Stable isotope signatures are emerging quickly as a powerful technique to study metal uptake and translocation in plants. Fundamental to this development is a thorough understanding of the processes that lead to isotope fractionation under differing environmental conditions. In this study, we investigated zinc (Zn) and iron (Fe) isotope fractionation in rice grown to maturity in anaerobic and aerobic soils under greenhouse conditions. The overall Zn isotope fractionation between the soil and above-ground plant material was negligible in aerobic soil but significant in anaerobic soil with isotopically lighter Zn in the rice plant. The observed range of fractionation was in line with previously determined fractionations of Zn in rice grown in hydroponic solutions (Weiss et al., 2005, New Phytol. 165, 703-710) and submerged soils (Arnold et al, 2010, Plant Cell Environ. 33, 370-381) and emphasizes the effect of taking up different chemical forms of Zn, most likely free and organically complexed Zn, on the isotopic signature found in the plant. The Zn in the grain was isotopically lighter than in the rest of the above-ground plant in rice grown in aerobic and anaerobic soils alike. This demonstrates that in the course of the grain loading and during translocation within the plant important biochemical and/or biophysical processes occur. The isotope fractionation observed in the grains would be consistent with a unidirectional controlled transport from shoot to grain fractionation with a fractionation factor of α ≈ 0.9994. Iron isotopes showed an isotopic lighter signature in shoot and grain compared to the bulk soil or the leach in both soil environments alike. The negative direction of isotopic fractionation is consistent with possible changes in redox state of the Fe during uptake and translocation. The isotope fractionation pattern between shoots and grain material are different for Zn and Fe which finally suggests that different mechanisms operate during translocation and grain loading in rice for these two key micronutrients. Stable isotope fractionation is emerging quickly as a powerful novel technique to study metal 25 uptake and translocation in plants. Fundamental to this development is a thorough under-26 standing of the processes that lead to isotope fractionation under differing environmental con-27 ditions. In this study, we investigated Zn and Fe isotope fractionation in rice grown to maturity 28 in anaerobic and aerobic soils under greenhouse conditions. The overall Zn isotope fractiona-29 tion between the soil and above-ground plant material was negligible in aerobic soil but signifi-30 cant in anaerobic soil with isotopically lighter Zn in the rice plant. The observed range of frac-31 tionation was in line with previously determined fractionations of Zn in rice grown in hydro-32 ponic solutions (Weiss et al., 2005, New Phytol. 165, 703-710) and submerged soils (Arnold T et 33 al, 2010, Plant Cell Environ. 33, 370-381)

This document is confidential and is proprietary to the American Chemical Society and its authors. Do not copy or disclose without written permission. If you have received this item in error, notify the sender and delete all copies. Experimental determination of zinc isotope fractionation in complexes with the phytosiderophore 2'-deoxymugeneic acid (DMA) and its structural analogues, and implications for plant uptake mechanisms

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To understand groundwater flow and geochemical processes within an aquifer, it is necessary to set up a conceptual model of the aquifer. To accomplish this, different methods are used, and one of them is an isotopic technique. The study area is located in the Varaždin area (NW Croatia). The aquifer represents the main source of potable water for the town of Varaždin and the surrounding settlements. The conceptual model of the alluvial aquifer has to be set up prior to creating a groundwater flow and transport model. Measurements of ratios δ18Ο and δ2H in ground- and surface waters and precipitation samples were carried out. The relationship between ratios δ18Ο, δ2H, and d-excess for local precipitation in the study area showed that precipitation originates from the Atlantic air masses, although during the colder periods of the year, influence of the Mediterranean air masses was not negligible. The monitored period was warmer and wetter than average. Evaporation was observed at all monitored surface waters, but the largest rate was at the location of a gravel pit in Šijanec. The isotopic composition of the precipitation and groundwater showed a good correlation due to the isotopic homogenization of groundwater along the flow path.

Eastern coast of the Adriatic Sea consists of karstified carbonates. It belongs to the well-known Dinaric karst region. The coast is extremely indented and there are 718 islands with numerous rock crags and reefs. Some of the inhabited islands use their own water resources for public water supply, or plan to do it in the future. Since karst rocks are extremely permeable, the seawater intrudes into underground water resources, thereby forming the wedge. A wide transition zone occurs between this seawater wedge and fresh water aquifers. Consequently, island groundwater reserves turn brackish to a certain extent. In this study, 77 water samples were collected from a wide variety of water resources. Comprehensive statistical and mathematical multivariate analysis of these data was performed. Simple statistical approach showed several useful correlations among some parameters, and more complex multivariate techniques extracted three factors in connection with three natural processes: (1) mixing with the seawater, (2) carbonate dissolution and (3) human influence (pollution) and nitrogen transformation processes. The results of this study demonstrate that in situ measurement of electrical conductivity is adequate for the very rough field estimation of numerous parameters.