KEMAMPUAN TANAMAN AIR PURUN (Lepiromia micronata) DALAM MENYERAP LOGAM BERAT (Pb, Cu dan Zn) DI BEKAS PENAMBANGAN TIMAH - UMROH, UMROH (Department of Aquatic Resources Management, Faculty of Agriculture, Fisheries, and Biology, University of Bangka Belitung, 2018)