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Synchronous fluorescence spectra and the first derivative spectra of urban rivers affected by treated sewage were studied to find the optimum index for biochemical oxygen demand (BOD) estimation. In addition, various sample treatment methods as well as the multiple regression method using available monitoring parameters were examined to improve the BOD estimation capability of the indices. From July to November 2006, grab samples were collected from three rivers in the city of Seoul, Korea, which included one receiving effluent from a municipal wastewater treatment facility. The BOD values of the samples ranged from 0.4 to 28.0 mg l(-1). Out of the many fluorescence characteristics observed, the relative fluorescence intensity at 283 nm to 245 nm from the synchronous spectra was selected as the optimum fluorescence estimation index because it had the highest positive correlations with the BOD values (r = 0.910). The filtration process, using GF/F filter prior to the fluorescence measurement, resulted in an enhanced correlation demonstrating that the removal of suspended solids from the samples helps alleviate, to some extent, the interference of light scattering. In contrast, the same correlation was not enhanced by the pH adjustment of the sample to minimize the complexation of organic matter with cations. The multiple regression method, using either light scattering intensity at 633nm or turbidity, greatly enhanced the correlation between measured and predicted BOD values. The correlation was even higher than that obtained for filtered samples, thus suggesting that the multiple regression method based on the original sample is more effective than sample treatment in enhancing BOD estimation.

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The assemblage of root-associated microorganisms plays important roles in improving their capability to adapt to environmental stress. Metal(loid) hyperaccumulators exhibit disparate adaptive capability compared to that of non-hyperaccumulators when faced with elevated contents of metal(loid)s. However, knowledge of the assemblage of root microbes of hyperaccumulators and their ecological roles in plant growth is still scarce. The present study used Pteris vittata as a model plant to study the microbial assemblage and its beneficial role in plant growth. We demonstrated that the assemblage of microbes from the associated bulk soil to the root compartment was based on their lifestyles. We used metagenomic analysis and identified that the assembled microbes were primarily involved in root-microbe interactions in P. vittata root. Notably, we identified that the assembled root microbiome played an important role in As requisition, which promoted the fitness and growth of P. vittata. This study provides new insights into the root microbiome and potential valuable knowledge to understand how the root microbiome contributes to the fitness of its host.