Availability of Cd,Ni and Zn to Ryegrass in Sewage Sludge-Treated Soils at Different Temperatures

A pot experiment to compare the availability of Cd, Ni and Znto ryegrass (Lolium perenne L.) was conducted at 15 and 25 °C. For this purpose, three ratesof sewage sludge (0, 10 and 50 t ha^-1) were applied in aloamy sand (LS) and a clay loam (CL). Heavy metal availabilityassessed by soil extractions with 0.05 M CaCl₂ and the organic matter content were monitored during a period of twoyears, while uptake by ryegrass was monitored over one year after addition of the sludge. The concentrations of Cd and Ni in both the ryegrass and the soil extracts increased significantly, during the first year, especially at 50 t ha^-1. However, in the second year metal availability reached a plateau. During the first year, in the ryegrass Znconcentrations did not show an increase, but in the soil CaCl₂-extracted Zn increased. During the same period,the organic matter content decreased rapidly, especially at25 °C, in the first year and much more slowly in thesecond, giving a total decrease of 16%. Temperature had a marked effect on metal availability; both soil extracts andplant samples from the 25 °C treatment had greater concentrations of Cd, Ni and Zn than those at 15 °C. This may be attributed to the organic matter, which decomposedmore rapidly at 25 °C. Moreover, soil-plant transfercoefficients (Tc) of the metals were significantly higher at 25 °C than at 15 °C, with Cd showing the greatest difference, followed in decreasing order by Zn and Ni.     

Determination of the Residual Metal Binding Characteristics of Soils Polluted by Cd and Pb

Four soils contaminated by Pb-Zn mining, Pb-Zn smelting, sewage sludge application, and clay pigeon shooting, respectively, were evaluated for their ability to attenuate relatively high concentrations of supplied Cd and Pb. The retention characteristics of the polluted soils and ‘background’-unpolluted soils for Cd and Pb, were assessed by batch adsorption experiments and equilibrium dialysis titration of the soil organic component. From the sorption data it was observed that the mining polluted and sewage sludge treated soils showed no significant change in Cd affinity when compared to the unpolluted soils. However, for Pb, the reduction in the slopes in the isotherms of the sludge treated and shot over soils were significant when compared to the background soils – indicating a reduced affinity for Pb. The Cd and Pb complexation capacities of the organic component were reduced in the mining, smelter and shot over soil compared to their respective background soils. However, the complexation capacity for Cd of the sludged soil increased from 1.01 µmol Cd g^-1 of organic matter to 4.38 µmol Cd g^-1 of organic compared to the background soil, but, the stability constant of the organo-metal complex formed was lower (6.05 cf. 6.85).     

The transfer of cadmium from sewage-sludge amended soils into the edible components of food crops

Water, Air, & Soil Pollution - The application of sewage sludge to soils used for the production of food crops represents a potential means by which human dietary exposures to Cd may be...     

Ascorbic acid and the behavioral response to haloperidol: implications for the action of antipsychotic drugs

Haloperidol, a widely used antipsychotic drug, was tested for its ability to block the behavioral response to amphetamine and to elicit catalepsy in rats treated with saline or ascorbic acid (1000 milligrams per kilogram of body weight). By itself, ascorbic acid failed to exert significant behavioral effects, but it enhanced the antiamphetamine and cataleptogenic effects of haloperidol (0.1 or 0.5 milligrams per kilogram). These results, combined with a growing body of biochemical evidence, suggest that ascorbic acid plays an important role in modulating the behavioral effects of haloperidol and related antipsychotic drugs.     

The flux of Cd,Cu, Pb and Zn in mining polluted soils

The monitoring of heavy metal deposition onto soils surrounding old Pb-Zn mines in two locations in the UK has shown that relatively large amounts of Cd, Pb, Zn and, in one case, Cu are entering the soil annually. Small particles of ore minerals in windblown mine tailings were found to be contributing up to 1.46 g m^?2 yr^?1 of Pb, 1.41 g m^?2 yr^?1 of Zn and 0.027 g m^?2 yr^?1 of Cd. However, when these inputs from bulk deposition are compared with the concentrations of the same metals within the soil profiles it is apparent that relatively little long-term accumulation is occurring. Metals are being lost from the soil profiles, probably through leaching. A calculated relative retention parameter gave values that ranged from 0.01 to 0.17 for Cd, 0.11 to 0.19 for Zn, 0.32 to 0.63 for Cu and over 1 for Pb. These relative retention values were found to follow the order of electronegativity of the elements concerned: Pb>Cu>Zn>Cd. Distribution coefficient (Kd) values quantifying the adsorptive capacity of the mine soils for Cd and Pb showed marked differences for the two metals (12 to 69 cm³ g^?1 for Cd and 14 to 126 cm³ g^?1 for Pb) and may, in part, account for the two to one hundred-fold variation in the relative retention parameter for the different metals within these soils.     

Chemical Principles of Environmental Pollution,B.J. Alloway and D.C. Ayres

Water, Air, &; Soil Pollution -     

Complexation of Copper by Sewage Sludge-derived Dissolved Organic Matter: Effects on Soil Sorption Behaviour and Plant Uptake

The complexation of Cu by sewage sludge-derived dissolved organic matter (SSDOM) is a process by which the environmental significance of the element may become enhanced due to reduced soil sorption and, hence, increased mobility. The work described in this paper used an ion selective electrode procedure to show that SSDOM complexation of Cu was greatest at intermediate pH values because competition between hydrogen ions and Cu for SSDOM binding sites, and between hydroxyl ions and SSDOM as Cu ligands, was lowest at such values. Batch sorption experiments further showed that the process of Cu complexation by SSDOM provided an explanation for enhanced desorption of Cu from the solid phase of a contaminated, organic matter-rich, clay loam soil, and reduced adsorption of Cu onto the solid phase of a sandy loam soil. Complexation of Cu by SSDOM did not affect uptake of Cu by spring barley plants, when compared to free ionic Cu, in a sand-culture pot experiment. However, it did appear to lead to greater biomass yields of the plant; perhaps indicating that the Cu-SSDOM complex had a lower toxicity towards the plant than the free Cu ion.     

Territoriality and the origin of slave raiding in leptothoracine ants

The slave-raiding behavior of Harpagoxenus canadensis closely resembles the territorial behavior of its host species, Leptothorax muscorum. Of primary importance is the discovery that both species of ants recruit nest mates into battle using an alarm-recruitment system which is a probable evolutionary precursor of more specialized forms of slave-raiding recruitment. The behavior of these species supports the hypothesis that slave raiding in leptothoracine ants evolved from territorial behavior.     

Distribution and Mobility of Trace Elements in Soils and Vegetation Around the Mining and Smelting Areas of Tharsis, Ríotinto and Huelva, Iberian Pyrite Belt, SW Spain

Trace elements may present an environmental hazard in the vicinity of mining and smelting activities. However, the factors controlling their distribution and transfer within the soil and vegetation systems are not always well defined. Total concentrations of up to 15,195 mg . kg ^–1 As, 6,690 mg . kg^–1 Cu, 24,820 mg . kg^–1 Pb and 9,810 mg . kg^–1 Zn in soils, and 62 mg . kg^–1 As, 1,765 mg . kg^–1 Cu, 280 mg . kg^–1 Pb and 3,460 mg . kg ^–1 Zn in vegetation were measured. However, unusually for smelters and mines of a similar size, the elevated trace element concentrations in soils were found to be restricted to the immediate vicinity of the mines and smelters (maximum 2–3 km). Parent material, prevailing wind direction, and soil physical and chemical characteristics were found to correlate poorly with the restricted trace element distributions in soils. Hypotheses are given for this unusual distribution: (1) the contaminated soils were removed by erosion or (2) mines and smelters released large heavy particles that could not have been transported long distances. Analyses of the accumulation of trace elements in vegetation (median ratios: As 0.06, Cu 0.19, Pb 0.54 and Zn 1.07) and the percentage of total trace elements being DTPA extractable in soils (median percentages: As 0.06%, Cu 15%, Pb 7% and Zn 4%) indicated higher relative trace element mobility in soils with low total concentrations than in soils with elevated concentrations.