparency.
Bravais Pearson correlation matrix between the physicochemical parameters (Table 3) showed strongly significant positive correlation between TDS and salinity (0.97), and between TDS and conductivity (0.96). A positive and highly significant correlation is noted between salinity and conductivity (0.95). In contrast, a highly significant negative correlation was observed between hydrogen potential and redox potential (-0.81), and between salinity (-0.79), conductivity (-0.85), TDS (-0.71) and resistivity. The correlation matrix of Bravais Pearson also showed a weakly significant negative correlation between water transparency and conductivity (-0.56); between transparency and TDS (-0.53), and between redox potential and TDS (-0.57).
The correlations between all environmental variables examined with a principal component analysis (PCA) showed that F1 axis expresses 39.10% of the variance and was expressed by the conductivity (-0.97), Total divolved solids (-0.95) and salinity (-0.92) on the negative side. With an inertia of 35.58%, second axis F2 was determined by water transparency (0.77), hydrogen potential (0.71) on the positive side and temperature (-0.76) on the negative side (Figure 3A).
Localities factor map (Figure 3B) associated with correlation circle of environmental variables, defines three groups of localities. The group composed to Offoriguie, Gbesse and Arraguie localities was characterized by electrical conductivities, salinities, high total dissolved solids and low resistivity. The second group, composed to Anno, Offa and M'brou localities was defined by warm waters. Third group, consisting of Attehou, Ehoueguie and Ottope localities was characterized by high electrical conductivities, moderately saline waters and low-rate dissolved solids.
Bravais Pearson correlation matrix between physicochemical variables (Table 4) showed a strongly positive correlation between total dissolved solids and conductivity (0.94) and total dissolved solids and salinity (0.87), water temperature and redox potential (0.70), and conductivity and salinity (0.86). In contrast, Bravais Pearson's correlation matrix showed a strong negative correlation between water transparency and resistivity (-0.83). Moderately significant correlation was observed between hydrogen potential and resistivity (-0.59) and between hydrogen potential and transparency (0.53).
3.3. Agneby and Me Rivers CombinedPrincipal Component Analysis (PCA) showed the distribution of localities in F1-F2 factorial axis (Figure 4). This factorial axis F1-F2 expressed both 70.72% of total inertia. In the distribution of variables on factorial axis F1-F2, axis 1 with 51.52% of the cumulative variance was represented by resistivity (0.84) and redox potential (0.69) on positive side and by hydrogen potential (-0.72), water salinity (-0.85), conductivity (-0.88) and total dissolved solids (-0.89) on the negative side.
The second component axis 2, with an inertia of 18.90%, is expressed by pH (0.56) and water transparency (0.54). The factorial map of the localities (Figure 4) associated with the correlation circle of the environmental variables, defined two groups. The first group (I) was represented by the localities of Agneby River. This group is characterized by waters weakly basic, salty, with a water conductivity relatively low, high concentrations of total dissolved solids and temperate waters. The second group (II) to the right of the factorial axis F1, represented by localities of Me River. This group was characterized by low water transparency and concentrations of redox potential.
Bravais Pearson correlation matrix (Table 5) between the physico-chemical parameters of the waters of the two rivers indicated a strongly significant positive correlation on one hand between salinity and conductivity (0.89), salinity (0.90) and TDS, conductivity (0.91) and total dissolved solids. On the other hand, negative highly correlation was observed respectively between pH and redox potential (-0.75), pH and resistivity (-0.73), resistivity and total dissolved solids (-0.64), resistivity and conductivity (-0.57) and between resistivity and salinity (-0.57).
In this study, the water temperature of the Agneby River (27.08 ± 0.87°C) was statistically higher (p < 0.05) than that of the Me River (26.33 ± 1.2°C). This difference in temperature could be explained by the influence of the canopy, which is much less pronounced on the Agneby River. In this way, the sun's rays arrived directly on the surface of the river, inducing a rise in the temperature of the surface water 8.
From a seasonal perspective, temperature average observed on the Me River varies from 24.54 ± 0.48°C to 28.14 ± 0.12°C. These values are comparable to those recorded in other coastal basins of Côte d'Ivoire such as Cavally (23 and 28°C) 9, Boulo and Bodouakô rivers of the Tanoe-Ehy lagoon complex (24.81 to 27.47°C) (Djiriéoulou, 2013). In addition, no seasonal variation was observed during the sampling period between this two Rivers. This could be explained, as pointed out by 10, by a constant maintenance of this parameter linked to low precipitation and by strong sunshine during the sampling period in these two basins.
As for the Agneby River, the average temperature measured varies between 26.21 ± 0.54°C and 28.2 ± 0.7°C. This observation is similar to that of 11 in Aby lagoon (27.4 °C). However, our results differ from those obtained by 12, which recorded an average value of 26.0°C on the Agneby River. This observed temperature difference would be due to the sampling period measured by this author between October 2001 and March 2002. Also, the high temperature of the ambient air above the survey points could also increase the temperature of the waters. According to 13. The non-significant seasonal variation in temperature reflects a certain constancy of this parameter was reported by 14 in the Aby-Tendo-Ehy lagoon complex.
The pH of the Me River waters (6.76 ±0.45) is statistically lower than that observed in the Agneby River (7.07 ±0.26). This difference in acidity could be explained by the discharge of very marked chemical effluents from anthropogenic activities, particularly banana, coffee, cocoa and rubber plantations located along most of the Agneby River localities. On a seasonal scale, the localities of the Me River are acidic both in dry season (6.71 ± 0.46) and in rainy season (6.81 ± 0.47). These values are similar to those of 12 and 9 which recorded respectively pH 6.70 on Me River and pH 6.60 in most rivers of Côte d'Ivoire. However, this result differs from the work of 15 and 14 who recorded a value of pH 7.05 on the Me River and pH 7.26 in Nouamou on Ehy Lagoon, respectively. This acidic character observed during the two seasons would probably be due to the decomposition of dead wood and the nature of the substrate. Also, a nonsignificant seasonal variation in pH could be explained by a low constancy in the concentration of carbon acids related to a dominant mineralization of organic matter during both seasons.
As for the Agneby River, the average value of the pH of the water measured is close to neutrality, both in dry season (7.05 ± 0.25) and in rainy season (7.09 ± 0, 25). These results are consistent with those of 12 and 14 who respectively found a value of 7.0 in the Me River and Tiapoum in the Ehy Lagoon. These neutral pH observed during the two sampling seasons could be explained by low water dilutions. According to 16, the increase in pH values towards a neutral pH could be attributable to the dilution effect of water during this period.
In both Rivers, salinity of Me River (0.03 ± 0.01 ‰) is statistically lower than that recorded in the Agneby River (0.05 ± 0.04 ‰). This difference is due to its proximity with Ebrie lagoon, whose surface water salinity varies between 14.26 and 18.85 ‰. According to 17, the level of salinity in fresh water is high when the level of the lagoon is relatively low. The average salinity of the localities surveyed on both rivers is high during dry season (0.04 ‰ in the Me River and 0.07 ‰ in the Agneby River) and low during rainy season (0.02 ‰ in the Me and 0.03 ‰ in Agneby). In addition, there are small seasonal variations in both rivers during the sampling period. These observations could be explained by the low influence of precipitation observed during rainy season. Thus, under the effect of dilution, the salinity level decreases.
Water conductivity of Me River (71.55 ± 29.26 μS / cm) is statistically lower than that recorded in the Agneby River (127.75 ± 84.92 μS / cm). This difference can be explained by the fact that at the Agneby River, urban runoff contains quantities of calcium, magnesium, potassium, nitrate and sulphate ions that dissolve in water. In addition, in the Me River indicate conductivities (87.52 ± 24.94 μS / cm) noted in dry season and 55.58 ± 24.96 μS / cm in rainy season were similar to those observed by 9 (59 μS / cm) in the Bandama and Marahoué (71 μS / cm) Rivers. However, these results are contrary to those of 18 who noted a high conductivity value 105.14 μS / cm in the Bandama River. According seasons, variations in electrical conductivity of water could be explained by the influence of certain factors such as precipitation, evaporation of water and type of substrate. Also, this variation observed would be related to seasonal changes in salinity, because electrical conductivity and the salinity of water are strongly correlated. Similar results were recorded by 19 between Kossou and Taabo lakes.
In Me River, the mean TDS value is between 43.14 ± 14.88 mg / l in dry season and 31.65 ± 26.54 mg / l in rainy season. In Agneby River, the mean value of TDS varies between 82.48 ± 48.41 mg / l during dry season and 41.09 ± 12.85 mg / l. Thus, the evolution of TDS follows that of electrical conductivity. The minimum and maximum values of the conductivity coincide respectively with those of the TDS in the two rivers. This correlation confirms the work of 15. According to this author, the rate of dissolved solids and the conductivity evolve in the same order of magnitude. These two parameters show almost similar average values in most sampled localities. Indeed, the solids dissolved in the aquatic environment contain large quantities of ions such as calcium, magnesium, iron, etc. These high quantities of ions in the aquatic environment induce high electrical conductivity.
With regard to the electrical resistivity of water, it refers to the ability of water to oppose the movement of ions in the aquatic environment. According to 20, resistivity is inversely correlated with conductivity. In Me River, average resistivity value is low (13.07 ±5.10 kΩ/cm) during the dry season and high (93.92 ±40.6 kΩ/cm) during rainy season. This low value would be explained by the seasonal variation in the electrical conductivity of the water in this river. Similar observations were recorded in the Agneby River during this study.
The redox potential or oxidation-reduction potential is a parameter that affects the oxidation states of the elements hydrogen, carbon, nitrogen, oxygen, sulphur, iron, etc. In well-oxygenated water, oxidation conditions dominate. When oxygen concentrations decrease, the environment becomes more reductive, which results in a reduction of the redox potential 21. In the present study, redox potential of Me River (94.36 ±32.62 mV) is statistically identical to that of Agneby River (74.89 ±20.50 mV). Also, the redox potential of well-oxygenated water without the presence of organic matter hovers around 350 mV in fresh water 22. The redox potential values recorded in these two rivers would place them in the range of less oxygenated water.
Seasonal variations in redox potential do not differ statistically from one River to another. These observations could be explained by the low production of oxygen from the photosynthetic activity of phytoplanktonic algae during both seasons.
Transparency is an indicator of the degree of pollution and makes it possible to follow the trajectory of an effluent 23 et 24. In all localities, transparency is generally low. In the Me River, the average value of transparency ranges from 23.2 ±10.79 cm during the dry season to 32.57 ±9.55 cm during the rainy season. Seasonal variations in observed transparency would probably be due to the continuous input of suspended particulate matter via riparian populations.
In Agneby River, the mean transparency value ranges from 31.16 ±11.46 cm during the dry season to 30.93 ±14.61 cm during the wet season. These low values observed during both seasons are the result of domestic wastewater and also of strong water currents resuspending particles.
Physico-chemical parameters is an excellent indicator of water quality. In general, this study revealed a spatial and temporal variation in a few physico-chemical parameters measured in the Agneby and Me rivers. This study shows that most of the physico-chemical parameters (temperature, pH, salinity, conductivity, dissolved solids, resistivity, redox potential and transparency) vary little from season to season. However, seasonal variations are more pronounced. Overall, the analysis of the physico-chemical parameters revealed that the waters of the Agneby River localities are warm, neutral in pH, saline, relatively high quantities of dissolved substances, low electrical resistivity. On the other hand, on the Me River, the waters are less warm, with acid pH, low salinity, low quantities of dissolved solids and high electrical resistivity. Moreover, the waters are reductive due to the low levels of redox potential observed in both rivers and low transparency.
We are grateful to the research group directed by Pr. NGORAN Eliézer, Director of the Environment Vector Parasites Laboratory for the collect of the data on the study area and all its staff. Thanks are addressed to the village chiefs, the other local authorities and the study participants in the 24 villages. This study received financial support from the University of Georgia Research Foundation Inc., which is funded by the Bill & Melinda Gates Foundation for the SCORE projects (prime award no. 50816, sub-award no. RR374-092/5054156).
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| [13] | Degbey C., Makoutode M., Fayomi B. et De Brouwer C, La qualité de l’eau de boisson en milieu professionnel à Godomey en 2009 au Bénin Afrique de l’Ouest. JInt Santé Trav 2010. 1: 15-22. | ||
| In article | |||
| [14] | Koffi K.B, Diversité de l’ichtyofaune et écologie trophique de quelques espèces dans le complexe lagunaire Aby-Tendo-Ehy (Côte d’Ivoire). Thèse de Doctorat d’Hydrobiologie et Ecotechnologie des Eaux, UFR Biosciences, Université Félix Houphouët-Boigny, Abidjan, Côte d’Ivoire, 2015. 165 p. | ||
| In article | |||
| [15] | N’Zi K.G., Gooré Bi G., N’Douba V., Koné T., Kouamélan E.P. & Ollevier F, Diversité biologique des crevettes d’un petit bassin côtier ouest africain, rivière Mé, Côte d’Ivoire en relation avec les variables environnementales. Sciences et Techniques, Sciences naturelles et agronomie, 2003. 27 (1 & 2), 17-27. | ||
| In article | |||
| [16] | Konan Y.A. Diversité de l’ichtyofaune et caractéristiques bioécologiques de Thysochromis ansorgii (Boulenger, 1901) et Clarias buettikoferi Steindachner, 1894 dans la forêt des marais Tanoé-Ehy (Côte d’Ivoire). Thèse de Doctorat d’Hydrobiologie et Ecotechnologie des Eaux, UFR Biosciences, Université Félix Houphouët-Boigny, Abidjan, Côte d’Ivoire, 2014. 172 p. | ||
| In article | |||
| [17] | Chantraine J.M, la lagune Aby (Côte d’Ivoire): morphologie, hydrologie, paramètres physico-chimiques. Documents Scientifiques, Centre de Recherches Océanographiques, Abidjan, 1980. 12 (2): 30-77. | ||
| In article | |||
| [18] | Aboua B.R.D, Développement d’un indice d’intégrité biotique piscicole pour la préservation de la biodiversité du fleuve Bandama. Thèse de Doctorat d’Hydrobiologie et Ecotechnologie des Eaux, UFR Biosciences, Université Félix Houphouët-Boigny, Abidjan, Côte d’Ivoire, 2012. 227 p. | ||
| In article | |||
| [19] | Berté S, Biologie et écologie de Distichodus rostratus (Günther, 1864) dans un hydrosystème particulier en Côte d’Ivoire. Thèse de Doctorat d’Hydrobiologie et Ecotechnologie des Eaux, UFR Biosciences, Université Félix Houphouët-Boigny, Abidjan, Côte d’Ivoire, 2009. 180 p. | ||
| In article | |||
| [20] | Besson A., Seger M., Giot G., Cousin I, Time-scale analyse of the soil structure evolution within an agricultural field locally trafficked. Soumis à Geoderma, 2012. 29 p. | ||
| In article | |||
| [21] | De Villers J., Marianne S. & Catherine Y, Qualité physico-chimique et chimique des eaux de surface : cadre général Fiche 2 Institut Bruxellois pour la Gestion de l'Environnement, Observatoire des Données de l'Environnement, 2005. 16 p. | ||
| In article | |||
| [22] | Anonymous 2. Forum Interrégional des Lagunes Méditerranéennes, www.pole-lagunes.org. 2010 | ||
| In article | |||
| [23] | Pagès J., Dufour P. et L. Lemasson. Pollution de la zone urbaine de la lagune Ebrie (Côte d’Ivoire). Document scientifique centre recherche. Oceanographique, Abidjan, 1980. 11 (2) 79-107 | ||
| In article | |||
| [24] | Kouaménan M, Paramètres environnementaux de la lagune Ebrié (Côte d’Ivoire): Secteur IV et V. Mémoire de Master 2 d’Hydrobiologie et Ecotechnologie des Eaux, UFR Biosciences, Université Félix Houphouët Boigny, Abidjan, Côte d’Ivoire, 2015. 51 p. | ||
| In article | |||
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| In article | |||
| [13] | Degbey C., Makoutode M., Fayomi B. et De Brouwer C, La qualité de l’eau de boisson en milieu professionnel à Godomey en 2009 au Bénin Afrique de l’Ouest. JInt Santé Trav 2010. 1: 15-22. | ||
| In article | |||
| [14] | Koffi K.B, Diversité de l’ichtyofaune et écologie trophique de quelques espèces dans le complexe lagunaire Aby-Tendo-Ehy (Côte d’Ivoire). Thèse de Doctorat d’Hydrobiologie et Ecotechnologie des Eaux, UFR Biosciences, Université Félix Houphouët-Boigny, Abidjan, Côte d’Ivoire, 2015. 165 p. | ||
| In article | |||
| [15] | N’Zi K.G., Gooré Bi G., N’Douba V., Koné T., Kouamélan E.P. & Ollevier F, Diversité biologique des crevettes d’un petit bassin côtier ouest africain, rivière Mé, Côte d’Ivoire en relation avec les variables environnementales. Sciences et Techniques, Sciences naturelles et agronomie, 2003. 27 (1 & 2), 17-27. | ||
| In article | |||
| [16] | Konan Y.A. Diversité de l’ichtyofaune et caractéristiques bioécologiques de Thysochromis ansorgii (Boulenger, 1901) et Clarias buettikoferi Steindachner, 1894 dans la forêt des marais Tanoé-Ehy (Côte d’Ivoire). Thèse de Doctorat d’Hydrobiologie et Ecotechnologie des Eaux, UFR Biosciences, Université Félix Houphouët-Boigny, Abidjan, Côte d’Ivoire, 2014. 172 p. | ||
| In article | |||
| [17] | Chantraine J.M, la lagune Aby (Côte d’Ivoire): morphologie, hydrologie, paramètres physico-chimiques. Documents Scientifiques, Centre de Recherches Océanographiques, Abidjan, 1980. 12 (2): 30-77. | ||
| In article | |||
| [18] | Aboua B.R.D, Développement d’un indice d’intégrité biotique piscicole pour la préservation de la biodiversité du fleuve Bandama. Thèse de Doctorat d’Hydrobiologie et Ecotechnologie des Eaux, UFR Biosciences, Université Félix Houphouët-Boigny, Abidjan, Côte d’Ivoire, 2012. 227 p. | ||
| In article | |||
| [19] | Berté S, Biologie et écologie de Distichodus rostratus (Günther, 1864) dans un hydrosystème particulier en Côte d’Ivoire. Thèse de Doctorat d’Hydrobiologie et Ecotechnologie des Eaux, UFR Biosciences, Université Félix Houphouët-Boigny, Abidjan, Côte d’Ivoire, 2009. 180 p. | ||
| In article | |||
| [20] | Besson A., Seger M., Giot G., Cousin I, Time-scale analyse of the soil structure evolution within an agricultural field locally trafficked. Soumis à Geoderma, 2012. 29 p. | ||
| In article | |||
| [21] | De Villers J., Marianne S. & Catherine Y, Qualité physico-chimique et chimique des eaux de surface : cadre général Fiche 2 Institut Bruxellois pour la Gestion de l'Environnement, Observatoire des Données de l'Environnement, 2005. 16 p. | ||
| In article | |||
| [22] | Anonymous 2. Forum Interrégional des Lagunes Méditerranéennes, www.pole-lagunes.org. 2010 | ||
| In article | |||
| [23] | Pagès J., Dufour P. et L. Lemasson. Pollution de la zone urbaine de la lagune Ebrie (Côte d’Ivoire). Document scientifique centre recherche. Oceanographique, Abidjan, 1980. 11 (2) 79-107 | ||
| In article | |||
| [24] | Kouaménan M, Paramètres environnementaux de la lagune Ebrié (Côte d’Ivoire): Secteur IV et V. Mémoire de Master 2 d’Hydrobiologie et Ecotechnologie des Eaux, UFR Biosciences, Université Félix Houphouët Boigny, Abidjan, Côte d’Ivoire, 2015. 51 p. | ||
| In article | |||
