Characterisation of Temperate Urban Lacustrine Surface-Sediments for Minerals and Metals in Comparison with Geochemical Indices and Sediment Quality Criteria

摘要

The present surface sediment assessment in two temperate lacustrine ecosystems in the region of anthro-urban intensification in less than a century of progressive human history identifies ecosystem responses through space-time monitoring of variable spectrum and their gradients. Sediments have almost no outliers in box-plots across the select sites that suggest their tranquil nature. But temporal fluctuations in pH, bicarbonates, conductivity, OC, OM, TN and C/N can be visualised during Ca-Si dominance. The estimated percentage elemental composition of surface sediments on dry weight basis revealed the order Si > Ca > Mg > K > Na > P > S > Cl. Besides, the micro and trace element quantification represent the descending series of Fe > Al > Zn > Mn > Cu > Cr > Ni > Co > As > Sn > Pb > Cd while Hg and Se remained below detection level (BDL). Sediment pH remained on the basic side but slight acidic nature is noticed during late summer. Significant correlation occurs for conductivity with organic C and organic matter (p < 0.01) as the latter serves an established source for nutrient ions. Similar is the case with sediment organic C, organic matter and total N as being complementary to one another. A general slight gradual decline in nutrient concentration till culmination of active macrophytic growth phase can be associated with active/passive bioaccumulation or anoxic release from sediments. The Enrichment Factor classifies each trace element into “No Enrichment” class to “Very High Enrichment” category. The Geochemical Index (Igeo) scale labels “Unpolluted” to “Highly Polluted” element groups in sediments. The construal of Contamination Factor differentiates between “Contaminated” and “Uncontaminated” score of elements. Integrated Pollution Index (IPI) and Pollution Load Index (PLI) also categorize the sites and lakes. Sediment Quality Guidelines (SQG’s) when compared to observed mean values for various elements point to pollution status and associated ecological risks involved.