Characterization of physical and chemical properties of spent foundry sands pertinent to beneficial use in manufactured soils

Abstract As of 2007, of the 2,000 United States foundries, 93% produce ferrous or aluminum castings, generating 9.4 million tons of non-hazardous spent foundry sand (SFS) annually. Only 28% of the SFS is beneficially used. The U.S. EPA Resource Conservation Challenge identifies SFS as a priority material for beneficial use, with soil blending as a potential reuse option. The objectives of this work were to measure: (1) select chemical and physical properties important to soil quality and function and (2) total and soluble elemental content of 39 SFSs, in order to evaluate SFS suitability as a component in manufactured soils. Total elemental concentration of the SFS was lower than natural background soil levels for most elements analyzed, suggesting limited to no contamination of the virgin sand during metal casting. Pore water elemental concentrations were generally below detection. However, both total and soluble elemental content indicate a potential contribution of plant nutrients. Lettuce (Lactuca sativa) planted in SFS mixtures had a median germination rate of 96.9% relative to the control. Blending SFS at varying ratios with other materials will allow “tailoring” of a manufactured soil’s chemical and physical properties to meet specific growing needs. The SFS organic carbon, clay, and plant nutrient content are benefits of SFS that may make them good candidates as manufactured soil components

Adsorption of Cd, Cu, Ni and Zn in tropical soils under competitive and non-competitive systems

The adsorption of heavy metals in soils affects their behavior in the environment and their bioavailability to plants. The knowledge of the adsorption mechanisms in competitive systems allows a more realistic evaluation of the metals' behavior in the soil than the single metal adsorption. The objectives of this study were (i) to evaluate Cd, Cu, Ni, and Zn adsorption in 14 surface samples (0-0.2 m) of representative soils of the Brazilian humid-tropical region, in competitive and non-competitive systems, and (ii) to establish metal affinity sequences for each soil, based in the maximum adsorption capacity (MAC) estimated by the Langmuir model. The Rhodic Eutrudox, the Kandiudalf Eutrudox, the Arenic Hapludalf, the Arenic Hapludult and the Typic Argiudoll had the highest metals' adsorption capacity, whereas the Typic Quartzipsamment and the sandy-textured Arenic Hapludult had the lowest values. In general, the MAC values for metals were lower in the competitive than in the non-competitive system. In the non-competitive system, the most common affinity sequence was Cu > Zn > Ni > Cd, whereas the most common sequence was Cu > Cd > Zn > Ni in the competitive system. In general, the Langmuir model fitted well the adsorption data of metals on the studied soils.A adsorção de metais pesados em solos afeta seu comportamento e biodisponibilidade às plantas. O conhecimento dos mecanismos de adsorção em sistemas competitivos permite uma avaliação mais realista do comportamento dos metais no solo do que estudos com adsorção de cada metal, isoladamente. Os objetivos desse trabalho foram: (i) avaliar a adsorção de Cd, Cu, Ni e Zn em amostras superficiais (0-0,2 m) de 14 solos representativos da região tropical úmida, em sistema competitivo e não-competitivo, e (ii) estabelecer sequências de afinidade metálica para cada solo, com base nos valores de capacidade máxima de adsorção (CMA) dos metais estimados por meio do modelo de Langmuir. O Rhodic Eutrudox, o Kandiudalfic Eutrudox, o Arenic Hapludalf (Alf2), o Arenic Hapludult (Ult2) e o Typic Argiudoll apresentaram elevadas capacidades de adsorção dos metais, ocorrendo o inverso para o Typic Quartzipsamment e para o Arenic Hapludult textura arenosa. No geral, a CMA dos metais aos solos foi menor no sistema competitivo. A sequência de afinidade mais comumente encontrada no sistema não-competitivo foi Cu > Zn > Ni > Cd. No sistema competitivo, a sequência foi Cu > Cd > Zn > Ni. Em geral, o modelo de Langmuir simulou de maneira satisfatória a adsorção dos metais nas amostras de solo

Characterization of physical and chemical properties of spent foundry sands pertinent to beneficial use in manufactured soils

Abstract As of 2007, of the 2,000 United States foundries, 93% produce ferrous or aluminum castings, generating 9.4 million tons of non-hazardous spent foundry sand (SFS) annually. Only 28% of the SFS is beneficially used. The U.S. EPA Resource Conservation Challenge identifies SFS as a priority material for beneficial use, with soil blending as a potential reuse option. The objectives of this work were to measure: (1) select chemical and physical properties important to soil quality and function and (2) total and soluble elemental content of 39 SFSs, in order to evaluate SFS suitability as a component in manufactured soils. Total elemental concentration of the SFS was lower than natural background soil levels for most elements analyzed, suggesting limited to no contamination of the virgin sand during metal casting. Pore water elemental concentrations were generally below detection. However, both total and soluble elemental content indicate a potential contribution of plant nutrients. Lettuce (Lactuca sativa) planted in SFS mixtures had a median germination rate of 96.9% relative to the control. Blending SFS at varying ratios with other materials will allow “tailoring” of a manufactured soil’s chemical and physical properties to meet specific growing needs. The SFS organic carbon, clay, and plant nutrient content are benefits of SFS that may make them good candidates as manufactured soil components

Risk characterization of spent foundry sands in soil-related applications

Spent molding sand is generated at about 2000 foundries in the U.S. when the sand can no longer be reclaimed within the foundry. Interest in beneficial use, rather than disposal of spent foundry sand (SFS), grew in recent years as the cost of landfilling increased and the potential benefit of using SFS in agriculture and horticulture became increasingly apparent. Thus, USDA-ARS researchers and the U.S. EPA's Office of Solid Waste, and researchers at The Ohio State University cooperated to conduct a risk assessment for beneficial use of SFS, and to develop guidance for such use. The available literature on SFS was reviewed and a program of sampling and comprehensive analysis of SFS was undertaken. The sample sets included foundries which cast iron, steel, or aluminum, and generated SFSs which contained low levels of potentially toxic trace elements and organic compounds. Data from these SFSs were evaluated using a pathway risk assessment approach, and it was concluded that most could be beneficially used due to high levels of copper and zinc commonly found in those sands. While most foundries use silica sand, it was also suggested that olivine sands not be beneficially used in soil-related applications, as they contain elevated levels of nickel which may present a phytotoxicity risk in acidic soils. Overall, however, the trace element concentrations in spent sands from iron, steel, and aluminum foundries were not unlike those found in U.S. soils. This guidance document recommends that SFSs with trace elements concentrations below the 95th percentile concentration of background U.S. soils can be safely applied to land or used in manufactured soils. Furthermore, none of the measured organic compounds were present at levels which would comprise excessive risk to humans or environmental receptors. The compounds present were largely biodegradable and mixing SFS in soils would promote natural biodegradation of these compounds

Risk characterization of spent foundry sands in soil-related applications

Spent molding sand is generated at about 2000 foundries in the U.S. when the sand can no longer be reclaimed within the foundry. Interest in beneficial use, rather than disposal of spent foundry sand (SFS), grew in recent years as the cost of landfilling increased and the potential benefit of using SFS in agriculture and horticulture became increasingly apparent. Thus, USDA-ARS researchers and the U.S. EPA's Office of Solid Waste, and researchers at The Ohio State University cooperated to conduct a risk assessment for beneficial use of SFS, and to develop guidance for such use. The available literature on SFS was reviewed and a program of sampling and comprehensive analysis of SFS was undertaken. The sample sets included foundries which cast iron, steel, or aluminum, and generated SFSs which contained low levels of potentially toxic trace elements and organic compounds. Data from these SFSs were evaluated using a pathway risk assessment approach, and it was concluded that most could be beneficially used due to high levels of copper and zinc commonly found in those sands. While most foundries use silica sand, it was also suggested that olivine sands not be beneficially used in soil-related applications, as they contain elevated levels of nickel which may present a phytotoxicity risk in acidic soils. Overall, however, the trace element concentrations in spent sands from iron, steel, and aluminum foundries were not unlike those found in U.S. soils. This guidance document recommends that SFSs with trace elements concentrations below the 95th percentile concentration of background U.S. soils can be safely applied to land or used in manufactured soils. Furthermore, none of the measured organic compounds were present at levels which would comprise excessive risk to humans or environmental receptors. The compounds present were largely biodegradable and mixing SFS in soils would promote natural biodegradation of these compounds

Applications of Fertilizer Cations Affect Cadmium and Zinc Concentrations in Soil Solutions and Uptake by Plants

A pot experiment was conducted to study changes over time of Cd and Zn in soil solution and in plants. Radish was grown in a soil which had been contaminated with heavy metals prior to 1961. Constant amounts of a fertilizer solution (NH4NO3, KNO3) were added daily. Soil solution was obtained at intervals by displacement with water. The cumulative additions of small amounts of fertilizers were made equal to the plants' requirements at the final harvest but were found to exceed them during most of the experiment. Excess fertilizers caused substantial increases of major (K, Ca, Mg) and heavy-metal (Cd, Zn) ions in soil solutions and a decrease in soil pH, probably due to ion-exchange mechanisms and the dissolution of carbonates. Uptake of Cd and Zn into leaves was correlated with the mass flow of Cd (adjusted r = 0.798) and Zn (adjusted r2 = 0.859). Uptake of K, Ca and Mg by the plants was independent of their concentrations in solution. It is concluded that, in order to study effects of plants on heavy-metal availability and obtain soil solution that has not been altered by fertilizer ions, nutrients must be added according to the needs and growth of the plants. This could be achieved by linking fertilizer additions to the rate of transpiration, as nutrient uptake and transpiration were closely correlated in this experiment