Assessment of contamination level, pollution risk and source apportionment of heavy metals in the Halda River water, Bangladesh

This study demonstrates the level of heavy metal pollution in the Halda River, the only natural breeding source of carps in Bangladesh. Water was collected from 12 different sampling points along the Halda River. Water at various locations was found satisfactory in terms of the assessed physicochemical parameters (pH, electrical conductivity, and total dissolved solids). The presence of various cations and anions was also studied using ion chromatography. Atomic absorption spectroscopy was used to identify and quantify various heavy metals in the collected water samples. Among the heavy metals, Cd, Cr, Fe, Pb, Cu, and As concentration exceeded the safe limit suggested by WHO. The calculated heavy metal pollution index and metal index were found higher than the critical index value. The single-factor assessment (P (i)) and Nemerow's multi-factor index (P (N)) of heavy metals was calculated to find out the degree of pollution in the Halda River. The maximum values of P (i) (Cd), P (i) (Pb), P (i) (As), P (i) (Cu), and P (i) (Cr) were determined to be 26.67, 260.00, 17.00, 208.76 and 2.80 respectively. The maximum value of P (N) was found to be 289.04. The discharge of effluents from various large and small industries near the Halda River is considered to be the major source of the identified heavy metals. Multivariate statistical analysis such as principal component analysis, Pearson correlation matrix and cluster analysis revealed that most of the heavy metals originated from different anthropogenic sources. Multivariate analysis also showed that Co, Mn, Cu, Cr, Pb, Cd, NH(4)(+), NO(3)(-) mainly came from artificial sources whereas Fe, Ca, As mainly originated from natural sources. Arsenic (As) also came from artificial sources with Cu.