The geochemistry of manganese (Mn) in seawater is dominated by its redox chemistry, as Mn(II) is soluble and Mn(IV) forms insoluble oxides, and redox transformations are mediated by a variety of processes in the oceans. Dissolved Mn (DMn) accumulates under reducing conditions and is depleted under oxidizing conditions. Thus the Peruvian upwelling region, characterized by highly reducing conditions over a broad continental shelf and a major oxygen minimum zone extending far offshore, is potentially a large source of Mn to the eastern Tropical South Pacific. In this study, DMn was determined on cruises in October 2005 and February 2010 in the Peruvian Upwelling and Oxygen Minimum Zone, to evaluate the relationship between Mn, oxygen and nitrogen cycle processes. DMn concentrations were determined using simple dilution and matrix-matched external standardization inductively coupled mass spectrometry. Surprisingly, DMn was depleted under the most reducing conditions along the Peruvian shelf. Concentrations of dissolved Mn in surface waters increased offshore, indicating that advection of Mn offshore from the Peruvian shelf is a minor source. Subsurface Mn maxima were observed within the oxycline rather than within the oxygen minimum zone (OMZ), indicating they arise from remineralization of organic matter rather than reduction of Mn oxides. The distribution of DMn appears to be dominated by non-redox processes and inputs from the atmosphere and from other regions associated with specific water masses. Lower than expected DMn concentrations on the shelf probably reflect limited fluvial inputs from the continent and efficient offshore transport. This behavior is in stark contrast to Fe, reported in a companion study which is very high on the shelf and undergoes dynamic redox cycling. (C) 2014 Elsevier Ltd. All rights reserved.

Vertical profiles of total dissolved iron (DFe), Fe(II), and hydrographic parameters were obtained along three transects across the continental shelf off Peru in October 2005. Fe(II) and DFe concentrations were determined using luminol chemiluminescence and isotope dilution inductively coupled plasma mass spectrometry (ICP-MS), respectively. The objective was to study the relationships among redox chemistry, nitrogen-cycle processes, bottom topography, and the distribution and chemistry of iron in the region. The results are the most thorough survey to date of Fe geochemistry in this region. Exceedingly high DFe (similar to 50-75 nmol L-1) was measured over the wide northern continental shelf, with most of the dissolved Fe present as Fe(II) below the oxycline. In southern Peru, the shelf is narrower, and dissolved Fe concentrations were 10-fold lower. Moreover, a smaller fraction of the dissolved Fe was present as Fe(II) in the south, even below the oxycline. At the western ends of the transects, Fe(II) maxima were coincident with deep (i.e., secondary) nitrite maxima. This suggests a relationship between nitrate reduction and Fe(II) accumulation in the water column. However, over the shelf, Fe(II) was also influenced by benthic processes. Large lateral gradients in dissolved Fe across the shelf-slope break reflect Fe removal by oxidative scavenging, and it seems plausible that much of the Fe is "trapped" by redox cycling on the shelf. Nevertheless, the maintenance of dissolved Fe(II) filaments within the secondary nitrite maxima constitutes an important mechanism for Fe transport offshore.

Typha angustata L. is a wetland plant commonly found in the marshy land or flood planes of the Ganges riverine system. A field study was taken on T angustata L. to evaluate the uptake and transport of heavy metals (Mn, Cu, Zn, Cr, Ni and Pb) in different parts of plants grown on waste amended soils in water logged condition for 3 months. T angustata L. accumulated Mn, Cu, Zn, Cr, Ni and Pb up to 119.21 +/- 5.8 mu g g(-1), 4.18 +/- 0.5 mu g g(-1), 5.72 +/- 1.1 mu g g(-1), 15.4+1.9 mu g g(-1), 5.3 0.8 mu g g(-1) and 7.21 +/- 0.9 mu g g(-1) in below ground organ (BL) respectively. Whereas, the maximum metal contents in above ground organ (AG) were 43.86 +/- 3.2 mu g g(-1), 1.73 +/- 0.04 mu g g(-1), 2.11 +/- 0.07 mu g g(-1), 6.31 +/- 0.3 mu g g(-1), 1.8 +/- 0.04 mu g g(-1) and 2.75 +/- 0.03 mu g g(-1) respectively. The plant also retained the tissue nitrogen up to 6.1 +/- 0.38% in BL and 9.82 +/- 0.54% in AG. It accumulated the maximum concentration of phosphorus 0.25 +/- 0.02% in BL and 0.41 +/- 0.02% in AG. Metals in both BL and AG were enriched with exposure, but the translocation factor was higher in BL in all amendments. Metal translocation factor was higher in BL/soil than AG/soil to a large extent. The translocation factor of metal from water to below ground organ was higher than water to above ground organ with a maximum value for Cr. There is a strong positive correlation of metal contents in plant tissue with soil organic matter (OM), and phosphorus contents in plant tissue. There is no significant correlation between metal uptake and nitrogen contents in plant tissue. This study reveals that T angustata L can be used for remediation of heavy metals containing waste when used in 25% waste amendment. (c) 2008 Elsevier B.V. All rights reserved.