Cobalt aluminate blue spinel

Toxicity to terrestrial plants

Administrative data

Endpoint:

toxicity to terrestrial plants: short-term

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
According to Column 2 of Information Requirement 9.4., Annex IX, Commission Regulation (EU) 1907/2006, ”These studies do not need to be conducted if direct and indirect exposure of the soil compartment is unlikely. In the absence of toxicity data for soil organisms, the equilibrium partitioning method may be applied to assess the hazard to soil organisms. Where the equilibrium partitioning method is applied to nanoforms, this shall be scientifically justified. The choice of the appropriate tests depends on the outcome of the chemical safety assessment. In particular for substances that have a high potential to adsorb to soil or that are very persistent, the registrant shall consider long-term toxicity testing instead of short-term.”

According to Section 8.4.2 of ECHA Guidance on IR & CSA, Part B: Hazard assessment (Version 2.1; ECHA, 2011), “For substances which are classified as harmful, toxic or very toxic to aquatic life (i.e. H412, H411, H410 and H400), an aquatic PNEC can be derived. In these circumstances there are unclassified hazards to the sediment and soil compartments because toxicity to aquatic organisms is used as an indicator of concern for sediment and soil organisms, and a screening risk characterisation is undertaken using the equilibration partitioning method (EPM) to derive PNECs for sediment and soil. Hence quantitative exposure assessment, i.e. derivation of PECs, is mandatory for the water, sediment and soil environmental compartments.

Substances with the only environmental classification as ‘May cause long lasting harmful effects to aquatic life’ (i.e. H413) have been established as persistent in the aquatic environment and potentially bioaccumulative on the basis of test or other data. There are also potential hazards for these substances for the sediment and soil compartments, because these substances are potentially bioaccumulative in all organisms and are also potentially persistent in sediment and soil. Hence exposure assessment is mandatory for the water, sediment and soil environmental compartments, which may be quantitative or qualitative as appropriate. PBT and vPvB substances have been established as persistent and bioaccumulative (and the former also as toxic) in the environment as a whole. Hence qualitative exposure assessment is mandatory for the water, sediment and soil environmental compartments.

If there are ecotoxicity data showing effects in aquatic organisms, but the substance is not classified as dangerous for the aquatic environment, an aquatic PNEC can nevertheless be derived thus indicating a hazard to the aquatic environment. In these circumstances there are also unclassified hazards to the sediment and soil compartments because toxicity to aquatic organisms is used as an indicator of concern for sediment and soil organisms and a screening risk characterisation is undertaken using the equilibration partitioning method (EPM) to derive PNECs for sediment and soil. Hence quantitative exposure assessment, i.e. derivation of PECs, is mandatory for the water, sediment and soil environmental compartments.”

Cobalt aluminate blue spinel can be considered environmentally and biologically inert due to the characteristics of the synthetic process (calcination at a high temperature of approximately 1000°C), rendering the substance to be of a unique, stable crystalline structure in which all atoms are tightly bound and not prone to dissolution in environmental and physiological media. This assumption is supported by available transformation/dissolution data (Pardo Martinez, 2013) that indicate a very low release of pigment components at pH 8, the pH that maximises dissolution. Transformation/dissolution tests at a loading of 1 mg/L and pH 8 resulted in dissolved cobalt concentrations that remained below the LOD (i.e. < 0.5 µg Co/L) during the 28-d test. Dissolved aluminium concentrations after 7 and 28 days amount to 1.9 and 2 µg Al/L, respectively. Thus, the rate and extent to which Cobalt aluminate blue spinel produces soluble (bio)available ionic and other aluminium-and cobalt-bearing species in environmental media is limited. Hence, the pigment can be considered as environmentally and biologically inert during short- and long-term exposure. The poor solubility of Cobalt aluminate blue spinel is expected to determine its behaviour and fate in the environment, and subsequently its potential for ecotoxicity.

Proprietary studies are not available for Cobalt aluminate blue spinel. The poorly soluble substance Cobalt aluminate blue spinel is evaluated by comparing the dissolved metal ion levels resulting from the transformation/dissolution test after 7 and 28 days at a loading rate of 1 mg/L with the lowest acute and chronic ecotoxicity reference values (ERVs) as determined for the (soluble) metal ions. The ERVs are based on the lowest EC50/LC50 or NOEC/EC10 values for algae, invertebrates and fish.

Since cobalt ion concentrations remained below the LOD during the T/D test and are well below respective ecotoxicity ERVs, only aluminium concentrations are taken into account. The dissolved aluminium concentration of 1.9 microg/L in the T/D test after 7 days at pH 8 (i.e. the pH that maximizes the dissolution) is significantly lower than the lowest short-term ERVs (EC50s of 1,040 µg/L and 3,390 µg/L for algae at pH 6 and 8, respectively). Hence, the substance Cobalt aluminate blue spinel is not sufficiently soluble to cause short-term toxicity at the level of the acute ERVs (expressed as EC50/LC50). There is not a concern for long-term (chronic) toxicity of aluminium ions according to the Classification and Labelling Committee in 1999 (see report 013-003-00-7 submitted to the C&L Committee, 1999), and a chronic ERV has not been derived for dissolved aluminium ions. Hence, the substance Cobalt aluminate blue spinel is not sufficiently soluble to cause long-term toxicity at the level of the chronic ERVs (expressed as NOEC/EC10).

In accordance with Figure IV.4 “Classification strategy for determining acute aquatic hazard for metal compounds”, Figure IV.5 „Classification strategy for determining long-term aquatic hazard for metal compounds “of ECHA Guidance on the Application of the CLP Criteria (Version 5.0, July 2017) and section 4.1.2.10.2. of Regulation (EC) No 1272/2008, the substance Cobalt aluminate blue spinel is poorly soluble and does not meet classification criteria for acute (short-term) and chronic (long-term) aquatic hazard.

Cobalt aluminate blue spinel is not classified as dangerous for the aquatic environment, an aquatic PNEC cannot be derived, thus not indicating a hazard to the aquatic environment. In these circumstances there are also no unclassified hazards to the soil compartment because toxicity to aquatic organisms is used as an indicator of concern for soil organisms and a screening risk characterisation (using the equilibration partitioning method to derive a PNEC for soil) cannot be undertaken. Thus, Cobalt aluminate blue spinel does not have a “non-classified hazard” potential.

With an average crustal abundance of about 8.3%, aluminium is the most abundant metal in the lithosphere and ubiquitous in the environment. As ubiquitous element, it is a major constituent of many rock-forming minerals, and the weathered products of aluminium minerals include secondary clay minerals, and aluminium-hydroxides, which may control the equilibrium concentration of aluminium in soil solution, groundwater and stream water. The speciation of aluminium in the environment is determined by pH, mineralogical composition, and the abundance of organic complexing agents. Under most environmental conditions, aluminium has a low mobility. However, decreasing pH (below pH 5.5) increases the mobility of aluminium ions (Salminen et al. 2005 and references therein).

Cobalt is ubiquitous with an average abundance of 17 mg Co/kg in the upper continental crust and found in several rock-forming minerals. Cobalt ions are most mobile in the surface environment under acidic and reducing conditions (Salminen et al. 2005 and references therein).

Monitoring data for elemental aluminium and cobalt background concentrations in soil are provided by the FOREGS Geochemical Baseline Mapping Programme, that offers high quality, multi-purpose homogeneous environmental geochemical baseline data for Europe (Salminen et al. 2005 and references therein).

The FOREGS dataset for EU-27 countries plus UK and Norway reports aluminium oxide and cobalt concentrations for 833 (Al2O3) and 825 (Co) topsoil samples. Baseline aluminium levels in topsoil range from 1,958.2 to 141,151.2 mg Al/kg with 5th, 50th and 95th percentiles of 16,322.1, 58,376.4 and 92,121.4 mg Al/kg, respectively. Baseline cobalt levels in topsoil range from < 1.0 (< LOQ) to 255.0 mg Co/kg with 5th, 50th and 95th percentiles of < 1.0 (< LOQ), 7.0 and 21.0 mg Co/kg, respectively.

Additionally, aluminium and cobalt concentrations of agricultural soils were determined in the GEMAS project (Geochemical Mapping of Agricultural and Grazing land Soil), that offers high quality harmonized, freely and interoperable geochemical data for the top layer of agricultural and grazing land soil (Reimann et al. 2014). For the EU-27, UK and Norway, 1,867 and 1,781 samples of agricultural and grazing land soil were analysed for aluminium and cobalt.

Aluminium levels of agricultural soil range from 351.6 to 64,527.0 mg Al/kg with 5th, 50th and 95th percentiles of 2,508.0, 10,769.4 and 23,999.1 mg Al/kg, respectively. In grazing land, soil concentrations of aluminium range from 627.3 to 62,541.8 mg Al/kg with 5th, 50th and 95th percentiles of 2,335.6, 10,506.8 and 25,326.4 mg Al/kg, respectively.

Cobalt levels of agricultural soil range from < 0.1 (< LOQ) to 126.1 mg Co/kg with 5th, 50th and 95th percentiles of 1.0, 7.2 and 21.6 mg Co/kg, respectively. In grazing land, soil concentrations of cobalt range from 0.1 to 114.3 mg Co/kg with 5th, 50th and 95th percentiles of 1.0, 7.1 and 20.9 mg Co/kg, respectively.

Based on the FOREGS dataset, the 95th percentile of 92,121.4 mg Al/kg can be regarded as representative background concentration of aluminium in topsoil of EU countries. Representative aluminium concentrations (95th percentile) of agricultural and grazing land soil (i.e. ambient levels) amount to 23,999.1 and 25,326.4 mg Al/kg, respectively, according to the GEMAS dataset.

Based on the FOREGS dataset, the 95th percentile of 21.0 mg Co/kg can be regarded as representative background concentration of cobalt in topsoil of EU countries. Representative cobalt concentrations (95th percentile) of agricultural and grazing land soil (i.e. ambient levels) amount to 21.6 and 20.9 mg Co/kg, respectively, according to the GEMAS dataset.

Cobalt is an essential trace elements, acts as catalytic or structural components of larger molecules and occupy key roles in essential metabolic pathways of microorganisms, plants, and animals.

Cobalt is e.g. required in the nitrogen fixation processes of bacteria, algae and plants. In animals cobalt is the key element of Vitamin B12, which is required i.e., as co-factor for methionine synthase, in the synthesis of the citric acid cycle intermediate, succinyl-CoA and for a proper function of neurons. It can be assumed that the cellular uptake of cobalt is actively regulated by a strict control system as already known for other trace elements, which suggest a low potential for cobalt bioaccumulation (WHO, 2006 and references therein).

Aluminium and cobalt are abundant in soil environments and soil organisms are well adapted to the presence. The addition of anthropogenic aluminium and cobalt in a poorly soluble form to soil is not expected to be relevant for respective total and bioavailable soil concentrations and toxicity. Thus, additional soil testing is not expected to provide any further insight.

Cobalt aluminate blue spinel is not classified as harmful, toxic or very toxic to aquatic life or may cause long lasting harmful effects to aquatic life. Cobalt aluminate blue spinel is also not an unclassified hazard to the aquatic environment. Based on the poor solubility, bioavailability, lack of a potential for bioaccumulation and toxicity to aquatic organisms and considering ubiquitousness of aluminium and cobalt and the respective essentiality in soil, Cobalt aluminate blue spinel is also not considered an unclassified hazard to the soil compartment. Results of the chemical safety assessment do not indicate the need to investigate further the effects of Cobalt aluminate blue spinel on soil organisms. Therefore, the study on short-term toxicity to terrestrial plants does not need to be conducted in accordance with Column 2 of Information Requirement 9.4.3., Annex IX, Commission Regulation (EU) 1907/2006.

References:

Reimann et al. (2014) Chemistry of Europe’s agricultural soils - Part A: Methodology and interpretation of the GEMAS data set.

Salminen et al. (2005) Geochemical Atlas of Europe - Part 1: Background information, Methodology and Maps. EuroGeoSurveys.

WHO (2006) Concise International Chemical Assessment Document 69 - Cobalt and inorganic cobalt compounds

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

monitoring data

Type of information:

other: report

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

no guideline required

Principles of method if other than guideline:

Evaluation and summary of high quality environmental geochemical data for Europe, which is provided by the Forum of European Geological Surveys (FOREGS) and the European Geochemical Mapping of Agricultural and Grazing Land Soil (GEMAS), with respect to aluminium concentrations in stream water, stream sediment and topsoil, as well as in agricultural soil and grazing land.

GLP compliance:

no

Type of measurement:

other: Geochemical background and ambient aluminium concentrations in different environmental compartments across Europe

Media:

other: Natural stream water, stream sediment and topsoil, as well as agricultural and grazing land soils

Details on sampling:

FOREGS and GEMAS data for EU-27 countries plus UK and Norway were considered, i.e. data from non-EEA countries such as Albania, Bosnia and Switzerland were excluded from further analysis.

FOREGS:
- The FOREGS sampling grid was based on GTN grid cells developed for Global Geochemical Baseline mapping. This grid divides the entire land surface into 160 km x 160 km cells covering an area of 4,500,000 km2.
- Sampling methodology, preparation and analysis are described by Salminen et al. (2005).
- FOREGS data for EU-27 countries plus UK and Norway were considered, i.e. data from non-EEA countries such as Albania and Switzerland were excluded from further analysis.
- A total of 795 stream water samples of aluminium and 839 sediment samples of aluminium oxide were processed in the FOREGS-program, including 742 paired samples, i.e. samples with the same coordinates for the sampling location of stream water and sediment.
- The FOREGS dataset reports aluminium/aluminium oxide concentrations for 833 topsoil samples sampled on a grid across Europe. A topsoil sample was taken at each site from 0-25 cm (excluding material from the organic layer where present).
- Reported aluminium oxide concentrations were converted into aluminium concentrations.
- High quality and consistency of the obtained data were ensured by using standardised sampling methods and by treating and analysing all samples in the same laboratory of each country.

GEMAS:
- Samples from 33 out of 38 European countries were analysed to develop a suitable harmonised geochemical data base for soils. The sampling started in the spring 2008 and the first four months of 2009.
- The whole GEMAS project area of 5,600,000 km2 was divided into a grid with 50 km x 50 km cells.
- To generate harmonised data sets, all project samples were processed by a central sample preparation facility in Slovakia.
- GEMAS data for EU-27 countries plus UK and Norway were considered, i.e. data from non-EEA countries such as Bosnia and Switzerland were excluded from further analysis.
- The GEMAS dataset reports aluminium concentrations for 1,867 samples from the regularly ploughed layer (Ap-horizon) of agricultural land (arable land; 0 - 20 cm) and for 1,781 samples from the top layer of grazing land (soil under permanent grass cover; 0 – 10 cm) sampled on a grid across Europe.

FOREGS DATABASE STREAM WATER/SEDIMENT:

- Sampled stream water and sediments cover a wide range of environmental conditions. Water parameters such as pH, hardness and organic carbon concentrations extend over several magnitudes. Aluminium water levels range from 0.7 to 3,370.0 µg/L with 5^th, 50^th and 95^th percentiles of 2.0, 17.1 and 313.9 µg/L, respectively.

- In the sediment, aluminium concentrations range from 1,058.5 to 137,075.9 mg/kg with 5^th, 50^th and 95^th percentiles of 12,225.7, 55,042.1 and 94,735.9 mg/kg, respectively (Table 1).

- Taking into account the high quality and representativeness of the data set, the 95^th percentile of 313.9 µg/L can be regarded as representative background concentration for dissolved aluminium in European surface waters and the 95^th percentile of 94,735.9 mg/kg as representative background concentration of aluminium in European stream sediments.

- Regarding the partitioning of aluminium in the water column, stream water/sediment partition coefficients range from 15,747 to 94,090,878 L/kg. Since FOREGS sampled on a grid aiming to equally represent geochemical baseline concentrations across Europe, a European median log K_p value of 6.39 is derived.

Table 1: Water parameters and aluminium/aluminium oxide concentrations of stream sediment and stream water and respective partitioning.

	Parameter	#	Unit	Min.	Max.	5^thP	50^thP	95^thP
water	pH ^1	734 ^2	-	9.80	4.50	8.50	7.70	6.10
water	Ca	742	mg/L	0.23	592.00	1.63	42.63	146.97
water	Cl	742	mg/L	0.14	4,560.00	0.49	9.19	67.33
water	HCO3	740 ^3	mg/L	0.69	1,804.42	5.36	131.52	374.14
water	K	742	mg/L	< 0.01	182.00	0.15	1.63	9.80
water	Mg	742	mg/L	0.05	230.00	0.46	6.20	37.85
water	Na	742	mg/L	0.23	4,030.00	1.00	6.73	48.26
water	NO3	742	mg/L	< 0.04	107.00	< 0.04	3.10	39.89
water	DOC	735 ^4	mg/L	< 0.50	57.94	0.60	4.79	23.07
water	SO4^2-	742	mg/L	< 0.30	2,420.00	1.18	17.03	166.75
water	Al	742	µg/L	0.70	3,370.00	2.00	17.10	313.90
sediment	Al2O3	742	%	0.20	25.90	2.31	10.40	17.90
sediment	Al ^5	742	mg/kg	1,058.50	137,075.93	12,225.69	55,042.07	94,735.87
Partitioning (Kp)	Al (sed/water)	742	L/kg	15,746	94,089,011	152,295	2,452,151	23,238,707
Log Kp	Al (sed/water)	742	-	4.20	7.97	5.18	6.39	7.37

¹ Statistics are based on H⁺ concentrations rather than pH.

² Removal of 2 outliers < pH 4.3 and 6 negative values.

³ Removal of 2 outliers < 0.01.

⁴ Removal of 1 outlier > 70 mg/L and 1 negative values.

⁵ Values converted from Al₂O₃.

FOREGS DATABASE Background soil concentrations

- Sampled soils cover a wide range of environmental conditions. Soil parameters, including pH and TOC, cover several magnitudes.

- Baseline aluminium levels in topsoil range from 1,958.2 to 141,151.2 mg/kg with 5^th, 50^th and 95^th percentiles of 16,322.1, 58,376.4 and 92,121.4 mg/kg, respectively (see Table 2).

- Taking into account the high quality and representativeness of the data set, the 95^th percentile of 92,121.4 mg/kg can be regarded as representative background concentration of aluminium in topsoil of EU countries.

Table 2: Concentrations of aluminium/aluminium oxide in topsoil samples.

Parameter	Unit	#	Min.	Max.	5^thP	50^thP	95^thP
pH ^1	-	802	7.55	3.38	7.31	5.49	4.28
TOC	%	799	0.07	46.61	0.56	1.72	5.86
Al2O3	%	833	0.37	26.67	3.08	11.03	17.41
Al ^2	mg/kg	833	1,958.2	141,151.2	16,322.1	58,376.4	92,121.4

¹ Statistics are based on H⁺ concentrations rather than pH.

² Values converted from Al₂O₃.

GEMAS DATABASE AGRICULTURAL AND GRAZING LAND SOIL CONCENTRATIONS:

- Aluminium levels of agricultural soil range from 351.6 to 64,527.0 mg/kg with 5^th, 50^th and 95^th percentiles of 2,508.0, 10,769.4 and 23,999.1 mg/kg, respectively (see Table 3). In grazing land, soil concentrations of aluminium range from 627.3 to 62,541.8 mg/kg with 5^th, 50^th and 95^th percentiles of 2,335.6, 10,506.8 and 25,326.4 mg/kg, respectively (see Table 4).

Table 3: Agricultural soil concentrations.

Parameter	Unit	Method	#	Min.	Max.	5^th P	50^th P	95^th P
CEC	meq/100g	AAS	1,867	1.80	48.30	6.10	15.80	33.30
pH (CaCl2)	pH	pH-meter	1,867	3.32	7.98	4.14	5.71	7.45
TOC	%	IR	1,854	0.40	46.00	0.70	1.70	5.67
Aluminium	mg/kg	AR	1,867	351.60	64,526.98	2,508.03	10,769.43	23,999.05
Aluminium	mg/kg	XRF	1,867	1,958.00	143,850.00	16,120.80	55,730.00	83,606.10
Aluminium	mg/kg	MMI	1,867	< 1.00	450.00	10.00	69.00	450.00

Table 4: Grazing land soil concentrations.

Parameter	Unit	Method	#	Min.	Max.	5^thP	50^thP	95^thP
CEC	meq/100g	AAS	1,781	2.54	49.88	8.27	17.96	37.74
pH (CaCl2)	pH	pH-meter	1,780	3.26	8.06	4.03	5.38	7.45
TOC	%	IR	1,780	0.41	49.00	0.94	2.80	11.05
Aluminium	mg/kg	AR	1,781	627.25	62,541.83	2,335.60	10,506.82	25,326.43
Aluminium	mg/kg	XRF	1,781	1,535.00	141,429.00	14,397.00	52,348.00	84,106.00

Conclusions:

Representative background or ambient concentrations of aluminium/aluminium oxide in environmental compartments are tabulated below.

compartment, unit, concentration (50th P), concentration (95th P)
background stream water, µg/L Al, 17.1, 313.9
background stream water sediment, % Al2O3, 10.4, 17.9
, mg/kg Al, 55,042.1*, 94,735.9*
background topsoil, % Al2O3, 11.0, 17.4
, mg/kg Al, 58,376.4*, 92,121.4*
agricultural soil, mg/kg Al, 10,769.4, 23,999.1
grazing land soil, mg/kg Al, 10,506.8, 25,326.4
* based on measured Al2O3.

Based on the FOREGS dataset, the 95th percentile of 313.9 µg/L can be regarded as representative background concentration for dissolved aluminium in European surface waters and the 95th percentile of 94,735.9 mg/kg as representative background concentration of European stream sediments. Regarding the respective partitioning between sediment and water, a European median log Kp value of 6.39 is derived.

Based on the FOREGS dataset, the 95th percentile of 92,121.4 mg/kg can be regarded as representative background concentration of aluminium in topsoil of EU countries. Representative aluminium concentrations (95th percentile) of agricultural and grazing land soil (i.e. ambient levels) amount to 23,999.1 and 25,326.4 mg/kg, respectively, according to the GEMAS dataset.

Cross-reference 2

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

monitoring data

Type of information:

other: report

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

no guideline required

Principles of method if other than guideline:

Evaluation and summary of high quality environmental geochemical data for Europe, which is provided by the Forum of European Geological Surveys (FOREGS) and the European Geochemical Mapping of Agricultural and Grazing Land Soil (GEMAS), with respect to cobalt concentrations in stream water, stream sediment and topsoil, as well as in agricultural soil and grazing land.

GLP compliance:

no

Type of measurement:

other: Geochemical background and ambient cobalt concentrations in different environmental compartments across Europe

Media:

other: Natural stream water, stream sediment and topsoil, as well as agricultural and grazing land soils

Details on sampling:

FOREGS and GEMAS data for EU-27 countries plus UK and Norway were considered, i.e. data from non-EEA countries such as Albania, Bosnia and Switzerland were excluded from further analysis.

FOREGS:
- The FOREGS sampling grid was based on GTN grid cells developed for Global Geochemical Baseline mapping. This grid divides the entire land surface into 160 km x 160 km cells covering an area of 4,500,000 km2.
- Sampling methodology, preparation and analysis are described by Salminen et al. (2005).
- FOREGS data for EU-27 countries plus UK and Norway were considered, i.e. data from non-EEA countries such as Albania and Switzerland were excluded from further analysis.
- A total of 795 stream water samples and 832 sediment samples were processed in the FOREGS-program, including 737 paired samples, i.e. samples with the same coordinates for the sampling location of stream water and sediment.
- The FOREGS dataset reports cobalt concentrations for 825 topsoil samples sampled on a grid across Europe. A topsoil sample was taken at each site from 0-25 cm (excluding material from the organic layer where present).
- High quality and consistency of the obtained data were ensured by using standardised sampling methods and by treating and analysing all samples in the same laboratory of each country.

GEMAS:
- Samples from 33 out of 38 European countries were analysed to develop a suitable harmonised geochemical data base for soils. The sampling started in the spring 2008 and the first four months of 2009.
- The whole GEMAS project area of 5,600,000 km2 was divided into a grid with 50 km x 50 km cells.
- To generate harmonised data sets, all project samples were processed by a central sample preparation facility in Slovakia.
- GEMAS data for EU-27 countries plus UK and Norway were considered, i.e. data from non-EEA countries such as Bosnia and Switzerland were excluded from further analysis.
- The GEMAS dataset reports cobalt concentrations for 1,867 samples from the regularly ploughed layer (Ap-horizon) of agricultural land (arable land; 0 - 20 cm) and for 1,781 samples from the top layer of grazing land (soil under permanent grass cover; 0 – 10 cm) sampled on a grid across Europe.

FOREGS DATABASE STREAM WATER/SEDIMENT:

- Sampled stream water and sediments cover a wide range of environmental conditions. Water parameters such as pH, hardness and organic carbon concentrations extend over several magnitudes. Cobalt water levels range from 0.01 to 15.7 µg/L with 5^th, 50^th and 95^th percentiles of 0.03, 0.2 and 0.9 µg/L, respectively.

- In the sediment, cobalt concentrations range from < 1.0 (< LOQ) to 245.0 mg/kg with 5^th, 50^th and 95^th percentiles of 1.0, 8.0 and 25.0 mg/kg, respectively (Table 1).

- Taking into account the high quality and representativeness of the data set, the 95^th percentile of 0.9 µg/L can be regarded as representative background concentration for dissolved cobalt in European surface waters and the 95^th percentile of 25.0 mg/kg as representative background concentration of cobalt in European stream sediments.

- Regarding the partitioning of cobalt in the water column, stream water/sediment partition coefficients range from 191 to 2,000000 L/kg. Since FOREGS sampled on a grid aiming to equally represent geochemical baseline concentrations across Europe, a European median log K_p value of 4.67 is derived.

Table 1: Water parameters and cobalt concentrations of stream sediment and stream water and respective partitioning.

	Parameter	#	Unit	Min.	Max.	5^thP	50^thP	95^thP
water	pH ^1	729 ^2	-	9.80	4.50	8.50	7.70	6.10
water	Ca	737	mg/L	0.23	592.00	1.61	42.44	143.52
water	Cl	737	mg/L	0.14	4,560.00	0.49	8.97	68.37
water	HCO3	735 ^3	mg/L	0.69	1,804.42	5.35	128.02	371.20
water	K	737	mg/L	< 0.01	182.00	0.14	1.62	9.81
water	Mg	737	mg/L	0.05	230.00	0.46	6.15	38.11
water	Na	737	mg/L	0.23	4,030.00	1.00	6.66	48.28
water	NO3	737	mg/L	< 0.04	107.00	< 0.04	3.09	39.91
water	DOC	735 ^4	mg/L	< 0.50	57.94	0.60	4.80	23.10
water	SO4^2-	737	mg/L	< 0.30	2,420.00	1.18	16.80	164.01
water	Co	737	µg/L	0.01	15.70	0.03	0.16	0.94
sediment	Co	737	mg/kg	< 1.00	245.00	1.00	8.00	25.00
Partitioning (Kp)	Co (sed/water)	737	L/kg	191	2,000,000	4,744	46,667	415,000
Log Kp	Co (sed/water)	737	-	2.28	6.30	3.68	4.67	5.62

¹ Statistics are based on H⁺ concentrations rather than pH.

² Removal of 2 outliers < pH 4.3 and 6 negative values.

³ Removal of 2 outliers < 0.01.

⁴ Removal of 1 outlier > 70 mg/L and 1 negative values.

FOREGS DATABASE Background soil concentrations

- Sampled soils cover a wide range of environmental conditions. Soil parameters, including pH and TOC, cover several magnitudes.

- Baseline cobalt levels in topsoil range from < 1.0 (< LOQ) to 255.0 mg/kg with 5^th, 50^th and 95^th percentiles of < 1.0 (< LOQ), 7.0 and 21.0 mg/kg, respectively (see Table 2).

- Taking into account the high quality and representativeness of the data set, the 95^th percentile of 21.0 mg/kg can be regarded as representative background concentration of cobalt in topsoil of EU countries.

Table 2: Concentrations of cobalt in topsoil samples.

Parameter	Unit	#	Min.	Max.	5^thP	50^thP	95^thP
pH ^1	-	798	7.55	3.38	7.31	5.49	4.29
TOC	%	805	0.07	46.61	0.55	1.72	5.87
Co	mg/kg	825	< 1.00	255.00	< 1.00	7.00	21.00

¹ Statistics are based on H⁺ concentrations rather than pH.

GEMAS DATABASE AGRICULTURAL AND GRAZING LAND SOIL CONCENTRATIONS:

- Cobalt levels of agricultural soil range from < 0.1 (< LOQ) to 126.1 mg/kg with 5^th, 50^th and 95^th percentiles of 1.0, 7.2 and 21.6 mg/kg, respectively (see Table 3). In grazing land, soil concentrations of cobalt range from 0.1 to 114.3 mg/kg with 5^th, 50^th and 95^th percentiles of 1.0, 7.1 and 20.9 mg/kg, respectively (see Table 4).

Table 3: Agricultural soil concentrations.

Parameter	Unit	Method	#	Min.	Max.	5^th P	50^th P	95^th P
CEC	meq/100g	AAS	1,867	1.80	48.30	6.10	15.80	33.30
pH (CaCl2)	pH	pH-meter	1,867	3.32	7.98	4.14	5.71	7.45
TOC	%	IR	1,854	0.40	46.00	0.70	1.70	5.67
Cobalt	mg/kg	AR	1,867	< 0.10	126.06	0.98	7.23	21.56
Cobalt	mg/kg	XRF	1,867	< 3.00	144.00	< 3.00	9.00	25.00
Cobalt	mg/kg	MMI	1,867	0.00	8.94	0.03	0.18	1.34

Table 4: Grazing land soil concentrations.

Parameter	Unit	Method	#	Min.	Max.	5^thP	50^thP	95^thP
CEC	meq/100g	AAS	1,781	2.54	49.88	8.27	17.96	37.74
pH (CaCl2)	pH	pH-meter	1,780	3.26	8.06	4.03	5.38	7.45
TOC	%	IR	1,780	0.41	49.00	0.94	2.80	11.05
Cobalt	mg/kg	AR	1,781	0.14	114.28	1.04	7.06	20.91
Cobalt	mg/kg	XRF	1,781	< 3.00	129.00	< 3.00	9.00	24.00

Conclusions:

Representative background or ambient concentrations of cobalt in environmental compartments are tabulated below.

compartment, unit, concentration (50th P), concentration (95th P)
background stream water, µg/L Co, 0.2, 0.9
background stream water sediment, mg/kg Co, 8.0, 25.0
background topsoil, mg/kg Co, 7.0, 21.0
agricultural soil, mg/kg Co, 7.2, 21.6
grazing land soil, mg/kg Co, 7.1, 20.9

Based on the FOREGS dataset, the 95th percentile of 0.9 µg/L can be regarded as representative background concentration for dissolved cobalt in European surface waters and the 95th percentile of 25.0 mg/kg as representative background concentration of European stream sediments. Regarding the respective partitioning between sediment and water, a European median log Kp value of 4.67 is derived.

Based on the FOREGS dataset, the 95th percentile of 21.0 mg/kg can be regarded as representative background concentration of cobalt in topsoil of EU countries. Representative cobalt concentrations (95th percentile) of agricultural and grazing land soil (i.e. ambient levels) amount to 21.6 and 20.9 mg/kg, respectively, according to the GEMAS dataset.