Reduction of arsenic toxicity in two rice cultivar seedlings by different nanoparticles.

In this study, we investigated arsenic uptake and enzymatic activities in rice seedlings after the addition of nanoparticles. Hydroponic experiments were conducted to investigate the effects of different nanomaterials (high-quality graphene oxide, multilayer graphene oxide, 20 nm hydroxyapatite (HA20), 40 nm hydroxyapatite (HA40), nano-Fe3O4 (nFe3O4) and nano-zerovalent iron [nFe]) on the biomass, arsenic uptake, and enzyme activities in seedlings of the rice cultivars T705 and X24. Compared with the control, the addition of different nanomaterials increased seedling growth, with X24 rice growing better than T705 rice. Nanomaterials effectively reduced arsenic uptake in T705 rice seedlings under low and high arsenic concentrations; however, they were only effective at lower arsenic concentrations in X24 seedlings. nFe3O4 and nFe performed better than other nanomaterials in preventing arsenic from being transported to the aboveground parts of the rice seedlings. Different nanomaterials obviously influenced enzyme activities in the T705 seedlings at low arsenic concentrations (≤ 0.8 mg L-1). High-quality and multilayer graphene oxide decreased enzyme activities in the aboveground parts of the T705 seedlings, whereas, HA20 and HA40 increased the enzyme activities. nFe3O4 and nFe also reduced the effect of antioxidants in the aboveground parts of the T705 seedlings. Nanomaterials effectively reduced the arsenic uptake of T705 and X24 rice seedlings at low arsenic concentrations.

[Toxic effects of polystyrene and dibutyl phthalate on purple lettuce]. / èšè‹¯ä¹™çƒ¯ä¸Žé‚»è‹¯äºŒç”²é ¸äºŒä¸é ¯å ±å­˜å¯¹ç´«å¶ç”Ÿèœçš„æ¯’æ€§æ•ˆåº”.

As a carrier of environmental pollutants, microplastics have received wide concerns in recent years. However, the direct and indirect effects of the coexistence of polystyrene particles (PS) and pollutants on vegetables are still unclear. Here, the combined effects of 0.25, 0.50, 1.0 mg·mL-1 PS and 5 mg·L-1 dibutyl phthalate (DBP) on the biomass and biochemical indices of purple lettuce were investigated in hydroponic experiments. The results showed that the presence of PS increased the inhibition of DBP on lettuce biomass and increased O2-· content in roots and leaves relative to the control group with DBP alone, with positive consequences on the activities of supero-xide dismutase, ascorbic acid peroxidase, dehydroascorbate reductase and monodehydroascorbate reductase. According to transmission electron microscope analysis, plasmolysis occurred in root cells under the treatment of DBP alone, cell wall was damaged in PS-only treatment, and the negative effect was enhanced when DBP and PS coexisted. Therefore, the combined pollution of PS and DBP aggravated the toxic effect on purple lettuce.

[Effects of elevated CO2 on the Cd uptake and root morphology of different rice varieties under cadmium stress].

A hydroponic experiment was conducted to study the effects of elevated CO2 on the Cd uptake and root morphology of rice varieties Rongyou-398 (RY) and Yueza-889 (YZ) under different levels of Cd stress. Low levels (5, 10, and 20 micromol x L(-1)) Cd stress increased the biomass of the two rice varieties significantly, while high levels (> 50 micromol x L(-1)) Cd stress was in adverse. Elevated CO2 increased the varieties dry biomass significantly, and increased the stem Cd concentration of YZ but decreased that of RY. Under the stress of 5-200 micromol Cd x L(-1), elevated CO2 increased the proportion of active root length in total root length of YZ but decreased that of RY, which could be one of the main reasons for the difference in the Cd uptake of the two varieties under Cd stress.

[Effects of calcium on cadmium bioavailability in lateritic red soil and related mechanisms].

A pot experiment with Cd-polluted lateritic red soils was conducted to study the effects of applying different concentration (0, 40, 100, and 200 mg x kg(-1)) Ca on the rape biomass, its Cd uptake, and the Ca and Cd concentrations in soil solution. Comparing with no Ca application, applying Ca increased the rape dry mass, whether under high or low level Cd pollution. The increment of the dry mass in two cropping seasons was averagely 5.5% (low level Cd pollution) and 17.3% (high level Cd pollution). The Ca concentration both in soil solution and in rape plant increased markedly with increasing Ca application rate. At the Ca application rate 100 mg x kg(-1), the Cd concentration in soil solution increased by 74.5% (low Cd pollution) and 31.0% (high level Cd pollution), while that in rape plant decreased by 4.5% (low Cd pollution) and 13.1% (high level Cd pollution). There was a positive relationship between the Ca/Cd (mass ratio) in soil solution and the Cd concentration in rape plant under both low and high levels Cd pollution. The Ca/Cd (mass ratio) in soil solution affected the bioavailability of soil Cd, and further, affected the Cd up-take by rape.

[Effects of different potassium fertilizers on the phytoavailability of Pb in soil and its mechanisms].

Effects of four kinds of potassium fertilizer (KH2PO4, K2SO4, KNO3 and KCl) in its conventional application rate as K, 0.11 g x kg(-1) on the Pb absorption by rape and speciation of Pb in paddy soil were examined by pot trial. Results showed that the Pb content in rape decreased with using KH2PO4 and K2SO4, and in the second season of pot trial for KH2PO4 treatment, Pb content in rape shoots under Pb1 (300 mg x kg(-1)) and Pb2 (500 mg x kg(-1)) level decreased by 35.6% and 45.4% respectively compared with control treatment. Applied KNO3 in soil also decreased Pb content in rape shoots to some extent, but KCl had adverse effect. At lower Pb level (300 mg x kg(-1)), KH2 PO4 and K2SO4 caused Pb in soil transformed from non-residual fractions to residual fraction substantially and for higher Pb level (500 mg x kg(-1)) only KH2PO4 application had similar effect. Under two contaminated Pb levels, exchangeable and carbonate fraction Pb in soil by using KCl were all enhanced, which indicated that KCl could promote the phytoavailability of Pb. As thus one of the most important mechanisms of potassium fertilizers influencing Pb phtoavailability was changing the speciation of Pb in soil.