Fractions Of Zn Research Articles

Isotopic fractionation of Zn during soil sorption as influenced by soil properties and the Zn–O bond distance: Insights from EXAFS and MC-ICP-MS

Compared to some of the other heavy metals (such as cadmium and lead), zinc (Zn) is a vital trace element for humans and plants but toxic at high concentrations. Stable Zn isotopic techniques have been used to trace the sources of Zn in soils over the past decade. However, sorption processes after Zn enters soil may result in additional isotopic fractionation. This could change the Zn isotopic ratio and result in poor assessment and mismanagement of Zn pollution when using this technique. Different soil properties may have an influence on the Zn sorption process in soils. In this study, we explored the Zn isotopic fractionation in 29 soil samples with different properties (including Zn content, pH, texture, particle size, cation exchange capacity, etc.) using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Results of path analysis showed that the differences in the Zn isotopic fractionation of different soils mainly arose from the direct effects of Alox, Mnox, and clay, as well as the indirect effects of pH and soil organic matter. Extended X-ray absorption fine structure (EXAFS) analysis showed a positive correlation between Zn isotopic fractionation and the Zn–O bond distance, which conformed to the theory that fractionation factor varies according to bond strength. The results of this study show that different soil properties have varying degrees of impact on Zn isotopic fractionation. And the difference in fractionation can be largely explained by binding conditions of Zn in soils.

Accumulation of Co, Ni, Cu, Zn and Cd in Aboveground Organs of Chinese Winter Jujube from the Yellow River Delta, China.

In the present study, winter jujube organs including fruit, fruiting leaf and foliage leaf, and associated soils in 14 typical orchards in Binzhou City, Shandong Province, China were collected and determined for the mass fractions of Co, Ni, Cu, Zn, and Cd. The mass fractions of Co, Ni, Cu, Zn, and Cd in plant tissues generally showed an order of Cu > Zn > Ni > Co > Cd as well as those in the soils decreased as Zn > Cu > Ni > Co > Cd. The values of single factor index and Nemerow pollution index suggested the jujube fruits were not polluted by heavy metals. Values of estimated daily intake for all the elements were far below their associated acceptable reference values, indicating no health risks would be caused by a single trace element. The results of targeted hazard quotient (THQ) of the metals in the fruits decreased as Cu > Ni > Zn > Cd accompanying total THQ (TTHQ) lower than 1 showing no hazard would be caused by those metals. Correlation analysis showed soil might not be the main source of heavy metals in winter jujube organs. Bioaccumulation factors (BAFs) for Co, Ni, Zn and Cd in fruits and leaves were far below 1 suggesting their low bioavailablities. The relatively great BAFs of Cu in the leaves might be due to the application of fertilizers and pesticides containing great amounts of Cu through soil and foliar spraying. To sum up, heavy metals tended not to be a major threat to winter jujube cultivation, and winter jujube had great edible safety.

Co-hydrothermal carbonization of sewage sludge and swine manure: Hydrochar properties and heavy metal chemical speciation

Alleviating the risk of heavy metals while improving fuel properties is one of the important challenges of sewage sludge (SS) disposal. In this work, ferric chloride (FeCl3) was chosen as a typical additive (0.005–0.02 mol) to analyse its effect on the co-hydrothermal carbonation (co-HTC) of SS and swine manure (SM). During co-HTC, SS was converted into hydrochar with SM at different mixing ratio (30–70 %) at 230 °C. Chemical speciation of heavy metals (HMs) in hydrochars, along with fuel properties, were evaluated. The results showed that co-HTC was beneficial for the decline of weakly fractions of Cr, Ni, Mn, and Zn. Furthermore, FeCl3 further decreased the risk of Mn and Zn without significantly expanding the pollution of Ni. More importantly, the risk of Cu was dramatically alleviated by the addition of 0.02 mol FeCl3. Compared with the hydrochar produced from SS, the fuel ratio, higher heating values (9.75–13.09 MJ/kg), and combustion behavior of the hydrochar derived from co-HTC were upgraded and improved. The FeCl3 could notably promoted the dehydration and decarboxylation reaction and prevented the reservation of N content. This study suggested that co-HTC with FeCl3 was a promising strategy to produce superior solid fuel with lower risk of HMs.

In vitro bioaccessibility of essential minerals from raw and cooked Tilapia fillet: Method validation and analysis by synchronous vertical dual view ICP OES

A novel insight into the nutritional changes of Tilapia fillets due to heat treatments was provided by evaluating the influence of baking and air-frying on the total mass fraction and bioaccessibility of micronutrients Ca, Cu, Fe, K, Mg, P, S and Zn. A static in vitro model was used to simulate the human gastrointestinal digestion and then quantify the analytes using inductively coupled plasma optical emission spectrometry with a synchronous vertical dual view system (SVDV ICP OES). Unlike recent studies focusing on the mineral content of cooked foods, we interpreted the results more accurately by considering the weight yield factors. Compared with the raw sample, the baking and air-frying procedures significantly increased the total mass fraction of Fe. Air-frying promoted a slight decrease in Zn content. Bioaccessibility results ranged from 12–31% to 86–88% for Zn and K, respectively. Both heat treatments appear to increase the bioaccessibility of Mg, Fe, and Zn, whereas the other evaluated micronutrients were not remarkably affected by cooking. In addition, the SVDV mode was an efficient instrumental strategy for determination of total, bioaccessible, and non-bioaccessible fractions of essential minerals in Tilapia, improving the sample throughput.

Enhancement of heavy metal immobilization in sewage sludge biochar by combining alkaline hydrothermal treatment and pyrolysis

Heavy metals, including Cd, As, Ni, Cu, Pb, Cr, Zn, and Mn in sewage sludge (SS) are among the greatest impediments to SS application because of their potential toxicity to living organisms and latent environmental pollution risks. In this study, hydrothermal treatment (HT)/alkaline HT combined with pyrolysis was used to treat SS for heavy metal immobilization. The heavy metal characteristics, including total, fraction, and leaching concentrations and potential ecological risks, were comprehensively investigated to ensure the safe application of biochar. The results showed that the heavy metals mainly remained in the hydrochar and biochar. Additionally, both HT and alkaline HT promoted the residual fractions of Cr, Zn, Ni, and Cu in biochar. Furthermore, alkaline HT-aided pyrolysis was more effective for immobilizing Zn and Ni with their residual fractions increasing by 100% and 60% respectively, compared with direct sludge pyrolysis. Moreover, the ecological risk of heavy metals in SS significantly decreased from 57.27 to 30.05 after alkaline HT-combined pyrolysis treatment, contributing to the low potential ecological risk of SS-based biochar. This study provides a promising strategy for converting SS to biochar with improved heavy metal immobilization.

Dewatering municipal wastewater sludge using electro-coagulation combined with added free nitrous acid

An electro-coagulation (EC) process combined with added free nitrous acid (FNA) improves sludge dewaterability. Under optimal conditions(EC voltage of 25 V, EC process time of 60 min, FNA dosage of 1.13 mg/L, pH value of 4.5), specific resistance to filtration (SRF) and water content (WC) was decreased by 89.57%, and 18.90%respectively. The EC process disrupted the sludge structure, reducing sludge particles’ size (D50) from 59.5 to 50.5 μm. After adding FNA, the sludge cells lysed, and the DNA concentrations and soluble chemical oxygen demand (SCOD) increased from 6.07 μg/ml and 29 mg/L to 364 μg/ml and 588 mg/L, respectively. The conversion of Fe(II) to Fe(III) was enhanced. The addition of FNA after EC further improved the sludge dewaterability. Combined conditioning using EC and FNA can effectively destroy tightly bound extracellular polymeric substances (TB-EPS) and release bound water. In addition, the pH value is kept low, which benefits sludge dewaterability and the removal of heavy metals. The concentrations of Zn and Mn in the sludge cake were reduced by 92.3% and 69.0%, respectively. The Bureau of Reference (BCR) sequential extraction method showed increases in the percentages of the residual fractions of Zn and Mn, showing that EC combined with FNA is an efficient and versatile means of sludge conditioning.

Zinc dynamics and yield sustainability in relation to Zn application under maize-wheat cropping on Typic Hapludalfs

Globally, widespread micronutrient deficiencies have become a serious challenge for sustaining crop production systems and food security. Of all micronutrients, zinc (Zn) is the most deficient one. Hence, efficient Zn management is essential to achieve potential crop yields. A six-year field experiment was conducted on Typic Hapludalfs with maize-wheat cropping system to study the direct and residual Zn management effect on maize and succeeding wheat crop, respectively. The effect on soil available Zn was also evaluated. Three Zn application frequencies, viz. once (single year), alternate (every alternate year), and continuous (every year) at four Zn application rates, viz. 2.5, 5.0, 7.5, and 10.0 kg ha −1 along with one control (no Zn) were investigated from 2013 to 2019. The Zn application significantly improved the crop yields, system sustainability, DTPA-Zn, and different Zn pools without causing any environmental risk. In general, the continuous application of Zn at 5.0 kg ha −1 produced the best yield and system productivity. The economically optimal system productivity was obtained with 5.93 and 7.46 kg Zn ha −1 for alternate and continuous frequency Zn application, respectively. The optimal DTPA-Zn to attain the highest system productivity of 7.64 t ha −1 was 1.55 mg kg −1 . The crop yields were mainly influenced by the alternate and continuous application of Zn at lower rates (2.5, 5.0, and 7.5 kg ha −1 ), whereas Zn fractions and DTPA-Zn were significantly influenced by Zn application at higher rate (10 kg ha −1 ) irrespective of Zn application frequencies. Similar results were obtained with PCA analysis. The results of this study suggested the rationality of Zn application in attaining economically viable and environmentally sound maize-wheat system productivity.

Effect of losartan potassium, metformin hydrochloride, and simvastatin on in vitro bioaccessibility of Cu, Fe, Mn, and Zn in oat flour from Brazil

BackgroundThe simultaneous administration of drugs with food can compromise the bioaccessibility and absorption of nutrients. The objective of this study was to evaluate the influence of the use of losartan potassium (LP), metformin hydrochloride (MH), and simvastatin (S) on the in vitro bioaccessibility of micronutrients (Cu, Fe, Mn, and Zn) in oat flour from Bahia, Brazil. MethodsThe experimental procedure consisted of the in vitro extraction of the bioaccessible fraction of Cu, Fe, Mn, and Zn in oat flour—with and without LP (50 mg), MH (500 mg), and S (20 mg)—using the unified bioaccessibility method (UBM), simulating the conditions of the gastrointestinal tract. For decomposition of the samples (oat flour and residue), a digester block with a closed system was used. To determine the total content (flour and residual fraction) and bioaccessible micronutrients, inductively coupled plasma optical emission spectrometry (ICP OES) was used. ResultsThe bioaccessible contents (µg g-1) without the addition of drugs were: Cu 5.86 ± 0.21, Fe 32.80 ± 1.32, Mn 87.90 ± 1.90, and Zn 30.33 ± 2.05, with bioaccessibility ranging from 31.5 % for Fe to 99 % for Mn. The in vitro extraction method was validated by mass balance with recovery values from 89.78 % for Cu to 101.94 % for Mn. The range of bioaccessible contents (µg g-1) were: Cu (<4.14), Fe (32.10 ± 0.20–54.10 ± 2.03), Mn (81.40 ± 0.93–93.22 ± 0.80), and Zn (<10.80–29.11 ± 2.20). The estimation of the bioaccessibility of Cu, Mn, and Zn in oat flour were compromised in the presence of LP, MH, and S (p < 0.05). ConclusionChemical interactions can occur between drugs and micronutrients. Taken together, our results highlight that LP, MH, and S can interfere with the bioaccessibility of Cu, Fe, Mn, and Zn in oat flour in patients who use these drugs, suggesting its rational use in further investigations.

Fluidized bed gasification of biomass from plant-assisted bioremediation: Fate of contaminants

Fluidized-bed gasification (FBG) of Phyto-assisted Bioremediation (PABR) biomass is analyzed focusing on the contaminants’ dispersion. Poplar pruning coming from an area contaminated by polychlorinated biphenyls (PCBs) and heavy metals (HM) are considered. The biomass analysis showed relevant contents in HMs, especially Cd and Cr, and no significant PCB content. FBG process was analyzed to: a) track pollutants, b) detect contaminants in the FBG and c) investigate the HMs concentration in the produced streams. The results showed that most of the metals are concentrated in the ashes collected in the bottom of the reactor (Pb, Cd, Cu, Cr), or in the cyclone (B, Na, Mg, Al, K and Fe). Interestingly, metals are also released by the olivine bed (Mg, Fe, Ni and Al) and transported downstream. Consistent fractions of Zn and Fe (also Cu) were detected in the fugitive ashes. As for the Volatile Organic Compounds (VOC) concentration, we noted similarities between PABR and virgin biomass syngas streams. A reduced-scale process was carried out in TGA-DTA to investigate the potential of such technique in reproducing the main features of the FBG process. Comparable results were obtained, thus suggesting its possible application for small-scale preliminary assessment of FBG process.

Fractionation analysis and risk assessment of potential toxic elements in reservoir sediments in central China.

The pollution of potential toxic elements (PTEs) in the environment is a persistent issue and draws public attention constantly. However, there is no study comprehensively assessing the PTE pollution of water supply reservoirs in central China. This study determined the total contents and fractions of seven PTEs in 10 water supply reservoirs of central China, and evaluated PTE pollution risks by adopting various models. The results indicated that PTE pollution in water supply reservoirs was lower comparing that in estuary or river sediments, and Mn (manganese) was the predominant PTE in central China reservoirs. Fractionation analysis revealed that for B1 fraction (exchangeable/acid-soluble fraction) of Mn, Zn (zinc) and B2 fraction (reducible fraction) of Pb (lead) was high, while the effective state portion of Cr (chromium) was small. The monomial potential ecological risk indices and Igeo values were low among most samples, indicating overall modest PTE pollution. However, the results of the individual contamination factor (ICF) suggested that Pb might lead to potential health risks to human beings.

Effect of superphosphate addition on heavy metals speciation and microbial communities during composting

Superphosphate fertilizer (SSP) as an additive can reduce the nitrogen loss and increase available phosphorus in composting but few studies investigated the effect of SSP addition on heavy metal and microbial communities. In this study, different ratios (10%, 18%, 26%) of SSP were added into pig manure composting to assess the changes of heavy metal (Cu, Mn, As, Zn, and Fe) fractions, bacterial and fungal communities as well as their interactions. SSP addition at 18% had lower ecological risk but still increased the bioavailability of Cu, Mn, and Fe in composts compared to control. Adding 18% SSP into compost decreased bacterial number and increased the fungal diversity compared to CK. Redundancy analysis indicated heavy metal fractions correlated significantly with bacterial and fungal community compositions in composting with 18% SSP. Network analysis showed adding 18% SSP increased microbial interaction and positive cooperation especially enhanced the proportion of Proteobacteria and Ascomycota.

Reference Materials for the Activity Concentration of Technogenic Radionuclides and the Mass Fraction of Elements Based on the Soil Matrix of the Semipalatinsk Test Site

The application of reference materials for the composition and properties of natural objects with certified characteristics is the main instrument for ensuring the correctness of the obtained analytical information in radioecological, geological, and other studies. The article presents the experience of the branch of the Institute of Radiation Safety and Ecology of the National Nuclear Center of the Republic of Kazakhstan in the development and certification of reference materials containing technogenic radionuclides and mass fractions of elements. The soil selected from the sites of underground and surface nuclear tests at the «Experimental field» and «Balapan» sites of the former Semipalatinsk Test Site, which has a diverse radionuclide composition (natural and technogenic radionuclides) with a wide range of chemical elements, was chosen as the starting material for production of reference materials. The main purpose of the work is the certification of two reference materials: reference material for the activity concentration of 137Cs, 90Sr, the mass fraction of Zn, Cu, Pb, Cd, Co, Fe, Mn, As in the soil cover of the Semipalatinsk Test Site (KZ.04.01.00007–2020) and reference material for the activity concentration of 152Eu, 60Co, the mass fraction of Zn, Cu, Pb, Cd, Co, Fe, Mn, As in the soil cover of the Semipalatinsk Test Site (KZ.04.01.00008–2020).All procedures necessary for the creation of reference materials were carried out: separation of the magnetic fraction from the bulk of the material, grinding of the material, control sieve of the material, as well as homogenization with subsequent analytical studies to certify the parameters of reference materials. The methods of gamma spectrometry, beta spectrometry, mass spectrometry, and combined measurement results processing were applied. The results of an interlaboratory comparative test to determine the certified value of the concentrations of the specified radionuclides and elements are given.Reference materials are soil samples dried to an air-dry state, grinded to a particle size of less than 60 µm, and packaged in hermetically sealed polypropylene containers weighing 200 g. Reference materials have been included in the register of the state system for ensuring the uniformity of measurements and approved as state reference materials of the Republic of Kazakhstan. The scope of reference materials is to provide interlaboratory quality control of tests of analytical laboratories specialized in conducting radioecological complex studies, as well as the development and validation of analytical measurement procedures.

The zinc isotope composition of late Holocene open-ocean marine sediments

The controls on Zn burial fluxes into marine sediments are not well constrained by existing datasets. To address this problem, new Zn-isotope data have been generated from a globally distributed array of late-Holocene age sediments that accumulated in open ocean settings underneath a diverse range of depositional conditions (Namibian margin, West African margin, Arabian margin, Californian margin, Peruvian margin, Southern Ocean, Indian Ocean, North and South Atlantic Oceans, South China Sea). The mean non-detrital isotopic composition of Zn in the whole dataset (δ66/64Zn = 0.37 ± 0.25 ‰, 2. S.D., n = 33) is only slightly lower than the modern deep-ocean composition (0.45 ± 0.14 ‰). Locations with total organic carbon >1 wt% have greater non-detrital enrichments of Zn and higher Zn isotope compositions than organic-poor sites, although the uncertainties overlap. Zinc associated with organic matter burial (using Zn/C ratios) and/or oxyhydroxide burial (using Zn/Fe and Zn/Mn ratios) account for a combined total of ~16–73% of the total non-detrital Zn content of the investigated sediments, therefore requiring an additional burial flux of Zn to balance the sedimentary budget. This flux is probably related to ZnS formation although Zn incorporation into authigenic clays is also possible. The new data indicate that open-ocean marine sediments track the deep-ocean Zn isotope composition to within 0.1–0.2 ‰, except in areas where isotopically distinct Zn fractions dominate the non-detrital Zn budget. The fraction of Zn removed into different sedimentary components is used to calculate Zn residence times ranging from ~2.7 kyr to 13.5 kyr that are within the range of previous estimates based on input fluxes to the ocean.

Relationship of Selected Soil Properties with the Micronutrients in Salt-Affected Soils

The present study aimed to assess the relationship of soil properties in salt-affected soils. The soil samples were collected from 14 districts of Pakistan. Soil salinity and sodicity are the common features of the arid and semiarid regions. The effects of the salt’s interactions with soil micronutrients have not been well studied. Therefore, saline and non-saline soil samples were collected from different locations. The microelements (Fe, Cu, Mn, and Zn) were fractionated into water-soluble, exchangeable, carbonate, Fe + Mn oxide, organic, and residual fractions. Univariate and multivariate analysis (PCA) was carried out to determine the linear relationship between soil properties and micronutrients fractions. Results showed that the magnitude of micronutrients appeared to be affected by the salinity in soils. In saline soil, the Fe fractions differed in the order of residual &gt; organic bound &gt; Fe + Mn bound &gt; carbonate bound &gt; exchangeable &gt; water soluble. Iron fractions varied in the non-saline soils as residual &gt; Fe + Mn bound &gt; organic bound &gt; exchangeable &gt; carbonate bound &gt; water soluble. Copper concentration was higher in the residual and carbonate forms, and the amount was lower in the exchangeable and water-soluble forms under both saline and non-saline conditions. The water-soluble Mn fraction was lower, and the residual Mn fraction was proportionately higher than other forms of Mn in soils. Zinc was found mostly in the residual fraction in both saline and non-saline soils. The mobility factor of micronutrients in non-saline soil was greater than in saline soil. PCA revealed that organic matter (OM) and pH directly affected the fractionation of Cu, Mn, Zn, and Fe in soil. Thus, it could be inferred that salts can bring changes to the composition of micronutrients depending on the nature of the soil and the magnitude of salts.

Corn processing, flake density, and starch retrogradation influence ruminal solubility of starch, fiber, protein, and minerals.

Five ruminally cannulated steers (body weight = 390 ± 7.86 kg) were used in three experiments to evaluate effects of corn processing, flake density, and starch retrogradation on in situ ruminal degradation. In experiment 1, corn was left whole or processed with no screen, ground through a 6-mm screen, or ground through a 1-mm screen. In experiment 2, we produced steam-flaked corn at four densities: 309, 335, 360, and 386 g/L. These four flake densities were sifted for 20 s through a 4-mm screen to produce two particle sizes within each flake density: sifted flakes (>4 mm) and sifted fines (<4 mm). In experiment 3, sifted flakes (335 g/L) were stored for 3-d at either 23 °C (starch availability = 55%) or 55 °C to induce starch retrogradation (starch availability = 41%). All samples for each of the three experiments were weighed into nylon bags and ruminally incubated for 0-h to estimate the soluble fraction. The residue remaining was analyzed for nutrient composition. In experiment 1, whole shelled corn had lesser (P < 0.01) ruminal solubility of all nutrients measured compared with ground corn. Corn ground with a screen (6 and 1 mm) had greater (P < 0.01) ruminal solubility of all nutrients measured compared with corn ground with no screen. Corn ground through a 1-mm screen had greater (P < 0.03) ruminal solubility of DM, total starch, CP, ADF, AHF, P, Mg, K, S, Zn, Fe, and Mn compared with corn ground through a 6-mm screen. In experiment 2, increasing flake density linearly decreased (P < 0.02) the soluble fraction of DM, total starch, CP, ADF, AHF, P, K, S, and Zn of sifted flakes. The soluble DM fraction of sifted fines tended to decrease (P = 0.06) linearly with increasing flake density. Total starch, CP, NDF, and Zn soluble fractions of sifted fines were not influenced by flake density. In experiment 3, storage of sifted flakes in heat-sealed foil bags at 55 °C for 3-d decreased (P < 0.04) the soluble fractions of DM, total starch, CP, NDF, P, Mg, K, S, and Fe. With each increase in the degree of corn processing, there was an increase in the solubility of nutrients. Increasing flake density can decrease ruminal solubility of flakes; however, the soluble fraction of sifted fines is not influenced as much by changes in flake density. Inducing starch retrogradation decreases ruminal solubility of starch, nonstarch OM, and minerals.

Processing and mechanical properties of novel biodegradable poly-lactic acid/Zn 3D printed scaffolds for application in tissue regeneration

The feasibility to manufacture scaffolds of poly-lactic acid reinforced with Zn particles by fused filament fabrication is demonstrated for the first time. Filaments of 2.85 mm in diameter of PLA reinforced with different weight fractions of μm-sized Zn - 1 wt.% Mg alloy particles (in the range 3.5 to 17.5 wt.%) were manufactured by a double extrusion method in which standard extrusion is followed by precision extrusion in a filament-maker machine. Filaments with constant diameter, negligible porosity and a homogeneous reinforcement distribution were obtained for Zn weight fractions of up to 10.5%. It was found that the presence of Zn particles led to limited changes in the physico-chemical properties of the PLA that did not affect the window temperature for 3D printing nor the melt flow index. Thus, porous scaffolds could be manufactured by fused filament fabrication at 190 °C with poly-lactic acid/Zn composites containing 3.5 and 7 wt.% of Zn and at 170 °C when the Zn content was 10.5 wt.% with excellent dimensional accuracy and mechanical properties.

Fractionation, Mobility and Environmental Risk of Trace Metals in the Sediments from N’zi River, Côte d’Ivoire

Despite increasing human activities, such as agriculture, little information is available on the status of trace metals contamination in rivers in developing countries including Côte d’Ivoire (West Africa). The aim of this study was study chemical fractions of Cu, Pb, Zn, and Ni, to identify mobility, sources and to evaluate ecological risks of traces metal in sediment of N’zi River using modified BCR sequential extraction procedure. The results showed that all metal were dominated by residual fractions. Labile fractions of Pb accounted for 0.0 – 68% of total contents indicating significant anthropogenic sources for Pb, while for Cu, Ni and Zn results suggesting natural sources. The potential mobility of the metals manifested following order: Ni &gt; Zn &gt; Cu &gt; Pb. Risk assessment code indicated low to medium risk for Pb and low risk for other metals in the sediments.&#x0D; Cluster analysis (CA) and Matrix correlation were used to detect the relationship between the studied sampling sites and to see if some of the parameters interrelated with each trace metal concentration in exchangeable fraction. Results indicated high anthropogenic contamination at stations near to urban and agricultural areas.

One stone two birds: Bone char as a cost-effective material for stabilizing multiple heavy metals in soil and promoting crop growth

Remediation of farmland soils contaminated with high levels of multiple heavy metals near PbZn smeltery is still a great challenge. It is of great significance to find cost-effective green remediation technologies for stabilization of multiple heavy metals in soil and reduce metal accumulation in crops with ensured yield. In this study, we demonstrated that bone char (BC) is an effective heavy metal stabilizer which can substantially increase residual fractions of heavy metals and reduce metal accumulation in pea (Pisum sativum) with its enhanced growth. We chose the soils contaminated with high levels of Pb, Zn, Cu and Cd near the Baiyin PbZn smeltery as the tested soil. After 2 months of BC application, the relative mobile fractions (non-residual fractions) of Cu, Zn, Pb and Cd in the contaminated soil decreased while the residual fraction increased significantly. The leachability of Cu, Zn, Pb and Cd decreased by 91.2%, 38.6%, 67.6% and 54.3%, respectively compared with the control. BC application remarkably promoted pea growth and reduced accumulation of heavy metals in shoots. The mechanisms for stabilization of multiple heavy metals BC include ion exchange, surface complexation and subsequent mineralization, accompanied with release of Ca and phosphate. The immobilization of heavy metals led to their reduced toxicity to plant, and thus increased pea growth. The results show that BC is a cost-effective and sustainable heavy metal stabilizer with phosphate fertilization function. It can simultaneously immobilize multiple heavy metals in soil and facilitate crop production.

Distribution and Fractionation of Zinc and Copper in Poultry Litters Across North Carolina

ABSTRACT Zinc (Zn) and copper (Cu) are necessary micronutrients for crop production. However, excess Zn and Cu applied through land application of manures can result in Zn and Cu toxicity, reducing yields. With many integrators and little information on the formulation of poultry feeds in North Carolina (NC), it is difficult to predict the fractionation of Zn and Cu in litters generated at facilities, as the form of Zn and Cu determines mobility and bioavailability. Therefore, statewide data from the NC Department of Agriculture and Consumer Services was analyzed to determine regional variation of total Zn and Cu. The results showed a significant effect of the region on the total Zn and Cu among the three production regions in the state. Additionally, 11 broilers and broiler breeder litter samples were analyzed to determine the distribution of Zn and Cu in acid soluble, reducible, oxidizable, and residual fractions. Total Zn and Cu averaged 675 mg/kg and 629 mg/kg, respectively. There was a significant interaction between the region and Zn concentration in the fractions. However, there was no region interaction when converted to a percentage of the sum of the fractions, indicating Zn partitions similarly across a wide range of concentrations and 37%, 40%, 21%, and 0.6% was found in the acid soluble, reducible, oxidizable, and residual fractions, respectively. Region did not have an effect on Cu fractionation, with 26%, 8%, 67%, and 2% of Cu in the acid-soluble, reducible, oxidizable, and residual fractions, respectively. Results indicate greater bioavailability and mobility potential for Zn as compared to Cu.

Fungi Can Be More Effective than Bacteria for the Bioremediation of Marine Sediments Highly Contaminated with Heavy Metals.

The contamination of coastal marine sediments with heavy metals (HMs) is a widespread phenomenon that requires effective remediation actions. Bioremediation based on the use of bacteria is an economically and environmentally sustainable effective strategy for reducing HM contamination and/or toxicity in marine sediments. However, information on the efficiency of marine-derived fungi for HM decontamination of marine sediments is still largely lacking, despite evidence of the performance of terrestrial fungal strains on other contaminated matrixes (e.g., soils, freshwater sediments, industrial wastes). Here, we carried out for the first time an array of parallel laboratory experiments by using different combinations of chemical and microbial amendments (including acidophilic autotrophic and heterotrophic bacteria, as well as filamentous marine fungi) for the bioremediation of highly HM-contaminated sediments of the Portman Bay (NW Mediterranean Sea), an area largely affected by long-term historical discharges of mine tailings. Our results indicate that the bioleaching performance of metals from the sediment is based on the addition of fungi (Aspergillus niger and Trichoderma sp.), either alone or in combination with autotrophic bacteria, was higher when compared to other treatments. In particular, fungal addition allowed obtaining bioleaching yields for As eight times higher than those by chemical treatments and double compared with the addition of bacteria alone. Moreover, in our study, the fungal addition was the only treatment allowing effective bioleaching of otherwise not mobile fractions of Zn and Cd, thus overtaking bacterial treatments. We found that the lower the sediment pH reached by the experimental conditions, as in the case of fungal addition, the higher the solubilization yield of metals, suggesting that the specific metabolic features of A. niger and Trichoderma sp. enable lowering sediment pH and enhance HM bioleaching. Overall, our findings indicate that fungi can be more effective than acidophilic autotrophic and heterotrophic bacteria in HM bioleaching, and as such, their use can represent a promising and efficient strategy for the bioremediation of marine sediments highly contaminated with heavy metals.