Electrocoagulation coupled with electrooxidation for the simultaneous treatment of multiple pollutants in contaminated sediments

In situ and simultaneous remediation of a variety of pollutants in sediments remains a challenge.In this study,we report that the combination of electrocoagulation(EC)and electrooxidation(EO)is efficient in the immobilization of phosphorus and heavymetals and in the oxidation of ammonium and toxic organicmatter.The integratedmixed metal oxide(MMO)/Fe anode system allowed the facile removal of ammonium and phosphorus in the overlying water(99% of 10 mg/L NH_(4)^(+)-N and 95% of 10 mg/L P disappeared in 15 and 30 min,respectively).Compared with the controls of the single Fe anode and single MMO anode systems,the dual MMO/Fe anode system significantly improved the removal of phenanthrene and promoted the transition of Pb and Cu from the mobile species to the immobile species.The concentrations of Pb and Cu in the toxicity characteristic leaching procedure extracts were reduced by 99%and 97% after an 8 hr operation.Further tests with four real polluted samples indicated that substantial proportions of acid-soluble fraction Pb and Cu were reduced(30%-31% for Pb and 16%–23% for Cu),and the amounts of total organic carbon and NH_(4)^(+)-N decreased by 56%–71% and 32%–63%,respectively.It was proposed that the in situ electrogenerated Fe(II)at the Fe anode and the active oxygen/chlorine species at the MMO anode are conducive to outstanding performance in the co-treatment of multiple pollutants.The results suggest that the EC/EO method is a powerful technology for the in situ remediation of sediments contaminated with different pollutants.

近年中国北方草地变绿受降水增加的驱动

中国北方的暖湿化是近期的热点话题,然而其对植被生长的影响仍不清楚。本研究基于长时间序列(1982–2018年)数据,研究了归一化植被指数(NDVI)的时间动态及其气候驱动因子之间的关系,以探索近年来气候的暖湿化是否会导致该区植被变绿。我们采用分段回归探测了NDVI的变化趋势是否存在转变点,用Pearson相关分析描述了植被指数与气候因子的关系。最后,采用逐步多元回归方法研究了气候因子对NDVI时间变化的贡献率。研究结果表明,NDVI时间变化趋势的转变点出现在2008年,GIMMS NDVI在1982–2008年略有增加,上升速率为0.00022 yr?1,在2008–2015年上升速率达到0.002 yr?1,MODIS NDVI在2008–2018年上升速率为0.0018 yr?1。降水是NDVI变化的主要驱动因子,气温和饱和水汽压差(VPD)对NDVI的变化影响较小。总体看来,NDVI时间序列变化趋势存在转变点,并且近期气候的暖湿化主导了中国北方草地植被变绿,这为今后更好地预测该地区气候变化下的植被覆盖变化提供了依据。