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The potential of 32 frequently studied ornamental and/or energy grasses and two cadmium/zinc hyperaccumulators for phytoextraction and phytostabilization was compared by their growth in a historically contaminated soil over a three-month pot experiment. Shoot and root biomasses varied by factors of 14.2 and 62.7, respectively. Mainly due to their large biomass, Napier grass (Pennisetum purpureum ‘Purple’) and variegated giant reed (Arundo donax var. versicolor) accumulated cadmium and zinc contents in shoots up to 109.3% and 55.4% higher, respectively, than those in the cadmium/zinc hyperaccumulators, despite their lower metal concentrations. Pennisetum purpureum ‘Purple’ accumulated the most zinc and the third highest cadmium in roots. Bioconcentration factors of cadmium in roots were greater than 1 for 19 grasses. The present study demonstrated that many of these grasses may be suitable for phytostabilization of soil cadmium. Arundo donax var. versicolor exhibited the most potential for phytoextraction of soil zinc, whereas Pennisetum purpureum ‘Purple’ was best for phytoextraction and phytostabilization of cadmium and phytostabilization of zinc. Ornamental/energy grasses may have greater potentials for soil remediation than hyperaccumulators, especially given their utility and eco-economic benefits. The considerable variation in their performance emphases the value of screening to select the most effective candidates.

Pennisetum grasses (P. purpureum Schumach. ‘Purple’, P. alopecuroides (L.) Spreng. ‘Liren’ and P. alopecuroides (L.) Spreng. ‘Changsui’), and a cadmium (Cd) hyperaccumulator (Thlaspi caerulescens J.Presl & C.Presl), were grown in soil with four Cd addition levels of 0, 2, 20 and 200 mg/kg. Toxicity symptoms were not observed although growth of all plants decreased as Cd addition increased. Shoot bioconcentration factor (BCFS), the translocation factor (TF) and shoot accumulation of Cd for most plants first increased and then declined as Cd concentrations increased. In contrast, the root bioconcentration factor (BCFR) for T. caerulescens declined and root Cd accumulation for T. caerulescens and two P. alopecuroides cultivars increased consistently as Cd levels increased. P. purpureum had the largest biomass with shoot Cd accumulation similar to that of T. caerulescens, despite lower foliar Cd concentration. Although shoot Cd concentrations of two P. alopecuroides cultivars were lower than for P. purpureum, root Cd concentrations were greater. P. purpureum had Cd BCFS and TF (> 1) at 2- and 20-mg/kg Cd addition treatments, similar to T. caerulescens. P. alopecuroides cultivars had Cd BCFR (> 1) and TF (< 1) at all Cd levels. Roots did not affect rhizosphere pH. However, concentrations of acid extractable Cd in rhizosphere soil were lower than those of corresponding non-rhizosphere soil at all Cd levels for T. caerulescens and P. purpureum; T. caerulescens and P. purpureum did not affect less bioavailable Cd fractions. Concentrations of acid extractable Cd in the rhizosphere of the P. alopecuroides cultivars were not reduced at any Cd level. Differences in Cd accumulation among the three Pennisetum grasses were mainly attributable to root biomass and Cd TFs rather than rhizosphere Cd mobility.

Arsenic (As) is a metalloid toxic to organisms including humans. Arsenic in rice represents a significant exposure pathway for the general population, particularly for those subsisting on rice. Arsenic transformation, namely reduction, oxidation and methylation, in soil-rice systems has fundamental impacts on its mobility and toxicity. In addition to soil chemical properties (pH, Eh, metallic oxides, organic matter), microorganisms play critical roles in As transformation and mobility in paddy soil, such as through ArsM (As(III) S-adenosylmethyltransferase) and interactions with iron oxides or organic matters. Arsenic species in paddy soil directly influence As speciation in rice grain because the methylated As species in rice are mainly derived from microbial methylation in paddy soil. This paper aims to provide an overview on the status of the knowledge and gaps on the chemical aspects of As transformation in soil-rice system in conjunction with microbial ecology and functional genes. In addition, potential pathways (manipulation of microorganisms in paddy soil and genetic engineering) to decrease total As and/or inorganic As in rice grain are proposed.

The physical model of two-dimensional suerconducting photonic crystal is established.Taking atomic non-harmonic oscillation into account with the help of two-fluid model,the equation of photonic band structure is obtained using the method of plane wave expansion.Taking a superconducting photonic crystal YBaCuO as example,the influences of temperature on the photonic band structure are analyzed.The calculations show that the two-dimensional photonic crystals have the wider band gaps at the lower temperature,which narrows with the increases of temperature.