Distribution, Source Identification, and Ecological Risk Assessment of Selected Trace Elements in Sediments from Manchar Lake, Pakistan

Abstract

ABSTRACT Preserving the ecological health of wetlands has enormous importance in an arid climate. Manchar Lake, located in the arid part of Pakistan, is one of the most vulnerable freshwater lakes and has continuously been exposed to direct pollutants influx. Its vulnerability demands an assessment of pollution loads of trace elements in bed sediments. This study was carried out with sediment samples from 21 locations. Nine trace elements (As, Pb, Fe, Cr, Hg, Cu, Ni, Mn, and Zn) were detected using Inductively Coupled Plasma Mass Spectrometry. Pollution load-related analytical approaches were applied to estimate the contamination loads of individual elements and the aggregated ecological risks. Overall, the mean concentrations of all trace elements in lakebed sediments were detected as: As 5.4, Pb 2.2, Cr 17, Cu 1.5, Fe 165.1, Hg 0.028, Mn 2.6, Ni 7.5, and Zn 64.9 in mg/kg. Results revealed that the lakebed sediment is significantly polluted, primarily with Fe, Zn, Hg, Cr, and As. The spread of these trace elements also varies across locations as many locations do not receive polluted water during dry seasons due to the low water level in the lake. The ecological risk assessment and multivariate analysis findings establish that the Main Nara Valley Drain comprising drainage water from agricultural fields and in part from municipalities is the greatest pollution source to the lake. This dangerous pollution problem calls for action to restore the purity of the natural lake ecosystem.