Zirconium iron pink zircon

Toxicity to soil microorganisms

Administrative data

Endpoint:

toxicity to soil microorganisms

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.”

Zirconium zircon with encapsulated hematite 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. Transformation/dissolution tests at a loading of 100 mg/L for 7 days resulted in dissolved iron and zirconium concentrations below the LOD of < 0.5 µg/L at pH 6 and 2.4 µg Fe/L and 2.17 µg Zr/L at pH 8. Thus, metal release is maximised at pH 8. Transformation/dissolution at a loading of 1 mg/L and pH 8 resulted in dissolved iron and zirconium concentrations below the LOD (< 0.5 µg/L) after 7 and 28 days. Silicon was not considered in the T/D assessment since it does not have an ecotoxic potential as confirmed by the absence of respective ecotoxicity reference values in the Metals classification tool (MeClas) database (see also OECD 2004). Thus, the rate and extent to which Zirconium zircon with encapsulated hematite produces soluble (bio)available ionic and other iron- and 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 zircon with encapsulated hematite is expected to determine its behaviour and fate in the environment, and subsequently its potential for ecotoxicity.

Proprietary studies are not available for Zirconium zircon with encapsulated hematite. The poorly soluble substance Zirconium zircon with encapsulated hematite 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 respective lowest acute and chronic ecotoxicity reference values (ERVs) as determined for the (soluble) metal ions. The acute and chronic ERVs are based on the lowest EC50/LC50 and NOEC/EC10 values for algae, invertebrates and fish, respectively, and were obtained from the Metals classification tool (MeClas) database as follows: 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 ERVs for iron (> 100 mg Fe/L) and zirconium (74 mg Zr/L) are above 1 mg/L and thus a concern for short-term (acute) toxicity was not identified (no classification). 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.” Due to the lack of an acute aquatic hazard potential for iron, silicon and zirconium ions and the fact that dissolved iron and zirconium concentrations remained below the LOD after 7 days at pH 8 and a loading of 1 mg/L in the T/D test, it can be concluded that the substance Zirconium zircon with encapsulated hematite 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, a chronic ERV for silicon has not been derived since a concern for long-term (chronic) toxicity of silicon ions was also not identified (see also OECD, 2004). A chronic ERV has also not been derived for zirconium. For iron ions, the chronic ERV is above 1 mg/L and a concern for long-term (chronic) toxicity was not identified (no classification). According to ECHA Guidance on the Application of the CLP Criteria (Version 5.0, July 2017), ”Where the chronic ERV for the metal ions of concern corrected for the molecular weight of the compound (further called as chronic ERV compound) is greater than 1 mg/L, the metal compounds need not to be considered further in the classification scheme for long-term hazard.” Due to the lack of a chronic aquatic hazard potential for iron, silicon and zirconium ions and the fact that dissolved iron and zirconium concentrations were below the LOD of 0.5 µg/L after 28 days at pH 8 in the T/D test, it can be concluded that the substance Zirconium zircon with encapsulated hematite 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 zircon with encapsulated hematite is poorly soluble and does not meet classification criteria for acute (short-term) and chronic (long-term) aquatic hazard.

Zirconium zircon with encapsulated hematite 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 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, Zirconium zircon with encapsulated hematite does not have a “non-classified hazard” potential.

Iron is the fourth most abundant element and the second most abundant metal in the Earth’s crust (after aluminium). It is present mostly as ferrous iron (Fe2+) in ferro-magnesian silicates, such as olivine, pyroxene, amphibole and biotite, and as ferric iron (Fe3+) in iron oxides and hydroxides, as the result of weathering (Salminen et al. 2005). Ferrous iron is more soluble and bioavailable to plants than ferric iron. Iron is an abundant element in rocks and soils, but it is also one of the most commonly deficient micronutrients due to the extremely insoluble nature of certain compounds of ferric iron (US EPA, 2003).

Silicon, at about 28%, is the second most abundant element in the Earth’s crust after oxygen, and is mainly found in silica or silicate forms. It is a major constituent of nearly all rocks. Quartz, SiO2, is the most resistant mineral in soil. Quartz, because of its very low aqueous solubility, may be considered unreactive, and it is one of the residual minerals remaining in soil after other minerals have altered or dissolved (Salminen et al. 2005 and references therein).

Zirconium with an average crustal abundance of 162 mg/kg is a lithophile metallic element, forms several minerals, including zircon ZrSiO4, and also displays very low mobility under most environmental conditions, mainly due to the stability of the principal host mineral zircon and the low solubility of the hydroxide Zr(OH)4 (Salminen et al. 2005 and references therein).

Monitoring data for elemental iron, silicon and zirconium 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). The FOREGS dataset for EU-27 countries plus UK and Norway reports iron, silicon and zirconium concentrations for 825 (Fe) and 833 (Si and Zr) topsoil samples.

Baseline iron levels in topsoil range from 0.7 to 152.4 g Fe/kg with 5th, 50th and 95th percentiles of 3.5, 19.6 and 44.3 g Fe/kg, respectively. Baseline silicon levels (derived from silicon dioxide data) in topsoil range from 6,874 to 452,307 mg Si/kg with 5th, 50th and 95th percentiles of 159,056, 317,531 and 415,681 mg Si/kg, respectively. Baseline zirconium levels in topsoil range from 5.0 to 1,060.0 mg Zr/kg with 5th, 50th and 95th percentiles of 91.0, 231.0 and 466.6 mg Zr/kg, respectively.

Taking into account the high quality and representativeness of the data set, the 95th percentiles of 44.3 g Fe/kg, 415,681 mg Si/kg and 466.6 mg Zr/kg can be regarded as representative background concentrations of iron, silicon and zirconium in topsoil of EU countries.

Additionally, iron, silicon and zirconium concentrations in 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, 1867 and 1781 samples of agricultural and grazing land soil were analysed.

Based on the GEMAS dataset, iron levels of agricultural soil range from 404.5 to 133,926.1 mg Fe/kg with 5th, 50th and 95th percentiles of 3,223.4, 17,165.1 and 36,998.8 mg Fe/kg, respectively. In grazing land, soil concentrations of iron range from 510.3 to 94,759.1 mg Fe/kg with 5th, 50th and 95th percentiles of 3,448.0, 16,949.0 and 38,345.0 mg Fe/kg, respectively.

Silicon levels of agricultural soil range from 11,499 to 448,274 mg Si/kg with 5th, 50th and 95th percentiles of 156,448, 311,829 and 417,708 mg Si/kg, respectively. In grazing land, soil concentrations of silicon range from 7,058 to 450,293 mg Si/kg with 5th, 50th and 95th percentiles of 133,489, 299,650 and 409,396 mg Si/kg, respectively.

Zirconium levels of agricultural soil range from < 0.1 (< LOQ) to 165.22 mg Zr/kg with 5th, 50th and 95th percentiles of 0.15, 1.65 and 8.99 mg Zr/kg, respectively. In grazing land, soil concentrations of zirconium range from < 0.1 (< LOQ) to 375.89 mg Zr/kg with 5th, 50th and 95th percentiles of 0.16, 1.54 and 9.12 mg Zr/kg, respectively.

According to the GEMAS dataset, representative iron, silicon and zirconium concentrations (95th percentile) of agricultural and grazing land soil (i.e. ambient levels) amount to 36,998.8 and 38,345.0 mg Fe/kg, 417,708 and 409,396 mg Si/kg, 8.99 and 9.12 mg Zr/kg, respectively.

Regarding essentiality, iron is an essential trace element for living organisms including animals, plants and microorganisms. It serves as a cofactor in a variety of enzymes involved in the electron transport processes of various metabolic pathways, i.e., photosynthesis, respiration, and nitrogen fixation. It is a structural component of the metalloenzyme nitrogenase, which is the key enzyme in the nitrogen fixation process performed by different microorganisms. Due to its involvement in the synthesis and maintenance of chlorophyll, iron is a vital factor for the photosynthetic performance of plants. As an essential component of the haemoglobin of red blood cells, iron functions as a carrier of oxygen in the blood and muscles of animals (e.g. US EPA, 2003; Colombo et al. 2014). 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). Zirconium is a non-essential element without a known biological role.

Considering abundance and/or bioavailability of iron, silicon and zirconium in soil and the low release of these ions under environmental conditions from Zirconium zircon with encapsulated hematite, the potential for toxicity to terrestrial organisms can be expected to be low.

Zirconium zircon with encapsulated hematite is not classified as harmful, toxic or very toxic to aquatic life or may cause long lasting harmful effects to aquatic life. Zirconium zircon with encapsulated hematite 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/or bioavailability of iron, silicon and zirconium in soil, Zirconium zircon with encapsulated hematite 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 Zirconium zircon with encapsulated hematite on soil organisms. Therefore, the study on effects on soil microorganisms does not need to be conducted in accordance with Column 2 of Information Requirement 9.4.2., Annex IX, Commission Regulation (EU) 1907/2006.

References:

Colombo et al. (2014) Review on iron availability in soil: interaction of Fe minerals, plants, and microbes. Journal of Soils and Sediments 14: 538–548.

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 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.

US EPA (2003) Ecological Soil Screening Level for Iron, Interim Final, OSWER Directive 9285.7-69.

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 iron 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 iron 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 iron concentrations for 825 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 iron 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. Iron water levels range from < 1.0 (< LOQ) to 4,820.0 µg/L with 5^th, 50^th and 95^th percentiles of 4.1, 65.4 and 1,120.0 µg/L, respectively.

- In the sediment, iron concentrations range from 0.6 to192.4 g/kg with 5^th, 50^th and 95^th percentiles of 5.8, 20.1 and 45.3 g/kg, respectively (Table 1).

- Taking into account the high quality and representativeness of the data set, the 95^th percentile of 1,120.0 µg/L can be regarded as representative background concentration for dissolved iron in European surface waters and the 95^th percentile of 45.3 g/kg as representative background concentration of iron in European stream sediments.

- Regarding the partitioning of iron in the water column, stream water/sediment partition coefficients range from 1,413 to 294,000,000 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 5.48 is derived.

Table 1: Water parameters and iron 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	Fe	737	µg/L	< 1.00	4,820.00	4.10	65.40	1,120.00
sediment	Fe	737	g/kg	0.60	192.40	5.78	20.10	45.28
Partitioning (Kp)	Fe (sed/water)	737	L/kg	1,413	294,000,000	14,317	303,282	6,805,391
Log Kp	Fe (sed/water)	737	-	3.15	8.47	4.16	5.48	6.83

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 iron levels in topsoil range from 0.7 to 152.4 g/kg with5^th, 50^th and 95^th percentiles of 3.5, 19.6 and 44.3 g/kg, respectively (see Table 2).

- Taking into account the high quality and representativeness of the data set,the 95^th percentile of 44.3 g/kg can be regarded as representative background concentration of iron in topsoil of EU countries.

Table 2: Concentrations of iron 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
Fe	g/kg	825	0.70	152.40	3.52	19.60	44.30

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

GEMAS DATABASE AGRICULTURAL AND GRAZING LAND SOIL CONCENTRATIONS:

- Iron levels of agricultural soil range from 404.5 to 133,926.1 mg/kg with 5^th, 50^th and 95^th percentiles of 3,223.4, 17,165.1 and 36,998.8 mg/kg, respectively (see Table 3). In grazing land, soil concentrations of iron range from 510.3 to 94,759.1 mg/kg with 5^th, 50^th and 95^th percentiles of 3,448.0, 16,949.0 and 38,345.0 mg/kg, respectively (see Table 4).

Table 3: Agricultural soil concentrations.

Parameter	Unit	Method	#	Min.	Max.	5^thP	50^thP	95^thP
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
Iron	mg/kg	AR	1,867	404.50	133,926.10	3,223.35	17,165.05	36,998.83
Iron	mg/kg	XRF	1,867	909.00	154,715.00	5,595.00	24,620.00	48,499.00
Iron	mg/kg	MMI	1,867	0.50	2,200.00	7.00	35.00	249.00

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
Iron	mg/kg	AR	1,781	510.31	94,759.13	3,447.99	16,948.95	38,344.67
Iron	mg/kg	XRF	1,781	979.00	114,422.00	5,665.00	24,129.00	49,727.00

Conclusions:

Representative background or ambient concentrations of iron in environmental compartments are tabulated below:

compartment, unit, concentration (50th P), concentration (95th P)
background stream water, µg/L Fe, 65.4, 1,120.0
background stream water sediment, g/kg Fe, 20.1, 45.3
background topsoil, g/kg Fe, 19.6, 44.3
agricultural soil, mg/kg Fe, 17,165.1, 36,998.8
grazing land soil, mg/kg Fe, 16,949.0, 38,344.7

Based on the FOREGS dataset, the 95th percentile of 1,120.0 µg/L can be regarded as representative background concentration for dissolved iron in European surface waters and the 95th percentile of 45.3 g/kg as representative background concentration of European stream sediments. Regarding the respective partitioning between sediment and water, a European median log Kp value of 5.48 is derived.

Based on the FOREGS dataset, the 95th percentile of 44.3 g/kg can be regarded as representative background concentration of iron in topsoil of EU countries. Representative iron concentrations (95th percentile) of agricultural and grazing land soil (i.e. ambient levels) amount to 36,998.8 and 38,344.7 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 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.