Multiple copper adsorption and regeneration by zeolite 4A synthesized from bauxite tailings

Copper ions were first adsorbed by zeolite 4A synthesized from bauxite tailings, the desorption of Cu(II) using Na₂EDTA solutions was performed, and the recycling of zeolite 4A in adsorption and desorption was systematically investigated. It was observed that the Cu(II) removal efficiency was directly dependent on the initial pH value. The maximum removal efficiency of Cu(II) was 96.2% with zeolite 4A when the initial pH value was 5.0. Cu(II) was completely absorbed in the first 30 min. It was also observed that the desorption efficiency and zeolite recovery were highly dependent on the initial pH and concentration of Na₂EDTA in the solution. The desorption efficiency and percent of zeolite recovered were 73.6 and 85.9%, respectively, when the Na₂EDTA solution concentration was 0.05 mol L^?1 and the pH value was 8. The recovered zeolites were pure single phase and highly crystalline. After 3 cycles, the removal efficiency of Cu(II) was as high as 78.9%, and the zeolite recovery was 46.9%, indicating that the recovered zeolites have good adsorption capacity and can repeatedly absorb Cu(II).

     

入侵物种三裂叶蟛蜞菊挥发物的化感作用研究

对华南地区重要外来入侵物种三裂叶蟛蜞菊挥发物的化感作用进行了研究,以揭示该物种的入侵机制。采用水蒸气蒸馏法提取三裂叶蟛蜞菊地上部分的挥发油,提取率为2.58‰(质量比)。以稗草、三叶鬼针草和青葙3种杂草种子为供试对象,用种子萌发法测定了三裂叶蟛蜞菊挥发物的化感作用活性。结果表明:三裂叶蟛蜞菊的茎叶在密闭系统中产生的挥发性物质对稗草、三叶鬼针草和青葙的幼苗生长有显著抑制作用。稗草的根长、苗高和鲜质量分别比对照减少49.1%、35.0%和27.3%,三叶鬼针草的分别比对照减少18.8%、20.9%和28.6%,青葙的分别比对照减少62.9%、21.2%和50.0%。水蒸气蒸馏法所得的挥发油对稗草、三叶鬼针草和青葙的幼苗生长也有显著抑制作用,且抑制作用随着浓度的增大而增强。稗草的根长、苗高和鲜质量分别比对照减少88.2%、58.3%和45.5%,三叶鬼针草的根长、苗高和鲜质量分别比对照减少38.6%、34.5%和71.4%,青葙的根长、苗高和鲜质量分别比对照减少83.7%、51.5%和75.0%。结论:三裂叶蟛蜞挥发物具有化感作用,其作用机理值得深入研究。     

入侵物种三裂叶蟛蜞菊挥发物对杂草叶绿素含量的影响

研究了华南地区外来入侵植物三裂叶蟛蜞菊（Wedelia trilobata L.）挥发物对本地区3种主要杂草的叶绿素含量的影响,以揭示其化感作用的机理。结果表明：三裂叶蟛蜞菊植株挥发物和挥发油对稗草（Echinochloa crusgalli（L.）Beauv.）、三叶鬼针草（Bidens pilosa L.）和青葙（Celosia argentea L.）叶绿素含量有明显的抑制作用。在同一实验条件下,250.0 g三裂叶蟛蜞菊新鲜茎叶及含有0.10 mL、0.25 mL和0.50 mL挥发油容器中生长的稗草、三叶鬼针草和青葙的叶绿素含量明显减少,稗草的叶绿素含量分别比对照减少56.5%、41.9%、49.6%和64.9%;三叶鬼针草的叶绿素含量分别比对照减少6.45%、4.35%、15.3%和24.8%;青葙的叶绿素含量分别比对照减少53.3%、17.6%、33.3%和71.5%。结论：三裂叶蟛蜞菊挥发物的化感作用可使受体植物的叶绿素含量减少。其作用机理值得深入研究。     

入侵物种三裂叶蟛蜞菊挥发物对杂草叶绿素含量的影响

研究了华南地区外来入侵植物三裂叶蟛蜞菊(Wedelia trilobata L.)挥发物对本地区3种主要杂草的叶绿素含量的影响,以揭示其化感作用的机理。结果表明:三裂叶蟛蜞菊植株挥发物和挥发油对稗草(Echinochloa crusgalli(L.)Beauv.)、三叶鬼针草(Bidens pilosa L.)和青葙(Celosia argentea L.)叶绿素含量有明显的抑制作用。在同一实验条件下,250.0 g三裂叶蟛蜞菊新鲜茎叶及含有0.10 mL、0.25 mL和0.50 mL挥发油容器中生长的稗草、三叶鬼针草和青葙的叶绿素含量明显减少,稗草的叶绿素含量分别比对照减少56.5%、41.9%、49.6%和64.9%;三叶鬼针草的叶绿素含量分别比对照减少6.45%、4.35%、15.3%和24.8%;青葙的叶绿素含量分别比对照减少53.3%、17.6%、33.3%和71.5%。结论:三裂叶蟛蜞菊挥发物的化感作用可使受体植物的叶绿素含量减少。其作用机理值得深入研究。     

Sorption and bioreduction of hexavalent uranium at a military facility by the Chesapeake Bay

Directly adjacent to the Chesapeake Bay lies the Aberdeen Proving Ground, a U.S. Army facility where testing of armor-piercing ammunitions has resulted in the deposition of >70,000 kg of depleted uranium (DU) to local soils and sediments. Results of previous environmental monitoring suggested limited mobilization in the impact area and no transport of DU into the nation's largest estuary. To determine if physical and biological reactions constitute mechanisms involved in limiting contaminant transport, the sorption and biotransformation behavior of the radionuclide was studied using geochemical modeling and laboratory microcosms (500 ppb U(VI) initially). An immediate decline in dissolved U(VI) concentrations was observed under both sterile and non-sterile conditions due to rapid association of U(VI) with natural organic matter in the sediment. Reduction of U(VI) to U(IV) occurred only in non-sterile microcosms. In the non-sterile samples, intrinsic bioreduction of uranium involved bacteria of the order Clostridiales and was only moderately enhanced by the addition of acetate (41% vs. 56% in 121 days). Overall, this study demonstrates that the migration of depleted uranium from the APG site into the Chesapeake Bay may be limited by a combination of processes that include rapid sorption of U(VI) species to natural organic matter, followed by slow, intrinsic bioreduction to U(IV).     

High mercury leachate containing HgS22 − complex ion: Detoxifying solidification and high efficiency Hg extraction

Clean and efficient treatment of high-mercury leachate produced from remediation of mercury-polluted soil has become a huge challenge for environmental scientists.In this work,cement solidification was firstly adopted to treat the high-concentration mercury leachate,which had high alkalinity.Different mercury concentrations,namely 3.120 mg/L Hg mercury leachate and 9.243 mg/L Hg mercury concentrated leachate,were separately solidified by Portland cement.The results indicated that simply using the cement can properly solidify both the leachates to meet the waste landfill standard,with liquid(mL)/solid(g) ratio(L/S ratio) of4:10–6:10.In order to make full use of mercury in the leachates,a Hg extraction method was subsequently carried out under different experimental parameters,such as temperature and p H value.It was shown that the Hg extraction ratio could reach as high as 99.84% and almost all the mercury in the leachate could be transformed to HgS precipitate;moreover,the Hg concentration in the treated leachate was reduced from 3.120 to 0.005 mg/L at p H 2.98 and 30°C,which was much less than the limit of the national standard,indicating that the leachate had been completely cleaned and could be discharged freely.Hence,simple cement solidification renders high-mercury leachate nontoxic,and the Hg extraction method can successfully recover the Hg and enable the residual leachate to be discharged safely.     

杜鹃红山茶(Camellia changii Ye)的扦插苗、嫁接苗和砧木的光合作用特征

杜鹃红山茶(Camellia changii Ye)是山茶科全年开花的珍稀种类,其自然繁殖能力差,需要人工辅助的传粉、扦插或嫁接进行繁殖。本文研究了杜鹃红山茶扦插苗、嫁接苗及其砧木(油茶,Camellia oleifera Abel)3种苗木的叶绿素荧光参数和光合作用参数。结果显示,砧木及杜鹃红山茶的嫁接苗和扦插苗的叶片电子传递速率光曲线均随着光合有效辐射的增强而逐渐升高至最大值,后趋于相对稳定或略有下降,其光饱和点均在800~1 000μmol.m-2.s-1附近。研究还表明,3种苗木的最大光化学效率(Fv/Fm)、实际光化学效率(ΦPSII)、光化学荧光淬灭(qP)、相对电子传递速率(rETR)、最大净光合速率(Pmax)、蒸腾速率(Tr)、瞬时水分利用效率(IWUE)和瞬时光能利用效率(ILUE)均表现为砧木>嫁接苗>扦插苗,而非荧光淬灭(NPQ)的大小顺序则为:扦插苗>嫁接苗>砧木。这些结果表明,在这3种苗木中,砧木具有高光合、高蒸腾的特点,而扦插苗的光合蒸腾能力最弱。从光合生理的角度表明砧木适应能力最强、扦插苗最弱,而嫁接苗适应能力居中,商品化生产苗木可采用嫁接方式。