Individual denitrification experiments were performed
in anaerobic (sealed) batch systems prepared in
125 ml serum bottles. The initial nitrate concentrations
ranged from 50 to 400 Each 125 ml sample of
50, 100, 200 and 400 mg NO
ÿ
3 /l aqueous solution and 0.5
g of dry iron particles was charged into 125 ml serum
bottles capped with a crimpstyle Mininertä valve. In
most cases, the bottle was mixed on a rotary shaker
(Glas-Col) with 60 rpm under ambient conditions. Periodically,
1 ml of the aqueous solution was withdrawn
by a 1 ml glass syringe into a 2 ml vial and then passed
through a 0.45 lm membrane ®lter. The concentrations
of unreacted nitrate (NO
ÿ
3 ) were determined by UV
spectrophotometer (UV2100, Shimadzu). Control experiments
containing no Fe0 particles were also prepared.
Oxygen was removed by purging argon gas into
the nitrate solution as well as into headspace of the serum
bottle.