Hans J. Brumsack

Rare earth elements in Japan Sea sediments and diagenetic behavior of Ce/Ce*: Results from ODP Leg 127

The relative effects of paleoceanographic and paleogeographic variations, sediment lithology, and diagenetic processes on the recorded rare earth element (REE) chemistry of Japan Sea sediments are evaluated by investigating REE total abundances and relative fractionations in 59 samples from Ocean Drilling Program Leg 127. REE total abundances (ΣREE) in the Japan Sea are strongly dependent upon the paleoceanographic position of a given site with respect to terrigenous and biogenic sources. REE concentrations at Site 794 (Yamato Basin) overall correspond well to aluminosilicate chemical indices and are strongly diluted by SiO2 within the late Miocene-Pliocene diatomaceous sequence. EuEu∗ values at Site 794 reach a maximum through the diatomaceous interval as well, most likely suggesting an association of EuEu∗ with the siliceous component, or reflecting slight incorporation of a detrital feldspar phase. ΣREE at Site 795 (Japan Basin) also is affiliated strongly with aluminosilicate phases, yet is diluted only slightly by siliceous input. At Site 797 (Yamato Basin), REE is not as clearly associated with the aluminosilicate fraction, is correlated moderately to siliceous input, and may be sporadically influenced by detrital heavy minerals originating from the nearby rifted continental fragment composing the Yamato Rise. The biogenic influence is largest at Site 794, moderately developed at Site 797, and of only minor importance at Site 795, reflecting basinal contrasts in productivity such that the Yamato Basin records greater biogenic input than the Japan Basin, while the most productive waters overlie the easternmost sequence of Site 794. CeCe∗ profiles at all three sites increase monotonically with depth, and record progressive diagenetic LREE fractionation. The observed CeCe∗ record does not respond to changes in oxygenation state of the overlying water, and CeCe∗ correlates slightly better with depth than with age. The downhole increase in CeCe∗ at Site 794 and Site 797 is a passive response to diagenetic transfer of LREE (except Ce) from sediment to interstitial water. At Site 795, the overall lack of correlation between CeCe∗ and LanYbn suggests that other processes are occurring which mask the diagenetic behavior of all LREEs. First-order calculations of the Ce budget in Japan Sea waters and sediment indicate that ~20% of the excess Ce adsorbed by settling particles is recycled within the water column, and that an additional ~38% is recycled at or near the seafloor (data from Masuzawa and Koyama, 1989). Thus, because the remaining excess Ce is only ~10% of the total Ce, there is not a large source of Ce to the deeply buried sediment, further suggesting that the downhole increase in CeCe∗ is a passive response to diagenetic behavior of the other LREEs. The REE chemistry of Japan Sea sediment therefore predicts successive downhole addition of LREEs to deeply-buried interstitial waters.

Heavy metal contamination and health risk assessment in waste mine water dewatering using phosphate beneficiation processes in Jordan

Phosphate production is one of the major industries in Jordan. Phosphate beneficiation processing consume large quantities of its limited fresh water resources for processes such as washing and flotation. The process of mine water effluents have long been contained with remarkably high levels of heavy metals (e.g., Cd, Cr, Mn, Mo, Ni, Pb, U, V, and Zn), making them toxic for human health and surrounding environemnt. The main objective of this study was to determine the heavy metal contamination in washing mine water of phosphate bed-A1 (WMW-A1) and flotation mine water of phosphate bed-A3 (FMW-A3) of a Jordan phosphate mine (Eshidiya), to assess the health risks associated with oral daily intake and dermal absorption of mine water effluents from phosphate mining process. The results indicated accumulations of Cd, Cr, Li, Mn, Mo, Ni, Pb, U, V, and Zn in the mine water, with lower concentrations than the Jordan standards for discharge of water bodies into streams. In particular, Mn and Cr exhibited high levels of pollution in mine water due to their slightly higher contamination index values (CI). This can be interpreted to variation in geochemical behavior of these metal contents naturally present in francolite mineral phase. Varimax rotated factor analysis, cluster analysis, and correlation analysis revealed that Cd, Cr, Li, Mn, Mo, Ni, Pb, U, V, and Zn in mine water were mainly related to geochemical behavior for francolite mineral phase and clay mineral phase represents the main source of mine water contamination. The hazard quotient (HQ) and hazard index (HI) values were assessed to determine health risk (e.g., non-carcinogenic risk and cancer risk) in case of daily intake and dermal exposure pathways in mine water. The health risk assessment showed that As, Hg, Ni, Pb, and Zn are < 1, indicating non-carcinogenic risk tends to become significant for daily intake and dermal exposure pathways by the mine water. The cancer risk of being exposed to lead through WMW-A1 and FMW-A3 from these sources did not exceed the acceptable risk limits of 1:10,000 for regulatory purposes. Overall, this study provides comparative research on the accumulation, potential health risks and sources of heavy metals in mine water (washing and flotation) beneficiation process in Eshidiya mines, and our findings suggest that, Mn and Cr in both mine water could potentially represent environmental problems.