Response of Castor Bean Plants to Different Row Spacings and Planting Seasons

The cultivation of the castor bean plant is prominent and important because of its potential for producing vegetable oils with special properties. However, research on cultivating castor bean plants is scarce, especially in areas with altitudes of 300 m or below. Moreover, the currently available cultivars have not been widely tested in Brazil. Thus, the aim of this study was to evaluate the response of the castor bean cultivar BRS Nordestina to different spacings at low altitudes during two cropping seasons. The study was conducted in the municipality of Itaocara, in the northwest Fluminense region, Brazil, which has an altitude of 60 m. The treatments consisted of five row spacings (1.5, 2.0, 2.5, 3.0 and 3.5 m) with 1 m between plants. The plants were cultivated in the 2007/2008 spring/summer season or in the 2008 autumn/winter season. A randomised block design with four replicates was used. The following parameters were assessed: plant height, height of insertion of primary raceme, number of racemes per plant, raceme length, number of fruits per raceme and grain yield. The spacing of 2.5 m between rows had the highest yield of castor beans during the two cropping seasons. The average yield of the cultivar BRS Nordestina indicates its potential for cultivation in northern Rio de Janeiro, below an altitude of 300 m. The yield was higher during the summer cropping season. The less-dense arrangement of the plant population contributed to the cultivation of plants with more racemes in both growing seasons.

Seasonal variations in the concentration and removal of nonylphenol ethoxylates from the wastewater of a sewage treatment plant

In this study, we investigated the occurrence and fate of nonylphenol（NP）, nonylphenol monoethoxylate（NP1EO） and nonylphenol diethoxylate（NP2EO） in a full scale sewage treatment plant, which applied an Anaerobic/Oxic process. Concentrations of NP, NP1 EO and NP2 EO in the wastewater were measured during the period spanning a whole year.The results showed remarkable seasonal variation in the concentrations of the compounds.The NPn EO compounds were most abundant in winter, with the total concentrations of influent NP, NP1 EO and NP2 EO ranging from 3900 to 7000 ng/L, 4000 to 4800 ng/L and 5200 to 7200 ng/L, respectively. Regarding the total removal efficiencies of the three types of short-chain NPn EO compounds, different trends were exhibited according to different seasons. The average removal efficiency of NP for the different seasons ranked as follows：winter 〉 summer 〉 autumn 〉 spring; NP2 EO concentrations decreased as follows： summer 〉autumn 〉 winter 〉 spring, while NP1 EO concentrations reduced according to： spring 〉summer 〉 autumn 〉 winter. We also investigated the contribution ratio of individual treatment units in the A/O process, with the findings suggesting that the anaerobic treatment unit plays an important role in the elimination of short-chain NPn EOs from the wastewater.

Decontamination efficiency and root structure change in the plant-intercropping model in vertical-flow constructed wetlands

Subtropical climatic conditions can contribute to the death of the aerial parts of constructed wetland plants in winter. This presents a barrier to the widespread application of constructed wetland and is an issue that urgently needs to be solved. Three contrasting experi- ments, the plant-intercropping model （A）, the warm- seasonal plant model （B）, and the non-plant model （C）, were studied in terms of their efficiency in removing pollutants, and the change in root structure of plants in the plant-intercropping model within the vertical-flow con- structed wetlands. The results indicate that model A was able to solve the aforementioned problem. Overall, average removal rates of three pollutants （CODcr, total nitrogen （TN） and total phosphorous （TP）） using model A were significantly higher than those obtained using models B and C （P 〈 0.01）. Moreover, no significant differences in removal rates of the three pollutants were detected between A and B during the higher temperature part of the year （P〉 0.05）. Conversely, removal rates of the three pollutants were found to be significantly higher using model A than those observed using model B during the lower temperature part of the year （P 〈 0.01）. Furthermore, the morphologies and internal structures of plant roots further demonstrate that numerous white roots, whose distribution in soil was generally shallow, extend further under model A. The roots of these aquatic plants have an aerenchyma structure composed of parenchyma cells, therefore, roots of the cold-seasonal plants with major growth advantages used in A were capable of creating a more favorable vertical-flow constructed wetlands media- microenvironment. In conclusion, the plant-intercropping model （A） is more suitable for use in the cold environment experienced by constructed wetland during winter.