[Integrated Assessment of Runoff Quality from Green Roofs with Different Configurations].

Green roofs are regarded as one of the important measures for the sponge city construction. However, the comprehensive impacts of configuration factors (e.g., vegetation and substrates) on runoff quality from green roofs are not clear, which limits the promotion of green roofs. In this study, 12 green roofs with three vegetation types (i.e., Sedum lineare, Portulaca grandiflora, and non-vegetated substrates), three substrate types (i.e., local planting soil, engineered soil, and light growing medium), and two substrate depths (i.e., 10 cm and 15 cm) were set up in Beijing. During the rainy season of 2019, the rainfall characteristics, runoff volumes, and concentrations of nutrients and heavy metals of runoff from the green roofs were monitored. Based on the measured data, a runoff quality index (RQI) was developed to evaluate the comprehensive influences of configurations on runoff quality of the green roofs. The results showed that vegetation could improve runoff reduction rate and decrease the concentrations of NO3--N in runoff of green roofs. The RQIs of green roofs planted with S. linear and P. grandiflora were similar, and the evaluation results of runoff quality were better than those with non-vegetated substrates. The materials of substrates had significant influences on the runoff reduction rate and pollutant concentrations in runoff from green roofs. The green roofs with light growing medium, which had the lowest runoff reduction rates and the highest concentrations of NH4+-N, DFe, DMn, and DZn in the runoff, showed poorer runoff quality than the green roofs with local planting soil and engineered soil. The green roofs with a substrate depth of 15 cm had higher runoff reduction rates than those with 10 cm deep substrate, and the runoff quality was better than those with a substrate depth of 10 cm. The results of this study provide scientific reference for the design and integrated assessment of green roofs.

Phytoremediation of Cd-contaminated farmland soil via various Sedum alfredii-oilseed rape cropping systems: Efficiency comparison and cost-benefit analysis.

Phytoremediation is a green technology for heavy metal removal from contaminated soil, and its remediation efficiency and economic feasibility in field trial should be evaluated before large-scale application. However, there is still lacking relevant analysis, especially for phytoremediation with different cropping patterns. In the present study, we performed phytoremediation on slightly Cd-contaminated farmland soil via three cropping systems, i.e. Sedum alfredii monoculture, oilseed rape monoculture, and S. alfredii-oilseed rape intercropping. Dry weights of S. alfredii and oilseed rape were both enhanced under intercropping pattern, while the highest total Cd extraction amount (148 g ha-1) were observed under S. alfredii monoculture. Furtherly, a cost-benefit analysis via Monta Carlo simulation in a ten-year lifetime was conducted. The benefits of S. alfredii monoculture and intercropping schemes would offset the total costs in 6 and 8 years, respectively. S. alfredii monoculture achieved a higher net present value of 1.88 × 104 US$ as compared with intercropping (9.53 × 103 US$). These results indicate that S. alfredii monoculture scheme could be a promising phytoremediation strategy for slightly Cd-contaminated soil owing to better remediation efficiency and economic feasibility. Moreover, the enhancement in mechanization level and the reduction of seedling cost could further improve its economic viability.

Comparison of ashing and pyrolysis treatment on cadmium/zinc hyperaccumulator plant: Effects on bioavailability and metal speciation in solid residues and risk assessment.

Phytoremediation of metal(loid)s contaminated sites is widely used, while there is scarce of investigation on the metal-enriched biomass waste safely disposal which resulted in risks of causing secondary pollution to the soil and water bodies and even to human health. Thus, this study compared the effects of ashing and pyrolysis treatments on cadmium (Cd) and zinc (Zn) hyperaccumulation plant Sedum plumbizincicola. Chemical speciation, the Toxicity Characteristic Leaching Procedure (TCLP), and diethylenetriamine pentaacetic acid (DTPA) extraction were employed to characterize the bioavailability and leachability of Cd and Zn in the solid residues after pyrolysis and ashing. The risk assessment code (RAC) and potential ecological risk index (RI) were subsequently used to evaluate the risk of the solid residues to the environment. The results showed that both ashing and pyrolysis treatments could transform the bioavailable Cd and Zn in S. plumbizincicola into a more stable form, and the higher the temperature the greater the stablility. Pyrolysis converted a maximum of 80.0% of Cd and 70.3% of Zn in S. plumbizincicola to the oxidisable and residual fractions, compared with ashing which achieved only a ∼42% reduction. The pyrolysis process minimised the risk level of Cd and Zn to the environment based on the RAC and RI assessments. The results of the TCLP test, and DTPA extraction confirmed that the leaching rate and the bioavailable portion of Cd and Zn in the biochars produced by pyrolysis were invariably significantly (p < 0.05) lower than the solid residues produced by ashing, and reached the lowest at 650 °C. In other words, pyrolysis was better than ashing for thermal treatment of the metal-enriched hyperaccumulator plant, in view of minimising the bioavailability and leachability of Cd and Zn from the solid residues to the environment. This study provides fundamental data on the choice of treatments for the disposal of metal-enriched plant biomass.

Transformation behaviors and environmental risk assessment of heavy metals during resource recovery from Sedum plumbizincicola via hydrothermal liquefaction.

Environmentally sound disposal of hyperaccumulator harvests is of critical importance to industrialization of phytoremediation. Herein, transformation behaviors and environmental risk of heavy metals were comprehensively examined during subcritical hydrothermal liquefaction of Sedum plumbizincicola. It is concluded that low temperature liquefaction favored resource recovery of heavy oil and hydrochars in terms of higher energy density, improved carbon sequestration and less energy consumption. Heavy metals were mainly distributed into hydrochars and water soluble phase with less than 10% in heavy oil. All metal elements except As could be accumulated in hydrochars by extending reaction time, whereas more than 96% of As was redistributed into water soluble phase. Prolonged liquefaction time facilitated immobilization of Cd, Cr and As in hydrochars, but fast liquefaction favored Pb stabilization. Liquefaction significantly reduced environmental risk level of Cd, Zn and As, but may mobilize Pb and Mn, especially for Mn to very high risk level at 240 ºC. High temperature with long reaction time tended to inhibit leaching rate of Mn, whereas low liquefaction temperature with short reaction time prevented the leaching of Zn and As from hydrochars. Overall, these findings are essential for downstream upgrading of heavy oil and metals recovery from hydrochars.

The effects and health risk assessment of cauliflower co-cropping with Sedum alfredii in cadmium contaminated vegetable field.

Phytoremediation coupled with co-cropping is assumed to be good for safety utilization and remediation of heavy metal contaminated farmland, which can ensure farmers' income without increasing health risks for human. In this study, the effects on plant cadmium (Cd) accumulation and health risk of consuming the vegetable plant were compared between monoculture and co-cropping of cauliflower (Brassica oleracea) with two ecotypes of Sedum alfredii in a moderately (0.82 mg kg-1) Cd contaminated greenhouse vegetable field. The results showed that co-cropping with S. alfredii raised Cd concentration in edible part of cauliflower with slightly growth promotion. The health risk of consuming cauliflower to different groups of people have been evaluated by calculating Hazard Quotient (HQ) and all HQ value were less than 1.0, which indicated that eating co-cropped cauliflower would not cause health risks to adults and children. Besides, the Cd concentration of hyperaccumulating ecotype (HE) of S. alfredii was 27.3 mg kg-1 in monoculture and it increased to 51.2 mg kg-1 after co-cropping with cauliflower, suggesting that the co-cropping system promoted HE Cd absorption capacity. Therefore, the "Phytoextraction Coupled with Agro-safe-production" (PCA) model of cauliflower and HE can serve as an alternative sustainable strategy in the Cd moderate polluted greenhouse.

Cadmium accumulation in winter crops and the assessment of paddy soil phytoremediation in southern China.

Heavy metal pollution, in particular with cadmium (Cd), threatens both the environment and human health. The phytoremediation of contaminated soil is one recently developed eco-friendly technique that can be applied to mitigate this issue. Repairing Cd-contaminated paddy soil during the fallow winter period can ensure future rice production while reducing heavy metal pollution. Seven winter crops were planted in this study to investigate the accumulation of this metal in mid-level Cd and low-level lead (Pb) and zinc (Zn)-contaminated paddy soils. Results show that after 4 or 5 months of growth, all crops had become moderately tolerant to toxicity; indeed, shoot Cd bioconcentration factor (BCF) values were 37.4, 17.0, 11.5, 10.5, 5.8, 3.9, and 1.4 for Sedum alfredii (SA), Witloof chicory (WC), edible-leaf beet (EB), Cardamine hupingshanensis (CH), leafy mustard (LM), oil mustard (OM), and perennial ryegrass (PR), respectively, while shoot Pb and Zn BCF values were less than 1 and 5, respectively. And SA, WC, EB, and CH all had higher shoot Cd accumulation capacities, especially SA in which the level reached 53.9 mg kg-1. The calculation results of restoration potential show that it will take at least 5 years for WC, 7 years for SA and EB, and 10 years for CH to reach the repair target. These results show that it is possible to grow winter crops to repair soil Cd pollution, with WC, EB, CH, and SA, the best candidates for making full use of fallow periods while simultaneously achieving soil phytoremediation. The results of this study will prove useful for establishing a new summer production model by ensuring the winter repair of contaminated paddy soil.

Comparison of Antioxidant Capability after Isopropanol Salting-Out Pretreatment and n-Butanol Partition Extraction, and Identification and Evaluation of Antioxidants of Sedum formosanum N.E.Br.

Crude extracts of Sedum formosanum N.E.Br. obtained from n-butanol partition (BP) and isopropanol salting-out pretreatment (ISP) were analyzed using antioxidation assays. The results indicated that the extract from ISP contained more potent antioxidants and thus exhibited more antioxidant activity in all the assays. The superoxide radical-scavenging activity and inhibition of nitric oxide radicals achieved after ISP were 3.65 and 2.18 times higher than those achieved through BP, respectively. Eight bioactive natural products were isolated and identified according to an analysis of antioxidation activity in different fractions of the ISP crude extract, namely three cyanophoric glycosides 1-3, three flavonoids 4-6 and two phenolic compounds (7 and a new compound 8). Among them, compounds 5 and 6 exhibit the highest antioxidation capability, and the ISP is suitable for obtaining compounds 5 and 6 using HPLC chromatograms. Therefore, ISP is an excellent extraction technology that can be used to extract antioxidant compounds in the nutraceutical and pharmaceutical industries.

Green roof systems: a study of public attitudes and preferences in southern Spain.

This study investigates people's preconceptions of green roofs and their visual preference for different green roof design alternatives in relation to behavioral, social and demographical variables. The investigation was performed as a visual preference study using digital images created to represent eight different alternatives: gravel roof, extensive green roof with Sedums not in flower, extensive green roof with sedums in bloom, semi-intensive green roof with sedums and ornamental grasses, semi-intensive green roof with shrubs, intensive green roof planted with a lawn, intensive green roof with succulent and trees and intensive green roof with shrubs and trees. Using a Likert-type scale, 450 respondents were asked to indicate their preference for each digital image. Results indicated that respondents' sociodemographic characteristics and childhood environmental background influenced their preferences toward different green roof types. Results also showed that green roofs with a more careful design, greater variety of vegetation structure, and more variety of colors were preferred over alternatives.

Phytoextraction of heavy metals from contaminated soil by co-cropping with chelator application and assessment of associated leaching risk.

Phytoextraction using hyperaccumulating plants is generally time-consuming and requires the cessation of agriculture. We coupled chelators and a co-cropping system to enhance phytoextraction rates, while allowing for agricultural production. An experiment on I m3 lysimeter beds was conducted with a co-cropping system consisting of the hyperaccumulator Sedum alfredii and low-accumulating corn (Zea Mays, cv. Huidan-4), with addition ofa mixture of chelators (MC), to assess the efficiency of chelator enhanced co-crop phytoextraction and the leaching risk caused by the chelator. The results showed that the addition of MC promoted the growth of S. alfredii in the first crop (spring-summer season) and significantly increased the metal phytoextraction. The DTPA-extractable and total metal concentrations in the topsoil were also reduced more significantly with the addition of MC compared with the control treatments. However, mono-cropped S. alfredii without MC was more suitable for maximizing S. alfredii growth and therefore phytoextraction of Zn and Cd during the autumn-winter seasons. No adverse impact to groundwater due to MC application was observed during the experiments with three crops and three MC applications. But elevated total Cd and Pb concentrations among subsoils compared to the initial subsoil concentrations were found for the co-crop + MC treatment after the third crop.