Potential contribution of anammox to nitrogen loss from paddy soils in Southern China.

The anaerobic oxidation of ammonium (anammox) process has been observed in diverse terrestrial ecosystems, while the contribution of anammox to N2 production in paddy soils is not well documented. In this study, the anammox activity and the abundance and diversity of anammox bacteria were investigated to assess the anammox potential of 12 typical paddy soils collected in southern China. Anammox bacteria related to "Candidatus Brocadia" and "Candidatus Kuenenia" and two novel unidentified clusters were detected, with "Candidatus Brocadia" comprising 50% of the anammox population. The prevalence of the anammox was confirmed by the quantitative PCR results based on hydrazine synthase (hzsB) genes, which showed that the abundance ranged from 1.16 × 10(4) to 9.65 × 10(4) copies per gram of dry weight. The anammox rates measured by the isotope-pairing technique ranged from 0.27 to 5.25 nmol N per gram of soil per hour in these paddy soils, which contributed 0.6 to 15% to soil N2 production. It is estimated that a total loss of 2.50 × 10(6) Mg N per year is linked to anammox in the paddy fields in southern China, which implied that ca. 10% of the applied ammonia fertilizers is lost via the anammox process. Anammox activity was significantly correlated with the abundance of hzsB genes, soil nitrate concentration, and C/N ratio. Additionally, ammonia concentration and pH were found to be significantly correlated with the anammox bacterial structure.

Anaerobic ammonium oxidation in agricultural soils-synthesis and prospective.

Denitrification is considered as the dominant nitrogen (N) removing pathway, however, anaerobic oxidation of ammonium (anammox) also plays a significant part in N loss in agricultural ecosystems. Large N inputs into agricultural soils may stimulate the growth of anammox bacteria, resulting in high activity and diversity of anammox bacteria and subsequent more N loss. In some specific niches, like oxic-anoxic interface, three processes, nitrification, anammox and denitrification couple with each other, and significant anammox reaction could be observed. Soil parameters like pH, dissolved oxygen, salinity, oxidation-reduction potential (ORP), and substrate concentrations impact the anammox process. Here we summarize the current knowledge on anammox activity and contribution to N loss, abundance and diversity of anammox bacteria, factors affecting anammox, and the relationship between anammox and other N loss pathways in agricultural soils. We propose that more investigations are required for (1) the role of anammox to N loss with different agricultural management strategies; (2) microscale research on the coupling of nitrification-anammox-denitrification, that might be a very complex process but ideal model for further studies responsible for N cycling in terrestrial ecosystems; and (3) new methods to estimate differential contributions of anammox, codenitrification and denitrification in total N loss in agricultural ecosystems. New research will provide much needed information to quantify the contribution of anammox in N loss from soils at landscape, ecosystem and global scales.

Synthesis of a novel p-hydroxycinnamic amide with anticancer capability and its interaction with human serum albumin.

In the present study, a novel p-hydroxycinnamic amide (E)-3-(4-hydroxyphenyl)-N-(4-(N-(5-meth oxypyrimidin-2-yl)-sulfamoyl)phenyl)acrylamide (HMSP) was synthesized and confirmed. In vitro cytotoxic assays indicated that HMSP was able to inhibit the proliferation of various cancer cell lines. The interaction between HMSP and human serum albumin (HSA) was examined by fluorescence, UV-Vis and circular dichroism (CD) spectra, in addition to molecular simulation. The fluorescence and UV-Vis spectra data indicated that the binding of HMSP with HSA was a static process. According to the fluorescence quenching calculation, the corresponding thermodynamic parameters, bimolecular quenching rate constant and apparent quenching constants were calculated. Van der Walls forces and hydrogen bonds were vital in the binding of HMSP on HSA. The distances between HSA and its derivatives were obtained. Furthermore, competitive experiments and molecular modeling results suggested that the binding of the compound on HSA mainly occurred in site I (sub-domain IIA). Changes in HSA conformation were observed from synchronous fluorescence and CD spectra, which were further investigated by molecular dynamic simulations.

Simultaneous nitrification and denitrification in step feeding biological nitrogen removal process.

The simultaneous nitrification and denitrification in step-feeding biological nitrogen removal process were investigated under different influent substrate concentrations and aeration flow rates. Biological occurrence of simultaneous nitrification and denitrification was verified in the aspect of nitrogen mass balance and alkalinity. The experimental results also showed that there was a distinct linear relationship between simultaneous nitrification and denitrification and DO concentration under the conditions of low and high aeration flow rate. In each experimental run the floc sizes of activated sludge were also measured and the results showed that simultaneous nitrification and denitrification could occur with very small size of floc.

Removal effect on Mesocyclops leukarti and mutagenicity with chlorine dioxide.

Mesocyclops leukurti of zooplankton propagates excessively in eutrophic water body and it cannot be effectively inactivated by the conventional drinking water treatment process. In order to tackle this problem, a study of removal effect on Mesocyclops leukarti with chlorine dioxide in a waterworks was performed. The results showed that Mesocyclops leukarti could be effectively removed from water by 1.0 mg/L chlorine dioxide preoxidation combined with the conventional drinking water treatment process. Higher oxidizability and molecular state of chlorine dioxide in water is the key to the inactivation of Mesocyclops leukarti. The chlorite, disinfection by-products (DBPs) of chlorine dioxide, was stable at 0.45 mg/L, which is lower than that critical value of the USEPA. GC-MS examination showed that the quantity of organic substance in the water treated by chlorine dioxide obviously decreased. Ames test further revealed that the mutagenicity was reduced by chlorine dioxide with respect to prechlorine. The propagation of Mesocyclops leukarti can be inactivated effectively and safely by chlorine dioxide pre-oxidation.

Automatic control strategy for step feed anoxic/aerobic biological nitrogen removal process.

Control of sludge age and mixed liquid suspended solids concentration in the activated sludge process is critical for ensuring effective wastewater treatment. A nonlinear dynamic model for a step-feed activated sludge process was developed in this study. The system is based on the control of the sludge age and mixed liquor suspended solids in the aerator of last stage by adjusting the sludge recycle and wastage flow rates respectively. The simulation results showed that the sludge age remained nearly constant at a value of 16 d in the variation of the influent characteristics. The mixed liquor suspended solids in the aerator of last stage were also maintained to a desired value of 2500 g/m3 by adjusting wastage flow rates.

Nitrogen loss by anaerobic oxidation of ammonium in rice rhizosphere.

Anaerobic oxidation of ammonium (anammox) is recognized as an important process for nitrogen (N) cycling, yet its role in agricultural ecosystems, which are intensively fertilized, remains unclear. In this study, we investigated the presence, activity, functional gene abundance and role of anammox bacteria in rhizosphere and non-rhizosphere paddy soils using catalyzed reporter deposition-fluorescence in situ hybridization, isotope-tracing technique, quantitative PCR assay and 16S rRNA gene clone libraries. Results showed that rhizosphere anammox contributed to 31-41% N2 production with activities of 0.33-0.64 nmol N2 g(-1) soil h(-1), whereas the non-rhizosphere anammox bacteria contributed to only 2-3% N2 production with lower activities of 0.08-0.26 nmol N2 g(-1) soil h(-1). Higher anammox bacterial cells were observed (0.75-1.4 × 10(7) copies g(-1) soil) in the rhizosphere, which were twofold higher compared with the non-rhizosphere soil (3.7-5.9 × 10(6) copies g(-1) soil). Phylogenetic analysis of the anammox bacterial 16S rRNA genes indicated that two genera of 'Candidatus Kuenenia' and 'Candidatus Brocadia' and the family of Planctomycetaceae were identified. We suggest the rhizosphere provides a favorable niche for anammox bacteria, which are important to N cycling, but were previously largely overlooked.