Valuable alkaloids content is preserved in Camptotheca acuminata and Morus alba grown in trace elements contaminated soil.

Phytoextraction of trace elements (TE) using woody species is an economically challenging soil remediation approach because of the long time needed. Yet, some trees contain alkaloids that can be exploited along structural components to enhance biomass value. As alkaloids are thought to be involved in plant defence mechanisms, we hypothesized that potentially hostile phytoremediation conditions could increase their level. Camptothecin in Camptotheca acuminata and 1-deoxynojirimycin in Morus alba were measured from trees grown in a field in presence of Cu, Pb and Zn all together, and from M. alba grown in a greenhouse in presence of Cd or other abiotic stressors (NaCl and bending). The trees did not extract TE in the field, but M. alba stems accumulated Cd in the greenhouse experiment, with no consequence on stomatal conductance and leaves pigments concentration. Camptothecin and 1-deoxynojirimycin concentrations were preserved under all experimental conditions, as was biomass yield, and phenolics were slightly increased in M. alba exposed to TE. This study provides evidence that valuable and persistent alkaloids and phenolics can be extracted from trees facing phytoremediation-associated stresses, without a negative impact on their quantity and on biomass yield. Such products could generate a sustainable stream of revenues during phytoremediation.

There is scarce data on tree alkaloid content and scarcer data on how it is affected by exposure to trace elements in a phytoremediation context. We provide evidence that the content of two specific alkaloids is not altered in Morus alba and Camptotheca acuminata exposed to moderate to elevated levels of contaminating trace elements. The manuscript introduces the use of M. alba for phytoremediation in the Americas and is the first to propose the use of C. acuminata on trace element contaminated sites to produce camptothecin, a valuable anticancer alkaloid.

The use of willow microcuttings for phytoremediation in a copper, zinc and lead contaminated field trial in Shanghai, China.

A phytoremediation approach using willow microcuttings was tested on a large experimental site spiked with Cu, Pb and Zn. The objective was to verify if this approach allows plant establishment and effective extraction of contaminants. The experimental design consisted of four blocks divided into three plots, in which treatments (salts of the three metals) were randomly applied. Each plot was also subdivided to verify the effect of adding diverse compost treatments: no compost, vegetable garden waste compost (Compost 1), food waste compost (Compost 2) and a mix of Composts 1 and 2. Willow microcuttings (Salix matsudana × alba) were scattered on the plots at a density of 60 m-2. Nine months after the implementation, the number of stems developed, yield and concentration of metals in the aerial parts of the willows were measured. The presence of a contaminant did not affect the number of stems developed. However, the presence of Compost 1 had a significant effect on the number of stems produced as well as on the biomass. Among the three metals, Zn was the element found in highest concentration in willow tissues. An estimated minimum 300 g of Zn per hectare per year could be removed using this method.

Biomass and phytoextraction potential of three ornamental shrub species tested over three years on a large-scale experimental site in Shanghai, China.

Issues related to environmental degradation are of increasing concern worldwide. In urban Shanghai, many plant species used for ornamental purposes grow under harsh conditions yet show good resistance to pollution. Twelve shrub species were tested in a previous study to evaluate their capacity to tolerate and absorb inorganic contaminants. Among these, Hibiscus mutabilis and H. hamabo and Senna corymbosa, presented good performance and were tested over three growing seasons in a large experimental design (2000 m2) where the soil was spiked with salts of Cu, Pb, or Zn. Each year of the study, all plants were cut and biomass was harvested and analyzed. Despite the relatively high concentration of metals in plots, no signs of toxicity were observed. Concentrations of metals in root tissues were generally much higher than those found in aerial parts. The bioconcentration factor values were generally very low, but the high biomass yield produced by H. mutabilis led to significant removal of Cu and Zn. No difference in the quantity of Pb extracted was found between species. As these plants respond well to coppicing, it may be possible to gradually eliminate contaminants from soils. Their use can also embellish the landscape while generating many other ecological services.

The Response of a 16S Ribosomal RNA Gene Fragment Amplified Community to Lead, Zinc, and Copper Pollution in a Shanghai Field Trial.

Industrial and agricultural activities have caused extensive metal contamination of land throughout China and across the globe. The pervasive nature of metal pollution can be harmful to human health and can potentially cause substantial negative impact to the biosphere. To investigate the impact of anthropogenic metal pollution found in high concentrations in industrial, agricultural, and urban environments, 16S ribosomal RNA gene amplicon sequencing was used to track change in the amplified microbial community after metal contamination in a large-scale field experiment in Shanghai. A total of 1,566 operational taxonomic units (OTUs) identified from 448,108 sequences gathered from 20 plots treated as controls or with lead, zinc, copper, or all three metals. Constrained Analysis of Principal Coordinates ordination did not separate control and lead treatment but could separate control/lead, zinc, copper, and three metal treatment. DESeq2 was applied to identify 93 significantly differentially abundant OTUs varying in 211 pairwise instances between the treatments. Differentially abundant OTUs representing genera or species belonging to the phyla Chloroflexi, Cyanobacteria, Firmicutes, Latescibacteria, and Planctomycetes were almost universally reduced in abundance due to zinc, copper, or three metal treatment; with three metal treatment abolishing the detection of some OTUs, such as Leptolyngbya, Desmonostoc muscorum, and Microcoleus steenstrupii. The greatest increases due to metal treatment were observed in Bacteroidetes, Actinobacteria, Chlamydiae, Nitrospirae, and Proteobacteria (α, ß, δ, and γ); the most (relative) abundant being uncharacterized species within the genera Methylobacillus, Solirubrobacter, and Ohtaekwangia. Three metal treatment alone resulted in identification of 22 OTUs (genera or species) which were not detected in control soil, notably including Yonghaparkia alkaliphila, Pedobacter steynii, Pseudolabrys taiwanensis, Methylophilus methylotrophus, Nitrosospira, and Lysobacter mobilis. The capacity to track alterations of an amplified microbial community at high taxonomic resolution using modern bioinformatic approaches, as well as identifying where that resolution is lost for technical or biological reasons, provides an insight into the complexity of the microbial world resisting anthropogenic pollution. While functional assessment of uncharacterized organisms within environmental samples is technically challenging, an important step is observing those organisms able to tolerate extreme stress and to recognize the extent to which important amplifiable community members still require characterization.

Plant growth and nutrient uptake in treatment wetlands for water with low pollutant concentration.

The objective of this study was to determine how macrophytes commonly used in treatment wetlands (TWs) respond to water with low pollutant concentration. We measured pollutant removal efficiency and compared growth and nutrient uptake of five macrophytes in demonstration scale units (volume >40 m3) irrigated by water with pollutant concentrations representative of average urban stormwater quality. All species showed a strong productivity gradient along the beds, starting with high biomass - high density near the inlet, then decreasing progressively with distance. Cyperus was by far the most productive species. Phragmites and Thalia had higher biomass in the first few metres of the beds than Typha and Arundo. In terms of pollutant removal, decreasing plant growth may be interpreted as indicative of high efficiency when caused by nutrient depletion. Differences in aboveground biomass between species did not translate into measurable differences in removal efficiency at the outlet. Although Phragmites australis is the species most commonly used in TWs, under the low nutrient load, Cyperus had twice its biomass, and higher N and P uptake. These results highlight the importance of considering wastewater characteristics when selecting macrophyte species for TWs.