Phytoremediation potential of charophytes: Bioaccumulation and toxicity studies of cadmium, lead and zinc

The ability for usage of common freshwater charophytes,Chara aculeolata and Nitella opaca in removal of cadmium (Cd),lead (Pb) and zinc (Zn) from wastewater was examined.C.aculeolata and N.opaca were exposed to various concentrations of Cd (0.25 and 0.5 mg/L),Pb (5 and 10 mg/L) and Zn (5 and 10 mg/L) solutions under hydroponic conditions for 6 days.C.aculeolata was more tolerant of Cd and Pb than N.opaca.The relative growth rate of N.opaca was drastically reduced at high concentrations of Cd and Pb although both were tolerant of Zn.Both macroalgae showed a reduction in chloroplast,chlorophyll and carotenoid content after Cd and Pb exposure,while Zn exposure had little effects.The bioaccumulation of both Cd and Pb was higher in N.opaca (1544.3 μg/g at 0.5 mg/L Cd,21657.0 μg/g at 10 mg/L Pb) whereas higher Zn accumulation was observed in C.aculeolata (6703.5 μg/g at 10 mg/L Zn).In addition,high bioconcentration factor values (> 1000) for Cd and Pb were observed in both species.C.aculeolata showed higher percentage of Cd and Pb removal (> 95%) than N.opaca and seemed to be a better choice for Cd and Pb removal from wastewater due to its tolerance to these metals.     

纳米二氧化钛胁迫对普生轮藻的毒性效应

纳米材料独特的理化性质使其得到了广泛的应用,但其可能带来的生物安全性问题也引起了广泛关注.实验研究了胁迫浓度梯度为0、0.01、0.10、1.0、10、100mg.L-1的纳米二氧化钛(nTiO2)悬浮液单一处理普生轮藻(CharavulgarisL.)的毒性效应,在胁迫24h、48h、72h、96h后分别测定其叶绿素a含量、脂质过氧化物丙二醛(MDA)含量、超氧化物歧化酶(SOD)活性和过氧化氢酶(CAT)活性.结果表明,随着胁迫浓度的增加和时间的延长,叶绿素a含量、SOD和CAT活性总体呈下降趋势,而MDA含量呈递增趋势,高浓度剂量组与对照组比较差异极显著,酶的活性降幅也较大,说明急性nTiO2暴露对普生轮藻具有毒性作用,且表现出剂量效应.     

On the tolerance of charophytes to high-nitrate concentrations

Currently a debate exists about whether the reduced growth of macrophytes with increased nitrogen loading in shallow ecosystems is determined by ecological or physiological factors. To discover whether nitrate in the water is detrimental per se to charophytes, we subjected Chara hispida and Chara vulgaris specimens, collected from two habitats greatly differing in nitrate concentrations (1.5 and 10?mg NO₃-N/L, annual means), to a wide nitrate range (0.5–50?mg NO₃-N/L) in two experiments (with free-floating specimens using nitrate as the sole N source, and with planted specimens, with other N sources in sediment). Charophytes grew both unplanted and planted in all treatments, and growth reductions occurred at the highest concentration in all cases. Some charophyte responses when faced with nitrate increases were different depending on (i) the species and (ii) population origin. Under the most realistic situation, the growth of both planted C. vulgaris populations was higher than that of C. hispida populations. C. vulgaris specimens from the nitrate-rich waterbody adapted best to the highest nitrate concentrations when they grew floating. Despite charophytes being vital and growing under high-nitrate concentrations in short-term laboratory experiments, such a situation in the environment may eventually not be sustainable, since ecological factors act in the field.