Journal of North Khorasan

Introduction:       The high  concentration   of nitrate  in water  is one of the pollutants  in ground  waters. In recent years  due to the increase  of wastewater  and agriculture  and urban  development,   its amount in water  source  has  been  increased.  High  nitrate  concentration   in drinking  water  is dangerous   for children's  health  and causes  Methemoglobinomia.    The aim of this research  was measure  the nitrate concentration   in  water  wells  which   supply  the  drinking   water  in Bojnord   and  compare   it  with ommon  standards.

Marerials    and  Methods:    This  was  a descriptive   research   to  investigate   nitrate  concentration   in vater sources  in Bojnord  in 2007. Thus the result  of nitrate  tests was considered  in 82 samples  from water  supplying  source  and  drinking  water  reservoirs   in Bojnord.  All  the  samples  were  tested  by using   spectrophotometric     methods    in  the   chemistry    lab   of  Northern    Khorasan's     Water   and wastewater  Company.  The final results  were studied  and analyzed  by statistical  methods.

Results:  The results  showed  that there was a significant  difference  between  concentration   of nitrate ions  in  inner   wells   and   concentration    of  nitrate   ions   in  outer   wells   (P=0.003).   The   average oncentration   of nitrate  ions  in inner  wells  was  higher  than  those  of the  outer  wells.  The  average itrate concentration   indicated  that 2 from  8 (25 %) outer  water  wells  and  8 from  9 (88.8  %) inner vater  wells   had   an  average   higher   than  the  standard   specified   by  Iranian   Standard   Industry esearch Institute.  It was shown that there was a significant  negative  relationship  between  the depth of well  and  nitrate  concentration   (P<O.OOl). The  average  of nitrate  concentration   in the  outlet  of

eservoir  was 34.4 mg/I.

Disscussion:    According  to the results,  the average  of nitrate  concentration   in many  drinking  water vells  of  Bojnord   was  more  (50  mg/I)  than  the  standard   approved   by  Institute   of  Standards   & dustrial  Research  of Iran. Because  of health  threats  of high nitrate  in drinking  water  wells,  some asic measures  should  be taken  such as refining  water  of polluted  wells  or taking  out polluted  wells om  consumption   cycles  and  using  better  quality   sources.   Regular   examination   and  control  of

itrate in supplying  sources  and water  distribution  nets is also necessary.