Chemodynamics of chromium reduction in soils: implications to bioavailability.

Chromium toxicity in soils can be mitigated by reduction of Cr(VI) to Cr(III) which is influenced by the presence of free Cr(VI) species in soil solution, and the supply of protons and electrons. In this study, the effects of Cr(VI) adsorption (i.e.

Using biochar for remediation of soils contaminated with heavy metals and organic pollutants.

Soil contamination with heavy metals and organic pollutants has increasingly become a serious global environmental issue in recent years. Considerable efforts have been made to remediate contaminated soils. Biochar has a large surface area, and high capacity to adsorb heavy metals and organic pollutants.

Concomitant reduction and immobilization of chromium in relation to its bioavailability in soils.

In this study, two carbon materials [chicken manure biochar (CMB) and black carbon (BC)] were investigated for their effects on the reduction of hexavalent chromium [Cr(VI)] in two spiked [600 mg Cr(VI) kg(-1)] and one tannery waste contaminated [454 mg Cr(VI) kg(-1)] soils. In spiked soils, both the rate and the maximum extent of reduction of Cr(VI) to trivalent Cr [Cr(III)] were higher in the sandy loam than clay soil, which is attributed to the difference in the extent of Cr(VI) adsorption between the soils. The highest rate of Cr(VI) reduction was observed in BC-amended sandy loam soil, where it reduced 452 mg kg(-1) of Cr(VI), followed by clay soil (427 mg kg(-1)) and tannery soil (345 mg kg(-1)).

Lead immobilization and bioavailability in microbial and root interface.

A range of both soluble and insoluble phosphate (P) compounds have been used to immobilize Pb in solution and soil. However, these compounds have limitations because of low solubility or leaching of P. Phosphate solubilizing bacteria (PSB) can be used to enhance the solubility of insoluble P compounds.

Role of organic amendment application on greenhouse gas emission from soil.

Globally, substantial quantities of organic amendments (OAs) such as plant residues (3.8×10(9) Mg/yr), biosolids (10×10(7) Mg/yr), and animal manures (7×10(9) Mg/yr) are produced. Recycling these OAs in agriculture possesses several advantages such as improving plant growth, yield, soil carbon content, and microbial biomass and activity.

Carbon storage and soil CO2 efflux rates at varying degrees of damage from pine wilt disease in red pine stands.

We evaluated the carbon (C) storage and soil CO2 efflux rates of red pine (Pinus densiflora S. et Z.) stands damaged by pine wilt disease (PWD) in Korea.

Sorption-bioavailability nexus of arsenic and cadmium in variable-charge soils.

In this work, the nexus between sorption and bioavailability of arsenic (As) and cadmium (Cd) as affected by soil type, soil pH, ageing, and mobilizing agents were examined. The adsorption of As and Cd was examined using a number of allophanic and non-allophanic soils which vary in their charge components. The effect of pH and ageing on the bioavailability of As and Cd was examined using spiked soils in a plant growth experiment.

Recycled water sources influence the bioavailability of copper to earthworms.

Re-use of wastewaters can overcome shortfalls in irrigation demand and mitigate environmental pollution. However, in an untreated or partially treated state, these water sources can introduce inorganic contaminants, including heavy metals, to soils that are irrigated. In this study, earthworms (Eisenia fetida) have been used to determine copper (Cu) bioavailability in two contrasting soils irrigated with farm dairy, piggery and winery effluents.

Heavy metal toxicity to bacteria - are the existing growth media accurate enough to determine heavy metal toxicity?

A new minimal medium was formulated considering the limitations of the existing media for testing heavy metal sensitivity to bacteria. Toxicity of cadmium and copper to three bacteria was investigated in the new medium and compared with three other media commonly used to study the effect of the toxic metals. Based on speciation data arrived at using ion-selective electrodes, the available free-metal concentration in solution was highest in the MES-buffered medium.

Effect of soil type on distribution and bioaccessibility of metal contaminants in shooting range soils.

Shooting ranges from Department of Defence sites around Australia were investigated for extent of metal contamination. Shooting range soils contained concentrations ranging from 399 to 10,403 mg/kg Pb, 6.57 to 252 mg/kg Sb, 28.

DDT remediation in contaminated soils: a review of recent studies.

Over the past few decades significant progress has been made in research on DDT degradation in the environment. This review is an update of some of the recent studies on the degradation and biodegradation pathways of DDT and its metabolites, particularly in soils. The latest reports on human toxicity shows that DDT intake is still occurring even in countries that banned its use decades ago.

Improving bioavailability of phosphorous from cattle dung by using phosphatase immobilized on natural clay and nanoclay.

The high P retention of acidic Andisols makes necessary to increase our technological approaches in pasture management in the animal system production. Here, we evaluated the clay- or nanoclay-acid phosphatase complexes for improving phosphorus mineralization from degraded cattle dung. We implemented an immobilization mechanism of acid phosphatase (AP) using natural clays (allophanic and montmorillonite) and nanoclays as support materials.

Environmental monitoring of the role of phosphate compounds in enhancing immobilization and reducing bioavailability of lead in contaminated soils.

Lead is a highly toxic element and forms stable compounds with phosphate, which is commonly used to immobilize Pb in soils. However, few studies have monitored the long-term stability of immobilized Pb, which is a critical factor in determining the effectiveness of the in situ stabilization technique. Both soluble and insoluble phosphate compounds were tested for Pb immobilization, and its subsequent mobility and bioavailability in a contaminated soil from a shooting range.

Concomitant rock phosphate dissolution and lead immobilization by phosphate solubilizing bacteria (Enterobacter sp.).

This paper examines the potential value of phosphate solubilizing bacteria (Enterobacter cloacae) in the dissolution of rock phosphate (RP) and subsequent immobilization of lead (Pb) in both bacterial growth medium and soils. Enterobacter sp. showed resistance to Pb and the bacterium solubilized 17.

Comparative value of phosphate sources on the immobilization of lead, and leaching of lead and phosphorus in lead contaminated soils.

The mobility and bioavailability of lead (Pb) in soils can be mitigated by its immobilization using both soluble and insoluble phosphate (P) compounds. The effectiveness of insoluble P sources on Pb immobilization depends on their rate of dissolution which can be enhanced by phosphate solubilizing bacteria (PSB). In this study, the effect of soluble (potassium dihydrogen phosphate) and insoluble (rock phosphate in the presence and absence of PSB) P compounds on the immobilization of Pb, and leaching of Pb and P was examined using both naturally contaminated (SR soil: NH₄NO₃ extractable Pb: 28.

Role of organic amendments on enhanced bioremediation of heavy metal(loid) contaminated soils.

As land application becomes one of the important waste utilization and disposal practices, soil is increasingly being seen as a major source of metal(loid)s reaching food chain, mainly through plant uptake and animal transfer. With greater public awareness of the implications of contaminated soils on human and animal health there has been increasing interest in developing technologies to remediate contaminated sites. Bioremediation is a natural process which relies on soil microorganisms and higher plants to alter metal(loid) bioavailability and can be enhanced by addition of organic amendments to soils.

Isolation of phosphate solubilizing bacteria and their potential for lead immobilization in soil.

Lead (Pb), a highly toxic heavy metal forms stable compounds with phosphate (P). The potential of phosphate solubilizing bacteria (PSB) to immobilize Pb by enhancing solubilization of insoluble P compounds was tested in this research. Eighteen different PSB strains isolated from P amended and Pb contaminated soils were screened for their efficiency in P solubilization.

Mobility of copper, chromium and arsenic from treated timber into grapevines.

The use of chromated copper arsenate (CCA) treated timber posts as support structures in New Zealand vineyards has raised concerns regarding the release of heavy metal(loid)s from the treated timber into the environment. A laboratory experiment was set up to evaluate if post sealing by painting reduces the release rate of CCA metal(loid)s from timber posts. Three posts were painted (Gripset 38, Multi Purpose Bitumen Rubber) on the bottom part, submerged in freshwater, and the concentrations of copper (Cu), chromium (Cr) and arsenic (As) in the water were monitored over a period of 8 months.

Phosphorus removal mechanisms in active slag filters treating waste stabilization pond effluent.

Phosphorus (P) removal mechanisms from waste stabilization pond effluent by a melter slag filter were investigated. The studied filter had treated pond effluent for a decade, but lost its P removal efficiency after 5 years. The P distribution in the slag was examined by scanning electron microscopy (SEM), electron dispersive spectrometry (EDS), X-ray fluorescence (XRF), X-ray diffraction (XRD), and chemical fractionation.

Role of phosphorus in (Im)mobilization and bioavailability of heavy metals in the soil-plant system.

A large number of studies have provided conclusive evidence for the potential value of both water-soluble (e.g..

Adsorption, complexation, and phytoavailability of copper as influenced by organic manure.

Copper (Cu) is bound strongly to clay minerals and organic matter in soils, and forms both insoluble and soluble organic complexes with organic carbon. In this experiment, the effect of five manure composts (biosolid, farmyard manure, spent mushroom, pig manure, and poultry manure) on the adsorption and complexation of Cu in a mineral soil (Manawatu sandy soil, Palmerston North, New Zealand) low in organic matter content was examined. The effect of biosolid on the uptake of Cu from the soil, treated with various levels of Cu (0-400 mg/kg soil), was examined by using mustard (Brassica juncea L.

Uptake of arsenic by New Zealand watercress (Lepidium sativum).

Watercress (Lepidium sativum) is consumed as a vegetable, especially by the indigenous community in New Zealand. An investigation was carried out on the accumulation of arsenic by watercress, following earlier reports of inordinate arsenic concentrations in some aquatic macrophytes collected from the Waikato River, North Island, New Zealand. The Waikato River and some other aquatic systems in Taupo Volcanic Zone, New Zealand have elevated arsenic concentrations due to geothermal activity.