2.1.2. Extraction of leachates
Equal amounts of samples from three sites were taken and mixed homogenously. The 500 g of mixture was used for extraction. Three replicates were carried out. Samples were weighed and put into distilled water with a 1:1 ratio of sample:water (%, w:v), extracted on a horizontal oscillator with bubbling nitrogen for 6 h and then allowed to stand statically for 24 h. The leachates were first filtered (0.45 µm porosity filter paper) and then through a 0.22 μm membrane filter using a vacuum pump and then prepared for toxicity testing. The average pH of leachates was 6.98±0.16 for river sediment and 7.22±0.21 for paddy soil. The TOC was 1.86±0.64% for sediment and 2.86±1.26% for paddy soil.