Enrichment Of Zn Research Articles

Effects of trace Ca addition on microstructure and mechanical properties of as-cast Mg-Sm-Gd-based alloy

The effects of trace amounts of Ca on the microstructure and mechanical properties of as-cast Mg−Sm− Gd−Zn−Zr alloy were systematically investigated mainly by means of transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and tensile test. The results reveal that the dominant intermetallic compound in Mg−Sm−Gd−Zn−Zr alloy is Mg3RE phase with significant enrichment of Zn. The addition of Ca in Mg−Sm−Gd−Zn−Zr alloy can not only refine grains, but also promote the formation of Mg5RE phase and solute-enriched stacking faults (SESFs). The coherent interface indicates that Mg3RE phase can act as the nucleation site of Mg5RE phase. Finally, the decreased grain size and the formation of Mg5RE phase and SESFs in the Ca-modified alloy are beneficial to the enhancement of mechanical properties.

Root foraging in the leguminous zinc hyperaccumulator Crotalaria novae-hollandiae from Queensland, Australia

Context Root foraging by hyperaccumulator plants in response to patchily distributed metals has been observed in several obligate hyperaccumulators, but it is not known whether facultative hyperaccumulators respond similarly. Aims This study investigated the root-growth behaviour in the leguminous zinc (Zn) hyperaccumulator Crotalaria novae-hollandiae compared with the non-accumulating Crotalaria cunninghamii in response to localised soil Zn enrichment in the soil to observe foraging versus avoidance responses. Methods We conducted rhizotron experiments in which we exposed the Crotalaria species pair to juxtaposed treatments, which were either homogenous (each half of the treatments containing same Zn concentrations) or heterogenous (different Zn concentrations in each half of the treatments). The Zn concentrations were 0 μg Zn g−1 (control), 2000 μg Zn g−1 and 5000 μg Zn g−1 in the form of zinc carbonate). Key results We found that none of the treatments had significantly different rooting density and root biomass, regardless of the Crotalaria species. This finding contrasts with increased root proliferation in Zn-rich patches found for other obligate hyperaccumulator species. Conclusions and implications The no-preference root response towards Zn in Crotalaria may partly explain the facultative hyperaccumulation mechanism displayed by these species. This root response towards Zn may ultimately affect Zn phytoextraction efficacy when utilising Crotalaria species in a heterogenous Zn soil substrate. These findings highlight the need for rhizosphere investigations prior to field phytoextraction applications.

Trace element enrichment mechanisms in black shales during the early cambrian (ca. 521–514 Ma), South China

It is widely accepted that significant perturbations in ocean redox states are closely related to biological evolution during the early Cambrian. However, the host and geochemical cycle of redox-sensitive elements (V and Zn) of the Niutitang Formation shale in South China have not been well-constrained. This study reports lithofacies, mineralogy and geochemical data of high-resolution samples from slope and basin settings (Xa1 and Xb1 wells, Hunan Province), to evaluate the significance of redox condition and hydrothermal contribution to trace element accumulation during the early Cambrian. Our results reveal the Zn-rich host is primarily sphalerite, while the V-rich host includes organic matter, illite, and anatase minerals in the Niutitang shale. Illite and anatase minerals have significant V concentration (14.8% and 18.3%), whereas organic matter contains relatively lower V concentration (1.4%). Trace elements can be scavenged by dissolved organic matter in seawater, and then taken up by clay minerals or form sulfide during deposition/diagenesis of organic-rich shales. Although seawater restriction of the lower member (LM) shale was stronger than in the upper member (UM) shale, euxinic conditions were more conducive to V and Zn enrichment than ferruginous conditions. Specifically, dwindling concentrations of V and Zn in seawater existed in South China during deposition of the early LM shale. However, the ocean experienced episodic hydrothermal activity, which may have supplied abundant trace elements to supplement seawater content. Overall, we propose that the V and Zn geochemical cycles in the early Cambrian paleo-ocean were controlled by redox condition, organic matter, and the trace element inventory of seawater.

Elemental and boron isotopic variations in tourmaline in two-mica granite from the Cuona area, Tibet: Insights into the evolution of leucogranitic melt

Two-mica granite is the most common magmatic rock type in the Himalayan leucogranite belt, which has close relationship with rare metal mineralization. Its genesis is generally attributed to magmatic differentiation. In recent years, the mineral geochemical compositions are increasingly used to study magmatic differentiation, which are significant for deciphering the melt evolution and element migration processes. In this study, in-situ major and trace element and boron isotope compositions for tourmalines from two-mica granites in the Cuona and Cuonadong leucogranites in the Cuona area are conducted to determine microscopic changes in mineral assemblages and geochemical compositions. Analytical results show that the tourmalines in the Cuonadong leucogranite were crystallized earlier relative to the tourmalines in the Cuona leucogranite during magmatic differentiation. The volatile contents have a genetic relationship with incompatible elements in tourmaline, which is possibly responsible for the formation of tourmaline zonation and the enrichment of Sr, Zn, and Pb during magmatic differentiation. The B isotopic composition of tourmaline in the Cuona area suggests that the granitic magma was dominantly derived from the partial melting of the metasedimentary source rocks. Their B isotope variations likely resulted from fluid exsolution during B-rich melt evolution. High rare metal contents in tourmalines indicate that the two-mica granites in the Cuona area may have great mineralization potential.

Sediment-associated heavy metal contamination and potential ecological risk along an urban river in South Africa

Sediment contamination by heavy metals poses one of the worst environmental risks to aquatic ecosystems worldwide. The study explored sediment-associated heavy metal contamination and potential ecological risk along the Molopo River in Mahikeng, South Africa. Total concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), and zinc (Zn) were analysed using inductively coupled plasma mass spectrometry. Various indices were applied to assess the level of contamination and ecological risk. Most heavy metal concentrations at selected upstream and downstream sites were below average shale, except Cr, Cu, Hg, Pb, and Zn. The contamination factor (CF) indicates that the level of contamination was low (CF < 1) at most sampling sites, except Cr, Cu, Pb and Zn, which varied from moderate (1 CF < 3) to considerable (3 ≤ CF < 6) contamination. The enrichment factor (EF) shows that Cd, Cr, Cu, and Zn were moderate (2 EF < 5) to significantly enriched (5 EF < 20) at the affected sites. The results suggest anthropogenic enrichment (EF > 2) of Cd, Cr, Cu, and Zn. The threshold effect concentration and probable effect concentration sediment quality guidelines predicted that Cr, Cu, and Ni concentrations were more likely to have harmful effects on bottom-dwelling organisms. Pearson correlation and principal component analysis reveal that Cd, Cr, Cu, Ni, Pb, and Zn had a common anthropogenic source. We attribute the source to industrial and wastewater effluent, vehicle traffic, and runoff from various urban surfaces in the city. The study provides baseline data for heavy metal monitoring in the study area. Future research and monitoring should focus on heavy metals that cause concern because of their concentrations (Cr, Cu, Pb, and Zn) and potential ecological risk (Cr, Cu, and Ni).

Whole rock and mineral chemistry of the rare metals-bearing mylonitic rocks, Abu Rusheid borehole, south Eastern Desert, Egypt

Abu Rusheid area represents one of the typical rare metals-bearing rocks in the Northern Neoproterozoic Arabian-Nubian Shield. The current work reports a new detailed lithologic description, petrographic, and mineralogical studies integrated with a geochemical investigation of the borehole no.5 to discern the petrological features, rare metals enrichment and their origin. Abu Rusheid mylonitic rocks are composed mainly of quartz, K-feldspars (Or62-98), plagioclase (Ab98-99), primary muscovite, and neoformed biotite of annite type as well as some accessories such as zircon, columbite, tantalite, fluorite, allanite, xenotime, monazite, and kasolite. They have a noticeable high content of rare earth elements and a conspicuous enrichment of Zr (up to ∼ 4400 ppm), Nb (up to ∼ 2150 ppm), Ta (up to ∼ 270 ppm), Hf (up to ∼ 190 ppm), Zn (up to ∼ 5600 ppm), U (up to ∼ 175 ppm), Pb (up to ∼ 900 ppm) and Th (up to ∼ 1000 ppm) trace elements. REE patterns revel M-type tetrad effect (t1) with an absence of the W-type tetrad segment in the third tetrad (t3). Further constrains, lambda method (where τ2 can be detected) yield a positive values of τ1 (av. 0.534), τ2 (0.487), τ3 (0.498) and τ4 (0.28) for the examined rocks, reflecting M-type tetrads. The rare metals enrichment are related to magmatic as well as the extrusion of lamprophyre dykes yielding alteration processes that led to the remobilization and enrichment of these elements through joints, faulting and their deposition along contacts with the ophiolitic mélange.

Manganese Mobility in Gale Crater, Mars: Leached Bedrock and Localized Enrichments

AbstractIn Gale crater on Mars, the rover Curiosity has discovered evidence of fluid mobilization of the redox‐sensitive element manganese. We present results for Mn from Curiosity's Alpha Particle X‐ray Spectrometer (APXS), which show that the average MnO concentration in mudstone‐dominated sedimentary units (0.22 wt%) is about one‐half of the concentration in the average Mars crust (0.44 wt%). Geochemical trends indicate that Mn in the sedimentary bedrock, most of which has a basaltic provenance, was leached by chemical alteration and dissolution. In &gt;350 vertical meters of mudstone‐dominated strata, the apparent leaching of Mn and retention of Fe in Fe‐O‐H phase(s) resulted in the fractionation of Fe and Mn, indicating relatively moderate Eh‐pH fluid conditions that were not highly alkaline, reducing, or oxidizing. Exceptions are fracture‐associated, silica‐rich haloes where both Mn and Fe were leached by low pH fluids. The rover also discovered Mn‐rich veins, nodules, and patchy, dark coatings on rock surfaces, which are variably associated with enrichments in Fe, P, Cl, and/or Zn. These Mn‐rich features represent ∼1% of the 1029 APXS measurements acquired over ∼25 km of rover traverse. A thermochemical model shows that dissolved Mn2+ could have been concentrated via evaporation, sublimation, and/or freezing. Manganese was then likely precipitated in localized features when &gt;99.99% of the Mn2+‐bearing water was removed from the system. These findings indicate that Mn was mobile in Gale crater and therefore bioavailable as a potential energy source for life.

Ultrasonic-assisted soldering of sapphire through metallic transition layers of Al and Zn using Sn-xZn-2Al solder alloys

Ultrasonic-assisted soldering has potential in the electrical industry especially for the joining of ceramics. The Al-activated Sn-based alloys are promising ultrasonic solders due to simple preparation, while the current approaches required long ultrasonic action. In order to increase the efficiency and reduce ultrasonic-induced damage, this study investigated the soldering of sapphire (monocrystalline α-Al2O3) performed under an ultrasonic action for 0.5 s by using Sn-xZn-2Al(x = 9, 25, 45) solder alloys. Microstructures of interfacial transition layers between the sapphire and solders were focused on. It has been found that at the interfaces no interfacial reaction phases formed and the interfacial bonding was realized via metallic transition layers. Three kinds of interfacial structures existed, that is, sapphire/Al atomic layer/β-Sn, sapphire/Al atomic layer/(Zn enrichment layer)/β-Sn and sapphire/Al atomic layer/Zn nanocrystalline clusters/β-Sn. The elements of Al and Zn in the solder alloys underwent a selective and asynchronous adsorption process during the ultrasonic action. An Al atomic layer formed on the sapphire surface by the stronger chemical adsorption and acted as a transition layer between sapphire and β-Sn. The Zn enrichment layer was distributed locally along the interface and as the Zn content increased in the solder alloys, more localized Zn nanocrystalline clusters formed. These Zn transition structures strengthened the interfacial bonding by transforming the Al atomic layer/β-Sn interface into the Al atomic layer/Zn transition structures/β-Sn interfaces. The joints possessed a shear strength of up to 28 MPa when soldering with Sn–45Zn–2Al at 350 °C.

Heavy Metal Pollution and Source Contributions in Agricultural Soils Developed from Karst Landform in the Southwestern Region of China.

Heavy metal pollution of soil in agricultural areas is the most prominent environmental pollution problem in China, seriously affecting human health and food security. It has become one of the environmental problems to which all sectors of society attach great importance. Soil heavy metals in the weathering area of hazardous geological bodies in southwest China have naturally high background attributes. Therefore, ecological risk assessment and analysis of potential sources of soil heavy metals in southwest China is of great significance for soil health management, soil heavy metal pollution control and territorial spatial planning. In this study, we collected 787 soil samples (0–20 cm) in Xuanwei County in China and analyzed the concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in soils. Igeo, RI, HI and CR were used to calculate the pollution levels, ecological risks and human health risks. Additionally, the PMF model and one-way ANOVA were used to identify the potential sources and discuss the factors affecting the enrichment of heavy metals. The results showed that the mean contents of the surface soils were 1.190 (Cd), 139.4 (Cr), 96.74 (Cu), 0.081 (Hg), 56.97 (Ni), 46.66 (Pb) and 130.1 (Zn) mg/kg. All heavy metals exceeded the background values of the A layer soil in Yunnan Province. The Igeo showed that Cd was the most hazardous element in the study area, followed by Cu, Cr, As, Ni and Pb. The RI showed that low ecological risks, moderate ecological risks, considerable ecological risks and strong ecological risks accounted for 3.81%, 55.27%, 37.74% and 3.18%, respectively, of the total samples, and Cd was the main dominant element. The HI values of the As element in children were greater than 1, indicating a non-carcinogenic risk, and other elements’ risks were acceptable. The CR values of Cr and Ni were higher than their limits (1 × 10−4), and both had carcinogenic risks in children and adults, as did As in children. According to the PMF model, four heavy metals sources were identified: geological sources (32%), sources from mining activities (19.38%), atmospheric deposition sources (17.57%) and agricultural sources (31.05%). Thereinto, As and Pb were mainly derived from agricultural sources, Cd and Cr were mainly associated with geological sources, Cu was largely from mining activity sources, Hg was mainly from atmospheric deposition sources and Ni and Zn were mainly from geological sources, mining activities and agricultural activities. The parent material has a significant influence on the enrichment of heavy metals in the soil, and the heavy metals are significantly enriched in the carbonate parent material and quaternary parent material. Topography also plays a role in heavy metal accumulation; Cd, Cr, Cu, Ni and Zn gradually decreased with the increase in altitude, and As and Pb increased with the increase in altitude. Mn-oxide played a crucial part in the enrichment of Cu and Zn, while SOC, K2O and pH had little influence on the accumulation of heavy metals.

Metals in Lake Sediments as Indicators of Human Activities in Prehistory: Case Study of the Southeastern Baltic, Kamyshovoe Lake

This paper presents the results of geochemical research on the Kamyshovoe Lake sediments (Kaliningrad oblast, Russian Federation). The study of Pb, Ni, Zn, As, Co and Cu concentration and enrichment factors (EF) combined with the results of the lithological, geochronological, magnetic susceptibility and microcharcoal studies revealed possible anthropogenic sources of metals in southeastern Baltic lake sediments from the Neolithic to the Medieval period. Increasing Co EF value and peaks of the Pb EF in Kamyshovoe Lake sediments, starting from ~6000 cal yr BP in the Neolithic, probably show the growing role and usage of metals as dyes and fixatives. Since ~3100 cal yr BP, in the end of the Bronze Age, a simultaneous increase in the content of indicators of metallurgical production Pb, Ni, Zn and As, coinciding with growth of the microcharcoal curve, can show a growing demand for metal objects in the southeastern Baltic region and the input of the local or regional ancient metallurgy into the metal pollution of the lake sediments.

Heavy metal background levels and pollution temporal trend assessment within the marine sediments facing a brownfield area (Gulf of Pozzuoli, Southern Italy)

In this study, site-specific natural background levels (NBLs) were determined for 18 elements (Al, As, Be, Cd, Co, Cu, Cr, Fe, Hg, K, Mn, Mo, Ni, Pb, Tl, U, V, and Zn) in two sediment cores collected offshore the Bagnoli-Coroglio brownfield site (Gulf of Pozzuoli, southern Italy) to accurately assess the degree of contamination and the historical trends in Heavy Metals (HMs) enrichment. This objective was pursued taking in account the high temporal and spatial variability of the geochemical properties of the area due to the local geothermal activity. Moreover, the temporal variation of Polycyclic Aromatic Hydrocarbons (PAHs) was investigated.226Ra was used as an extraordinary marker to confirm 210Pb dating. It especially allowed defining the geochronological framework of the sediment core closer the brownfield up to around 1500, providing compelling support to correlate the investigated elements’ occurrences with natural geogenic dynamic. Sediment samples were accurately dated and analyzed for chemical and particle size composition. The contamination factor (Cf) and the pollution load index (PLI) showed very high enrichment of Cd, Cu, Hg, Pb, and Zn. The contamination profiles of HMs and PAHs follow the same pattern in both sediment cores, increasing from deep to upper layers. The highest contamination levels for HMs and PAHs were observed between 10 and 30 cm, corresponding to the periods of most intense industrial activity. Decreasing trends of pollutants were observed in the surface layers (0–10 cm), probably affected by a natural attenuation process due to the cessation of industrial activities.

Assessment of heavy metal contamination of an electrolytic manganese metal industrial estate in northern China from an integrated chemical and magnetic investigation.

Heavy metal concentrations (Al, V, Mn, Fe, Co, Ni, Cu, Zn, and Pb) and the magnetic properties of soil and sediment samples in/around an electrolytic manganese metal (EMM) industrial estate in northern China were investigated. Potential enrichment of Mn, Zn, and Pb was found in/around the core area of the EMM industrial estate; however, the pollution load index (PLI) values did not indicate severely polluted levels. For adults, all hazard index (HI) values of noncarcinogenic risks in the soil samples were below the safe level of 1.00. For children, none of the HI values exceeded the safe level, except Mn (HI = 1.23) in one industrial estate sample. The particle size of magnetic materials was mostly in the range of stable single-domain, and coarser ferrimagnetic phases enhanced the magnetic parameters in the industrial estate soils. Highly positive correlations were found between magnetic parameters, heavy metal concentrations, and PLI values, demonstrating that the magnetic parameters are an efficient proxy for assessing heavy metal contamination. Enrichment of Mn, Zn, and Pb was mainly derived from the EMM industry. The data showed that the EMM industrial estate under cleaner production had limited adverse impacts on the adjacent environment from the perspective of heavy metal contamination.

TWO STAGES OF THE CENOZOIC ALKALINE-BASALT VOLCANISM IN THE DARKHAD DEPRESSION (NORTHERN MONGOLIA) – GEOCHRONOLOGY, GEOCHEMISTRY, AND GEODYNAMIC CONSEQUENCES

The isotopic data showed that there are two stages distinguished in the Cenozoic history of the Darkhad depression volcanic activity, the Late Oligocene initial stage (~28.0–26.6 Ma) and the final Late Miocene – Early Pliocene stage (~5.8–4.2 Ma). It has been stated that the rocks of the initial stage are only represented by trachybasalts; however, among the final-stage basaltoids there are series of shield-volcano hawaite-basanite-phonotephrite rocks and compex trachybasaltic "valley" lava flows, the formation of which is the last stage in the territorial volcanic evolution. It has been shown that the initial-stage trachybasaltic andesites are characterized by their enrichment of TiO2, P2O5, Sr, Zn, Ga and low concentrations of Al2O3, MnO, CaO, Sc and HREE (La/Yb=27.2–30.2). Basaltoids of the final stage have a similar rare-element distribution and show an increase in the contents of TiO2, Al2O3, P2O5, LILE, HFSE, Th, U and in the degree of fractionation of REE (La/Yb from 12.2 to 20.9) towards the rocks alkalinity enhancement. Modeling of eclogite, pyroxenite and peridotite melting processes in the La/Yb – Sm/Yb system shows that trachybasaltic andesite melts could be formed at ~7–8 % melting of eclogitic matter or at ~10–11 % melting of Grt-containing pyroxenites, with trachybasalt formed at ~3 % melting of Grt-containing peridotites. The composition distribution of rocks in coordinates (Mg# – Fe/Mn) indicates that the parental magmas are the initial-stage trachybasaltic andesite magmas as well as the Early Pliocene trachybasaltic "valley" lava flows. Sr, Nd, Pb isotope characteristics of the Darkhad depression basaltoids show significant shift of isotopic ratios in time towards the relatively enriched mantle as compared with the depleted MORB mantle. The initial formation of trachybasaltic andesite melts occurred in the Late Oligicene at the pre-rift stage of the territory development involving metasomatized mantle matter, with the pyroxenite or eclogite component contained in the magma formation source. The origin of trachybasalt magmas of the final stage is associated with the processes of decompression melting of peridotites in a weakly metasomatized lithospheric mantle at the rift stage of the Darkhad structure development.

Detection and Assessments of Sources and Health Hazards Caused by Heavy Metals in the Dust of Urban Streets in Harbin, Northeast China

To investigate heavy metals (HMs) in the dust of the urban streets and evaluate health hazards through dust pollution exposure, this research implements an analysis method called principal component analysis and a model called positive matrix factorization to investigate the associations between HMs and their plausible allocation of sources. A total number of 118 dust samples were collected from Harbin, China, which is one of the most eloquent industrial hubs and tourist destinations. The results suggest that the mean concentrations of Cd, Cr, Cu, Zn, Ni, Pb, and Mn are 1.79 ± 1.618, 67.23 ± 32.84, 57.76 ± 51.50, 328.52 ± 117.62, 27.11 ± 4.66, 83.03 ± 25.39, and 745.34 ± 153.22 mg kg−1, respectively. The erratic enrichment of Cu, Zn, Pb, and Cd is succeeded by a geo-accumulation index and the factors that are used for enrichment. Both the spatial distribution and correlation analysis imply that Cu, Zn, Pb, and Cd can be controlled by anthropogenic activities. On the contrary, Cr, Mn, and Ni can be ascribed to natural sources. The hazard quotients are less than 1, and the hazard indexes for seniors and kids are 0.129 and 0.852, respectively. So, kids had more non-carcinogenic hazards than the older individuals did. Both groups have carcinogenic risks of less than 1 × 10−6. The results indicated that street dust could not be potentially accepted as a health hazard for dwellers. Cu, Zn, Pb, Cr, Ni, and Cd existed in the street dust of the research region and have been influenced by the combination of industrial and traffic sources and domestic coal combustion, and the parent material that forms soil affects the levels of Mn. A model, called the PMF, is implemented in the study of street dust pollution sources, enhancing the reliability and accuracy of pollution source determination, and presenting some potential applications.

A record of metasomatism and crustal contamination of the Mediterranean lithosphere in chromitites of the Orhaneli Ophiolite Complex (NW Türkiye)

• Orhaneli chromitites include Middle Devonian to Mesoproterozoic zircon and rutile . • Chromite trace elements points a metasomatic signature in relics within chromitites. • More data should be sought for ultrahigh-pressure history of Orhaneli chromitites. This study provides the first-ever report of U-Pb isotopic ages of zircon and rutile from high-Cr chromitites of the Orhaneli Ophiolite Complex (OOC). The chromites within the OOC chromitites yield Cr-numbers between 0.77 and 0.86, Mg-numbers between 0.46 and 0.71 and TiO 2 < 0.26 wt%. They exhibit V, Ga and Ni depletion and Sc, Ti, Zn, Co and Mn enrichment relative to MORB spinels, with significant Sc and Ti positive anomalies. This, and the Al 2 O 3 and TiO 2 compositions of the parental melts, suggest that the studied chromitites formed from island arc melts of boninitic affinity, in a supra-subduction environment. In addition to zircons, chromites host other solid mineral inclusions, including Os- and Ir-dominant platinum-group minerals (PGM), base-metal sulfides (BMS), alloys, ubiquitous silicate (some as micron-sized oriented lamellae), and two poorly defined Fe-Cr-O and Ti-Si-C grains. The zircons show Th/U ratios typical for magmatic zircons from felsic melts, and present Middle Devonian to Mesoproterozoic U-Pb isotopic ages. Although the reworked/resorbed forms of the zircons suggest a xenocrystic origin, coupling of U-Pb data from some zircons and rutile with the Ti positive anomaly in the chromites raises the possibility for an earlier Neoproterozoic metasomatic event affecting the relics now included within the chromitite bands. The current state of knowledge about the silicate micro-lamellae within the chromites has prompted reassessment of their early interpretation as direct evidence of deep mantle recycling. We currently suggest a more cautious approach on this issue by seeking additional evidences for an ultrahigh-pressure (UHP) history.

Efficacy of Nitrogen and Zinc Application at Different Growth Stages on Yield, Grain Zinc, and Nitrogen Concentration in Rice

Zinc (Zn) is an essential element involved in human metabolism, which can be supplied by an appropriate diet. Enhancing Zn enrichment in rice grains through agronomic biofortification is advocated as an immediate and effective approach to combat micronutrient malnutrition in hu-man. It has been well-documented that high grain Zn accumulation in rice can be achieved by Zn fertilizers management. This study evaluated the effects of foliar nitrogen (N) and Zn applied at the flowering and milky stages of brown rice plants with and without soil Zn application. A glasshouse pot experiment was conducted using a completely randomized design with four replicates. Soil Zn in the form of ZnSO4 was applied at 0 and 50 kg ha−1. Foliar fertilizer of 1% urea along with 0.5% ZnSO4 was applied and assigned as (1) nil foliar N and Zn (N0Zn0), (2) foliar N with nil Zn (N+Zn0), (3) nil foliar N with foliar Zn (N0Zn+), and (4) foliar N and Zn (N+Zn+) at flowering and milky stages. Foliar application of N and Zn increased grain yield and yield components in both soil Zn conditions. Grain Zn concentration in brown rice was the highest when foliar N and Zn were applied under nil soil Zn conditions; however, grain N concentration decreased by 13.1–28.5% with foliar application at flowering and 18.8–28.5% with application at the milky stage. The grain Zn content was increased by foliar application of N0Zn+ and N+Zn+ at flowering and milky stages. Applying foliar N and Zn at flowering or milky stages tended to increase the grain N content when Zn was applied to the soil, while nil soil Zn decreased the N content by 26.8% at flowering and milky stages under N0Zn+. The results suggest that the milky stage is the most suitable for foliar application of Zn for increasing (i) grain yield and (ii) N and Zn concentrations in brown rice without having a dilution effect.

Zinc nutrition improves fruit yield, quality, and reduces bacterial blight disease severity in pomegranate (Punica granatum L.)

The study was designed to identify the most effective way of fertilizing Zn for improved productivity and quality of pomegranate cv. Bhagwa on calcareous soil. Fertilization methods included foliar sprays of ZnSO4, Zn-EDTA, and amino acid chelated Zn; irrigation applied ZnSO4 and Zn chelate (Zn-EDTA); soil application of ZnSO4 (@ 12.5 and 25.0 g tree−1) and were evaluated on full grown pomegranate orchard for 2 years. All the Zn treatments of foliar and irrigation-applied methods were effective in raising the leaf Zn concentration above the recommended adequate level (>15.98 mg kg−1). Higher number of hermaphrodite flowers was observed with foliar sprays of ZnSO4, amino acid chelated Zn, irrigation applied Zn-chelate, and soil application of ZnSO4 @ 25 g Zn tree−1. Various Zn application methods except irrigation-applied ZnSO4 increased fruit yield by 4.33–23.63%. Some of the Zn treatments viz. foliar sprays of ZnSO4, amino acid chelated Zn and irrigation-applied Zn-chelate caused substantial improvement in fruit quality attributes such as fruit size, aril and juice percent, biochemical attributes like juice acidity (by 8.33–13.89%), anthocyanin, ascorbic acid concentration, and enrichment of Zn in the edible part of the fruit. Interestingly, sprays of ZnSO4 also enriched Fe, Mn, and Cu in the arils. While some of the Zn treatments viz. foliar spray of ZnSO4, irrigation-applied Zn-chelate and soil application of ZnSO4 could reduce bacterial blight disease incidence by 19.29–25.97% and severity by 22.18–47.36%. Hence, foliar sprays of ZnSO4 are recommended for enhancement of fruit yield as well as quality in pomegranate.

Cadmium geochemistry and groundwater pollution status evaluation using indexing and spatial analysis for Keffe community and Environs Sokoto Basin, North Western Nigeria

Representative groundwater samples were collected from the Kaffe community and environs to evaluate the concentrations and geochemical constraints for mobilizing cadmium (Cd) and selected heavy metals. Field-based in-situ measurements of physicochemical parameters were combined with Atomic Absorption Spectrophotometer analysis of dissolved elemental concentrations. Pollution indices (i.e. heavy metal pollution index; HPI, heavy metal evaluation index; HEI, contamination degree; Cd, metal index; MI, synthetic pollution index; SPI, ecological risk index; ERI and Nemerow index; NI) evaluations highlighted the levels of heavy metals in the groundwater. Cadmium and iron (Fe) concentrations exceeded the recommended limits in 97% of the analysed samples, with an average pH of 6.3. Strong positive correlations were observed between cadmium and the computed pollution indices (p 0.774 to p 0.100), suggesting significant Cd pollution of the groundwater. Components analysis grouped Cd, Fe, and the pollution indices in the first PC. This was favourably compared to the correlation analysis result. Cluster analysis categorized Cd, Zn and pH in the first cluster consistent with the suggested dissolution and enrichment of Cd and Zn in the groundwater under similar geochemical conditions. The study area is medium and moderately polluted based on HPI, HEI, Cd, and NI.

Experiment and mechanism study on enrichment of heavy metals during MSW pyrolysis by modified kaolin.

Experiment and mechanism studies on the enrichment of Pb, Cd, Zn, As, and Cr by modified kaolin were investigated during MSW (municipal solid waste) pyrolysis at 450 ~ 650°C. The results showed that γAlOK(micro- and nano-γAl2O3 by hydrothermal method modified kaolin) was relatively selective for the solid phase enrichment of Cr and As, while CaHPK (CaHPO4 impregnated modified kaolinite) was more advantageous for the adsorption of Pb and Zn, which might be related to the thermal stability of γAl2O3 and the thermal conversion of CaHPO4. Compared with the original kaolin, the adsorption and retention capacity of γAlOK for As was improved by 20 ~ 30%. Moreover, the retention rate of modified kaolin for Cd decreased from 66.75 to 30.30% at 450 ~ 650 ℃, and the effect of temperature on the volatilization of Cd was always greater than the active components on the surface of modified kaolin. In the fluidized bed experiment, the physical mixing of different modified kaolin achieves complementary advantages on the retention capacity of heavy metals. In addition, the ∆E between Ca2P2O7 and PbCl2 is smaller than that of γAl2O3 at 500 ~ 650°C, i.e., their electron transfer induction is stronger, and therefore more favorable for electron transfer and stable chemical bond formation.

Effect of Milling of ZnO and MgO Powders On Structural, Optical, and Electrical Properties of (Mg,Zn)O Ceramics

The effect of the milling of virgin ZnO and MgO powders on structural, optical, and electrical properties of Mg0.2Zn0.8O ceramics is studied. In all Mg0.2Zn0.8O ceramics, both cubic and hexagonal phases of solid solution are formed simultaneously. The hexagonal phase is represented by densely sintered grains that are doped with magnesium homogeneously. The crystallites of cubic phase of solid solution turn out to appear in large pores. The infrared reflection spectra show that the milling of intial powders does not affect free carrier concentration in hexagonal grains. It is found to be close to that of ZnO being determined by Zn interstials. For ceramics sintered from virgin powders, a decrease of direct current conductivity of Mg0.2Zn0.8O in comparison with that of pure ZnO occurres, which is being caused by the appearance of barriers, the nature of which may be ascribed to the fluctuations in the bandgap and/or electron concentration. For ceramics sintered from milled powders, an increase in DC conductivity of all samples is found and attributed to the formation of conductive channels along the grain boundaries via their enrichment in Zn and Mg due to mechanical stress. A chemical mapping of the ceramics supports this effect.