Barium

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

experimental and analytical accomplishment: April 18, 2016 - April 21, 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Series on Testing and Assessment No. 29 (23-Jul-2001): Guidance document on transformation/dissolution of metals and metal compounds in aqueous media

Principles of method if other than guideline:

The OECD Series 29 requires a limit of 20 % and 10 % for the between-vessel and the within-vessel variation, respectively. The observed variations within and between test vessels for the barium concentrations with a loading of 100 mg test item/L at pH 6 and 8 are mostly in compliance with the test guideline after one day of testing, except between-vessel variation at pH 6 (43.2 %). A lower Ba concentration has been quantified in vessel 5 compared to other Ba treatments at pH 6 (Table 1, Table 8) resulting in this increased between-vessel variation. The lower Ba concentration in vessel 5 compared to the other Ba treatments at pH 6 corresponds with a higher pH in this vessel after 24h (pH 8.9) compared to the other vessels with the same treatment (pH 8.1).

GLP compliance:

yes (incl. QA statement)

Other quality assurance:

other: The Quality Assurance Unit of the test facility

Remarks:

inspected the study, audited the final report, and reported possible findings to the Study Director and to the management

Type of method:

flask method

Specific details on test material used for the study:

Test item name:Barium metalTrade name:Bariummetall, Stangen unter Paraffinöl –Sr max. 1.6 %CAS-Number7440-39-3EC-Number:231-149-1Chemical formula:BaMolecular weight:137.33 g/molAppearance:Metal rods in paraffin oil Lot/Batch Number:72893Purity:Ba incl. Sr 99.9 % [according to CoA]Sr 0.6 % [according to CoA]Storage: Store dry in original tightly closed container at a well-ventilated cool place. Keep and transport under petroleum or argon. Protect from humidity, water and heat. Prevent from air / oxygen. Do not store together with acids, alcohols. Incompatible with oxidizing agents.Stability:Stable under storage conditionsOrigin of the test item:Rockwood Lithium GmbHIndustriepark Höchst, Gebäude G87965926 Frankfurt a.M:GermanyWaste disposal:Waste will be disposed of in accordance with federal, state and local environmental control regulations.Date of receipt:March 11, 2016Expiry date:n.A.General preventive measures: Non-flammable protective clothing, gloves, eye protector.

Key result

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

18.11 mg/L

Element analysed:

barium metal

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

The OECD guidance document 29 requests the performance of the test at a pH which maximizes the dissolution. The sponsor decided to perform the test at pH 6 and 8 to cover acidic as well as basic conditions in environment. As requested the test was conducted with a loading of 100 mg/L over 24 hours and one sampling after one day because barium is expected to “ […] undergo either dissolution or rapid transformation such that [its] ecotoxicity potential is indistinguishable from soluble forms”. The test was performed in triplicate vessels (agitation at 100 rpm, 21.5 ± 1.5 °C) and duplicate samples per vessel, this includes method blanks (same procedure but without test item).

Key result

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

69.33 mg/L

Element analysed:

barium metal

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

The OECD guidance document 29 requests the performance of the test at a pH which maximizes the dissolution. The sponsor decided to perform the test at pH 6 and 8 to cover acidic as well as basic conditions in environment. As requested the test was conducted with a loading of 100 mg/L over 24 hours and one sampling after one day because barium is expected to “ […] undergo either dissolution or rapid transformation such that [its] ecotoxicity potential is indistinguishable from soluble forms”. The test was performed in triplicate vessels (agitation at 100 rpm, 21.5 ± 1.5 °C) and duplicate samples per vessel, this includes method blanks (same procedure but without test item).

Details on results:

Oxygen levels (Table 7) as well as the mean temperature (see sections 5.1, 5.2) are in compliance with the requirements of the OECD guidance document 29 (4). In solutions containing 100 mg/L of the test item at pH 8 and 6, the pH increased after 6 h up to 11.1 and 10.6, respectively. After 24 h pH decreased to 8.1 – 8.9 (starting pH of 6) and 7.9 – 8.0 (starting pH of 8). Method blanks remained relatively stable in the range of 6.0 – 6.4 and 7.7 – 8.0 (see Table 7). Under the described conditions of this test with barium metal at a loading of 100 mg/L, dissolved barium concentrations were 18.11 ± 0.54 mg/L in media at pH8 and 69.33 ± 29.94 mg/L (1 d) in media at pH 6 after 24 h (1 d).During the 24 h of testing Ba completely reacts with water in a short time frame and there is no (visual) evidence of remaining Ba metal after 24h. In a first instance it dissolves to Ba(OH)2, resulting in an increase of pH, and then precipitates as BaCO3. The difference in measured dissolved Ba concentrations between the pH 6 and pH 8 media is driven by the difference in buffer capacity and different potential for carbonate precipitation.The OECD Series 29 requires a limit of 20 % and 10 % for the between-vessel and the within-vessel variation, respectively. The observed variations within and between test vessels for the barium concentrations with a loading of 100 mg test item/L at pH 6 and 8 are mostly in compliance with the test guideline after one day of testing, except between-vessel variation at pH 6 (43.2 %). A lower Ba concentration has been quantified in vessel 5 compared to other Ba treatments at pH 6 (Table 1, Table 8) resulting in this increased between-vessel variation. The lower Ba concentration in vessel 5 compared to the other Ba treatments at pH 6 corresponds with a higher pH in this vessel after 24h (pH 8.9) compared to the other vessels with the same treatment (pH 8.1).

Conclusions:

Under the described conditions of this test with barium metal at a loading of 100 mg/L, dissolved barium concentrations were 18.11 ± 0.54 mg/L in media at pH8 and 69.33 ± 29.94 mg/L (1 d) in media at pH 6 after 24 h (1 d).

Executive summary:

The OECD guidance document 29 requests the performance of the test at a pH which maximizes the dissolution. The sponsor decided to perform the test at pH 6 and 8 to cover acidic as well as basic conditions in environment. As requested the test was conducted with a loading of 100 mg/L over 24 hours and one sampling after one day because barium is expected to “ […] undergo either dissolution or rapid transformation such that [its] ecotoxicity potential is indistinguishable from soluble forms". The test was performed in triplicate vessels (agitation at 100 rpm, 21.5 ± 1.5 °C) and duplicate samples per vessel, this includes method blanks (same procedure but without test item).

 

Solution pH and oxygen concentrations were recorded after 2 h, 6 h and 24 h. Total dissolved barium concentrations were measured in samples taken after 24 h.

 

Final results:

Oxygen levels (Table7) as well as the mean temperature (see sections5.1,5.2) are in compliance with the requirements of the OECD guidance document 29(4). In solutions containing 100 mg/L of the test item at pH 8 and 6, the pH increased after 6 h up to 11.1 and 10.6, respectively. After 24 h pH decreased to 8.1 – 8.9 (starting pH of 6) and 7.9 – 8.0 (starting pH of 8). Method blanks remained relatively stable in the range of 6.0 – 6.4 and 7.7 – 8.0 (see Table7).

 

Under the described conditions of this test with barium metal at a loading of 100 mg/L, dissolved barium concentrations were 18.11 ± 0.54 mg/L in media at pH8 and 69.33 ± 29.94 mg/L(1 d) in media at pH 6 after 24 h (1 d).

 

During the 24 h of testing Ba completely reacts with water in a short time frame and there is no (visual) evidence of remaining Ba metal after 24h. In a first instance it dissolves to Ba(OH)₂, resulting in an increase of pH, and then precipitates as BaCO₃. The difference in measured dissolved Ba concentrations between the pH 6 and pH 8 media is driven by the difference in buffer capacity and different potential for carbonate precipitation.

 

 

The OECD Series 29 requires a limit of 20 % and 10 % for the between-vessel and the within-vessel variation, respectively. The observed variations within and between test vessels for the barium concentrations with a loading of 100 mg test item/L at pH 6 and 8 are mostly in compliance with the test guideline after one day of testing, except between-vessel variation at pH 6 (43.2 %). A lower Ba concentration has been quantified in vessel 5 compared to other Ba treatments at pH 6 (Table1,Table8) resulting in this increased between-vessel variation. The lower Ba concentration in vessel 5 compared to the other Ba treatments at pH 6 corresponds with a higher pH in this vessel after 24h (pH 8.9) compared to the other vessels with the same treatment (pH 8.1).

 

Table 1 compiles the results for the mean barium concentrations. For more details (e.g. Ba conc. each sample per vessel) see Table8(100 mg/L loading, pH 8 and 6) and Table9 (Ba concentrations in method blanks at pH 6 and 8).

 

Table1:       Mean measured barium concentrations and within- and between vessel variations for the loading of 100 mg/L (target pH 8: vessels 1, 2, 3; target pH 6: vessels 4, 5, 6)

vessel and day	target pH	mean Ba conc. per vessel [µg/L]	SD Ba conc. per vessel [µg/L]	within vessel variation [%]	mean Ba conc. Ba samples [µg/L]	SD Ba conc. Bal samples [µg/L]	between vessel variation [%]
1 d1	8	17887.5	9.9	0,1
2 d1	8	17713.3	50.6	0,3
3 d1	8	18731.2	82.1	0,4	18110.7	544.4	3.0
4 d1	6	85106.7	158.3	0,2
5 d1	6	34806.0	2.8	<0,1
6 d1	6	88082.0	685.3	0,8	69331.6	29937.0	43.2

Description of key information

Under the described conditions of this test with barium metal at a loading of 100 mg/L, dissolved barium concentrations were 18.11 ± 0.54 mg/L in media at pH8 and 69.33 ± 29.94 mg/L (1 d) in media at pH 6 after 24 h (1 d).

Additional information

Under the described conditions of this test with barium metal at a loading of 100 mg/L, dissolved barium concentrations were 18.11 ± 0.54 mg/L in media at pH8 and 69.33 ± 29.94 mg/L (1 d) in media at pH 6 after 24 h (1 d).