Metal‐Associated Forms and Speciation in Biosolid‐Amended Oxisols

Abstract

The objective of this study was to determine the effects of pH and ionic strength on the distribution and speciation of zinc (Zn), copper (Cu), and cadmium (Cd) in surface soil samples from two Brazilian Oxisols amended with biosolids. Soils and biosolids were equilibrated in an experimental dual‐chamber diffusion apparatus that permits the soils and biosolids to react through a solution phase via diffusion across a membrane. After equilibrium was reached, soil and biosolids samples were sequentially fractionated to identify various solid forms of Zn, Cu, and Cd. Metal concentrations in the solution phase were determined and mass balance calculated. Equilibrating pH had no major effect on Cu solubility from biosolids and, at pH range from 4 to 7, most Cu remained in the biosolids. Soluble Zn and Cd concentration increased with decreasing pH because of the increased solubility of the biosolids. Copper and Zn were primarily associated with the residual fraction and Fe oxides in one soil, but were primarily associated with chemically unstable fractions, or adsorbed to the surface of oxides, in the other soil. In both soils, Cd was primarily associated with readily bioavailable fractions. The effect of pH on the metal distribution was more evident than the ionic strength effect. Free ions were the predominant metal species in solution, especially at lower pH values.     

Correlation Between Chemical Element Contents in Tree Rings and Soils

The annual growth rings of ten trees and the soils near the tree roots were sampled from the mining ares of lead-and zinc-dominant metals in the Xixia Mountain,Nanjing,for the determination of chemical element contents.The study results showed that the elemental contents in the tree rings were correlated with those in the soils,i.e.,the elemental contents in the tree rings increased with those in the soils,even in the cases of different environments and different tree species.Therefore,a time-concentration sequence could be set up on the basis of determining the elemental contents in the successive annual growth rings of trees to qualitatively reflect the annual variations of relevant elements in the soils,and a time-concentration sequence of elemental contents in soils could also be established in terms of related model to reproduce the dynamic changes of the surroundings.     

Productivity and Chemical Composition of Tomato and Cucumber Plants Growing in Nickel‐Polluted Soils Fertilized with Biona‐312

Abstract: The effect of ion‐exchange substrate Biona‐312 additions to nickel (Ni)–polluted soil on yield and mineral composition of cherry tomato and cucumber was evaluated. The plants were grown on the following media: untreated soil (the control series) and soil with added Ni (40 and 100 mg of Ni kg^?1, respectively) as well as Biona‐312 (2 and 5% mass additions, respectively). In the presence of 40 mg of Ni kg^?1 of soil, the plant yield did not change significantly, whereas in conditions of 100 of mg Ni kg^?1, it decreased significantly. Biona‐312 application on Ni‐polluted soil increased the productivity of both species. The content of macronutrients in the plant biomass varied depending on the growth stage, Ni level, and Biona‐312 dose. For both species, higher Ni content was observed in the aboveground organs than in roots, but tomato contained more Ni than cucumber. Biona application reduced the Ni content in plant biomass of both species after being introduced into soil with a higher Ni level.     

Productivity and Chemical Composition of Tomato and Cucumber Plants Growing in Natural Soils Fertilized with Biona‐312

This study was carried out to evaluate the effect of small additions of ion exchange substrate, Biona‐312, to soil on the yield and mineral composition of cherry tomato cv. ‘Koralik’ and cucumber cv. ‘Hermes F₁.’ The test plants were grown under greenhouse conditions and subjected to 0, 2, and 5% (mass) Biona‐312 doses introduced into the soil. The study results showed that Biona‐312 introduced into soil significantly increased the yield of the test species at the flowering and fruiting stage. Soil enrichment with 2 and 5% Biona additions generally increased the nitrogen–phosphorus–potassium (N‐P‐K) content in tomato and cucumber organs at the flowering and fruiting stage with parallel magnesium (Mg) and calcium (Ca) content decrease. Introduction of nutrients together with the ion exchange substrate did not cause negative effects of overfertilization, and thus the ion exchange substrate can be recommended as a fertilizer in tomato and cucumber cultivation.     

Fractionation of Zinc in Paddy Soils of China

The rice fields in China amount to 25.4 million hectares of which low yield paddy soils areabout 26％(Xu,1981;Xiao,1981).One of the most important causes of low yield is the defi-ciency in nutrients including zinc.Zinc deficiency usually occurs in calcareous paddy soils withpH>6.5(Zhu and Liu,1981).And the availability of zinc in calcareous paddy soils is lowerthan that in neutral and acid paddy soils.     

Estimation of Plant‐Available Nitrogen in Soils using Rapid Chemical and Biological Methods

The relationships between potential laboratory indices for plant‐available nitrogen (N) and the plant N uptake in a pot experiment with ryegrass were assessed for 13 mineral soils and 2 peat soils. The methods included aerobic soil incubation, soil incubation in a bioreactor, hot potassium chloride (KCl)–extractable mineral N, 0.01 M calcium chloride (CaCl₂)–extractable N, and N loss at heating. The indices for total plant‐available N accounted for 63–93% of the variance in N uptake in a statistical analysis with all soils (n = 15) and 27–89% for the mineral soils (n = 13). Most indices were not a direct quantitative measure of the plant N uptake. The N mineralization indices accounted for 57–86% of the variance in N mineralization for all soils and 5–50% for the mineral soils. Hot KCl‐extractable mineral N and 0.01 M CaCl₂–extractable N were the most promising rapid indices for plant‐available N.     

Influence of Dissolved Organic Matter on the Solubility of Heavy Metals in Sewage‐Sludge‐Amended Soils

Abstract

Sewage‐sludge‐amended soils generally contain elevated levels of organic matter and heavy metals compared to control soils. Because organic matter is known to complex with heavy metals, the solubility behavior of the organic matter in such soils may exert a significant influence on the solubility of the metals. Little is known about such a process. Using batch experiments in which the solubility of organic matter in a heavily sludge‐amended soil was artificially manipulated, we show that the solubilities of the heavy metals copper (Cu), nickel (Ni), and lead (Pb) show a strong positive relationship to the solubility of organic matter, particularly at high pH. The results suggest that under field conditions, spatiotemporal variations in the solid–solution partitioning of organic matter may have a bearing on the environmental significance (mobility and bioavailability) of these heavy metals.     

Study on Model of Correlation Between Chemical Element Contents in Tree Rings and Soils near Tree Roots

The chemical element contents in tree rings are correlated with those in the soils near the tree roots,The results in the present study showed that the correlation between them could be described using the following logarithmic linear correlation model:lgC‘(Z)=a(Z) b(Z)lgC(Z).Therefor,by determining the chrono-sequence C(Z,t),where Z is the atomic number and t the year,of elemental contents in the annual growth rings of trees,we could get the chrono-sequence C‘(Z,t) of elemental contents in the soil,thus inferring the dynaminc variations of relevant elemental contents in the soil.     

Prediction of Chemical Element Contents in Soils

Assuming that the regularity for the dynamic changes of the chrono-sequences of chemical element contents in tree rings follows a k-order constant coefficient differential equation and substituting the differential with the difference,we could obtain the inferred value ym k 1 by the formula:ym k 1=c1ym 1 c2Ym 2 …ckym kEach coefficient ci in the formula may be ascertained by use of the measured data in the chrono-sequences,Extending the chrono-sequences on the assumption that the regularity of dynamic changes wouldn‘t change in the near future,the contents of chemical elements in the soils may be predicted in terms of a logarithmic linear correlation model.Also,this extension method could be used for the reproduction of the contents of chemical elemets in soils during different periods of time in the past.     

Phosphorus Fractionation in Soils and Wastewater Sorbent Materials as an Indicator of Material Specific and Storage‐Dependant Availability

Abstract

Wastewater treatment with reactive filters and recycling the phosphorus (P)‐saturated materials as fertilizers in plant production is a suitable concept for a sustainable society. The objective of the present study was to evaluate the ability of the Hedley P fractionation scheme to separate different P fractions, including inorganic and organic P, in soils and sorbent materials used to reduce the P content of waste water. An additional aim was to determine changes in P fractions after storage for 8 months under different humidity regimes. This was to evaluate whether extractability of P is dependent on storage conditions between sorption of P and the subsequent use of the sorbent materials as P fertilizers. This study is the first one showing that in sorbent materials used for treatment of wastewater, the Hedley fractionation scheme separated Ca phosphates in the HC1 extract from Al and Fe phosphates in the NaOH extract. The different fractions could also be used to characterize soils of different origins, to separate liming treatments, and to approximately document soil P fertility, but could not assess differences in soil P status caused by different P fertilization in a single year. No significant influence of moisture regimes during storage on resin‐exchangeable P was detected. This increases the suitability of the studied sorbent materials for recycling P from wastewater to agricultural crops, because it indicates that plant availability of sorbed P does not change drasticaIly during the studied storage conditions.     

Nitrogen Mineralization in Soils Treated with Fly Ash–Amended Wastewater Sludges

Abstract

Alkaline‐treated wastewater sludges with varying doses of fly ash were added to a clay soil at rates equivalent to 100 t (dry weight) raw sludge ha^?1 soil, and the variations in ammonium, nitrate, and total nitrogen contents were monitored throughout an incubation period of 360 days at 28°C. The results showed that inhibition of organic nitrogen mineralization occurred in soil amended with fly ash–containing sludge during the first 90 days of incubation. After the total incubation period of 360 days, the inhibition effects of alkaline sludge amendments totally disappeared. In fact, mineralization was enhanced in alkaline pasteurized sludges containing 80% and 120% fly ash. The overall results indicated that application of sludges amended with fly ash may prolong the use (3 to 6 months) of nitrogen from the organic nitrogen pool in sludge.     

Distribution and Availability of Heavy Metals in Raw and Acidulated Phosphate Rock–Amended Soils

Abstract

The effectiveness of the application of raw (PR‐1), and partially acidulated phosphate rock (PR), at 25% (PR‐25) and at 50% (PR‐50), was investigated to reduce extractability and plant uptake of Pb, Cd, Cu, Ni, and Zn in three calciorthids soils.Furthermore, the effects of soil treatments on metal extractability were evaluated by sequential extraction. Similarly, such effects were assessed on the phytoavailability of metals of maize (Zea mays L.) through a pot experiment. Water‐soluble and exchangeable metal fractions (the bioavailable fractions) were influenced distinctively by PR treatments and soil properties. In addition, decrease of soluble and exchangeable metal fractions was compensated by an increase in metal extracted from other fractions. Most bioavailable soil metals correlated significantly with their associated level in plant tissue. Finally, plant metal uptake decreased with PR treatments, suggesting that PR application was likely to be effective in controlling metal immobilization in these soils.     

Evaluation of Distribution and Chemical Associations between Cobalt and Manganese in Soils by Continuous‐Flow Sequential Extraction

Abstract

In this study, a strong association between cobalt (Co) and manganese (Mn) in different geochemical soil phases (fractions) was evaluated using a continuous‐flow sequential extraction technique employing a modified Tessier extraction scheme. With the flow system, detailed extraction profiles of Co and Mn in soils could be obtained by plotting concentrations of the elements extracted against extraction time (plots referred to as extractograms). Extractograms may be used as an indicator of whether the elements dissolving in the same extraction step are closely associated, or are merely extractable with the same reagent. From the soil samples studied, the coincidence of Co and Mn peaks seems to indicate a close association of these elements in the exchangeable, reducible, and oxidizable fractions. Analysis of flow extraction data suggested that the association between Co and Fe is not as strong as reported in previous studies based on the statistical analysis of batch fractionation data.     

Drinking‐Water Treatment Residual Effects on the Phosphorus Status of Field Soils Amended with Biosolids,Manure, and Fertilizer

Abstract

Concerns about surface water pollution with phosphorus (P) from biosolids and manures are prompting land application guidelines that limit residual application rates to those based on crop‐P removals (typically, no more than 2 Mg ha^?1). Such rates are so low that the beneficial recycling of residuals is seriously threatened. Greater application rates [i.e., nitrogen (N) based] require judicious selection of residuals (low soluble P contents) and/or soil amendments, such as drinking‐water treatment residuals (WTRs) to control soluble P concentration. Although in the short term, WTR is effective in reducing soluble P levels, field studies to evaluate the stability of WTR‐immobilized P are scarce. The initial objective of this study was to determine the effects of WTR on P losses to surface and groundwater from Florida sand amended with different P sources (biosolids, manure, and inorganic fertilizer) applied at P‐ and N‐based rates. However, this objective could not be pursued to its logical conclusion because of severe flooding of the field 17 months after amendment application. The flooding appears to have compromised the treatments (moved soil and associated amendments across plots), which forced early termination of the experiment. Measurements taken after the flooding, however, provided a unique opportunity to assess the usefulness of WTR in controlling P solubility following severe flooding of WTR‐amended plots. Soluble P values measured from WTR‐amended A horizon plots were significantly lower than the plots without WTR amendment throughout the study. Phosphorus‐specific measurements in the Bh horizon suggest that excessive P leaching apparently occurred in the plots without WTR amendment and the control plots, whereas very little or no P leaching occurred in the WTR‐amended plots. Thus, despite extensive hurricane‐induced flooding of the fields, the WTR was able immobilize P and prevent excessive P leaching. We conclude that WTR could reduce offsite P transport, which will lower P loads into nutrient‐sensitive surface water systems, and that WTR‐immobilized P is stable even under severe flooding conditions.     

Bioavailability of Heavy Metals in Biosolids‐Amended Soil

Abstract

A single biosolids application was made to 1.5×2.3 m confined plots of a Davidson clay loam (Rhodic Kandiudult) in 1984 at 0, 42, 84, 126, 168, and 210 Mg ha^?1. The highest biosolids application supplied 750 and 600 kg ha^?1 of Cu and Zn, respectively. Corn (Zea mays L.), from 1984 to 2000, and radish (Raphanus sativus L.) and romaine lettuce (Lactuca sativa var. longifolia), from 2001 to 2004, were grown at the site to assess heavy‐metal bioavailability. Extractable (0.005 diethylenetriamine (DTPA) and Mehlich 1) Cu and Zn were determined on 0 to 15‐cm depth samples from each plot. Corn yield increased with biosolids rate each year until 1993 to 1997, when yield decreased with biosolids rate because of phytotoxicity induced by low (<5.0) soil pH. The corn yield reduction was reversed between 1998 and 2000 upon raising the soil pH to approximately 6.0 by limestone addition following the 1997 season. Between 2001 and 2004, radish and lettuce yields were either not affected or slightly increased with biosolids rate, even as soil pH declined to below 5.5. Plant‐tissue metal concentrations increased with biosolids rate and as pH declined but were always within the normal range of these crops. Mehlich 1 and DTPA extractable metals increased linearly with biosolids rate. Extractability of Cu and Zn decreased approximately 50% over the past 20 years despite a decrease in soil organic matter concentration and greater than 95% conservation of the metals.     

Dissolution and Fractionation of Calcium—Bound and Iron—and Aluminum—Bound Humus in Soils

This paper deals with the development of a sequential extraction method to separate the Ca-bound and Fe-and Al-bound humus from soils.First,comparative analyses were carried out on dissolution of synthetic organo-mineral complexes by different extractants,i.e.0.1M Na4P2O7,0.1M NaOH 0.1M Na4P2O7 mixture,0.1M NaOH,0.5M (NaPO3)6 and 0.5M neutral Na2SO4.Among the five extractants,0.1M NaOH 0.1M Na4P2O7 mixture was the most efficient in extracting humus from various complexes.0.5M Na2SO4 had a better specificity to Ca than 0.5M (NaPO3)6,by only extracting Ca-bound humus without destorying Fe-and Al-bound organo-mineral complexes.Then sequential extractions first with 0.5M Na2SO4 and then with 0.1M NaOH 0.1M Na4P2O7 mixture were applied to a series of soil samples with different degrees of base saturation.The cations were dominated by Ca in the 0.5M Na2SO4 extract and by Al in the 0.1M NaOH 0.1M Na4P2O7 mixture.The sequential extraction method can efficiently separate or isolate Ca-bound and Fe-and Al-bound humus from each other.     

Adsorption and Desorption of Exogenous Rare Earth Elements in Soils:Ⅰ. Rate and Forms of Rare Earth Elements Sorbed

Adsorption and desorption of exogenous rare earth elements (REE) in soils were studied.Results showed that soils had strong adsorbability for REE and the rate of adsorption of REE was over 95% of the added REE in these tests.The characteristics of adsorption isotherms corresponded well with the both Freundlich and Temkin equations,but deviated from the Langmuir equation.The adsorption of REE tended to increase with the rising of soil pH.A sequential extraction method used for studing the desorption and distribution of REE sorbed in soils are also discussed.     

Surface Chemical Properties of Colloids in Main Soils of China

Surface chemical properties of soil colloids are the important factor affecting soil fertility and genesis.To provide scientific basis for soil genetic classification,promotion of soil fertility and reasonable fertilizqation,the specific surface area and electric charge of soil colloids in relation to clay minerals and organic matter are further discussed on the basis of the results obtained from the studies on surface chemical properties of soil colloids in five main soils of China.Results from the studies show that the effect of clay minerals and organic matter on the surface chemical properties of soil colloids is very complicated because the siloxane surface,hydrated oxide surface and organic matter surface do not exist separately,but they are always mixed together and influenced each other.The understanding of the relationship among clay minerals,organic matter and surface chemical properties of soil colloids depends upon further study of the relevant disciplines of soil science,especially the study on the mechanisms of organo-mineral complexes.     

Heavy‐Metal Concentration of Sewage‐Contaminated Water and Its Impact on Underground Water,Soil, and Crop Plants in Alluvial Soils of Northwestern India

Abstract

Heavy‐metal concentration in underground and surface water, soil, and crop plants growing in farmers' fields near the industrial city of Ludhiana, Punjab, India, that receive irrigation with water contaminated with sewer and untreated industrial effluents was studied. The concentrations of lead (Pb), chromium (Cr), cadmium (Cd), and nickel (Ni) in sewage‐contaminated water were 18, 80, 88, and 210 times higher than in shallow handpump water, and 21, 133, 700, and 2200 times higher than in deep tube‐well water, respectively. The concentrations of Cd and Ni in shallow handpump underground water were significantly higher than in deep tube‐well underground water. The concentrations of Pb, Cr, Cd, and Ni in deep tube‐well water were 0.017, 0.003, 0.0002, and 0.0002 mg L^?1, respectively. Soils irrigated with sewage‐contaminated water had higher electrical conductivity, cation exchange capacity, organic carbon (C), and clay content but had lower pH and calcium carbonate content compared to soils irrigated with deep underground water. The concentrations of diethylenetriamine pentaacetic acid (DTPA)–extractable Pb, Cr, Cd, and Ni in soils irrigated with sewage‐contaminated water were 1.8, 35.5, 3.6, and 14.3 times higher, and total concentrations of these heavy metals were 1.5, 3.0, 3.7, and 2.2 times higher than that in soils irrigated with deep underground water. The mean concentrations of Pb, Cr, Cd, and Ni in crop plants growing on soils irrigated with sewage‐contaminated water were 4.88, 4.20, 0.29, and 3.99 mg kg^?1, which were 1.2, 2.1, 8.7, and 1.9 times higher than in plants irrigated with deep tube‐well water, respectively. The amounts of potentially toxic metals were significantly and positively correlated with cation exchange capacity and organic C content and negatively correlated with soil pH. In conclusion, long‐term accumulation of toxic metals in soils and their uptake by crop plants has a high potential for phytotoxicity as well as for entering into the food chain. The findings also suggest contamination of underground shallow drinking water through leaching of some highly mobile metals.     

Phosphorus and Potassium Transformations in Soil Amended with Enriched Compost and Chemical Fertilizers in a Wheat–Soybean Cropping System

India imports large amounts of rock phosphate (RP) and potassium (K) fertilizers from other countries; hence, research priorities have been directed toward finding alternative sources of phosphorus (P) and K fertilizers. This study focuses on the transformations of P and K in soil amended with RP and waste mica–enriched compost. The enriched compost had greater total P, K, calcium (Ca), magnesium (Mg), micronutrients, and biological properties than ordinary compost. In a wheat–soybean rotation, application of 5 t ha^?1 enriched compost along with 50% of the recommended rate of inorganic fertilizer resulted in increased concentrations of saloid P, iron (Fe) P, aluminum (Al) P, Ca-P, occluded P, water-soluble K, exchangeable K, and nonexchangeable K over unfertilized plots. In addition, plots that received enriched compost had greater microbial biomass and phosphatase activities than unfertilized plots. Thus, enriched compost could be an alternative source of water-soluble P and K fertilizers for crop production.