Lanthanum in freshwater and marine water

Toxicant default guideline values for protecting aquatic ecosystems

October 2000

Extracted from Section 8.3.7 ‘Detailed descriptions of chemicals’ of the ANZECC & ARMCANZ (2000) guidelines.

The default guideline values (previously known as ‘trigger values’) and associated information in this technical brief should be used in accordance with the detailed guidance provided in the Australian and New Zealand Guidelines for Fresh and Marine Water Quality.

Description of chemical

Lanthanum is one of the rare earth elements, which includes all elements between lanthanum and lutetium. Its molecular weight is 138.9. Trace quantities of rare earth elements are applied to many crop species in the People’s Republic of China to enhance plant growth. In 1993 over 1000 tonnes of rare earth elements were applied as fertiliser to over 1 million hectares in China (Barry & Meehan 1997). Their value for Australian agriculture is currently being investigated (Buckingham et al. 1997).

Concentrations of lanthanum have been measured in water associated with mining activities in northern Australia (Milne et al. 1992, Noller 1994). Lanthanum concentrations up to 3500 µg/L were found in mine sump waters from Pine Creek Gold Mine and up to 230 µg/L in tailings waters (Noller 1994). Other rare earths were also found at high concentrations. Lanthanum at concentrations above 1 mg/L tends to precipitate as the hydroxide. It has many chemical and physical characteristics that are similar to calcium (Barry & Meehan 1997). The current analytical practical quantitation limit (PQL) for lanthanum is 0.01 µg/L in fresh water and 0.3 µg/L in marine water (NSW EPA 2000).

Aquatic toxicology

The only toxicity data for lanthanum was for the Australian Daphnia carinata, reported by Barry and Meehan (1997). This has not yet been peer reviewed but is reported for information.

The 48-hour EC50 values for lanthanum to D. carinata at pH 7.5 to 7.8 were 43 µg/L in dechlorinated Melbourne tap water (22 mg/L CaCO₃), 49 µg/L in synthetic pond water (98 mg/L CaCO₃) and 1180 µg/L in Australian Standard Test Method (ASTM) hard water (160 mg/L CaCO₃).

Chronic NOEC levels for lanthanum to D. carinata varied from 100 to 200 µg/L, higher than acute values.

Guideline

An environmental concern level (ECL) (refer to Section 8.3.4.5 of the ANZECC & ARMCANZ 2000 guidelines) of 0.04 µg/L could be used as a low reliability freshwater trigger value for lanthanum. This was calculated using an assessment factor (AF) of 1000. This figure should only be used as an indicative interim working level. No marine data were available. As this is below the analytical practical quantitation limit (PQL), any detection may warrant investigation.

References

ANZECC & ARMCANZ 2000. Australian and New Zealand Guidelines for Fresh and Marine Water Quality, Australian and New Zealand Environment and Conservation Council and Agriculture and Resource Management Council of Australia and New Zealand, Canberra.

Barry MJ & Meehan B 1997. Toxicity of the rare earth element lanthanum to Daphnia. Poster P3 in Proceedings, 4th Annual Conference of the Australasian Society for Ecotoxicology, Brisbane, July 1997. Australasian Society for Ecotoxicology, Sydney.

Buckingham SD, Maheswaran J, Meehan BJ & Peverill KI 1997. The role of applications of rare earth elements in enhancement of crop and pasture production. Journal of the Rare-Earth Society of Japan 31:11, 69-85.

Milne FJ, Hunt RJ, Noller BN & Woods PH 1992. A review of water management issues at Pine Creek Gold Mine. Environmental Technical Report 92/1, Mines Environment Directorate, Department of Mines and Energy, Darwin NT.

Noller BN 1994. The identification of constituents in waste waters from gold mining using ICP-MS. International Journal of Surface Mining, Reclamation and Environment 8, 95-99.

NSW EPA 2000. Analytical Chemistry Section, Table of Trigger Values 20 March 2000, LD33/11, Lidcombe, NSW.