Partitioning Of Zinc Research Articles

Zinc partitioning between mantle minerals and basaltic melts: Application to revisit the Zn/FeT redox proxy

Zn/FeT (FeT=Fe2+ + Fe3+) ratios in primitive melts have been proposed as a redox proxy to assess the redox states of the upper mantle. However, to effectively use the melt Zn/FeT ratio as a redox proxy, it is necessary to compare variations of melt Zn/FeT ratios induced by changes in oxygen fugacity (fO2) with variations due to changes in Zn-Fe contents and mineralogy of the sources. Here we show that the melt Zn/FeT ratio variation caused by fO2 change can be expressed as Δ(Znm/FemT) = (Znper/FeperT)* Δ(Fem2+/FemT)/(DZnper/m/DFe2+per/m). Zn/FeT ratios in most arc and MORB peridotites (Znper/FeperT) are 9.0 ± 1.0*10−4, and melt Fe2+/FeT ratio variation resulted from fO2 change [Δ(Fem2+/FemT)] can be easily obtained by the existing model. Hence, if the Zn and Fe2+ partition coefficients (DZnper/m and DFe2+per/m) between melt and peridotite are known, the melt Zn/FeT ratio variation resulting from fO2 change can be estimated. In this study, we determined DZn between olivine, orthopyroxene, clinopyroxene and basaltic melts at 0.75–2.5 GPa and 1250–1450 ℃. Our data show that melt composition (expressed as MgO content) dominantly controls the mineral-melt Zn partitioning under peridotite melting conditions. These data, along with published mineral-melt DFe2+ data, enable us to calculate appropriate DZnper/m/DFe2+per/m, which is 0.78 ± 0.02 under arc and MORB spinel peridotite melting conditions. Based on these parameters, the calculated average melt Zn/FeT ratio variation caused by per log unity fO2 change in typical fO2 span of arc and MORB mantles is only ∼ 0.69 ± 0.20*10−4. Alternatively, melt Zn/FeT ratio variations caused by changes in Zn-Fe contents and mineralogy of peridotites are ±1.10*10−4. These findings indicate that melt Zn/FeT ratio variation induced by one log units fO2 change is on the same order of magnitude as those caused by changes in Zn-Fe contents and mineralogy of peridotites. Therefore, unless the precise chemical and mineralogical compositions of the mantle sources can be determined independently, the melt Zn/FeT redox proxy is unsuitable for tracing the mantle fO2. Our study, combined with recent works on melt Cu and V/Sc redox proxies, suggests that these redox proxies, previously considered as the strongest evidence for a reduced arc mantle, might not support the idea of a reduced arc mantle.

Significant effect of salinity on zinc adsorption on tropical coastal and floodplain soils

AbstractRising sea levels due to climate change are causing increased salinisation of low‐lying coastal and floodplain soils, and the impact of this process on the bioavailability of plant nutrients needs to be understood as mitigation strategies are adapted. Zinc (Zn) is an element of particular importance due to its function as a micronutrient for plants including rice and other staple foods. In the current study, our aim was to investigate the effects of salinisation on zinc adsorption onto soils representing at‐risk coastal and floodplain environments, addressing in particular our knowledge gap concerning the roles that solution chemistry and soil composition play. To this end, we conducted batch adsorption experiments in the laboratory and ran geochemical models in saline solutions up to 0.7 mol L−1 ion strength incorporating both (i) a multi surface model (MSM) for surface reactions containing three phases, that is iron hydroxides, organic matter and phyllosilicate clays, and (ii) aqueous‐phase complexation to dissolved organic and inorganic ligands. Surface reactions were modelled using the diffuse double layer model, the NICA–Donnan model and an ion exchange model using the Gaines–Thomas convention. We combined the experimentally determined mass composition of surface phases with generic modelling parameters taken from the literature. We first show that increasing salinity enhances the formation of aqueous Zn‐chloride complexes in the presence of dissolved organic matter and bicarbonate, thereby decreasing the availability of free Zn2+ and supressing the partitioning of zinc to the adsorbed phase. We demonstrate using batch adsorption experiments with a calcareous hydraquent and a tropaquept, that salinity decreases zinc adsorption strongly in the pH range between 3 and 6. Satisfactory agreement between experiments and model calculations was achieved with root‐mean‐square errors ranging for different salinities between 2.88% and 2.92% for the hydraquent and between 4.59% and 2.74% for the tropaquept soil. Model predictions of adsorption were slightly inferior at low salinity for the hydraquent soil and at high salinity for the tropaquept soil, pointing possibly to an incomplete geochemical model or to a need to parametrise surface adsorption models at higher ionic strengths. Present surface models have been largely parametrised at lower ionic strength. We lastly apply the MSM to examine zinc adsorption in five endoaquepts soils, representing soil series from Bangladesh. We show that increasing salinity decreases zinc adsorption to the soil organic matter and the clay fractions. We conclude from our findings that increased soil salinity due to rising sea levels and climate change will have a significant impact on zinc cycling and possibly other micronutrients in areas where coastal soils and floodplain soils overlap, such as deltas and estuaries. In particular, we predict a decrease in zinc adsorption in acidic to neutral soils. The availability of zinc for biouptake through the roots of crop plants including rice will be significantly disturbed following salinisation, most likely affecting crop production. Our study demonstrates the potential that geochemical modelling combined with experimental data has to improve our capability to assess the effects of salinity due to rising seawater levels in vulnerable regions of the world.

Agronomic biofortification of finger millet for zinc, and its influence on yield and partitioning of zinc, iron, and calcium in the plant

Zinc (Zn) deficiency in humans is the most common, and zinc requirement is catered mainly by cereal food grains which have lower zinc content. Finger millet is one of the staple food crops in Africa and India and has only 25 to 30 µg Zn g−1 of grain. Breeding efforts have improved the grain-Zn content to nearly 40 µg g−1 of grain, which is far below the recommended dietary allowance of 15 mg day−1 adult−1, and such varieties are not suited to all the finger millet cultivation regions. Therefore, the objective of the present studies is to enhance the grain-Zn content of locally adapted varieties through agronomic biofortification, which can be adapted for any variety and region. The easy, promising, and cost-effective approach is the soil or foliar application of zinc to increase the grain-Zn content. Present studies over four years revealed that the foliar application of 0.5% ZnSO4·7H2O solution at flowering and 20 days after flowering (DAF) is apt to increase the grain-Zn significantly to 40 µg g−1 of grain. Whereas the soil application of ZnSO4·7H2O at 12.5 kg ha−1 is appropriate to increase the grain yield to 504 g m−2 from 444 g m−2 in the control. The partitioning of zinc and calcium was higher toward the leaf sheath, leaf lamina, and husk than the other plant parts, whereas iron was toward the root. Therefore, the translocation of zinc from leaves to grain needs to be improved for further increase in grain-zinc of finger millet.

Uptake and preferential partitioning of zinc in different wheat species

AbstractSome wild relatives have higher grain zinc (Zn) concentrations than common wheat and were widely used for wheat biofortification. However, little is known about the mechanisms controlling Zn accumulation in wheat and its wild relatives. This study is aimed to shed light on the causes of different grain Zn concentrations in wheat at a physiological level. Six genotypes, including one Triticale, one Triticum monococcum, one Triticum petropavlovskyi, and three Triticum aestivum, with different grain Zn concentrations, were evaluated in this study. Zn concentrations in roots and aboveground tissues in the field at grain maturity were measured to assess the differences in Zn uptake and partitioning among genotypes. Zn concentrations in roots and shoots at the seedling stage in hydroponics were also assessed to see if the differences in Zn uptake efficiencies could be identified before planting in the laboratory. The triticale had the highest grain Zn concentration, followed by the cultivated einkorn wheat, the T. petropavlovskyi wheat, and then the three common wheat varieties. No difference in Zn concentration was detected between grains from the main stem and grains from tillers. Genotypes with high grain Zn concentration generally had higher Zn uptake and rachis Zn loading efficiencies. The cultivated einkorn wheat showed retarded translocation of Zn in nodes. Genotypes with high Zn uptake efficiencies may be identified at the seedling stage in hydroponics. Grain Zn concentration is a product of multiple physiological processes. Roots, nodes, and rachis could be the potential target tissues for further research related to grain Zn accumulation.

Integrated use of plant growth-promoting bacteria and nano-zinc foliar spray is a sustainable approach for wheat biofortification, yield, and zinc use efficiency.

The intensive cropping system and imbalance use of chemical fertilizers to pursue high grain production and feed the fast-growing global population has disturbed agricultural sustainability and nutritional security. Understanding micronutrient fertilizer management especially zinc (Zn) through foliar application is a crucial agronomic approach that could improve agronomic biofortification of staple grain crops. The use of plant growth-promoting bacteria (PGPBs) is considered as one of the sustainable and safe strategies that could improve nutrient acquisition and uptake in edible tissues of wheat to combat Zn malnutrition and hidden hunger in humans. Therefore, the objective of this study was to evaluate the best-performing PGPB inoculants in combination with nano-Zn foliar application on the growth, grain yield, and concentration of Zn in shoots and grains, Zn use efficiencies, and estimated Zn intake under wheat cultivation in the tropical savannah of Brazil. The treatments consisted of four PGPB inoculations (without inoculation, Azospirillum brasilense, Bacillus subtilis, and Pseudomonas fluorescens, applied by seeds) and five Zn doses (0, 0.75, 1.5, 3, and 6 kg ha-1, applied from nano ZnO in two splits by leaf). Inoculation of B. subtilis and P. fluorescens in combination with 1.5 kg ha-1 foliar nano-Zn fertilization increased the concentration of Zn, nitrogen, and phosphorus in the shoot and grain of wheat in the 2019 and 2020 cropping seasons. Shoot dry matter was increased by 5.3% and 5.4% with the inoculation of P. fluorescens, which was statistically not different from the treatments with inoculation of B. subtilis as compared to control. The grain yield of wheat was increased with increasing nano-Zn foliar application up to 5 kg Zn ha-1 with the inoculation of A. brasilense in 2019, and foliar nano-Zn up to a dose of 1.5 kg ha-1 along with the inoculation of P. fluorescens in the 2020 cropping season. The zinc partitioning index was increased with increasing nano Zn application up to 3 kg ha-1 along with the inoculation of P. fluorescens. Zinc use efficiency and applied Zn recovery were improved at low doses of nano-Zn application in combination with the inoculation of A. brasilense, B. subtilis, and P. fluorescens, respectively, as compared to control. Therefore, inoculation with B. subtilis and P. fluorescens along with foliar nano-Zn application is considered a sustainable and environmentally safe strategy to increase nutrition, growth, productivity, and Zn biofortification of wheat in tropical savannah.

Macro and Micro-Nutrient Accumulation and Partitioning in Soybean Affected by Water and Nitrogen Supply.

This study aimed to investigate the influence of water availability and nitrogen fertilization on plant growth, nutrient dynamics, and variables related to soybean crop yield. Trials were performed in Teresina, Piauí, Brazil, using randomized blocks in a split-split plot arrangement. The plots corresponded to water regimes (full and deficient), the split plots to N fertilization (0 and 1000 kg ha-1 N-urea), and the split-split plots to harvest times of soybean plants (16, 23, 30, 37, 44, 58, 65, 79 and 86 days after emergence), with three replicates. In general, the accumulation and partitioning of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulphur (S), copper (Cu), iron (Fe), manganese (Mn), zinc (Zn) and boron (B) were decreased in plants subjected to water deficit and without N fertilization. Although nitrogen fertilization promoted elevated N accumulation in tissues, it did not result in any significant yield gain, and the highest seed yields were found in plants under full irrigation, regardless of N supplementation. However, deficient irrigation decreased the seed oil content of N-fertilized plants. In conclusion, N fertilization is critical for nutrient homeostasis, and water availability impairs biomass and nutrient accumulation, thereby limiting soybean yield performance.

Characterizing Trace Metal Contamination and Partitioning in the Rivers and Sediments of Western Europe Watersheds

Adsorption and desorption processes occurring on suspended and bed sediments were studied in two datasets from western Europe watersheds (Meuse and Mosel). Copper and zinc dissolved and total concentrations, total suspended sediment concentrations, mass concentrations, and grain sizes were analyzed. Four classes of mineral particle size were determined. Grain size distribution had to be considered in order to assess the trace metal particulate phase in the water column. The partitioning coefficients of trace metals between the dissolved and particulate phases were calculated. The objective of this study was to improve the description of the processes involved in the transportation and fate of trace metals in river aquatic ecosystems. Useful data for future modelling, management and contamination assessment of river sediments were provided. As it is confirmed by a literature review, the copper and zinc partitioning coefficients calculated in this study are reliable. The knowledge related to copper and zinc (e.g., partitioning coefficients) will allow us to begin investigations into environmental modelling. This modelling will allow us to consider new sorption processes and better describe trace metal and sediment fates as well as pressure–impact relationships.

Subcellular Accumulation and Depuration of Zinc in Periphytic Algae during Episodic and Continuous Exposures

As the severity of extreme precipitation events increases with global climate change, so will episodic pulses of contamination into lotic systems. Periphytic algae represents bioindicator species in most freshwater systems due to their rapid accumulation of toxicants; therefore, it is vital to understand how accumulation in this group differs across temporally variable exposure regimes. The ability to rapidly accrue contaminants has additional implications for the trophic transfer of metals to primary consumers. While dietary toxicity has been studied in algivorous consumers, techniques used to prepare contaminated periphytic algae for consumption have not been compared. This study used a modified subcellular fractionation method to compare the partitioning of zinc (Zn) in periphyton cultures exposed for various durations (cultured in the presence of Zn and 15 min, 24 h, and 48 h exposures). Three exposure groups were additionally depurated over a period of 24 h in order to compare retention of Zn, an important aspect of preparing diets used in dietary toxicity studies. The results not only provide evidence for increased retention by periphytic algae cultured in the presence of Zn but reveal relationships among treatments and subcellular partitioning that suggest time-dependent accumulation and detoxification. These relationships suggest that episodic exposure of periphytic algae to contaminants may pose a greater risk than that of chronic regimes. Based on these results, we additionally advocate for culturing periphytic algae in the presence of contamination to produce a more reliable diet for dietary exposure testing in algivorous organisms.

Carbon dioxide enrichment effects on concentration, partitioning and uptake of metallic micronutrient elements in soybean under varied nitrogen application rates

Information on the fate of micronutrients in plant tissue and total uptake from soil upon exposure to elevated carbon dioxide (CO2) is meager. Hence, this field study was conducted in open top field chambers to investigate the effects of elevated CO2 and applied nitrogen (N) on partitioning and uptake of zinc (Zn), copper (Cu), iron (Fe), and manganese (Mn) in soybean crop under two CO2 and four N levels during 2016 and 2018 crop seasons. The two CO2 concentrations were ambient and elevated (∼550 µmol mol−1). Nitrogen treatments included application at 0, 50, 100, and 150% of the recommended dose. Significant effects of CO2 and N were observed on grain yield, biomass and uptake of the four micronutrients. Seed Fe concentration was significantly increased by 12% under CO2 enrichment. Tukey’s post-hoc test revealed significantly higher grain yield, biomass and uptake of micronutrients in seed and straw under CO2 elevation and at higher N application. Uptake of Fe, Zn, Cu, and Mn increased by 53, 42, 36, and 41%, respectively, in seed and by 25, 26, 31, and 18% in straw under elevated CO2. Total uptake of Fe, Zn, Cu, and Mn increased by 39, 38, 34, and 29%, respectively. Nitrogen at 100% level enhanced uptake of Fe, Zn, Cu, and Mn by 25, 20, 32, and 28%. The study bears implications in micronutrient management for sustaining soil health under changing climate.

Effects of Zinc Fertilization on Grain Cadmium Accumulation, Gene Expression, and Essential Mineral Partitioning in Rice

Cadmium (Cd) is a toxic heavy metal that can cause severe health issues if ingested. Certain varieties of rice can accumulate high levels of the metal in edible tissues thereby transferring the toxin into the food chain. As chemical analogs, interactions between the essential mineral zinc and the toxic heavy metal cadmium play an important role in regulating the transport of both minerals to rice grains. Understanding these interactions is crucial for limiting cadmium and increasing zinc transfer to the food chain. Previous studies have reported conflicting results suggesting synergistic and antagonistic relationships between the minerals. The goal of this work was to identify the effect of external cadmium and zinc on the uptake and translocation of both minerals from roots to grains of rice that differ in grain cadmium concentrations. The results showed that a higher input of external zinc increased cadmium translocation and accumulation to the grain in two of three varieties, while external cadmium does not influence zinc accumulation. Cadmium synergy and antagonism with other essential minerals were also examined and the effects differed between rice lines. Our results showed that the differential expression of the transport proteins OsNramp5, OsHMA2, and OsHMA3 as well as genes involved in the synthesis of glutathione and phytochelatin could have contributed to differences in grain Cd accumulation. These results add to the knowledge of cadmium and zinc partitioning in one of the most consumed plant foods in the world and can assist fortification efforts to establish rice lines that are both safe and nutritious.

Metal pollutant pathways in cohesive coastal catchments: Influence of flocculation and biopolymers on partitioning and flux

The impacts of the partitioning of potentially toxic metals (PTM) within the estuarine environment is highly complex, but is of key significance owing to increases in populations living within such sensitive environments. Although empirical data exist for the partitioning of metals between the dissolved and particulate phases, little is known regarding the impacts of extracellular polymeric substances (EPS) upon the flocculation of particles within such a dynamic system nor the resultant influence on the distribution of metals between the particulate and dissolved phases. This prevents regulators from fully understanding the fate and risks associated with metals in estuaries. This study provides data associated with the simulation of 3 settlings typical of the turbulent mixing found in estuaries and partitioning of copper, cadmium, nickel, arsenic, lead and zinc for 3 salinities (0, 15, 30 PSU) reflecting the full salinity range from freshwater to seawater. Experiments were completed with and without the presence of EPS, using kaolin as the mineral particulate. The results showed significant differences between salinity, PTMs and turbulence for the experiments with and without EPS present. Overall, salinity was the main factor controlling the PTM partitioning to sediment, however the flocculation process did impact on the PTM distribution and with the addition of EPS the impact was more pronounced. The data highlighted the importance of taking account of EPS within any estuarine sediment process modelling, for relying on simple partitioning with corrections for salinity would likely lead to significant bias.

Partition, correlation, and natural bioconcentration of iron, manganese, and zinc in cacao trees

The aim of this study was to evaluate the variability, partition, and correlation of Fe, Mn, and Zn in the leaves and fruit components (pod husk, pulp, tegument, and cotyledons) of cacao trees. These contents were also correlated with chemical attributes of the soils in regions classified as humid (H), humid to sub-humid (SH), and sub-humid to dry (SD) in the South Bahia, Brazil. Soils samples were collected, along with leaves and fruits from the PH16 clone of the cacao tree, for analysis of Fe, Mn, and Zn. Descriptive statistics and Pearson's correlation were applied, as well as Shapiro Wilk’s normality test and Tukey's test for comparison of the climate regions. The accumulation order for Fe and Zn in the fruit components was tegument > pod husk > leaf > cotyledons; and for Mn the order was pod husk > leaf > tegument > cotyledons. The increase in hydric restriction, from the most humid region to the driest, causes natural bioconcentration of Fe, Mn, and Zn in the fruit components used to produce food (cotyledons and pulp). The Mn contents in the leaf can be used as indicators of its accumulation in the cotyledon and cacao pulp.

Partitioning of zinc and its associated metabolites in zinc efficient and inefficient rice (Oryza sativa L.) genotypes

Among rice genotypes, substantial differences exist with respect to zinc efficiency, but the mechanisms underlying zinc efficiency are less envisaged. Hence, focus of present investigation was to identify the pattern of zinc partitioning in different plant parts of rice genotypes viz., PR113, PR121, RYT Biofort1 and RYT 3403 at three stages viz., maximum tillering, anthesis and maturity. The rice genotypes were selected on the basis of their inherent zinc content. The experiment was conducted during the Kharif 2016–17. The studies suggest that PR113 and PR121 genotypes accumulated higher dry matter, zinc and metabolites and were rated as zinc efficient in comparison to RYT Biofort1 and RYT 3403 genotypes which were rated as zinc inefficient. Remobilization of zinc from source to sink was more prominent in zinc efficient genotypes, whereas zinc inefficient favored its retention in the source tissues.

Solid-phase partitioning and release-retention mechanisms of copper, lead, zinc and arsenic in soils impacted by artisanal and small-scale gold mining (ASGM) activities

Artisanal and small-scale gold mining (ASGM) operations are major contributors to the Philippines’ annual gold (Au) output (at least 60%). Unfortunately, these ASGM activities lacked adequate tailings management strategies, so contamination of the environment is prevalent. In this study, soil contamination with copper (Cu), lead (Pb), zinc (Zn) and arsenic (As) due to ASGM activities in Nabunturan, Davao de Oro, Philippines was investigated. The results showed that ASGM-impacted soils had Cu, Pb, Zn and As up to 3.6, 83, 73 and 68 times higher than background levels, respectively and were classified as ‘extremely’ polluted (CD = 30–228; PLI = 5.5–34.8). Minerals typically found in porphyry copper-gold ores like pyrite, chalcopyrite, malachite, galena, sphalerite and goethite were identified by XRD and SEM-EDS analyses. Furthermore, sequential extraction results indicate substantial Cu (up to 90%), Pb (up to 50%), Zn (up to 65%) and As (up to 48%) partitioned with strongly adsorbed, weak acid soluble, reducible and oxidisable fractions, which are considered as ‘geochemically mobile’ phases in the environment. Although very high Pb and Zn were found in ASGM-impacted soils, they were relatively immobile under oxidising conditions around pH 8.5 because of their retention via adsorption to hydrous ferric oxides (HFOs), montmorillonite and kaolinite. In contrast, Cu and As release from the historic ASGM site samples exceeded the environmental limits for Class A and Class C effluents, which could be attributed to the removal of calcite and dolomite by weathering. The enhanced desorption of As at around pH 8.5 also likely contributed to its release from these soils.

Partitioning of zinc, copper and lead in urban drainage from paved source area catchments

Representation of metal partitioning in urban drainage is required when determining loadings, treatment, maintenance and regulatory compliance. This study examined partitioning and transport of metals from urban paved surfaces: highway; parking lot (landside) and apron terminal (airside) within aviation site; terminals within port area. Equilibrium concentrations of metals and particulate matter (PM) using a non-parametric analysis for a series of six paved surface area catchments were compared. In particular, two American highway sites and four Italian sites located in the Liguria Region (two port terminal and two aviation sites) are examined and compared with event-based concentrations collected from catchments with similar land uses. The highway sites are more heavily loaded with PM (up to averagely 470 mg/l of PM as total suspended solids) while the terminal port ones reveal the most significant mass delivery of metals, as high as 1 mg/l. Transport of metal phases on an event basis, thus relating hydrology and PM mass delivery impacting metal partitioning, are examined. At all catchment sites, copper and lead reveal the greatest affinity for the particulate-bound fraction while zinc shows significantly different partitioning behaviour that may be partially depending on the specific site characteristics and the chemistry of zinc. Partitioning, indexed through a partitioning coefficient, Kd, accounts for hydrologic transport, PM transport and interactions with and between metals. Kd can vary by orders of magnitude across a runoff event for the source area catchments of this study. A Kd condition in the range of 104–105 l/kg appears to be approached for all metals as elapsed runoff time increases. Based on the variability of partitioning, whether intra- or inter-event, results indicate that paved source area treatment requires a combination of sedimentation, filtration and adsorption mechanisms for in-situ unit operations and processes.

Effect of Zinc Fertilizer Application on Growth Yield and Yield Contributing Characters in Rice

Field experiment was carried out at the field of Department of Agronomy, BSMRAU campus, Gazipur, of Bangladesh during aman season (July-October) of 2017 to study the effect of zinc fertilizer application on growth, yield and zinc partitioning in three rice varieties: (BRRI dhan 56, BRRI dhan 57 and BRRI dhan 62) at three levels of zinc fertilization, no application of zinc, 10and 20 kg Zn ha-1. The highest leaf area indices of 3.15 in BRRI dhan 56, and 3.27 in BRRI dhan 57 were recorded with the application of 10 kg Zn ha-1 at 75 DAT and 3.28 in BRRI dhan 62 with 20 kg Zn ha-1. Through the growth period the SPAD value was the maximum at 10 kg Zn ha-1 in BRRI dhan 56 and BRRI dhan 57 and in BRRI dhan 62 at 20 kg Zn ha-1. The highest CGR, RGR, NAR were recorded at 10 kg Zn ha-1 in BRRI dhan 56 and BRRI dhan 57, and at 20 kg ha-1 in BRRI dhan 62.Zinc fertilizer at 10 kg Zn ha-1significantly increased the number of effective tiller m-2, length of panicle, total number of spikelet’s panicle-1,1000-grain weight, number of filled spikelet’s panicle-1, grain yield and straw yield in BRRI dhan 56 and BRRI dhan 57, and at 20 kg Zn ha-1 in BRRI dhan 62. It was revealed that the rice varieties BRRI dhan 56 and BRRI dhan 57 responded to the application of 10 kg Zn ha-1, while BRRI dhan 62 to 20 kg Zn ha-1.Overall results indicates, application of zinc might be necessary to ensure satisfactory yield.

Partitioning and geochemical fractions of heavy metals from geogenic and anthropogenic sources in various soil particle size fractions

The size of soil particles can significantly affect the enrichment of heavy metals in soil. However, the size effect of soil particles in colloidal dimension on the partitioning and geochemical fractions of heavy metals has been rarely studied. In this study, four soils, polluted by several heavy metals, were collected from Jiangxi (JX) and Hebei (HB) Provinces and Guangxi Zhuang Autonomous Region (GX and GX′) in China, respectively. Five size fractions (>10, 10–1, 1–0.45, 0.45–0.2 and <0.2μm) were separated from the studied soils to investigate the partitioning and geochemical fractions of cadmium (Cd), cadmium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn). For JX, GX and GX′ soils, Cr and Ni in JX and GX′ soils and Cr, Ni and Mn in GX soil, as geogenic elements, were comparable with their background values; whereas other heavy metals, as anthropogenic elements, were higher than their background values. For the HB soil that was only polluted by Pb, Cd, Cr, Cu, Mn, Ni and Zn were the geogenic heavy metals. Generally, the contents of most heavy metals in the soil colloids were higher than that in coarse soil particles, and the partitioning tendencies with particle size were not significantly different between geogenic heavy metals and anthropogenic heavy metals. The partitioning of heavy metals in various soil particle size fractions was closely related to the soil particle compositions, such as OM, Fe/Al oxides and clay minerals. For geogenic heavy metals (Cr, Ni), the proportion of the residual fraction, which is imbedded in the silicate crystalline structures of soil particles, was very high, and the geochemical fraction patterns of the various soil particle size fractions were comparable, whereas the bioavailable fraction of anthropogenic heavy metals, such as Cu, Mn, Pb and Zn, decreased with decreasing soil particle size and the proportion of other fractions increased with decreasing size. This result indicates that more anthropogenic heavy metals exist in their stable form in fine soil particles. Correlations between Fe, Al and TOC and the bioavailable fraction of anthropogenic heavy metals were all negative, and most were significant or very significant indicating that high contents of OM and Fe/Al oxides stabilize anthropogenic heavy metals in fine soil particles.

Zinc partitioning in basmati rice varieties as influenced by Zn fertilization

Zinc (Zn) ferti-fortification using different sources and methods in Zn deficient soils is being advocated to increase Zn concentration in rice kernel as an alternative to pursuing greater Zn-use efficiency (ZnUE). A two-year field study was conducted to assess the effect of Zn application on Zn content and uptake at several growth stages and in several parts of the rice kernel: hull, bran, and the white rice kernel. Variety ‘PB 1509’ with 1.25kgZnha−1 as Zn-EDTA+0.5% foliar spray (FS) at maximum tillering (MT) and panicle initiation (PI) stages registered the highest Zn content in hull, bran, and white rice kernel. Among parts of the rice kernel, Zn concentration decreased in the order hull>bran>white rice kernel, indicating that brown rice kernels are much denser in Zn content than polished rice. Considering the higher Zn accumulation in the bran, brown rice consumption, especially in Asia and Africa, could be recommended to overcome Zn malnutrition. The variety ‘PB 1401’ showed the highest Zn uptake in rice straw, while ‘PB 1509’ showed the highest Zn uptake in hull and white rice kernel. Application of 1.25kgZnha−1 (Zn-EDTA)+0.5% FS at MT and PI and 2.5kgZnha−1 ZnSO4·7H2O (ZnSHH)+0.5% FS at MT and PI resulted in higher Zn uptake than other treatments. On average, about one third of total Zn uptake remained in the white rice kernel, with the remaining two thirds accumulating in both hull and bran of brown rice. Zn-EDTA along with 0.5% FS, despite the application of a lower quantity of Zn leading to the highest Zn mobilization efficiency index (ZnMEI) and Zn-induced nitrogen recovery efficiency (ZniNRE), produced the highest kernel yield. However, of the two Zn sources, Zn-EDTA contributed more to the increase in ZnUE than did ZnSHH.

Subcellular partitioning of cadmium and zinc in mealworm beetle (Tenebrio molitor) larvae exposed to metal-contaminated flour

By studying the internal compartmentalization of metals in different subcellular fractions we are able to better understand the mechanisms of metal accumulation in organisms and the transfer of metals through trophic chains. We investigated the internal compartmentalization of cadmium (Cd) and zinc (Zn) in mealworm beetle (Tenebrio molitor) larvae by breeding them in flour contaminated with either Cd at 100, 300 and 600mgkg−1, or Zn at 1000 and 2000mgkg−1. We separated the cellular components of the larvae into 3 fractions: the S1 or cytosolic fraction containing organelles, heat-sensitive and heat-stable proteins, the S2 or cellular debris fraction and the G or metal-rich granule fraction. The concentration of Cd and Zn in each fraction was measured at 0, 7, 14 and 21 days of being fed the flour.The concentration of Cd in the flour affected the concentration of Cd measured in each larval subcellular fraction (p≤0.0001), while the concentration of Zn in the flour only affected the Zn concentration in the S2 and G fractions (p≤0.02). Both Cd and Zn concentrations in mealworms remained relatively constant during the exposure (days 7, 14 and 21) in all three fractions, but the Cd concentrations were much higher than those found in larvae before the exposure (day 0). The concentration of Cd in the flour, however, did not affect the percentage of Cd in the S1 fraction. The contribution of Cd in the G fraction to the total Cd amount was similar (30–40%) in all Cd treatments. The percentage of Zn in all three fractions was not affected by the concentration of Zn in the flour and the relative contributions of each subcellular fraction to the total burden of Zn remained generally constant for both control and treated larvae. In general, larvae sequestered approximately 30% of Cd and Zn in the S1 fraction, which is important for the transport of metals to higher trophic levels in a food web.

Zinc incorporation in the miliolid foraminifer Pseudotriloculina rotunda under laboratory conditions

The incorporation rate of Zn into the calcareous tests of Pseudotriloculina rotunda was investigated in culture in order to evaluate the possibility of using Zn/Ca ratios as a pollution proxy. Foraminifera were incubated at zinc concentrations up to 10-fold higher than unpolluted seawater (sea + 10 mg Zn/L) during 70 days. New calcite was investigated under the Environmental Scanning Electron Microscope (ESEM), for potential alteration of test structure. Laser ablation-Inductively Coupled Plasma-Mass spectrometry (LA-ICP-MS) was used to quantify Zn contents. The analyses revealed that test structure is not visibly altered by the presence of zinc. However, significant Zn incorporation is detected by the LA-ICP-MS. The zinc partition coefficient, DZn, decreases at increasing Zn concentrations (from 4.03 ± 0.06 to 0.2 ± 0.01) and the zinc is incorporated into the calcite not necessarily linearly.