Soil Zn Fractions Research Articles

Geochemical Interaction and Bioavailability of Zinc in Soil Under Long‐Term Integrated Nutrient Management in Pearl Millet–Wheat System

ABSTRACTThe degree and severity of zinc (Zn) deficiency in soil reduced the agricultural yield and quality, thus encouraging malnutrition in humans worldwide. The study was hypothesized to increase the bioavailability and release of Zn in soil and Zn biofortification in wheat grains under integrated nutrient management (INM). The long‐term (54 years) experiment laid out in a split‐plot design comprising single (W) and dual (PW) applications of farmyard manure (FYM) (0, 5, 10, and 15 Mg ha−1) and nitrogen (0, 60, and 120 kg ha−1) was studied to understand the distribution of different Zn fractions in soil and their relationship to wheat grain yield and Zn uptake. A laboratory incubation study was performed on surface soils to evaluate the release kinetics of native Zn at field capacity. The different fractions of Zn in soil increased with increasing frequency and levels of FYM application. Residual Zn constituted the maximum proportion (89.03%) of total soil Zn. A high positive correlation (p < 0.01) of diethylenetriaminepentaacetic acid (DTPA)‐extractable Zn and total grain Zn content were observed with different Zn fractions. The release kinetics of native soil Zn increased up to 10 days and became almost constant, indicating the establishment of chemical equilibria between the soil solid and solution phase. Thus, long‐term INM ensured higher wheat production (6.08 Mg ha−1) and Zn biofortification (38.95 mg kg−1) to combat Zn malnutrition and achieve the United Nations’ sustainable development goals on “zero hunger” and “good health and well‐being.”

Effect of phosphorus and zinc application on zinc transformation and phyto-availability of zinc fraction in rice soil

Application of high dose of phosphorus (P) changes the soil chemical properties which may lead to redistribution of Zn fractions in soil. A field experiment was conducted to study the effect of added zinc (Zn) and P on Zn transformations in a New Alluvial soil (Aeric Haplaquept), together with dry matter yield and Zn uptake by rice plants. The treatments included four levels of P (0, 40, 60, and 80 kg ha−1) and three levels of Zn (0, 5, and 10 kg ha−1). Although P application increased the dry matter yield of rice, Zn concentration and uptake was decreased significantly at higher dose of P application. Application of P caused a decrease in all the fractions of soil Zn except amorphous and crystalline Fe-oxide bound zinc. The order of preponderance of different zinc fractions followed the order, water soluble plus exchangeable (WE-Zn) < carbonate bound (Car-Zn) < organically bound (Org-Zn) < manganese oxide (MnOx-Zn) < crystalline sesquioxide (CFeOx-Zn) < amorphous sesquioxide (AFeOx-Zn) < residual Zn (Res-Zn). Residual Zn was the most dominant form of Zn, contributing about 69.07% to total Zn. Correlation data indicated that those fractions are in a state of dynamic equilibrium among different fractions and governs the plant-available Zn in soil. Path coefficient analysis of different Zn-fractions with Zn-uptake in rice plant showed that among the all pools of Zn, Org-Zn fraction plays the most vital role in contributing to Zn uptake by plants.

Phasing of Zn Application on Yield, Sustainability Index and Soil Zn Fractions Under a Rice-Rice Cropping System Grown in an Inceptisols

ABSTRACT Presence of Zn deficiency in soils and its subsequent management forms the basis of the present investigation. To find out the optimum dose and frequency of Zn application a field experiment was conducted by taking fou graded doses of Zn applied in phasing through three frequencies upto 5 year to a rice-rice cropping system grown in an Inceptisols of central farm,OUAT,Bhubaneswar,Odisha. Zinc fractionation study was conducted in initial and post harvest soil to address the possible fate of Zn application on various Zn pools and on yield of rice – rice cropping system. Results after five cropping cycles revealed that rice crop responded to Zn application both to increasing dose and frequency of Zn by producing highest mean grain yield of 4.3 t/ha as well as cumulative yield of 21.3 t/ha in the treatment of every year Zn application @ 5 kg/ha with highest gross return of 1.33 per rupee investment. Highest response of 37% over no Zn application was observed in the same treatment. Among the soil Zn pools affected by Zn application was organic and amorphous oxide bound forms. Residual fraction constituted the highest percent of total Zn among all fractions. Nominal increase in DTPA extractable Zn in post harvest soil under every year Zn application was noticed. Hence for rice growing lowland soils of Odisha application of small dose Zn@ 5 kg/ha every year to the first crop of a rice-rice cropping system can produce a sustainable yield upto 5 year without any adverse effect on soil.

Effect of Different Dosages and Frequency of Zinc Application on Yields, Zinc Concentration, and Uptake of Rice-Wheat Rotation and Changes in Soil Chemical Fractions of Zinc

ABSTRACT Under intensive rice-wheat cropping system (RWCS), the information on the optimum Zn dose and frequency of application is needed for sustainable productivity of the system and maintenance of soil fertility. In a 6-year field study carried out on a sandy loam (Typic hapludoll), the effect of different dosages (0, 2.5, 5.0, 7.5, and 10.0 kg Zn ha−1) and frequency of Zn applications (once, alternate year, and every year) were investigated on yield and Zn nutrition of rice-wheat crops and changes in chemical fractions of Zn in soil. Based on the average grain yields of rice and wheat, it was concluded that application of 7.5 kg Zn ha−1 as zinc sulfate heptahydrate to rice in alternate years was the best practice in a typic hapludoll as it resulted in an average production of 5.67 t of rice grain and 4.53 t of wheat grain ha−1. The practice resulted in a benefit:cost ratio of 14.2: 1 and also helped to maintain the optimum level of Zn in soil. Application of Zn markedly increased the residual Zn fraction in soils. The use of medium (5 kg Zn/ha) and high doses (7.5 and 10.0 kg Zn ha−1) in all years brought a significant increase in water soluble + exchangeable, organically bound, and sesquioxide bound fractions of Zn. Soil application of 7.5 kg Zn ha−1 to alternate year rice crop can be recommended under RWCS on typic hapludoll for higher grain yields, profitability, and maintenance of Zn availability.

Impact of ZnSO4 and ZnEDTA applications on wheat Zn biofortification, soil Zn fractions and bacterial community: Significance for public health and agroecological environment

Application of Zn fertilizer can improve cereal Zn concentration, and affect soil microbial ecology by increasing soil Zn concentration. We investigated the effects of three-year continuous applications of different Zn fertilizers (i.e., ZnSO4 and ZnEDTA) on wheat Zn biofortification, soil Zn fractions and bacterial community on a Zn deficient calcareous soil. The results showed that ZnEDTA application induced a higher grain Zn concentration and bioavailability than those in the case of ZnSO4 application, which met the target of wheat Zn biofortification within three years. Correspondingly, ZnEDTA application resulted in a higher Zn availability in soil than ZnSO4 application by facilitating Zn transformation into exchangeable and organic matter loosely bound fractions. Bacterial diversity and richness were not affected, but the bacterial community was altered after three years Zn applications. ZnEDTA application significantly decreased the relative abundances of Nocardioides, Arthrobacter, Blastococcus, Gemmatimonas, and Streptomyces as compared with ZnSO4 application. Meanwhile, ZnEDTA application lowered α-glucosidase, β-glucosidase, and β-xylosidase activities in soil as compared with ZnSO4 application. These results indicated that ZnEDTA application is an effective practice to achieve wheat Zn biofortification, but attention needs to be paid to the potential environmental risks associated with the decreased activities of microbes and enzymes in soil.

The effect of soil properties on zinc lability and solubility in soils of Ethiopia – an isotopic dilution study

Abstract. Zinc (Zn) deficiency is a widespread nutritional problem in human populations, especially in sub-Saharan Africa (SSA). The Zn concentration of crops consumed depends in part on the Zn status of the soil. Improved understanding of factors controlling the phyto-availability of Zn in soils can contribute to potential agronomic interventions to tackle Zn deficiency, but many soil types in SSA are poorly studied. Soil samples (n=475) were collected from a large part of the Amhara Region of Ethiopia, where there is widespread Zn deficiency. Zinc status was quantified by measuring several fractions, including the pseudo-total (aqua regia digestion; ZnTot), available (DTPA (diethylenetriamine pentaacetate) extractable; ZnDTPA), soluble (dissolved in 0.01 M Ca(NO3); ZnSoln) and isotopically exchangeable Zn, using the enriched stable Zn isotope 70Zn (ZnE). Soil geochemical properties were assessed for their influence on Zn lability and solubility. A parameterized geochemical assemblage model (Windermere Humic Aqueous Model – WHAM) was also employed to predict the solid phase fractionation of Zn in tropical soils rather than using sequential chemical extractions. ZnTot ranged from 14.1 to 291 mg kg−1 (median = 100 mg kg−1), whereas ZnDTPA in the majority of soil samples was less than 0.5 mg kg−1, indicating widespread phyto-available Zn deficiency in these soils. The labile fraction of Zn in soil (ZnE as % ZnTot) was low, with median and mean values of 4.7 % and 8.0 %, respectively. Labile Zn partitioning between the solid and the solution phases of soil was highly pH dependent, where 94 % of the variation in the partitioning coefficient of 70Zn was explained by soil pH. Similarly, 86 % of the variation in ZnSoln was explained by soil pH. Zinc distribution between adsorbed ZnE and ZnSoln was controlled by pH. Notably, Zn isotopic exchangeability increased with soil pH. This contrasts with literature on contaminated and urban soils and may arise from covarying factors, such as contrasting soil clay mineralogy across the pH range of the soils used in the current study. These results could be used to improve agronomic interventions to tackle Zn deficiency in SSA.

Zinc fractions and nutrition of maize (Zea mays L.) as affected by Olsen-P levels in soil

Zinc (Zn) deficiency with large phosphorus (P) application for plant nutrition is commonly an investigated antagonistic interaction. However, required P fertilization for optimum grain yield with desirable grain Zn content is a major constraint owing to poor understanding of relationships between P application rates, residual P accumulated in the soil after surplus fertilizer P applications, and soil Zn transformations together with plant Zn uptake. Results showed that the effect of added P fertilizer was more pronounced with decreasing availability of water-soluble and exchangeable (WS), specifically adsorbed (SPAD), Mn-Oxide bound (MnOX), amorphous Fe-oxides (FeOX), and organically bound (OM) zinc fractions in ‘high’ P (22.5–50 kg ha−1) soils than ‘medium’ (12.5–22.5 kg ha−1) and ‘low’ P (< 12.5 kg ha−1) soils. Further, the addition of farmyard manure (FYM) significantly improved the availability of all the soil Zn fractions. Plant Zn uptake decreases with P additions of 39 and 52 kg P ha−1 by 20 and 26% in ‘high’ P soils, 15 and 26% in ‘medium’ P soils, and 6 and 12% in low P soils respectively, indicating higher Olsen-P levels restricts the translocation of Zn from roots to above-ground parts of the plant. Maximum grain Zn content averaging 30 mg kg−1 over three years was observed at Olsen-P level of 21.5 mg kg−1. Path analysis highlighted that extractable OM and MnOX fractions in ‘high’ P soils, WS and FeOX fractions in ‘medium’ P, and WS fractions in low P soils were the most prevalent fractions that contribute towards Zn uptake of maize plants.

Zinc fractions and Barley productivity under zinc fertilization and sodic irrigation water management

An experiment was conducted to know the effect of different residual sodium carbonate (RSC) water, farmyard manure (FYM) and different levels of zinc fertilization on different zinc fractions of soil, yield attributes and yield of barley in loamy sand soil under semi-arid climatic conditions. The three levels of RSC of irrigation water (2.5, 5 and 10 mmol/ L), two levels of FYM (control and 15 t/ha) and four levels of zinc (control, 15, 30 and 45 kg ZnSO4/ha) were evaluated on barley production in split plots design. Results indicated that application of high RSC irrigation water (10 mmol/ L) significantly reduced the different fractions of soil Zn (except Occ-Zn), plant height, total and effective tillers, test weight and yield of barley during both the years, while 5 mmol/L of RSC irrigation level found at par with 2.5 mmol/L. Application of FYM significantly increased the different Zn fractions in soil (except Occluded- Zn) as well as yield attributes, grain and straw yield of barley. The increasing level of zinc application significantly increased the different fractions of soil Zn (except Occ-Zn), available soil Zn, yield attributes and yield of barley. It was observed that the grain yield of barley positive and significantly correlated with different fractions of Zn, viz. DTPA-Zn (r=0.888), Ads-Zn (r=0.525), Occ-Zn (r = 0.670), OC-Zn (r = 0.948) and Res-Zn (r = 0.923). The optimum dose of zinc for barley computed as 37.6 kg / ha ZnSO4 with corresponding optimum yield of 4365 kg/ha.

Combining zinc desorption with EXAFS speciation analysis to understand Zn mobility in mining and smelting affected soils in Minas Gerais, Brazil

Zinc contents exceeding regulatory levels have been documented in several areas in Brazil and elsewhere, especially in sites surrounding mining and smelting sites. Studies involving Zn release and speciation are keys to assess the mobility and bioavailability and thus the potential ecological risk of this element. This study evaluated Zn desorption and speciation from soils affected by mining (soils from a mine area, classified as Technosols) and smelting (mine tailing) activities in Brazil with high total Zn contents, ranging from 1.8 to 8.2%, using a stirred-flow approach and synchrotron-based X-ray absorption spectroscopy (XAS), in order to better assess Zn availability and mobility in these environments. The exchangeable fraction, extracted by 0.1 M CaCl2 solution, represented only a small (<0.5%) portion of the total Zn from soils of the mining site, while accounting for ~80% from tailings of the smelting site. In the mine area, X-ray absorption fine structure (XAFS) showed that Zn was associated with hemimorphite, Zn-ferrihydrite, Zn-phyllosilicates (Zn-kerolite), and Zn-layered double hydroxides (Zn-LDH); this is the first time these Zn precipitate/sorbed forms have been detected in Brazilian mining soils, which have been exposed to tropical conditions. The formation of these insoluble phases of Zn could explain the low Zn desorption from these soils, taking into consideration that Zn-ferrihydrite, Zn-kerolite, and Zn-LDH can lead to a significant decrease of the exchangeable/mobile fraction of Zn in soils. The higher amount of Zn desorbed (⁓80%) from the tailing material located in the smelting site could be attributed to the predominance of weakly bound forms of Zn (~70%). These findings were also seen by analyzing the Fourier Transform (FT) and Wavelet Transform (WT). This study has shown that combining EXAFS analyses with desorption extraction is relevant to better understand Zn mobility and how it is related to Zn speciation.

Field evaluation of Zincated nanoclay polymer composite (ZNCPC): Impact on DTPA-extractable Zn, sequential Zn fractions and apparent Zn recovery under rice rhizosphere

Zinc (Zn) deficiency is a widespread phenomenon globally. Conventional Zn fertilizers (ZnSO4·7H2O) are reported to have very low use efficiency of applied Zn (1–5%). Hence, technological interventions in increasing Zn efficiency are of utmost importance. Keeping in this background, the present investigation was undertaken with the objectives of evaluating ZNCPC (Zincated nanoclay polymer composites), Nano ZnO and ZnSO4·7H2O on various fractions of soil Zn and agronomic parameters under rice rhizosphere in field experiment for two consecutive growing seasons. Nano Zn carriers (ZNCPC at three doses 100%, 75% and 50%) and nano ZnO were evaluated in comparison with ZnSO4·7H2O in a field experiment under rice (Rajendra Mahsuri) rhizosphere. DTPA Zn was significantly increased under 100% ZNCPC (1.99 mg kg−1). Sequential Zn fractionation revealed that under ZNCPC treatments there was significant increase of water soluble, exchangeable and organically bound Zn, whereas there was significant increase of residual and specifically adsorbed Zn under ZnSO4·7H2O. Grain Zn content was maximum under 100% ZNCPC treatment (40.57 mg kg−1) followed by nano ZnO (34.71 mg kg−1). Maximum AZR (Apparent Zn recovery) was found in case of 100% ZNCPC (26.35%) followed by 75% ZNCPC (21.22%) and nano ZnO (18.73%). ZNCPC was found to be promising Zn formulation for increasing Zn use efficiency. Nano ZnO at foliar spray was also proved to be effective in increasing the grain Zn concentration. However, ZNCPC and nano ZnO need to be evaluated in long-term experiment in various soil types and cropping system for evaluating benefit: cost ratio and wide scale farmers’ adaptability.

Zinc fractions in soils and uptake in winter wheat as affected by repeated applications of zinc fertilizer

This field study was conducted to determine the effect of repeated zinc (Zn) applications at different rates on the concentrations and availability of different forms of Zn in the calcareous soil, in relationship to their contributions to Zn uptake by wheat. Plot-based field experiment was established in 2009 in a winter wheat-summer maize rotation. In each growing season of wheat and maize, six levels of Zn (0, 2.3, 5.7, 11.4, 22.7 and 34.1 kg Zn ha−1) as ZnSO4·7H2O were applied at planting. Following the harvest of the winter wheat in 2010, 2012, 2014 and 2016, soil samples (0−30 cm) from 5 selected Zn levels except 2.3 kg Zn ha-1 were collected and subjected to a sequential extraction to examine the concentrations of Zn fractions including water soluble plus exchangeable Zn (Ex-Zn) and Zn as bounded to carbonate (Car-Zn), manganese oxide (MnO-Zn), iron oxide (FeO-Zn), or organic matter (OM-Zn), and residual (Res-Zn). Stepwise multiple regression was used to identify the contributions of each soil Zn fraction to variation in crop Zn uptake. The results showed that repeated Zn fertilization over the multiple years increased concentrations of all soil Zn fractions. However, the percentage of each Zn fraction to total Zn varied with Zn inputs. Increasing Zn input increased the percentages of Ex-, Carb-, MnO- and FeO-Zn to soil total Zn, whereas reduced that of OM- and Res-Zn. The FeO-, Ex-, and Res-Zn were selected by the stepwise regression procedure as the significant variables explaining the variation in wheat Zn uptake, with partial adjusted coefficient (R2) of 0.81, 0.03 and 0.04, respectively. Crop Zn uptake also increased linearly with soil DTPA-extractable Zn and reached a maximum at DTPA-extractable Zn concentration of 12 mg kg−1. In conclusion, repeated Zn fertilization increased the concentrations of Zn in exchangeable and adsorption forms, which in turn resulted in higher uptake of Zn by winter wheat. DTPA-extractable Zn is a good indicator of Zn availability for wheat. Fraction of FeO-Zn is an important Zn retention pool for determining crop uptake on the calcareous soil. These results emphasize the importance of Zn retention capacity in response to repeated application of Zn fertilizer.

Long-term effects of soil management practices on soil Zn chemical fractions and their availability to grain sorghum {Sorghum vulgare (L.)} grown in a yearly rotation with castor (Ricinus communis) in rainfed red Alfisol soils

ABSTRACTA study was conducted at Hayathnagar Research Farm of ICAR-Central Research Institute for Dryland Agriculture to assess the long-term effects of soil management practices viz. tillage, residue application and N levels on soil Zn fractions and their contribution to soil Zn availability and uptake by grain sorghum grown in a yearly rotation with castor. Results of the study clearly revealed that tillage significantly influenced the Water soluble + Exchangeable Zinc (Zn-CA), zinc specifically sorbed by inorganic sites (Zn-ACC) and available Zinc (Zn-DTPA). However, the remaining Zn fractions were not influenced significantly. Residue application on long-term basis significantly increased the amount of zinc in all the fractions except water soluble + exchangeable Zinc (Zn-CA), and residual zinc (Zn-Res). The application of N @ 90 kg ha−1resulted in a higher amount of zinc in different fractions compared to control. The multiple regression analysis conducted between Zn-DTPA and zinc fractions revealed that the order of magnitude of the positive contribution of the zinc fractions toward zinc availability pool (DTPA-Zn) was: Zn-CA > Zn-ACC > Zn-OX > Zn-Res. The coefficient of multiple determination (R2 = 0.89) was significant at p = .05 level of significance. The order of percent contribution of Zn fractions toward the sum total of all the fractions was: Zn-Res > Zn-PYR > Zn-OX > Zn-ACC > Zn-CA. The multiple regression studies also revealed that all the zinc fractions studied significantly contributed toward Zn uptake by the sorghum crop (R2 = 0.99). Relatively, significantly higher Zn uptake was recorded by sorghum crop under minimum tillage (0.11 kg ha−1) as compared to conventional tillage (0.10 kg ha−1). The results of this study will be highly useful in regulating the Zn availability in soil through soil management practices.

Effects of selenium combined with zinc amendment on zinc fractions and bioavailability in calcareous soil.

Selenium (Se) and zinc (Zn) are two important trace elements for human being and animals. The interaction between Se and Zn on the bioavailability of Zn in soil is still unclear. Therefore, pot experiments exposed to different dosages of zinc sulfate (ZnSO4) (0, 20, and 50mg/kg soil) and sodium selenite (Na2SeO3) (0, 0.5, 1.0, and 2.5mg/kg soil) were conducted to investigate the effects of selenite application on Zn bioavailability in calcareous soil and its related mechanisms. The total Zn content of different tissues (roots and shoots) of pak choi (Brassica chinensis L.) and the changes in Zn fraction distribution in soil before planting and after harvest were determined, and the mobility factor (MF) and distribution index (DI) of Zn in soils were calculated. In addition, the Pearson correlation and path analysis were conducted to clarify the relationships between Zn fractions in soil and the Zn uptake of pak choi. Results showed that Se amendment elevated soil Zn bioavailability at appropriate levels of Se and Zn. When 1.0 and 2.5mg/kg of Se and 20mg/kg of Zn were applied in soil, the proportion of exchangeable Zn (Ex-Zn) and Zn weakly bound to organic matter (Wbo-Zn) to the total content of Zn was significantly increased by 28.14%-82.52% compared with that of the corresponding single Zn treatment. Therefore, the Zn concentration in the shoots of pak choi was significantly increased by 27.2%-31.1%. High Zn (50mg/kg) and Se co-amended treatments showed no significantly beneficial effect on the bioavailability of Zn. In addition, the potential available Zn content in soil (weakly bound to organic matter and carbonate bound Zn) and MF and DI values were all positively correlated with the Zn concentrations in pak choi, indicating that these indexes can be used to predict the bioavailability of Zn in soil. This study can provide a good reference for Se and Zn biofortification of plants in calcareous soil.

Effects of ZnSO4 and Zn‐EDTA applied by broadcasting or by banding on soil Zn fractions and Zn uptake by wheat (Triticum aestivum L.) under greenhouse conditions

AbstractZinc biofortification of staple food crops is essential for alleviating worldwide human malnutrition. Agronomic interventions to promote this should include fertilizer selection and management. A chelated Zn source, Zn‐EDTA, and an inorganic Zn source, ZnSO4 × 7 H2O, were applied either by banding or by broadcasting in soil, and Zn fractions in soil and Zn uptake by wheat were determined in a pot experiment. Compared to ZnSO4 × 7 H2O, Zn‐EDTA produced higher Zn concentration in grain regardless of application method and even at a lower application rate. Residual Zn fraction was the largest Zn fraction with both ZnSO4 and Zn‐EDTA amendment. ZnSO4 banded in soil caused Zn fractions to be restricted to the Zn‐amended soil band and resulted in lower grain Zn concentrations than did broadcast ZnSO4. Planting wheat slowed Zn fixation by promoting the maintenance of a high concentration of Zn fraction loosely bound to organic matter (LOM‐Zn) in soil. Zn‐EDTA was a better Zn source for Zn biofortification of wheat than was ZnSO4.

Effects of ZnSO4 and Zn-EDTA broadcast or banded to soil on Zn bioavailability in wheat (Triticum aestivum L.) and Zn fractions in soil

Human Zn deficiency is prevalent in developing countries, and staple grains are commonly bio-fortified to increase their Zn contents. We measured Zn content, distribution, and bioavailability in calcareous soil and in wheat plants (Triticum aestivum L.) in Shaanxi Province, China, when either an organic Zn-ethylenediaminetetraacetate (Zn-EDTA) or an inorganic zinc sulfate heptahydrate (ZnSO4·7H2O) Zn source was banded below the seedbed or broadcasted into soil. Compared with ZnSO4·7H2O, Zn-EDTA fertilization produced higher Zn concentration and uptake in wheat plants. However, Zn bioavailability in grain remained low, with [phytate]/[Zn] ratio >15 and the resulting estimated dietary total absorbed zinc (TAZ) < 3 mg Zn/d. ZnSO4 banded into soil had little short-term effect on grain Zn concentration but had a high residual effect and promoted the maintenance of a high concentration of the Zn fraction bound to loose organic matter (LOM-Zn) in rhizosphere soil. Both ZnSO4 and Zn-EDTA were more efficient if uniformly mixed through the soil than if banded to soil. Both ZnSO4 and Zn-EDTA had limited effects on Zn bioavailability in wheat plants due to the high rate of Zn fixation in this calcareous soil.

Structural equation model of the relationship between metals in contaminated soil and in earthworm (Metaphire californica) in Hunan Province, subtropical China

Earthworms have the ability to take up heavy metals in soil and partition them in different subcellular compartments. In this study, we used a structural equation model (SEM) to investigate the two-step causal relationship between environmental availability (EA) and environmental bioavailability (EB) of heavy metals (Cd, Cu, Zn, and Pb), as reflected by their levels in soil fractions and in earthworms from field-contaminated areas in Southern China. In the SEM, the correlation between EA and EB reflected the bioavailability of Cd, Zn, and Pb. For Cd, the causal relationship between the latent variables EA and EB was reflected by DTPA fractions in soil as well as by earthworm internal and subcellular cytosol fractions. The extractable and oxidizable fractions of Zn in soil influenced Zn concentrations in the cytosol and debris. The DTPA and reducible Pb fractions were bioavailable to earthworm internal Pb concentrations and those in cytosol fractions. These results implied that the DTPA, extractable, oxidizable, or reducible fractions of different metals could be the bioavailable sources to earthworm internal metals and partitioned in their subcellular compartments.

Distribution of Zinc in Selected Benchmark Soils of South Western Nigeria

The Understanding of the different fractions of Zinc in soils is important to effectively manage fertilizer resources due to the low availability of Zinc in the native soil worldwide. Bioavailability, uptake of Zinc by plant and its fractions depend largely on the soil parent material, the type of chemical transformation the soil has been expose to over times and some anthropogenic intervention. This study examined five different Zn pools.The distribution of Zn in soil fractions was determined for seven selected soils of South Western Nigeria. A sequential batch extraction which had been modified was used to identify Zn fractions and were separated into: the extractable zinc (Ex-Zn), zinc associated with the carbonate (CO3-Zn), the organically bound zinc (Org-Zn), sesquioxide (Ox-Zn) and residual (Res-Zn) in each soil. Total Zn was estimated as a sum of all the pools.Result showed that Zinc fractions in the soils were in this order: extractible pool (3.8%) &lt; organic pool (13.6%) &lt; carbonate pool (14.8%) &lt; sesquioxide pool (22.8%) &lt; residual pool (45.1%). The residual pool amounts for almost half of the zinc that made up the total zinc in the soil. The distribution of zinc into these pools were determined by selected physical and chemical properties of the soil; the pH, organic carbon, clay, CEC, and phosphorus. However, soil phosphorus and pH had the highest influence on the zinc in the experimental soils. The stable fraction that dominated the soil was evident in the low extractable Zn fractions in the soil. Which is an indication of the inherently low levels of the bioavailability of Zn in the selected soils used in this study.

鸟粪对同里湿地公园土壤重金属及其形态的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 鸟粪对同里湿地公园土壤重金属及其形态的影响 DOI: 10.5846/stxb201705220953 作者: 作者单位: 安徽师范大学 国土资源与旅游学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41371480）；安徽师范大学研究生科研创新与实践项目（2017cxsj055） Heavy metal concentrations and speciation of soil affected by bird droppings in Tongli Wetland Park, East China Author: Affiliation: College of Territorial Resources and Tourism,Anhui Normal University,Wuhu Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了解鸟粪对同里湿地公园土壤重金属全量及形态转化的影响，测定了公园内有鸟粪土壤、无鸟粪土壤、鸟粪沉积物的理化性质，Co、Cr、Cu、Ni、Zn全量及其形态分布，并进行统计分析。结果显示：同里湿地公园土壤及沉积物pH值平均含量达4.5，N、C、H、S和TP平均含量分别达到3.69、38.07、10.97、0.52、1.43g/kg，有鸟粪土壤中N、C、H和S含量显著高于无鸟粪土壤。Cu、Zn、Co平均含量呈现出鸟粪沉积物 > 有鸟粪土壤 > 无鸟粪土壤；Cr的平均含量表现为鸟粪沉积物 > 无鸟粪土壤 > 有鸟粪土壤；Ni呈现出有鸟粪土壤 > 鸟粪沉积物 > 无鸟粪土壤。总体上，鸟粪的进入增加了土壤Cu、Zn、Co、Ni含量。因此应及时清理土壤上覆鸟粪，降低对当地重金属污染风险。相对于无鸟粪土壤中不同重金属形态的分布，有鸟粪土壤中Co、Cr、Cu、Zn的活性态占全量的百分比均略有下降，非活性态呈上升趋势。鸟粪的加入，虽然会在一定程度上降低活性态重金属占总量的比例，但因总量和活性态含量均上升，向植物系统的迁移量会呈现增加趋势，因此对鸟粪施肥再利用应慎重。 Abstract:The heavy metal content and speciation in soil and bird droppings from Tongli National Wetland Park were determined. The main purpose was to understand the impact of bird droppings on wetland soil heavy metal contentraions and their speciationchanges. Soil with and without bird droppings was collected from Tongli Wetland. The metal concentrations were determined by inductively coupled plasma-optical emission spectrometry. The result suggested that the average pH for soil was 4.5, and the contents of N, C, H, S, and TP were 3.69, 38.07, 10.97, 0.52, and 1.43g/kg, respectively. Thus, the N, C, H, and S levels in soil containing bird dropping were significantly higher than those in soil without bird droppings. The average contents of Cu, Zn, and Co were in the order guano sediments > soil with bird dropping > soil without bird droppings. The average content of Cr was in the order guano sediments > soil without bird droppings > soil with bird dropping. The average content of Ni was in the order soil with bird droppings > guano sediments > soil without bird droppings. In general, the Cu, Zn, Co, and Ni contents in soil increased with the presence of bird droppings. Bird droppings should be cleaned in a timely manner to reduce the local pollution risk of heavy metals in soil. The percentages of total active Co, Cr, Cu, and Zn fractions in soil containing bird droppings were slightly lower than those in soil without bird droppings. The inactive state showed an upward trend. The proportion of the total activity of heavy metals in soil reduced with the presence of guano, but the content of total and active heavy metals in the soil increased; therefore, the amount of migration of plant systems will increase, and fertilization using bird droppings should be applied carefully. 参考文献 相似文献 引证文献

Fractionation and bioavailability of zinc (Zn) in the rhizosphere of two wheat cultivars with different Zn deficiency tolerance

Zinc (Zn) deficiency is a widespread problem in wheat-cultivated lands, and understanding important mechanisms determining Zn phytoavailability is of high importance. Accordingly, a two-year field experiment was conducted to investigate the effects of two Zn-deficiency tolerant wheat cultivars on Zn binding forms in a calcareous saline soil. Changes in soil Zn fractions were also found to be related to Zn uptake by wheat. Rhizosphere and bulk soil samples and the above-ground biomass were collected at grain maturity and analyzed for Zn. By using a sequential extraction procedure, soil Zn was divided into the following operationally defined fractions which are conceptually designated: ‘exchangeable Zn’ (EXCH-Zn), ‘Zn bound to carbonates’ (CAR-Zn), ‘organically bound Zn’ (ORG-Zn), ‘Zn bound to iron and manganese oxides’ (FeMnOX-Zn), and ‘residual Zn’ (RES-Zn). EXCH-Zn and ORG-Zn in the rhizosphere soil were found to be positively correlated with Zn uptake into the aboveground biomass of both wheat cultivars, thereby indicating that these fractions could be considered as labile pools. Higher EXCH-Zn and ORG-Zn fractions were determined in the rhizosphere, not in the bulk soil, whereas the non-labile Zn pools was decreased, suggesting strong Zn solubilization due to the input of acidity and organic compounds by root and the associated microbial activity. The differences between rhizosphere and bulk soil in EXCH-Zn and ORG-Zn were associated with the lower pH and the higher concentrations of the total (TOC) and dissolved organic carbon (DOC) in the rhizosphere. The fact, these effects (lower pH and higher DOC in the rhizosphere, rather than in the bulk soil) were stronger for Back Cross Rushan than were for Kavir; this was in line with the higher Zn uptake of Zn-deficiency tolerant Back Cross Rushan.

Bioavailability of coated and uncoated ZnO nanoparticles to cucumber in soil with or without organic matter

There is a gap of knowledge for the fate, effects and bioavailability of coated and uncoated ZnO nanoparticles (NPs) in soil. Moreover, little is known about the effects of soil properties on effects of NPs on plants. In this study, the availability ZnO NPs in two soils with different organic matter content (one treated with cow manure (CM) and the other as untreated) was compared with their bulk particles. Results showed that coated and uncoated ZnO NPs can be more bioaccessible than their bulk counterpart and despite their more positive effects at low concentration (< 100mgkg−1), they were more phytotoxic for plants compared to the bulk ZnO particles at high concentration (1000mgkg−1) in the soil untreated with CM. The concentration of 1000mgkg−1 of ZnO NPs, decreased shoot dry biomass (52%) in the soil untreated with CM but increased shoot dry biomass (35%) in CM-treated soil compared to their bulk counterpart. In general, plants in the CM-treated soil showed higher Zn concentration in their tissues compared with those in untreated soil. The difference in shoot Zn concentration between CM-treated and untreated soil for NPs treatments was more than bulk particles treatment. This different percentage at 100mgkg−1 of bulk particles was 20.6% and for coated and uncoated NPs were 37% and 32%, respectively. Generally, the distribution of ZnO among Zn fractions in soil (exchangeable, the metal bound to carbonates, Fe-Mn oxides, organic matter and silicate minerals and the residual fraction) changed based on applied Zn concentration, Zn source and soil organic matter content. The root tip deformation under high concentration of NPs (1000mgkg−1 treatment) was observed by light microscopy in plants at the soil untreated with CM. It seems that root tip deformation is one of the specific effects of NPs which in turn inhibits plant growth and nutrients uptake by root. The transmission electron microcopy image showed the aggregation of NPs inside the plant cytoplasm and their accumulation adjacent to the cell membrane.