Auto-correlograms and auto-regressive models of trace metal distributions in Cochin Backwaters

Abstract

Auto-correlation technique has been applied to study fluctuations in concentration profiles of chemical species in Cochin Backwaters (Kerala, India). No stability in time can be detected for particulate Mn at all stations, for Fe at stations 1,2 and 3 and for Zn at stations 1 and 4. The stability in time for the concentration profiles increases as Fe ~ Mn < Zn < Ni ~ Cu ~ Co. The fraction of variability in the variables obtained by the auto-regressive model of order 1 ranges from 20 to 50%. Auto-regressive model of order 1 can give the concentration of majority of metals at any time point, given the concentration at a previous time point in station 3. Stability in time for the concentration profile is followed by the presence of isopattern. Very low values of <i>Tx</i> indicate absence of isopattern and for such metals it is found that there is no stability in time.