Effect of Papyrus (Cyperus Papyrus) On The Water Quality In Yala Swamp And Lake Sare, Siaya County, Kenya

Abstract

Access to safe water is a fundamental need and basic human right. Wetlands around the globe are being modified, reclaimed and overexploited due to high levels of resource consumption and land conversion that alter the quality of water. Yala swamp, the largest fresh water wetland in Kenya supports a large biodiversity and part of this wetland has been converted into large-scale agriculture resulting into a conflict and controversy amongst key stakeholders. The papyrus being destroyed to create room for agriculture are important because they help in adsorbing contaminants in their tissues, increasing the residence time of water and filter contaminants like heavy metals thus cleaning the water. Despite this role of papyrus in phytoremediation the information is limited, lacks supportive evidence and the empirical aspect on the levels of these pollutants in relation to the papyrus biomass is limited. The main objective of this study was to determine the effects of papyrus reeds on the water quality in Yala Swamp and Lake Sare. The specific objectives were to; determine the variation of physicochemical parameters (Temperature, Dissolved Oxygen (DO), pH, Biological Oxygen Demand (BOD), Total Suspended Solids (TSS), Turbidity, Electrical conductivity (EC) and Total Dissolved Solids (TSS), investigate the levels of nitrate s and phosphates in water and sediments, examine the levels of heavy metals (Pb, Zn, Cu and Fe) in water and sediments and to analyze the bioaccumulation of these heavy metals in the tissues of papyrus in River Yala, Yala swamp and Lake Sare. The study adopted a longitudinal sectional design. Six sampling sites were selected where samples were collected in triplicates during the wet and dry seasons (May and September 2015 respectively). Data on physicochemical parameters were obtainedinsitu using a muiltimeter model (YSI 556 MPS Multimeter USA). Data on nitrates and phosphates were determined using Ultraviolet spectrometry and data on heavy metals determined by use of Atomic Absorption Spectrophotometer. Statistical analysis was done using SAS V9.0 software while levels of significance determined using one way ANOVA at p ≤ 0.05 and Duncan Multiple Range test (DMRT) for separation of means. Student’s t-test was used to determine the difference between the values in the dry and wet seasons. Mean temperature was 26.19±0.710C, DO:3.72±1.02Mg/l, BOD:3.9±0.32Mg/l, pH:7.52±0.17, TDS:109±86.33, EC:173.26±13.8 µS/cm, TSS: 12.42±18.51 Mg/l and Turbidity: 12.29±10.03 NTU. The values varied significantly at P<0.05 among all the sites. The values for nitrates and phosphates also varied significantly in both water and sediments in all the sites at P˂ 0.001 but there was no significant difference in the values of phosphates in the two seasons (Student’s t-test p=0.1772). The values for heavy metals; lead, copper, zinc and iron varied significantly among all the sites in water and sediments at P˂ 0.001. Similarly there was no significant difference in the values of the heavy metals in the two seasons (Student’s t-test P˂0.05). The sequence from highest was Fe ˃ Pb ˃ Zn ˃ Cu. However, the values were above the guideline limits for drinking water and aquatic life as per NEMA and USEPA standards. The concentrations of all the heavy metals in sediments were higher in sediments than in water which confirmed the capacity of sediments to accumulate heavy metals compared to freely moving water bodies. The heavy metals were also determined in the tissue of papyrus i.e. the stems, flowers roots and rhizomes. The levels were higher in roots than stems and flowers except for Zn and Pb that were high in stems than roots. This is a further proof of confirmation of phytoremediation by the papyrus. The results show that papyrus is useful in biological monitoring of heavy metal contamination in water bodies. The study will assist in conservation of the papyrus to help phytoremediate pollutants from Dominion farms and the adjacent farms in order to have ecologically sound wetland.