Zirconium praseodymium yellow zircon

Sediment toxicity

Administrative data

Endpoint:

sediment toxicity: long-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 9.5.1, Annex X, Commission Regulation (EU) 1907/2006 ” Long-term toxicity testing shall be proposed by the registrant if the results of the chemical safety assessment indicates the need to investigate further the effects of the substance and/or relevant degradation products on sediment organisms. The choice of the appropriate test(s) depends on the results of the chemical safety assessment.”

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.”

Zirconium praseodymium yellow zircon 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 (Grane, 2010) that indicate a very low release of pigment components. Transformation/dissolution of zirconium praseodymium yellow zircon (24-screening test according to OECD Series 29, loading of 100 mg/L) resulted in mean dissolved praseodymium concentrations of 3.05 µg/L Pr and 21.66 µg/L Pr, silicon concentrations of 0.13 µg/L Si and 0.02 µg/L Si at pH 6 and 8, respectively, whereas dissolved zirconium concentrations remained below the LOD (< 0.08 µg/L Zr). Since silicon does not have an ecotoxic potential, as confirmed by the absence of respective ecotoxicity reference values in the Metals classification tool (MeClas) database, and the dissolution of praseodymium is highest at pH 6, pH 6 is considered as pH that maximised metal release. Metal release at the 1 mg/L loading and pH 6 resulted in dissolved concentrations of 2.10 µg/L Pr and 0.17 µg/L Zr after 7 days and 0.79 µg/L Pr and < 0.08 µg/L Zr (< LOD) after 28 days whereas silicon concentrations remained below the LOD (< 0.07 µg/L Si) during the test. Thus, the rate and extent to which zirconium praseodymium yellow zircon produces soluble (bio)available ionic and other praseodymium-, silicon- or zirconium-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 zirconium praseodymium yellow zircon is expected to determine its behaviour and fate in the environment, and subsequently its potential for ecotoxicity.

Reliable proprietary studies are not available for zirconium praseodymium yellow zircon. The potential for acute aquatic toxicity of the poorly soluble substance zirconium praseodymium yellow zircon is evaluated by comparing the dissolved metal ion levels resulting from the transformation/dissolution test after 7 days at a loading rate of 1 mg/L with the lowest acute ecotoxicity reference values (ERVs) as determined for the (soluble) metal ions. The ERVs are based on the lowest EC50/LC50 values for algae, invertebrates and fish. Acute ERVs were obtained from the Metals classification tool (MeClas) database as follows: Hazard information for praseodymium is not included in the MeClas database. Nevertheless, soluble praseodymium salts (Praseodymium trichloride, EC 233-794-4, CAS 10361-79-2; Praseodymium trinitrate, EC 233-796-5, CAS 10361-80-5) are self-classified as Aquatic Acute 1 (M-factor 1) indicative of an L(E)C50 of > 0.1 ≤ 1 mg/L (https://echa.europa.eu/information-on-chemicals/cl-inventory-database, accessed on 12.03.2021), which is applied to evaluate the aquatic hazard potential of zirconium praseodymium yellow zircon. An acute ERV for silicon has not been derived since a concern for short-term (acute) toxicity of silicon ions was not identified (see also OECD, 2004). The acute ERV for zirconium in the MeClas database amounts to 74 mg Zr/L. According to ECHA’s Guidance on the Application of the CLP Criteria (Version 5.0, July 2017), “Where the acute ERV for the metal ions of concern is greater than 1 mg/L the metals need not be considered further in the classification scheme for acute hazard.” Metal release in the T/D test at the 1 mg/L loading and pH 6 resulted in dissolved concentrations of 2.10 µg/L Pr and 0.17 µg/L Zr after 7 days, whereas silicon concentrations remained below the LOD (< 0.07 µg/L Si). Due to the lack of an aquatic hazard potential for silicon and zirconium ions and the fact that dissolved praseodymium concentrations were well below the respective L(E)C50 estimate of > 0.1 ≤ 1 mg/L, it can be concluded that the substance zirconium praseodymium yellow zircon is not sufficiently soluble to cause short-term toxicity at the level of the acute ERVs (expressed as EC50/LC50).

Regarding the long-term toxicity, the poorly soluble substance zirconium praseodymium yellow zircon is evaluated by comparing the dissolved metal ion levels resulting from the transformation/dissolution test after 28 days at a loading rate of 1 mg/L with the lowest chronic ecotoxicity reference values (ERVs) as determined for the (soluble) metal ions. The ERVs are based on the lowest NOEC/EC10 values for algae, invertebrates and fish. Chronic ERVs were obtained from the Metals classification tool (MeClas) database as follows: Hazard information for praseodymium is not included in the MeClas database. Nevertheless, soluble praseodymium salts (Praseodymium trichloride, EC 233-794-4, CAS 10361-79-2; Praseodymium trinitrate, EC 233-796-5, CAS 10361-80-5) are self-classified as Aquatic Chronic 1 (M-factor 1) indicative of a NOEC/EC10 of > 0.01 ≤ 0.1 mg/L (https://echa.europa.eu/information-on-chemicals/cl-inventory-database, accessed on 12.03.2021), which is applied to evaluate the aquatic hazard potential of zirconium praseodymium yellow zircon. A chronic ERV for silicon has not been derived since a concern for long-term (chronic) toxicity of silicon ions was not identified (see also OECD, 2004). A chronic ERV has also not been derived for zirconium. Metal release in the T/D test at the 1 mg/L loading and pH 6 resulted in dissolved concentrations of 0.79 µg/L Pr and < 0.08 µg/L Zr (< LOD) after 28 days, whereas silicon concentrations remained also below the LOD (< 0.07 µg/L Si). Due to the lack of an aquatic hazard potential for silicon and zirconium ions and the fact that dissolved praseodymium concentrations were well below the respective NOEC/EC10 estimate of > 0.01 ≤ 0.1 mg/L, it can be concluded that the substance zirconium praseodymium yellow zircon 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” and 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 zirconium praseodymium yellow zircon is poorly soluble and does not meet classification criteria for acute (short-term) and chronic (long-term) aquatic hazard.

Zirconium praseodymium yellow zircon 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 not unclassified hazards to the sediment compartment because toxicity to aquatic organisms is used as an indicator of concern for sediment organisms and a screening risk characterisation (using the equilibration partitioning method to derive a PNEC for sediment) cannot be undertaken. Thus, zirconium praseodymium yellow zircon does not have a “non-classified hazard” potential.

Praseodymium forms several minerals and displays a very low mobility under naturally conditions (Reimann and de Caritat 1998).

Silicon is naturally abundant in sediments and a significant fraction of total silicon is associated with the solid phase (e.g., quartz). The major mineral phases of stream sediment are generally silicates or carbonates. Weathering of minerals is the primary source of Si in fresh water (Salminen et al. 2005).

Zirconium’s very low mobility under most environmental conditions limits concentrations in most natural waters and is mainly due to the stability of the principal host mineral zircon and the low solubility of the zircon hydroxide Zr(OH)4 (Salminen et al. 2005).

Monitoring data for praseodymium, silicon and zirconium background concentrations in stream water sediments are provided by the FOREGS Geochemical Baseline Mapping Programme, which offers high quality, multi-purpose homogeneous environmental geochemical baseline data for Europe.

A total of 741 (Pr), 743 (Si) or 744 (Zr) stream sediment samples were processed in the FOREGS-program for the EU-27, UK and Norway to determine representative concentrations. In stream sediments, praseodymium concentrations range from 0.3 to 125.0 mg/kg with 5th, 50th and 95th percentiles of 2.4, 7.4 and 24.3 mg/kg, respectively. Silicon concentrations range from 11,691.1 to 439,586.6 mg/kg with 5th, 50th and 95th percentiles of 161,384.4, 290,875.4 and 385,246.2 mg/kg, respectively. Zirconium concentrations range from 1.0 to 9,942.0 mg/kg with 5th, 50th and 95th percentiles of 118.5, 404.5 and 1,312.6 mg/kg, respectively.

Taking into account the high quality and representativeness of the FOREGS data set, the 95th percentiles of 24.3 mg Pr /kg, 385,246.2 mg Si /kg, and 1,312.6 mg Zr /kg sediment can be considered as representative background concentration of praseodymium, silicon and zirconium in European stream sediments.

Regarding essentiality, whereas praseodymium and zirconium are non-essential elements, having no known biological roles, silicon is considered necessary for various functions in some species, including diatom algae, gastropods and mammals. Silicon deficiency in animals may lead to delays in growth, bone deformations and abnormal skeletal development, and one of the symptoms of silicon deficiency is aberrant connective and bone tissue metabolism (Pérez-Granados and Vaquero, 2002).

Considering abundance and/or bioavailability, the potential of praseodymium, silicon and zirconium ions for toxicity to sediment organisms can be expected to be low.

Zirconium praseodymium yellow zircon is not classified as harmful, toxic or very toxic to aquatic life or may cause long lasting harmful effects to aquatic life. Zirconium praseodymium yellow zircon 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 and bioavailability of praseodymium, silicon and zirconium in sediment as well as essentiality and low bioaccumulation of praseodymium, silicon and zirconium, Zirconium praseodymium yellow zircon is also not considered an unclassified hazard to the sediment compartment. Results of the chemical safety assessment do not indicate the need to investigate further the effects of zirconium praseodymium yellow zircon on sediment organisms. Therefore, the study on the long-term toxicity to sediment organisms does not need to be conducted in accordance with Column 2 of Information Requirement 9.5.1., Annex X, Commission Regulation (EU) 1907/2006.

References

OECD (2004) SIDS Initial Assessment Profile Silicon dioxide, Silicic acid, aluminum sodium salt, Silicic acid, calcium salt. SIAM 19, 19-22 October 2004.

Pérez-Granados and Vaquero (2002) Silicon, aluminium, arsenic and lithium: Essentiality and human health implications. The Journal of Nutrition Health and Aging 6/2:154-62.

Reimann and de Caritat (1998) Chemical elements in the environment – Factsheets for geochemist and environmental scientist. Springer-Verlag, Berlin-Heidelberg, 398 pp.

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

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 silicon 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 silicon 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 silicon dioxide and 839 sediment samples of silicon dioxide were processed in the FOREGS-program, including 743 paired samples, i.e. samples with the same coordinates for the sampling location of stream water and sediment.
- The FOREGS dataset reports silicon/silicon dioxide 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 silicon dioxide concentrations were converted into silicon 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 silicon concentrations of 1,867 samples from the regularly ploughed layer (Ap-horizon) of agricultural land (arable land; 0 - 20 cm) and of 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. Silicon water levels range from 0.05 to 33.7 mg/L with 5^th, 50^th and 95^th percentiles of 0.8, 3.7 and 8.7 mg/L, respectively.

- In the sediment, silicon concentrations range from 11,691.1 to 439,586.6 mg/kg with 5^th, 50^th and 95^th percentiles of 161,384.4, 290,875.4 and 385,246.2 mg/kg, respectively (Table 1).

- Taking into account the high quality and representativeness of the data set, the 95^th percentile of 8.7 mg/L can be regarded as representative background concentration for dissolved silicon in European surface waters and the 95^th percentile of 385,246.2 mg/kg as representative background concentration of silicon in European stream sediments.

- Regarding the partitioning of silicon in the water column, stream water/sediment partition coefficients range from 7,056 to 5,290,000 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 4.87 is derived.

Table 1: Water parameters and silicon/silicon dioxide concentrations of stream sediment and stream water and respective partitioning.

	Parameter	#	Unit	Min.	Max.	5^thP	50^thP
water	pH ^1	735 ^2	-	9.80	4.50	8.50	7.70
water	Ca	743	mg/L	0.23	592.00	1.64	42.70
water	Cl	743	mg/L	0.14	4,560.00	0.49	9.32
water	HCO3	741 ^3	mg/L	0.69	1,804.42	5.36	131.67
water	K	743	mg/L	< 0.01	182.00	0.15	1.64
water	Mg	743	mg/L	0.05	230.00	0.46	6.22
water	Na	743	mg/L	0.23	4,030.00	1.00	6.76
water	NO3	743	mg/L	< 0.04	107.00	< 0.04	3.10
water	DOC	741 ^4	mg/L	< 0.50	57.94	0.60	4.79
water	SO4^2-	743	mg/L	< 0.30	2,420.00	1.18	17.10
water	SiO2	743	mg/L	0.10	72.00	1.66	8.00
water	Si ^5	743	mg/L	0.05	33.67	0.78	3.74
sediment	SiO2	743	%	2.50	94.00	34.51	62.20
sediment	Si ^5	743	mg/kg	11,691.13	439,586.58	161,384.39	290,875.37
Partitioning (Kp)	Si (sed/water)	743	L/kg	7,056	5,290,000	26,762	73,789
Log Kp	Si (sed/water)	743	-	3.85	6.72	4.43	4.87

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 SiO₂.

FOREGS DATABASE Background soil concentrations

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

- Baseline silicon levels in topsoil range from 6,874.4 to 452,306.5 mg/kg with 5^th, 50^th and 95^th percentiles of 159,055.5, 317,531.2 and 415,680.6 mg/kg, respectively (see Table 2)

- Taking into account the high quality and representativeness of the data set, the 95^th percentile of 415,680.6 mg/kg can be regarded as representative background concentration of silicon in topsoil of EU countries.

Table 2: Concentrations of silicon/silicon dioxide 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
SiO2	%	833	1.47	96.72	34.01	67.90	88.89
Si ^2	mg/kg	833	6,874.4	452,306.5	159,055.5	317,531.2	415,680.6

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

² Values converted from SiO₂.

GEMAS DATABASE AGRICULTURAL AND GRAZING LAND SOIL CONCENTRATIONS:

- Silicon levels of agricultural soil range from 11,499.0 to 448,274.0 mg/kg with 5^th, 50^th and 95^th percentiles of 156,447.5, 311,829.0 and 417,708.0 mg/kg, respectively (see Table 3). In grazing land, soil concentrations of silicon range from 7,058.0 to 450,293.0 mg/kg with 5^th, 50^th and 95^th percentiles of 133,489.0, 299,650.0 and 409,396.0 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
Silicon	mg/kg	XRF	1,867	11,499.00	448,274.00	156,447.50	311,829.00	417,708.00

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
Silicon	mg/kg	XRF	1,781	7,058.00	450,293.00	133,489.00	299,650.00	409,396.00

Conclusions:

Representative background or ambient concentrations of silicon/silicion dioxide in environmental compartments are tabulated below.

compartment, unit, concentration (50th P), concentration (95th P)
background stream water, mg/L SiO2, 8.0, 18.6
background stream water, mg/L Si, 3.7*, 8.7*
background stream water sediment, % SiO2, 62.2, 82.4
background stream water sediment, mg/kg Si, 290,875.4*, 385,246.2*
background topsoil, % SiO2, 67.9, 88.9
background topsoil, mg/kg Si, 317,531.2*, 415,680.6*
agricultural soil, mg/kg Si, 311,829.0, 417,708.0
grazing land soil, mg/kg Si, 299,650.0, 409,396.0
* based on measured SiO2.

Based on the FOREGS dataset, the 95th percentile of 8.7 mg/L can be regarded as representative background concentration of dissolved silicon in European surface waters and the 95th percentile of 385,246.2 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 4.87 is derived.

Based on the FOREGS dataset, the 95th percentile of 415,680.6 mg/kg can be regarded as representative background concentration of silicon in topsoil of EU countries. Representative silicon concentrations (95th percentile) of agricultural and grazing land soil (i.e. ambient levels) amount to 417,708.0 and 409,396.0 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 zirconium 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 zirconium 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 839 sediment samples were processed in the FOREGS-program, including 744 paired samples, i.e. samples with the same coordinates for the sampling location of stream water and sediment.
- The FOREGS dataset reports zirconium concentrations for 833 topsoil samples. 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 zirconium concentrations of 1,867 samples from the regularly ploughed layer (Ap-horizon) of agricultural land (arable land; 0-20 cm) and of 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. Zirconium water levels range from < 0.002 (< LOQ) to 2.4 µg/L with 5^th, 50^th and 95^th percentiles of 0.003, 0.05 and 0.5 µg/L, respectively.

- In the sediment, zirconium concentrations range from 1.0 to 9,942.0 mg/kg with 5^th, 50^th and 95^th percentiles of 118.5, 404.5 and 1,312.6 mg/kg, respectively (see Table 1).

- Taking into account the high quality and representativeness of the data set, the 95^th percentile of 0.5 µg/L can be regarded as representative background concentration for dissolved zirconium in European surface waters and the 95^th percentile of 1,312.6 mg/kg as representative background concentration of zirconium in European stream sediments.

- Regarding the partitioning of zirconium in the water column, stream water/sediment partition coefficients range from 125,000 to 1,060,000,000 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 6.94 is derived.

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

	Parameter	#	Unit	Min.	Max.	5^thP	50^thP	95^thP
water	pH ^1	736 ^2	-	9.80	4.50	8.50	7.70	6.10
water	Ca	744	mg/L	0.23	592.00	1.64	42.63	148.05
water	Cl	744	mg/L	0.14	4,560.00	0.49	9.36	71.43
water	HCO3	742 ^3	mg/L	0.69	1,804.42	5.37	129.69	373.80
water	K	744	mg/L	< 0.01	182.00	0.15	1.64	9.85
water	Mg	744	mg/L	0.05	230.00	0.46	6.23	38.67
water	Na	744	mg/L	0.23	4,030.00	1.00	6.76	48.35
water	NO3	744	mg/L	< 0.04	107.00	< 0.04	3.10	39.87
water	DOC	742 ^4	mg/L	< 0.50	57.94	0.60	4.80	23.05
water	SO4^2-	744	mg/L	< 0.30	2,420.00	1.18	17.03	166.99
water	Zr	744	µg/L	< 0.002	2.41	0.003	0.05	0.48
sediment	Zr	744	mg/kg	1.00	9,942.00	118.45	404.50	1,312.55
Partitioning (Kp)	Zr (sed/water)	744	L/kg	125,000	1,060,000,000	724,684	8,804,023	160,216,667
Log Kp	Zr (sed/water)	744	-	5.10	9.03	5.86	6.94	8.20

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 zirconium levels in topsoil range from 5.0 to 1,060.0 mg/kg with 5^th, 50^th and 95^th percentiles of 91.0, 231.0 and 466.6 mg/kg, respectively (see Table 2).

- Taking into account the high quality and representativeness of the data set, the 95^th percentile of 466.6 mg/kg can be regarded as representative background concentration of zirconium in topsoil of EU countries.

Table 2: Concentrations of zirconium 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
Zr	mg/kg	833	5.00	1,060.00	91.00	231.00	466.60

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

GEMAS DATABASE AGRICULTURAL AND GRAZING LAND SOIL CONCENTRATIONS:

- Zirconium levels of agricultural soil range from < 0.1 (< LOQ) to 165.2 mg/kg with 5^th, 50^th and 95^th percentiles of 0.2, 1.7 and 9.0 mg/kg, respectively (see Table 3). In grazing land, soil concentrations of zirconium range from < 0.1 (< LOQ) to 375.9 mg/kg with 5^th, 50^th and 95^th percentiles of 0.2, 1.5 and 9.1 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
Zirconium	mg/kg	AR	1,867	< 0.10	165.22	0.15	1.65	8.99
Zirconium	mg/kg	XRF	1,867	4.00	963.00	98.30	255.00	506.4
Zirconium	mg/kg	MMI	1,867	< 0.005	1.85	0.01	0.05	0.31

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
Zirconium	mg/kg	AR	1,781	< 0.10	375.89	0.16	1.54	9.12
Zirconium	mg/kg	XRF	1,781	4.00	871.00	90.00	241.00	477.00

Conclusions:

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

compartment, unit, concentration (50th P), concentration (95th P)
background stream water, µg/L Zr, 0.05, 0.5
background stream water sediment, mg/kg Zr, 404.5, 1,312.6
background topsoil, mg/kg Zr, 231.0, 466.6
agricultural soil, mg/kg Zr, 1.7, 9.0
grazing land soil, mg/kg Zr, 1.5, 9.1

Based on the FOREGS dataset, the 95th percentile of 0.5 µg/L can be regarded as representative background concentration of dissolved zirconium in European surface waters and the 95th percentile of 1,312.6 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 6.94 is derived.

Based on the FOREGS dataset, the 95th percentile of 466.6 mg/kg can be regarded as representative background concentration of zirconium in topsoil of EU countries. Representative zirconium concentrations (95th percentile) of agricultural and grazing land soil (i.e. ambient levels) amount to 9.0 and 9.1 mg/kg, respectively, according to the GEMAS dataset.

Cross-reference 3

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 praseodymium 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 praseodymium 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 835 sediment samples were processed in the FOREGS-program, including 741 paired samples, i.e. samples with the same coordinates for the sampling location of stream water and sediment.
- The FOREGS dataset reports praseodymium concentrations for 830 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 praseodymium 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. Praseodymium water levels range from < 0.002 µg/L (< LOQ) to 4.7 µg/L with 5^th, 50^th and 95^th percentiles of < 0.002 µg/L (< LOQ), 0.01 and 0.2 µg/L, respectively.

- In the sediment, praseodymium concentrations range from 0.3 to125.0 mg/kg with 5^th, 50^th and 95^th percentiles of 2.4, 7.4 and 24.3 mg/kg, respectively (Table 1).

- Taking into account the high quality and representativeness of the data set, the 95^th percentile of 0.2 µg/L can be regarded as representative background concentration for dissolved praseodymium in European surface waters and the 95^th percentile of 24.3 mg/kg as representative background concentration of praseodymium in European stream sediments.

- Regarding the partitioning of praseodymium in the water column, stream water/sediment partition coefficients range from 1,957 to 43,700,000 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 5.92 is derived.

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

	Parameter	#	Unit	Min.	Max.	5^thP	50^thP	95^thP
water	pH ^1	733 ^2	-	9.80	4.50	8.50	7.70	6.10
water	Ca	741	mg/L	0.23	592.00	1.63	42.70	147.20
water	Cl	741	mg/L	0.14	4,560.00	0.49	9.05	67.43
water	HCO3	739 ^3	mg/L	0.69	1,804.42	5.36	131.37	374.27
water	K	741	mg/L	< 0.01	182.00	0.15	1.64	9.80
water	Mg	741	mg/L	0.05	230.00	0.46	6.18	37.94
water	Na	741	mg/L	0.23	4,030.00	1.00	6.76	48.26
water	NO3	741	mg/L	< 0.04	107.00	< 0.04	3.10	39.90
water	DOC	739 ^4	mg/L	< 0.50	57.94	0.60	4.79	23.07
water	SO4^2-	737	mg/L	< 0.30	2,420.00	1.18	17.10	166.93
water	Pr	741	µg/L	< 0.002	4.70	< 0.002	0.01	0.20
sediment	Pr	741	mg/kg	0.30	125.00	2.40	7.40	24.30
Partitioning (Kp)	Pr (sed/water)	741	L/kg	1,957	43,700,000	34,884	833,333	6,100,000
Log Kp	Pr (sed/water)	741	-	3.29	7.64	4.54	5.92	6.79

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 praseodymium levels in topsoil range from 0.3 to 31.6 mg/kg with 5^th, 50^th and 95^th percentiles of 1.5, 5.6 and 11.7 mg/kg, respectively (see Table 2).

- Taking into account the high quality and representativeness of the data set, the 95^th percentile of 11.7 mg/kg can be regarded as representative background concentration of praseodymium in topsoil of EU countries.

Table 2: Concentrations of praseodymium in topsoil samples.

Parameter	Unit	#	Min.	Max.	5^thP	50^thP	95^thP
pH ^1	-	804	7.55	3.38	7.31	5.49	4.28
TOC	%	803	0.07	46.61	0.56	1.72	5.86
Pr	mg/kg	830	0.29	31.60	1.46	5.61	11.70

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

GEMAS DATABASE AGRICULTURAL AND GRAZING LAND SOIL CONCENTRATIONS:

- Praseodymium levels of agricultural soil (by MMI) range from < 0.001 (< LOQ) to 3.0 mg/kg with 5^th, 50^th and 95^th percentiles of < 0.001 (< LOQ), 0.02 and 0.2 mg/kg, respectively (see Table 3).

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
Praseodymium	mg/kg	MMI	1,867	< 0.001	2.98	< 0.001	0.02	0.19

Conclusions:

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

compartment, unit, concentration (50th P), concentration (95th P)
background stream water, µg/L Pr, 0.01, 0.2
background stream water sediment, mg/kg Pr, 7.4, 24.3
background topsoil, mg/kg Pr, 5.6, 11.7
agricultural soil (by MMI), mg/kg Pr, 0.02, 0.2

Based on the FOREGS dataset, the 95th percentile of 0.2 µg/L can be regarded as representative background concentration for dissolved praseodymium in European surface waters and the 95th percentile of 24.3 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 5.92 is derived

Based on the FOREGS dataset, the 95th percentile of 11.7 mg/kg can be regarded as representative background concentration of praseodymium in topsoil of EU countries. Representative praseodymium concentrations (95th percentile) of agricultural soil (i.e. ambient levels) amount to 0.2 mg/kg (for MMI extracts), according to the GEMAS dataset.