Distribution of heavy metals (arsenic, cobalt, copper and zinc) composition and bacterial communities in sediments along tropical river east coast Malaysia

Sediment samples were collected from 19 sampling stations of Pahang River, east coast Malaysia to determine the concentration of arsenic (As), cobalt (Co), copper (Cu), zinc (Zn) and bacterial colony forming unit (CFU) distribution. Sampling was conducted during pre and post of North-East monsoon season for the years 2013 and 2022. Heavy metal concentrations were determined by using inductively coupled plasma mass spectrometry (ICP-MS). The concentration of heavy metals was compared with the world average concentration of shale values. The dry weight concentration of As ranged between 4.387 ± 0.586 to 15.922 ± 8.738 μg·g–1 during pre-monsoon. While it was 3.989 ± 0.758 to 11.336 ± 6.748 μg·g–1 during post-monsoon. The range of dry weight concentration for Co was found between 1.730 ± 0.318 and 4.569 ± 0.586 μg·g–1 during pre-monsoon while 1.476 ± 0.063 and 4.620 ± 0.951 μg·g–1 during post-monsoon. The dry weight concentration of Cu ranged between 1.182 ± 0.510 to 10.722 ± 5.664 μg·g–1 and 0.900 ± 0.222 to 6.514 ± 3.749 μg·g–1 during pre-monsoon and post-monsoon, respectively. The range dry weight concentration for Zn was found between 7.964 ± 4.857 and 26.289 ± 2.636 μg·g–1 during pre-monsoon while 8.187 ± 3.010 and 28.347 ± 15.665 μg·g–1 during post-monsoon. The bacterial community in sediments along Pahang River was determined using culture-based method. The bacterial CFU range was found between 1526.67 ± 64.68 and 16146.67 ± 225.71 CFU/g during pre-monsoon while 1013.33 ± 38.51 and 28826.67 ± 418.47 CFU/g during post-monsoon. This study revealed that the concentration of heavy metals does not influence the distribution of bacteria in the Pahang River sediments. Even though the concentrations of heavy metals studied are typically below reported toxic levels, ongoing monitoring of river ecosystems is an essential to safeguard this ecosystem and ensure that the pollution from heavy metals is under conducive condition throughout these increased industrialization and urbanization.