Zn In Soil Solution Research Articles

Colloids control the mobilization of released zinc- and cadmium- species in calcite-rich soils

Cadmium (Cd)-bearing sphalerite (SP, ZnS) and smithsonite (SM, ZnCO3) particulate matter (PM) is deposited on soils near carbonate-hosted Zn ore deposits. Whether and how carbonate rocks such as limestone influence the mobility of Cd and Zn in soils is largely unknown. For this reason, we conducted a soil incubation experiment to investigate the chemical and mineralogical changes in soil–soil solution samples, including the occurrence of Cd- and Zn-bearing colloids and nanoparticles. Here the addition of calcite to SP- and SM-spiked soils promoted the formation of Cd- and Zn- bearing nanoparticles and colloids and thus significantly decreased the concentrations of Cd and Zn in soil solutions. Transmission electron microscope and extended X-ray absorption fluorescence spectroscopy showed that the addition of calcite resulted in the formation of Fe-OM-Ca colloids (OM = organic matter), sequestrating Cd and Zn. Furthermore, the release of Ca2+ during the dissolution of calcite promoted the aggregation of colloids and thus decreased the mobility of Cd- and Zn-bearing colloids in the soil column. The addition of calcite also decreased the amount of Cd and Zn released from the dissolution of SP and SM through the formation of calcite nano-layers armoring particles of the SP and SM phases. This study provides new insights into the environmental fate of particulate Cd and Zn in soils around carbonate-hosted Pb-Zn ore deposits. Specifically, it shows that the formation and aggregation of Cd- and Zn-bearing colloids decrease the mobility and bioavailability of both elements.

Biodegradation and effects of EDDS and NTA on Zn in soil solutions during phytoextraction by alfalfa in soils with three Zn levels

In chelator-enhanced Zn phytoremediation studies, it is crucial to understand how the degradable chelators and the competition from other ions influence the concentration of Zn in soil solutions. This study investigated the biodegradability of two chelators (EDDS: Ethylenediamine-N,N′-disuccinic acid, and NTA: Nitrilotriacetic acid) and their effects on the Zn concentration in the soil solution during the growth of alfalfa (Medicago Sativa L.). The chelators were added at four doses (0, 0.5, 2 and 5 mmol kg−1) in soils with varying Zn levels (189, 265 and 1496 mg kg−1). The results showed that the lag phase before EDDS and NTA biodegradation varied from 0 to 7 days in the three soils. EDDS and NTA were completely decomposed within the assessed 57 days regardless of the applied dosage, with a half-life of 1.3–3.0 days in highly Zn-contaminated soil and 4.2–10.8 days in the two other soils. In soil solutions, the change in solubilized Zn was in line with EDDS and NTA degradation kinetics. Cu, Al, Fe and Mn were the main metal ions that competed against Zn for chelation. Besides, Ni competed with Zn in the whole process. Ca did not compete effectively in the three soils, while Mg was a competitor only at the initial stage. Our results show the importance of considering both the biodegradation rate and the competition between the target cation and other elements present in the soil when using chelators to enhance phytoremediation. A 30-day explorative incubation experiment is recommended to evaluate the appropriate application time of chelators and the target Zn exposure time for plants during phytoremediation.

Soil moisture influences performance of selected stabilizing amendments in soil remediation

Various stabilizing amendments are used and tested for immobilization of metals and metalloids in contaminated soils. Although the soil moisture level may fundamentally drive these stabilizing agents' performance, most laboratory studies do not provide consistent data for different moisture regimes. In addition, the possible influence of applied stabilizing materials on the soil's physical and hydraulic properties and associated changes in soil chemistry is virtually unknown. For this reason, this study aimed to investigate the stabilizing potential of two immobilizing agents (amorphous Mn oxide – AMO, and AMO-biochar composite – AMOchar) toward As, Cd, Pb, and Zn in two contaminated soils at two different soil moisture regimes (unsaturated and saturated conditions). At the same time, changes in saturated hydraulic conductivity (Ks), soil swelling, and saturated water content were evaluated. The soil moisture conditions essentially affected all the studied parameters, including both physical and chemical properties. Under the saturated condition, the contents of As, Cd, Pb and Zn in soil solution were elevated compared to the unsaturated condition. The stabilizing effectiveness of the AMO/AMOchar strongly depended on the moisture regime (saturated vs. unsaturated conditions) and type of contaminant based on its binding mechanism in soil. The release of Cd and Zn was reduced by AMO and AMOchar after 10 weeks under both moisture regimes due to an induced pH increase, decreasing the contents of Cd and Zn in soil solution in maximum by 87% (AMOchar, saturated conditions) and 74% (AMO, unsaturated conditions), respectively. Under the saturated conditions, only AMO was effective at immobilizing Pb and As, decreasing their release by 58% and 53%. The application of AMOchar led under full saturation to a significant redox (Eh) drop (minimum value of 181 mV), followed by the dissolution of soil Fe oxides and the associated release of bound Pb and As. As a result, the contents of Pb and As in soil solution increased compared to control by 78% and 248%, respectively. This decline in Eh may be a consequence of the observed AMOchar swelling. However, additional factors, such as changes in the soil microbiology, probably contributed to the overall effect. The study demonstrates the fundamental role of soil moisture content in the stabilizing agents' performance and highlights the need for future interdisciplinary studies aiming at physical/geochemical/biological aspects of soil systems together.

Comparative Response of Two Rice (Oryza sativa L.) Cultivars to Applied Zinc and Manganese for Mitigation of Salt Stress

Soil salinity, together with zinc (Zn) and manganese (Mn) deficiencies, adversely affects rice growth and yield. The comparative salinity stress mitigation response of rice to Zn or Mn remains largely unknown. Rice cultivars, viz. Basmati-515 and KSK-282, were grown in saline soil having electrical conductivity (EC) of 7.5 dS m−1 (as control) parallel to EC 7.5 dS m−1 + Zn 3.5 mg kg−1 and EC 7.5 dS m−1 + Mn 3.5 mg kg−1 treatments in a pot experiment. Application of Zn in saline soil decreased (p < 0.05) sodium (Na+) and chloride (Cl−) concentrations (6% and 26%, respectively) and increased potassium (K+) concentration (25.9%) in leaves compared with the control. The increments in superoxide dismutase (SOD), glutathione reductase (GR), and catalase activities (CAT) reduced salinity-induced oxidative damage which translated into 50.5% and 74% increased membrane stability index (MSI) and relative water content (RWC), respectively. A 5-fold increment of Zn in soil solution ensured its adequate availability for rice which increased SPAD value for an effective photosynthesis to reinforce above ground biomass and grain production. The enhancements in indole-3-acetic acid (46% and 39%) whereas reductions in abscisic acid (18% and 11%) in shoot and root highlighted the Zn-dependent mitigation of salinity stress in both rice cultivars. Ameliorative effect of Mn remained second to Zn despite the increased shoot Mn concentration in KSK-282. Conclusively, both rice cultivars preferred Zn to mitigate salinity; however, KSK-282 responded better through increased antioxidant activities, indole-3-acetic acid biosynthesis, and decreased abscisic acid accumulation.

Nitrogen induced DOC and heavy metals leaching: Effects of nitrogen forms, deposition loads and liming

Atmospheric nitrogen (N) deposition is believed to accelerate dissolved organic carbon (DOC) production and could lead to increased heavy metal mobility into water resources. We sampled intact soil cores from the Isle of Skye with low background N deposition history and having Serpentine rock known for its higher heavy metal concentrations including zinc (Zn), copper (Cu), nickel (Ni) and lead (Pb). The effects of 16 (16kgN) and 32 kg N ha−1 year−1 (32kgN), and liming with 32kgN (32kgN+Lime) on soil solution chemistry and heavy metal mobilization were investigated over the 15-month study. Nitrogen in deposition load was added at five ammonium (NH4+) to nitrate (NO3−) ratios of 9:1, 5:1, 1:1, 1:5 and 1:9 along NO3−dominance. We found significant effects of load on Cu and NH4+/NO3− ratio on pH, DOC and Zn in soil solution. However, under lime and ratio experimental factors, liming significantly influenced pH, DOC, Cu and Pb, and NH4+/NO3− ratio pH, DOC, Ni and Zn whereas interactions between lime and ratio was significant for Ni and Cu. pH and DOC increased with N load, liming and NO3− dominance, and both correlated significantly positively. Liming under NH4+ dominance enhanced DOC production due to supply of base cations in lime. Mobilization of Cu, Ni and Pb was driven by DOC concentrations and, therefore, increased with load, liming and NO3− dominance in deposition. However, in contrast, low pH and high NH4+ dominance was associated with Zn mobilization in soil solution. On the contrary, despite of some patterns, heavy metals in soil HNO3 extracts were devoid of any load, lime and NH4+/NO3− ratio effects. Our study suggests that the effects of N load and forms in deposition on sites with high accumulated loads of metals need to be better quantified through soil solution partitioning models.

You are here: Home » Online First » Volume 15, 2020 - Number 1 » EFFECT OF SUBSTRATE PROPERTIES ON THE MOBILITY OF SELECTED TRACE ELEMENTS IN SOIL AND CONCENTRATIONS IN SHOOTS OF PHALARIS ARUNDINACEA, Carpathian Journal of Earth and Environmental Sciences, February 2020, Vol. 15, No. 1, p. 49 - 56; DOI:10.26471/cjees/2020/015/108 « Back Christin MOSCHNER1, Ulf FEUERSTEIN2, Hermann

Christin MOSCHNER, Ulf FEUERSTEIN, Hermann HEILMEIER, Nazia ZAFFAR & Oliver WICHE - EFFECT OF SUBSTRATE PROPERTIES ON THE MOBILITY OF SELECTED TRACE ELEMENTS IN SOIL AND CONCENTRATIONS IN SHOOTS OF PHALARIS ARUNDINACEA, Carpathian Journal of Earth and Environmental Sciences, February 2020, Vol. 15, No. 1, p. 49 - 56; DOI:10.26471/cjees/2020/015/108

Cadmium and zinc bioaccumulation by Phytolacca americana from hydroponic media and contaminated soils

Hydroponic, greenhouse and field experiments were conducted to explore the potential of pokeweed (Phytolacca americana L.) to accumulate Zn and Cd from nutrient solutions and contaminated soils. The hydroponic results confirmed that this native species is a strong Zn and Cd bioaccumulator that does not experience severe phytotoxicity until quite high root and shoot concentrations, approaching 4000 and 1600 mg kg−1 of Zn, and 1500 and 500 mg kg−1 of Cd, respectively. These high Zn and Cd concentrations were accompanied by increased sulfur and lower manganese in both shoots and roots. However, in field and greenhouse trials with soils historically contaminated by a number of heavy metals including Zn and Cd, concentrations of Zn and Cd in shoots of P. americana reached concentrations less than 30% and 10%, respectively, of those achieved with hydroponics. The main constraint to phytoremediation of soils by P. americana was the low concentrations of Zn and Cd in soil solution. Pretreatment of the metal-contaminated soil by oxalic acid increased soluble Cd and Zn but failed to increase plant uptake of either metal, a possible result of higher solubility of competing metal ions (Cu, Mn) or low bioavailability of Cd and Zn-oxalate complexes.

Assessment of biomass ash applications in soil and cement mortars

The pH-dependent availability and leaching of major and trace elements was investigated for a wide range of biomass ash from different fuels and conversion technologies. A technical and environmental assessment of selected biomass ash for application in soil or cement mortars was performed, using both the total content and leaching of elements. A large variation in biomass ash composition, yet consistent pH dependent leaching patterns were observed for most elements and conversion technologies. Chromium showed a distinct behaviour which was hypothesized to reflect redox conditions during conversion of the biomass.The leaching based approach was found to provide a more realistic assessment of the availability of desired (i.e. nutrients) and undesired elements (i.e. contaminants) in soil systems. When applied to a reference soil at a rate of 2% by weight, the selected biomass ash increased the concentration of particularly Cr, Mo and Zn in soil solution to a level of concern. For cement applications, the release of Ba, Cr and Mo can become of concern during the second life stage, but the release was not attributed to the included biomass ash.Both soil and cement matrixes were found to control the release of elements such as Cu, V and Ni (soil) and As, Cr and Mo (cement) when compared to the released from pure biomass ash, underlining the importance of evaluating the availability and leaching of desired and undesired elements in the application scenario.Given current regulatory criteria, beneficial utilization of biomass ash in cement may be more feasible than in soil, but regulatory criteria based on leaching rather than total content of elements may widen the application potential of biomass ash.

Effects of Cu and Zn Coated Urea on Eh, pH and Solubility of Cu and Zn in Rice Soils

The concentration of Cu (Copper) and Zn (Zinc) decreases upon flooded conditions of rice soil. To assess the effects of flooding and application of Cu and Zn coated urea on changes in Eh, pH and solubility of Cu and Zn, a glasshouse experiment was conducted at Universiti Putra Malaysia. Rice plants (30 days old seedlings of type MR-219) on two soils (riverine and alluvium and marine alluvium) were transplanted. Nine treatments with variable rates and combinations of Cu and Zn coated urea were applied. The sources of fertilizers were copper sulfate and zinc sulfate. Eh values decreased with flooding time in both soils. The changes of Eh values were more negative in control treatments and stabilized after 3 weeks of submergence. The Eh variation was not observed affectively in the treated soils however, soil pH increased with flooding time. During the 3rd week of submergence, pH was neutral (pH 7.0). In both soils, Cu and Zn treated soil showed lower Eh and higher pH values as compared to untreated soil. Concentration of Cu and Zn in soil solution decreased with flooding. The higher Cu and Zn contents in soil were recorded in treated soils. Reduced solubility of Cu and Zn in control soils was related to larger changes in Eh and pH values. Mean comparison with Tukey’s HSD (Honest Significant Difference) test showed that Cu and Zn solubility decreased with decreased Eh and increased pH in the soil solution (p &lt; 0.05%).

Comparison of simple soil-solution extraction techniques for assessing transfer of metals from soil to plant in contaminated soils

An attempt was made to evaluate simple techniques for extraction of soil solution for predicting uptake of Zn, Cu, Ni, Pb and Cd by spinach (Beta vulgaris L. var. All Green) grown on metal contaminated soils under modelling framework. Twenty-eight surface soil samples (0-15 cm) with heterogeneous chemical properties were collected. A pot experiment was conducted using spinach as a test crop. The leachate from experimental pots was collected with the help of plastic container installed below the pots. The 1:2 and 1:5 soil: water ratio was used for soil solutionextraction. The total concentration of Zn, Cu, Ni, Pb, and Cd in soil solution was determined using ICP-MS. Harvested plant sample was analyzed for total Zn, Cu, Ni, Pb, and Cd using ICP-MS. For predicting metal uptake by spinach free ion activity model (FIAM) was used and total metal concentration in soil solution was used as an input of FIAM. Higher concentration of all metal in 1:5 soil-water ratio were recorded than that in 1:2 soil-water ratio. The free ion activity model as a function of total metal concentration in soil solution, as measured by 1:5 soil: water extraction, could explain the variability in metal content in spinach to the extent of 94% for Zn, 67% for Cu, 80% for Ni, 50% for Pb and 75% for Cd, respectively. Extraction of soil with 1:5 soil-water ratio is more efficient and suitable for predicting metal uptake by spinach as compared to that of 1:2 and leachate extraction.

Speciation of Cu, Zn, and Pb in Soil Solutions Extracted from Strongly Polluted Soils Treated with Organic Materials

Speciation of Cu, Zn, and Pb in Soil Solutions Extracted from Strongly Polluted Soils Treated with Organic Materials

Reactivity and effectiveness of traditional and novel ligands for multi-micronutrient fertilization in a calcareous soil.

This study compares the effectiveness of multi-micronutrient formulations containing iron (Fe), manganese (Mn), and zinc (Zn) with traditional (EDTA, DTPA, HEEDTA, and EDDHAm) or novel chelates (o,p-EDDHA, S,S-EDDS, and IDHA) and natural complexing agents (gluconate and lignosulfonate). The stability and reactivity of the formulations were studied on batch experiments with calcareous soil and by speciation modeling. Formulations containing traditional ligands maintained higher Mn but lower Zn concentration in soil solution than the novel ligands. The gluconate and lignosulfonate maintained low concentrations of both Mn and Zn in soil solution. Selected formulations were applied into calcareous soil and their efficacy was evaluated in a pot experiment with soybean. The formulation containing DTPA led to the highest Zn concentration in plants, as well as the formulation containing S,S-EDDS in the short-term, which correlated with its biodegradability. The application of traditional or novel ligands in formulations did not result in sufficient plant Mn concentrations, which was related to the low Mn stability observed for all formulations under moderate oxidation conditions. The results highlight the need to consider the effect of metals and ligands interactions in multi-nutrient fertilization and the potential of S,S-EDDS to be used for Zn fertilization. Furthermore, it is necessary to explore new sources of Mn fertilization for calcareous soils that have greater stability and efficiency, or instead to use foliar fertilization.

Transpiration flow controls Zn transport in Brassica napus and Lolium multiflorum under toxic levels as evidenced from isotopic fractionation

Stable zinc (Zn) isotope fractionation between soil and plant has been used to suggest the mechanisms affecting Zn uptake under toxic conditions. Here, changes in Zn isotope composition in soil, soil solution, root and shoot were studied for ryegrass (Lolium multiflorum L.) and rape (Brassica napus L.) grown on three distinct metal-contaminated soils collected near Zn smelters (total Zn 0.7–7.5%, pH 4.8–7.3). The Zn concentrations in plants reflected a toxic Zn supply. The Zn isotopic fingerprint of total soil Zn varied from −0.05‰ to +0.26±0.02‰ (δ66Zn values relative to the JMC 3-0749L standard) among soils, but the soil solution Zn was depleted in 66Zn, with a constant Zn isotope fractionation of about −0.1‰ δ66Zn unit compared to the bulk soil. Roots were enriched with 66Zn relative to soil solution (δ66Znroot−δ66Znsoil solution=Δ66Znroot–soil solution=+0.05 to +0.2 ‰) and shoots were strongly depleted in 66Zn relative to roots (Δ66Znshoot–root=−0.40 to −0.04 ‰). The overall δ66Zn values in shoots reflected that of the bulk soil, but were lowered by 0.1–0.3 ‰ units as compared to the latter. The isotope fractionation between root and shoot exhibited a markedly strong negative correlation (R2=0.83) with transpiration per unit of plant weight. Thus, the enrichment with light Zn isotopes in shoot progressed with increasing water flux per unit plant biomass dry weight, showing a passive mode of Zn transport by transpiration. Besides, the light isotope enrichment in shoots compared to roots was larger for rape than for rye grass, which may be related to the higher Zn retention in rape roots. This in turn may be related to the higher cation exchange capacity of rape roots. Our finding can be of use to trace the biogeochemical cycles of Zn and evidence the tolerance strategies developed by plants in Zn-excess conditions.

Soil micronutrient availability to crops affected by long-term inorganic and organic fertilizer applications

The effects of mineral and organic fertilization on the contents of Fe, Cu, Zn, Mn, B and Mo in soil and in the soil solution as well as on availability of these elements for crops were investigated in the long-term field trial. The highest contents of Zn, Fe, Mn and Cu in soil and soil solution were observed in the treatment with the lowest pH (NPK). In this same combination the content of B and Mo was the lowest. The concentration of Zn, B and Fe in the soil solution significantly increased under farmyard manure application. Liming significantly decreased contents extractable by 1 mol/L HCl forms of Mn and Zn and significantly increase the content of Mo in the soil. Regardless of fertilization applied, microelement concentrations in the soil solution are sufficient for fulfilling nutritional needs of plants cultivated during the trial.

Contamination of Floodplain Soils along the Wupper River, Germany, with As, Co, Cu, Ni, Sb, and Zn and the Impact of Pre-definite Redox Variations on the Mobility of These Elements

This study demonstrates that floodplain soils of the River Wupper, Germany, are seriously contaminated with metal(loid)s. We used an automated biogeochemical microcosm system allowing controlled variation of redox potential (EH) to assess the impact of pre-definite redox conditions on the dynamics of arsenic (As), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), antimony (Sb), and zinc (Zn) in homogenized soil material taken from an acid floodplain soil. The concentrations of Co, Cu, Mn, Ni, Sb, and Zn in soil solution were low at low EH, possibly due to the precipitation of metal sulfides, and increased with rising EH, presumably caused by their association with dissolved organic carbon (DOC). A significant positive correlation between metal/DOC-ratio and EH indicated that the binding of the metals to DOC shifted from stronger to weaker when EH rose. Decreasing As concentrations with increasing EH in soil solution indicated co-precipitation with Fe(hydr)oxides and/or oxidation of more soluble As(III) to less soluble As(V) during oxidation. The other studied elements seemed not to co-precipitate with newly formed Fe(hydr)oxides when EH rose, possibly due to the prevailing low pH. In the future, the specific role of DOC and sulfur chemistry on metal(loid) dynamics should be elucidated more fully, and similar studies should be conducted with additional frequently flooded soils worldwide to verify these results.

Speciation of Cu and Zn in soil solution in a long-term fertilization experiment

Abstract The changes of the concentration of Cu and Zn in the soil solution and the percentage of particular forms of these elements in the soil solution were investigated in the long-term fertilization experiment. The soil solution was obtained following the vacuum displacement method. Speciation of copper and zinc ions was determined with MINTEQA2 for Windows software. The results of the investigation indicated that exclusive mineral fertilization (NPK) caused an increase of Cu and Zn concentration in the soil solution. Organic fertilization (FYM) resulted in a decrease of Cu and an increase of Zn concentration in the soil solution. Liming limited mobility of both analysed elements. The results of speciation analysis showed that regardless of the fertilization mode, the organo-mineral complexes are the main form of Cu occurring in soil solution. The percentage of Cu-DOC complexes ranges from 76.5 to 85.2% of the total concentration of Cu in the soil solution. The particular forms of copper can be sorted depending on the percentage in the soil solution as follows: Cu-DOC&gt;Cu2+&gt;Cu-CO3. The main form of Zn in the soil solution are active Zn2+ ions. The share of Zn2+ in total zinc concentration in the soil solution ranged from 76.9% to 86.4%. Forms of zinc in the soil solution can be arranged with regard to their percentage as follows: Zn2+&gt;Zn-DOC&gt;ZnCl+&gt;ZnHCO3+.

Elevated CO2 concentration increase the mobility of Cd and Zn in the rhizosphere of hyperaccumulator Sedum alfredii

The effects of elevated CO2 on metal species and mobility in the rhizosphere of hyperaccumulator are not well understood. We report an experiment designed to compare the effects of elevated CO2 on Cd/Zn speciation and mobility in the rhizosphere of hyperaccumulating ecotype (HE) and a non-hyperaccumulating ecotype (NHE) of Sedum alfredii grown under ambient (350μll(-1)) or elevated (800μll(-1)) CO2 conditions. No difference in solution pH of NHE was observed between ambient and elevated CO2 treatments. For HE, however, elevated CO2 reduced soil solution pH by 0.22 unit, as compared to ambient CO2 conditions. Elevated CO2 increased dissolved organic carbon (DOC) and organic acid levels in soil solution of both ecotypes, but the increase in HE solution was much greater than in NHE solution. After the growth of HE, the concentrations of Cd and Zn in soil solution decreased significantly regardless of CO2 level. The visual MINTEQ speciation model predicted that Cd/Zn-DOM complexes were the dominant species in soil solutions, followed by free Cd(2+) and Zn(2+) species for both ecotypes. However, Cd/Zn-DOM complexes fraction in soil solution of HE was increased by the elevated CO2 treatment (by 8.01% for Cd and 8.47% for Zn, respectively). Resin equilibration experiment results indicated that DOM derived from the rhizosphere of HE under elevated CO2 (HE-DOM-E) (90% for Cd and 73% for Zn, respectively) showed greater ability to form complexes with Cd and Zn than those under ambient CO2 (HE-DOM-A) (82% for Cd and 61% for Zn, respectively) in the undiluted sample. HE-DOM-E showed greater ability to extract Cd and Zn from soil than HE-DOM-A. It was concluded that elevated CO2 could increase the mobility of Cd and Zn due to the enhanced formation of DOM-metal complexes in the rhizosphere of HE S. alfredii.

Comparative tolerance of Pinus radiata and microbial activity to copper and zinc in a soil treated with metal-amended biosolids

A study was conducted to evaluate the effects of elevated concentrations of copper (Cu) and zinc (Zn) in a soil treated with biosolids previously spiked with these metals on Pinus radiata during a 312-day glasshouse pot trial. The total soil metal concentrations in the treatments were 16, 48, 146 and 232 mg Cu/kg or 36, 141, 430 and 668 mg Zn/kg. Increased total soil Cu concentration increased the soil solution Cu concentration (0.03-0.54 mg/L) but had no effect on leaf and root dry matter production. Increased total soil Zn concentration also increased the soil solution Zn concentration (0.9-362 mg/L). Decreased leaf and root dry matter were recorded above the total soil Zn concentration of 141 mg/kg (soil solution Zn concentration, >4.4 mg/L). A lower percentage of Cu in the soil soluble + exchangeable fraction (5-12 %) and lower Cu(2+) concentration in soil solution (0.001-0.06 μM) relative to Zn (soil soluble + exchangeable fraction, 12-66 %; soil solution Zn(2+) concentration, 4.5-4,419 μM) indicated lower bioavailability of Cu. Soil dehydrogenase activity decreased with every successive level of Cu and Zn applied, but the reduction was higher for Zn than for Cu addition. Dehydrogenase activity was reduced by 40 % (EC40) at the total solution-phase and solid-phase soluble + exchangeable Cu concentrations of 0.5 mg/L and 14.5 mg/kg, respectively. For Zn the corresponding EC50 were 9 mg/L and 55 mg/kg, respectively. Based on our findings, we propose that current New Zealand soil guidelines values for Cu and Zn (100 mg/kg for Cu; 300 mg/kg for Zn) should be revised downwards based on apparent toxicity to soil biological activity (Cu and Zn) and radiata pine (Zn only) at the threshold concentration.

The profile distribution of Zn and the Zn2+-pH isotherms of savanna alfisols irrigated with untreated wastewater in Northern Nigeria

The distribution of total and labile Zn, and the Zn2+-pH isotherms of arable urban fields were evaluated to determine the fate of Zn under long-term Zn loading from untreated wastewater irrigation. At the three sites, total Zn concentration in the surface layer had attained pollution level in the topsoil, but the concentration of total, mobile and the potentially labile Zn decreased rapidly with depth, suggesting limited movement within the profiles. The soils were spiked with Zn(NO3)2 solution at the pH range of 4-8 and allowed to react for 25 days, results indicated that the soil attained maximum Zn adsorption at pH ≥ 7.5. Free cationic Zn2+ activities accounted for between 69 and 88% of soluble Zn while Zn-inorganic complexes accounted for just about 1-5% of the total dissolved Zn in soil solution as compared to the Zn-fulvate complex that ranged from 11 to 22% of total soluble Zn. The linear -log Zn2+-pH isotherms had slopes that approached the solubility isotherm of hopeite, (Zn3(PO4)2 especially at pH ≥ 7.0. Given the increasing tendency of pH and the attendant Zn loading of the soils due to irrigation with untreated wastewater, precipitation of Zn-solid phases having solubility similar to hopeite will likely control Zn2+ activities and availability in the soils in the long-term.

Influence of soil fertilization on concentration of microelements in soil solution of sandy soil

The study was carried out to asses the influence of soil mineral fertilization, manure application and soil liming on changes in the concentration of microelements (B, Cu, Fe, Mn and Zn) in soil solution. The tests were performed on samples of sandy soil collected from long-term fertilization experiments being conducted on lessive soil of the granulometric structure of clayish sand. Soil solution was prepared with the suction method. The concentration of microelements in soil solution was determined by means of the ICP method. The results showed an increase in Fe, Mn, Zn and Cu and a decrease in B and Mo in soil solution when soil was fertilized with nitrogen. The concentration of microelements in soil solution was not significantly influenced when soil was fertilized with phosphorous and potassium. Liming had a significant effect on a decrease in the concentration of Fe, Mn, Zn and Cu and an increase in B and Mo in soil solution. Soil application of manure significantly increased the concentration of microelements in soil solution.