BERBAGAI JENIS MODEL YANG DIGUNAKAN UNTUK SIMULASI PROSES DAN KEADAAN KESEKITARAN DIPERKENALKAN. MODEL LINEAR, BUKAN LINEAR, SATU ATAU BEBERAPA DIMENSI, MODEL PENYERAPAN FICKIAN, PUNCA TITIK, PUNCA SELANJAR, ALIRAN PALAM DAN CAMPUR PENUH DIBINCANGKAN. AN((THE DIFFERENT TYPES OF MODELS WHICH ARE USED IN SIMULATINGPROCESSES AND CONDITIONS IN THE ENVIRONMENT ARE INTRODUCED. LINEAR, NON-LINEAR, ONE AND MULTI-DIMENSION, PICKIAN DIFFUSION, POINT AND CONTINUOUS SOURCE, PLUG FLOW AND FULLY MIXED MODELS ARE DISC)