Fractions Of Zn Research Articles

Elucidating the Potential of Biochar-Bentonite Composite and Kaolinite-Based Seed Balls for the Remediation of Coal Mining Impacted Heavy Metals Contaminated Soil

Globally, open-pit coal mining is associated with severe land use impact and the contamination of soil and water resources with heavy metals. Thus, in growing economies like India, where coal is a significant energy source, the heavy metals contamination of soil and water become ubiquitous. This study uses a unique remediation approach by developing biochar-bentonite-based seed balls encapsulating Shorgham grass seeds at their core for application in the contaminated soil. The seed ball was developed by using the bentonite biochar composite in varying weight fractions of 0.5–5% with respect to the kaolinite, whose fractions in the seed ball also varied at one, three, and five parts. The seed balls were applied to the pots containing 3 kg of heavy-metals-contaminated soil for a pot-culture study in a polyhouse for a period of four months. Initial soil analysis results indicated that the mine soil samples showed poor nutrient and organic matter content and were contaminated with heavy metals such as Ni, Zn, Cr, and Cd. Post-pot-culture soil analysis results indicated that the application of seed balls containing five fractions of biochar composite with its combination with three and five-weight fractions of kaolinite showed substantial improvement in the pH, available nutrients, organic matter content, soil enzymes, and overall soil fertility index compared to the controlled study and other cases. The same combination of seed balls also significantly reduced the plant-available fractions of Ni, Zn, Cr, and Cd in the soil, indicating the stabilization of heavy metals within the soil matrix. Also, the application of seed balls substantially improved the plant physiology and reduced the release of stress hormones within the plant cells, indicating improvement in the plant’s biotic and abiotic stress factors. Thus, the application of seed balls in heavy metals contaminated soils, particularly over a large stretch of land, could be a low-cost and viable remediation technique.

Photochemical vapor generation of Zinc and Gallium

Photochemical vapor generation (PVG) of Zinc (Zn) and Gallium (Ga) was firstly reported in this study. The main parameters influencing PVG of Zn and Ga were investigated with inductively coupled plasma mass spectrometry (ICP-MS), such as the type and concentration of low molecular weight organic acids (LMWOAs), the concentration of transition metal ions and their synergistic effects, the wavelength and time of UV irradiation, and pH of sample solution. Formic acid (FA) and Cu2+ were required for the generation of volatile species of Zn and Ga. In addition, the effects of interfering ions on the PVG of Zn and Ga were investigated. Good precisions with 2.3% and 2.7% were obtained under the selected conditions for replicate measurement of 200 ng mL−1 Zn and Ga standard solution (n = 7), respectively. The limits of detection (LOD, 3σ, n = 11) were calculated to be 8.8 ng mL−1 and 0.77 ng mL−1 for Zn and Ga with PVG-ICP-MS measurement, respectively. Carbonyl compounds were speculated to be formed in this study. Moreover, nanoparticles containing Cu, Zn or Ga were found in liquid solution after UV irradiation, which may be useful for investigating the formation of natural nanoparticles in environment as well as the isotope fractionation of Zn and Ga in photochemical processes.

Effects of Biochar and Apatite on Chemical Forms of Lead and Zinc in Multi-Metal-Contaminated Soil after Incubation: A Comparison of Peanut Shell and Corn Cob Biochar

Heavy metal pollution in soils caused by mining activities is a severe issue worldwide. It is necessary to find a suitable approach to mitigate heavy metal-contaminated soil. Yet little is known about how soil amendments affect the chemical forms of heavy metals. Biochar produced from peanut shells (PSB300) and corn cob (CCB300) at 300 °C, and apatite (AP) were applied at various ratios to investigate their ability to adsorb lead (Pb) and zinc (Zn) in contaminated soil. The Pb and Zn’s chemical fractions were analyzed utilizing Tessier’s sequential extraction procedure and quantified using inductively coupled plasma mass spectroscopy. The one-month amendment incubation of biochar and AP could significantly diminish Pb and Zn’s exchangeable fractions, and CCB300 showed a slightly better effect on declining the exchangeable fractions of Pb and Zn than PSB300, which might be attributed to the higher values of OC and EC of CCB300 than those of PSB300. Moreover, the amendments could also transform the exchangeable fractions of Pb and Zn into stable fractions, resulting in immobility in natural conditions. Thus, PSB300 and CCB300 and the mixture of biochar/apatite could be hopeful amendments for immobilizing heavy metals in heavy metal multi-metal-contaminated field soil.

Responses of soil microarthropods to soil metal fractions under different mediterranean vegetation covers

Soil microarthropods play essential roles in soil functioning and they are considered useful indicators of soil metal contamination, as they quickly respond to environmental changes. The toxicity of metals depends on their fractions, but few studies have been conducted on the responses of microarthropods to different metal fractions. The study aimed to assess the response of the soil microarthropods to the soil metal fractions (exchangeable: available for organisms, reducible: associated to Fe-Mn oxides, oxidizable: associated to organic matter) under different Mediterranean vegetation covers. To reach the aim, the soils of different vegetation covers (holm oak, pine, black locust and herbs) were analysed for pH, water content, total C, N and P and Corg, NH4+ and Passimilable contents, the exchangeable (F1), reducible (F2) and oxidizable (F3) fractions of Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, V and Zn and the microarthropod taxonomic and functional indices. The results showed that, regardless the vegetation cover, the F2 and F3 of Ca, Cr, Cu, Fe, K, Mg, Mn, V and Zn significantly inhibited the density of microarthropods, favouring the functional traits typical of disturbed environments. The element F1, except for Mn, slightly impacted on the microarthropod community. In addition, the soils under trees positively influenced the taxonomic and functional indices of the microarthropod community where higher contents of Corg and macronutrients were observed. Several taxa were differently impacted by three metal fractions of Al, Ca, Fe and K; in particular, Formicidae were favoured, whereas Diplopoda and Isopoda were favoured by Ca, Fe and K and inhibited by Al concentrations. The present research demonstrated that stable fractions (F2 and F3) of metals, instead to available one, exert a strong impact of microarthropod community. This leaded to change in microarthropod community assemblage, favouring taxa and traits typical of disturbed environments.

Kinetics, product properties, and migration of heavy metals during co-pyrolysis of textile dyeing sludge and litchi shells

In this study, the co-pyrolysis behavior, products, and the migration of heavy metals (HMs) during the co-pyrolysis of textile dyeing sludge (DS) and litchi shells (LS) were investigated. Thermogravimetric (TG) analysis was used to identify the pyrolysis stages of mixtures, and the activation energy (Ea) of the main pyrolysis stages was calculated by Kissinger Akahira Sunose (KAS) method. The average of Ea decreased from 326.1 to 232.5 kJ/mol with increasing the proportion of LS. The bio-oil compositions indicated that the interaction effect between DS and LS mainly promoted the generation of phenols and acid compounds and inhibited the production of nitrogenated compounds, ketones, and ethers. The emission characteristics of gases from the co-pyrolysis of three samples were analyzed by TG-FTIR. The results found that the addition of LS could inhibit the generation of NOx precursors. Finally, LS in co-pyrolysis was beneficial to the increase of Cu, Zn, Cr, and Ni stable fractions (F3 +F4) to 96%, 69%, 99% and 80%, and the potential Ecological Risk Index (RI) of biochar was reduced to 7.26. This study provided a cleaner and more efficient idea for co-pyrolysis strategy and resource utilization of solid waste.

Competitive sorption and desorption of cadmium, lead, and zinc onto peat, compost, and biochar

Soil and water contamination by potentially toxic metals (PTMs) has exerted adverse environmental impacts, which justifies studies of promising remediation alternatives. This article investigated the competitive sorption of cadmium (Cd), lead (Pb), and zinc (Zn) onto peat, compost, and biochar derived from the organic fraction of municipal solid waste (OFMSW), but its main innovation was the post-sorption assessment. The effects of contact time on competition between contaminants were systematically analyzed by batch experiments and the effectiveness of the sorption process was evaluated in desorption tests (H2O, HCl, NaOH, and NaCl) and sequential extraction. Kinetic data were well-fitted to pseudo-first-order (PFO) and pseudo-second-order (PSO) models and the intra-particle diffusion model revealed the existence of multiple linear regions, indicating the sorption process was controlled by a multi-step mechanism. The sorption capacities followed a biochar > compost > peat order, with biochar retaining more than 99% of Cd, Pb, and Zn in all samples. The general order of desorption percentage was peat > compost > biochar, with a below 0.60% biochar release, suggesting the importance of chemical processes. HCl solution (more acid pH) showed the highest release of previously sorbed contaminants and, therefore, can be employed for the reuse of sorbents (sorption/desorption cycles). The only exception was Pb desorption on biochar, with maximum release in NaOH solution. A negative Pearson correlation with F1 (acid-soluble/exchangeable fraction) for Cd and Zn and a positive one with the other steps were reported. Pb exhibited an opposite behavior, showing the highest sorption performances and the lowest desorption rates for all sorbents, justified by positive correlations with F4 (residual fraction) and negative ones with desorption. The findings suggest the evaluated sorbents, especially compost and biochar, can be effective materials in the simultaneous sorption of Cd, Pb, and Zn in wastewater, as well as an amendment for PTMs immobilization in contaminated soils.

Geochemical fractionation, bioaccessibility and ecological risk of metallic elements in the weathering profiles of typical skarn-type copper tailings from Tongling, China

Nonferrous metal tailings have long posed a significant threat to the surrounding environment and population. Previous studies have primarily focused on heavy metal pollution in the vicinity of sulfide tailings, while little attention was given to metal mobility and bioavailability within skarn-type tailings profile during weathering. Therefore, this study aimed to investigate the fractionation, bioaccessibility, and ecological risk associated with metallic elements (MEs, including Pb, Cd, Cr, Zn, and Cu) in two representative weathering copper-tailings profiles of Tongling mine (China). This was achieved through the use of mineralogical analyses, BCR extractions (F1: exchangeable, F2: reducible, F3: oxidizable, F4: residual fraction), in-vitro gastrointestinal simulation test (PBET) and risk assessment models. The mineral compositions of two weathering profiles were similar, with quartz and calcite being the dominant minerals, along with minor amounts of siderite, hematite and spangolite. The mean concentration in the tailings profile was approximately 0.31 (Cr), 1.8 (Pb), 12 (Zn), 33 (Cd) or 34 (Cu) times of the local background values (LBVs). The mean content of the bottom weakly-weathering layer in profile was about 0.36 (Cr), 0.91 (Pb), 1.91 (Cd), 2.73 (Zn) or 2.68 (Cu) times of the surface oxide layer, indicating a strong weathering-leaching effect. The average proportion of BCR-F1 fraction for Cd (30.94 %) was the highest among the five MEs, possibly due to its association with calcite. The PBET-extracted fractions for Cd, Zn and Cu were significantly positively correlated with the F1, F2 and F3 fractions of BCR, suggesting that these elements have higher bioavailability/bioaccessibility. The assessment results indicated that Cd posed a higher health risk, while the risk of Cu, Zn, and Pb is relatively low and Cr is safe. In conclusion, this study provides valuable insights into the environmental geochemical behavior and potential risks of MEs in skarn-type non-ferrous metal tailings ponds.

Influence of Integrated Nutrient Management on Fractions of Zinc and Its Uptake by Indian Spinach (Beta vulgaris L.)

ABSTRACT Zinc (Zn) availability can change with different organic amendments applied. The aim of this study was to evaluate the impact of farm yard manure (FYM) and vermicompost (VC) applied with or without chemical Zn fertilizer on dry biomass yield, Zn uptake by Indian spinach (Beta vulgaris L.), and distribution of various fractions of Zn in post-harvest soil. Results indicated that dry biomass yield and Zn uptake positively responded to the application of FYM or VC alone at 2% as well as in combination with Zn at 5 mg kg−1 through ZnSO4·7H2O. Integrated application of recommended dose of fertilizers (RDF)+2% VC+5 mg kg−1 Zn increased dry biomass yield and Zn uptake by 2.92- and 3.37-folds, respectively, over the control. Integrated application of RDF+2% FYM+5 mg kg−1 Zn was the best combination for increasing water-soluble and exchangeable Zn (WS&EX-Zn), carbonate-bound Zn (CAR-Zn), Fe- and Mn-oxide-bound Zn (FeMnOX-Zn), and organically bound Zn (OR-Zn) fractions. However, the preponderance of different Zn fractions remained the same in all the treatments, viz. WS&EX-Zn < FeMnOX-Zn < CAR-Zn < OR-Zn < Residual Zn (RES-Zn). All the Zn fractions were significantly and positively correlated with DTPA-extractable Zn, dry biomass yield, and uptake of Zn.

Physiological effects of some engineered nanomaterials on radish (Raphanus sativus L.) intercropped with pea (Pisum sativum L.).

Intercropping leguminous plant species with non-legume crops could be an effective strategy to maintain soil fertility. Additionally, the application of nano-Zn and Fe in trace amounts can substantially improve the bioavailable fractionof Zn and Fe. We studied the effect of foliar application of some nanomaterials on the agronomic, physio-biochemical attributes under a radish/pea intercropping system. The radish and pea were sprayed with different nanomaterials (Zn-Fe nanocomposite, nZnO, and nanobiochar) at 0 and 50mg L-1 concentrations. Results indicated that the growth parameters of radish were higher in intercropping than in monocropping, while pea growth was inhibited in intercropping compared with monocropping. The shoot and root length, fresh weight, and dry matter of radish were increased by 28-50%, 60-70%, and 50-56% by intercropping than monocropping. Foliar spray of nano-materials further increased the growth traits of intercropped radish, such as shoot and root length, fresh weight, and dry matter, by 7-8%, 27-41%, and 50-60%, respectively. Similarly, pigments such as chlorophyll a, b, and carotenoids and the concentration of free amino acids, soluble sugars, flavonoids, and phenolics were differentially affected by intercropping and nanomaterials. The yield of the non-legume crop was increased by intercropping, whereas the legume crop exhibited significant growth inhibition due to competitive interactions. In conclusion, both intercropping and foliar spray of nanomaterials could be used as a combined approach to benefit plant growth and enhance the bioavailable Fe and Zn fractions of both crops.

Immobilized sulfate reducing bacteria (SRB) enhanced passivation performance of biochar for Zn

The low survival rate in harsh environments has been hindering the transformation of microbial remediation technology for heavy metal-contaminated soil from laboratory to field application. Therefore, biochar was selected as the carrier in this study to immobilize the heavy metal tolerant sulfate-reducing bacteria of SRB14-2-3 for the passivation of Zn-contaminated soil. The results showed that the immobilized bacteria of IBWS14-2-3 exhibited the highest passivation performance, as the total content of bioavailable Zn fractions (exchangeable + carbonates) in soil with initial Zn concentration of 350, 750 and 1500 mg·kg−1 decreased by almost 34.2 %, 30.0 % and 22.2 % compared to the control group, respectively. In addition, the introducing of SRB14-2-3 into biochar has successfully alleviated the possible adverse effects on soil caused by the application of large amounts of biochar, while the protection of biochar against immobilized bacteria significantly improved the reproduction of SRB14-2-3, since the number of SRB14-2-3 increased by 82,278, 42 and 5 times in three different level contaminated soil. Furthermore, the new passivation mechanism for heavy metals brought by SRB14-2-3 is expected to make up for the deficiency of biochar in long-term application. And more attention should be paid on the performance of immobilized bacteria under field practical application in the future research.

Diffusion-driven Zn and Mg isotope fractionation in magmatic Fe-Ti-Cr oxides and implications for timescales of magmatic processes

Diffusion-driven isotopic fractionation during crystal growth and crystal-melt interaction has important implications for identifying diffusive processes and estimating the timescales of magmatic processes. Especially, Fe-Ti-Cr oxides are common crystalline phases in both relatively unfractionated and highly evolved basaltic magmas and may record the evolution history of the host magmas. High-precision Zn and Mg isotopic compositions for a set of Fe-Ti-Cr oxides and their host lavas in three types of Cenozoic basalts (sodic, transitional and potassic) from northeast China are reported in this study. These oxide crystals exhibit a wide range of chemical compositions (e.g., FeOT = 20.6–49.1 wt%, TiO2 = 1.38–8.70 wt%, Cr2O3 = 16.2–43.1 wt%), reflecting substantial chemical disequilibrium with their host magmas. A large range of δ66ZnJMC-Lyon from −1.12‰ to 0.24‰ and δ26MgDSM-3 from 0.04‰ to 0.80‰ is observed in oxides (n = 17) from all three lava types. Compared with the host basalts, the oxides are enriched in lighter Zn with △66Znoxide-melt (δ66Znoxide–δ66Znmelt) from −1.43‰ to −0.19‰ and heavier Mg with △26Mgoxide-melt (δ26Mgoxide–δ26Mgmelt) from 0.43‰ to 1.13‰. Comparison with existing theoretical work indicates that these isotopic offsets, even if compositional effects of oxides are considered, are too large to be in equilibrium. There are negative correlations between tetrahedral-site Fe2+ + Zn2+ and Mg2+ (R2 = 0.97) and between δ66Zn and δ26Mg (R2 = 0.66) for the oxides, which are best attributed to isotopic fractionation induced by Zn–Mg inter-diffusion, supported by the core-to-rim increase of Zn contents and decline of Mg contents in zoned oxides. Our results thus suggest that inter-diffusion between Mg and Zn can occur during crystal growth and reaction with host magmas, which is commonly observed between Mg and Fe, and this process is accompanied by strong Zn and Mg isotope fractionations. Such fractionations can be utilized to estimate the timescales for the formation of zoned minerals. Numerical simulation yields a short (∼35 days) diffusion interval for the observed Zn and Mg isotopic variations in the investigated oxide crystals, which indicates rapid cooling of the host lavas. Our results also indicate that fractional crystallization of oxides would lead to slight δ66Zn increase and δ26Mg decrease in the residual melts. Such fractionation should be considered while characterizing the Zn and Mg isotopic compositions of evolved magmas with low MgO and Zn contents.

Influence of nano-zinc oxide and fortified rice residue compost on rice productivity, zinc biofortification, zinc use efficiency, soil quality, zinc fractions and profitability in different rice production systems

Transplanted rice (TPR) faces several limitations, including deteriorating soil quality, zinc (Zn) deficiency, low use efficiency of zinc sulfate (ZnSO4), water scarcity and escalating labor costs, which are dictating the shift toward alternate production systems like direct-sown rice (DSR) and aerobic rice (AR). However, this shift affects soil Zn dynamics and Zn availability to crops. This study was conducted to compare the effectiveness of Zn nutrition (ZnSO4 as soil application and zinc oxide nanoparticles (ZnO NPs) as seed priming alone or with foliar spray) and fortified organic manures (farm yard manure and rice residue) on the rice productivity, Zn use efficiency, grain biofortification, soil quality, Zn fractions and profitability under TPR, DSR and AR. The application of ZnO NPs and fortified rice residue compost significantly improved the yield traits (437 productive tillers m−2 and 186 filled grains panicle−1), grain weight (6.27 Mg ha−1), grain Zn fortification (33.41 mg kg−1) and Zn fractions in all rice production systems. The AR was found to be more encouraging in improving soil organic carbon (11.3%), dehydrogenase activity (21.96%), microbial biomass carbon (17.31%) and DTPA-Zn (10.57%) than TPR and DSR. ZnO NPs seed priming and fortified rice residue resulted in superior zinc use efficiency in both TPR and DSR. The maximum benefit-cost ratio was obtained in DSR with ZnO NPs and fortified rice residue compost. Altogether, DSR with seed priming and foliar spraying of ZnO NPs and fortified rice residue can be a more efficient way to enhance rice productivity, grain Zn fortification and profitability.

Assessment of trace element content throughout the white shrimp (Litopenaeus vannamei) farming cycle

Environmental context Intensive aquaculture is the main source of fisheries products. Thus, investigating the food safety of these products and the environmental impacts of the farms on mangroves is necessary. A shrimp productive cycle was evaluated with a focus on trace element accumulation in shrimps and effluent. The results revealed secure levels of elements in the final product; however, the effluent produced in farms is an important source of contamination to mangrove environment. Rationale Aquaculture systems have increased in the last years due to the high demand for seafood consumption, this could impact the environment and subject fisheries to accumulation of toxic elements. To understand some parameters of food safety and environmental impact, the present study evaluated the concentration of trace elements (Al, As, Cd, Co, Cr, Cu, Mn, Mo, Pb, Se, V and Zn) throughout the production cycle of shrimp. Methodology About 50 shrimps per cycle were collected in a shrimp farm in Brazil and their trace element contents were determined by inductively coupled plasma–tandem mass spectrometry (ICP-MS/MS) and microwave-induced plasma–optical emission spectroscopy (MIP-OES). Results At their final lifecycle stage, shrimp samples present a content (mg g−1) of elements following the trend: Cu (102 ± 12) &gt; Al (20.06 ± 4.24) &gt; Zn (14.82 ± 2.46) &gt; Mn (6.24 ± 0.94) &gt; As (2.65 ± 0.42) &gt; Se (0.932 ± 0.140) &gt; Co (0.380 ± 0.05) &gt; Mo (0.254 ± 0.03) &gt; V (0.204 ± 0.02). Discussion The content of Cd and Pb are in allowance with Brazil and USA legislation for crustaceans, however, the content of As is 3–4-fold higher than that allowed by guidelines in all stages of the growth of the shrimp. The final effluent of the shrimp’s pond into the mangroves shows a high mass fraction of Zn and Mn that could be a source of contamination. Some correlations between some elements in the shrimp samples were found, such as As–Se, Se–Co and Se–V. This study was a scoping experiment to study the content of trace elements throughout the farming cycle of shrimps, encouraging the researcher to undergo a wide survey to evaluate the environmental impact of aquaculture shrimp farming.

Pig manure biochar for contaminated soil management: nutrient release, toxic metal immobilization, and Chinese cabbage cultivation

Pig manure could be an effective fertilizer source for soil, but with high concentrations of xic elements. It has been shown that the pyrolysis method could largely reduce the environmental risk of pig manure. However, the comprehensive analysis of both toxic metals immobilization effect and environmental risk of pig manure biochar applied as a soil amendment is rarely addressed. To address the knowledge gap, this study was carried out with pig manure (PM) and pig manure biochar (PMB). The PM was pyrolyzed at 450 ℃ and 700 ℃, the corresponding biochar was abbreviated as PMB450 and PMB700, respectively. The PM and PMB were applied in a pot experiment growing Chinese cabbage (Brassica rape L. ssp. Pekinensis) with clay-loam paddy soil. The application rates of PM were set at 0.5% (S), 2% (L), 4% (M) and 6% (H). With the equivalent mass principle, PMB450 and PMB700 were applied at 0.23% (S), 0.92% (L), 1.84% (M), 2.76% (H), and 0.192% (S), 0.7% (L), 1.4% (M), 2.1% (H), respectively. Parameters of Chinese cabbage biomass and quality, total and available concentrations of toxic metals in soil, and soil chemical properties were systemically measured. The main results of this study showed that compared with PM, PMB700 was more effective than PMB450, which induced the highest reductions of Cu, Zn, Pb, and Cd contents in cabbage by 62.6%, 73.0%, 43.9%, and 74.3%, respectively. Both PM and PMB increased the total contents of metals (Cu, Zn, Pb, and Cd) in soil, and PMB decreased the mobility of Cu, Zn, Pb, and Cd at high application rates (≥2%). Treatment with H-PMB700 reduced CaCl2 extractable Cu, Zn, Pb, and Cd by 70.0%, 71.6%, 23.3%, and 15.9%, respectively. For Cu, Zn, Pb, and Cd fractions with BCR extraction, PMB treatments, especially PMB700, were more effective than PM in decreasing the available fractions (F1 +F2 +F3) at high application rates (≥2%). Overall, pyrolysis with high temperature (e.g., 700 ℃) could significantly stabilize the toxic elements in PM and enhance PM’s effect on toxic metals immobilization. The marked effects of PMB700 on toxic metal immobilization and cabbage quality improvement might be attributed to high ash contents and liming effect.

Emission Characteristics of Tyre Wear Particles from Light-Duty Vehicles

Tyre wear particle emissions have gained significant attention due to their harmful effects on the environment and human health. However, studies on tyre wear particles generated under chassis dynamometer conditions are still scarce. This study measures the instantaneous number concentrations and elemental species of tyre wear particles in different light-duty vehicle test cycles. The results show that the particle number (PN) concentrations of the US06 test cycle are much higher than those of the WLTC test cycle due to the larger and more frequent accelerations and decelerations in the former. High PN concentrations are observed during high driving speeds with rapid accelerations, while PN concentrations are much lower during low driving speed with rapid acceleration. Furthermore, tyre tread temperature is found to be related to the formation of tyre wear particles. The PN concentration in the second and third US06 test cycles are similar, indicating that once the tyre temperature exceeds the critical value, the tyres become heated to a steady state, and the PN concentrations will not be affected by the average temperature of the tyre. A low initial tyre temperature can produce high PN concentrations during the cold start phase of test cycles and prolong the time required for tyres to warm up. In addition, the particles contained a high mass fraction of Zn, which can serve as a tracer of tyre wear particles in non-exhaust particle tests of vehicles.

Shock-induced potassium and zinc isotope fractionation in ordinary chondrites and its implications

To constrain how impacts influence the behavior of moderately volatile elements (MVEs), we report potassium (K) and zinc (Zn) contents and isotopic compositions of shock melt pockets (SMPs) and unmelted parts of three heavily shocked ordinary chondrites and bulk rocks of Chelyabinsk meteorite. All SMPs are enriched in K content and have lower isotopic values (δ41K = −1.99‰, −1.22‰ and −1.40‰) while the adjacent unmelted parts are enriched in heavy K isotopes (δ41K = −0.41‰, −0.01‰ and 0.04‰) compared to the bulk rocks of Chelyabinsk meteorite (δ41K = −0.77‰ and −0.73‰). By contrast, Zn is depleted in SMPs and the isotopic compositions are heavier (δ66Zn = −0.19‰, 2.42‰, 1.74‰) in SMPs than that in unmelted parts (δ66Zn = −0.65‰, 1.76‰, −0.97‰). Our results indicate a decoupling between the two MVEs that Zn is lost from shock melts while K is dramatically enriched in shock melts during impacts. The isotope fractionation of Zn is probably caused by evaporation of shock melts, while K isotope fractionation is most likely caused by solid-melt diffusion which is controlled by its incompatibility. The isotopic decoupling of K from Zn during major impacts further enhances our understanding of high temperature elemental and isotopic behavior of MVEs and may shed new light on the variously heterogeneous distribution of MVEs in solar system.

Geochemical speciation, ecological risk, and source identification of heavy metal(loid)s in sediments and waters from Musa Estuary, Persian Gulf

Surface sediment and water samples from 12 stations were collected from Musa Estuary. Metals concentrations (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sb, and Zn) were analyzed by ICP-MS. The highest contribution to ecological risk belonged to Cd (49 %) based on the PERI index. The Tessier procedure showed that with increasing contamination, exchangeable and carbonate fractions of Cd, Pb, Ni, Zn, and Cu increased by 25 %, 18 %, 17 %, 10 %, and 9 %, respectively. Cadmium and Pb have a high risk of release according to mobility factor (30 < MF < 50) and individual contamination factor (3 < ICF < 6) indices. Cluster analysis revealed that Al-Fe-Co-V-Mn-Cu-Pb derived from lithogenic resources, while As-Cd-Ni-Zn-Cr originated from anthropogenic sources. The adsorption of Co, Ni, V, and Zn to sediments was strongly influenced by Eh/pH, DOC/temperature, and salinity (r > 0.79, r < −0.78, and r < −0.69; p < 0.01).

Geochemical controls on the distribution and bioavailability of heavy metals in sediments from Yangtze River to the East China Sea: Assessed by sequential extraction versus diffusive gradients in thin-films (DGT) technique

This study conducted a comprehensive investigation on the distribution and bioavailability of heavy metals (Cr, Co, Ni, Cu, Zn, Cd and Pb) in sediments along two typical transects from Yangtze River to the East China Sea continental shelf that spanning large physicochemical gradients. Heavy metals were mainly associated with the fine-grained sediments (enriched with organic matter), exhibiting decreasing trends from nearshore to offshore sites. The turbidity maximum zone showed the highest metal concentrations, which evaluated as polluted for some tested metals (especially Cd) using the geo-accumulation index. Based on the modified BCR procedure, the non-residual fractions of Cu, Zn and Pb were higher within the turbidity maximum zone, and significantly negatively correlated with bottom water salinity. The DGT-labile metals all positively correlated with the acid-soluble metal fraction (especially for Cd, Zn and Cr), and negatively correlated with salinity (except Co). Therefore, our results suggest salinity as the key factor controlling metal bioavailability, which could further modulate metal diffusive fluxes at the sediment-water interface. Considering that DGT probes could readily capture the bioavailable metal fractions, and reflect the impacts of salinity, we suggest DGT technique can be used as a robust predictor for metal bioavailability and mobility in estuary sediments.

Combining ultrafiltration and diffusive gradients in thin films techniques for speciation/fractionation of Cu and Zn in cytosol of liver of Nile tilapia (Oreochromis niloticus).

This work aims to evaluate the size and lability of Cu and Zn bound to proteins in the cytosol of fish liver of Oreochromis niloticus by employing solid-phase extraction (SPE), diffusive gradients in thin films (DGT), and ultrafiltration (UF). SPE was carried out using Chelex-100. DGT containing Chelex-100 as binding agent was employed. Analyte concentrations were determined by ICP-MS. Total Cu and Zn concentrations in cytosol (1g of fish liver in 5ml of Tris-HCl) ranged from 39.6 to 44.3ng ml-1 and 1498 to 2106ng ml-1, respectively. Data from UF (10-30kDa) suggested that Cu and Zn in cytosol were associated with ∼70% and 95%, respectively, with high-molecular-weight proteins. Cu-metallothionein was not selectively detected (although 28% of Cu was associated with low-molecular-weight proteins). However, information about the specific proteins in the cytosol will require coupling UF with organic mass spectrometry. Data from SPE showed the presence of labile Cu species of ∼17%, while the fraction of labile Zn species was >55%. However, data from DGT suggested a fraction of labile Cu species only of 7% and a labile Zn fraction of 5%. This data, as compared with previous data from literature, suggests that the DGT technique gave a more plausible estimation of the labile pool of Zn and Cu in cytosol. The combination of results from UF and DGT is capable of contributing to the knowledge about the labile and low-molecular pool of Cu and Zn.

Site-specific isotope fractionation during Zn adsorption onto birnessite: Insights from X-ray absorption spectroscopy, density functional theory and surface complexation modeling

Birnessite minerals help control the fate of Zn in surface environments and readily fractionate Zn isotopes through adsorption reactions, yet little is known about the role played by various reactive sites in stable isotopic fractionation. Here we present the Zn isotope fractionation data cause by adsorption on birnessite under different reaction times, pH values, and Zn concentrations. We observe that isotopic equilibrium of Zn is attained after ∼120 h of reaction time at pH 6. At pH 3–5 and Zn concentrations of 0.05–0.3 mM, the isotopic fractionation (Δ66Znadsorbed-aqueous) is around −0.46 ± 0.04‰, and gradually increases to −0.09 ± 0.05‰ at pH 6–8 and Zn concentrations of 0.2 mM. The change in Zn isotopic compositions as a function of pH and Zn concentration is well described using the surface complexation model, where two binding sites are involved: external edge sites and interlayer vacancies. According to this model, two different isotopic fractionation factors of Zn are calculated: Δ66Znadsorbed-aqueous = −0.46 ± 0.04‰ for adsorption on vacancy sites and Δ66Znadsorbed-aqueous = 0.52 ± 0.04‰ for binding to edge sites. Extended X-ray absorption fine structure spectroscopy (EXAFS) demonstrates that Zn forms triple-corner-sharing (TCS) octahedral complex on birnessite vacancies at pH 3 and Zn concentrations of 0.05–0.2 mM, where Zn is coordinated on one side to three oxygen atoms of the Mn vacancy (∼2.03 Å) and to three water molecules on the other side (∼2.15 Å), suggesting the formation of distorted ZnO octahedra (average bond length: ∼2.09 Å). At pH 6 and 8, double-corner-sharing (DCS) complexes on layer edges formed in addition to the TCS octahedral complex on vacancies. Density functional theory (DFT) optimisations suggest that DCS Zn complex exist in tetrahedral coordination. Based on EXAFS spectroscopy, DFT optimisations and surface complexation modeling, the distinct isotopic fractionation of Zn is related to the differences in Zn local structure at different reactive sites of birnessite. Our results provide a molecular-scale understanding of Zn isotopic fractionation in natural birnessite-containing settings, as well as new insights into predicting the links between adsorption and fractionation of other similar metals.