Heavy Metals Pollution in Roadside Ecosystems

Abstract

Heavy metals refer to metallic elements that are characterized by having a relatively high density and they are toxic or poisonous even at low concentration. They are environmental pollutant owing to toxicity and longevity in atmosphere and ability to accumulate in living things via bioaccumulation. They tend to enter in different system such as food chain. Analyses of water, soil sediment and the surrounding growing plants (Cynodon dactylon and Cyperus species) for selected heavy metals (Cd, Pb, Zn and Cu) were conducted on a roadside pond located at Boko MSB, Dar es Salaam. Pond water, soil sediments and plant
samples were collected from Boko MSB site and treated using appropriate methods of acid digestion (aqua regia digestion) involving sample preparation and digestion and analyses for heavy metals and physical-chemical parameters using atomic absorption spectrometry (GBC XPLOOR AAS). Physical-chemical parameters of pond water such as pH, electrical conductivity, total dissolved solids and turbidity were measured. The concentration of Cd and Pb in the water sample were 0.0637 mg/L and 0.995 mg/L, respectively, while the physical-chemical parameters of the pond water indicated a pH of 7.55, electrical
conductivity of 184 µs. Based on the results of the study, the pond water is not safe for potable uses since it contains toxic heavy metals which are above WHO/TBS safe limit. The high concentration of the heavy metals was reflected in both the soil sediments and plants with Cd and Pb in soil samples being above safe limits while Cd, Pb, Zn and Cu in plant samples were also above safe limit.