SOIL CONDITIONS AS AFFECTED BY TANNERY WASTE WATERS

Abstract

1. Eight  samples  of  tannery  effluents,  twenty-three  samples  of  soil  drawn  from  eight  profile  pits  (six  located  in  the  belt  of  land  affected  by  the  tannery  effluent  and  two  located  in  the  adjoining  fertile  belt  of  land),  four  samples  of  sub-soil  water  from  the  profile  pits  in  the  affected  belt,  three  samples  of  water  from  the  wells  in  the  arca  and  a  sample  of  water  from  the  lake  in  the  neighbourhood  were  examined  and  the  results  are  given.
2. Analysis  of  the  tannery  effluents  has  shown  that  they  invariably  contain  high  amounts  of  salts,  particularly  sodium  chloride,  and  also  toxic  elements  such  as  chromium  and  arsenic.  They  possess  the  characteristics  of  tannery  wastes  in  general.
3. Studies  on  the  soil  samples  from  the  affected  belt  have  shown  that  they  contain  high  amounts  of  water-soluble  salts,  especially  sodium  chloride;  that  they  also  contain  the  toxic  constituents,  viz.,  chromium  and  arsenic;  that  their  mechanical  texture  has  been  adversely  affected  especially  with  regard  to  porespace  and  water-holding  capacity;  that  sodium  clay  has  formed  and  in  consequence  lime  has  been  leached  out;  that  the  soil  has  become  alkaline  and  the  degree  of  alkalisation  is  over  50%.  The  soils  from  the  fertile  belt  lying  on  either  side  of  the  affected  belt  have  shown  the  normal  characteristics  of  a  healthy  soil.
4. The  results  of  analyses  of  sub-soil  waters  lend  further  evidence  that  the  reactions  mentioned  above  have  taken  place  in  the  soil.
5. Analysis  of  the  irrigation  water  from  the  lake  has  not  revealed  any  unusual  feature,  its  composition  being  that  of  good  irrigation  water.  So  its  use  for  crop  irrigation  cannot  produce  any  adverse  effect  on  soil  conditions.  The  deterioration  of  the  soil  noticed  could  only  be  due  to  some  factor  other  than  the  use  of  the  irrigation  water.
6. The  results  of  the  analytical  studies  and  related  evidence  clearly  show  that  the  waste  waters  from  the  tannery  have  been  responsible  for  the  deterioration  of  the  soil  in  the  affected  belt  of  land  and  for  the  failure  of  crops