| dc.description | Selenium is an essential trace element in regard to human and other animals' health, but it presents a narrow range of dietary deficiency and toxic excess. Some phosphate rocks are rich in selenium. Furthermore it is necessary to control selenium's and other trace elements’ compositions in the phosphate rocks, because phosphorite ores of different geographical sites are varied, and even ores from the same outcrop can vary substantially in trace element levels. Data of trace element composition of phosphorites from Bayovar–Sechura (Northern, Peru, 06°05'S and 80°50'W) is scarce and incomplete. In this paper 19 trace element concentrations are reported. Aqua regia extracts were used to estimate the “pseudototal” values of 19 elements, following standard procedures (ISO 11466, 2002) and measured by ICP-AES and ICP-MS. In decreasing order of mean abundance (mg kg− 1) are: Sr (1117) > Cr (134) > B (76.8) > Zn (65.4) > V (49.2) > U (44.9) > Mo (30.4) > Cd (17.3) > Cu (17.0) > Ni (16.8) > Co (15.4) > As (14.3) > Pb (5.8) > Se (2.4) > Th (2.2) > Sn (0.81) > Sb (0.63) > Tl (0.43) > Ag (0.22). The concentration (mg kg− 1) of Se in Bayovar–Sechura phosphorites is: mean 2.4 ± 1.2, median 2 and range 0.5–6. Selenium is enriched in the phosphorite (factor 4). Selenium shows significant positive correlations with As, B, Cr, Mo, Sr, Th and U, and negative with Ag, Sn and Tl. Cadmium concentration (mg kg− 1) is: 17.3 ± 10.9, median 8.5 and range 2–53. These levels are analogous to those of average phosphorites. Uranium and Th concentrations (mg kg− 1) are 44.9 and 2.2, respectively, versus 120 and 6.5 of the average phosphorites. Molybdenum level (mg kg− 1) is a high 30.4 versus 9 of average phosphorite. This concentration is very useful in Mo deficient soils application. | |
