Can liming change root anatomy, biomass allocation and trace element distribution among plant parts of Salix × smithiana in trace element-polluted soils?

Is the harvest of Salix and Populus clones in the growing season truly advantageous for the phytoextraction of metals from a long-term perspective?

The phytoextraction potential of short-rotation field coppice plantations was investigated on soil historically contaminated with risk elements (REs), especially Cd, Pb and Zn. The main objective of the study was to assess the effect of biomass harvest time (summer harvest versus traditional winter one) on biomass yield, REs accumulation and removal in the long-term study. The precise field experiment with two Salix clones and two Populus clones was established in April 2009. Shoots of all clones were harvested in February 2012 for the first time, and then identical branches and leaves were harvested every two years in September (summer harvest = SH) and the branches every two years in February (winter harvest = WH). The first summer harvest seemed to be more promising compared to the winter one, but the yields in the second and third harvests were inconsistent. The total phytoextraction efficiency of the SH declined in second and third harvests due to a decrease of leaves/aboveground biomass ratio, and the RE concentrations in leaves. Clonal Salix smithiana was the most productive one in the SH, with a dry matter yield of 15.1 t ha^-1 year^-1 and showed promising extraction ability for Cd (11.65 %) and Zn (4.59 %) over a 6-year field experiment. A lower portion of Cd (6.97 %) and Zn (2.38 %) was removed by this clone in the WH (calculated from the total soil content of REs). SH was more reasonable for phytoextraction compared to WH. Higher RE concentrations were found in leaves of Salix compared to Populus. Populus accumulated the highest Pb content in the branches; unfortunately, the Pb extraction was low, due to extremely high soil Pb contamination. Locally bred willows and poplars performed substantially better than internationally recognised ones, indicating the importance of phytoremediation optimisation, including clone selection, for suitable climatic conditions.

Understanding Potential Heavy Metal Contamination, Absorption, Translocation and Accumulation in Rice and Human Health Risks

Rice is a worldwide staple food and heavy metal contamination is often reported in rice production. Heavy metal can originate from natural sources or be present through anthropogenic contamination. Therefore, this review summarizes the current status of heavy metal contamination in paddy soil and plants, highlighting the mechanism of uptake, bioaccumulation, and health risk assessment. A scoping search employing Google Scholar, Science Direct, Research Gate, Scopus, and Wiley Online was carried out to build up the review using the following keywords: heavy metals, absorption, translocation, accumulation, uptake, biotransformation, rice, and human risk with no restrictions being placed on the year of study. Cadmium (Cd), arsenic (As), and lead (Pb) have been identified as the most prevalent metals in rice cultivation. Mining and irrigation activities are primary sources, but chemical fertilizer and pesticide usage also contribute to heavy metal contamination of paddy soil worldwide. Further to their adverse effect on the paddy ecosystem by reducing the soil fertility and grain yield, heavy metal contamination represents a risk to human health. An in-depth discussion is further offered on health risk assessments by quantitative measurement to identify potential risk towards heavy metal exposure via rice consumption, which consisted of in vitro digestion models through a vital ingestion portion of rice.

Lead-induced oxidative stress triggers root cell wall remodeling and increases lead absorption through esterification of cell wall polysaccharide

Tall fescue (Festuca arundinacea Schreb) shows remarkable tolerance to lead (Pb), but the mechanisms involved in metal tolerance are not yet well understood. Here, tall fescue were firstly cultivated hydroponically with Pb²⁺ (0, 50, 200 and 1000 mg/L) for 14 days. The results showed that remodeling of root architecture plays important roles in tolerance of tall fescue to Pb²⁺ stress. Increased cell wall (CW) components contribute to restrict high amount of Pb²⁺ in roots. Additionally, the uronic acid contents of pectin, hemicellulose 1 (HC1) and hemicellulose 2 (HC2) increased under Pb²⁺ stress. We further observed that tall fescue cultivated with H₂O₂ showed similar remodeling of root architecture as Pb²⁺ treatment. Furthermore, pectin, HC1 and HC2 fractions were sequentially extracted from 0 and 10 mM H₂O₂ treated roots, and Pb²⁺ adsorption capacity and contents of carboxyl groups of pectin and HC2 fractions were steadily increased under H₂O₂ treatment in vitro. Our results suggest that degrees of esterification of pectin and HC2 are regulated by H₂O₂. High amount of low-esterified pectin and HC2 offer more carboxyl groups, provide more Pb²⁺ binding sites, and restrict more Pb²⁺ in the CW, which may enhance tolerance of tall fescue to Pb²⁺ stress.

An ecological microsystem to treat waste oil contaminated soil: Using phytoremediation assisted by fungi and local compost, on a mixed-contaminant site, in a cold climate

As a result of anthropization and industrialization, northern remote communities face issues of soil contamination by mixtures of organic and inorganic contaminants. Soil bioremediation in cold environments is particularly challenging because of slower degradation rates, slower production of biomass for phytoextraction of trace elements (TEs), and remoteness, which can complicate logistics and inflate costs. This study evaluated a decontamination approach integrating indigenous willows, fungi and compost in a northern community. The site was a waste oil pit and its soil was initially contaminated with petroleum hydrocarbons (PHC) exceeding 200 g kg^-1 and TEs including As, Cd, Co, Cr, Cu, Pb and Zn. In under five years, 65 and 75% of PHC (C6-C50 and >C50) were degraded, compared to 27 and 13% for the untreated control soil. We found contrasting TE translocation patterns to the aboveground biomass for the willow species used (Salix planifolia and Salix alaxensis), as well as distinctive rooting strategies. Hazard quotients were calculated to assess the risk plant material could pose to local wildlife. The highest TE concentration measured was Zn in S. planifolia, which exceeded Canadian soil guidelines. Results indicate toxicity risks to animals linked to TEs in Salix spp. leaves is generally unlikely. The fungus Trametes versicolor inoculated into the soil did not fruit, however fruiting bodies of Psathyrella sp. were observed consistently (four out of five years). Biological tests indicated that in five growing seasons soil toxicity significantly decreased compared to the untreated soil used as control. This was demonstrated by vegetation cover (137 vs 11% cover), toxicity assays on earthworms (Eisenia andrei) (0 vs 33% mortality) and barley seed germination (Hordeum vulgare) (86 vs 62% germination). The proposed decontamination approach, without the use of synthetic fertilizers, is promising for the PHC remediation of mixed-contaminants on cold climate sites.