Biogeochemistry Of Trace Elements In Arid Environments

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Effect of Bioaccumulation of Cs and Sr Natural Isotopes on Foliar Structure and Plant Spectral Reflectance of Indian Mustard (Brassica juncea) -8105

ABSTRACT The objectives of this study are: 1.) evaluate the capacity of Indian mustard (Brassica juncea) for uptake and accumulation of Cs and Sr natural isotopes; 2.) identify foliar structural and other physiological changes (biomass, relative water content, etc.) resulting from the accumulation of these two elements; and 3.) monitor Cs and Sr uptake and bioaccumulation process by spectral reflectance. Potted Indian mustard plants were exposed to different concentrations of Cs (50 and 600 ppm) and Sr (50 and 300 ppm) natural isotopes in solution form for 23 days. Bioaccumulation of Cs and Sr was found in the order of leaves > stems > roots for both Cs-and Sr-treated plants. The highest leaf Sr accumulation is observed to be 2708 mg kg -1 , and the highest leaf Cs accumulation is 12251 mg kg -1 . High translocation efficiency for both elements is documented by shoot/root concentration ratios greater than one. Relative water content (RWC) of the plants showed a significant (p < 0.05) decrease in Cs-treated plants. Cs accumulation also affected the pigment concentration and internal structure of the leaf and the spectral characteristics of plants. Within the applied concentration range, Sr accumulation resulted in no significant changes in RWC, structural and spectral characteristics of mustard plants. Cs shoot concentration showed significant negative correlation with relative water content RWC (r = -0.88) and Normalized Difference Vegetation Index (NDVI) (r = -0.68) of plant shoots. The canopy spectral reflectance and NDVI analysis clearly revealed (p < 0.05) the stress caused by Cs accumulation

Removing uranium (VI) from aqueous solution with insoluble humic acid derived from leonardite

The occurrence of uranium (U) and depleted uranium (DU)-contaminated wastes from anthropogenic activities is an important environmental problem. Insoluble humic acid derived from leonardite (L-HA) was investigated as a potential adsorbent for immobilizing U in the environment. The effect of initial pH, contact time, U concentration, and temperature on U(VI) adsorption onto L-HA was assessed. The U(VI) adsorption was pH-dependent and achieved equilibrium in 2 h. It could be well described with pseudo second-order model, indicating that U(VI) adsorption onto L-HA involved chemisorption. The U(VI) adsorption mass increased with increasing temperature with maximum adsorption capacities of 91, 112 and 120 mg g(-1) at 298, 308 and 318 K, respectively. The adsorption reaction was spontaneous and endothermic. We explored the processes of U(VI) desorption from the L-HA-U complex through batch desorption experiments in 1 mM NaNO3 and in artificial seawater. The desorption process could be well described by pseudo-first-order model and reached equilibrium in 3 h. L-HA possessed a high propensity to adsorb U(VI). Once adsorbed, the release of U(VI) from L-HA-U complex was minimal in both 1 mM NaNO3 and artificial seawater (0.06% and 0.40%, respectively). Being abundant, inexpensive, and safe, L-HA has good potential for use as a U adsorbent from aqueous solution or immobilizing U in soils. (C) 2017 Elsevier Ltd. All rights reserved

In site bioimaging of hydrogen sulfide uncovers its pivotal role in regulating nitric oxide-induced lateral root formation

Hydrogen sulfide (H2S) is an important gasotransmitter in mammals. Despite physiological changes induced by exogenous H2S donor NaHS to plants, whether and how H2S works as a true cellular signal in plants need to be examined. A self-developed specific fluorescent probe (WSP-1) was applied to track endogenous H2S in tomato (Solanum lycopersicum) roots in site. Bioimaging combined with pharmacological and biochemical approaches were used to investigate the cross-talk among H2S, nitric oxide (NO), and Ca(2+) in regulating lateral root formation. Endogenous H2S accumulation was clearly associated with primordium initiation and lateral root emergence. NO donor SNP stimulated the generation of endogenous H2S and the expression of the gene coding for the enzyme responsible for endogenous H2S synthesis. Scavenging H2S or inhibiting H2S synthesis partially blocked SNP-induced lateral root formation and the expression of lateral root-related genes. The stimulatory effect of SNP on Ca(2+) accumulation and CaM1 (calmodulin 1) expression could be abolished by inhibiting H2S synthesis. Ca(2+) chelator or Ca(2+) channel blocker attenuated NaHS-induced lateral root formation. Our study confirmed the role of H2S as a cellular signal in plants being a mediator between NO and Ca(2+) in regulating lateral root formation

Kinetics and Thermodynamics of Uranium (VI) Adsorption onto Humic Acid Derived from Leonardite

Humic acid (HA) is well known as an inexpensive and effective adsorbent for heavy metal ions. However, the thermodynamics of uranium (U) adsorption onto HA is not fully understood. This study aimed to understand the kinetics and isotherms of U(VI) adsorption onto HA under different temperatures from acidic water. A leonardite-derived HA was characterized for its ash content, elemental compositions, and acidic functional groups, and used for the removal of U (VI) from acidic aqueous solutions via batch experiments at initial concentrations of 0−100 mg·L−1 at 298, 308 and 318 K. ICP-MS was used to determine the U(VI) concentrations in solutions before and after reacting with the HA. The rate and capacity of HA adsorbing U(VI) increased with the temperature. Adsorption kinetic data was best fitted to the pseudo second-order model. This, together with FTIR spectra, indicated a chemisorption of U(VI) by HA. Equilibrium adsorption data was best fitted to the Langmuir and Temkin models. Thermodynamic parameters such as equilibrium constant (K0), standard Gibbs free energy (ΔG0), standard enthalpy change (ΔH0), and standard entropy change (ΔS0), indicated that U(VI) adsorption onto HA was endothermic and spontaneous. The co-existence of cations (Cu2+, Co2+, Cd2+ and Pb2+) and anions (HPO42− and SO42−) reduced U(VI) adsorption. The high propensity and capacity of leonardite-derived HA adsorbing U(VI) suggests that it has the potential for cost-effective removal of U(VI) from acidic contaminated waters

Endogenous H₂S was involved in lateral root formation in tomato seedlings.

<p>(a) WSP-1 was loaded into the roots during lateral root formation for fluorescent imaging. (b) The cross section of primary roots loaded with WSP-1. Arrows indicate lateral roots (LR) primordium; BF, bright field; Fl, fluorescence. (c–f) The roots of three-day old tomato seedlings were exposed to NaHS (2 mM), PAG (0.1 mM), HT (0.1 mM), Na₂SO₄ (2 mM), Na₂SO₃ (2 mM), and NaHSO₃ (2 mM) for 6 days for photographing root phenotype (c–d) and measuring lateral root numbers (e–f). Vertical bars represent the standard deviations of the mean (n = 6). (g–h) The roots of three-day old tomato seedlings were exposed to NaHS (2 mM), PAG (0.1 mM), HT (0.1 mM), Na₂SO₄ (2 mM), Na₂SO₃ (2 mM), and NaHSO₃ (2 mM) for 3 days. Then, the roots were loaded with WSP-1 for fluorescent imaging (g) and the calculation of relative fluorescent density (h). Vertical bars represent standard deviations of the mean (n = 3). Asterisk indicates that mean values are significantly different (<i>P</i><0.05) between the treatment and the control.</p

NO induced lateral root formation by regulating endogenous H₂S generation.

<p>(a–b) The roots of three-day old tomato seedlings were exposed to cPTIO (0.1 mM), SNP (0.2 mM), SNP (0.2 mM)+cPTIO (0.1 mM), GSNO (0.5 mM), and GSNO (0.5 mM)+cPTIO (0.1 mM) for 3 days. Then, the roots were loaded with WSP-1 for fluorescent imaging (a) and the calculation of relative fluorescent density (b). Vertical bars represent standard deviations of the mean (n = 3). (c) The roots of three-day old tomato seedlings were exposed to 0, 0.05, 0.1, 0.2, and 0.4 mM of SNP for 3 days. Then, the roots were loaded with DAF-FM DA and WSP-1 for fluorescent imaging, respectively. (d–g) The roots of three-day old tomato seedlings were exposed to cPTIO (0.1 mM), cPTIO (0.1 mM) + NaHS (2 mM), SNP (0.2 mM), and SNP (0.2 mM) + PAG (0.1 mM) for 6 days for photographing root phenotype (d–e) and measuring lateral root number (f–g). (h–i) The roots of three-day old tomato seedlings were exposed to cPTIO (0.1 mM), cPTIO (0.1 mM) + NaHS (2 mM), SNP (0.2 mM), and SNP (0.2 mM) + PAG (0.1 mM) for 2 days for the measurement of lateral root primordia. Vertical bars represent standard deviations of the mean (n = 6). (j) The roots of three-day old tomato seedlings were exposed to SNP (0.2 mM), NaHS (2 mM), and SNP (0.2 mM)+PAG (0.1 mM) for 2 days for the analysis of genes transcripts. (k) Quantitative analysis of genes transcript levels under different treatment conditions. The data were obtained by densitometric analysis of the relative abundance of the transcripts with respect to the loading control <i>Actin</i>. Asterisk indicates that mean values are significantly different (<i>P</i><0.05) between the treatment and the control. <i>Actin</i> was used for cDNA normalization.</p

The schematic model for H₂S regulation of lateral root formation.

<p>A positive feedback regulation of NO by H₂S probably exists in inducing lateral root formation.</p