Preface.- Contributors.- List of Abbreviations.- Section 1: Basic Principles: Introduction.-Sources of Heavy Metals and Metalloids in Soils.- Chemistry of Heavy Metals and Metalloids in Soils.- Methods for the Determination of Heavy Metals and Metalloids in Soils.- Effects of Heavy Metals and Metalloids on Soil Organisms.- Soil-Plant Relationships of Heavy Metals and Metalloids.- Heavy Metals and Metalloids as Micronutrients for Plants and Animals.-Critical Loads of Heavy Metals for Soils.- Section 2: Key Heavy Metals And Metalloids: Arsenic.- Cadmium.- Chromium and Nickel.- Cobalt and Manganese.- Copper.-Lead.- Mercury.- Selenium.- Zinc.- Section 3: Other Heavy Metals And Metalloids Of Potential Environmental Significance: Antimony.- Barium.- Gold.- Molybdenum.- Silver.- Thallium.- Tin.- Tungsten.- Uranium.- Vanadium.- Glossary of Specialized Terms.- Index.

Heavy metals in soils : trace metals and metalloids in soils and their bioavailability

Long-term impact of irrigation with sewage effluents on heavy metal content in soils, crops and groundwater : a case study

A comprehensive review of the sequential extraction schemes for metal fractionation in environmental samples (i.e., sediment, soil, sewage sludge, fly ash, etc.) is presented. The review contains more than 400 references and covers principally the literature published over the last decade. The use of each reagent involved in these schemes is looked at critically, and guidelines for their selectivity and extraction capacity are given. The operational character of these schemes is emphasised. Topics such as comparability between sequential extraction schemes of widespread use, harmonisation, acceleration, validation, etc. are addressed and future developments outlined.

Chemical sequential extraction for metal partitioning in environmental solid samples.

Preparation and catalytic properties of cationic and anionic clays

The remarkable complexity of soil and its importance to a wide range of ecosystem services presents major challenges to the modeling of soil processes. Although major progress in soil models has occurred in the last decades, models of soil processes remain disjointed between disciplines or ecosystem services, with considerable uncertainty remaining in the quality of predictions and several challenges that remain yet to be addressed. First, there is a need to improve exchange of knowledge and experience among the different disciplines in soil science and to reach out to other Earth science communities. Second, the community needs to develop a new generation of soil models based on a systemic approach comprising relevant physical, chemical, and biological processes to address critical knowledge gaps in our understanding of soil processes and their interactions. Overcoming these challenges will facilitate exchanges between soil modeling and climate, plant, and social science modeling communities. It will allow us to contribute to preserve and improve our assessment of ecosystem services and advance our understanding of climate-change feedback mechanisms, among others, thereby facilitating and strengthening communication among scientific disciplines and society. We review the role of modeling soil processes in quantifying key soil processes that shape ecosystem services, with a focus on provisioning and regulating services. We then identify key challenges in modeling soil processes, including the systematic incorporation of heterogeneity and uncertainty, the integration of data and models, and strategies for effective integration of knowledge on physical, chemical, and biological soil processes. We discuss how the soil modeling community could best interface with modern modeling activities in other disciplines, such as climate, ecology, and plant research, and how to weave novel observation and measurement techniques into soil models. We propose the establishment of an international soil modeling consortium to coherently advance soil modeling activities and foster communication with other Earth science disciplines. Such a consortium should promote soil modeling platforms and data repository for model development, calibration and intercomparison essential for addressing contemporary challenges.

/pdf/modeling-soil-processes-review-key-challenges-and-new-4a1lz21a4f.pdf

Modeling Soil Processes: Review, Key Challenges, and New Perspectives

While many workers have utilized various reagents for sequential extraction of soil trace metals, few studies have examined the order of extraction for key steps in the sequential procedure In this study, several sequences involving both adsorbed and structural (occluded) metal extractants were evaluated to determine the most appropriate sequential methodology for extracting different forms of Cu, Fe, and Mn For "specifically adsorbed" metals, Pb(NO3)2 and CH3COOH were used The results showed that the former reagent extracted less Cu, Mn, and Fe and was probably more specific in replacing metals covalently bound to adsorption sites Lead nitrate was therefore placed before CH3COOH extraction in the sequence Chao's NH2OHHCl reagent and K4P2O7, used for Mn oxide and organic metal removal, respectively, were found to solubilize significantly different amounts of Cu and Mn depending on sequence, with K4P2O7 extracting more metal when used first As NH2OH • HCl has little effect on organic metals, it should be used before K4P2O7 Noncrystalline and crystalline Fe compounds are solubilized next, using a variety of reagents, and residual (silicate lattice) metals are dissolved in the final step A nine-step sequential method is proposed to characterize trace metals in agricultural, polluted, and wasteamended soils Additional Index Words: sequential extraction, trace metal fractionation, soil Cu, soil Mn, soil Fe View complete article To view this complete article, insert Disc 4 then click button8

Effect of Sequence in Extraction of Trace Metals from Soils

Crystal growth theory was applied to describe edge sites of phyllosilicates. Three face config- urations were found to exist. One face has one tetrahedral site per tetrahedral sheet and two octahedral one-coordinated sites per crystallographic area ac sin/3, where a and c are layer dimensions and/3 is the angle between them. The other two faces are similar except that they have one less octahedral site which is replaced by one Si'v-O-A1 vt site in this same ac sin/3 area. A transfer of bonding energy from the remaining octahedral site to the Si'v-O-A1 w site is believed to neutralize all edge charge on faces containing these latter sites at normally encountered pHs (pH 3-9). A similar charge rearrangement along the edges results in an apparent decrease in the permanent charge of the mineral with an increase in edge area. On the basis of such an analysis, lath-shaped illite can be described as a very fine grained dioctahedral mica in which the apparent deficient occupancy of the octahedral sheet, presence of excess water, and measurable cation-exchange capacity may in part be the result of a large ratio of edge area to total volume, with no other chemical or structural change in the mica layers. The increasing importance of edge charge relative to layer charge produces erroneous formulae for 2:1 phyllosilicates in very fine grained samples containing fewer than 2 of 3 octahedral sites occupied by cations, on the basis of a 22-charge half cell.

Analysis and Implications of the Edge Structure of Dioctahedral Phyllosilicates

It is known that PO 4 is retained by soils through ligand exchange, i.e., inner sphere complexation, but the mechanism for SO 4 adsorption at the mineral-water interface has been in debate. By studying the effects of ionic strength on ion adsorption, it is possible to distinguish between inner and outer sphere ion surface complexes. This study was conducted to evaluate ionic strength effects on S04 and PO 4 adsorption on γ-Al 2 O 3 and kaolinite at varying solution pH (3-11), and to infer SO 4 and PO 4 adsorption mechanisms at the mineral-water interface. The adsorption of SO 4 on γ-Al 2 O 3 and kaolinite decreased monotonically with increasing solution pH and was markedly reduced by increasing the concentration of background electrolyte. On the other hand, PO 4 adsorption on γ-Al 2 O 3 and kaolinite increased from pH 3 to 4 and decreased from pH 6 to 11, with an adsorption plateau between pH 4 and 6. Effects of change in ionic strength on PO 4 adsorption varied with pH. At low pH, PO 4 adsorption demonstrated a slight decrease with increasing ionic strength, whereas at high pH, P04 adsorption increased slightly with increasing ionic strength, resulting in a crossover point where there was no ionic strength effect. The triple-layer model (TLM) was applied to model the adsorption of SO 4 and PO 4 with both inner and outer sphere complexes using the FITEQL 3.1 computer program. Sulfate adsorption was better modeled by assuming outer sphere complex formation, while P04 adsorption was better modeled by assuming inner sphere complex formation.

Ionic Strength Effects on Sulfate and Phosphate Adsorption on γ‐Alumina and Kaolinite: Triple‐Layer Model

Soil properties indicative of shrink-swell potential were studied for 12 soils encompassing several parent materials in Virginia. Soils are rated from moderate to very high shrink-swell potential. The mineralogy classes, soil series, and (parent materials) examined include: smectitic-Iredell (hornblende gneiss), Jackland and Waxpool (diabase); vermiculitic-Kelly (thermal shale); kaolinitic-Cecil (granite gneiss) and Davidson (diabase); and mixed-Carbo and Frederick (limestone), Craven and Peawick (Coastal Plain sediments), and Mayodan and Creedmoor (Triassic sandstones). Soil properties measured were swell index, coefficient of linear extensibility (COLE), particle-size distribution, cation-exchange capacity (CEC), liquid limit, plasticity index (PI), and day mineralogy. Soils with estimated high or very high shrink-swell potential were clayey, with clay contents exceeding 60%. These expansive soils also exhibited high CEC (>15 cmol c kg -1 soil), high liquid limits (>70), and appreciable swelling 2:1 mineral content (> 15% montmorillonite + 1/2 vermiculite on whole-soil basis). An expansive soil rating system, termed the Expansive Soil Index (ESI), was developed using the soil properties most correlated with shrink-swell potential, The sum of swelling 2:1 minerals, swell index, liquid limit, and CEC gave ESI ratings for each soil series. The higher the ESI, the greater the shrink-swell potential. Where less-detailed information is required, such as for initial feasibility studies, an ESI consisting of liquid limit and CEC is recommended. Finally, the soils were grouped into risk categories based on parent material to allow for classification of similar soils into the ESI rating system. Soils with restricted drainage formed from mafic rocks, carbonate parent material, and metamorphic shales are at high risk for expansive soil behavior.

L. W. Zelazny

Papers

Effect of Sequence in Extraction of Trace Metals from Soils

Analysis and Implications of the Edge Structure of Dioctahedral Phyllosilicates

Ionic Strength Effects on Sulfate and Phosphate Adsorption on γ‐Alumina and Kaolinite: Triple‐Layer Model

An expansive soil index for predicting shrink-swell potential.

Effects of Manure Amendment on Soil Chemical Properties and Hydrous Oxides1