Heavy metals in soils

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Treatment Wetlands, Second Edition

Because of their insolubility in water, nanoparticles have a limitation concerning toxicity experiments. The present study demonstrated a plant agar test for homogeneous exposure of nanoparticles to plant species. The effect of Cu nanoparticles on the growth of a plant seedling was studied, and bioaccumulation of nanoparticles was investigated. All tests were conducted in plant agar media to prevent precipitation of water-insoluble nanoparticles in test units. The plant species were Phaseolus radiatus (mung bean) and Triticum aestivum (wheat). Growth inhibition of a seedling exposed to different concentrations of Cu nanoparticles was examined. Copper nanoparticles were toxic to both plants and also were bioavailable. The 2-d median effective concentrations for P. radiatus and T. aestivum exposed to Cu nanoparticles were 335 (95% confidence level, 251-447) and 570 (450-722) mg/L, respectively. Phaseolus radiatus was more sensitive than T. aestivum to Cu nanoparticles. A cupric ion released from Cu nanoparticles had negligible effects in the concentration ranges of the present study, and the apparent toxicity clearly resulted from Cu nanoparticles. Bioaccumulation increased with increasing concentration of Cu nanoparticles, and agglomeration of particles was observed in the cells using transmission-electron microscopy-energy-dispersive spectroscopy. The present study demonstrated that the plant agar test was a good protocol for testing the phytotoxicity of nanoparticles, which are hardly water soluble.

Toxicity and bioavailability of copper nanoparticles to the terrestrial plants mung bean (Phaseolus radiatus) and wheat (Triticum aestivum): plant agar test for water-insoluble nanoparticles.

In recent years, copper (Cu) pollution in agricultural soils, due to arbitrary use of pesticides, fungicides, industrial effluent and wastewater irrigation, present a major concern for sustainable agrifood production especially in developing countries. The world’s major food requirement is fulfilled through agricultural food crops. The Cu-induced losses in growth and yield of food crops probably exceeds from all other causes of food safety and security threats. Here, we review the adverse effects of Cu excess on growth and yield of essential food crops. Numerous studies reported the Cu-induced growth inhibition, oxidative damage and antioxidant response in agricultural food crops such as wheat, rice, maize, sunflower and cucumber. This article also describes the toxic levels of Cu in crops that decreased plant growth and yield due to alterations in mineral nutrition, photosynthesis, enzyme activities and decrease in chlorophyll biosynthesis. The response of various crops to elevated Cu concentrations varies depending upon nature of crop and cultivars used. This review could be helpful to understand the Cu toxicity and the mechanism of its tolerance in food crops. We recommend that Cu-tolerant crops should be grown on Cu-contaminated soils in order to ameliorate the toxic effects for sustainable farming systems and to meet the food demands of the intensively increasing population.

The effect of excess copper on growth and physiology of important food crops: a review

https://espace.library.uq.edu.au/view/UQ:34525/Menzies_at_al_2007_UQ_eSpace.pdf

Evaluation of extractants for estimation of the phytoavailable trace metals in soils.

The effects of copper on the growth, tolerance indices, mineral composition (N, P, K, Fe, Zn and Mn) and metal uptake of reed (Phragmites australis [Cav. Trin. ex Steudel]) and maize (Zea mays L.) were investigated in hydroponic experiments at copper concentrations ranging from 0.5 to 157 μM Cu. A reduction in root length was shown to be a good indicator of copper toxicity, concentrations of 15.7 and 78.7 μM Cu inhibiting root growth in maize and reed, respectively. The reed was significantly more tolerant of copper than maize and at 7.85 μM Cu (external concentration), reed can be described as a Cu tolerant plant, and maize as a Cu non-tolerant species. As a result of Cu toxicity, the concentrations of macronutrients N, P and K decreased in both shoot and root of maize, while the concentrations were hardly affected in reed tissues. Fe concentration increased in shoots and roots of maize and in roots of reed with increasing Cu treatments, leading to highly significant (p<0.01) linear relationships between tissue Fe and Cu concentrations. The bioconcentration factor (BCF) of Cu was higher in roots than in shoots of both plant species, ranging from 612 to 1592 in reed for the Cu treatments tested. In the roots of maize, BCF of Cu increased from 349 to 1931 when increasing Cu in nutrient solution from 7.85 μM to 78.5 μM. Therefore, reed could be useful in wastewater treatments for the removal of Cu. However, the use of reed in phytoextraction of Cu from contaminated soils is limited by the low accumulation rate in shoots and although reed can be more efficient than maize for Cu phytoextraction, harvesting the full biomass, including roots, may be required.

Nadia Ait Ali

Papers

Tolerance and bioaccumulation of copper in Phragmites australis and Zea mays

Tolerance and bioaccumulation of cadmium by Phragmites australis grown in the presence of elevated concentrations of cadmium, copper, and zinc