Nabarlek Pit decommissioning migration of sulphate, nitrate and radium ions in groundwater - preliminary modelling
Appleyard, S.
E-Publications; E-Books; PublicationNT; Report ; 41/1984
1984-04-01
Made available via the Publications (Legal Deposit) Act 2004 (NT).
Date:1984-04
English
Dept. of Transport and Works
Darwin
Report ; 41/1984
application/pdf.
Check within Publication or with content Publisher.
https://hdl.handle.net/10070/228496
https://hdl.handle.net/10070/674076
Technical Report WRD84041 Viewed at 14:07:09 on 29/07/2010 Page 16 of 34. I I I I I I I I I I I I I I I I I I I I I -------------~--------~~~--.,." The longitudinal dispersion coefficient can be determined from a breakthrough curve by the expression (Fried, 1975): where D L := longitudinal dispersion coefficient = distance when C/C o = 0.16 - distance when C/C - 0.84 o "C. := time (days) (m) (m) For the breakthroug~ curve in Fig 5.1: == 25m "0.84 10 = 250 to 465 days (Treloar, 1982) Assuming these values gives a dispersion ,- ~ , .t... COer.I:lClenl".. in the range 0.15 to 0.3 rn2jday. r,12 / day is assumed to apply t.o zone to the south east of the An average value of 0.2 the highly transmissive , ~ p..:... L-. The first order decay constant, ~, was assumed to be negligibly small. Breakthrough curves for conservative ions (apply to both nitrate and sulphate ions) under a variety of grounc\vater flm,; conditions are ShOVlD in Fig 5.2 (a) to (c). If the groundwater velocity derived from the finite element model (O.03m/day) is assumed, then the concentration distributions in Fig 5.2 (a) result. One "ea-" -..<= ... er a ,1 ,.!.,. aLI... seepage plume containing sulphate and nitrate ions enters the highly transmissive zone, the boundary between seepage water and natural groundwater will still be clearly defined. The seepaae Dulse ;,vill - ~ take about 55 years to cross the highly transmissive zone and reach Cooper Creek, by which time maximum concentrations of sulphate and nitrate ions will be about 20% of initial values {at first entry , .. lD,-O the h ' hl t .. .. "' t' 't) _ 19~ .. Y ranS~lSSlve zone, no,- .i..rom ne pl. . SA2/ll :TJ