Table 1.
Summary of USGS laboratory analytical results for total chemical composition.
| Sample type (n samples) | Lead ppm [range (median)] | Mercury ppm [range (median)] | Manganese ppm [range (median)] | Arsenic ppm [range (median)] | Antimony ppm [range (median)] |
|---|---|---|---|---|---|
| Raw ores (189 spot analyses) | <0.3–333,000 (185) | 0.5–25 (4.0) | <17–1,447 (16.7) | <0.5–73,497 (57.4) | <1–3,188 (62) |
| Processed ores | |||||
| Crushed, ground, washed ores (6) | 305–180,000 (10,200) | 0.1–0.9 (0.3) | 71–1,320 (722) | 2.5–69 (14) | 6.9–60 (22.5) |
| Sluiced ores (1) | 112,000 | 7 | 550 | 110 | 366 |
| Soils from ore sluicing, ore washing areas | |||||
| Dareta (3) | 5,420–58,900 (54,400) | 2.1–12.6 (2.4) | 694–859 (749) | 8.5–140 (140) | 31.2–435 (389) |
| Yargalma (5) | 27,700–39,200 (29,800) | 13.8–15.1 (14.5) | 235–413 (391) | 20.4–76 (22) | 174–344 (279) |
| Sweep samples | |||||
| Dareta (17) | 78–185,000 (3,250) | 0.05–68.1 (0.5) | 256–1,040 (500) | 1.5–27 (3.8) | 0.7–79 (9.1) |
| Yargalma (15) | 1,510–132,000 (33,700) | 1.0–44.0 (5.9) | 196–649 (309) | 4.7–270 (44) | 13.7–1,250 (189) |
| Village soils | |||||
| Dareta (4) | 1,560–69,700 (27,400) | 0.7–15.2 (2.4) | 703–1,060 (851) | 5.3–150 (31.5) | 9.5–431 (89) |
| Yargalma (3) | 7,450–8,490 (7,630) | 2.7–3.9 (2.9) | 433–625 (470) | 22–76 (33) | 54–144 (77) |
| Village outskirt soils | |||||
| Dareta (1) | 122 | 0.3 | 620 | 3.3 | 431 |
| Yargalma (1) | 293 | 0.2 | 284 | 2.8 | 3 |
| Village soils, no ore processing (5) | 12–25 (19) | 0.01–0.1 (0.02) | 113–419 (255) | 2–11.2 (2.4) | 0.1–6.9 (0.3) |
| RSSL (U.S. EPA 2002a, 2011a) | 400 | 10–23a | 390 | 0.39 | 31 |
| Zamfara plant foodstuff samples | |||||
| Processed samples (16) | 0.1–146 (1.5) | 0.02–0.45 (0.07) | 7.5–136 (22.3) | <0.05–0.91 (739) | 0.7–1.4 (0.95) |
| Raw samples (23) | <0.05–1.86 (0.39) | 0.01–0.15 (0.06) | 3.4–242 (14.6) | <0.05–0.45 (0.27) | 0.3–1.4 (0.94) |
| Plant standard reference materials | |||||
| NIST wheat 1567a | <0.05 | 0.006 | 7.6 | <0.05 | 1 |
| NIST rice 1568a | <0.05 | 0.0005 | 18.5 | <0.05 | 0.9 |
| NIST samples from National Institute of Standards and Technology, Gaithersburg, MD, USA. Analytical methods used for raw ores: handheld XRF in lab; for processed ores, all soils, sweep samples: ICP-MS, mercury by CVAFS; for plant foodstuffs: ICP-AES, mercury by CVAFS. aRange is for elemental (10) to salt (23) forms. | |||||