[en] The aim of this thesis was to study the assisted phytoremediation in contaminated soils with metals. To accomplish this objective, various tests were conducted in the laboratory, greenhouse and field. The effects of various organic residues on nitrogen losses during application and storage were studied. There was also evaluated the effect of composting time on these losses and how C minerlization evolves during it. The opportunities for metal's mobility by biosolid application to soils were observed. Considerating the aim of remediating contaminated sites with heavy metals, it was studied the use of calcareous amendments, Bisolid compost and phytoremediation. The results show that, during the composting process, ammonia losses are inevitable. The testing was extended to other organic residues, such as equine and bovine manure. The possibility of differential mineralization of organic residues leads to ammonia loss in terms of the amendment used. It was observed that the microorganisms' respiration is linked to the fertlizer's descomposition, which increased with study time. Manures without prior stabilization showed a high respiration rate. There were also evaluated the phytotoxic effects of different amendments. The testing with ryegrass, a very common kind of the Pampas grasslands, showed that the phytotoxic effects were mainly associated to pH and electrical conductivity. These effects were observed both in the delaying at the time of germination and in their percentage. Having identified the environmental effects of the generation and use of different organic residues, it was decided to continue the testing with biosolids compost. Then it was decided to evaluate if its use favored heavy metals contamination in soils where they were discharged. The addition of contaminated calcareous amendment to the soil produced the reduction in the bioavailability of Cd and Zn, showing a direct effect on the remediation of contaminated sites. Its use in connection with compost could also be a viable option for improving the physical and chemical fertility of soil remedying. Finally, it was studied the use of biosolids compost and the use of phytoremediation with Festuca rubra in the remediation of soils contaminated with cadmium, copper, lead and zinc. The results of these experiments in columns helped to clarify this point. Compost application presented a positive environmental impact. Due to increased biomass achieved it would be evidenced the reduction of the effect of wind and water erosion, decreasing the dispersion of contaminated topsoil into other areas. The increase in the ratio of Cd and Pb aerial / root with the application of compost would strengthen the phytoremediator effect of Festuca because of the possibility of harvesting the absorbed metal in a greater proportion. On the soil, it was clarified the greater mobility of extractable fractions with DTPA versus total fractions. It was observed that the application of compost with or without the plant decreased the mobilization of Zn, Cu and Cd total, limiting its possible leaching to lower horizons, but, however, this effect was not evidenced in the extractable fraction with DTPA. It would be appropriate to discuss then what was found in leachate. In the leaching experiment through the horizons of a typical soil in the Pampas, it was shown that the Bt horizon presents a barrier to leaching of metals. The application of a dose of organic amendment and successive crop had no effect on the leaching of metals. For pollution levels studied, the obtained leachate showed no concentrations exceeding the limits set by the standards of quality drinking water. This would allow us to conclude then that assisted phytoremediation is a recommended practice for remediation of large areas contaminated with heavy metals.

[gl] O obxectivo desta tese foi estudar a fitorremediación asistida en solos contaminados con metais, tendo en conta experimentos de compostaxe, descomposición e fitotoxicidade con varias emendas que foron feitos en laboratorio, invernadoiro e campo. Estudouse a acción de diversos refugallos orgánicos sobre as perdas de nitróxeno nas fases de aplicación e almacenamento. Tamén se avaliou o efecto que produce o tempo de compostaxe nestas perdas e mais a evolución do carbono. Observáronse as posibilidades de mobilidade dos metais pesados e estudouse o uso de emendas con calcio, compós de biosólido e mais fitoremediación, por separado ou en combinación. Os resultados indican que durante a compostaxe as perdas de amoníaco son inevitables. Estendeuse o estudo a outros refugallos orgánicos, como o esterco de equino e de vacún. A mineralización diferencial dos residuos orgánicos supuxo perdas de amoníaco en función da emenda usada. Observouse que a respiración dos microorganismos está ligada a descomposición dos abonos, a cal aumentou con tempo do ensaio. Diste xeito os estercos sen estabilización previa evidenciaron altas taxas de respiración. Ademais avaliáronse os efectos fitotóxicos das distintas emendas. O ensaio realizado con raigrás, especie común nos pastos pampeanos, mostrou que os efectos fitotóxicos dependen principalmente do pH e mais da condutividade eléctrica. Estes efectos observáronse tanto no retraso do momento da xerminación como na súa porcentaxe. Unha vez determinados os efectos ambientais do uso de diferentes refugallos orgánicos, optouse por continuar os estudos co compós de biosólidos. Avaliouse si su o seu uso favorecía a contaminación con metais pesados nos solos onde eran aplicados. A adición o solo contaminado de emenda con caliza produciu a redución da biodisponibilidade de Cd y Zn, mostrando efecto directo na remediación de sitios contaminados. O uso conxunto con compós podería ser ademais unha opción viable para a mellora da fertilidade física e química dos solos a remediar. Finalmente, estudouse o uso do compós de biosólidos e mais o uso da fitorremediacion con Festuca rubra na mellora de solos contaminados con cadmio, cobre, chumbo e cinc. Os resultados dos experimentos en columnas axudaron a clarificar este aspecto. A aplicación de compós presentou un impacto ambiental positivo. Debido o incremento da biomasa evidenciouse a reducción do efecto da erosión hídrica e mais eólica diminuíndo desta forma la dispersión do horizonte superficial contaminado deica outras áreas. O incremento da relación de Cd e Pb aéreo/raíz coa aplicación de compós permitiu potenciar o efecto fitoremediador da festuca, debido a posibilidade de colectar en maior proporción o metal absorbido. No solo observouse a maior mobilidade das fraccións extraíbles con DTPA fronte as fracción totais. A aplicación de compós con o sen planta diminuíu a mobilización do Zn, Cu y Cd total, o que limita a súa posible lixiviación a prol dos horizontes inferiores, sen embargo este efecto non se evidenciou na fracción extraíble con DTPA. Convén discutir estes dados cos resultados dos lixiviados . No ensaio de lixiviación a través dos horizontes dun solo típico da Rexión Pampeana demostrouse que o horizonte Bt presenta unha barreira a la lixiviación de metais. A aplicación de unha doses de emenda orgánica e mais o cultivo sucesivo, non influíron na lixiviación de metais. Para os niveis de contaminación estudados, los lixiviados obtidos non presentaron concentracións que superen os límites establecidos polos estándares de calidade de auga de bebida. Isto permitiríanos concluír, xa que logo, que a fitorremediacion asistida e unha práctica aconsellada para a remediación de áreas extensas contaminadas con metais pesados.