Effects of Trace Elements on Arylsulfatase Activity in Soils

Studies to evaluate the effects on arylsulfatase activity of 21 trace elements showed that all elements inhibited the activity of this enzyme in soils. Results showed that the relative effectiveness of trace elements in inhibition of arylsulfatase activity depends on the soil. When the trace elements were compared by using 25 μmole/g soil, the average inhibition of arylsulfatase in the four soils studied showed that Ag(I), Hg(II), B(III), V(IV), and Mo(VI) were the most effective inhibitors (average inhibition>50 percent) and that Fe(II) was the least effective (average inhibition <10 percent). Other trace elements that inhibited arylsulfatase in soils were: Cu(I), Cd(II), Sn(II), Zn(II), Cu(II), Ba(II), Mn(II), Ni(II), Pb(II), Co(II), Cr(III), Al(III), Fe(III), As(III), Se(IV), Ti(IV), As(V), and W(VI). Among these elements, Cu(II) and Fe(III) were more effective than Cu(I) and Fe(II), respectively. But As(V) was somewhat less effective than As(III). Generally, the inhibitory effect of the trace elements studied decreased when the amount of trace element added per gram of soil decreased by 10-fold (from 25 μmoles to 2.5 μmoles). The inhibition by MoO42-, WO42-, AsO43-, and PO43- showed competitive kinetics. Related anions, such as NO2-, NO3-, Cl-,SO42-, did not inhibit arylsulfatase activity in soils.