L. M. Shuman

Mobility of Zn, Cd and Pb in soils as affected by poultry litter extract—I. leaching in soil columns

Application of poultry litter to cropland may increase metal mobility, because the soluble organic ligands in poultry litter can form water-soluble complexes with metals. In this study, one uncontaminated soil and two metal-contaminated soils were sampled. A portion of the uncontaminated soil was amended with Zn, Pb, and Cd at rates of 400, 200, and 8 mg kg(-1), respectively. Packed soil columns were leached with H2O, EDTA, CaCl2, and poultry litter extract (PLE) solutions separately. No leaching of Zn, Cd, and Pb with the PLE was found in the uncontaminated soil. The retention of PLE-borne Zn indicated the potential for Zn accumulation in the soil. A large portion of the metals was leached from the metal-amended soil, and EDTA solubilized more Zn, Cd, and Pb than CaCl2 and PLE. In the metal-contaminated soils, the leaching of Zn and Cd with PLE was consistently larger than that for CaCl2, indicating that these metals were mobilized by organic ligands. The PLE did not mobilize Pb in these soils. The utilization of poultry litter in metal-contaminated soils might accelerate the movement of Zn and Cd in soil profiles.

Heavy Metal Movement In Metal-contaminated Soil Profiles

Heavy metal movement in soil profiles is a major environmental concern because even slow transport through the soil may eventually lead to deterioration of groundwater quality. In this study, three metal-contaminated soils (Fuquay, Dothan, and Clarendon) were selected from cropland where a high-meta

Redistribution of forms of zinc, cadmium and nickel in soils treated with EDTA

Abstract Organic amendments are often added to soils in the form of waste materials which increase the soluble organic ligands in soil. To study the interaction of these soluble organics with metals in soil, Ethylenediaminetetraacetic acid (EDTA) can be used as a model compound for natural organics. The addition of EDTA to soil may alter the physicochemical forms of metals in soil because of its strong chelating capacity. In this work, samples of eight agricultural soils collected in Georgia were spiked with soluble salts of Zn, Cd, and Ni in proportions of 75.9, 1.62, and 4.30 mg kg−1, respectively. Both natural and metal-amended soils were treated with Na2-EDTA (disodium ethylenediamine tetraacetate) solution at amounts of 0, 1.0 and 2.0 g kg−1. After five months incubation in a greenhouse, the soil samples were fractionated into exchangeable (EXC), organic matter (OM), Mn oxide (MNO), amorphous Fe oxide (AFEO), crystalline Fe oxide (CFEO), and residual (RES) fractions. The added Zn was distributed among all fractions in the soils, and added Cd and Ni were found predominantly in the EXC and OM fractions with some of the added Ni occurring in the RES fraction. Increasing the amounts of EDTA significantly raised Zn concentrations in the EXC fraction in both natural and metal-amended soils, and the EDTA also increased Ni and Cd concentrations in the EXC fraction of the metal-amended soils. The results suggested that added EDTA enhanced the solubility of these metals in these soils. The OM-fraction metals decreased with increasing amounts of EDTA, except for Ni in the natural soils. The increase in Zn and Cd associated with the EXC fraction may have been related to solubilization of metals from the OM fraction by EDTA. In the metal-amended soils, EDTA not only removed Ni from the OM fraction, but also from the MNO, AFEO and CFEO fractions, and redistributed it into the EXC fraction. Based on relative percent, Cd in the EXC fraction was higher than Zn, while Ni in this fraction was lowest. This suggests that the order of solubility was: Cd>Zn>Ni for metals added to soils, but when EDTA was present, added Ni may be more vulnerable to solubilization than added Zn and Cd.

Effect of organic waste amendments on cadmium and lead in soil fractions of two soils

Abstract Certain organic soil amendments have been found to ameliorate metal toxicity to plants. A study was undertaken to determine the effects of organic amendments on cadmium (Cd) and lead (Pb) distribution among soil fractions. Two soils (fine‐textured and coarse‐textured) were amended with five organic waste materials or commercial humic acid (HA) with and without 5 mg Cd kg‐1 or 300 mg Pb kg‐1, incubated, and fractionated using a sequential extraction technique. The added Cd and Pb were found mainly in the organic matter (OM) fraction, although significant amounts were in the exchangeable (EXC) fraction for the sandy Norfolk soil. Spent mushroom compost (SMC) and HA lowered Cd in the EXC fraction for both soils and raised Cd in the OM fraction for the sandy Norfolk soil. The SMC and HA lowered Pb in the EXC and OM fractions and raised Pb in the manganese oxide (MnO), amorphous Fe oxide (AFeO) and the crystalline Fe oxide (CFeO) fractions. Poultry‐litter amendment caused higher Cd and Pb in the EXC f...

Cadmium forms and plant availability in compost-amended soil

Organic matter amendments to metal-contaminated soil can have an ameliorative effect due to increased surface area and an increase in the number of specific adsorption sites. A greenhouse experiment was conducted where composted biosolids were added at 0, 100, and 300 tons ha− 1 and a Cd salt was added at 0, 5, 10, 20, and 50 mg kg− 1 to a Southeastern Piedmont soil. Corn (Zea mays L.) was grown for 42 days and plant weights and cadmium (Cd) content was measured. Soil Cd was extracted according to a sequential fractionation procedure to extract operationally-defined forms of the metal. The CEC of the soil and the organic matter content increased with biosolid additions, but soil pH remained stable. Phytotoxicity was greatly reduced by addition of biosolids, especially at the medium rate of 10 mg kg− 1. Cadmium content of the plants was decreased from 105 to 30 mg kg− 1 by the biosolid additions at the 10 mg Cd kg− 1 rate. The decrease in phytotoxicity and in plant Cd was attributed to a redistribution of Cd from the water soluble and exchangeable fractions to the organic fraction, which decreased the plant availability. The results of this study indicate that composted biosolid amendments can be useful in decreasing Cd uptake by plants from contaminated soil and may bring about an increase in plant growth.

Effect of rice variety on zinc, cadmium, iron, and manganese content in rhizosphere and non‐rhizosphere soil fractions

Abstract In research on selecting rice (Oryza sativa L.) cultivars that are resistant to metal toxicity, an experiment was carried out with the objective of determining the effects of rice cultivars with differing oxidizing powers on the forms of metals in the rhizosphere soil. Four rice varieties were grown for 40 d in 3 soils which had differing amounts of iron (Fe) and manganese (Mn) oxides. The rhizosphere soil was kept separate from the non‐rhizosphere using nylon mesh “rhizobags”;. The soils were treated with either 5 mg/kg cadmium (Cd) or 20 mg/kg zinc (Zn). At the end of the experiment the soils were analyzed using a sequential fractionation scheme for five forms of Cd, Zn, Fe, and Mn. The rhizosphere soil was lower in pH (p=0.14) and P (p=0.05) than the non‐rhizosphere soil. Iron in the Mn oxide fraction was ten times higher in the rhizosphere as opposed to the non‐rhizosphere soil while the rhizosphere soil Mn was lower in this fraction. Cadmium in the rhizosphere soil was increased in both the ...

Effect of organic waste amendments on zinc adsorption by two soils

Two soils (fine and coarse textured) were amended with five organic wastes or humic acid. One adsorption experiment was carried out at 1 mmol L[sup [minus]1] Zn and at pH levels from 4 to 8. A second experiment was at pH 6 and 0 to 4 mmol/L[sup [minus]1] Zn. The greatest variation in Zn adsorption among organic treatments came at pH 6, with a lesser range for the fine textured soil (pH 5--6) and a wider range for the sandy soil (pH 5--7). Adsorption followed a two-site Langmuir model, and maxima were higher for the finer textured soil compared with the sandy soil. Adsorption maxima were not changed by the organic wastes for the fine textured soil, but all were increased over the controls for the sandy soil. Zinc adsorption for poultry litter was lower than the control for the sandy soil. Industrial sewage sludge and humic acid increased Zn adsorption more than did commercial compost, spent mushroom compost, and cotton litter. It was concluded that organic materials have more influence on Zn adsorption for sandy soils than for fine textured soils and that most materials will increase Zn adsorption, whereas those with high soluble C can decrease Zn adsorption.

Mobility of Zn, Cd and Pb in soils as affected by poultry litter extract—II. Redistribution among soil fractions

The application of poultry litter to metal-contaminated soils may influence metal leaching and distribution of metals among soil fractions. Soil columns (one uncontaminated control, one metal-amended, and two metal-contaminated soils) were leached with H2O, CaCl2, EDTA, and poultry litter extract (PLE) solutions. After leaching, the soil samples in the columns were sequentially extracted for water soluble (WS), exchangeable (EXC), organic matter (OM), Mn oxide (MNO), amorphous Fe oxide (AFEO), crystalline Fe oxide (CFEO) and residual (RES) fractions. The OM fraction showed high retention for Zn from the PLE. The EDTA redistributed Zn, Cd and Pb from the EXC, OM and MNO fractions to the WS fraction. The PLE usually solubilized more Zn and Cd from the EXC fraction than CaCl2. Neither PLE nor CaCl2 mobilized Pb. The application of poultry litter on metal-contaminated soils might cause Zn and Cd redistribution from the EXC to the WS fraction and enhance metal mobility.

Zinc Forms and Plant Availability in a Compost Amended Soil

Compost can be used to remediate metal-contaminatedsites because it binds metals and reduces metal uptakeby plants. A greenhouse experiment was conducted totest the effectiveness of compost to remediate Zntoxicity to plants and to determine its effect on zinc(Zn) distribution among operationally defined forms. Cecil soil (Typic kanhapludults) was amendedwith 0 to 5000 mg kg-1 Zn and biosolid compost at0, 100, and 300 tons ha-1, and then corn (Zea mays L.) was planted. After 42 days of growthplants were weighed and analyzed for Zn concentration. Soil was analyzed for Mehlich 1-extractable Zn andfractionated by a sequential extraction procedure forforms of Zn. Compost lowered soil pH while increasingCEC, exchangeable hydrogen and percent carbon. Concentrations of Mehlich 1-extractable Zn weredecreased by compost addition. Compost additionsdecreased plant Zn concentration and allowed moreplant survival with toxic levels of soil Zn. Compostamendment redistributed Zn from the water soluble andexchangeable fractions to the manganese oxide andamorphous iron oxide fractions, which shows a changein form of Zn from more plant available to less plantavailable. Biosolid compost soil amendments decreaseplant availability of Zn making it less toxic toplants even where it decreases soil pH, which wouldtend to have the opposite effect.

Comparison of mehlich‐1 and mehlich‐3 extractable soil boron with hot‐water extractable boron

Abstract The standard hot water extractant for soil boron (B) was compared with two extractants currendy in use by routine soil testing laboratories, Mehlich‐1 (M‐1) and Mehlich‐3 (M‐3). If routine extractants could be used for B, it would save the time and expense required for a separate extraction. Six states (Delaware, Maryland, Virginia, North Carolina, South Carolina, and Georgia) each selected 100 soil samples sent by growers to their State laboratories which were analyzed for routine properties (pH, P, K, Ca, Mg, and organic matter) and B by M‐1 or M‐3. The samples were then analyzed for hot‐water B (HWB) using a plastic pouch procedure and inductively‐coupled plasma emission spectrometry (ICP). M‐3 extracted more B than M‐1, and the correlation coefficients for M‐3 B with HWB were higher (r = 0. 82∗∗) than were M‐l with HWB (r = 0. 74∗∗). Correlations of soil properties with M‐l and M‐3 B were higher than with HWB, but none were notable with two exceptions. Extractable Ca was positively correlated...