Phytotreatment of sewage sludge contaminated by heavy metals and PAHs by co-planting Sedum alfredii and Alocasia marorrhiza.

High concentrations of heavy metals and organic pollutants in municipal sewage sludge are key factors limiting its use in agriculture. The objectives of this study were to decrease the heavy metal and polycyclic aromatic hydrocarbon concentrations in sewage sludge by phytotreatment and to determine, in a field experiment, whether co-planting is more effective than using a mono-crop of Sedum alfredii. Four treatments were used in the plot experiment: no sludge, no plants, S. alfredii and co-planting S. alfredii and Alocasia marorrhiza. The results showed that co-planting produced tubers and shoots of A. marorrhiza that were suitable as a safe animal feed and good organic K fertilizer, respectively. Co-planting was more effective than mono-planting at reducing concentrations of total Zn and diethylenetriaminepentaacetic acid (DTPA)-extractable Zn, Cd, and Cu in the sludge. Co-planting decreased the concentrations of DTPA-extractable heavy metals and benzo[a]pyrene (B[a]P) in the sludge significantly compared with the unplanted sludge. Decreases of 87, 75, 85, 31, and 64% were obtained for B[a]P and DTPA-extractable Zn, Cd, Cu, and Pb, respectively, compared with the fresh sludge. These results indicate that co-planting can reduce significantly the environmental risks associated with heavy metals and B[a]P in sewage sludge for further disposal.

Lead and cadmium induced alterations of cellular functions in leaves of Alocasia macrorrhiza L. Schott.

Alocasia macrorrhiza is a fast growing and propagating herbaceous species commonly found in South China. To determine its physiological responses to Pb and Cd stresses, the biochemical, histochemical and cytochemical changes under PbAC2 and CdCl2 phytotoxicity were detected using leaf discs as an experimental model. After leaf discs were infiltrated in different concentrations of PbAC2 and CdCl2 solutions (0, 50, 100, 150, 200 microM) for 72 h, the formation of reactive oxygen species (H2O2 and O2-) in plant tissue were found to be exaggerated together with elevated OH concentration and cell death. Changes in chlorophyll fluorescence (Fv/Fm, PhiPSII, qP and NPQ) imaging colours/areas of leaf discs indicated decreased photosystem II functions by both heavy metal treatments and positive reactions of antioxidants under Pb2+ stress. Results showed that fluorescent detection of hydroxylated terephthlate using terephthalic acid as OH trap is a simple, yet valuable and specific method for monitoring OH generation in plant tissue under heavy metal stresses. As compared with Cd2+, Pb2+ was found to be less toxic, indicating that A. macrorrhiza tissue might have a potential tolerance to Pb.

Produção e renda de taro Macaquinho, solteiro e consorciado comalface 'Salad Bowl', em solo com cobertura de cama-de-frango semidecomposta / 'Macaquinho' taro in monocrop system and intercropped with 'SaladBowl' lettuce in soil with chicken manure mulching

Este trabalho teve como objetivos estudar a produtividade e a renda do taro ‘Macaquinho, em cultivo solteiro e consorciado com a alface mimosa ‘Salad Bowl’, em solo sem (SCF) ou com (CCF) cobertura com cama-defrango (10 t ha-1). A colheita da alface foi feita aos 64 dias após a semeadura e a do taro aos 199 dias após o plantio. Na alface obtiveram-se baixos valores para plantas com “cabeças” comerciais (média de 15.830 “cabeças” ha-1) e altos para as não comerciais (média de 89.160 “cabeças” ha-1). No taro, as maiores produções de folhas (4,89 t ha-1), rizomas-mãe (6,46 t ha-1), rizomas-filho comerciais (15,33 t ha-1) e não-comerciais (9,73 t ha-1) foram obtidas nas plantas sob cultivo solteiro e cultivadas em solo CCF. A razão de área equivalente (RAE) para o consórcio taro-alface, em solo CCF foi de 1,47 e a do consórcio em solo SCF foi de 1,82. As rendas bruta e líquida mostraram que no taro foi melhor o cultivo solteiro em solo CCF (R$ 18.936,00 e R$ 17.596,00, respectivamente). Para alface, foi melhor o consórcio com taro, em solo CCF (R$ 18.024,00 e R$ 17.224,00, respectivamente). A maior RAE não induziu as maiores rendas bruta e líquida.

This work had as aim to study yield and income of ‘Macaquinho’ taro in monocrop system and intercropped with ‘Salad Bowl’ mimosa lettuce in soil without (SCF) or with (CCF) mulching with chicken manure (10 t ha-1). Lettuce harvest was done on 64 days after sowing and taro harvest on 199 days after planting. For lettuce it was obtained low values for plants with commercial heads (average of 15,830heads ha-1) and high values for non-commercial heads (average of 89,160 heads ha-1). For taro, the highest yields of leaves (4.89 t ha-1), corms (6.46 t ha-1), commercial (15.33 t ha-1) and non-commercial (9.73 t ha-1) cormels were obtained in plants under monocrop system and that were cultivated in CCF soil. Land Equivalent Ratio (LER) for taro/lettuce intercropping, in CCF soil, was 1.47 and of intercropping in SCF soil was 1.82. Gross and net income showed that for taro it was better to use of monocrop system in CCF soil (R$ 18,936.00 and R$ 17,596.00, respectively). For lettuce, it was better to use intercrop system with taro in CCF soil (R$ 18,024.00 and 17,224.00, respectively). The highest LER did not induce the highest gross and net income.

Produção e composição nutritiva de taro em função do propágulo, em solo hidromórfico do Pantanal Sul-Mato-Grossense / Yield and nutritive components of taro as a function of propagule type in a hydromorfic soil of South Mato grosso Pantanal

O objetivo do trabalho foi determinar a produtividade e a composição nutritiva dos rizonas de taro, em condições de solo hidromórfico do pantanal sul-mato-grossense. Foram avaliados os taros Chinês e Macaquinho, propagados por rizomas das classes grande e pequena, como tipos inteiros e cortados no meio, arranjados em esquema fatorial 2x2x2, no delineamento experimental de blocos casualizados, com quatro repetições. A população final, altura das plantas e massa fresca das folhas e dos rizomas-mãe do taro Chinês foi significativamente superior à do macaquinho. Quanto ás classes de propágulos utilizados para a propagação, foi melhor o uso de rizomas grandes. O uso de rizomas inteiros foi significativamente melhor que dos rizomas cortados quanto à população final e produção de massa fresca dos rizomas mãe (RM) e semelhantes para altura das plantas e produções de massa fresca de folhas e dos rizomas-filho (RF). Em relação à composição nutritiva dos rizomas, os RM e os RF tiveram teores caracterísitcos do clone. Os RM e RF dos dois clones apresentaram maiores teores de resíduo mineral fixo, proteínas e carboidratos e menores teores de lipídeos e de fibras, assim como de valor calórico total-VCT, que os domilho. Os RM e RF dos dois clones tiveram menores teores de lipídeos, carboidratos e VCT em relação à farinha de trigo

The objective of this work was to determine yield and nutritive components of taro rhizomes inhydromorfic soil conditions of South Mato Grosso Pantanal. Chinês and Macaquinho taroswere evaluated. They were propagated by rhizomes of big and small classes, as whole and halftypes, arranged as 2 x 2 x 2 factorial scheme in randomized block experimental design, with four replications. Final population, plant height and fresh mass of leaves and of corms of Chinêstaro were significantly superior than 'Macaquinho'. Regarding to propagule classes used forpropagation, big rhizome was the best. The use of whole rhizomes was significantly better thancut rhizomes regarding to final population and yield of fresh mass of corms (RM) and it wassimilar for plant height and yield of fresh mass of leaves and of cormels (RF). In relation tonutritive compound of rhizomes, RM and RF had contents which were characteristics of theclone. RM and RF of both two clones showed higher contents of fix mineral residue, proteinsand carbohydrates and they have smaller contents of lipids and of fibers, as well of total caloricvalue, than of corn. RM and RF of both two clones had smaller contents of lipids, carbohydratesand TCV in relation to wheat flour

Plants grown on sewage sludge in South China and its relevance to sludge stabilization and metal removal.

The production of sewage sludge in China has been increasing sharply in order to treat 40% of the municipal sewage in 2005 as planned by central government. The main sludge disposal method is landfill owing to heavy metal contamination, but it presents an attractive potential for agricultural land application. Experiments were carried out to study the simultaneous metal removal and sludge stabilization by plants. The sludge samples were collected from Datansha Wastewater Treatment Plant of Guangzhou, it contained excessive Cu and Zn compared with the Chinese National Standard for Agricultural Use of Sewage Sludge. Plants growing on sludge beds were investigated to follow their growth and metal uptake. 30 sludge plants were identified during 1 year's observation. A Zn high-accumulating and high growth rate plant(Alocasia macrorrhiza) was selected and grown on sludge beds in plots. The water, organic matter, heavy metals and nutrients contents, the E. coli number and the cress seed germination index were monitored for the sludge samples collected monthly. The plant growth parameters and its heavy metals contents were also determined. The sewage sludge treated by plants could be stabilized at about 5 months, the E. coli number was significantly decreased and the cress seed germination index attained 100%. Crop on sludge could ameliorate the sludge drying. The experiments are continuing to find out the appropriate plant combination for simultaneous sludge stabilization and metal removal for an acceptable period. Comparisons between the proposed processes and other methods for treating produced sludge such as composting, chemical andbacterial leaching were discussed.