| Order | Study area | No. of samples | Sample collection method | Method Instrument | | Reference | Period | Soil depth (cm) | Grid | Reference materials used |
| 1 | Albania | 21 | Jul ‘95 | 0–15 | — | ICP-AES | CRMs-BCR 142R | [11] | 2 | Algeria | 119 | Jan-Feb ‘06 | — | km | FAASa, GFSb | CRM 141 R, SRM 2709 SJS | [12] | 3 | Australia | 25 | Dec ‘00–Feb ‘01 | 0–5 and 5–20 | — | ICP-MS | CRMs-AGAL 10, AGAL 11 | [13] | 4 | Belgium | 27 | ‘93–‘98 | 0–20 | 10 m interval | ICP-MS, ICP-AES | CRMs-SRM2710, GBW07411, | [14] | | | | | | | | GBW07311 & SRM1633 | | 5 | Bulgaria | 14 | Jun ‘04 | — | — | XRF | — | [15] | 6 | Kosovo | 82 | Jun–Nov ‘02 | — | 1×1 km | XRF, ICP-MS | CRMs-BR, DR-N, GH, DTS-1, | [16] | | | | | | | | SDO-1, AGV-2, NIST 2709, 2710 | | 7 | Greece | 30 | ‘93–‘94 | — | — | INAAc & AAS | IAEA SOIL-7, Pepperbush SRM | [17] | 8 | Italy | 280 | — | 0–5 | — | ICP-MS | — | [18] | 9 | Jordan | 3 | Sept ‘03 | 0–20 and 20–40 | — | AAS | — | [19] | 10 | Peru | 6 | — | 0–10 | — | ICP-ES | — | [20] | 11 | Slovenia | 40 | — | 0–25 | — | FAAS | WEPAL 2004.3.3 | [21] | 12 | UK | 70 | — | 0–15 | 1 km interval | FAAS | — | [22] | 13 | Bangladesh | 53 | Nov ‘95 | 0–5 and 5–15 | — | AAS | — | [23] | 14 | India | 30 | ‘02–‘04 | — | — | XRF | SO-1, SO-2, SO-3, SO-4, NGRI-D, | [24] | | | | | | | | NGRI-U | | 15 | Spain | 24 | Winter ‘07 | 0–5 | — | ICP-MS & AAS-GF | CRM 052 | [25] | 16 | Spain | 27 | Winter ‘05 | 0–3 | — | ICP-MS | Lobster hepatopancreas | [26] | 17 | Turkey | 29 | Sep ‘03 | — | — | FAAS | SRM - BCR-701 | [27] | 18 | China | 50 | — | 0–10 | 20 m × 20 m | XRF | GSS, GRS, GSD, SO-1, NIST-2709, | [28] | | | | | | | | NIST-2710, NIST-2711 | | 20 | Jordan | 31 | — | 0–10 and 10–20 | — | AAS | NBS SRMs | [29] | 21 | Pakistan | 38 | Oct ‘03–Dec ‘03 | 1–5 | — | AAS | SRM-SR-96 | [30] | 22 | Serbia | 59 | Jun ‘99–Mar ‘00 | 0–5 | — | FAAS | — | [31] | 23 | Damascus | 51 | Summer ‘98 | 0–20 | — | FAAS | — | [32] |
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