The distribution of heavy metals and natural radionuclides within the surface sediments of the Juru River, Penang

This study was to assess the concentration levels of some heavy metals and natural radioactivities within the surface sediments collected along the Juru river at Penang from upstream to downstream. The elemental concentrations were measured using Neutron Activation Analysis (NAA) technique while natural radioactivities were quantified using HPGe gamma spectrometry. Using the continental crust value that normalized with iron concentration, enrichment for each element within the surface sediments was calculated. Overall, the enrichment appeared to be extremely severe for zinc, followed by severe enriched for arsenic and uranium, moderate enriched for antimony and thorium and no enrichment in elements barium, cobalt and chromium. Meanwhile, based on the radioactivity concentration in sediment, radiation risk was calculated using radium equivalent activity concentration index where three locations were found to have the index value higher than those recommended by UNSCEAR.The average elemental concentration found in the heavy metals of As, Ba, Co, Cr, Fe, Sb, Th, U, and Zn was 11.4 ppm, 297 ppm, 9.0 ppm, 128 ppm, 41400 ppm, 1.3 ppm, 36.3 ppm, 10.7 ppm and 1420 ppm, respectively. The enrichment factors (EFs) for zinc were between 3.5 to 80.5 with the average value of 20.2, whilst for the elements of arsenic and uranium, they were between 4.1 – 15.3 and 4.6 – 17.0, respectively. In antimony and thorium, the EFs were between 2.5– 9.4 and 1.9 – 9.6, respectively. EFs for barium, cobalt and chromium were less than 3.0. The activity concentration of 226Ra, 228Ra and 40K were found in ranges from 43 Bq/kg to 268 Bq/kg (mean 125 Bq/kg), 88 Bq/kg to 328 Bq/kg with a mean value of 165 Bq/kg and from 339 Bq/kg to 777 Bq/kg (mean 485 Bq/kg), respectively. The estimated radium equivalent index were between 199 – 792 Bq/kg and average of 395 Bq/kg which was exceeding the 370 Bq/kg suggested value by UNSCEAR.