Willow can be recommended as a strong candidate for the phytoremediation of cadmium and pyrene co-polluted soil under flooding condition.

Soil cadmium (Cd) and pyrene (PYR) pollutions have gained worldwide attention due to their negative effects on the environment. Intermittent flooding in rain-rich areas may affect phytoremediation of Cd and PYR in soil. Therefore, a pot-culture experiment, with and without flooding, was conducted to study the effects of flooding on soil Cd and PYR phytoremediation. Concentrations of Cd, PYR, and nutrients in soils and plants, as well as plant physiological and biochemical responses, were examined. Under both flooding and non-flooding conditions, willow (Salix × aureo-pendula CL 'J1011') demonstrated a better ability to remove soil Cd and PYR. Flooding led to higher Cd accumulation in roots than that in shoots. Conversely, non-flooding resulted in higher Cd accumulation in shoots than that in roots. The maximum concentrations of Cd in shoots were 11.02 and 14.07 mg kg-1 with and without flooding, respectively. The maximum dissipation rates of PYR in soil were 47.35% and 88.61% under flooding and non-flooding conditions, respectively. In addition, flooding significantly increased the photosynthetic pigment, photosynthetic fluorescence, and chlorophyll fluorescence parameters in leaves, compared with non-flooding treatment. Flooding also increased the concentrations of Mg, Mn, P, Fe, and K in roots and shoots. This study outlines an effective insight for the phytoremediation of Cd- and PYR-contaminated soil under flooding condition.

Li Y ，Zha Y ，Wang G ，Xie T ，Zhao C ，Yin Y ，Guo H ... -  《-》

Urea-enhanced phytoremediation of cadmium with willow in pyrene and cadmium contaminated soil.

The phytoremediation of cadmium (Cd) and pyrene (PYR) in agricultural soil with willow was investigated by carrying out a pot-culture experiment in a greenhouse. The soil was incubated with urea 60 days before it was used for this experiment. The concentrations of Cd and PYR in soil and willow, the bioconcentration and transfer factors, the physiological and biochemical responses, and plant biomass production were determined at the end of the experiment. The phytoremediation with willow based on urea application was effective for enhancing the phytoremediation of Cd and PYR contaminated soil. Urea application did not affect the available Cd but increased the accumulation of soil Cd and the plant biomass of different parts of the willow. The removal rate (77.1-89.5%) of PYR in soil was not significantly affected although urea application decreased the accumulation of PYR in willow root and bark. Urea application significantly promoted the uptake of chlorophyll, carotenoid and malondialdehyde by willow leaves. The results of this study will provide scientific information for the effective phytoremediation of Cd in Cd and PYR contaminated soil.

Li Y ，Xie T ，Zha Y ，Du W ，Yin Y ，Guo H ... -  《-》

Phytoremediation of soils contaminated with phenanthrene and cadmium by growing willow (Salix × aureo-pendula CL 'j1011').

Sun YY ，Xu HX ，Li JH ，Shi XQ ，Wu JC ，Ji R ，Guo HY ... -  《-》

Ethyl lactate-EDTA composite system enhances the remediation of the cadmium-contaminated soil by autochthonous willow (Salix x aureo-pendula CL 'J1011') in the lower reaches of the Yangtze River.

In order to explore a practical approach to the remediation of the cadmium (Cd)-contaminated soil in the lower reaches of the Yangtze River, we evaluated the effects of a local willow (Salix x aureo-pendula CL 'J1011') of absorbing, accumulating, and translocating Cd; and assessed the potential of chelator ethylenediaminetetraacetic acid (EDTA) in combination with ethyl lactate for enhancing the efficiency of the willow in removing Cd in two water-culture growth chamber trials and a field one. The willow showed a high tolerance to Cd in growth chamber trial 1 where the Cd concentration in the medium reached up to 25 mg L(-1) medium, and the bioaccumulation factors (BAFs) of the shoots for Cd rose from 3.8 to 7.4 as the Cd concentration in the medium was elevated from 5 to 25 mg L(-1) medium. In growth chamber trial 2, the average Cd removal rates in two treatments with EDTA and ethyl lactate (molar ratios of EDTA to ethyl lactate=68/39 and 53.5/53.5, respectively) reached 0.71 mg d(-1) pot(-1) for the duration of Day 5-8 and 0.59 mg d(-1) pot(-1) for that of Day 8-11, which were 5- and 4-fold of their counterparts in the control, respectively. In the field trial, for the remediational duration of 45 days, three treatments-willow alone, willow combined with EDTA, and willow combined with EDTA and ethyl lactate-led to decreases in the Cd concentration in soil by 5%, 20%, and 29%, respectively; increases in that in the leaves by 14.6%, 56.7%, and 146.5%, respectively; and increases in that in the stems by 15.6%, 41.2%, and 87.4%, respectively, compared to their counterparts on Day 0. These results indicate that EDTA combined with ethyl lactate significantly enhanced the efficiency of willow in removing Cd from the soil. Therefore, a phytoextration system consisting of the autochthonous willow, EDTA, and ethyl lactate has high potential for the remediation of the Cd-polluted soil in the lower reaches of the Yangtze River.

Li J ，Sun Y ，Yin Y ，Ji R ，Wu J ，Wang X ，Guo H ... -  《-》

Microbial communities in the rhizosphere of different willow genotypes affect phytoremediation potential in Cd contaminated soil.

Plant-associated microorganisms play an important role in controlling heavy metal uptake and accumulation in aerial parts. The microbial community and its interaction with Cd accumulation by willow were assessed to explore the association of phytoextraction efficiency and rhizospheric microbial populations. Therefore, the rhizosphere microbial compositions of three willow genotypes grown in two Cd polluted sites were investigated, focusing on their interactions with phytoremediation potential. Principal coordinate analysis revealed a significant effect of genotype on the rhizosphere microbial communities. Distinct beneficial microorganisms, such as plant growth promoting bacteria (PGPB) and mycorrhizal fungi, were assembled in the rhizosphere of different willow genotypes. Linear mixed models showed that the relative abundance of PGPB was positively associated (p < 0.01) with Cd accumulation, since these microbes significantly increased willow growth. The higher abundance of arbuscular mycorrhizal fungi in the rhizosphere of Salix × aureo-pendula CL 'J1011' at the Kejing site, showed a negative correlation with the Cd content, but a positive correlation with biomass. Conversely, mycorrhizal fungi, were more abundant in the rhizosphere of S. × jiangsuensis CL. 'J2345' and positively correlated with the Cd content in willow tissues. This study provides new insights into the distinctive microbial communities in rhizosphere of different willow genotypes, which may be consistent with the phytoremediation potential.

Wang G ，Zhang Q ，Du W ，Ai F ，Yin Y ，Ji R ，Guo H ... -  《-》