[Blocking Effects of Foliar Conditioners on Cadmium, Arsenic, and Lead Accumulation in Wheat Grain in Compound-contaminated Farmland].

Heavy metal contamination of soil has become a hot issue of social concern due to its impact on the safety of agricultural products in recent years. Wheat is one of the most dominant staple food crops worldwide and has become a major source of toxic metals in human diets. Foliar application was considered to be a more efficient and economical method of heavy metal remediation. Field experiments were carried out in Cd-, As-, and Pb-contaminated farmland soils. The effects of foliar conditioners on the accumulation of Cd, As, and Pb in wheat grains were investigated after being sprayed with Zn (0.2% ZnSO4), Mg (0.4% MgSO4), and Mn (0.2% MnSO4) separately and in combination. Thus, the effective foliar conditioners were selected to block the accumulation of Cd, As, and Pb in wheat grains grown in combined heavy metal-contaminated farmland in north China. The results showed that, compared with that in the control, the Cd, As, and Pb contents in wheat grains of the Zn+Mg+Mn foliar treatment were significantly decreased by 18.96%, 23.87%, and 51.31%, respectively, and TFgrain/straw decreased by 14.62%, 27.73%, and 47.70%, respectively. Thus, spraying the compound foliar conditioner of Zn+Mg+Mn could effectively reduce heavy metal accumulation in wheat grains through inhibition translocation of those metals from stem leaves to grain. In addition, the results indicated that Cd and As were mainly distributed at the central endosperm (34.08%-37.08%), whereas Pb was primarily distributed at the pericarp and seed coat (27.78%) of the wheat grain. Compared with that in the control, spraying the compound foliar conditioner of Zn+Mg+Mn extremely decreased Cd and As accumulation in the aleurone layer of the wheat grain by 81.10% and 82.24%, respectively. Except for the pericarp, seed coat, and central endosperm layers, the Pb content in each grain layer was dramatically decreased by 42.85% to 91.15%. There was only a significant negative correlation between heavy metal content and Zn content in the aleurone layer (P2) of wheat flour. In summary, the accumulation of Cd, As, and Pb in wheat grains, especially in the aleurone layer, could be effectively reduced by foliar conditioner application at the jointing, booting, and early filling stages of wheat, separately. Furthermore, besides the foliar treatment, removing wheat bran to reduce Cd contamination in wheat grains is highly recommended to ensure the safe production of wheat.

[Distribution and Transport of Cadmium and Arsenic in Different Aboveground Parts of Wheat After Flowering].

To investigate the effects of leaves and stems on the accumulation and transport of cadmium(Cd) and arsenic(As) in wheat shoots after flowering, a field experiment was conducted in a typical Cd and As co-contaminated agricultural land to explore the distribution and translocation of Cd and As in the different parts of two wheat cultivars after flowering. The results showed that Cd was mainly distributed in the nodes of two varieties, and the translocation factors of Cd from internode 3 to node 2, from internode 2 to node 1, and from sheath 1 to node 1 were markedly higher than those of other aboveground parts during the grain-filling stage. However, Cd was mainly distributed in the leaves, and the translocation factors of Cd from sheath to leaf and from node 1 to rachis was significantly higher than those of other parts at the mature stage. In addition, the transport capacity of Cd from glume to rachis and from rachis to grain in JM22 was significantly lower than that in SN28, which significantly reduced Cd concentrations in the rachis, glume, and grain of JM22 by 22.3%, 40.8%, and 44.4%, respectively. Meanwhile, As was mainly distributed in the wheat leaves from the grain-filling stage to the mature stage, and As concentrations in the glume and grain of JM22 were 25.8% and 33.3% lower than those of SN28, respectively. Additionally, the translocation factors of As from the sheath to the node were significantly 438% and 190% higher than that from leaf to sheath and from node to internode during the whole grain filling stage and mature stage. Moreover, the translocation factors of As from glumes to grains and from rachis to grains in JM22 were 40.6% and 44.4% lower than that in SN28, respectively. In summary, flag leaf, node 1, and the rachis had regulated Cd transport and accumulation in wheat grains, whereas leaf 3, flag leaf, node 1, the glumes, and the rachis were mainly responsible for As transport and accumulation in wheat grains.

Transcriptomic mechanisms of reduced PM2.5-Pb retention in the leaves of the low-Pb-accumulation genotype of Chinese cabbage.

Atmospheric fine particulate matter (PM2.5) mainly contributes to Pb accumulation in the edible leaves of Chinese cabbage in North China. It was found that a low-Pb-accumulation (LPA) genotype of Chinese cabbage contained less Pb in leaves than high-Pb-accumulation (HPA) genotype exposed to PM2.5-Pb. However, there are no data on the transcriptional regulatory mechanisms of foliar PM2.5-Pb uptake by Chinese cabbage. The present study investigated the retention of PM2.5-Pb in foliar apoplast and symplasm and the underlying molecular mechanisms of reduced Pb in LPA leaves. It appeared more Pb in apoplast and less Pb in symplasm of LPA leaves, whereas the pattern was opposite in HPA. There were 2646 and 3095 differentially expressed genes (DEGs) in LPA and HPA leaves under PM2.5-Pb stress with clearly genotype-specific function, respectively. Furthermore, mRNA levels of XTH16 regulating cell wall thickening, PME2 and PME6 involved in cell wall remodification were significantly expressed in LPA, but not in HPA. Meanwhile, foliar PM2.5-Pb stress downregulated expression of ZIP1, YSL1, and CNGC3 responsible for Pb influx to cell, and upregulated expression of ABCG36 regulated Pb efflux from symplasm in LPA leaves. These results improve our understanding to the mechanisms underlying foliar Pb uptake from PM2.5-Pb at transcriptomic level.

[Characteristics and Health Risk Assessment of Cadmium, Lead, and Arsenic Accumulation in Leafy Vegetables Planted in a Greenhouse].

In recent years, dust pollution has occurred frequently in spring and haze or fog in autumn and winter. The inhalable particulate matters in the atmosphere, especially PM2.5, loaded in heavy metals such as cadmium, lead, and arsenic, are easily taken up by leafy vegetables and accumulate in the edible parts. It is not clear whether the accumulation of heavy metals in the edible parts of leafy vegetables in greenhouses is also affected by atmospheric deposition. Therefore, a field experiment was conducted to explore characteristics and health risk assessment of cadmium, lead, and arsenic accumulation in leafy vegetables planted in a greenhouse using six types of common leafy vegetables (spinach, leaf lettuce, lettuce, pakchoi, Chrysanthemum coronarium, and fennel) in the Beijing-Tianjin-Hebei region. The results showed that C. coronarium, pakchoi, and spinach are the leafy vegetables with a low accumulation of Cd, Pb, and As, respectively. Fennel is the leafy vegetable with a low accumulation of Cd and Pb. In the greenhouse, Pb concentrations in PM2.5 were 42.6 and 8.4 times of Cd and As, respectively. Moreover, PM2.5-Pb contributed on average 36.5% to the edible parts of six kinds of leafy vegetables, which indicated that the Cd, Pb, and As accumulated in leafy vegetables were mainly derived from the soil. Meanwhile, the concentrations of Cd, Pb, and As in the edible parts of vegetables did not exceed the safety limitations of three heavy metals (GB 2762-2017), and Pb accumulation in leafy vegetables does not pose a health risk to humans. However, Cd in the leafy vegetables could threaten the health of adults and children, except for the intake of fennel. Conversely, As in the C. coronarium could threaten the health of adults and children.

Mechanism of Pb accumulation in Chinese cabbage leaves: Stomata and trichomes regulate foliar uptake of Pb in atmospheric PM2.5.

Chinese cabbage (Brassica rapa ssp. pekinensis) is one of the most popular and frequently consumed leafy vegetables. It was found that atmospheric PM2.5-Pb contributes to Pb accumulation in the edible leaves of Chinese cabbage via stomata in North China during haze seasons with high concentrations of fine particulate matter in autumn and winter. However, it is unclear whether both stomata and trichomes co-regulate foliar transfer of PM2.5-Pb from atmospheric deposition to the leaf of Chinese cabbage genotypes with trichomes. Field and hydroponic experiments were conducted to investigate the effects of foliar uptake of PM2.5-Pb on Pb accumulation in leaves using two genotypes of Chinese cabbage, one without trichomes and one with trichomes. It was verified that open stoma is a prominent pathway of foliar PM2.5-Pb transfer in the short-term exposure for 6 h, contributing 74.5% of Pb accumulation in leaves, whereas Pb concentrations in the leaves of with-trichome genotype in the rosette stage were 6.52- and 1.04-fold higher than that of without-trichome genotype in greenhouse and open field, respectively, which suggests that stomata and trichomes co-regulate foliar Pb uptake of from atmospheric PM2.5. Moreover, subcellular Pb in the leaves was distributed in the following order of cytoplasm (53.8%) > cell wall (38.5%)> organelle (7.8%), as confirmed through high-resolution secondary ion mass spectrometry (NanoSIMS). The Leadmium™ Green AM dye manifested that Pb in PM2.5 entered cellular space of trichomes and accumulated in the basal compartment, enhancing foliar Pb uptake in the edible leaves of cabbage. The results of these experiments are evidence that both stomata and trichomes are important pathways in the regulation of foliar Pb uptake and translocation in Chinese cabbage.

Bioimaging of Pb by LA-ICP-MS and Pb isotopic compositions reveal distributions and origins of Pb in wheat grain.

Atmospheric heavy metal deposition in agroecosystems has increased recently, especially in northern China, which poses serious risks to crop safety and human health via food chain. Wheat grains can accumulate high levels of Pb even when wheat is planted in soils with low levels of Pb. However, the influence of atmospheric deposition on the accumulation and distribution of Pb in wheat grain is still unclear. A field survey was conducted in three districts (A: a district with industrial and traffic pollution; B: a district with traffic pollution; and C: an unpolluted district) in Hebei Province, North China. The grain of wheat cultivated in district A accumulated more Pb from soil and atmospheric deposition than those in other districts, and the bran from district A contained 3.50 and 2.04 times more Pb than those from districts B and C, respectively. The Pb distribution pattern in wheat grain detected by laser ablation inductively coupled mass spectrometry (LA-ICP-MS) was characterized by accumulation mostly in the pericarp and seed coat rather than in the crease, embryo and endosperm. Furthermore, Pb isotopic data showed that airborne Pb was the major source (>50%) of Pb in wheat grain. Interestingly, average contributions of Pb from atmospheric deposition to white flour (78.22%) were higher than its contributions to bran (56.27%). In addition, wheat flag leaves were exposed to PbSO4 at the booting stage, and much greater Pb accumulation (0.33-0.48 mg/kg) was observed in exposed wheat grain than in the control (P < 0.05), PbSO4 constituted most (82.80-100%) of the Pb in the wheat grain. In summary, the results confirmed the efficient foliar Pb uptake and transfer from atmospheric deposition into wheat grain. It would be a new sight for understanding the contribution of airborne Pb to Pb accumulation in wheat grains.

[Uptake and Accumulation of Cadmium and Zinc by Two Energy Grasses: A Field Experiment].

The remediation potential of large biomass energy grasses in cadmium-contaminated soil remains ambiguous. A field experiment was carried out in a cadmium-contaminated farmland using two energy grasses and two control plants. The two energy grasses were hybrid pennisetum (Pennisetum americanum×P. purpureum, PAP) and purple elephant grass (P. purpureum 'Purple', PPP), and the two control plants were Iris lactea var. chinensis (ILC) and a cadmium hyperaccumulator, Noccaea caerulescens (NC). The results showed that the aboveground biomass of PAP was the largest among the four plants, and 126 and 36 times that of NC and ILC, respectively, but no significant difference with that of PPP. The concentrations of cadmium and zinc in the shoots and roots of NC were significantly higher than in the other plants. Zinc concentrations in the shoots and roots of ILC were lower than in the other plants, while cadmium concentrations were significantly higher than in PAP and PPP (P<0.05). The amounts of cadmium and zinc accumulated in the shoots of PPP were the highest among the four plants, while cadmium concentrations in the shoots and roots of PPP were significantly lower than in ILC and NC (P<0.05). Cadmium amounts accumulated in PPP shoots were 7.0 and 4.1 times that of ILC and NC, respectively. Zinc amounts accumulated in PPP shoots were 41 and 11 times that of ILC and NC, respectively (P<0.05). Cadmium accumulation in the shoots of PAP was 19.4% lower than in PPP, and zinc accumulation had no significant difference with that of PPP. NC, having a bioconcentration factor of shoot (BCFS) and a translocation factor (TF) for cadmium and zinc both larger than 1, is usable for phytoextraction of soils contaminated by cadmium and zinc. ILC, having a bioconcentration factor of root (BCFR) larger than 1 and a TF lower than 1 for cadmium, is usable for the phytostabilization of soils contaminated by cadmium. PPP, having a BCFR larger than 1 and a TF lower than 1 for zinc, can be used in the phytostabilization of soils contaminated by zinc. Under field conditions, PPP and PAP showed great potential for the extraction and removal of cadmium and zinc from soil due to their large biomass and ability to produce economic benefits, have good application prospects.

Contribution of PM2.5-Pb in atmospheric fallout to Pb accumulation in Chinese cabbage leaves via stomata.

Foliar uptake of Pb is especially important when Chinese cabbage (Brassica rapa spp. pekinensis), having a large leaf surface area, is cultivated in North China during seasons with heavy haze. However, the mechanisms of foliar Pb uptake via stomata by Chinese cabbage exposed to atmospheric fallout are unclear. A field experiment was conducted to explore the impacts of Pb in particulate matter with sizes ≤ 2.5 µm (PM2.5-Pb) from atmospheric fallout to Pb accumulation in cabbage leaves through stomata. Cabbage varieties with low-Pb-accumulation (LPA) and high-Pb-accumulation (HPA) were examined using inductively coupled plasma-mass spectrometry and scanning electron microscopy/energy-dispersive X-ray analysis. The 206Pb/207Pb and 208Pb/207Pb ratios of PM2.5, plants, and soil demonstrated that the major source of Pb in cabbage leaves was PM2.5. The average width and length of the stomatal apertures were 7.14 and 15.61 µm for LPA cabbage and 8.10 and 16.64 µm for HPA cabbage, which are large enough for PM2.5-Pb to enter the leaves. The HPA cabbage had significantly higher stomatal width-to-length ratios than the LPA cabbage, indicating that the former trapped much more PM2.5-Pb and accumulated more Pb. These results clarify the contributions of the stomatal characteristics to PM2.5-Pb accumulation in the edible parts of Chinese cabbage.

[Characteristics of Cd, As, and Pb in Soil and Wheat Grains and Health Risk Assessment of Grain-Cd/As/Pb on the Field Scale].

In recent years, heavy metal pollution in farmlands has become increasingly serious because of human activities such as metal smelting, sewage irrigation, and road traffic in China. A field survey was conducted to investigate characteristics of Cd, As, and Pb in soil and wheat grains and assess the health risk of grain-Cd/As/Pb to humans on the fields scale. The farmland was influenced by smelter and sewage irrigation in the attitude and by road traffic in the horizon. The results showed that in farmland soil with moderate pollution levels, Cd, As, and Pb concentrations in soil samples all exceeded the risk screening values of farmland soil (GB 15618-2018), and the exceeding rates were 100%, 100%, and 36.7% respectively; the exceeding rates of Cd and Pb concentrations in wheat grains were 76.7% and 13.3%, respectively (GB 2762-2017). Distance from smelter, river of sewage irrigation, and road had no significant effect on Cd, As, and Pb concentrations in soil but had a significant effect on Cd and As concentrations in wheat grains, with the median Cd and As concentrations of the closest group being 14.9% and 41.8%, respectively, higher than the highest group (P<0.05). The Pb concentrations in soil and wheat grains were influenced by road traffic; the median Pb concentrations of the closest group were 78.9% and 471%, respectively, higher than the highest group (P<0.05). Cd and As in wheat grains have carcinogenic risks (Ri>1×10-4), RCd > RAs, Rchildren > Radult, while Pb poses no health risks in this farmland.

Facile Exfoliation of 3D Pillared Metal-Organic Frameworks (MOFs) to Produce MOF Nanosheets with Functionalized Surfaces.

The production of two-dimensional (2D) ultrathin metal-organic framework (MOF) nanosheets with functionalized surfaces is significant for extending their applications. To date, no protocol has been developed yet to solve this problem. Herein, we report a facile, mild, and efficient method to produce 2D monolayer MOF nanosheets with hydrophobic surfaces from layer-pillared 3D MOFs. This approach is based on the replacement of weaker coordinating pillar ligands with stronger coordinating capping ligands with the assistance of a high concentration gradient of the latter. Utilizing this method, the replacement of the 4,4'-bipyridine (bpy) pillars in two cadmium-based layer-pillared MOFs with alkylpyridine derivatives has been achieved, producing 2D MOF nanosheets with monolayer thickness and double-sided hydrophobic surfaces. The resulting hydrophobic 2D MOF nanosheets exhibit good performance for the separation of oil and water.

H3K27me3 Signal in the Cis Regulatory Elements Reveals the Differentiation Potential of Progenitors During Drosophila Neuroglial Development.

Drosophila neural development undergoes extensive chromatin remodeling and precise epigenetic regulation. However, the roles of chromatin remodeling in establishment and maintenance of cell identity during cell fate transition remain enigmatic. Here, we compared the changes in gene expression, as well as the dynamics of nucleosome positioning and key histone modifications between the four major neural cell types during Drosophila neural development. We find that the neural progenitors can be separated from the terminally differentiated cells based on their gene expression profiles, whereas nucleosome distribution in the flanking regions of transcription start sites fails to identify the relationships between the progenitors and the differentiated cells. H3K27me3 signal in promoters and enhancers can not only distinguish the progenitors from the differentiated cells but also identify the differentiation path of the neural stem cells (NSCs) to the intermediate progenitor cells to the glial cells. In contrast, H3K9ac signal fails to identify the differentiation path, although it activates distinct sets of genes with neuron-specific and glia-related functions during the differentiation of the NSCs into neurons and glia, respectively. Together, our study provides novel insights into the crucial roles of chromatin remodeling in determining cell type during Drosophila neural development.

Anchoring CoII Ions into a Thiol-Laced Metal-Organic Framework for Efficient Visible-Light-Driven Conversion of CO2 into CO.

Using solar energy to convert CO2 into valuable fuels or chemicals offers a powerful solution to urgent energy and environmental problems. However, the development of efficient and selective catalysts remains a considerable scientific challenge. To address this, catalytically active CoII centers can be anchored into the porous matrix of metal-organic frameworks (MOFs) by utilizing a robust Zr-based MOF (Zr-DMBD) functionalized with freestanding thiol groups to enable efficient post-synthetic metal insertion. The thus-prepared Zr-DMBD-Co MOF solids are modified by well-defined Co-thiolate units and have the capability of photocatalytically converting CO2 into CO with high efficiency and selectivity under visible-light irradiation in a water-containing system. The turnover number and CO selectivity reach as high as 97 941 and 98 %, respectively.

Dinuclear Metal Synergistic Catalysis Boosts Photochemical CO2 -to-CO Conversion.

The solar-driven CO2 reduction is a challenge in the field of "artificial photosynthesis", as most catalysts display low activity and selectivity for CO2 reduction in water-containing reaction systems as a result of competitive proton reduction. Herein, we report a dinuclear heterometallic complex, [CoZn(OH)L1 ](ClO4 )3 (CoZn), which shows extremely high photocatalytic activity and selectivity for CO2 reduction in water/acetonitrile solution. It achieves a selectivity of 98 % for CO2 -to-CO conversion, with TON and TOF values of 65000 and 1.8 s-1 , respectively, 4, 19, and 45-fold higher than the values of corresponding dinuclear homometallic [CoCo(OH)L1 ](ClO4 )3 (CoCo), [ZnZn(OH)L1 ](ClO4 )3 (ZnZn), and mononuclear [CoL2 (CH3 CN)](ClO4 )2 (Co), respectively, under the same conditions. The increased photocatalytic performance of CoZn is due to the enhanced dinuclear metal synergistic catalysis (DMSC) effect between ZnII and CoII , which dramatically lowers the activation barriers of both transition states of CO2 reduction.

A Copper(II) Molecular Catalyst for Efficient and Selective Photochemical Reduction of CO2 to CO in a Water-Containing System.

A catalyst developed from a CuII complex of (Et4 N)[Cu(pyN2Me2 )(HCO2 )]⋅0.5 CH3 OH⋅H2 O (1⋅0.5 CH3 OH⋅H2 O; pyN2Me2 =bis(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate(2-)) shows a high activity to catalyze the reduction reaction of CO2 to CO driven by visible light in 4:1 acetonitrile/water (v:v) using [Ru(phen)3 ](PF6 )2 as photosensitizer and TEOA as sacrificial reductant, with a high TON of 9900 and a high CO selectivity of 98 %. The results of isotope labeling experiment, durability tests and energy dispersive spectroscopy reveal that 1 is robust during the photocatalytic process.

The role of Melatonin receptor MTNR1A in the action of Melatonin on bovine granulosa cells.

Granulosa cells (GCs) play an important role in ovarian follicle growth, development, and follicular atresia. In the present study, we investigated the effects of Melatonin on bovine GCs, and asked if MTNR1A was involved in their response to this indole hormone. Our results indicated that Melatonin inhibited GC apoptosis by up-regulating the expression of BCL2, BCL-XL, GPX4, and SOD1, and down-regulating the expression of BAX, CASP3, and TP53. Moreover, Melatonin modulated bovine GC function by decreasing the expression of INHA, INHBB, FSHR, and TGFBR3, and the abundance of Inhibin ß and Activin B, while increasing the expression of LHR, INHBA, and secretion of progesterone by GCs. In contrast, knockdown of MTNR1A significantly increased the expression of BAX, CASP3, TP53, INHA, FSHR, and TGFBR3, as well as Inhibin ß abundance, while decreasing the expression of BCL2, GPX4, SOD1, and LHR, and production of progesterone and estradiol; no effect was observed on the expression of BCL-XL, INHBA, or INHBB. These results suggest that Melatonin and MTNR1A play an important role in modulating bovine GC function by regulating cellular progression, apoptosis, hormones secretion, and reproduction-related genes. Furthermore, altered expression of MTNR1A could affect how bovine GCs respond to Melatonin.

A Highly Selective and Robust Co(II)-Based Homogeneous Catalyst for Reduction of CO2 to CO in CH3CN/H2O Solution Driven by Visible Light.

Visible-light driven reduction of CO2 into chemical fuels has attracted enormous interest in the production of sustainable energy and reversal of the global warming trend. The main challenge in this field is the development of efficient, selective, and economic photocatalysts. Herein, we report a Co(II)-based homogeneous catalyst, [Co(NTB)CH3CN](ClO4)2 (1, NTB = tris(benzimidazolyl-2-methyl)amine), which shows high selectivity and stability for the catalytic reduction of CO2 to CO in a water-containing system driven by visible light, with turnover number (TON) and turnover frequency (TOF) values of 1179 and 0.032 s-1, respectively, and selectivity to CO of 97%. The high catalytic activity of 1 for photochemical CO2-to-CO conversion is supported by the results of electrochemical investigations and DFT calculations.

[Intracorporeal Roux-en-Y reconstruction after laparoscopic distal gastrectomy: a report of 20 cases].

OBJECTIVE: To investigate the safety and feasibility of intracorporeal Roux-en-Y reconstruction after laparoscopic distal gastrectomy. METHODS: Clinical data of 20 patients undergoing laparoscopic distal gastrectomy and intracorporeal Roux-en-Y reconstruction in our hospital from August 2012 to March 2013 were analyzed retrospectively. RESULTS: Totally laparoscopic distal gastrectomy was successfully performed in all the patients. The mean operation time was (190.8±53.6) min, the mean operative blood loss was(122.4±57.7) ml, and mean number of harvested lymph node was 31.2±5.7. Tumor-free proximal margin was confirmed by pathological examination in all the patients. The mean time to first flatus and hospital stay were (2.6±1.6) d and (8.1±2.0) d. One case developed pulmonary infection postoperatively, but no anastomosis related complication was observed. CONCLUSION: Intracorporeal Roux-en-Y reconstruction after laparoscopic distal gastrectomy is safe and feasible.

[Variations of arsenic species in the solution of arsenic-contaminated paddy soil under flooding and at different temperatures].

Taking arsenic (As)-contaminated paddy soil as test object, and by using high performance liquid chromatography inductively coupled plasma-mass spectrometry (HPLC-ICP-MS), this paper studied the variations of As species in soil solution when the soil was sterilized or non-sterilized and incubated at different temperatures (5, 27, and 50 degrees C) under flooding. In the soil solution (pore water), only As(III) (arsenite), As(V) (arsenate), and DMA(V) ( dimethylarsinic acid) were detected, but no MMA(V)(mono methylarsinic acid) was found. With the increasing time of flooding and at the test temperatures, arsenite became the predominant species, averagely accounting for 64%, followed by As(V), with the proportion of 35%, and DMA(V), with the least proportion of 1%. Soil sterilization or non-sterilization had less effect on the concentrations of As(III) and DMA(V) in the soil solution, but remarkably affected the reduction of As(V) and the methylation of As(III). The promotion effect of soil sterilization decreased gradually with the increasing time of flooding and incubation. At 50 degrees C and after flooded for 23 days, the DMA(V) concentration in sterilized soil solution was the highest and up to 23.7 ng x mL(-1), indicating that some thermophilic microbes remained in sterilized soil became predominant species, and promoted the methylation of As(III) In sum, the total arsenic concentration in non-sterilized soil at incubation temperature 27 degrees C and flooded for 23 days was relatively low (501 ng x mL(-1)), and thus, in As-contaminated paddy rice planting areas, to adopt the water management mode of short cycle flooding-non-flooding could decrease the As level in soil solution as far as possible, and in the same time, save water resources and ensure yielding.

Arsenic speciation in Chinese Herbal Medicines and human health implication for inorganic arsenic.

Rice and drinking water are recognized as the dominant sources of arsenic (As) for human intake, while little is known about As accumulation and speciation in Chinese Herbal Medicines (CHMs), which have been available for many hundreds of years for the treatment of diseases in both eastern and western cultures. Inorganic arsenic was the predominant species in all of CHMs samples. The levels of inorganic arsenic in CHMs from fields and markets or pharmacies ranged from 63 to 550 ng/g with a mean of 208 ng/g and 94 to 8683 ng/g with a mean of 1092 ng/g, respectively. The highest concentration was found in the Chrysanthemum from pharmacies. It indicates that the risk of inorganic As in CHMs to human health is higher in medicines from markets or pharmacies than that collected directly from fields. Some CHMs may make a considerable contribution to the human intake of inorganic arsenic.