Author：Williamson, G;Chen, Z

Abstract:In paddy soil the reductive dissolution of iron oxide and the availability of organic matter plays an important role in arsenic release under anaerobic conditions. Microbial fuel cells have been shown to reduce organic matter (OM) content and the rate in which this occurs strongly relate to the external resistance applied. In this study we investigated the effects of bioanode operating at different external resistance on the paddy soil microbial community and iron and arsenic concentration. The results show that MFC can be used to reduce soil pore water iron and arsenic concentration and the extent in which this occurs depend on the external resistance applied. The MFC is able to mitigate arsenic release by decreasing organic matter availability. Furthermore, our finding shows that external resistance had a significant influence on the bacterial community composition that develop on the bioanode however only had minimal effect on the community of the bulk soil. These findings suggest that the sMFC can influence the iron and arsenic concentration by reducing OM content and the microbial community that develop in the bioanode vicinity.

Author：Davies-Colley, RJ;Ballantine, DJ;Elliott, SH;Swales, A;Hughes, AO;Gall, MP

Abstract:Fine sediment continues to be a major diffuse pollution concern with its multiple effects on aquatic ecosystems. Mass concentrations (and loads) of fine sediment are usually measured and modelled, apparently with the assumption that environmental effects of sediment are predictable from mass concentrations. However, some severe impacts of fine sediment may not correlate well with mass concentration, notably those related to light attenuation by suspended particles. Light attenuation per unit mass concentration of suspended particulate matter in waters varies widely with particle size, shape and composition. Data for suspended sediment concentration, turbidity and visual clarity (which is inversely proportional to light beam attenuation) from 77 diverse New Zealand rivers provide valuable insights into the mutual relationships of these quantities. Our analysis of these relationships, both across multiple rivers and within individual rivers, supports the proposition that light attenuation by fine sediment is a more generally meaningful basis for environmental management than sediment mass. Furthermore, optical measurements are considerably more practical, being much cheaper (by about four-fold) to measure than mass concentrations, and amenable to continuous measurement. Mass concentration can be estimated with sufficient precision for many purposes from optical surrogates locally calibrated for particular rivers.

Author：Juvigny-Khenafou, NPD;Zhang, YX;Piggott, JJ;Atkinson, D;Matthaei, CD;Van Bael, SA;Wu, NC

Abstract:Despite the progress made in environmental microbiology techniques and knowledge, the succession and functional changes of the microbial community under multiple stressors are still poorly understood. This is a substantial knowledge gap as microbial communities regulate the biogeochemistry of stream ecosystems. Our study assessed the structural and temporal changes in stream fungal and bacterial communities associated with decomposing leaf litter under a multiple-stressor scenario. We conducted a fully crossed 4-factor experiment in 64 flow-through mesocosms fed by a pristine montane stream (21 days of colonisation, 21 days of manipulations) and investigated the effects of nutrient enrichment, flow velocity reduction and sedimentation after 2 and 3 weeks of stressor exposure. We used high-throughput sequencing and metabarcoding techniques (16S and 18S rRNA genes) to identify changes in microbial community composition. Our results indicate that (1) shifts in relative abundances of the pre-existing terrestrial microbial community, rather than changes in community identity, drove the observed responses to stressors; (2) changes in relative abundances within the microbial community paralleled decomposition rate patterns with time; (3) both fungal and bacterial communities had a certain resistance to stressors, as indicated by relatively minor changes in alpha diversity or multivariate community structure; (4) overall, stressor interactions were more common than stressor main effects when affecting microbial diversity metrics or abundant individual genera; and (5) stressor effects on microbes often changed from 2 weeks to 3 weeks of stressor exposure, with several response patterns being reversed. Our study suggests that future research should focus more on understanding the temporal dynamics of fungal and bacterial communities and how they relate to ecosystem processes to advance our under- standing of the mechanisms associated with multiple-stressor interactions. (C) 2019 Elsevier B.V. All rights reserved.

Author：Wang, SQ;Qu, CY;Liu, L;Li, LH;Li, T;Qin, SJ;Zhang, T

Abstract:Rhinophore, a bio-chemical sensory organ with soft and stretchable/retractable features in many marine molluscs species, exhibits tunable chemosensory abilities in terms of far/near-field chemical detection and molecules' source orientation. However, existing artificial bio-chemical sensors cannot provide tunable modality sensing. Inspired by the anatomical units (folded sensory epithelium) and the functions of a rhinophore, this work introduces a stretchable electrochemical sensor that offers a programmable electro-catalytic performance towards glucose based on the fold/unfold regulation of the gold nanomembrane on an elastic fiber. Geometrical design rationale and covalent bonding strategy are used to realize the robust mechanical and electrical stability of this stretchable bionic sensor. Electrochemical tests demonstrated that the sensitivities of the as-prepared bionic sensor exhibit a linear relationship with its strain states from 0%% to 150%%. Bio-inspired sensory functions are tested by regulating the strain of the bionic sensor. The sensor achieves a sensitivity of 195.4 mu A mM(-1) in a low glucose concentration range of 8-206 mu M at 150%% strain for potentially far-field chemical detection, and a sensitivity of 14.2 mu A mM(-1) in a high concentration range of 10-100 mM at 0%% strain for near-field chemical detection. Moreover, the bionic sensor performs the detection while extending its length can largely enhance the response signal, which is used to distinguish the molecules' source direction. This proposed bionic sensor can be useful in wearable devices, robotics and bionics applications which require diverse modality sensing and smart chemical tracking system.

Author：Guo, K;Wu, NC;Wang, C;Yang, DG;He, YF;Luo, JB;Chai, Y;Duan, M;Huang, XF;Riis, T

Abstract:Using metacommunity theory to understand the mechanisms shaping community structure is a promising framework that has been widely applied to ecological research. In lakes, the spatial pattern of phytoplankton assemblages depends on the relative importance of environmental conditions, spatial processes, and biotic interactions (e.g., grazing pressure), but the inclusion of the latter two factors was often overlooked. We tested how these three factors contributed to phytoplankton community composition in a shallow lake by separating the responses of taxonomic and trait compositions (i.e., nine species traits groups) of phytoplankton in Lake Changhu, China. Our results indicated that the taxonomic composition of phytoplankton assemblages in Lake Changhu are mainly determined by environmental factors (7.6 +/- 1.3%%), followed by spatial processes (4.7 +/- 1.0%%) and grazing pressure (2.9 +/- 0.5%%). However, for the nine species traits groups, relative influences of environmental, spatial and grazing factors were trait specific, suggesting that different mechanisms were responsible for community composition supporting the potential advantages of using traits in water quality assessment. More specifically, some traits (e.g., large cell size and filamentous) may be excellent candidates for biomonitoring in lakes as they are predominantly driven by environmental factors (12.4%% and 17.2%% for large cell size and filamentous respectively), while other traits (e.g., unicellular and non-motile) are controlled largely by spatial processes or grazing and may not be suitable as bio-indicators. We also advocate inclusion of biotic factors (e.g., grazing pressure) in community studies, since we have found relatively weak but unneglectable effects of grazing on structuring phytoplankton community (2.9 +/- 0.5%% for taxonomic composition while 3.1 +/- 4.1%% for trait composition). In general, our findings suggest that a combination of metacommunity theory and the use of traits provide a useful framework for assessing driving factors structuring phytoplankton community in lakes, and such framework can be very useful for future lake bioassessment and management efforts.

Author：Zhu, XH;Yue, Y;Wong, PWH;Zhang, YX;Ding, H

Abstract:The optimized design of water quality monitoring networks can not only minimize the pollution detection time and maximize the detection probability for river systems but also reduce redundant monitoring locations. In addition, it can save investments and costs for building and operating monitoring systems as well as satisfy management requirements. This paper aims to use the beneficial features of multi-objective discrete particle swarm optimization (MODPSO) to optimize the design of water quality monitoring networks. Four optimization objectives: minimum pollution detection time, maximum pollution detection probability, maximum centrality of monitoring locations and reservation of particular monitoring locations, are proposed. To guide the convergence process and keep reserved monitoring locations in the Pareto frontier, we use a binary matrix to denote reserved monitoring locations and develop a new particle initialization procedure as well as discrete functions for updating particle's velocity and position. The storm water management model (SWMM) is used to model a hypothetical river network which was studied in the literature for comparative analysis of our work. We define three pollution detection thresholds and simulate pollution events respectively to obtain all the pollution detection time for all the potential monitoring locations when a pollution event occurs randomly at any potential monitoring locations. Compared to the results of an enumeration search method, we confirm that our algorithm could obtain the Pareto frontier of optimized monitoring network design, and the reserved monitoring locations are included to satisfy the management requirements. This paper makes fundamental advancements of MODPSO and enables it to optimize the design of water quality monitoring networks with reserved monitoring locations.

Author：Zhou, SC;Wu, NC;Zhang, M;Peng, WQ;He, FZ;Guo, K;Yan, SY;Zou, Y;Qu, XD

Abstract:Understanding processes and mechanisms driving patterns of species distribution and diversity is a vital theme in community ecology and conservation biology. There has been a continuous increase in studies focusing on diversity patterns in freshwater ecosystems during the last few decades. However, comparative studies of species distributions, diversity patterns and underlying processes across trophic levels remain limited. The unique characteristics of the study area (i.e. Hun-Tai River in Northeast China) generates a wide range of environmental conditions to advance our understanding of what drives community assembly and diversity pattern of three stream organism groups. We applied variance partitioning (VPA) to correlate community compositions with environmental and spatial factors to infer stochastic and deterministic assembly processes, respectively. Linear regression (LR) models were used to identify the main drivers of species richness and local contributions to beta diversity (LCBD) as a function of different factors, including local environmental (e.g., in situ parameters, hydrology, nutrients), geo-climatic variables (e.g., land use, topography, climate) and spatial factors. Results indicated that species compositions of stream biota showed significant correlations with local environmental, geoclimatic and spatial factors. VPA demonstrated that both paradigms (i.e. deterministic and stochastic processes) interact to influence the biota distributions with stochastic process contributing more than deterministic process. In addition, the strongest stochastic process was found in fishes (10%%), followed by benthic algae and macroinvertebrates with the same effects (8%%). Notably, geo-climatic factors explained a substantial fraction of species composition, richness and beta diversity, although their effects were partially manifested via local and spatial variables. We demonstrate the relative importance of both stochastic and deterministic processes in shaping community composition and biodiversity of three stream organism groups in a large basin. This emphasizes the need to move beyond observed patterns and consider metacommunity theory into river management and conservation practices.

Author：Zhang, XK;Qin, BQ;Deng, JM;Wells, M

Abstract:As the world burden of environmental contamination increases, it is of the utmost importance to develop streamlined approaches to environmental risk assessment in order to prioritize mitigation measures. Whole-cell biosensors or bioreporters and speciation modeling have both become of increasing interest to determine the bioavailability of pollutants, as bioavailability is increasingly in use as an indicator of risk. Herein, we examine whether bioreporter results are able to reflect expectations based on chemical reactivity and speciation modeling, with the hope to extend the research into a wider framework of risk assessment. We study a specific test case concerning the bioavailability of lead (Pb) in aqueous environments containing Pb-complexing ligands. Ligands studied include ethylene diamine tetra-acetic acid (EDTA), meso-2,3 dimercaptosuccinic acid (DMSA), leucine, methionine, cysteine, glutathione, and humic acid (HA), and we also performed experiments using natural water samples from Lake Tai (Taihu), the third largest lake in China. We find that EDTA, DMSA, cysteine, glutathione, and HA amendment significantly reduced Pb bioavailability with increasing ligand concentration according to a log-sigmoid trend. Increasing dissolved organic carbon in Taihu water also had the same effect, whereas leucine and methionine had no notable effect on bioavailability at the concentrations tested. We find that bioreporter results are in accord with the reduction of aqueous Pb2+ that we expect from the relative complexation affinities of the different ligands tested. For EDTA and HA, for which reasonably accurate ionization and complexation constants are known, speciation modeling is in agreement with bioreporter response to within the level of uncertainty recognised as reasonable by the United States Environmental Protection Agency for speciation-based risk assessment applications. These findings represent a first step toward using bioreporter technology to streamline the biological confirmation or validation of speciation modeling for use in environmental risk assessment. (C) 2017 Elsevier Ltd. All rights reserved,

Author：Sak, H;Yang, GY;Li, BL;Li, WF

Abstract:This paper introduces a portfolio approach for quantifying pollution risk in the presence of PM concentration in cities. The model used is based on a copula dependence structure. For assessing model parameters, we analyze a limited data set of PM levels of Beijing, Tianjin, Chengde, Hengshui, and Xingtai. This process reveals a better fit for the t-copula dependence structure with generalized hyperbolic marginal distributions for the PM log-ratios of the cities. Furthermore, we show how to efficiently simulate risk measures clean-air-at-risk and conditional clean-air-at-risk using importance sampling and stratified importance sampling. Our numerical results show that clean-air-at-risk at 0.01 probability level reaches up to (initial PM concentrations of cities are assumed to be ) for the constructed sample portfolio, and that the proposed methods are much more efficient than a naive simulation for computing the exceeding probabilities and conditional excesses.

Author：Ballantine, DJ;Davies-Colley, RJ

Abstract:Recent assessments of water quality in New Zealand have indicated declining trends, particularly in the 40 %% of the country's area under pasture. The most comprehensive long-term and consistent water quality dataset is the National Rivers Water Quality Network (NRWQN). Since 1989, monthly samples have been collected at 77 NRWQN sites on 35 major river systems that, together, drain about 50 %% of New Zealand's land area. Trend analysis of the NRWQN data shows increasing nutrient concentrations, particularly nitrogen (total nitrogen and nitrate), over 21 years (1989-2009). Total nitrogen and nitrate concentrations were increasing significantly over the first 11 years (1989-2000), but for the more recent 10-year period, only nitrate concentrations continued to increase sharply. Also, the increasing phosphorus trends over the first 11 years (1989-2000) levelled off over the later 10-year period (2000-2009). Conductivity has also increased over the 21 years (1989-2009). Visual clarity has increased over the full time period which may be the positive result of soil conservation measures and riparian fencing. NRWQN data shows that concentrations of nutrients increase, and visual clarity decreases (i.e. water quality declines), with increasing proportions of pastoral land in catchments. As such, the increasing nutrient trends may reflect increasing intensification of pastoral agriculture.

Author：Zhao, ZH;Wang, JH;Fu, CX;Liu, DW;Li, BL

Abstract:The research on the green roof is of great importance in the field of urban beautification and improving ecological effect. According to the previous research, plants have shown a significant impact on the absorption of PM2.5. Therefore, it is justified that the appropriate planting design or some particular combinations of plants can be considered as a solution, dealing with the urban fine particulate matter (PM2.5). This paper presented a work in progress on developing wireless sensor networks (WSN) system based on a prototype wind tunnel, which is used for the simulation of the green roof. Several data collection processes are handled by this system, where the concentration of PM2.5, wind speed, temperature & relative humidity are obtained and stored in the database simultaneously. Additionally, users are able to real-timely define their commands in details, controlling the sensor's height through a GUI on the website. Experimental and simulation results and measurements have verified the validity of the wind tunnel module as well as the reliability of the sensor network. The system can be operated on thousands of devices when the packet delay maintained in a low level.

Author：Ballantine, DJ;Hughes, AO;Davies-Colley, RJ

Abstract:Many river water quality monitoring programmes do not measure suspended particulate matter (SPM) mass concentrations despite significant interest in its multiple effects on aquatic ecosystems. Regular monthly sampling usually intercepts rivers in baseflow when suspended sediment mass concentrations and fluxes are relatively low and not of particular interest. New Zealand's National Rivers Water Quality Network (NRWQN) is probably typical in not measuring SPM mass, although visual clarity and nephelometric turbidity are routinely measured. In order to better characterize SPM in NZ rivers, total suspended sediment (TSS) was temporarily added to the NRWQN. Turbidity, visual clarity and TSS are mutually inter-related over all 77 sites, although with considerable data scatter. However, within individual rivers turbidity and visual clarity are typically fairly closely related to TSS and provide fair to excellent surrogates. Therefore, TSS need not be measured routinely because it can be estimated with sufficient precision for many purposes from visibility or turbidity.

Author：Wang, FH;Qiao, M;Chen, Z;Su, JQ;Zhu, YG

Abstract:Lettuce and endive, which can be eaten raw, were planted on the manure-amended soil in order to explore the influence of plants on the abundance of antibiotic resistance genes (ARGs) in bulk soil and rhizosphere soil, and the occurrence of ARGs on harvested vegetables. Twelve ARGs and one integrase gene Until) were detected in all soil samples. Five ARGs (sulI, tetG, tetC, tetA, and tetM) showed lower abundance in the soil with plants than those without. ARGs and intI1 gene were also detected on harvested vegetables grown in manure-amended soil, including endophytes and phyllosphere microorganisms. The results demonstrated that planting had an effect on the distribution of ARGs in manure-amended soil, and ARGs were detected on harvested vegetables after growing in manure-amended soil, which had potential threat to human health. (C) 2015 Elsevier B.V. All rights reserved.

Author：Huang, LL;Huang, J;Wu, ZQ;Mo, YM;Zou, Q;Jeppesen, E;Wu, NC

Abstract:Beta diversity partitioning has currently received much attention in research of fish assemblages. However, the main drivers, especially the contribution of spatial and hydrological variables for species composition and beta diversity of fish assemblages are less well studied. To link species composition to multiple abiotic variables (i.e., local environmental variables, hydrological variables, and spatial variables), the relative roles of abiotic variables in shaping fish species composition and beta diversity (i.e., overall turnover, replacement, and nestedness) were investigated in the upstream Lijiang River. Species composition showed significant correlations with environmental, hydrological, and spatial variables, and variation partitioning revealed that the local environmental and spatial variables outperformed hydrological variables, and especially abiotic variables explained a substantial part of the variation in the fish composition (43.2%%). The overall species turnover was driven mostly by replacement (87.9%% and 93.7%% for SOrensen and Jaccard indices, respectively) rather than nestedness. Mantel tests indicated that the overall species turnover (ss(SOR) and ss(JAC)) and replacement (ss(SIM) and ss(JTU)) were significantly related to hydrological, environmental, and spatial heterogeneity, whereas nestedness (ss(SNE) or ss(JNE)) was insignificantly correlated with abiotic variables (P > 0.05). Moreover, the pure effect of spatial variables on overall species turnover (ss(SOR) and ss(JAC)) and replacement (ss(SIM) and ss(JTU)), and the pure effect of hydrological variables on replacement (ss(SIM) and ss(JTU)), were not important (P > 0.05). Our findings demonstrated the relative importance of interactions among environmental, hydrological, and spatial variables in structuring fish assemblages in headwater streams; these fish assemblages tend to be compositionally distinct, rather than nested derivatives of one another. Our results, therefore, indicate that maintaining natural flow dynamics and habitat continuity are of vital importance for conservation of fish assemblages and diversity in headwater streams.

Author：Zhao, W;Liu, L;Xu, MZ;Wang, XW;Zhang, T;Wang, YN;Zhang, ZY;Qin, SJ;Liu, Z

Abstract:1D nanoscale photodetectors have been extensively investigated for the unique geometry structure and novel physical and chemical properties. The 1D CdS materials have received much attention in the field due to its high photosensitivity and fast response, while how to achieve high responsivity is still in development, despite it is the crucial target to the excellent photodetector. Single crystal CdS nanorods (NRs) are synthesized on SiO2/Si substrate over large scale via the chemical vapor deposition method. The individual single CdS nanorod photodetector have been fabricated by using photolithography process and the responsivity of the photodetector is investigated systematically. At a very low percentage of illumination intensity (2%%, 0.5 mW cm(-2)) under 450 nm, the photodetector exhibited a high responsivity and reached at 1.23 x 10(4) A W-1 with the bias voltages of 2 V. The good crystallinity and large surface of CdS nanorod are the reasons of this excellent performance of CdS based photodetector. The strategy proposed herein appears to hold great potential for a high responsivity with low illumination intensity.

Author：He, FZ;Wu, NC;Dong, XY;Tang, T;Domisch, S;Cai, QH;Jahnig, SC

Abstract:Freshwater ecosystems in high-mountain regions are subject to emerging threats such as global warming and expanding human activities. Stream diatoms and macroinvertebrates form an essential component of freshwater ecosystems in high-mountain regions. Although these organisms are sensitive to environmental changes, knowledge regarding their elevational diversity patterns remains limited. Opposite aspects (e.g., north vs south; west vs east) usually receive different amounts of solar radiation and precipitation, leading to distinct in-stream characteristics such as discharge, flow regime, and water temperature. Despite the suggested strong influence of aspect on biodiversity patterns in mountains, its effect on stream diatoms and macroinvertebrates has been largely overlooked. The aims of our study were to 1) investigate whether macroinvertebrate and diatom taxon richness follows the same pattern along an elevational gradient; 2) test the effect of aspect on the elevational diversity (i.e., taxon richness and assemblage dissimilarity) patterns of macroinvertebrate and diatom assemblages; and 3) examine the relative importance of elevation, aspect, and the local environment (e.g., in-stream physicochemical variables) in shaping macroinvertebrate and diatom assemblages. We investigated macroinvertebrate and diatom assemblages in six nearly parallel streams (three streams on the east aspect and three on the west) in the Hengduan Mountains region. We found that the taxon richness of both macroinvertebrates and diatoms showed a monotonic increase with elevation (1623-2905 m a.s.l.) when aspect was not accounted for. When aspect was taken into consideration, macroinvertebrate taxon richness still showed a monotonically increasing elevational pattern on both the east and west aspects, but with significantly different model slopes, while a monotonical pattern for diatoms only remained on the west aspect. In addition, taxon richness of macroinvertebrates may also follow a potential unimodal pattern. The distance-decay relationships followed the same patterns as taxon richness, suggesting that the influence of aspect on diatom and macroinvertebrate assemblages was not negligible. Our results suggested that the diversity of both diatoms and macroinvertebrates was jointly determined by elevation, aspect and local environment. Compared to macroinvertebrates, the diatom assemblages were more strongly influenced by the local environment. To gain a better understanding of the underlying mechanisms driving elevational patterns of stream biodiversity in high-mountain regions, comparative studies that involve multiple organisms, streams, and mountains across a large elevational range are needed.

Author：Koenig, WD;Knops, JMH;Carmen, WJ

Abstract:Quantifying masting behavior-the highly variable, yet synchronized, production of seeds by forest trees and other plants-is of considerable importance to ecosystem function and forest management, yet typically requires years of study to acquire. In contrast, measuring radial growth by mean of tree-ring cores potentially yields decades or more of data relatively quickly. Given the widespread existence of a negative correlation between growth and reproduction, can radial growth be used to infer historical masting behavior and detect long-term changes in reproductive behavior? Here we test this hypothesis in five species of California oaks (genus Quercus) for which we have long-term weather and 40 years of acorn production data a Hastings Reservation in central coastal California. Radial growth was measured for the three deciduous species using tree-ring analysis between 1980 and 1994 and for all five species using dendrometers between 1996 and 2019. Success was judged based on four criteria focused on the proportion of variance in annual acorn production explained, whether values using radial growth predicted very large and very small crop years, and whether five basic metrics of radial growth quantifying variance, autocorrelation, and synchrony matched values based on acorn production. Of the criteria, none was ma using tree-rings with the exception of one of the metrics (mean pairwise synchrony). Dendrometers performed better but still failed two of the four criteria entirely and only ma the other two for at most three of the five species. We conclude that radial growth does a generally poor job of estimating historical acorn production in these oaks. Although future advances may help resolve these shortcomings, demonstration that the relationship between radial growth and masting meet appropriate criteria based on years of overlapping data is currently necessary prior to any use of tree-ring growth to infer masting patterns.

Author：Zhang, XK;Qin, BQ;Deng, JM;Wells, M

Abstract:The authors regret that we incorrectly identified the wild type in the paper. In the methods, the first sentence of the passage in section 2.1 should read In this research, Escherichia coli strain zntA, which has the capacity to emit a dose-dependent bioluminescence in response to available Pb (Riether et al., 2001), was used for Pb bioavailability evaluation. The subsequent mentions of the wild type Cupriavidus metallidurans should be Escherichia coli. The authors would like to apologise for any inconvenience caused. © 2019 Elsevier Ltd

Author：Liang, JH;Chen, Z

Abstract:Arsenic (As) polluted groundwater in Northern China was used as drinking water source and caused severe health problems. Characterization of As speciation is crucial to understand the health risk of As and its biogeochemical behaviors in groundwater. In this study, groundwater samples were collected from 26 wells in Northern China. Arsenic species in the groundwater were measured by high-performance liquid chromatography (HPLC) and inductively coupled plasma mass spectrometry (ICP-MS). Thioarsenate, one of the As species that is seldom reported in drinking groundwater, was detected in two-third of the sampling wells, even in the samples with total As concentration lower than 10 mu g.L-1. Furthermore, the occurrence of thioarsenate in groundwater samples was dependent on the pH of groundwater, and thioarsenate was transformed to arsenite below a pH value of 8.2. The study demonstrated thioarsenate was prevalent in the alkaline drinking groundwater and would be a new As exposure pathway for the people and livestock living in the As-rich area.

Author：Zhu Yi;Sun Guoxin;Chen Zheng;Hu Ying;Zheng Ruilun

Abstract:The impacts of boron ( B) root application and foliar spray on arsenic ( As) uptake,translocation,and efflux by /in rice seedlings ( Oryza sativa L. ) were investigated in three hydroponic experiments. The addition of B to culture medium did not alter concentrations of arsenite ( As[Ⅲ]) ,arsenate ( As[Ⅴ]) ,and total As,nor did it alter transfer coefficients or uptake efficiency of As in rice seedlings under either As( Ⅲ) or As( Ⅴ) exposure. Foliar B supply increased shoot B concentrations 15. 8-fold,and decreased root As concentrations and As uptake efficiency by 20. 9%% and 18. 0%% under As( Ⅴ) treatment,and by 12. 6%% and 13. 8%% under As( Ⅲ) treatment,respectively,yet did not significantly decrease shoot As concentrations ( P > 0. 05) . Interestingly,foliar B supply reduced root B concentrations by up to 47. 1%% under exposure to As( Ⅴ) but not As( Ⅲ) ,and corresponding root B concentrations were 85. 3%% higher in As( Ⅴ) treatment than in As( Ⅲ) treatment on average ( P < 0. 05) . Both total As and As( Ⅴ) concentrations were positively related to B concentration in rice roots under As( Ⅴ) treatment following foliar B supply ( P < 0. 05) . Rice seedlings extruded 105. 2%% more As after As( Ⅲ) -pretreatment than after As( Ⅴ) -pretreatment. Foliar B supply increased the amount of As excreted by As( Ⅲ) -pretreated rice root by 14. 0%%-16. 9%% ( P > 0. 05) ,and had no effect on the As efflux of As( Ⅴ) -pretreatment seedlings. A range of 45. 9%%-70. 7%% of root As was excreted to solution during one week. These results indicate that the root application of B at four times the concentration of As can slightly decrease As accumulation by rice,whereas foliar B supply is conducive to a decline in As acquisition by rice roots. It is likely that the B channel is at least not the main pathway for As( Ⅲ) entering into rice roots,and the As( Ⅴ) distribution mechanism in rice plants may be shared with that of B.