Nabarlek Pit decommissioning migration of sulphate, nitrate and radium ions in groundwater - preliminary modelling
E-Publications; E-Books; PublicationNT; Report ; 41/1984
Made available via the Publications (Legal Deposit) Act 2004 (NT).
Dept. of Transport and Works
Report ; 41/1984
Check within Publication or with content Publisher.
Technical Report WRD84041 Viewed at 14:07:09 on 29/07/2010 Page 12 of 34. 1-- -----~-~-----,--".- .. ----.-..... I I I I I 1 1 I I I I I I I I I I 1 I I_.~~ 5. ESTIMATES OF NITRATE AND SULPHATE LOADS IN COOPER CREEK Unlike the situation for radium, sulphate and nitrate ions are not adsorbed by mineral surfaces to a significant extent and so the transport velocities of these ions are much higher than for Ra. SUlphate and nitrate ions probably move at the same rate as groundwater here. AGC (1984) have estimated that 35 m3/day of water will seep from the pit during rehabilitation, and that groundwater will have a velocity of about 0.02 - 0.6 m/day to the south east. Therefore, the time required for sulphate and nitrate ions to reach Cooper Creek via groundwater transport from the pit will be in the order of 5-140 years. In order to assess the effect of nitrate and sulphate ions seeping into Cooper Creek from the pit, background levels of these ions in Cooper must be knm"n. Total loads of nitrogen (nitrate, nitrite ammonia and organic nitrogen) and SUlphate in loads for the wet seasons between 1978 and 1981 are tabulated below, month of flow. together ,vi th loads carried in the first WET SEl'.50N 1978/79 1979/80 1980/81 TCP.J\L N (xl0 3 Kg) 0.34 2.84 0.73 SlILPFXl'E (xl0 3 kg) 1. 75 16.3 10.42 TGTAL N (xl0 3 kg) 7.70 28.2 2.29 SlT.LPH1'"TE (x10 3 kg) 28.9 66.1 112 The greatest impact that water seeping from the pit could have on Cooper Creek, would be if evaporation during the dry season concentrated soluble nitrate and sulphate salts in creek sediments whioh were then flushed out in the first flow of the subsequent wet season. SA2/11 :TJ W4U~ ,h + --*-- -41,