Extractable Zn Concentrations Research Articles

Spatial Variability of Soil Micronutrient Properties Using Geostatistical Approach and Geographic Information System Technique

The distribution of soil qualities in every given area is essential for the development of management strategies that are appropriate to that site, since this promotes agricultural productivity sustainability and preserves the health of the soil.In spite of this, the current study was carried out in the Madhya Pradesh state of India to measure the spatial distribution of specific soil qualities in the soybean-wheat and soybean-chickpea belt. A total 303 geo-referenced composite surface (0-15cm) soil samples were collected across the study area. These samples were analyzed for different soil properties viz: pH, soil organic carbon (SOC), Calcium carbonate (CaCO3) the DTPA extractable Zn, Cu, Mn and Fe. The main goals of the study were to: (i) use geo-statistical methods to assess the spatial variability of soil available micronutrients, such as extractable zinc (Zn), copper (Cu), manganese (Mn), iron (Fe), and boron (B), at a regional scale; (ii) use ordinary kriging to develop maps of soil micronutrient distribution; and (iii) evaluate the relationships between micronutrient availability and several soil properties. It was revealed that 79.54% and 7.92% of the soil samples had shortages in accessible zinc and iron, respectively, but no soil sample had deficiencies in copper, magnesium, or zinc and sulphur. The concentrations of extractable Zn, Cu, Mn, and Fe, with the exception of B, exhibited substantial negative relationships with the pH of the soil. The EC had positive and significant relationship with SOC and B, respectively. The significant positive relationship of SOC of soil with available hot water-soluble B respectively. The soil micronutrients were showed significant positive relationship with each other. HWS B was also shown to be positive and statistically significant. In this study, spherical models were best suited for Cu, Mn, and Fe, whereas exponential models were best fitted for Zn and B. The semivariogram models for Zn, Fe, Cu, Mn, and B's nugget/sill ratios There was a documented moderate regional dependence for extractable Zn, Cu, Mn, Fe, and B for Mn.

Soil and Plant Enzymes Responses to Zinc Oxide Nanoparticles in Submerged Rice (Oryza sativa L.) Ecosystem

In the present study, the effects of zinc oxide nanoparticles (ZnO NPs) on rice (Oryza sativa L. cv. PB1509) plant growth were assessed in hydroponics (5, 10, 25, 50 mg L−1) and soil microcosm (5, 10, 25 50 mg kg−1) experiments. In both hydroponics and soil experiments, Zinc (Zn) accumulation in plant parts (roots, shoots and grains) was found to increase with increasing doses of ZnO NPs. Grains accumulated 29 mg kg−1 Zn at 50 mg kg−1 ZnO NPs in the soil experiment. In the hydroponics experiment, growth and photosynthetic pigments were induced by ZnO NPs up to 10 mg L−1, while higher doses of 25 and 50 mg L−1 were toxic to plant growth. Antioxidant enzyme activities (SOD, CAT, APX and GPX) were mostly increased or unaffected by all ZnO NPs doses. In soil experiments, acid and alkaline phosphatase activities were increased at 5 mg kg−1 followed by a declining trend. However, a significant decrease occurred only at 50 mg kg−1. Urease activity in soil was significantly increased at all doses of ZnO NPs, while the activity of dehydrogenase did not show any significant change up to 25 mg kg−1. The length of plants and photosynthetic pigments did not show much toxicity except root length beyond 10 mg kg−1; however, the biomass of plants including grains was significantly lower than control beyond 5 mg kg−1 dose. The activity of antioxidant enzymes (GPX, APX and CAT) showed a significant increase at all doses of ZnO NPs. The DTPA extractable Zn concentration in the soil was significantly elevated with increasing exposure concentrations of ZnO NPs. Based on hydroponics and soil experiments, this study suggests a dose of up to 10 mg L−1 or 10 mg kg−1 would be an appropriate dose for augmenting the growth of rice plants and Zn accumulation, and this can be practically utilized for rice plants growing in submerged conditions. HIGHLIGHTS Rice plants exposed to ZnO nanoparticles in hydroponics and soil Zinc accumulation increased significantly in roots, shoots and grains Lower dose of ZnO NPs (10 mg/L or mg/kg) augmented plant growth Antioxidant enzymes showed a significant increase in activity in ZnO NPs treatment GRAPHICAL ABSTRACT

Influence of Different Rates and Frequencies of Zn Application to Maize–Wheat Cropping on Crop Productivity and Zn Use Efficiency

Nowadays, zinc (Zn) fertilizers are commonly used for quality food production globally. Knowledge about proper application time and rates of commercial Zn fertilizers is necessary to obtain higher crop production and improve Zn use efficiency. A long-term field experiment was conducted during 2012 to 2018 at Anand Agricultural University, Anand (Gujarat), India, to find out the right Zn fertilizer dose and its frequency of application in maize–wheat cropping systems grown on typic haplustepts soil. The study comprised of three frequency levels, i.e., Zn application in the first year only (F1), alternate year (F2), and every year (F3), with four different rates of Zn, i.e., 2.5, 5.0, 7.5, and 10.0 kg Zn ha−1 per year imposed in the maize–wheat cropping system in each kharif season (during June to September) for six years. Findings of the study revealed that Zn applications to maize at 7.5 and 10 kg ha−1 in alternate year and 5.0 to 10 kg ha−1 in every year significantly increased maize equivalent yield as compared to no-Zn treatment. Application of 10.0 kg Zn ha−1 per year produced higher grain size, straw, and total Zn concentrations compared to those observed under no-Zn application in maize and wheat crops. Diethylene triamine penta acetic acid extractable Zn concentration in soil was higher in Zn treated plots which received Zn application at 5.0, 7.5, and 10.0 kg ha−1 in alternate years and 10 kg ha−1 in every year as compared to no-Zn application. Apparent Zn recovery efficiency varied from 0.17 to 1.46% for maize crop and 0.34 to 1.70% for wheat crop under different rates and frequencies of Zn application. The above results emphasize the importance of Zn retention capacity of soil regarding its response to different rates and frequencies of Zn application to maize and wheat crops.

Zero-valent iron nanoparticles and organic amendment assisted rhizoremediation of mixed contaminated soil using Brassica napus

Soil is one of our most important natural resources. Regrettably, the expansion of human activities has resulted in the degradation of the soil resource due to contamination with a myriad of organic and inorganic compounds. The remediation of mixed contaminated soils, i.e. soils contaminated with both organic compounds and metals, is challenging as it requires actions to simultaneously decrease metal-induced risks and organic contaminant concentrations. Here, we evaluated the effect of the addition of zero-valent iron nanoparticles (nanoremediation) and organic amendments (biostimulation) on the rhizoremediation, using Brassica napus plants, of soil simultaneously contaminated with zinc (2500 mg kg −1 ) and lindane (100 mg kg −1 ). We used a factorial design with three factors (amendment, nZVI, plant) to evaluate the impact of the applied remediation actions on lindane and extractable Zn concentrations, as well as on soil health recovery as manifested by the values of different soil microbial indicators. The studied microbial indicators were not negatively affected by nZVI application. The application of nZVI was the most effective factor regarding the targeted reduction in lindane concentration (51% average reduction in nZVI treated soils). The highest reduction in extractable Zn was achieved in the presence of B. napus , nZVI and organic amendments (99 and 95% reduction in horse manure-amended and sewage sludge-amended soils, respectively). The combination of the three factors led to the highest values of soil microbial indicators (although a significant triple interaction was not observed for all parameters), especially when combined with horse manure amendment: in this case, prokaryotic richness increased by 64%, respiration by 376%, eukaryotic abundance by 333%, and prokaryotic abundance by 437%, compared to untreated soils. The combination of remediation approaches (rhizoremediation with B. napus , nanoremediation with nZVI, biostimulation with organic amendments) can help overcome the limitations of each individual strategy. • The combination of Brassica napus , nZVI and amendments improved soil health. • The combination of B. napus , nZVI and amendments reduced soil extractable Zn. • The application of nZVI led to the highest decrease in soil lindane concentration. • Soil microbial communities were not negatively affected by nZVI application.

Can Diffusive Gradients in Thin Films (DGT) Technique and Chemical Extraction Methods Successfully Predict both Zn Bioaccumulation Patterns in Plant and Leaching to Groundwater in Soils Amended with Engineered ZnO Nanoparticles?

The interactions of nanoparticles (NPs) with different soil components have impact on their fate, transport, and behavior. The present study was conducted to find operational extraction procedures for effective assessment of both plant availability and leaching to groundwater of Zn applied to soils from zinc oxide (ZnO) NPs. A greenhouse experiment was performed in lysimeters with different ZnO-NPs amounts (3, 20, and 225 mg Zn kg−1) in two typical soils in Central Spain. The experiment was carried out spanning the whole plant life-cycle of cherry tomato and common bean. The soil extractable Zn amounts were measured using chemical extraction procedures (the rhizosphere-based low-molecular-weight organic acids—LMWOAs—, CaCl2, DTPA-TEA, water-soluble—WS—, and NH4Ac) and the diffuse gradients in thin films (DGT) technique. The regression studies between extractable Zn concentrations and Zn concentrations in plant tissues showed that LMWOAs, CaCl2, WS, and the DGT technique successfully predicted Zn concentrations in all the different parts of plants. The prediction capacity of the DTPA-TEA and NH4Ac approaches were strongly influenced by soil type and plant species. LMWOAs, CaCl2, WS, and the DGT technique were the most robust approaches for evaluation of Zn bioavailability from the soils treated with ZnO-NP. Although LMWOAs and WS reagents were also able to estimate the total quantities of Zn that were leached to groundwater, the correlation improved when soil type was included as a categorical variable. DTPA-TEA and NH4Ac were able to predict the Zn concentrations in the plant tissues only if soil type was considered as a categorical factor.

Can the application of zinc decrease cadmium concentrations in spinach in a zinc sufficient soil?

ABSTRACTThe application of zinc (Zn) fertiliser to soil has been proposed as a mitigation strategy to decrease plant cadmium (Cd) concentrations. The strategy is untested in New Zealand and it is unclear whether it is effective in soils that are not Zn deficient. We undertook a glasshouse experiment and measured what effect applying Zn had on Cd concentrations in spinach (Spinacia olearacea L.) cultivated in a soil with a high extractable Zn concentration (7.3 mg kg−1) and total Cd concentration of 0.48 mg kg−1. The addition of 5–20 kg Zn ha−1 as zinc sulphate decreased Cd concentrations in spinach leaves after 64 days growth by 19–28% and in roots by up to 42%. In contrast, the addition of Zn increased Zn concentrations in spinach roots and leaves by 55% and 112% respectively. The decrease in Cd concentrations in spinach was likely a result of competition with Zn that restricted Cd uptake into the root. The results indicate there may be potential in using Zn fertiliser to decrease plant Cd concentrations. However, investigation needs to be undertaken to evaluate its effectiveness for soil types with different properties and Zn status, other food crops which may respond differently to spinach and the results confirmed in a field experiment.

Comparing chemical extraction and a piecewise function with diffusive gradients in thin films for accurate estimation of soil zinc bioavailability to Sedum plumbizincicola

SummaryAccurate evaluation of metal bioavailability to hyperaccumulators is necessary for prediction of metal uptake and estimation of phytoextraction potential. Sedum plumbizincicola X.H. Guo et S.B. Zhou ex L.H. Wu (Crassulaceae), a hyperaccumulator of cadmium (Cd) and zinc (Zn), was grown in a pot experiment in 108 agricultural soils representing a wide range of typical Chinese soil types. The contribution of soil properties to Zn uptake was assessed quantitatively. Soil total Zn, soluble Zn, CaCl2‐extractable Zn and (DGT)‐extractable Zn concentrations (Zntotal, Znsoln, ZnCaCl2 and ZnDGT, respectively) were compared to predict shoot Zn concentration (Znshoot) using a piecewise equation. This showed a logarithmic increase with increasing Zntotal from 100–1000 mg kg−1 but plateaued outside this range. The optimum soil pH for Zn removal was ~ 5.5 and further acidification was unnecessary because Znshoot increased significantly with a decrease in pH from 7.5 to 5.5 and rarely changed at pH < 5.5. Sedum plumbizincicola grown in loamy or clay loam soils had larger Znshoot than in sandy or clay soils. The ZnCaCl2 was superior to other methods in estimating Zn bioavailability across all the data. At pH < 5.5, ZnCaCl2 showed much stronger correlation with Znshoot than Zntotal, Znsoln or ZnDGT. Piecewise equations (single linear regression equations at different intervals of soil properties) versus Zntotal and ZnCaCl2 at different pH ranges considerably increased the accuracy of prediction of Znshoot compared with the global equations derived from all data. Estimation of the potential of S. plumbizincicola for Zn phytoextraction in the field indicated that it is feasible to decontaminate acid‐polluted soils with Zntotal ≤ 500 mg kg−1 with S. plumbizincicola.Highlights Zn bioavailability to hyperaccumulators needs to be estimated over a wide range of soil types. Piecewise equations considerably improved the prediction of shoot Zn concentration. CaCl2 extraction was more suitable than DGT for the estimation of Zn bioavailability. Decontamination with S. plumbizincicola is feasible for acid soils with Zntotal ≤ 500 mg kg−1.

The Application of Nanoscale Zero-Valent Iron Promotes Soil Remediation While Negatively Affecting Soil Microbial Biomass and Activity

The use of nanoscale zero-valent iron particles (nZVI) for soil remediation is gaining increased attention. However, there are concerns about the potential adverse effects of nZVI on soil microbial communities and, hence, soil quality. The objective of this study was to assess the impact of the application of nZVI on soil microbial parameters (as bioindicators of soil quality) during the nanoremediation of a soil artificially contaminated with lindane (10 mg γ-HCH kg-1 DW soil) and zinc (1,500 mg Zn kg-1 DW soil). nZVI were also applied to non-contaminated soil. The following nZVI doses were applied twice: 0, 0.25, 0.5, 1 and 2 mg nZVI g-1 DW soil. Nine weeks after nZVI application, the following parameters were determined in soil samples: lindane concentration, extractable Zn concentration, microbial biomass carbon (CMB), bacterial and fungal abundance (gene copy numbers by qPCR), enzyme activities (β-glucosidase, β-glucosaminidase, xylosidase, acid phosphatase, arylsulphatase and Leu-aminopeptidase) and bacterial richness by ARISA profiles. The application of nZVI reduced lindane and extractable Zn concentrations following a dose-dependent pattern. The presence of contaminants reduced soil microbial biomass and activity. The application of nZVI negatively affected the microbial quality of the contaminated soil but not of the non-contaminated soil. This observation might reflect a “stress-on-stress” effect, i.e. the already stressed microbial populations present in the contaminated soil were more sensitive to the application of nZVI (a second stress) than those present in the non-contaminated soil.

Sulfur and Zinc Availability from Co-granulated Zn-Enriched Elemental Sulfur Fertilizers.

Acidification by oxidation of elemental sulfur (ES) can solubilize ZnO, providing slow release of both sulfur (S) and zinc (Zn) in soil. For this study, a new granular fertilizer with ES and ZnO was produced and evaluated. The effect of incorporating microorganisms or a carbon source in the granule was also evaluated. Four granulated ES-Zn fertilizers with and without S-oxidizing microorganisms, a commercial ES pastille, ZnSO4, and ZnO were applied to the center of Petri dishes containing two contrasting pH soils. Soil pH, CaCl2-extractable S and Zn, and remaining ES were evaluated at 30 and 60 days in two soil sections (0-5 and 5-9 mm from the fertilizer application site). A visualization test was performed to evaluate Zn diffusion over time. A significant pH decrease was observed in the acidic soil for all ES-Zn fertilizer treatments and in the alkaline soil for the Acidithiobacillus thiooxidans-inoculated treatment only. In agreement with Zn visualization tests, extractable-Zn concentrations were higher from the point of application in the acidic (62.9 mg dm-3) compared to the alkaline soil (5.5 mg dm-3). Elemental S oxidation was greater in the acidic soil (20.9%) than slightly alkaline soil (12%). The ES-Zn granular fertilizers increased S and Zn concentrations in soil and can provide a strategically slow release of nutrients to the soil.

Spatial variability of soil micronutrients in the intensively cultivated Trans-Gangetic Plains of India

Soil micronutrient deficiency adversely affects crop production in intensive agriculture. However, information on the spatial variability of key micronutrients in intensively cultivated regions of India is limited. Thus, the present study was carried out in the Trans-Gangetic Plains (TGP) region of India with the hypothesis that spatial variability of micronutrient availability is high due to small farms and varied management. The major objectives of the study were (i) to assess the spatial variability of plant available micronutrients, viz. extractable zinc (Zn), copper (Cu), manganese (Mn) and iron (Fe) at a regional scale through geostatistical methods, (ii) to develop distribution maps for soil micronutrients using ordinary kriging and (iii) to assess the relationships of micronutrient availability with several soil properties. A total of 5638 soil samples, representative of the surface (0⿿15cm) horizon were collected (covering Inceptisols, Entisols, Alfisols and Aridisols) during April to June between 2011 and 2014 from farms in 21 districts of the TGP. For each micronutrient, semivariograms were calculated and their main parameters (nugget effect, sill and range) were obtained. Moderate spatial dependence for extractable Zn, Cu and Fe and strong spatial dependence for extractable Mn were recorded. The nugget/sill ratio values were 0.60, 0.37, 0.34 and 0.19 for extractable Zn, Fe, Cu and Mn, respectively. Available Fe, Zn, Mn and Cu deficiencies (including acute deficiencies) were observed in 28, 15, 14 and 13% of soil samples, respectively. Soil pH showed significant and negative correlations with the concentrations of extractable Zn, Cu, Mn and Fe; whereas the correlation was significant and positive with soil organic carbon (SOC) concentration. The distribution maps generated could be used as a guide for precise and site-specific micronutrient management in the study region.

Comparison of diffusive gradients in thin film technique with traditional methods for evaluation of zinc bioavailability in soils.

The technique of diffusive gradients in thin film (DGT) has been shown to be a promising tool to assess zinc (Zn) bioavailability in soils, but there exists considerable debate on its suitability. In this study, Zn bioavailability was systematically investigated in wheat- and maize-grown soils using this technique and seven traditional methods, including soil solution concentration and six widely used single-step extraction methods (HAc, EDTA, NaAc, NH4Ac, CaCl₂, and MgCl₂). The concentrations of Zn in the shoots and roots of these two plant species increased continuously with increasing additions of Zn to the soils, accompanied by significant decreases in shoot biomass and root biomass at Zn concentrations greater than 400 mg kg(-1) for maize and 800 mg kg(-1) for wheat. Zinc uptake and accumulation was higher in maize roots than in wheat roots. Both the concentrations of bioavailable Zn measured by DGT (CDGT) and soil solutions (Csol) increased linearly with increasing additions of Zn to the soils, while no strong linear relationships were observed for the extraction methods. Higher concentrations of extractable Zn, lower values of Csol, and larger values of R (i.e., the ratio of CDGT to Csol) were observed in maize-grown soils compared with those of wheat-grown soils, while the values of C DGT between the two plants were similar. These findings demonstrate that there likely exists a stronger resupply of Zn from the soil solid phases in maize-grown soils to satisfy a higher Zn uptake and accumulation in this plant. Linear correlation analyses showed that CDGT had the highest correlation coefficients with plant Zn concentrations compared with other traditional methods, implying that the DGT technique is more sensitive and robust in reflecting Zn bioavailability in soils to plants.

Effect of preceding crops and their residues on availability of zinc in a calcareous Zn-deficient soil

Limited information is available on the effect of preceding crop on phytoavailability of zinc (Zn) in soil. This pot experiment examined the effect of four preceding crops including clover, sunflower, safflower, and sorghum residues on shoot and grain Zn uptake by two wheat genotypes differing in Zn-deficiency tolerance Back Cross and Kavir in a calcareous Zn-deficient soil. Incorporation of all preceding crop residues into the soil significantly increased organic matter (OM) content, dissolved organic C (DOC), and diethylene triamine pentaacetic acid (DTPA) extractable Zn concentration in the soil. Residues of safflower and clover had the greatest effect on increasing DOC. Shoot and grain Zn concentrations were increased by incorporating all pre-crop residues into the soil although this increase was greater at safflower and clover treatments. Incorporation of sorghum residues into the soil had a negative effect on shoot and grain dry matter yield of wheat. Incorporation of safflower and clover residues into the soil increased Zn uptake by wheat shoot and grain. There was a positive significant correlation between shoot and grain Zn concentration with DOC in soil solution. It shows that DOC, produced from decomposition of crop residues, has facilitated Zn uptake by roots of wheat plants and particularly its transfer to grains.

Feasibility of Labile Zn Phytoextraction Using Enhanced Tobacco and Sunflower: Results of Five- and One-Year Field-Scale Experiments in Switzerland

Phytoextraction with somaclonal variants of tobacco and sunflower mutant lines (non-GMs) with enhanced metal uptake and tolerance can be a sustainable alternative to conventional destructive decontamination methods, especially for stripping bioavailable zinc excess in topsoil. The overall results of a 5-year time series experiment at field scale in north-eastern Switzerland confirm that the labile Zn pool in soil can be lowered by 45–70%, whereas subplots without phytoextraction treatment maintained labile Zn concentrations. In 2011, the phytoextraction experiment site was enlarged by a factor of 3, and the labile 0.1 M NaNO3 extractable Zn concentration in the soil was reduced up to 58% one period after harvest. A Mass Balance Analysis confirmed soil Zn decontamination in line with plant Zn uptake. The plants partially take Zn from the non-labile pool of the total. The sustainability of Zn phytoextraction in subplots that no longer exceed the Swiss trigger value is now assessed over time. In contrary to the phytoextraction of total soil Zn which needs a long cleaning up time, the bioavailable Zn stripping is feasible within a few years period.

Multivariate statistical and GIS-based approach to evaluate heavy metals behavior in mine sites for future reclamation

Soil contamination by metals has become a widespread serious problem in many parts of the world. Two tailing ponds (Lirio and Gorguel) from an abandoned Pb–Zn mine for a future reclamation were selected, surface samples were taken and analyzed for waste properties and total, extractable by DTPA and water-soluble Pb, Cu, Zn and Cd content. Results showed that both ponds were polluted by Cd, Pb, and Zn. High total concentrations of Zn and Pb and high percentage of extractable-Cd in both ponds suggested high risk of mobility via plants uptake. Due to high concentrations of soluble Zn and percentages of soluble Cd, especially in Lirio pond, these metals could be mobilized by runoff water and reach streams or leach to waste deep layers and contaminate soil and even groundwater. Thus, the immobilization of these metals should be a priority in reclamation actions. Statistical analyses showed that, for Lirio pond, soluble Cd and Zn and extractable Cd, Zn and Pb concentrations were increased by the presence of organic matter, due likely to formation of soluble organic ligands. Clay and electrical conductivity also increased soluble and extractable Zn concentrations, which could be attributed to adsorption of metals for clays combined by the effect of competition for sorption sites with cations and metal-complexation with anions. Finally, soluble Pb was controlled by pH. Therefore, it is recommended the use of alkaline amendment, which will increase the pH and immobilize the metals preventing the effect of organic matter. However, in Gorguel pond, the concentration of soluble and extractable Zn, Pb and Cd were dependent on pH and salinity. Since the pH of this pond is high, it is not necessary to increase it. Oppositely, the reclamation program should include actions to reduce soluble salts generated by oxidation process, which would reduce heavy metal mobility. A GIS-based approach was adopted to identify highest risk sites, where main efforts of reclamation and monitoring should be realized. Three locations in the Lirio pond and two in the Gorguel pond were selected according to their environmental risk, north, south and west edges for Lirio and west and center for Gorguel.

English

The objective of this study is to investigate the effect of three kinds of biosolids usage on soil chemical properties and uptake of heavy metals by Cercis siliquastrum leaves. The experiment was carried out in a completely randomized block design with seven treatments including: no fertilizer as a control (C), sewage sludge (SW), cow manure (CM), municipal solid waste compost (MC), mixture of sewage sludge and cow manure (50% SW + 50% CM), mixture of sewage sludge and municipal solid waste compost (50% SW + 50% MC) and mixture of cow manure and municipal solid waste compost (50% CM + 50% MC) at three levels of 0, 2.5 and 5 kg/shrub and three replicates in calcareous sandy loam soil at the botanical garden of Mobarekeh steel company. After 180 days, soil samples were collected from 30 cm depth and leaves assemblage. Results showed that the treatments had significant effect (P < 0.05) on organic matter content, pH, electrical conductivity and cation exchange capacity of the soil. Total diethylen-triamine pent acetic acid (DTPA) extractable concentrations of Zn, Fe and Pb increased significantly (P < 0.05) in biosolid treatments. Between unwashed and washed metals concentrations of leaves, significant differences were shown, so it appeared that the source of metals on leaves was mainly airborn. Key words: Biosolids, soil chemical properties, heavy metals, Cercis siliquastrum.

Effects of salinity on partitioning, uptake and toxicity of zinc in the earthworm Eisenia fetida

Salinisation of soil is a problem in many parts of the world especially in agricultural lands that could also be contaminated with metals from pesticide use. This study aimed to derive a quality criterion standard in a defined substrate with the eventual aim of protecting earthworms against salinity, and to assess the influence of salinity on partitioning of, uptake in and toxicity of zinc to earthworms. To achieve this, two experiments were conducted with specimens of Eisenia fetida exposed in the laboratory for 28 days using OECD artificial soil spiked with either NaCl (experiment 1) or combination of Zn and NaCl (experiment 2). In the first experiment, NaCl was added in the following concentrations: 0, 1000, 2000, 4000, 6000 and 8000 mg kg −1 NaCl. Mortality, growth and cocoon production were assessed at day 28. The results showed 28-day LC 50 of 5436 mg kg −1 for NaCl. The EC 50s for growth and cocoon production were 4985 and 2020 mg kg −1 NaCl, respectively. In the second experiment, Zn, added as ZnCl 2 in a range of sub-lethal concentrations (0, 250, 500, 750 mg kg −1 Zn) was combined with 0, 2000 or 4000 mg kg −1 NaCl. The endpoints: mortality, weight change, and the internal zinc concentration were assessed at day 1, 7, 14 and 28 while cocoon production was assessed only at day 28. Apart from the total zinc concentration in the substrates, DTPA and CaCl 2 extractable Zn concentrations were also determined at day 1 and 28 to assess how salinity influenced the partitioning of this metal in the substrates. There was a significant increase in CaCl 2 and DTPA extractable Zn in the substrates as salinity increased suggesting that salinity influenced the partitioning of Zn in the substrates. Weight and mortality of worms were not significantly affected by NaCl and Zn as individual substances, but in combination both had significant effects on these parameters. In contrast, cocoon production was significantly affected by increased NaCl and Zn administered as individual substances, and the effects were more severe when both substances were present. The apparent synergy between Zn and NaCl could not be fully explained by internal zinc concentrations in the worms. It could, however, be partly explained by Cl − effect from the addition of Zn as ZnCl 2. It is concluded that salinity resulting from increased NaCl had an additive to synergistic effect in combination with Zn, in influencing toxicity to these earthworms.

Lettuce grown on calcareous soils benefit from sewage sludge

The present study aimed to evaluate the effects of sewage sludge, manure and humic acid applications on soil properties and element concentrations of soil and plants. As a field experiment, lettuce was grown on soil amended with 0, 20, 40 and 80 t ha−1 of sewage sludge or manure. Humic acid was applied on sewage sludge amended plots as 250 kg ha−1. Addition of sewage sludge and manure increased lettuce yield, head circle, head height and leaf number and N, P, K and Mg levels to same extent. Leaf Cd concentration increased in sludge treated plots more than manure treated plots. Sewage sludge and manure applications increased organic matter, electrical conductivity, total N, available P, exchangeable K, total Cu, Ni and AB-DTPA (ammonium bicarbonate-diethylenetriaminepentaacetic acid) extractable Mn, Cu and Cd concentrations of topsoil. Extractable Fe, Cr and Zn and total Cd, Cr and Zn increased in soil with added sludge. Soil pH was unaffected by either sludge or manure applications. Lettuce leaf concentrations of Cd from the plots treated with humic acid were lower than those not treated with humic acid. Sludge together with humic acid application significantly increased soil available P, and impeded the increase of the soil AB-DTPA extractable Zn concentration. It may be concluded that sewage sludge can be an alternative to manure to enrich organic matter, and rectify N, P, Fe and Zn deficiencies with high pH and calcareous soils. Also, humic substances can be used, to a limited extent, for controlling the availability of sludge-borne heavy metals.

Heavy Metal Concentrations in Soils and Irrigation Waters in Thessaly Region, Central Greece

The purpose of this work was to provide information on heavy metals concentrations in soils and in irrigation water in Thessaly, Central Greece, where tobacco (Nicotiana tabacum) is cultivated. Tobacco tends to accumulate high levels of heavy metals, especially Cadmium. During the years 1998, 1999, and 2000, 795 surface soil samples (0 to 30 cm depth) and 200 water samples were collected from Karditsa, Larissa, and Trikala areas. Soil samples were analyzed for pH, organic matter, electrical conductivity, and clay content. Total (extraction with Aqua Regia) and available (DTPA‐extractable) heavy metal (Zn, Cu, Mn, Cd, and Pb) concentrations were determined by FAAS and GF‐AAS technique. The same technique was also used for the determination of the dissolved heavy metals in acidified (HNO3) water samples (pH<2). The values of soil pH ranged between 4.3 and 8.4, organic matter content between 0.2 and 2.6%, electrical conductivity between 108 and 1100 µS cm−1, and clay content between 12 and 39%. Total concentration of extractable Zn, Cu, Mn, Cd, and Pb (Aqua Regia method) ranged between 12 and 57, 5 and 61, 156 and 2231, 0.03 and 0.93, and 3 and 47 mg kg−1 dry soil, respectively and were all below European Community recommended limits. The concentration of heavy metals (DTPA method) in relation to total concentration (Aqua Regia method) was as follows: Cd: 17.8%; Pb: 6.7%; Cu: 3.8%; Mn: 1.9%; and Zn: 1.6%, indicating that Cd had the highest relative availability of the five metals tested. Significant negative correlation was found between soil pH and DTPA‐extractable Zn (0.48**) and Mn (0.78**). Total soil metals were significantly correlated with organic matter content Zn (0.33**), Cu (0.48**), Pb (0.39**), soil clay Zn (0.32**), and Cu (0.35**). In irrigation waters dissolved heavy metals in most cases were not detectable.

Amenização do calcário na toxidez de zinco e cádmio para mudas de Eucalyptus camaldulensis cultivadas em solo contaminado

Neste estudo, avaliaram-se os efeitos da aplicação de doses de calcário em misturas de solo com proporções crescentes de contaminação por Zn e Cd sobre o crescimento de Eucalyptus camaldulensis. O experimento foi realizado em casa de vegetação, e os níveis de contaminação foram obtidos pela mistura de 0, 25, 50 e 100 % de um solo contaminado a um outro não contaminado, usado como diluente. As doses de calcário foram correspondentes a 0, 10, 20, 40 e 80 t ha-1, e o experimento foi feito em vasos que continham 1,5 kg de solo, em esquema fatorial 4 x 5. A adição de calcário elevou o pH do solo próximo à neutralidade, reduziu os teores de Zn e Cd extraíveis no solo e beneficiou o crescimento das plantas. No solo de maior contaminação, as plantas morreram cinco dias após o transplantio no tratamento sem a adição de calcário. O calcário reduziu os teores de Zn na parte aérea a concentrações abaixo das consideradas tóxicas para as plantas, mas não apresentou o mesmo efeito sobre os teores de Cd. Os efeitos do calcário sobre a disponibilidade de Zn e Cd, teores na parte aérea e crescimento das plantas indicaram o potencial deste corretivo como agente amenizante da toxidez de Zn e Cd para mudas de E. camaldulensis em solos contaminados.

EFFICIENCY OF MULTINUTRIENT EXTRACTANTS FOR THE DETERMINING OF AVAILABLE ZINC IN SOILS

The increasing use of the ICP-AES (inductively coupled plasma atomic emission spectrophotometry) as a multielement analytical technique has stressed the preference for the use of multinutrient extractants in routine soil analysis. However, few studies relating the extraction of zinc (Zn) from soil with such extractants and the absorption of the element by plants have been published. Two experiments under greenhouse conditions were carried out in order to determine the efficiency of some multinutrient extractants for the determination of available Zn in 44 soils from the State of São Paulo, Brazil, for corn and soybean. All soil samples were limed to increase the CEC's base saturation at pH 7 to 70%. Twenty-two soil samples with DTPA (diethylenetriaminepentaacetic acid) extractable Zn concentration lower than 0.6 mg dm−3 received either the application of B, Cu, Mn, Zn or of these micronutrients excluding Zn. The remaining 22 soil samples, with Zn concentration above 0.6 mg dm−3, received application of three micronutrients (B, Cu and Mn). Macronutrients were applied to all pots as needed for crop development. Zinc was extracted from the soils before each planting using the extracting solutions, DTPA, Mehlich 1 (M-1), Mehlich 3 (M-3) and AB-DTPA (ammonium bicarbonate-DTPA) and determined by ICP-AES. The results showed significant correlations between plant Zn concentration and soil Zn concentration. The correlation values between soil-Zn and plant-Zn were of 0.74 (M-3), 0.73 (DTPA), 0.62 (AB-DTPA) and 0.61 (M-1) for corn, and of 0.71 (DTPA), 0.63 (M-1), 0.58 (M-3) and 0.46 (AB-DTPA) for soybean. Thus, the DTPA solution was the most efficient extractant for the determination of bioavailable Zn when both crops are considered together.