Evaluation of plant growth regulators to increase nickel phytoextraction by Alyssum species.

Recent studies have shown that application of phytohormones to shoots of Alyssum murale increased biomass production but did not increase Ni shoot concentration. Increased biomass and Ni phytoextraction efficiency is useful to achieve economically viable phytomining. The objective of this study was to evaluate the effect of two types of phytohormones on the Ni phytoextraction capacity of four Alyssum species. Two different commercially available phytohormones (Cytokin and Promalin) based on cytokinins and/or gibberellins were applied on shoot biomass of four Ni hyperaccumulating Alyssum species (A. corsicum, A. malacitanum, A. murale, and A. pintodasilvae). Cytokin was applied in two concentrations and promalin in one concentration. The application of phytohormones had no clear positive effect on biomass production, Ni accumulation and Ni phytoextraction efficiency in the studied Alyssum species. A. malacitanum was the only species in which a significantly negative effect of these treatments was observed (in Ni uptake). A slightly positive response to promalin treatment was observed in the biomass production and Ni phytoextraction efficiency of A. corsicum. Although this effect was not significant it does indicate a potential application of these approaches to improve phytoextraction ability. Further studies will be needed to identify the most adequate phytohormone treatment as well as the appropriate concentrations and application times.

Development of agro-environmental scenarios to support pesticide risk assessment in Europe.

This paper describes work carried out within the EU-funded FOOTPRINT project to characterize the diversity of European agricultural and environmental conditions with respect to parameters which most influence the environmental fate of pesticides. Pan-European datasets for soils, climate, land cover and cropping were intersected, using GIS, to identify the full range of unique combinations of climate, soil and crop types which characterize European agriculture. The resulting FOOTPRINT European agro-environmental dataset constitutes a large number of polygons (approximately 1,700,000) with attribute data files for i) area fractions of annual crops related to each arable-type polygon (as an indicator of its probability of occurrence); and, ii) area fractions of each soil type in each polygon (as an indicator of its probability of occurrence). A total of 25,044 unique combinations of climate zones, agricultural land cover classes, administrative units and soil map units were identified. The same soil/crop combinations occur in many polygons which have the same climate while the fractions of the soils and arable crops are different. The number of unique combinations of climate, soil and agricultural land cover class is therefore only 7961. 26-year daily meteorological data, soil profile characteristics and crop management features were associated with each unique combination. The agro-environmental scenarios developed can be used to underpin the parameterization of environmental fate models for pesticides and should also have relevance for other agricultural pollutants. The implications for the improvement and further development of risk assessment procedures for pesticides are discussed.

Time-dependent distribution of surface-applied radionuclides and their recovery in maize during the growing season.

The spatial and temporal heterogeneity of field soils influences the fate and behavior of strongly sorbing pollutants and their entry into the food chain. We studied the redistribution of surface-applied 54Mn, 65Zn, 57Co, and 134Cs in the soil profile and their recovery in the aerial parts of maize grown on an untilled agricultural soil during the growing season. Radionuclides were more concentrated in the preferential flow paths (PFP) than in the soil matrix and their concentration decreased with time. The recovery of 54Mn in the aerial plant parts increased between pollen shed and maturity, while the recovery of 65Zn and 57Co did not show any significant difference, and the recovery of 134Cs decreased with time. The amount and distribution of rainfall, and the chemical, physical, and microbiological soil characteristics are the major factors influencing the variation of radionuclide recovery with time.

Is the transfer factor a relevant tool to assess the soil-to-plant transfer of radionuclides under field conditions?

The radiological impact of radionuclides released to the terrestrial environment is usually predicted with mathematical models in which the transfer of radionuclides from soil to the plant is described with the transfer factor (TF). This paper questions the validity of the protocols proposed by the International Atomic Energy Agency to measure TF in the field and in greenhouses conditions. We grew maize (Zea mays L.) both in the field after a surface application of radionuclides ((54)Mn, (57)Co, (65)Zn, and (134)Cs) and in a greenhouse with the same soil that has received the same fertilization and that had been previously sieved and homogeneously labeled with the same radionuclides before being repacked in pots. The analysis of the displacement of radionuclides in the field soil profile showed a higher concentration of the surface-applied radionuclides in the preferential flow path (PFP) in comparison to the soil matrix indicating that they infiltrated heterogeneously in the soil profile due to the structure-induced non-uniform water flow. A significantly higher recovery of (57)Co and (134)Cs was observed in the plants grown in the field soil, whereas no differences in the recovery of (54)Mn and (65)Zn between the two experiments were detected. These results suggest that (i) under field conditions the soil-to-plant transfer of radionuclides that co-exist as stable elements present at low concentrations in the soil and in the plant is higher than that measured under greenhouse conditions and (ii) the implicit assumption made when calculating the TF (that radionuclides are homogeneously distributed in the soil profile) is not valid, thereby preventing the calculation of an average concentration to obtain the TF parameter.