London Atlas: Materials and methods I: data acquisition

Ferreira, A, Johnson, C C, Appleton, J D, Flight, D M A, Lister, T R, Knights, K V, Ander, L, Scheib, C, Scheib, A, Cave, M, Wragg, J, Fordyce, F and Lawley, R. 2017. London Region Atlas of Topsoil Geochemistry. British Geological Survey.

The London Region Atlas of Topsoil Geochemistry (LRA) covers a rectangular area of 80 x 62 km (4960 km²), from British National Grid coordinates X, Y: 490000, 153000 to 570000, 215000. The LRA was produced using the London Region Topsoil Dataset (LRD, N=8400), which was created from two BGS geochemical surveys (LOND and SEEN) carried out under the Geochemical Baseline Survey of the Environment (G-BASE) project between 2005 and 2009. LOND is an urban soil survey based on 6801 sampling sites at a sampling density of 1 per 0.25 km²; 6494 (95.5%) of the LOND samples are part of the London Earth project as they are located within the GLA. SEEN is a south-east England rural soil survey carried out at a sampling density of 1 per 2 km²; 1599 (out of the 4089) SEEN sample sites are included in the LRA rectangle area; however, 95% are outwith the GLA limit as these are rural samples (Figure 2).

Field procedures and laboratory methods were undertaken in a standardised way to ensure consistency and enable quality assessment of the analytical results (Johnson et al., 2005). This allowed adequate levelling of geochemical datasets from contiguous areas, sampled and analysed at different times or under different projects. Methods are described in the following sections. Descriptions of the interpolation method (parent material mapping method, Appleton and Adlam, 2012) used to generate maps of the soil geochemical properties and of the exploratory data analysis techniques deployed are outlined in the last section.

Throughout this atlas the LRD dataset, and SEEN and LOND subsets are generally represented by the colours black/white, dark green and dark red respectively, while Quaternary, Palaeogene and Cretaceous geological time periods are represented by soft yellow, orange and lime green colours respectively.

Sampling

Sampling strategies for geochemical mapping using soil samples in rural (regional) and urban areas are described by Johnson et al. (2005) and Fordyce et al. (2005), respectively. The only major difference between the two is the sampling density. In rural areas soil samples are collected from alternate British National Grid (BNG) kilometre squares, corresponding to a sampling density of 1 sample/2 km² (or 0.5 samples/km²); sites are ideally located at least 100 m from roads, buildings, railways, electricity pylons etc., on open unforested, and undisturbed ground whenever possible; the site should be generally representative of the land use within the selected kilometre square. In urban areas, the sample density is 1 sample/0.25 km² (or 4 samples/km²); samples are collected from open ground (preferably gardens, parks, sports fields, road verges, allotments, open spaces, schoolyards, and waste ground) as close as possible to the centre of each 500 m cell (subdivisions of the BNG 1 km cell) (Figure 5). The greater density in urban areas allows the capture of more local-scale element concentration variability caused by human activity. The way of defining an urban area for sample collection purposes is described by Johnson and Ander (2008).

Soil sampling was carried out according to the procedures detailed in the G-BASE field procedures manual (Johnson, 2005). All soil samples were collected and transported in 5”x10” Kraft™ paper bags. Each sample consisted of approximately 250 g of unsieved material and was a composite of five subsamples from auger holes distributed within an area of approximately 20 x 20 m whenever possible. Auger holes were located at the corners and centre of a square (Figure 6). A 1 m stainless steel Dutch auger with a 15 cm auger flight was used to collect soil samples from a fixed depth.

Topsoil samples (sample type code ‘A’) were collected to a depth of 20 cm, after removal of surface vegetation, surface litter and root zone. The bottom depth of the sample was recorded on the field card and the depth of any rootlet zone and surface litter was also noted. The deep soil sample (sample type code ‘S’) was targeted to collect to a depth of 35-50 cm (in rural areas this had the objective of sampling below any ploughed horizon), the actual sampling depth was recorded on the field card. Over terrains where only thin soils were developed e.g. over chalk, then a topsoil sample was collected from the normal surface depth, i.e. 5 to 20 cm and the S sample from as deep as possible down to bedrock. In such instances there may be little difference in the sampling depths between the A and S samples.

An extra surface sample (0–2 cm) was collected in the London Earth GLA area, designated as sample type code ‘X’. The X samples often demanded material from additional auger holes within the 20 m square in order to reach the required sample weight of ca. 250 g. If a root layer was present this was collected as part of the surface sample (Knights and Scheib, 2010).

Field duplicate samples were collected at a rate of 1 duplicate per 100 sampling sites in rural surveys. This rate was doubled (2 per 100 sampling sites) in urban surveys following the higher sampling density implemented in these areas. For quality control purposes, the field duplicates were collected with exactly the same procedure as a regular sample, but in an adjacent auger square (Figure 6).

At each sampling site, information about date of sampling, local details (location, geology, visible contamination, land use, etc.) and observations of the sample, such as soil colour, depth, clast lithology and apparent abundance, and textural classification, were recorded on a field card.

The geochemical results for the topsoil samples type ‘A’ (5-20 cm depth) only are presented in this atlas.

Figure 5 The G-BASE strategy for urban (red X) and rural (green X) soil sampling sites. The grid represents 1 km squares and the urban region is shaded (adapted from Johnson, 2005). (P929861).

Figure 6 Plan of composite auger holes for collecting a soil sample (dashed square represents adjacent duplicate sample) (from Johnson, 2005). (P929862).

Sample preparation and analysis

Soil samples were prepared and analysed at the BGS laboratories in Keyworth. All samples were dried and sieved but only the topsoils were routinely analysed by XRFS. After air-drying at <35°C (to prevent volatilisation of Se and Hg), each sample was sieved through a nylon sieve to give the <2 mm fraction. The sample was then homogenised, coned and quartered before a 50 g subsample was pulverised in an agate planetary ball mill to create a homogeneous sample (95% under 53 mm), from which a portion (12 g) was taken to prepare a pressed powder pellet for XRFS analysis.

Samples were analysed for total element concentration by XRFS in the BGS laboratories in Keyworth. Analysis is accredited to ISO 17025 and to the Environment Agency's Monitoring Certification Scheme (MCERTS) standard for soils. Several different XRFS instruments were used, namely a PANalytical Axios advanced and a Philips MagiX PRO wavelength dispersive XRF spectrometer (WD-XRFS); and a PANalytical Epsilon-5 polarised energy dispersive XRF spectrometer (ED(P)XRFS), to determine 53 chemical elements. Forty-four of these elements are listed together with their lower limit of detection (LLD) and the number of samples below LLD in Table 3. The remaining nine elements (Table 4) were excluded as six of them (Cl, In, S, Te, Hg and Ta) showed more than 90% of the results below the LLD in at least one of the LRD subsets (SEEN, LOND) and five of them (Sm, Tl, Yb, Hg and Ta) showed a very small between-site variability (less than 35%), due to high within-sample and/or within-site variability mostly as a results of data close to the LLD (Table 5). Of the 44 elements shown in the London Region Atlas of Topsoil Geochemistry, the 10 most abundant elements (Al₂O₃, CaO, Fe₂O₃, K₂O, MgO, MnO, Na₂O, P₂O₅, SiO₂, TiO₂) are expressed in terms of weight percent oxide (wt%) as concentration units, while the remaining 34 (Ag, As, Ba, Bi, Br, Cd, Ce, Co, Cr, Cs, Cu, Ga, Ge, Hf, I, La, Mo, Nb, Nd, Ni, Pb, Rb, Sb, Sc, Se, Sn, Sr, Th, U, V, W, Y, Zn and Zr) are shown in mg/kg (equivalent to the non-SI old notation ppm - parts per million).

Two extra parameters, loss on ignition (LOI) and pH were also determined on the topsoil samples from the LOND subset (except one for LOI) and about two thirds (1128 out of 1599) of the SEEN subset, resulting in a total of 7928 (for LOI) and 7929 (for pH) measurements. The loss on ignition, a proxy for the soil’s organic matter content (but can be affected by the loss of structural water in clay soils (Rowell, 1994), was determined on 2 g of <2 mm size material by weighing the sample before and after heating in a furnace at 450°C for 24 hrs. The soil pH was determined with a pH electrode after mixing 10 g of <2 mm size material in 25 ml of 0.01 M CaCl₂.2H₂O and shaking until a slurry was formed.

Table 3 List of elements determined by XRFS reported in the London Region Atlas of Topsoil Geochemistry. The lower limit of detection (LLD), the number of samples below the LLD (n<LLD) and the n<LLD in percent (%<LLD) are shown for the London Region Dataset (LRD), and the two subsets (SEEN and LOND). Number of samples (N) is as follow: LRD = 8400, SEEN = 1599 and LOND = 6801.

Element Symbol Units	-Data-	-LLD-	-n<LLD-	-%<LLD-	.	Element Symbol Units	-Data-	-LLD-	-n<LLD-	-%<LLD-	.	Element Symbol Units	-Data-	-LLD-	-n<LLD-	-%<LLD-
Aluminium oxide Al2O3 %	LRD	0.2	0	0.0		Cadmium Cd mg/kg	LRD	0.5	2317	27.6		Lead Pb mg/kg	LRD	1.3	0	0.0
	SEEN	0.2	0	0.0			SEEN	0.5	787	49.2			SEEN	1.3	0	0.0
	LOND	0.2	0	0.0			LOND	0.5	1530	22.5			LOND	1.3	0	0.0
Calcium oxide CaO %	LRD	0.05	14	0.2		Cerium Ce mg/kg	LRD	1	0	0.0		Rubidium Rb mg/kg	LRD	1	0	0.0
	SEEN	0.05	14	0.9			SEEN	1	0	0.0			SEEN	1	0	0.0
	LOND	0.05	0	0.0			LOND	1	0	0.0			LOND	1	0	0.0
Iron (III) oxide Fe2O3 %	LRD	0.01	0	0.0		Cobalt Co mg/kg	LRD	1.5	27	0.3		Antimony Sb mg/kg	LRD	0.5	84	1.0
	SEEN	0.01	0	0.0			SEEN	1.5	19	1.2			SEEN	0.5	68	4.3
	LOND	0.01	0	0.0			LOND	1.5	8	0.1			LOND	0.5	16	0.2
Potassium oxide K2O %	LRD	0.01	0	0.0		Chromium Cr mg/kg	LRD	3	0	0.0		Scandium Sc mg/kg	LRD	3	374	4.5
	SEEN	0.01	0	0.0			SEEN	3	0	0.0			SEEN	3	198	12.4
	LOND	0.01	0	0.0			LOND	3	0	0.0			LOND	3	176	2.6
Magnesium oxide MgO %	LRD	0.3	376	4.5		Caesium Cs mg/kg	LRD	1	0	0.0		Selenium Se mg/kg	LRD	0.2	140	1.7
	SEEN	0.3	83	5.2			SEEN	1	0	0.0			SEEN	0.2	51	3.2
	LOND	0.3	293	4.3			LOND	1	0	0.0			LOND	0.2	89	1.3
Element Symbol Units	-Data-	-LLD-	-n<LLD-	-%<LLD-	.	Element Symbol Units	-Data-	-LLD-	-n<LLD-	-%<LLD-	.	Element Symbol Units	-Data-	-LLD-	-n<LLD-	-%<LLD-
Manganese oxide MnO %	LRD	0.005	20	0.2		Copper Cu mg/kg	LRD	1.3	0	0.0		Tin Sn mg/kg	LRD	0.5	0	0.0
	SEEN	0.005	12	0.8			SEEN	1.3	0	0.0			SEEN	0.5	0	0.0
	LOND	0.005	8	0.1			LOND	1.3	0	0.0			LOND	0.5	0	0.0
Sodium oxide Na2O %	LRD	0.3	447	5.3		Gallium Ga mg/kg	LRD	1	0	0.0		Strontium Sr mg/kg	LRD	1	0	0.0
	SEEN	0.3	167	10.4			SEEN	1	0	0.0			SEEN	1	0	0.0
	LOND	0.3	280	4.1			LOND	1	0	0.0			LOND	1	0	0.0
Phosphorous pentoxide P2O5 %	LRD	0.05	16	0.2		Germanium Ge mg/kg	LRD	0.5	384	4.6		Thorium Th mg/kg	LRD	0.7	3	0.0
	SEEN	0.05	15	0.9			SEEN	0.5	109	6.8			SEEN	0.7	1	0.1
	LOND	0.05	1	0.0			LOND	0.5	275	4.0			LOND	0.7	2	0.0
Silica SiO2 %	LRD	0.1	0	0.0		Hafnium Hf mg/kg	LRD	1	0	0.0		Uranium U mg/kg	LRD	0.5	43	0.5
	SEEN	0.1	0	0.0			SEEN	1	0	0.0			SEEN	0.5	1	0.1
	LOND	0.1	0	0.0			LOND	1	0	0.0			LOND	0.5	42	0.6
Titanium dioxide TiO2 %	LRD	0.01	0	0.0		Iodine I mg/kg	LRD	0.5	15	0.2		Vanadium V mg/kg	LRD	3	0	0.0
	SEEN	0.01	0	0.0			SEEN	0.5	3	0.2			SEEN	3	0	0.0
	LOND	0.01	0	0.0			LOND	0.5	12	0.2			LOND	3	0	0.0
Element Symbol Units	-Data-	-LLD-	-n<LLD-	-%<LLD-	.	Element Symbol Units	-Data-	-LLD-	-n<LLD-	-%<LLD-	.	Element Symbol Units	-Data-	-LLD-	-n<LLD-	-%<LLD-
Silver Ag mg/kg	LRD	0.5	1232	14.7		Lanthanum La mg/kg	LRD	1	0	0.0		Tungsten W mg/kg	LRD	0.6	219	2.6
	SEEN	0.5	175	10.9			SEEN	1	0	0.0			SEEN	0.6	81	5.1
	LOND	0.5	1057	15.5			LOND	1	0	0.0			LOND	0.6	138	2.0
Arsenic As mg/kg	LRD	2.4	9	0.1		Molybdenum Mo mg/kg	LRD	0.2	18	0.2		Yttrium Y mg/kg	LRD	1	0	0.0
	SEEN	2.4	5	0.3			SEEN	0.2	11	0.7			SEEN	1	0	0.0
	LOND	2.4	4	0.1			LOND	0.2	7	0.1			LOND	1	0	0.0
Barium Ba mg/kg	LRD	1	0	0.0		Niobium Nb mg/kg	LRD	1	0	0.0		Zinc Zn mg/kg	LRD	1.3	3	0.0
	SEEN	1	0	0.0			SEEN	1	0	0.0			SEEN	1.3	1	0.1
	LOND	1	0	0.0			LOND	1	0	0.0			LOND	1.3	2	0.0
Bismuth Bi mg/kg	LRD	0.3	4490	53.5		Neodymium Nd mg/kg	LRD	4	19	0.2		Zirconium Zr mg/kg	LRD	1	0	0.0
	SEEN	0.3	918	57.4			SEEN	4	14	0.9			SEEN	1	0	0.0
	LOND	0.3	3572	52.5			LOND	4	5	0.1			LOND	1	0	0.0
Bromine Br mg/kg	LRD	0.8	0	0.0		Nickel Ni mg/kg	LRD	1.3	3	0.0		.
	SEEN	0.8	0	0.0			SEEN	1.3	3	0.2
	LOND	0.8	0	0.0			LOND	1.3	0	0.0

Table 4 List of elements determined by XRFS not reported in the London Region Atlas of Topsoil Geochemistry. The lower limit of detection (LLD), the number of samples below the LLD (n<LLD) and the n<LLD in percent (%<LLD) are shown for the London Region Dataset (LRD), and the two subsets (SEEN and LOND). Number of samples (N) is as follow: LRD = 8400, SEEN = 1599 and LOND = 6801.

Element Symbol Units	Data	LLD	n<LLD	%<LLD	.	Element Symbol Units	Data	LLD	n<LLD	%<LLD	.	Element Symbol Units	Data	LLD	n<LLD	%<LLD
Chlorine Cl mg/kg	LRD	200	8378	99.7		Tellurium Te mg/kg	LRD	0.5	8347	99.4		Samarium Sm mg/kg	LRD	3.0	3217	38.3
	SEEN	200	1596	99.8			SEEN	0.5	1583	99.0			SEEN	3.0	533	33.3
	LOND	200	6782	99.7			LOND	0.5	6764	99.5			LOND	3.0	2684	41.9
Indium In mg/kg	LRD	0.5	8348	99.4		Mercury Hg mg/kg	LRD	0.5	6921	82.4		Thallium Tl mg/kg	LRD	0.5	6054	72.1
	SEEN	0.5	1586	99.2			SEEN	0.5	1513	94.6			SEEN	0.5	1049	65.6
	LOND	0.5	6762	99.4			LOND	0.5	5408	79.5			LOND	0.5	5005	78.2
Sulphur S mg/kg	LRD	2000	8243	98.1		Tantalum Ta mg/kg	LRD	1.0	7741	92.9		Ytterbium Yb mg/kg	LRD	1.5	2520	30.0
	SEEN	2000	1586	99.2			SEEN	1.0	1368	85.6			SEEN	1.5	371	23.2
	LOND	2000	6657	97.9			LOND	1.0	6373	93.7			LOND	1.5	2149	33.6

Table 5 Nested ANOVA results for the London Region Data topsoil duplicate and replicate sets. The number of sites indicate the number of locations with duplicate and replicate samples. Results below the lower limit of detection are excluded from the ANOVA analysis (Johnson et al., 2010). Elements are ordered according to their performance in the nested ANOVA test. Shaded elements were excluded from the atlas after this test.

Element	Between-site %	Within-site %	Within-sample %	Number of sites	.	Element	Between-site %	Within-site %	Within-sample %	Number of sites
Nb	94.5	4.2	1.3	171		MnO	84.2	13.1	2.7	171
K2O	93.3	6.4	0.3	171		As	83.8	13.4	2.8	171
Rb	93.1	6.6	0.3	171		P2O5	82.5	16.6	0.9	171
La	92.0	6.0	2.0	171		Ba	82.3	15.3	2.4	171
TiO2	91.6	7.1	1.3	171		Na2O	82.3	10.2	7.5	124
Ce	91.0	7.4	1.6	171		Co	82.1	10.6	7.3	171
Ga	90.7	6.3	2.9	171		Cs	81.7	4.5	13.7	171
MgO	90.7	8.4	0.9	168		W	80.1	5.5	14.4	166
Y	90.6	7.0	2.4	171		Ni	79.9	16.2	3.9	171
Al2O3	90.5	8.7	0.7	171		Cu	79.6	17.8	2.6	171
V	90.5	8.3	1.2	171		Zn	77.0	20.9	2.0	171
Th	89.4	6.2	4.4	171		Sc	76.4	9.3	14.2	165
Zr	88.9	9.4	1.7	171		Sb	75.9	14.9	9.2	170
CaO	88.3	10.3	1.3	171		Sn	75.0	16.4	8.5	171
Fe2O3	88.1	8.8	3.1	171		U	72.1	5.5	22.3	165
Mo	88.1	8.9	3.0	151		Se	66.7	14.9	18.4	171
Sr	88.0	10.5	1.5	171		Cd	62.9	24.7	12.4	108
Nd	86.6	7.5	5.9	170		Ge	62.3	17.8	20.0	168
Br	86.4	11.4	2.2	171		Ag	58.9	30.9	10.2	26
Hf	86.0	7.1	6.9	171		Bi	52.2	28.1	19.7	55
Pb	85.3	10.7	4.0	171		Yb	34.8	5.3	59.8	99
I	85.2	8.8	6.0	171		Hg	29.7	55.2	15.1	39
SiO2	85.0	12.5	2.5	171		Sm	25.7	4.5	69.8	166
Cr	85.0	13.9	1.2	171		Tl	16.6	-8.6	91.9	65
						Ta	15.3	3.0	81.7	54

Quality control

G-BASE analytical results are subjected to rigorous quality control procedures described in detail elsewhere (Lister and Johnson, 2005; Johnson, 2011). The entire process, from field procedures to sample preparation and analysis in the laboratory is designed to minimise errors. Systematic errors are able to be checked because a randomised number is assigned to samples on collection.

Accuracy, precision and long-term analytical drift is assessed by including BGS XRF laboratory primary and secondary certified reference materials (CRMs) along with every batch of 500 samples in the analytical runs. Secondary CRMs allow any between batch bias to be identified and corrected. Primary CRMs ensure that bias from the 'true' result is minimized. Primary and secondary reference materials have been used routinely to assess the quality of regional geochemical data since the UK national mapping programme commenced in the 1960s (Lister and Johnson, 2005; Johnson et al., 2008). This ensures a ‘seamless’ continuation of geochemical data across large regions for samples collected over many field campaigns and analysed by different analytical instruments. All data in this London Region Geochemical Dataset are levelled using four accredited reference materials (GSD-7, GSS-1, LKSD-1, LKSD-4). Certified values (in red) together with the values reported by the BGS XRF laboratory are shown in Table 6.

A previously unrecognised analytical interference between high topsoil Pb concentration and U measurement in the London Earth results, where high Pb was suppressing the U results, has been corrected in this London Region dataset.

The G-BASE project also inserts field duplicate and laboratory replicate samples in every batch of fifty (urban) or one hundred (rural) samples. The laboratory replicate is a sub-sample of the same sample taken before analysis, whilst a field duplicate is a second sample collected in the field at the same location as a regular sample. These two control samples allow assessment of the analytical and sampling variability respectively and comparison to the total variability. This provides a check that the local (within-site) ‘noise’ is low enough so that the regional patterns (between sites) are distinguishable and reliable. This was achieved by performing a nested unbalanced analysis of variance (ANOVA) using these duplicate and replicate samples (Johnson, 2002). The validity of the nested ANOVA depends on the representativeness of the duplicates and replicates, and it may not be valid if a large number of samples have element concentrations that are near or below the LLD. Nevertheless, results give an indication of the elements for which the natural geochemical variability is significantly higher than the variability related to the sampling and analytical procedures. The higher the percentage of total variability attributed between sites, the higher the confidence in the results (Table 5). For elements with a value above 80% the sampling and analytical methodology is considered suitable, as it does not introduce too much 'background noise'. As between-site variability decreases from 80% down to about 50%, increasing caution must be taken during statistical analysis and/or interpretation. Elements showing a between-site variability below 50% (Yb, Hg, Sm, Tl and Ta) are not considered further in the LRA, as already explained under the Sample preparation and analysis section of this atlas.

Table 6 Summary of primary reference material results for soil samples XRFS analyses in the London Region Atlas of Topsoil Geochemistry. Units for elements shown as oxides are wt% and mg/kg otherwise.

Elements by XRF-ED
CRM ID	.	Ag	Cert Ag	.	Cd	Cert Cd	.	In	Cert In	.	Sn	Cert Sn	.	Sb	Cert Sb	.	I	Cert I	.	Cs	Cert Cs	.	Ba	Cert Ba	.	La	Cert La	.	Ce	Cert Ce
GSD-7		1.4	1.1		0.9	1.1		not detected	no data		4.8	5.4		2.8	2.6		0.9	no data		5	6		740	720		45	45		82	78.0
GSS-1		0.4	0.4		4.4	4.3		not detected	no data		5.9	6.1		1.0	0.9		1.9	1.9		9	9		587	590		34	34		68	70.0
LKSD-1		0.5	0.6		1.1	1.2		0.5	no data		15.2	16.0		0.9	1.2		1.7	no data		1	2		396	430		14	16		25	27.0
LKSD-4		0.1	0.2		1.9	1.9		not detected	no data		4.6	5.0		1.3	1.7		9.5	no data		2	2		262	330		21	26		38	48.0

Elements by XRF-WDT
CRM ID	.	K2O	Cert K2O	.	CaO	Cert CaO	.	TiO2	Cert TiO2	.	MnO	Cert MnO	.	Fe2O3	Cert Fe2O3	.	S	Cert S	.	Cl	Cert Cl	.	Sc	Cert Sc
GSD-7		3.64	3.54		1.65	1.67		0.707	0.747		0.093	0.089		6.50	6.51		646	190		83	no data		13.7	14.6
GSS-1		2.53	2.59		1.75	1.72		0.766	0.805		0.238	0.227		5.18	5.19		847	310		114	78		10.4	11.2
LKSD-1		1.06	1.10		12.14	10.80		0.448	0.500		0.093	0.100		4.03	4.10		9306	1570		430	no data		6.5	9.0
LKSD-4		0.76	0.80		1.85	1.80		0.299	0.400		0.068	0.100		4.20	4.10		5952	999		215	no data		7.1	7.0
CRM ID	.	V	Cert V	.	Cr	Cert Cr	.	Co	Cert Co	.	Ni	Cert Ni	.	Cu	Cert Cu	.	Zn	Cert Zn	.	Ga	Cert Ga	.	Ge	Cert Ge
GSD-7		93.4	96.0		119.3	122.0		20.6	21.0		55.6	53.0		36.1	38.0		246.2	238.0		16.7	17.7		0.9	1.4
GSS-1		80.7	86.0		60.0	62.0		13.9	14.2		20.7	20.4		19.7	21.0		671.6	680.0		17.6	19.3		0.6	1.3
LKSD-1		47.8	50.0		27.0	31.0		11.0	11.0		16.0	16.0		40.6	44.0		322.4	331.0		9.0	no data		0.1	no data
LKSD-4		45.5	49.0		30.1	33.0		11.7	11.0		34.1	31.0		30.1	31.0		194.3	194.0		7.9	no data		0.5	no data
CRM ID	.	As	Cert As	.	Se	Cert Se	.	Br	Cert Br	.	Rb	Cert Rb	.	Sr	Cert Sr	.	Y	Cert Y	.	Zr	Cert Zr	.	Nb	Cert Nb
GSD-7		83.7	84.0		0.2	0.3		0.6	no data		146.4	147.0		222.4	220.0		24.9	24.0		156.9	162.0		15.1	17.0
GSS-1		35.8	33.5		0.1	0.1		2.5	2.9		137.9	140.0		156.6	155.0		24.9	25.0		250.1	245.0		14.7	16.6
LKSD-1		34.9	40.0		1.0	no data		10.3	11.0		22.7	24.0		259.4	250.0		20.9	19.0		132.8	134.0		4.0	7.0
LKSD-4		16.6	16.0		2.3	no data		50.6	49.0		25.0	28.0		121.0	110.0		22.2	23.0		101.3	105.0		4.3	9.0
CRM ID	.	Mo	Cert Mo	.	Nd	Cert Nd	.	Sm	Cert Sm	.	Yb	Cert Yb	.	Hf	Cert Hf	.	Ta	Cert Ta	.	W	Cert W	.	Hg	Cert Hg
GSD-7		1.3	1.4		34.1	37.0		4.4	6.1		2.2	2.6		5.0	4.9		0.8	1.4		6.5	5.5		-0.3	0.1
GSS-1		1.1	1.4		26.3	28.0		3.9	5.2		2.1	2.7		7.7	6.8		0.5	1.4		4.6	3.1		-0.8	0.0
LKSD-1		9.4	10.0		19.4	16.0		2.9	4.0		1.7	2.0		4.1	3.6		-0.2	0.3		1.7	<4		-0.6	0.0
LKSD-4		1.3	<5		27.1	25.0		4.3	5.0		2.1	2.0		3.1	2.8		-0.1	0.4		1.8	<4		-0.5	no data
CRM ID	.	Tl	Cert Tl	.	Pb	Cert Pb	.	Bi	Cert Bi	.	Th	Cert Th	.	U	Cert U
GSD-7		0.7	0.9		361.1	350.0		0.6	0.7		12.6	12.6		3.4	3.5
GSS-1		0.7	1.0		98.2	98.0		0.7	1.2		11.4	11.6		3.7	3.3
LKSD-1		0.1	no data		83.7	82.0		0.6	no data		2.1	2.2		9.7	9.7
LKSD-4		0.8	no data		97.3	91.0		0.0	no data		5.1	5.1		31.4	31

Elements by XRF-WDM
CRM ID	.	Na2O	Cert Na2O	.	MgO	Cert MgO	.	Al2O3	Cert Al2O3	.	SiO2	Cert SiO2	.	P2O5	Cert P2O5	.	SO3	Cert SO3
GSD-7		1.2	1.2		4.3	3.1		14.6	13.4		67.3	64.7		0.21	0.19		not detected	no data
GSS-1		1.4	1.7		2.1	1.8		14.1	14.2		57.4	62.6		0.18	0.17		0.1	0.08
LKSD-1		1.6	2.0		1.8	1.7		5.6	7.8		31.5	40.1		0.16	0.20		2.6	no data
LKSD-4		0.5	0.7		1.0	0.9		5.2	5.9		45.2	41.6		0.36	0.30		2.1	no data