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Rice paddy fields pose a high risk of water pollutions for the surrounding waterbodies through surface runoff and subsurface fluxes. Compared to surface runoff, subsurface flux from rice paddy fields has received less attention and is still poorly quantified, mainly due to low-frequency measurements at field scale and limited modeling capability at regional scale. Here we proposed a simplified modeling approach to estimate the subsurface fluxes of water, nitrogen (N) and phosphorus (P) from rice paddy fields and examined their relative importance compared to surface runoff. This model was established based on the high-frequency field measurements over two rice growing seasons in central China and the extended datasets across the East Asia. Two-year site-based observations indicate the significance of subsurface fluxes of water (737–785 mm season−1), N (28.5–40.0 kg N ha−1) and P (0.7–4.3 kg P ha−1) compared to those of surface runoff (178–199 mm season−1, 4.5–12.9 kg N ha−1, 0.5–2.6 kg P ha−1). Our regional estimations in the East Asia reveal that subsurface fluxes from rice paddy fields were comparable with surface fluxes, primarily controlled by the magnitude of seasonal precipitation. Subsurface fluxes were the dominant pathway of nutrient losses in drier rice cropping areas, while surface runoff was the more important process in wetter areas. In the light of the regional differences, we suggest that a spatially flexible set of policies for mitigating nutrient losses from rice paddy fields would be beneficial for the future water-quality improvements in the surrounding waterbodies.

Nanosized TiO2/Ti photoanodes fabricated by metalorganic chemical vapor deposition (MOCVD) under different deposition temperatures were characterized and applied to the photoelectrocatalytic degradation of model pollutant of phenol. The anode prepared at 773 K was verified in anatase phase with a size about 60 nm and achieved the best photoelectrocatalytic activity, where IPCE could reach as high as 89% and the photoconversion efficiency peaked at 8.4%. The photoelectrocatalytic degradation of phenol was found well fit a pseudo-first-order kinetics, and kept stable performance in five continuous runs, confirming potential application of the electrode prepared by MOCVD for organic pollutants abatement. Keywords: TiO2 anode, Photoelectrocatalysis, MOCVD, Organic pollutants degradation, Deposition temperature

The world's oil supplies are dwindling. Bioenergy is an integral part of renewable energy solutions to relieve the current energy crisis. Unlike liquid biofuels such as bioethanol and biodiesel, microbial fuel cells (MFCs) generate electricity directly by degrading organic matter through electrochemical reactions. MFCs are capable of utilizing low-grade organic matter in wastewater streams. Despite the numerous theoretical advantages that MFCs have, they are not yet ready for “real-world” applications other than powering small sensor devices because of their low power output and high costs in construction and operation. New advances are needed in biofilm engineering, materials for electrodes and reactor configuration to achieve much better bioelectrochemical performance. This chapter reviews the bioelectrochemistry of electrogenic biofilms and the electrochemical mechanisms of MFCs. It explores various ways to improve MFC performance including state-of-the-art hypotheses on using engineered biofilms to revolutionize MFCs.