Contamination Level of Arsenic and Cadmium in the Water and Sediments of a Fish Farm: Application of Contamination Indices

Abstract

Fish farming is widely practiced around the world. Fish is an important source of protein and contributes to the supply of highly nutritious animal protein in Côte d'Ivoire. Pollution of fish farms by toxic metals can lead to contamination of farmed fish. This study evaluates the content of trace metallic elements (TME), which are arsenic (As) and cadmium (Cd) in the water and sediments of a pond farm located in Abengourou in the east of Côte d'Ivoire. Water and sediment samples were collected from a dam and three ponds on the farm in September and October 2020. These samples were analyzed using an atomic absorption spectrophotometer. All data was processed using STATISTICA 7.1 and was used to calculate Metal Pollution Index (MPI), Ratio Sediment/Water (R<SUB>S/W</SUB>), Contamination Factor (CF), the pollution load index (PLI), the individual potential risk index (Er) and the ecological risk index (PERI) in order to assess the level of metal contamination of the fish farm. The mean concentrations of metallic trace elements are higher in the sediments (As: 0.2045±0.218496 - 0.3950±0.1103 mg/kg; Cd: 0.0565±0.0148 - 0.0880±0.0212 mg/kg) than in water (As: (0.1837±0.0148) × 10^-2 - (0.2296±0.0300) × 10^-2 mg/L; Cd: (0,1150±0.0129) × 10^-2 - (0.1250±0.0076) × 10^-2 mg / L). Sediments also have the highest overall metal contents. However, MPI<1 in both sediment and water. The CF (As=0.102±0.109 - 0.198±0.055; Cd=0.565±0.148 - 0.880±0.212) showed that the sediments were not contaminated. The PLI (0.253±0.062 - 0.335±0.090) indicated that the sediments on the fish farm were not polluted. In addition, Er (As: 1.02±1.09 - 1.98±0.55; Cd: 16.95±4.44 - 26.40±6.36) and PERI (18.93±4.99 - 27.59±7.57) showed that the sediments do not pose an ecological risk to farmed fish. However, R<SUB>S/W</SUB>>1 showed strong mobility of TMEs from water to farm sediments. The concentrations of trace metal elements assayed in the samples were below the recommended standard for freshwater aquaculture. The CF, PLI, Er and PERI indices indicate a low degree of contamination, pollution and a low ecological risk. However, R<SUB>S/W</SUB> indicate high mobility of TME from water to sediment.