Tesis doctoral de Wilson Ariel Ramirez Hernandez
Plants play an important role in the fate and transport of many pollutants in soil and also are good indicators of their phytotoxic effects, so the bioaccumulation of pollutants, their bioavailability and related ecotoxicity, can be easily evaluated by specific plant bioassays. In this thesis we evaluated the suitability of standard test plants as indicators of toxicity in soils amended with biosolids or contaminated with an organic pollutant. To achieve this objective, we made use of 3 plant species for the estimation of the toxic effects of the solid and extractable phase of digested, composted and thermally-dried sewage sludge. We also tested standard plants to compare the toxicity of a reference toxicant in several mediterranean natural soils, and finally we used plants as indicators of the phytotoxic interactions between an organic pollutant and a heavy metal in a mediterranean soil. from the assays with several types of sewage sludge, we found phytotoxic effects at different rates in all the wastes tested, and a strong relation between the chemical stability of sludge and their phytotoxicity. The lower toxicity was found in the composted sludge, suggesting this postreatment as the most suitable to reduce the phytotoxicity of the digested sludge before their application to agricultural soils or for rehabilitation purposes. the tests made with sludge extracts permitted a better identification of the toxic-group compounds from sludge that affect plants. The higher phytotoxicity of the extracts was related to the hydrophilic substances rather than the more lipophilic ones. The main contributors to the toxicity were the ammonia-n and other water soluble compounds suggesting that special caution must be taken with biosolid leachates in field applications. among the phytotoxicity assays conducted to identify the possible interactions between cu and 4-nonyl-phenol, the root length test was the most sensitive plant endpoint to detect the effects of these pollutants. When the organic pollutant 4-nonyl-phenol was tested alone, phytotoxic effects were not found on the measured endpoints, but in presence of medium and high rates of cu, an interaction between them was observed, suggesting that the organic pollutant affects the bioavailability of the heavy metal. Nevertheless the true mechanisms underlying these interactive effects have not been explored. the tests conducted with natural mediterranean soils and a reference toxicant (sodium trichloroacetate), showed that the characteristics of the natural soils had an important impact on the performance of the plant species assayed and the toxicant. The main soil parameters explaining the plant response were the total nitrogen, the c/n ratio and the cation exchange capacity. All the mediterranean natural soils assayed fulfilled the validity criteria required for ecotoxicological plant testing, considering the endpoints measured. The fact that the natural soils used in this study came from the mediterranean region expands the range of reference substrates that was previously restricted to soils of temperate regions, and can be used as useful substrates for further studies. the sensitivity of standard plant tests used in this thesis permitted the toxic effects of the pollutants and biosolids applied to be distinguished, and new information about the effects of some contaminants and organic residues in soils was obtained. In synthesis, our results emphasize in the relevance of phytotoxicity controls of organic residues and sewage sludge stabilization by postreatment processes before application to soils. In general, in all the plant bioassays performed, the suitability of standard test plants as indicators of toxicity in soils ameliorated with biosolids or affected by pollution was confirmed. key words: soil pollution, soil amendments, phytotoxicity, standard plant tests, organic residues, sewage sludge, sludge extracts, pig slurry, composted sludge, thermally dried sludge, copper, 4-nonylphenol, pollutant interactions, standard soils, glm, natca, brassica rapa, lolium perenne, trifolium pratense.
Datos académicos de la tesis doctoral «Preserving soils from pollution threats: an assessment of phytotoxic effects in amended and contaminated soils«
- Título de la tesis: Preserving soils from pollution threats: an assessment of phytotoxic effects in amended and contaminated soils
- Autor: Wilson Ariel Ramirez Hernandez
- Universidad: Autónoma de barcelona
- Fecha de lectura de la tesis: 19/10/2009
Dirección y tribunal
- Director de la tesis
- Josep María Alcañiz Baldellou
- Tribunal
- Presidente del tribunal: Juan rafael Boluda hernadez
- Manuel Bonmatí (vocal)
- (vocal)
- (vocal)
