Alligator Rivers region regional surface water quality monitoring : November 1978 - April 1981
Alligator Rivers Region - Regional Surface Water Quality Monitoring, Volumes 1,2,3 (Plus draft)
Northern Territory. Department of Transport and Works. Water Division, Environmental Section
E-Publications; E-Books; PublicationNT; Report ; 49/1983
At head of title: Water Division, Dept. of Transport & Works, Northern Territory. "April 1983".
Water quality -- Northern Territory -- Alligator Rivers Region; Hydrology -- Northern Territory -- Alligator Rivers Region
Northern Territory Government
Report ; 49/1983
3 volumes. ; 30 cm
Attribution International 4.0 (CC BY 4.0)
Northern Territory Government
https://hdl.handle.net/10070/672725 [Alligator Rivers region regional surface water quality monitoring : November 1978 - April 1981 - WRD83049_v_1.pdf]; https://hdl.handle.net/10070/672727 [Alligator Rivers region regional surface water quality monitoring : November 1978 - April 1981 - WRD83049_v_2.pdf]; https://hdl.handle.net/10070/672729 [Alligator Rivers region regional surface water quality monitoring : November 1978 - April 1981 - WRD83049_v_3.pdf]
Technical Report WRD83049 Viewed at 14:07:10 on 29/07/2010 Page 35 of 440. I I I I I I I I I I I I I I I I I I I I 34 . Tl'.BLE 6.3 cont. 14. After weighing, the residue is dissolved in 10 ml of dilute acid and the sulphate determinated by auto-analysis using APHA method 607. 15. Silica - this is ah~ays determined on the unfrozen sample following the introduction of frozen and unfrozen samples. The reasons for this are set out in a separate note. The method used initially was the Heterpoly blue method given in the APHA as 426C. Recently, the determination has been made on the auto analyser using Technicon II method 186-72W uses a similar reaction. Considerable cross checking has shown that both methods give identical results. 16. The remaining determinations are usually made on the thawed unfiltered sample. 17. Calcium, magnesium, sodium and potassium are determined by ~ . b ~. a~onuc a sorp~~on. 18. Chloride by APHA method 408C. 19. Fluoride by selection ion electrode by method APHA-414B. 20. Arsenic. A 10 fold concentration by evaporation with nitric - perchloric acid is made and the total arsenic determined by evolution as hydride using atomic absorption measurement similar to the APHA procedure 301A part VII. The modification used is the method of Thompson, K.C. and Thomerson, D.R., Analyst Vol.99 September 1974 pp 595 601, which uses sodium borohydride as reductant in preference to a zinc slurry and a heated silica tube in preference to a flame. This enables a better detection limit to be achieved. 21. Nitrate. Initially nitrate was determined after the nitrite determination by placing a cadmium column into the analyser and reading the samples again. However, ~,is is not always convenient and often the nitrates have been read later when reading the sulphates on the auto analyser. Cross-checking has shown there is no difference caused by making the determination a few days after the opening of the container. 22. Checking correctness of analysis - this has been done using APa~ procedure 104C. The anion-cation balance has been maintained at less than 0.05 milliequivalents whereas the APHA procedure accepts a difference of at least 0.1 for fresh water.