Trace elements in the Upper Indus River Basin (UIRB) of Western Himalayas: Quantification, sources modeling, and impacts.

This study conducted a comprehensive analysis of trace element concentrations in the Upper Indus River Basin (UIRB), a glacier-fed region in the Western Himalayas (WH), aiming to discern their environmental and anthropogenic sources and implications. Despite limited prior data, 69 samples were collected in 2019 from diverse sources within the UIRB, including mainstream, tributaries, and groundwater, to assess trace element concentrations. Enrichment factor (EF) results and comparisons with regional and global averages suggest that rising levels of Zn, Cd, and As may pose safety concerns for drinking water quality. Advanced multivariate statistical techniques such as principal component analysis (PCA), absolute principal component scores (APCS-MLR), Monte Carlo simulation (MCS), etc were applied to estimate the associated human health hazards and also identified key sources of trace elements. The 95th percentile of the MCS results indicates that the estimated total cancer risk for children is significantly greater than (>1000 times) the USEPA's acceptable risk threshold of 1.0 × 10-6. The results classified most of the trace elements into two distinct groups: Group A (Li, Rb, Sr, U, Cs, V, Ni, TI, Sb, Mo, Ge), linked to geogenic sources, showed lower concentrations in the lower-middle river reaches, including tributaries and downstream regions. Group B (Pb, Nb, Cr, Zn, Be, Al, Th, Ga, Cu, Co), influenced by both geogenic and anthropogenic activities, exhibited higher concentrations near urban centers and midstream areas, aligning with increased municipal waste and agricultural activities. Furthermore, APCS-MLR source apportionment indicated that trace elements originated from natural geogenic processes, including rock-water interactions and mineral dissolution, as well as anthropogenic activities. These findings underscore the need for targeted measures to mitigate anthropogenic impacts and safeguard water resources for communities along the IRB and WH.

Deciphering dissolved organic matter characteristics and its fate in a glacier-fed desert river-the Tarim river, China.

The bioavailable diverse dissolved organic matter (DOM) present in glacial meltwater significantly contributes to downstream carbon cycling in mountainous regions. However, the comprehension of molecular-level characteristics of riverine DOM, from tributary to downstream and their fate in glacier-fed desert rivers remains limited. Herein, we employed spectroscopic and high-resolution mass spectrometry techniques to study both optical and molecular-level characteristics of DOM in the Tarim River catchment, northwest China. The results revealed that the DOC values in the downstream were higher than those in the tributaries, yet they remained comparable to those found in other glacier-fed streams worldwide. Five distinct components were identified using EEM-PARAFAC analysis in both tributary and downstream samples. The dominance of three protein-like components in tributary samples, contrasting with a higher presence of humic-like components in downstream samples, which implied that the dilution and alterations of the glacier DOM signature and overprinting with terrestrial-derived DOM. Molecular composition revealed that thousands of compounds with higher molecular weight and increased aromaticity were transformed, generated and introduced from terrestrial inputs during downstream transportation. The twofold rise in polycyclic aromatic and polyphenolic compounds observed downstream compared to tributaries indicated a greater influx of terrestrial organic matter introduced into the downstream during water transportation. The study suggests that the glacier-sourced DOM experienced minimal photodegradations, with limited influence from human activities, while also being shaped by terrestrial inputs during its transit in the alpine-arid region. This unique scenario offers valuable insights into comprehending the fate of DOM originating from glacial meltwater in arid mountainous regions.

Agricultural ditches are hotspots of greenhouse gas emissions controlled by nutrient input.

Agricultural ditches are pervasive in agricultural areas and are potential greenhouse gas (GHG) hotspots, since they directly receive abundant nutrients from neighboring farmlands. However, few studies measure GHG concentrations or fluxes in this particular water course, likely resulting in underestimations of GHG emissions from agricultural regions. Here we conducted a one-year field study to investigate the GHG concentrations and fluxes from typical agricultural ditch systems, which included four different types of ditches in an irrigation district located in the North China Plain. The results showed that almost all the ditches were large GHG sources. The mean fluxes were 333 µmol m-2 h-1 for CH4, 7.1 mmol m-2 h-1 for CO2, and 2.4 µmol m-2 h-1 for N2O, which were approximately 12, 5, and 2 times higher, respectively, than that in the river connecting to the ditch systems. Nutrient input was the primary driver stimulating GHG production and emissions, resulting in GHG concentrations and fluxes increasing from the river to ditches adjacent to farmlands, which potentially received more nutrients. Nevertheless, the ditches directly connected to farmlands showed lower GHG concentrations and fluxes compared to the ditches adjacent to farmlands, possibly due to seasonal dryness and occasional drainage. All the ditches covered approximately 3.3% of the 312 km2 farmland area in the study district, and the total GHG emission from the ditches in this area was estimated to be 26.6 Gg CO2-eq yr-1, with 17.5 Gg CO2, 0.27 Gg CH4, and 0.006 Gg N2O emitted annually. Overall, this study demonstrated that agricultural ditches were hotspots of GHG emissions, and future GHG estimations should incorporate this ubiquitous but underrepresented water course.

[Mechanisms of moxibustion preconditioning underlying improving learning-memory ability by regulating polarization of microglia via TLR4/NF-κB signaling pathway in AD rats].

OBJECTIVE: To observe the effect of moxibustion preconditioning on learning-memory ability, Toll like receptor 4(TLR4)/nuclear factor-kappa B(NF-κB) signal pathway related proteins and microglia in rats with Alzheimer's disease (AD), so as to explore its possible mechanisms underlying improvement of AD. METHODS: Male SD rats were randomly divided into normal, sham operation, AD model and pre-moxibustion groups, with 9 rats in each group. Moxibustion was applied to "Baihui"(GV20), "Shenshu"(BL23) and "Zusanli"(ST36) for 15 min, once daily, 6 days as a course of treatment for 3 courses. At the end of moxibustion, the AD model was established by injection of Aß25-35 aggregation solution into the bilateral hippocampus. The sham operation group was only injected with the same amount of 0.9% Nacl solution. The spatial learning-memory ability of rats was detected by Morris water maze test, the ultrastructure of hippocampal neurons was observed by transmission electron microscope (TEM). The histopathological changes of hippocampus tissue were observed by HE staining, and the protein expression levels of TLR4 and NF-κB p65 in the hippocampus detected by Western blot, and the positive expressions of Iba-1, CD80 and CD206 in the hippocampal CA1 region were detected by immunofluorescence labeling. The contents of inflammatory factors IL-1ß, TNF-α and IL-10 in the hippocampus were measured by ELISA. RESULTS: Compared with the sham operation group, the escape latency was significantly increased (P<0.01), and the number of platform quadrant crossing times was decreased (P<0.01) in the model group. In comparison with the model group, the increased escape latency and the decreased platform quadrant crossing times were reversed in the pre-moxibustion group (P<0.01). TEM and light microscope observation showed loose arrangement of cells, enlarged cell space, degeneration, swelling and deformation of hippocampal neurons, rupture of membranes of a large number of cells, reduction of mitochondria, dilation of endoplasmic reticulum, and matrix vacuoles, uneven distribution of organelles and cytoplasm, and being difficult in distinguishing the nuclear cytoplasm in the model group, which was relatively milder in the pre-moxibustion group. The expression levels of hippocampal NF-κB p65 and TLR4, the mean immunofluorescence density of Iba-1 and CD80, as well as the contents of IL-1ß and TNF-α in hippocampal CA1 region were significantly increased in the model group than those in the sham operation group (P<0.01), and obviously decreased in the pre-moxibustion group than those in the model group (P<0.05, P<0.01). Whereas the expression of CD206 and the content of IL-10 were evidently decreased in the model group than those in the sham operation group (P<0.01), and strikingly increased in the pre-moxibustion group than those in the model group (P<0.01). No significant differences were found between the sham operation group and the normal group in all the indexes mention above (P>0.05). CONCLUSION: Pre-moxibustion at GV20, BL23 and ST36 can improve learning-memory ability in AD rats, which may be associated with its functions in promoting the polarization of microglia from M1 to M2 and reducing the neuroinflammatory response by way of TLR4/NF-κB signaling pathway.

[Involvement of miR-126-3p via mTOR/HIF-1α signaling pathway in effect of electroacupuncture on angiogenesis in rats with cerebral ischemia].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on miRNA-126-3p and mammalian target of rapamycin (mTOR)/hypoxia-inducible factor-1α (HIF-1α) signaling pathway in rats with cerebral ischemia (CI), so as to explore the underlying mechanism of EA on angiogenesis. METHODS: Male SD rats were randomly divided into control group, model group, EA group and EA+inhibitor group (inhibitor group), which were further divided into 3, 7 and 14 d subgroups, with 12 rats in each sub-group. The CI model was established by occlusion of the middle cerebral artery. EA (2 Hz/20 Hz, 0.5 mA) was applied to "Dazhui" (GV14), "Baihui" (GV20) for 20 min, once daily for 14 days at most. Rats of the inhibitor group were given an intraperitoneally injection of mTOR inhibitor (0.1 mg/mL, 0.3 mg/kg) before daily EA. The neurological function was evaluated by modified neurological severity score (mNSS). The ultrastructure of cortical neurons and microvascular endothelial cells in ischemic penumbra was observed by transmission electron microscope, and the microvessel density (MVD) of cortical endothelium in ischemic penumbra was detected by immunohistochemistry. Western blot and quantitative real-time PCR were used to detect the protein and mRNA expression of mTOR, HIF-1α and the expression of miR-126-3p in the cortex of ischemic penumbra, respectively. RESULTS: After modeling, compared with the control group at the same time point, the mNSS of the model group was increased (P<0.01), and decreased over time (P<0.01). The cortical neurons and brain microvascular endothelial cells in the ischemic penumbra were edema, and the cell structure was damaged obviously in the model group.The MVD value and the expressions of mTOR、HIF-1α proteins and mRNAs were increased (P<0.01), while the expression of miR-126-3p decreased (P<0.01) in the model group relative to the control group. Compared with the model group at the same time point, the mNSS of both intervention groups was significantly reduced (P<0.01, P<0.05), the neuron and cerebral microvascular structure improved to varying degrees, and the MVD value, the expressions of mTOR and HIF-1α protein and mRNA, and the expression of miR-126-3p of the two treatment groups were increased (P<0.01, P<0.05) at all time points (excep MVD at day 7 in the inhibitor group). Compared with the EA group at the same time point, MVD, the expressions of mTOR, HIF-1α proteins and mRNAs and miR-126-3p in the inhibitor group were all decreased (P<0.05,P<0.01). Compared with the group itself at 4 hours after modeling and day 3 and day 7, the mNSS was decreased at day 14 （P<0.01） in the model, EA and inhibitor groups. Compared with the group itself at day 3, the MVD value and the expression of mTOR protein were increased at day 7 and day 14 in the model, EA and inhibitor groups (P<0.01, P<0.05). Compared with the group itself at day 3 and day 7, the expression of mTOR mRNA and miR-126-3p were up-regulated at day 14 in the model and EA groups (P<0.01, P<0.05).Compared with the group itself at day 3, the mRNA expressions of mTOR and HIF-1α were increased at day 7 and day 14 (P<0.01, P<0.05) in the inhibitor group. CONCLUSION: EA at GV14 and GV20 can alleviate neurological deficit and improve angiogenesis in rats with CI, which may be related with its effect in up-regulating the expression of mTOR and HIF-1α, improving activation of miR-126-3p in the cortex of ischemic penumbra.

[Repair impact of vibration exercise with different frequencies on articular cartilage of rats with early knee osteoarthritis and its JNK/NF-κB, SOX9 mechanisms].

Objective: To investigate the repair effect and JNK/NF-κB,SOX9 mechanisms of vibration exercise with different frequencies on articular cartilage in rats with early knee osteoarthritis. Methods: Forty-eight adult male SD rats were randomly divided into six groups(n=8):model control group(MC),high frequency vibration group 1 (GP1,60 Hz),high frequency vibration 2 group (GP2,40 Hz),medium frequency vibration group (ZP,20 Hz),minor frequency group(DP,10 Hz)and normal control group(NC). Except for NC group,the rats in each group were made into early knee osteoarthritis model after six weeks of knee joint cavity injection of papain solution and 2% mixture l-cysteine on the 1st,4 th and 7th day. Each exercise group was subjected vibration to 40 minutes a day with amplitude of 2～5 mm and 5 days a week. Four weeks later, the articular cartilage of the lateral femoral condyle of the both back leg knee joints were detected by HE staining,serine O staining and Mankin scores for morphological observation. The expression levels of JNK,NF-κB p65 and Sox9 mRNA in articular cartilage of the medial femoral condyle were detected by RT-qPCR,and the protein expressions of JNK,NF-κB p65 and Sox9 were detected by Western blot. Results: Compared with the NC group,the Mankin score in other groups was significantly higher (P＜0.01). Compared with the MC group,the Mankin score of each vibration group was significantly lower(P＜0.05),the mRNA and protein expressions of JNK and NF-κB p65 in each vibration training group were significantly lower (P＜0.01),the expressions of Sox9 mRNA and protein in vibration training group were increased significantly (P＜0.01). Compared with the higher frequency group,the Mankin score,the mRNA and protein expressions of JNK and NF-κB p65 of lower frequency group were significantly lower (P＜0.05 or P＜0.01). But the expressions of Sox9 mRNA and protein were significantly higher (P＜ 0.05 or P＜0.01). Conclusion: Vibration exercise of different frequencies may present varying degrees of cartilage repair impact in rats with early knee osteoarthritis,and the cartilage repair by low-frequency vibration training is better than that by high-frequency vibration. This can be one of the mechanisms on controlling collagen synthesis by down-regulating JNK/NF-κB expression and increasing SOX9 activity of OA articular cartilage.

Quadrupole detection FT-ICR mass spectrometry offers deep profiling of residue oil: A systematic comparison of 2ω 7 Tesla versus 15 Tesla instruments.

Mass resolving power is one of the key features of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), which enables the molecular characterization of complex mixtures. Quadrupole (2ω) detection provides a significant step forward in FT-ICR MS performance, as it doubles the resolving power for a given signal acquisition time. Whether this 2ω detection technique truly substitutes for a higher magnetic field remains unknown however. In this study, a residue oil sample was characterized using both a 2ω 7 Tesla FT-ICR and a 15 Tesla FT-ICR instrument, and analytical figures of merit were systematically compared. It was shown that 2ω 7T FT-ICR MS provided comparable performance in the deep profiling of the complex oil sample, with better signal intensities and reproducibilities for absorption-mode processing. The 15T FT-ICR MS gave more precise measurements with better estimates of the sample's elemental compositions. To the best of our knowledge, this is the first published study, which thoroughly compared the performance of 2ω detection on a low magnetic field instrument with that of a high magnetic field FT-ICR-MS.

Genomic basis for RNA alterations in cancer.

Transcript alterations often result from somatic changes in cancer genomes1. Various forms of RNA alterations have been described in cancer, including overexpression2, altered splicing3 and gene fusions4; however, it is difficult to attribute these to underlying genomic changes owing to heterogeneity among patients and tumour types, and the relatively small cohorts of patients for whom samples have been analysed by both transcriptome and whole-genome sequencing. Here we present, to our knowledge, the most comprehensive catalogue of cancer-associated gene alterations to date, obtained by characterizing tumour transcriptomes from 1,188 donors of the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA)5. Using matched whole-genome sequencing data, we associated several categories of RNA alterations with germline and somatic DNA alterations, and identified probable genetic mechanisms. Somatic copy-number alterations were the major drivers of variations in total gene and allele-specific expression. We identified 649 associations of somatic single-nucleotide variants with gene expression in cis, of which 68.4% involved associations with flanking non-coding regions of the gene. We found 1,900 splicing alterations associated with somatic mutations, including the formation of exons within introns in proximity to Alu elements. In addition, 82% of gene fusions were associated with structural variants, including 75 of a new class, termed 'bridged' fusions, in which a third genomic location bridges two genes. We observed transcriptomic alteration signatures that differ between cancer types and have associations with variations in DNA mutational signatures. This compendium of RNA alterations in the genomic context provides a rich resource for identifying genes and mechanisms that are functionally implicated in cancer.

Whole-genome sequencing reveals distinct genetic bases for insulinomas and non-functional pancreatic neuroendocrine tumours: leading to a new classification system.

OBJECTIVE: Insulinomas and non-functional pancreatic neuroendocrine tumours (NF-PanNETs) have distinctive clinical presentations but share similar pathological features. Their genetic bases have not been comprehensively compared. Herein, we used whole-genome/whole-exome sequencing (WGS/WES) to identify genetic differences between insulinomas and NF-PanNETs. DESIGN: The mutational profiles and copy-number variation (CNV) patterns of 211 PanNETs, including 84 insulinomas and 127 NF-PanNETs, were obtained from WGS/WES data provided by Peking Union Medical College Hospital and the International Cancer Genome Consortium. Insulinoma RNA sequencing and immunohistochemistry data were assayed. RESULTS: PanNETs were categorised based on CNV patterns: amplification, copy neutral and deletion. Insulinomas had CNV amplifications and copy neutral and lacked CNV deletions. CNV-neutral insulinomas exhibited an elevated rate of YY1 mutations. In contrast, NF-PanNETs had all three CNV patterns, and NF-PanNETs with CNV deletions had a high rate of loss-of-function mutations of tumour suppressor genes. NF-PanNETs with CNV alterations (amplification and deletion) had an elevated risk of relapse, and additional DAXX/ATRX mutations could predict an increased relapse risk in the first 2-year period. CONCLUSION: These WGS/WES data allowed a comprehensive assessment of genetic differences between insulinomas and NF-PanNETs, reclassifying these tumours into novel molecular subtypes. We also proposed a novel relapse risk stratification system using CNV patterns and DAXX/ATRX mutations.

[Electroacupuncture combined with rehabilitation training improves regional cerebral blood flow and reduces infarct volume by promoting expression of angiogenesis-related factors in acute cerebral ischemia rats].

OBJECTIVE: To observe the effect of electroacupuncture (EA) combined with rehabilitation training on regional cerebral blood flow (rCBF) and angiogenesis in rats with acute cerebral ischemia (ACI), so as to explore its mechanisms underlying improvement of ACI. METHODS: A total of 135 male SD rats were divided into 5 groups: sham-operation (sham), model, EA, rehabilitation training and EA+rehabilitation training (combined treatment) groups (n=27 rats in each group). The ACI model was established by occlusion of the middle cerebral artery with thread embolus. EA (2 Hz/20 Hz, 3-5 V) was applied to "Baihui" (GV20), "Shuigou" (GV26) and bilateral "Neiguan" (PC6) for 20 min, once daily for 14 days. The rehabilitation training including hair-brushing in an enriched environment (10 min), round wooden-stick turning (10 min), grid-board climbing (10 min), and treadmill running (30 min/d) was condacted once daily for 14 days. The rCBF was measured by Doppler ultrasound. The cerebral infarct volume (CIV) was measured after 2, 3, 5-triphenyltetrazolium chloride (TTC) staining. The expression of CD34+ in the ischemic penumbra region of brain tissue was detected by immunohistochemistry, and the expressions of angiogenesis-related factors as vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor 2 (VEGFR2) and basic fibroblast growth factor (bFGF) proteins in the ischemic brain tissue were detected by Western blot. RESULTS: Following modeling, the rCBF levels at the 5 min, 3rd, 7th and 14th day were significantly decreased in the model group relevant to the sham group (P<0.01). After the intervention, the rCBF levels were significantly increased on day 3, 7 and 14 in the combined treatment group and on day 7 and 14 in both the EA and rehabilitation training groups in comparison with the model group (P<0.01). The CIV was obvious in the model group in comparison with the sham group (P<0.01), but was markedly smaller in the EA, rehabilitation training and combined treatment groups on day 3,7 and 14 than in the model group (P<0.01). The number of CD34+ positive cells, and the expression levels of VEGF, VEGFR2, and bFGF proteins in ischemic brain tissues were significantly higher on day 3, 7 and 14 in the model group than in the sham group (P<0.01, P<0.05), and were further up-regulated considerably at the 3 time-points in the 3 treatment groups (P<0.01, P<0.05). The therapeutic effect of EA+rehabilitation training was significantly superior to that of simple EA and simple rehabilitation training in up-regulating rCBF, CD34+ positive cell number, and expression levels of VEGF, VEGFR2 and bFGF, and in down-regulating the CIV on day 3,7 and 14 (P<0.05, P<0.01). No significant differences were found between the EA and rehabilitation groups in the above-mentioned 6 indexes (P>0.05). CONCLUSION: EA combined with rehabilitation training can reduce the infarct volume and increase rCBF in ACI rats, which is probably associated with its effects in promoting the expression of angiogenesis-related factors of ischemic brain tissues. The effect of EA combined with rehabilitation training is markedly better than that of EA and rehabilitation training alone.

Stable isotope fractionation during uptake and translocation of cadmium by tolerant Ricinus communis and hyperaccumulator Solanum nigrum as influenced by EDTA.

The isotopic fractionation could contribute to understanding the Cd accumulation mechanisms in plant species. However, there are few of systematical investigations with regards to the Cd isotope fractionation in hyperaccumulator plants. The Cd tolerant Ricinus communis and hyperaccumulator Solanum nigrum were cultivated in nutrient solutions with varying Cd and EDTA concentrations. Cd isotope ratios were determined in the solution, root, stem and leaf. The two investigated plants were systematically enriched in light isotopes relative to their solutions (Δ114/110Cdplant-solution = -0.64‰ to -0.29‰ for R. communis and -0.84‰ to -0.31‰ for S. nigrum). Cd isotopes were markedly fractionated among the plant tissues. For both plant species, an enrichment in light Cd isotopes from solution to root was noted, followed by a slight depletion in light Cd isotopes from root to shoot. Noticeably, the chelation process has caused lighter Cd isotope enrichment in the root of R. communis and S. nigrum. Further, the good fits between △114/110Cdroot-plant and ln Froot (or between △114/110Cdshoot-plant and ln Fshoot) indicate that Cd isotopic signatures can be used to study Cd transportation during the metabolic process of plants. This study suggests that knowledge of the Cd isotope ratios could also provide new tool for identifying the Cd-avoiding crop cultivars.

Effects of Cadmium Stress on Leaf Chlorophyll Fluorescence and Photosynthesis of Elsholtzia argyi--A Cadmium Accumulating Plant.

A hydroponic experiment was conducted to investigate the effects of cadmium (Cd) on chlorophyll fluorescence and photosynthetic parameters on a Cd accumulating plant of Elsholtzia argyi. Four weeks-seedlings of E. argyi were treated with 0 (CK) 5, 10, 15, 20, 25, 30, 40, 50 and 100 µmol L(-1) Cd for 21 days. Fv/Fo, Fv/Fm, qP, ΦPSП, ETR and Fv'/Fm' were significantly increased under low Cd (5-15 µmol L(-1) for Fv/Fo, Fv/Fm and qP, 5-10 µmol L(-1) for ΦPSП, ETR and Fv'/Fm') stress, and these parameters were similar to control under Cd≤50 µmol L(-1). All above parameters were significantly decreased at 100 µmol L(-1) Cd. Compared with control, Pn was significantly (P<0.05) increased under 5-30 µmol L(-1) Cd. However, 50 and 100 µmol L(-1) Cd significantly (P < 0.05) reduced it. Gs and Tr were substantially decreased at 50-100 and 40-100 µmol L(-1) Cd, respectively. Ci was significantly increased at 50 and 100 µmol L(-1) Cd. High Cd-induced decrease of Pn is not only connected to stomatal limitation but also to the inhibition of Fv/Fo, Fv/Fm, ΦPSП, qP, ETR and increase of NPQ. Maintain chlorophyll fluorescence and photosynthesis parameters under its Cd tolerance threshold were one of tolerance mechanisms in E. argyi.

Cadmium tolerance and accumulation of Elsholtzia argyi origining from a zinc/lead mining site - a hydroponics experiment.

In this study, a hydroponics experiment was conducted to investigate the characteristics of Cd tolerance and accumulation of Elsholtzia argyi natively growing on the soil with high levels of heavy metals in a Zn/Pb mining site. Seedlings of E. argyi grown for 4 weeks and then were treated with 0(CK), 5,10,15, 20, 25, 30, 40, 50,100 umM Cd for 21 days. Each treatment had three replications. No visual toxic symptoms on shoots of E. argyi were observed at Cd level < or = 50 muM. The results indicated that the dry biomass of each tissue and the whole plants of the treatments with < or =40 umM cadmium were similar to that of the control, implying that E. argyi was a cadmium tolerant plant. The results also showed that the shoot Cd concentration significantly (P < 0.05) increased with the increase in the Cd level in nutrient solution. The shoot Cd concentration of the treatment with 40 umM Cd was as high as 237.9 mg kg(-1), which was higher than 100 mg kg(-1), normally used as the threshold concentration for identifying the Cd hyperaccumulating plant. It could be concluded that E. argyi was a Cd tolerant and accumulating plant species.

Rhizosphere concentrations of zinc and cadmium in a metal contaminated soil after repeated phytoextraction by Sedum plumbizincicola.

A growth chamber pot experiment and a field plot experiment were conducted with the installation of rhizobags to study the effects of repeated phytoextraction by Sedum plumbizincicola on the bioavailability of Cd and Zn in the rhizosphere and bulk soil Repeated phytoextraction gave significantly lower Cd and Zn concentrations in both rhizosphere and bulk soil solutions compared with soil without repeated phytoextraction. The depletion rates of NH40Ac-extractable Zn in rhizosphere soil in each treatment (L-PS, L-NPS, H-PS, and H-NPS) were 59.7, 18.0, 16.3, and 18.6%, respectively. For NH40Ac-extractable Cd, the depletion rates in treatments L-PS, L-NPS, H-PS, and H-NPS were 6.67, 29.4, 40.3, and 41.4%, respectively. Plant shoot biomass decreased in the order H-PS > H-NPS > L-PS > L-NPS, with dry weights of 0.56, 0.42, 1.43, and 1.21 g pot(-1), respectively. Plant Cd uptake increased with increasing aqua-regia extractable metal concentrations. The NH4OAc extraction procedure was satisfactory to predict the bioavailability of Cd and Zn in rhizosphere soil in terms of shoot uptake by S. plumbizincicola with positive correlation coefficients of 0.545 (p < 0.05) and 0.452 (p < 0.05), respectively. The field study results show a slight decrease in water soluble and NH4OAc-extractable metals, a trend similar to that found in the pot experiment.