Soil CO_2efflux(SCE) is an important component of ecosystem CO_2 exchange and is largely temperature and moisture dependent, providing feedback between C cycling and the climate system. We used a precipitation manipulation experiment to examine the effects of precipitation treatment on SCE and its dependences on soil temperature and moisture in a semiarid grassland. Precipitation manipulation included ambient precipitation, decreased precipitation(- 43%), or increased precipitation(+ 17%). The SCE was measured from July2013 to December 2014, and CO_2 emission during the experimental period was assessed.The response curves of SCE to soil temperature and moisture were analyzed to determine whether the dependence of SCE on soil temperature or moisture varied with precipitation manipulation. The SCE significantly varied seasonally but was not affected by precipitation treatments regardless of season. Increasing precipitation resulted in an upward shift of SCE–temperature response curves and rightward shift of SCE–moisture response curves,while decreasing precipitation resulted in opposite shifts of such response curves. These shifts in the SCE response curves suggested that increasing precipitation strengthened the dependence of SCE on temperature or moisture, and decreasing precipitation weakened such dependences. Such shifts affected the predictions in soil CO_2 emissions for different precipitation treatments. When considering such shifts, decreasing or increasing precipitation resulted in 43 or 75% less change, respectively, in CO_2 emission compared with changes in emissions predicted without considering such shifts. Furthermore, the effects of shifts in SCE response curves on CO_2 emission prediction were greater during the growing than the non-growing season. 相似文献
Water pollution by antibiotics is an increasing concern, which may be addressed by advanced oxidation processes using sulfites as precursors of sulfate radicals (SO4·–), yet the efficiency of sulfite activation is limited. Here, we tested copper cobalt sulfide (CuCo2S4) to activate sulfite, based on the synergy among transition metals and the facilitation of transition metal redox circulation by reductive sulfur species. We analyzed CuCo2S4 structure by X-Ray photoelectron spectroscopy, and we studied the effect of pH and radical scavengers. Results show 90–100% abatement of tetracycline concentration at pH 8.0–10.0, with SO4·– and HO· as the main reactive radicals. This finding is explained by the accelerated redox recycling of copper and cobalt by sulfur, and by the synergetic effect between active cobalt and copper sites.
• A full scale biofilm process was developed for typical domestic wastewater treatment.• The HRT was 8 h and secondary sedimentation tank was omitted.• Candidatus Brocadia were enriched in the HBR with an abundance of 2.89%.• Anammox enabled a stable ammonium removal of ~15% in the anoxic zone. The slow initiation of anammox for treating typical domestic wastewater and the relatively high footprint of wastewater treatment infrastructures are major concerns for practical wastewater treatment systems. Herein, a 300 m3/d hybrid biofilm reactor (HBR) process was developed and operated with a short hydraulic retention time (HRT) of 8 h. The analysis of the bacterial community demonstrated that anammox were enriched in the anoxic zone of the HBR process. The percentage abundance of Candidatus Brocadia in the total bacterial community of the anoxic zone increased from 0 at Day 1 to 0.33% at Day 130 and then to 2.89% at Day 213. Based upon the activity of anammox bacteria, the removal of ammonia nitrogen (NH4+-N) in the anoxic zone was approximately 15%. This showed that the nitrogen transformation pathway was enhanced in the HBR system through partial anammox process in the anoxic zone. The final effluent contained 12 mg/L chemical oxygen demand (COD), 0.662 mg/L NH4+-N, 7.2 mg/L total nitrogen (TN), and 6 mg/L SS, indicating the effectiveness of the HBR process for treating real domestic wastewater. 相似文献
Introduction Environm ental and econom ic advantages highlight anaerobic digestion as a sustainable technology for solid w aste treatm ent (Edelm ann etal., 2000). A naerobic digestion could be described as four sequential steps: hydrolysis, acidogenesis, aceto- genesis and m ethanogenesis, am ong w hich the hydrolysis is recognized as the rate-lim iting step for particulate organic w aste (Jain et al., 1992; M ata-A lvarez, 2000). H ydrolysis occurs com m only together w ith the acidogenesi… 相似文献