O. Ortiz

Toxic effects of digested, composted and thermally-dried sewage sludge on three plants

In order to evaluate potential toxic effects of stabilized sewage sludge that are currently applied to agricultural soils, three types of municipal sewage sludge and one pig slurry were subjected to phytotoxicity assays using three plants (Brassica rapa, Lolium perenne and Trifolium pratense). Equivalent batches of aerobically and anaerobically-digested sludge (F) from two municipal wastewater treatment plants, were composted (C) or thermally dried (T). In addition, one anaerobically-digested and thermally-dried pig slurry (P) was tested. A seedling growth test was performed in accordance with the OECD Guideline 208A, using seed emergence and shoot length as endpoints to identify the inhibition of plants growing in increasing doses of sludge. A correlation analysis between EC50 and physico-chemical parameters or the pollutant burden of the biosolids was also calculated. In all tests, lower germination rates were observed for T. pratense than for L. perenne and B. rapa. A moderate stimulatory effect on shoot length at low doses was observed for the three plants. In these wastes, a strong positive correlation was found between higher values of EC50 (less toxicity) and the stability degree of their organic matter, and a negative correlation between EC50 and total N, hydrolysable N or NH4-N content. No correlations were found with heavy metal or organic pollutant content in those wastes. Results indicate that digested sludge, thermally-dried sludge and thermally-dried pig slurry have non-negligible short term phytotoxic effects, and confirm that composting is an effective sludge treatment for the reduction of phytotoxicity.

Respiration potential of microbial biomass in a calcareous soil treated with sewage sludge

Urban sewage sludge from Gerona (Spain) was applied to a low organic matter calcareous soil (calcixerollic xerochrept, Bellaterra, Spain), at concentrations of 7.5% and 15%. Control soil (0% sludge), sludge, and mixtures were incubated for 1 year inside a chamber in a 15‐L container. Moisture and temperature were controlled. Microbial biomass and CO2 production were measured. Soil respiration potential was proportional to soil sewage sludge content. No microbial growth inhibition was detected in soil‐sewage sludge mixtures despite the fact that the 15% sewage sludge concentration doubled the recommended maximum input applicable to the soil. Sewage sludge incubated without soil showed lower respiration values. One year after sewage application, respiration potential of soil‐sewage sludge mixtures and sewage sludge dropped to lower values, suggesting stabilization of organic matter. Mineralization coefficients were high at the beginning of the incubation period, in comparison with other calcareous soils, bu...

Effects of different types of sludge on soil microbial properties: a field experiment on degraded Mediterranean soils.

The recycling of suitable organic wastes can enhance soil fertility via effects on soil physical, chemical and biological properties. To compare the effects of digested (DS), thermally dried (TDS) and composted dewatered (CDS) sewage sludge on soil microbiological properties, an experiment was conducted at field sites for more than one year (401 d) when applied to two Mediterranean degraded soils (loam and loamy sand soils). All three types of sewage sludge had a significant effect on measured parameters. In a short time, the plots of both loamy sand and loam soils amended with TDS showed the highest microbial basal respiration (loam soil: P＜0.01; loamy sand soil: P＜0.001) and carbon mineralization coefficient (loam soil: P＜0.01; loamy sand soil: P＜0.001). Furthermore, on loamy sand soil, the plots amended with TDS showed the highest microbial metabolic quotient (qCO2) (P＜0.05). This study revealed that the addition of sludge caused transient non-equilibrium effects on almost all soil microbial properties. However, there were no differences one year later because the remaining organic carbon was stable and quite similar in all treatments. These results may have practical implications for the rehabilitation of degraded soils.

Sewage Sludge Application Protocol for Quarry Restoration (Catalonia)

and wildlife communities (Weir et al. 2007). Rotational grazing and prescribed patch burning are essential parts of the long-term management strategy. It is the intention of the Prairie Management Committee to use these two ecosystem drivers together as they occurred historically on native prairies. Naturally, the cattle had previously gathered around the springs and, by doing so, blocked the flow of water. To prevent this occurrence, solar fencing has been installed around the perimeter of each of the six springs to protect the immediate areas from the cattle and to restore flowing water to the Prairie. Temporary hiking trails have been mowed to allow human access for educational purposes and for maintenance of the land. No permanent trails will be established, thus preventing the destruction of large areas of native grasses. To date, nearly three kilometers of walking and hiking trails have been cut and are open to the public. These trails will be relocated annually in order to protect the Prairie’s delicate plant life. The Prairie is home to a number of rare species. These include Fendler’s aster (Symphyotrichum fendleri), known in Nebraska from only Webster and Franklin Counties, and Fremont’s evening primrose (Oenothera macrocarpa ssp. fremontii), known only from Webster, Franklin, and Red Willow Counties. Both are potential candidates for threatened status in Nebraska. Dr. Steve Rothenberger, professor of biology at the University of Nebraska at Kearney and member of the Foundation’s Prairie Management Committee, has estimated that a minimum of 250 plant species exist on the Prairie, including numerous legumes, such as golden dalea (Dalea aurea) and leadplant (Amorpha canescens), and a nice diversity of grasses native to both talland mixed-grass prairies, such as big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), buffalo grass (Buchloe dactyloides), and blue grama (Bouteloua gracilis). Within the next year, the Foundation will erect signage to educate visitors about the variety of plants found on the Prairie, often including interesting facts about how Native Americans would have used them for medicinal purposes. The Prairie restoration is integral to the mission of the Willa Cather Foundation. Preservation of the Prairie is part of a holistic approach to the study of America’s art, history, and culture through the works of Willa Cather, who was a great champion of prairie lands. As Carl Linstrum observes in O Pioneers!, ”the land wanted to be let alone, to preserve its own fierce strength, its peculiar, savage kind of beauty, its uninterrupted mournfulness‘ (Cather 1913, 15). We strive to be a part of the land’s struggle back to itself.

Criterios y recomendaciones para la toma de imágenes de perfiles de suelos para crear una base de datos de imágenes .

El objetivo de este trabajo es mejorar las habilidades de los cientificos de suelos en la toma de imagenes de suelos para la docencia y la publicacion de trabajos cientificos. Los autores han compilado un conjunto de instrucciones, recomendaciones y consejos a partir de su experiencia, que van desde la captura de imagenes a la seleccion de un formato de archivo apropiado para almacenar o publicar una imagen, pasando por la edicion y el post-procesado de las imagenes. Los aspectos principales incluidos en este trabajo se refieren a la posicion fisica de la camara cuando se dispara para tomar un perfil de suelo, el ajuste basico de la camara, las acciones basicas de retoque y una lista de recomendaciones y errores que deben evitarse.