38 results on '"Xing, Guan"'
Search Results
2. Arsenic and selenium in the plant-soil-human ecosystem: CREST publications during 2018–2021
- Author
-
Zhi-Hua Dai, Dong-Xing Guan, Lena Q. Ma, and Hong-Jie Sun
- Subjects
Human ecosystem ,Environmental Engineering ,chemistry ,Environmental chemistry ,chemistry.chemical_element ,Environmental science ,Plant soil ,Crest ,Pollution ,Waste Management and Disposal ,Selenium ,Arsenic ,Water Science and Technology - Published
- 2021
3. Selenium Increased Arsenic Accumulation by Upregulating the Expression of Genes Responsible for Arsenic Reduction, Translocation, and Sequestration in Arsenic Hyperaccumulator
- Author
-
Zhi-Hua Dai, You-Jing Peng, Song Ding, Jia-Yi Chen, Si-Xue He, Chun-Yan Hu, Yue Cao, Dong-Xing Guan, and Lena Q. Ma
- Subjects
Arsenate Reductases ,Arsenites ,Pteris ,General Chemistry ,Selenic Acid ,Plant Roots ,Antiporters ,Arsenic ,Selenium ,Soil ,Biodegradation, Environmental ,Environmental Chemistry ,Arsenates ,Soil Pollutants - Abstract
Selenate enhances arsenic (As) accumulation in As-hyperaccumulator
- Published
- 2022
4. Nrf2/Keap1 pathway in countering arsenic-induced oxidative stress in mice after chronic exposure at environmentally-relevant concentrations
- Author
-
Hong-Jie Sun, Song Ding, Dong-Xing Guan, and Lena Q. Ma
- Subjects
Environmental Engineering ,Kelch-Like ECH-Associated Protein 1 ,NF-E2-Related Factor 2 ,Health, Toxicology and Mutagenesis ,Drinking Water ,Public Health, Environmental and Occupational Health ,General Medicine ,General Chemistry ,Pollution ,Arsenic ,Mice ,Oxidative Stress ,Environmental Chemistry ,Animals ,RNA, Messenger ,Signal Transduction - Abstract
Contamination of drinking water by carcinogen arsenic (As) is of worldwide concern as its exposure poses potential threat to human health. As such, it is important to understand the mechanisms associated with As-induced toxicity to humans. The Nrf2/Keap1 signal pathway is one of the most important defense mechanisms in cells to counter oxidative stress; however, limited information is available regarding its role in countering As-induced stress in model animal mouse. In this study, we assessed the responses of Nrf2/keap1 pathway in mice after chronic exposure to As at environmentally-relevant concentrations of 10-200 μg L
- Published
- 2022
5. Arsenic contents, speciation and bioaccessibility in rice grains from China: Regional and variety differences
- Author
-
Jia-Yi Chen, Jing-Yu Zeng, Song Ding, Jie Li, Xue Liu, Dong-Xing Guan, and Lena Q. Ma
- Subjects
China ,Environmental Engineering ,Asia ,Health, Toxicology and Mutagenesis ,Environmental Chemistry ,Humans ,Oryza ,Plant Structures ,Pollution ,Waste Management and Disposal ,Arsenic - Abstract
As the staple food for Asian countries and with its ability in arsenic accumulation, rice consumption becomes a dominant pathway for As exposure to humans. Here, we collected 108 rice samples from local markets and online sources in 13 major rice-producing regions in China, and determined As contents, speciation and bioaccessibility in the samples. Total As contents were 25-327 μg kg
- Published
- 2022
6. Application of diffusive gradients in thin-films technique for speciation, bioavailability, modeling and mapping of nutrients and contaminants in soils
- Author
-
Gang Li, Lena Q. Ma, H. Henry Teng, Si-Xue He, and Dong-Xing Guan
- Subjects
Biogeochemical cycle ,Environmental Engineering ,0208 environmental biotechnology ,02 engineering and technology ,010501 environmental sciences ,Contamination ,complex mixtures ,01 natural sciences ,Pollution ,Diffusive gradients in thin films ,020801 environmental engineering ,Bioavailability ,Nutrient ,Environmental chemistry ,Genetic algorithm ,Soil water ,Environmental science ,Waste Management and Disposal ,0105 earth and related environmental sciences ,Water Science and Technology - Abstract
Soil plays an important role in controlling the biogeochemical cycling of nutrients and contaminants in the environment. Reliable analytical techniques are critical to better understand their trans...
- Published
- 2021
7. Probability of Cultivating Se-Rich Maize in Se-Poor Farmland Based on Intensive Field Sampling and Artificial Neural Network Modelling
- Author
-
Xudong Ma, Zhongfang Yang, Tao Yu, and Dong-Xing Guan
- Subjects
China ,History ,Farms ,Environmental Engineering ,Polymers and Plastics ,Health, Toxicology and Mutagenesis ,Public Health, Environmental and Occupational Health ,Phosphorus ,General Medicine ,General Chemistry ,Zea mays ,Pollution ,Industrial and Manufacturing Engineering ,Selenium ,Soil ,Humans ,Soil Pollutants ,Environmental Chemistry ,Micronutrients ,Neural Networks, Computer ,Business and International Management ,Probability - Abstract
Selenium (Se) is a necessary micronutrient for humans, and its supplementation from crop grains is important to address the ubiquitous Se deficiency in people worldwide. Se uptake by crops largely depend on soil bioavailable Se rather than soil total Se content, which provides possibilities to explore the Se-rich crops in Se-poor area. Here, the possibility of cultivating Se-rich maize grains in Se-poor farmland was tested based on intensive field sampling and mathematical modelling. Sampling was conducted at county scale, and a total of 7779 topsoil samples and 109 maize samples with paired rhizosphere soils samples were collected. Results showed that although the soil Se content in the study county from southwestern China was at a low level (0.01-2.75 mg kg
- Published
- 2022
8. Amine- and thiol-bifunctionalized mesoporous silica material for immobilization of Pb and Cd: Characterization, efficiency, and mechanism
- Author
-
Xue Liu, Jing-Wei Fu, Lena Q. Ma, Shi Xinyao, Ni Tang, Meng-Ru Jia, and Dong-Xing Guan
- Subjects
Environmental Engineering ,Sorbent ,Chemistry ,Health, Toxicology and Mutagenesis ,Public Health, Environmental and Occupational Health ,Sorption ,General Medicine ,General Chemistry ,Mesoporous silica ,Silicon Dioxide ,Pollution ,Chemical reaction ,X-ray photoelectron spectroscopy ,Lead ,Environmental Chemistry ,Amine gas treating ,Adsorption ,Sulfhydryl Compounds ,Fourier transform infrared spectroscopy ,Amines ,Mesoporous material ,Nuclear chemistry ,Cadmium - Abstract
In this study, a two-step functionalizing strategy by combining co-condensation with grafting procedures was employed to synthesize well-ordered Amino- and Thiol-Bifunctionalized SBA-15 (ATBS) mesoporous silica. Its physicochemical properties, performance, and mechanisms in immobilization of toxic metals Pb and Cd in water and soil were investigated. After bi-functionalization, X-ray diffractometer, transmission electron microscope, and N2 adsorption-desorption measurements confirmed that the ATBS maintained a highly-ordered mesoporous structure, large surface area and pore volume. The elemental analysis, Fourier transform infrared spectroscopy and X-ray Photoelectron Spectroscopy (XPS) evidenced the successful incorporation of amine and thiol groups into ATBS. These structure and functional characteristics of ATBS benefited Pb and Cd sorption. Sorption isotherms of Pb and Cd were better fit with Sips and Redlich-Peterson models. Sorption kinetics suggested that Pb sorption was mainly regulated by chemical reactions, whereas both diffusion process and chemical reactions were rate-regulating steps in Cd sorption. ATBS showed the maximum sorption capacities for Pb and Cd at 120 and 38 mg g-1, respectively. The sorption mechanisms revealed by XPS measurements suggested that Cd sorption was mainly attributed to thiol groups while Pb was efficiently bond to both thiol and amino groups. High and stable sorption efficiencies were attained in the pH range of 4-6, with a higher affinity towards Pb than Cd. Furthermore, its ability to immobilize Pb and Cd in soils was examined with an incubation experiment, which showed that ATBS reduced 30-56% of MgCl2-extractable Pb and Cd in a contaminated soil. The synthesized sorbent via the two-step functionalizing strategy shows high sorption efficiency towards Pb and Cd, and thus it has potential application in remediating Pb and Cd contaminated water and soils.
- Published
- 2021
9. Selenate increased plant growth and arsenic uptake in As-hyperaccumulator Pteris vittata via glutathione-enhanced arsenic reduction and translocation
- Author
-
Yue Cao, Xue Liu, Ran Han, Shuxin Tu, Song Ding, Zhihua Dai, Dong-Xing Guan, Jia-Yi Chen, and Lena Q. Ma
- Subjects
Environmental Engineering ,Health, Toxicology and Mutagenesis ,Glutathione reductase ,chemistry.chemical_element ,Selenic Acid ,Selenate ,Plant Roots ,Arsenic ,chemistry.chemical_compound ,Botany ,Environmental Chemistry ,Soil Pollutants ,Hyperaccumulator ,Waste Management and Disposal ,chemistry.chemical_classification ,biology ,Glutathione peroxidase ,Arsenate ,Pteris ,Glutathione ,biology.organism_classification ,Pollution ,Biodegradation, Environmental ,chemistry ,Pteris vittata ,Selenium - Abstract
The beneficial effects of selenium on As uptake and plant growth in As-hyperaccumulator Pteris vittata are known, but the associated mechanisms remain unclear. Here, we investigated the effects of selenate on arsenic accumulation by P. vittata under two arsenate levels. P. vittata plants were exposed to 13 (As13) or 133 µM (As133) arsenate and 5 µM selenate in 0.2-strength Hoagland solution. After 14 d of growth, plant biomass, Se and As content, As speciation, and malondialdehyde (MDA), glutathione reductase (GR), glutathione peroxidase (GPX), and glutathione (GSH and GSSG) levels were determined. The results show that selenate promoted P. vittata growth and increased As concentrations in the roots and fronds by 256% from 97 to 346 mg kg−1 and 142% from 213 to 514 mg kg−1 under As13 treatment, and by 166% from 500 to 1332 mg kg−1 and 534% from 777 to 4928 mg kg−1 under As133 treatment. In addition, selenate increased the glutathione content in P. vittata roots and fronds by 75–86% under As13 treatment and 44–45% under As133 treatment. Selenate also increased the GPX activity by 161–173%, and GR activity by 72–79% in P. vittata under As13 and As133 treatments. The HPLC-ICP-MS analysis indicated that selenate increased both AsIII and AsV levels in P. vittata, with AsIII/AsV ratio being lower in the roots and higher in the fronds, i.e., more AsIII was being translocated to the fronds. Taken together, our results suggest that, via GPX-GR mediated enhancement of GSH-GSSG cycle, selenate effectively increases plant growth and As uptake in P. vittata by improving AsV reduction in the roots and AsIII translocation from the roots to the fronds.
- Published
- 2021
10. Geographical distribution of As-hyperaccumulator Pteris vittata in China: Environmental factors and climate changes
- Author
-
Shuang Yan, Wumei Xu, Yue Cao, Dong-Xing Guan, Lena Q. Ma, Qinglian Du, and Xue Liu
- Subjects
China ,Environmental Engineering ,biology ,Range (biology) ,business.industry ,Ecology ,Climate Change ,Species distribution ,Climate change ,Distribution (economics) ,Pteris ,biology.organism_classification ,Pollution ,Arsenic ,Phytoremediation ,Biodegradation, Environmental ,Pteris vittata ,Environmental Chemistry ,Environmental science ,Soil Pollutants ,Hyperaccumulator ,Precipitation ,business ,Waste Management and Disposal - Abstract
Understanding the distribution of hyperaccumulators helps to implement more efficient phytoremediation strategies of contaminated sites, however, limited information is available. Here, we investigated the geographical distribution of the first-known arsenic-hyperaccumulator Pteris vittata in China and the key factors under two climate change scenarios (SSP 1-2.6 and SSP 5-8.5) at two time points (2030 and 2070). Species distribution model (MaxEnt) was applied to examine P. vittata distribution based on 399 samples from field surveys and existing specimen records. Further, among 23 environmental factors, 11 variables were used in the MaxEnt model, including temperature, precipitation, elevation, soil property, and UV-B radiation. The results show that P. vittata can grow in ~23% of the regions in China. Specifically, it is mainly distributed in 11 provinces of southern China, including Hainan, Guangdong, Guangxi, Yunnan, Guizhou, Hunan, Hubei, Jiangxi, Fujian, Zhejiang, and Jiangsu. Besides, eastern Sichuan, and southern Henan, Shaanxi, and Anhui are suitable for P. vittata growth. Under two climate change scenarios, P. vittata distribution in China would decrease by ~5.76-7.46 × 104 km2 in 2030 and ~3.22-4.68 × 104 km2 in 2070, with southern Henan and most Jiangsu being unsuitable for P. vittata growth. Among the 11 environmental variables, the minimum temperature of coldest month (bio6) and temperature annual range (bio7) are the two key factors limiting P. vittata distribution. At bio6 33 °C, the regions are unsuitable for P. vittata growth. Based on the MaxEnt model, precipitation had limited effects, so P. vittata can probably survive under both dry and moist environments. This study helps guide phytoremediation of As-polluted soils using P. vittata and provides an example to evaluate habitat suitability of hyperaccumulators at international scales.
- Published
- 2021
11. Decomplexation of Cr(III)-EDTA and simultaneous abatement of total Cr by photo-oxidation: efficiency and in situ reduction of intermediate Cr(VI)
- Author
-
Zhao Min, Bei Ke, Qi Wang, Jin Zhan, Dong-Xing Guan, Zhang Yejian, Xiangyong Zheng, Huabin Zhou, Huang Xianfeng, and Xiran Wang
- Subjects
Chromium ,Ultraviolet Rays ,Decarboxylation ,Health, Toxicology and Mutagenesis ,Radical ,chemistry.chemical_element ,Wastewater ,010501 environmental sciences ,01 natural sciences ,Mineralization (biology) ,Spectroscopy, Fourier Transform Infrared ,Environmental Chemistry ,Irradiation ,Effluent ,Edetic Acid ,0105 earth and related environmental sciences ,Chemistry ,Advanced oxidation process ,General Medicine ,Photochemical Processes ,Electroplating ,Pollution ,Models, Chemical ,Degradation (geology) ,Oxidation-Reduction ,Water Pollutants, Chemical ,Nuclear chemistry - Abstract
Most prevailing processes are incapable of removing Cr(III)-organic complexes efficiently and facing the problem of in-process formation of highly toxic Cr(VI) based on oxidation. The efficient decomplexation of Cr(III) complexes and simultaneous abatement of Cr with low Cr(VI) accumulation would be desirable in treatment of Cr(III)-complexed wastewater. Here, we found efficient degradation of Cr(III)-EDTA and simultaneous removal of Cr by forming Cr2O3 precipitate from simulated solution as well as an electroplating effluent under UV irradiation. The results showed a complete degradation of Cr(III)-EDTA after reaction time of 60 min and 70–80% of TOC mineralization within 180 min as well. About 90% of Cr(III) precipitated as Cr2O3 simultaneously, with the residual total Cr below 1.5 mg/L. The degradation of Cr(III)-EDTA was a stepwise de-acetate group process, as proven by the obvious attenuation of peaks related to carboxyl groups and C–C bond from FT-IR spectra of Cr(III)-EDTA and significant mineralization of TOC after UV irradiation. Based on negligible accumulation of Cr(VI) (less than 0.1 mg/L) under N2-sparged condition, the C-centered radicals from the β-fragmentation of O-centered radicals formed by photo-induced ligand-to-metal charge transfer were responsible for the in situ reduction of intermediate Cr(VI), resulting in the low accumulation of Cr(VI). The addition of 20 mg/L Fe2+ was capable of removing the remaining Cr(VI) and total Cr, with Cr(VI) and total Cr less than 0.1 and 1.0 mg/L, respectively. Moreover, the photo-oxidation process combined with Fe2+ addition were efficient in removing other Cr(III) complexes, such as Cr(III)-citrate and those from a realistic electroplating effluent. We believe that this study would provide an alternative option for efficient degradation of Cr(III) complexes and simultaneous abatement of Cr from contaminated water.
- Published
- 2019
12. Improved adsorption properties of tetracycline on KOH/KMnO4 modified biochar derived from wheat straw
- Author
-
Jin Xu, Yin Zhang, Bin Li, Shisuo Fan, Huacheng Xu, and Dong-Xing Guan
- Subjects
Environmental Engineering ,Health, Toxicology and Mutagenesis ,Public Health, Environmental and Occupational Health ,Environmental Chemistry ,General Medicine ,General Chemistry ,Pollution - Published
- 2022
13. Correlative Distribution of DOM and Heavy Metals in the Soils of a Typical Peri-Urban Critical Zone
- Author
-
Azeem Muhammad, Gang Li, Zhe Wang, Ruixia Han, Eric Fru Zama, and Dong-Xing Guan
- Subjects
chemistry.chemical_classification ,History ,Biogeochemical cycle ,Watershed ,Polymers and Plastics ,Soil test ,complex mixtures ,Industrial and Manufacturing Engineering ,Humus ,chemistry ,Environmental chemistry ,Soil water ,Dissolved organic carbon ,Environmental science ,Organic matter ,Ecosystem ,Business and International Management - Abstract
In peri-urban critical zones, soil ecosystems are highly affected by increasing urbanization, causing probably an intense interaction between dissolved organic matter (DOM) and heavy metals in soil. Such interaction is critical for understanding the biogeochemical cycles of both organic matter and heavy metals in these zones. However, limited research has reported the correlative distribution of DOM and heavy metals at high seasonal and spatial resolutions in peri-urban critical zones. In this study, 160 soil samples were collected from the farmland and forestland of Zhangxi watershed, in Ningbo, eastern China during spring, summer, fall and winter four seasons. UV-visible absorption and fluorescent spectroscopy were used to explore the optical characteristics of DOM. The results indicated a mixture of exogenous and autogenous sources of DOM in the Zhangxi watershed, while DOM in farmland exhibited a higher degree of aromaticity and humification than that in forestland. Fluorescent results showed that humic acid-like, fulvic acid-like and microbial-derived humic-like fractions were mostly affected by seasons. The distribution of heavy metals was affected mainly by land-use changes and seasons. Correlation analysis between heavy metals and DOM characteristics and components suggested that aromatic and humic substances were more favorable in binding with EDTA extractable Ni, Cu, Zn and Cd. The bioavailable Cd and Pb decreased due to binding with humic fractions, indicating that DOM had great effects on the heavy metal bioavailability. Overall, these findings provide an insight into the correlative distributions of DOM and heavy metals in peri-urban areas, thereby highlighting their biogeochemical cycling in the soil environment.
- Published
- 2021
14. Localized intensification of arsenic release within the emergent rice rhizosphere
- Author
-
Yue Gao, Hao Zhang, Dong-Xing Guan, Jun Luo, Fang-Jie Zhao, Daixia Yin, Lena Q. Ma, Wen Fang, Eduardo Moreno-Jiménez, Paul N. Williams, UAM. Departamento de Química Agrícola, Chemistry, and Analytical, Environmental & Geo-Chemistry
- Subjects
chemistry.chemical_element ,010501 environmental sciences ,Spatial distribution ,01 natural sciences ,Oxygen ,Arsenic ,Soil ,Nutrient ,Flux (metallurgy) ,Soil Pollutants ,Environmental Chemistry ,0105 earth and related environmental sciences ,Rhizosphere ,Phosphorus ,Oryza ,General Chemistry ,Transition metals ,Química ,Elements ,Medio Ambiente ,chemistry ,Fluxes ,Environmental chemistry ,Soil water ,Soils ,Plant derived food - Abstract
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Environmental Science & Technology, © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see: https://pubs.acs.org/doi/full/10.1021/acs.est.9b04819, Behavior of trace elements in flooded/lowland rice soils is controlled by root-zone iron oxidation. Insoluble iron species bind/capture toxic elements, i.e., arsenic. However, it was recently observed that within this territory of arsenic immobilization lies a zone of prolific iron release, accompanied by a significant flux of arsenic in close proximity to rice root apices. Questions still remain on how common this phenomenon is and whether the chemical imaging approaches or soils/cultivars used influence this event. Here, three types of ultrathin/high-resolution diffusive gradient in thin films (DGT) substrates were integrated with oxygen planar optodes in a multilayer system, providing two-dimensional mapping of solute fluxes. The three DGT approaches revealed a consistent/overlapping spatial distribution with localized flux maxima for arsenic, which occurred in all experiments, concomitant with iron mobilization. Soil/porewater microsampling within the rhizosphere revealed no significant elevation in the solid phase’s total iron and arsenic concentrations between aerobic and anaerobic zones. Contrary to arsenic, phosphorus bioavailability was shown to decrease in the arsenic/iron flux maxima. Rice roots, in addition to their role in nutrient acquisition, also perform a key sensory function. Flux maxima represent a significant departure from the chemical conditions of the bulk/field environment, but our observations of a complete rhizosphere reveal a mixed mode of root–soil interactions, This work was funded by the National Natural Science Foundation of China (No. 41771271), the Fundamental Research Funds for the Central Universities (021114380126), the National Natural Science Foundation of China (No. 41807023), and the Jiangsu Province Natural Science Foundation (BK20180344). The study also received support from the Newton Fund/Royal Society and NFSC (R1504GFS and 21511130063)
- Published
- 2020
15. Total and available metal concentrations in soils from six long-term fertilization sites across China
- Author
-
Guanghui Yu, Fu-Sheng Sun, Yun-Gen Liu, Dong-Xing Guan, and Matthew L. Polizzotto
- Subjects
Crops, Agricultural ,China ,Nitrogen ,Health, Toxicology and Mutagenesis ,chemistry.chemical_element ,010501 environmental sciences ,01 natural sciences ,Soil ,Human fertilization ,Metals, Heavy ,Soil pH ,Animals ,Soil Pollutants ,Environmental Chemistry ,Fertilizers ,0105 earth and related environmental sciences ,Cadmium ,Phosphorus ,Agriculture ,04 agricultural and veterinary sciences ,General Medicine ,Pollution ,Diffusive gradients in thin films ,Soil contamination ,Manure ,Zinc ,chemistry ,Environmental chemistry ,Soil water ,Potassium ,040103 agronomy & agriculture ,0401 agriculture, forestry, and fisheries ,Environmental Pollution ,Copper ,Environmental Monitoring - Abstract
Approximately 19% of agricultural soils in China are contaminated by heavy metals. However, the effects of agricultural management practices on soil contamination are not well understood. Taking advantage of six long-term (23-34 years) field sites across China, this study examined the effects of different agricultural fertilization treatments, including control (no fertilization), inorganic nitrogen, phosphorus and potassium fertilization (NPK), manure fertilization (M), and NPK plus manure fertilization (NPKM), on the total and available metal concentrations in soils. The results showed that after 23-34 years of fertilization, the M and NPKM treatments significantly increased the total concentration of cadmium (Cd), copper (Cu), and zinc (Zn) in soils compared with the concentrations measured for the control and NPK treatments. In contrast, the fertilization treatments had almost no influence on soil lead (Pb) and nickel (Ni) concentrations. The results of analysis via diffusive gradients in thin films demonstrated that long-term sheep or cattle manure fertilization increased the available metals, especially Cd, Cu, and Zn, but long-term swine manure application decreased the available metals, except for Cu and Zn, in soils. Further analysis revealed that the manure source, soil pH level, and biogeochemical properties of metals affected the availability of Cd, Cu, Pb, Zn, and Ni in soils. Collectively, organic fertilizers had the potential to reduce metal uptake by crops, but caution should be taken to reduce metal concentrations in manure.
- Published
- 2018
16. DGT technique to assess P mobilization from greenhouse vegetable soils in China: A novel approach
- Author
-
Yusef Kianpoor Kalkhajeh, Helle Sørensen, Peter E. Holm, Hans Christian Bruun Hansen, Biao Huang, Jun Luo, Dong-Xing Guan, and Wenyou Hu
- Subjects
Topsoil ,Environmental Engineering ,Chemistry ,Greenhouse ,Soil classification ,04 agricultural and veterinary sciences ,010501 environmental sciences ,Soil type ,01 natural sciences ,Pollution ,Environmental chemistry ,Soil water ,040103 agronomy & agriculture ,0401 agriculture, forestry, and fisheries ,Environmental Chemistry ,Soil properties ,Leaching (agriculture) ,Eutrophication ,Waste Management and Disposal ,0105 earth and related environmental sciences - Abstract
Intensive phosphorus (P) inputs to plastic-covered greenhouse vegetable production (PGVP) in China has led to excessive soil P accumulation increasing the potential for leaching to surface waters. This study examined the mobility and hence the potential risk of P losses through correlations between soil solution P (PSol) and soil extractable P as determined by conventional soil P test methods (STPs) including degree of P saturations (DPSs), and diffusive gradient in thin-films (DGT P) technique. A total of 75 topsoil samples were chosen from five representative Chinese PGVPs covering a wide range of physiochemical soil properties and cultivation history. Total P and Olsen P contents varied from 260 to 4900, and 5 to 740mgkg-1, respectively, while PSol concentrations were between 0.01 and 10.8mgL-1 reflecting the large differences in vegetation history, fertilization schemes, and soil types. Overall, DGT P provided the best correlation with PSol (r2=0.97) demonstrating that DGT P is a versatile measure of P mobility regardless of soil type. Among the DPSs tested, oxalate extractable Al (DPSOx-Al) had the best correlation with PSol (r2=0.87). In the STP versus PSol relationships, STP break-points above which P mobilization increases steeply were 513μgL-1 and 190mgkg-1 for DGT P or Olsen P, respectively, corresponding to PSol concentration of 0.88mgL-1. However, for PSol concentration of 0.1mgL-1 that initiates eutrophication, the corresponding DGT P and Olsen P values were 27μgL-1 and 22mgkg-1, respectively. Over 80% of the investigated soils had DGT P and Olsen P above these values, and thus are at risk of P mobilization threatening receiving waters by eutrophication. This paper demonstrates that the DGT extracted P is a powerful measure for soluble P and hence for assessment of P mobility from a broad range of soil types.
- Published
- 2018
17. Effect of phosphate minerals on phytoremediation of arsenic contaminated groundwater using an arsenic-hyperaccumulator
- Author
-
Jorge A.G. Santos, Guang-Mei Yang, Yanshan Chen, Dong-Xing Guan, Gang Li, and Ling-Jia Zhu
- Subjects
021110 strategic, defence & security studies ,integumentary system ,biology ,Chemistry ,Ammonium phosphate ,Phosphorus ,0211 other engineering and technologies ,Environmental engineering ,Soil Science ,chemistry.chemical_element ,02 engineering and technology ,Plant Science ,010501 environmental sciences ,biology.organism_classification ,Phosphate ,01 natural sciences ,Phytoremediation ,chemistry.chemical_compound ,Phosphorite ,Environmental chemistry ,Pteris vittata ,Arsenic ,0105 earth and related environmental sciences ,General Environmental Science ,Hoagland solution - Abstract
To investigate the effect of phosphate sources on phytoremediation of arsenic (As) contaminated groundwater using Pteris vittata, a hydroponic experiment was conducted. Sparingly-soluble phosphate minerals (phosphate rock, PR, and hydroxyapatite, HA) and soluble Hoagland solution (HS, containing ammonium phosphate) were chosen as phosphate sources. Arsenic content in the residual nutrient solutions was analyzed to acquire the phytoextraction effect. The results showed that As concentrations in the nutrient solutions treated with sparingly-soluble P decreased more rapidly than that treated with soluble P. For treatment with sparingly-soluble PR, P. vittata reduced As concentration more rapidly than that in HA treatment and HS control. Nitrate and P concentrations in the residual solutions were also monitored to check eutrophication pollution. Phosphorus in the residual solutions in PR or HA treatment was not detected and 0.5 μ g L−1, respectively, much lower than HS control. These results indicated that sparingly-soluble PR could be an ideal P source to facilitate As removal from contaminated groundwater by P. vittata and ensure the nutrient quality of the residual water after phytoremediation.
- Published
- 2017
18. A diffusive gradients in thin-films technique for the assessment of bisphenols desorption from soils
- Author
-
William Davison, Dong-Xing Guan, Hao Zhang, Jun Luo, Jian-Lun Zheng, and Lena Q. Ma
- Subjects
Environmental Engineering ,010504 meteorology & atmospheric sciences ,Chemistry ,Health, Toxicology and Mutagenesis ,Kinetics ,Analytical chemistry ,010501 environmental sciences ,01 natural sciences ,Pollution ,Diffusive gradients in thin films ,Solution phase ,Partition coefficient ,Adsorption ,Environmental chemistry ,Desorption ,Soil water ,Environmental Chemistry ,Partition (number theory) ,Waste Management and Disposal ,0105 earth and related environmental sciences - Abstract
Desorption/adsorption of bisphenols (BPs) in soils affects their mobility and availability. However, the kinetics of these processes have not been well studied, due to the lack of appropriate means of measurement. Diffusive gradients in thin-films (DGT) technique can assess kinetic processes in soils and have recently been developed for measuring three BPs (BPA, BPB and BPF). DGT was deployed for 2.5 h to 20 d in five soils with different soil properties. Non-linear increase in mass accumulation by DGT with time indicated poor resupply of BPs from soil solid to solution phase. By fitting the data with DIFS (DGT-induced fluxes in soils) model, values for the labile partition coefficient (Kdl), response time (tc) and rates of exchange (k1 and k-1) of BPs between soil solid and solution phases were obtained. The derived values of Kdl showed that most of the BPs in the soil could participate in labile exchange. Average response times of 1–2 h implied that the supply of BPs to DGT was limited by their desorption rate. Soils with more binding sites (higher DOM, CEC and Fe oxides) could resupply BPs more quickly, highlighting the danger of just considering partition effects.
- Published
- 2017
19. Exploring the interactions and binding sites between Cd and functional groups in soil using two-dimensional correlation spectroscopy and synchrotron radiation based spectromicroscopies
- Author
-
Fu-Sheng Sun, Qirong Shen, Dong-Xing Guan, Matthew L. Polizzotto, Jun Wu, Boren Wang, Wei Ran, and Guanghui Yu
- Subjects
Cadmium ,Environmental Engineering ,010504 meteorology & atmospheric sciences ,Health, Toxicology and Mutagenesis ,Synchrotron radiation ,chemistry.chemical_element ,Heavy metals ,010501 environmental sciences ,01 natural sciences ,Pollution ,Human fertilization ,chemistry ,Environmental chemistry ,Micro-X-ray fluorescence ,Soil water ,Environmental Chemistry ,Binding site ,Waste Management and Disposal ,Two-dimensional nuclear magnetic resonance spectroscopy ,0105 earth and related environmental sciences - Abstract
Understanding how heavy metals bind and interact in soils is essential for predicting their distributions, reactions and fates in the environment. Here we propose a novel strategy, i.e., combining two-dimensional correlation spectroscopy (2D COS) and synchrotron radiation based spectromicroscopies, for identifying heavy metal binding to functional groups in soils. The results showed that although long-term (23 yrs) organic fertilization treatment caused the accumulation of Cd (over 3 times) in soils when compared to no fertilization and chemical fertilization treatments, it significantly (p0.05) reduced the Cd concentration in wheat grain. The 2D COS analyses demonstrated that soil functional groups controlling Cd binding were modified by fertilization treatments, providing implications for the reduced bioavailability of heavy metals in organic fertilized soils. Furthermore, correlative micro X-ray fluorescence spectromicroscopy, electron probe micro-analyzer mapping, and synchrotron-radiation-based FTIR spectromicroscopy analysis showed that Cd, minerals, and organic functional groups were heterogeneously distributed at the micro-scale in soil colloids. Only minerals, rather than organic groups, had a similar distribution pattern with Cd. Together, this strategy has a potential to explore the interactions and binding sites among heavy metals, minerals and organic components in soil.
- Published
- 2017
20. Evaluation of various approaches to predict cadmium bioavailability to rice grown in soils with high geochemical background in the karst region, Southwestern China
- Author
-
Chao Guo, Zhongfang Yang, Yinxian Song, Yubo Wen, Xiaoxiong Zhuo, Dong-Xing Guan, Junfeng Ji, and Wei Li
- Subjects
China ,Food Safety ,010504 meteorology & atmospheric sciences ,Health, Toxicology and Mutagenesis ,chemistry.chemical_element ,Biological Availability ,010501 environmental sciences ,Toxicology ,complex mixtures ,01 natural sciences ,Crop ,Soil ,Soil pH ,Humans ,Soil Pollutants ,0105 earth and related environmental sciences ,Cadmium ,Oryza sativa ,food and beverages ,Soil classification ,Oryza ,General Medicine ,Pollution ,Diffusive gradients in thin films ,Bioavailability ,chemistry ,Environmental chemistry ,Soil water - Abstract
Evaluating the bioavailability of Cd to rice (Oryza sativa L.) was essential in the karst region, Southwestern China, where the soils have previously been shown to be anomalously enriched in Cd through geogenic processes. In this research, we examined the bioavailability of Cd to rice samples collected from 278 sites in Guangxi province, where rice is the most widely cultivated cereal crop that is responsible for the largest human dietary exposure to Cd. Both soil chemical extraction and soil-plant transfer modelling approaches were used to predict the bioavailability to rice. Some of the soil types were highly enriched in Cd, but their bioavailability was low, since the soil carbonates raised soil pH and remarkably reduced Cd bioavailability. In contrast, acidic soils (Ca was largely leached) with relatively low total Cd, the grown rice plants accumulated higher Cd in their grains. Results from CaCl2 extraction experiments provided good predictions for Cd in rice grain grown in soils of different types. Stepwise multiple regressions revealed soil pH and soil Ca content were the dominant factors that control the transfer of Cd from soil to rice. An extended Freundlich-type model and a polynomial surface model provided good prediction for Cd in rice grains. The diffusive gradients in thin films (DGT) technique gave the best estimation of soil Cd bioavailability, whereas water-extracted soil solution Cd provided relatively poor fits. Regional soil threshold that derived using the models, can avoid exceedance of Cd in rice and thereby enable local agricultural practitioners or authorities to develop appropriate management for croplands with high Cd background.
- Published
- 2019
21. Autocatalytic Decomplexation of Cu(II)-EDTA and Simultaneous Removal of Aqueous Cu(II) by UV/Chlorine
- Author
-
Dong-Xing Guan, Xiangyong Zheng, Wang Yi, Huang Xianfeng, Chao Shan, Zhao Min, Bingcai Pan, Li Yubao, and Xuchun Li
- Subjects
Aqueous solution ,Decarboxylation ,Chemistry ,Ultraviolet Rays ,Inorganic chemistry ,Kinetics ,Photodissociation ,chemistry.chemical_element ,Portable water purification ,General Chemistry ,010501 environmental sciences ,Wastewater ,01 natural sciences ,law.invention ,Water Purification ,Autocatalysis ,law ,Chlorine ,Environmental Chemistry ,Electron paramagnetic resonance ,Edetic Acid ,0105 earth and related environmental sciences - Abstract
Traditional processes usually cannot enable efficient water decontamination from toxic heavy metals complexed with organic ligands. Herein, we first reported the removal of Cu(II)-EDTA by a UV/chlorine process, where the Cu(II)-EDTA degradation obeyed autocatalytic two-stage kinetics, and Cu(II) was simultaneously removed as CuO precipitate. The scavenging experiments and EPR analysis indicated that Cl• accounted for the Cu(II)-EDTA degradation at diffusion-controlled rate (∼1010 M-1 s-1). Mechanism study with mass spectrometry evidence of 11 key intermediates revealed that the Cu(II)-EDTA degradation by UV/chlorine was an autocatalytic successive decarboxylation process mediated by the Cu(II)/Cu(I) redox cycle. Under UV irradiation, Cu(I) was generated during the photolysis of the Cl•-attacked complexed Cu(II) via ligand-to-metal charge transfer (LMCT). Both free and organic ligand-complexed Cu(I) could form binary/ternary complexes with ClO-, which were oxidized back to Cu(II) via metal-to-ligand charge transfer (MLCT) with simultaneous production of Cl•, resulting in the autocatalytic effect on Cu(II)-EDTA removal. Effects of chlorine dosage and pH were examined, and the technological practicability was validated with authentic electroplating wastewater and other Cu(II)-organic complexes. This study shed light on a new mechanism of decomplexation by Cl• and broadened the applicability of the promising UV/chlorine process in water treatment.
- Published
- 2019
22. Effect of aging on bioaccessibility of arsenic and lead in soils
- Author
-
Jie Li, Lena Q. Ma, Dong-Xing Guan, Jun Luo, Shuang Liang, and Chun-Yang Zhou
- Subjects
Environmental Engineering ,Health, Toxicology and Mutagenesis ,Natural aging ,Carbonates ,0211 other engineering and technologies ,chemistry.chemical_element ,02 engineering and technology ,010501 environmental sciences ,01 natural sciences ,Arsenic ,Soil ,Soil Pollutants ,Environmental Chemistry ,0105 earth and related environmental sciences ,Intestinal phase ,021110 strategic, defence & security studies ,Chemistry ,Extraction (chemistry) ,Public Health, Environmental and Occupational Health ,General Medicine ,General Chemistry ,Pollution ,Environmental chemistry ,Soil water ,Correlation analysis - Abstract
The effect of aging on the bioaccessibility of As and Pb in three soils spiked with As (40 or 400 mg kg(-1)), Pb (150 or 1500 mg kg(-1)) or As + Pb (40 mg kg(-1) As and 150 mg kg(-1) Pb) were investigated using the physiologically based extraction test (PBET). Prolonged aging in soils resulted in a decrease in As/Pb bioaccessibility, especially within the first month. After 76 weeks, As/Pb bioaccessibility in soils decreased to a stable level, with 48-84% and 8-34% for bioaccessible As and Pb respectively in the intestinal phase, illustrating that As in spiked soils was much more bioaccessible than Pb. Correlation analysis between sequential extraction data and PBET results showed that the non-specifically sorbed As contributed the most to bioaccessible As, while Pb bound with carbonates and exchangeable fractions were the source for bioaccessible Pb. For future work, minerals containing As and/or Pb instead of their soluble salts can be added to uncontaminated soils to better simulate the natural aging processes.
- Published
- 2016
23. Background concentrations of trace metals As, Ba, Cd, Co, Cu, Ni, Pb, Se, and Zn in 214 Florida urban soils: Different cities and land uses
- Author
-
Lena Q. Ma, Xianjin Tang, Peng Gao, Dong-Xing Guan, Min Xu, and Evandro B. da Silva
- Subjects
010504 meteorology & atmospheric sciences ,Environmental remediation ,Health, Toxicology and Mutagenesis ,chemistry.chemical_element ,010501 environmental sciences ,Toxicology ,01 natural sciences ,Soil ,Metals, Heavy ,Soil Pollutants ,Cities ,0105 earth and related environmental sciences ,Cadmium ,Land use ,Background concentrations ,General Medicine ,Pollution ,Soil quality ,Soil contamination ,Zinc ,Lead ,chemistry ,Environmental chemistry ,Soil water ,Florida ,Environmental science ,Urban environment ,Environmental Monitoring - Abstract
Soil contamination in urban environment by trace metals is of public concerns. For better risk assessment, it is important to determine their background concentrations in urban soils. For this study, we determined the background concentrations of 9 trace metals including As, Ba, Cd, Co, Cu, Ni, Pb, Se, and Zn in 214 urban soils in Florida from two large cities (Orlando and Tampa) and 4 small cities (Clay County, Ocala, Pensacola and West Palm Beach). The objectives were to determine: 1) total concentrations of trace metals in urban soils in cities of different size; 2) compare background concentrations to Florida Soil Cleanup Target Levels (FSCTLs); and 3) determine their distribution and variability in urban soils via multivariate statistical analysis. Elemental concentrations in urban soils were variable, with Pb being the highest in 5 cities (165-552 mg kg-1) and Zn being the highest concentration in Tampa (1,000 mg kg-1). Besides, the As and Pb concentrations in some soils exceeded the FSCTL for residential sites at 2.1 mg kg-1 As and 400 mg kg-1 Pb. Among the cities, Clay County and Orlando had the lowest concentrations for most elements, with Cd, Co, and As being the lowest while Ba, Pb and Zn being the highest. Among all values, geometric means were the lowest while 95th percentile was the highest for all metals. Most 95th percentile values were 2-3 folds higher than the GM data, with Pb presenting the greatest difference, being 4 times greater than GM value (58.9 vs. 13.6 mg kg-1). Still they were lower than FSCTL, with As exceeding FSCTL for residential sites at 2.1 mg kg-1. In addition, the linear discriminate analysis showed distinct separation among the cities: Ocala (Ba & Ni) and Pensacola (As & Pb) were distinctly different from each other and from other cities with higher metal concentrations. The large variations among elemental concentrations showed the importance to establish proper background concentrations of trace metals in urban soils.
- Published
- 2020
24. Comparing CaCl2, EDTA and DGT methods to predict Cd and Ni accumulation in rice grains from contaminated soils
- Author
-
Junfeng Ji, Dong-Xing Guan, Wanfu Zhao, H. Henry Teng, Qiang Ma, and Lena Q. Ma
- Subjects
Contaminated soils ,010504 meteorology & atmospheric sciences ,Health, Toxicology and Mutagenesis ,food and beverages ,General Medicine ,010501 environmental sciences ,Toxicology ,Industrial pollution ,complex mixtures ,01 natural sciences ,Pollution ,Soil quality ,Safety guidelines ,Environmental chemistry ,Soil water ,Environmental science ,Paddy soils ,Extraction methods ,0105 earth and related environmental sciences - Abstract
Urbanization and industrialization have elevated metal concentrations in soils. However, systematic investigation on their availability in regional soils under industrial impacts is lacking. In this study, 230 paired soil-rice samples were collected from two areas in Southeast China, with low and high industrial impacts. Classic equilibrium-based CaCl2 and EDTA extraction methods, and dynamic-based diffusive gradients in thin-films (DGT) technique were used to study metal availability in soils, with the results being compared with metal concentrations in soils and rice grains. Generally, Cd, Ni, Cu, Zn, Cr and Pb concentrations in soils exceeded the Chinese Soil Quality Standard (GB15618-2018), whereas only Cd and Ni in some rice grains exceeded the Chinese Safety Guidelines. CaCl2 and EDTA extractions, DGT method and soil total metal concentrations provided good predication of grain Cd (R = 0.51–0.66, p
- Published
- 2020
25. Temporal and spatial distribution of Microcystis biomass and genotype in bloom areas of Lake Taihu
- Author
-
Lena Q. Ma, Xingyu Wang, Pengfu Li, Dong-Xing Guan, Huacheng Xu, and Li Chen
- Subjects
0106 biological sciences ,Chlorophyll a ,Environmental Engineering ,Microcystis ,Genotype ,Health, Toxicology and Mutagenesis ,010501 environmental sciences ,Spatial distribution ,01 natural sciences ,chemistry.chemical_compound ,Nutrient ,Botany ,Environmental Chemistry ,Biomass ,0105 earth and related environmental sciences ,Demography ,Biomass (ecology) ,biology ,010604 marine biology & hydrobiology ,Public Health, Environmental and Occupational Health ,General Medicine ,General Chemistry ,biology.organism_classification ,Pollution ,Lakes ,chemistry ,Spatial variability ,Bloom - Abstract
Cyanobacterial blooms as a global environmental issue are of public health concern. In this study, we investigated the spatial (10 sites) and temporal (June, August and October) variations in: 1) their biomass based on chlorophyll-a (chl-a) concentration, 2) their toxic genotype based on gene copy ratio of mcyJ to cpcBA, and 3) their cpcBA genotype composition of Microcystis during cyanobacterial bloom in Lake Taihu. While spatial-temporal variations were found in chl-a and mcyJ/cpcBA ratio, only spatial variation was observed in cpcBA genotype composition. Samples from northwestern part had a higher chl-a, but mcyJ/cpcBA ratio didn't vary among the sites. High chl-a was observed in August, while mcyJ/cpcBA ratio and genotypic richness increased with time. The spatial variations in chl-a and mcyJ/cpcBA ratio and temporal variation in cpcBA genotype were correlated negatively with dissolved N and positively with dissolved P. Spatial distribution of Microcystis biomass was positively correlated with nitrite and P excluding October, but no correlation was found for spatial distribution of mcyJ/cpcBA ratio and cpcBA genotype. Spatial distribution of toxic and cpcBA genotypes may result from horizontal transport of Microcystis colonies, while spatial variation in Microcystis biomass was probably controlled by both nutrient-mediated growth and horizontal transport of Microcystis. The temporal variation in Microcystis biomass, toxic genotype and cpcBA genotype composition were related to nutrient levels, but cause-and-effect relationships require further study.
- Published
- 2018
26. In situ measurement of perfluoroalkyl substances in aquatic systems using diffusive gradients in thin-films technique
- Author
-
Si Wei, William Davison, Ya-Qing Li, Hao Zhang, Xinyi Cui, Lena Q. Ma, Nanyang Yu, Jun Luo, Dong-Xing Guan, and Guanghui Yu
- Subjects
In situ ,Analyte ,Environmental Engineering ,0211 other engineering and technologies ,02 engineering and technology ,010501 environmental sciences ,Wastewater ,01 natural sciences ,Diffusion ,chemistry.chemical_compound ,Rivers ,Tandem Mass Spectrometry ,Waste Management and Disposal ,Effluent ,0105 earth and related environmental sciences ,Water Science and Technology ,Civil and Structural Engineering ,021110 strategic, defence & security studies ,Fluorocarbons ,Ecological Modeling ,Aquatic ecosystem ,Osmolar Concentration ,Hydrogen-Ion Concentration ,Pollution ,Diffusive gradients in thin films ,Lakes ,chemistry ,Alkanesulfonic Acids ,Environmental chemistry ,Perfluorooctanoic acid ,Environmental science ,Caprylates ,Water Pollutants, Chemical ,Passive sampling ,Chromatography, Liquid ,Environmental Monitoring - Abstract
To better understand the environmental impact of ubiquitous perfluoroalkyl substances (PFASs) in waters, reliable and robust measurement techniques are needed. As one of the most widely used passive sampling approaches, diffusive gradients in thin-films (DGT) is not only easy to handle but also provides time-weighted analyte concentrations. Based on DGT with XAD18 as a binding agent, we developed a new methodology to measure two frequently detected PFASs in surface waters and wastewaters, i.e. perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Their diffusion coefficients in the diffusive gel, measured using an independent diffusion cell, were 4.37 × 10−6 and 5.08 × 10−6 cm2 s−1 at 25 °C, respectively. DGT had a high capacity for PFOA and PFOS at 196 and 246 μg per gel disk, suggesting the DGT sampler was suitable for deployment of several weeks. Time-integrated concentrations of PFOA and PFOS in a natural lake and river, and a municipal wastewater treatment plant effluent using DGT samplers deployed in situ for 12–33 d were comparable to those measured by a solid-phase extraction method coupled with high-frequency grab sampling. This study demonstrates that DGT is an effective tool for in situ monitoring of PFASs in natural waters and wastewaters.
- Published
- 2018
27. Fluoride prevalence in groundwater around a fluorite mining area in the flood plain of the River Swat, Pakistan
- Author
-
Shah Jehan, Abdur Rashid, Muhammad Sufaid Khan, Seema Anjum Khattak, Raees Khan, Abida Farooqi, Dong-Xing Guan, Salman Zahir, Sardar Khan, University of Peshawar, Quaid-i-Azam University, Nanjing University, and Universidade Estadual Paulista (Unesp)
- Subjects
Environmental Engineering ,010504 meteorology & atmospheric sciences ,Floodplain ,Aquifer ,Weathering ,010501 environmental sciences ,Flood plain area ,01 natural sciences ,Fluorite ,Mining ,chemistry.chemical_compound ,Fluoride bearing minerals ,Fluorides ,Rivers ,Silicate minerals ,Environmental Chemistry ,Pakistan ,Hydrogeochemistry ,Waste Management and Disposal ,Groundwater ,0105 earth and related environmental sciences ,Geochemical modeling ,geography ,geography.geographical_feature_category ,Pollution ,Dental fluorosis ,chemistry ,Environmental chemistry ,Environmental science ,Fluoride ,Environmental Monitoring - Abstract
Made available in DSpace on 2018-12-11T16:52:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-09-01 Higher Education Commission, Pakistan University of Peshawar This study investigated the fluoride (F−) concentrations and physicochemical parameters of the groundwater in a fluorite mining area of the flood plain region of the River Swat, with particular emphasis on the fate and distribution of F− and the hydrogeochemistry. To better understand the groundwater hydrochemical profile and F− enrichment, groundwater samples (n = 53) were collected from shallow (24–40 m), mid-depth (48–65 m) and deep (85–120 m) aquifers, and then analysed using an ion-selective electrode. The lowest F− concentration (0.7 mg/L) was recorded in the deep-aquifer groundwater, while the highest (6.4 mg/L) was recorded in shallow groundwater. Most groundwater samples (62.2%) exceeded the guideline (1.5 mg/L) set by the World Health Organization (WHO); while for individual sources, 73% of shallow-groundwater samples (F− concentration up to 6.4 mg/L), 42% of mid-depth-groundwater samples, and 17% of deep-groundwater samples had F− concentrations that exceeded this permissible limit. Assessment of the overall quality of the groundwater revealed influences of the weathering of granite and gneisses rocks, along with silicate minerals and ion exchange processes. Hydrogeochemical analysis of the groundwater showed that Na+ is the dominant cation and HCO3 − the major anion. The anionic and cationic concentrations across the entire study area increased in the following order: HCO3 > SO4 > Cl > NO3 > F > PO4 and Na > Ca > Mg > K, respectively. Relatively higher F− toxicity levels were associated with the NaHCO3 water type, and the chemical facies were found to change from the CaHCO3 to (Na–HCO3) type in calcium-poor aquifers. Thermodynamic considerations of saturation indices indicated that fluorite minerals play a vital role in the prevalence of fluorosis, while under-saturation revealed that – besides fluorite minerals – other F− minerals that are also present in the region further increase the F− concentrations in the groundwater. Finally, a health risk assessment via Dean's classification method identified that the groundwater with relatively higher F− concentrations is unfit for drinking purposes. Department of Environmental Sciences University of Peshawar Hydrogeochemistry Laboratory Department of Environmental Sciences Faculty of Biological Sciences Quaid-i-Azam University, PO 45320 Key Laboratory of Surficial Geochemistry Ministry of Education School of Earth Sciences and Engineering Nanjing University National Centre of Excellence in Geology University of Peshawar Departamento de Fısico-Quımica de Instituto Quımica Universidade Estadual Paulista (UNESP) Departamento de Fısico-Quımica de Instituto Quımica Universidade Estadual Paulista (UNESP) University of Peshawar: 5135/NRPU
- Published
- 2017
28. Novel Precipitated Zirconia-Based DGT Technique for High-Resolution Imaging of Oxyanions in Waters and Sediments
- Author
-
Paul N. Williams, Huacheng Xu, Jun Luo, Jian Lun Zheng, Chao Cai, Lena Q. Ma, and Dong-Xing Guan
- Subjects
Anions ,Geologic Sediments ,Time Factors ,Materials science ,Analytical chemistry ,Oxyanion ,Environment ,Diffusion ,Ferrihydrite ,chemistry.chemical_compound ,Imaging, Three-Dimensional ,Chemical Precipitation ,Environmental Chemistry ,Cubic zirconia ,Precipitation (chemistry) ,Spectrophotometry, Atomic ,Osmolar Concentration ,Water ,Sorption ,General Chemistry ,Hydrogen-Ion Concentration ,Diffusive gradients in thin films ,Oxygen ,Kinetics ,chemistry ,Zirconium ,Particle size ,Gels ,Layer (electronics) ,Water Pollutants, Chemical - Abstract
Water-sediment exchange is a fundamental component of oxyanion cycling in the environment. Yet, many of the (im)mobilization processes overlay complex spatial and temporal redox regimes that occur within millimeters of the interface. Only a few methods exist that can reliably capture these porewater fluxes, with the most popular being high-resolution diffusive gradients in thin films (HR-DGT). However, functionality of HR-DGT is restricted by the availability of suitable analyte binding agents within the sampler, which must be simple to cast and homogeneously distributed in the binding layer, exhibit adequate sorption capacities, be resistive to chemical change, and possess a very fine particle size (≤10 μm). A novel binding layer was synthesized to meet these requirements by in situ precipitation of zirconia into a precast hydrogel. The particle diameter≤0.2 μm of zirconia in this precipitated gel was uniform and at least 50-times smaller than the conventional molding approach. Further, this gel had superior binding and stability characteristics compared with the commonly used ferrihydrite HR-DGT technique and could be easily fabricated as an ultrathin gel (60 μm) for simultaneous oxygen imaging in conjunction with planar-optodes. Chemical imaging of anion and oxygen fluxes using the new sampler were evaluated on Lake Taihu sediments.
- Published
- 2015
29. Characterization of arsenic-resistant endophytic bacteria from hyperaccumulators Pteris vittata and Pteris multifida
- Author
-
Bala Rathinasabapathi, Dong-Xing Guan, Jun Luo, Ling-Jia Zhu, and Lena Q. Ma
- Subjects
Siderophore ,Environmental Engineering ,Arsenites ,Health, Toxicology and Mutagenesis ,chemistry.chemical_element ,Bacillus ,Biology ,Polymerase Chain Reaction ,Arsenic ,chemistry.chemical_compound ,Species Specificity ,RNA, Ribosomal, 16S ,Drug Resistance, Bacterial ,Botany ,Endophytes ,Environmental Chemistry ,Hyperaccumulator ,DNA Primers ,Arsenite ,Analysis of Variance ,Public Health, Environmental and Occupational Health ,Arsenate ,food and beverages ,Pteris ,General Medicine ,General Chemistry ,biology.organism_classification ,Pollution ,Transformation (genetics) ,Biodegradation, Environmental ,chemistry ,Pteris vittata ,Arsenates ,Oxidation-Reduction ,Bacteria - Abstract
We isolated and characterized As-resistant endophytic bacteria (AEB) from two arsenic hyperaccumulators. Their plant growth promoting traits and the relation between As tolerance and transformation were evaluated. A total of 41 and 33 AEB were isolated from Pteris vittata (PV) and Pteris multifida (PM) respectively. PV AEB represented 2 genera while PM AEB comprised of 12 genera, with Bacillus sp. being the most dominant bacteria from both plants. All AEB had limited ability in solubilizing P and producing indole acetic acid (IAA) and siderophore. All isolates tolerated 10 mM arsenate (As(V)), with PV isolates being more tolerant to As(V) and PM more tolerant to arsenite (As(III)). Bacterial arsenic tolerance was related to their ability in As(III) oxidation and As(V) reduction as well as their ability to retain As in the biomass to a varying extent. Though AEB showed limited plant growth promoting traits, they were important in arsenic tolerance and speciation in plants.
- Published
- 2014
30. Research on Influences of 'A Test of Different Initial pH from the Reaction' with Properties of Environment Materials on Distribution of Arsenic Speciation Arsenic-Ferric Precipitation
- Author
-
Meng Qi Wang and Xing Guan Ma
- Subjects
inorganic chemicals ,integumentary system ,Coprecipitation ,Precipitation (chemistry) ,Extraction (chemistry) ,Inorganic chemistry ,General Engineering ,chemistry.chemical_element ,Chloride ,Adsorption ,chemistry ,Environmental chemistry ,medicine ,Ferric ,Absorption (chemistry) ,Arsenic ,medicine.drug - Abstract
The distribution of arsenic speciation can be applied to elucidate the mechanism of removal arsenic during treatment the water containing arsenic with molysite. In this study, the effect of initial pH on the distribution of arsenic speciation in arsenic-ferric precipitation was determined by a five-step sequential extraction procedure. And then further explore the mechanism of arsenic removal with molysite. This experimental results showed that the main mechanisms governing the arsenic removal with ferric chloride were specific adsorption and coprecipitation. Besides, as pH increased from 5 to 9, the arsenic-ferric coprecipitation played a more and more important role in mechanism of arsenic removal with molysite. At the same time, the water soluble state As and the non-specific adsorption As were barely detectable, which suggested that physical absorption had almost no effect on arsenic removal.
- Published
- 2014
31. High Resolution measurement and mapping of tungstate in waters, soils and sediments using the low-disturbance DGT sampling technique
- Author
-
Huacheng Xu, Jun Luo, Dong-Xing Guan, Gang Li, Paul N. Williams, and Lena Q. Ma
- Subjects
Environmental Engineering ,Materials science ,010504 meteorology & atmospheric sciences ,Health, Toxicology and Mutagenesis ,Analytical chemistry ,chemistry.chemical_element ,010501 environmental sciences ,Tungsten ,01 natural sciences ,Pollution ,Matrix (chemical analysis) ,chemistry.chemical_compound ,Ferrihydrite ,Flux (metallurgy) ,chemistry ,Tungstate ,Soil water ,Slurry ,Environmental Chemistry ,Diffusion (business) ,Waste Management and Disposal ,0105 earth and related environmental sciences - Abstract
Increasing tungsten (W) use for industrial and military applications has resulted in greater W discharge into natural waters, soils and sediments. Risk modeling of W transport and fate in the environment relies on measurement of the release/mobilization flux of W in the bulk media and the interfaces between matrix compartments. Diffusive gradients in thin-films (DGT) is a promising passive sampling technique to acquire such information. DGT devices equipped with the newly developed high-resolution binding gels (precipitated zirconia, PZ, or ferrihydrite, PF, gels) or classic/conventional ferrihydrite slurry gel were comprehensively assessed for measuring W in waters. (Ferrihydrite)DGT can measure W at various ionic strengths (0.001-0.5molL(-1) NaNO3) and pH (4-8), while (PZ)DGT can operate across slightly wider environmental conditions. The three DGT configurations gave comparable results for soil W measurement, showing that typically W resupply is relatively poorly sustained. 1D and 2D high-resolution W profiling across sediment-water and hotspot-bulk media interfaces from Lake Taihu were obtained using (PZ)DGT coupled with laser ablation ICP-MS measurement, and the apparent diffusion fluxes across the interfaces were calculated using a numerical model.
- Published
- 2016
32. Arsenic Induced Phytate Exudation, and Promoted FeAsO4 Dissolution and Plant Growth in As-Hyperaccumulator Pteris vittata
- Author
-
Xue Liu, Yue Cao, Bala Rathinasabapathi, Dong-Xing Guan, Jing-Wei Fu, Jun Luo, Yanshan Chen, and Lena Q. Ma
- Subjects
0106 biological sciences ,Phytic Acid ,chemistry.chemical_element ,010501 environmental sciences ,01 natural sciences ,Plant Roots ,Oxalate ,Arsenic ,chemistry.chemical_compound ,Botany ,Environmental Chemistry ,Soil Pollutants ,Hyperaccumulator ,Pteris ,0105 earth and related environmental sciences ,Phytic acid ,biology ,Chemistry ,General Chemistry ,biology.organism_classification ,Biodegradation, Environmental ,Solubility ,Pteris vittata ,Solanum ,010606 plant biology & botany ,Pteris ensiformis - Abstract
Arsenic hyperaccumulator Pteris vittata (PV) is efficient in taking up As and nutrients from As-contaminated soils. We evaluated the mechanisms used by PV to mobilize As and Fe by examining the impacts of As and root exudates on FeAsO4 solubilization, and As and Fe uptake in four plants: As-hyperaccumulators PV and Pteris multifida (PM), nonhyperaccumulator Pteris ensiformis (PE), and angiosperm plant tomato (Solanum lycopersicum). Phytate and oxalate were dominant in fern plants (93%), which were 50-83, 15-42, and 0-32 mg kg(-1) phytate and 10-15, 7-26, and 4-12 mg kg(-1) oxalate for PV, PM, and PE respectively, with higher As inducing greater phytate exudation and no phytate being detected in tomato exudates. PV treated with phytate+FeAsO4 had higher As and Fe contents and larger biomass than phytate or FeAsO4 treatment, which were 340 vs 20 and 130 mg kg(-1) As in the fronds and 7900 vs 1600 and 4100 mg kg(-1) Fe in the roots. We hypothesized that As-induced phytate exudation helped PV to take up Fe and As from insoluble FeAsO4 and promoted PV growth. Our study suggests that phytate exudation may be special to fern plants, which may play an important role in enhancing As and nutrient uptake by plants, thereby increasing their efficiency in phytoremediation of As-contaminated soils.
- Published
- 2016
33. Novel DGT method with tri-metal oxide adsorbent for in situ spatiotemporal flux measurement of fluoride in waters and sediments
- Author
-
Chen Yang Zhou, Dong-Xing Guan, Jun Luo, Lena Q. Ma, and Paul N. Williams
- Subjects
Environmental Engineering ,010501 environmental sciences ,01 natural sciences ,chemistry.chemical_compound ,Fluorides ,Adsorption ,Flux (metallurgy) ,Waste Management and Disposal ,Dissolution ,0105 earth and related environmental sciences ,Water Science and Technology ,Civil and Structural Engineering ,SDG 15 - Life on Land ,Ecological Modeling ,010401 analytical chemistry ,Osmolar Concentration ,Sediment ,Water ,Sorption ,Hydrogen-Ion Concentration ,Pollution ,Diffusive gradients in thin films ,0104 chemical sciences ,chemistry ,Metals ,Environmental chemistry ,Environmental science ,SDG 6 - Clean Water and Sanitation ,Fluoride ,Surface water - Abstract
Natural mineral-water interface reactions drive ecosystem/global fluoride (F−) cycling. These small-scale processes prove challenging to monitoring due to mobilization being highly localized and variable; influenced by changing climate, hydrology, dissolution chemistries and pedogenosis. These release events could be captured in situ by the passive sampling technique, diffusive gradients in thin-films (DGT), providing a cost-effective and time-integrated measurement of F− mobilization. However, attempts to develop the method for F− have been unsuccessful due to the very restrictive operational ranges that most F−-absorbents function within. A new hybrid-DGT technique for F− quantification containing a three-phase fine particle composite (Fesingle bondAlsingle bondCe, FAC) adsorbent was developed and evaluated. Sampler response was validated in laboratory and field deployments, passing solution chemistry QC within ionic strength and pH ranges of 0–200 mmol L−1 and 4.3–9.1, respectively, and exhibiting high sorption capacities (98 ± 8 μg cm−2). FAC-DGT measurements adequately predicted up to weeklong averaged in situ F− fluvial fluxes in a freshwater river and F− concentrations in a wastewater treatment flume determined by high frequency active sampling. While, millimetre-scale diffusive fluxes across the sediment-water interface were modeled for three contrasting lake bed sediments from a F−-enriched lake using the new FAC-DGT platform.
- Published
- 2016
34. Arsenic-induced plant growth of arsenic-hyperaccumulator Pteris vittata: Impact of arsenic and phosphate rock
- Author
-
Lena Q. Ma, Guang-Mei Yang, Jing-Wei Fu, Yanshan Chen, Dong-Xing Guan, and Yong-He Han
- Subjects
0106 biological sciences ,Frond ,Environmental Engineering ,Arsenites ,Health, Toxicology and Mutagenesis ,Amendment ,chemistry.chemical_element ,Plant Development ,010501 environmental sciences ,Biology ,complex mixtures ,01 natural sciences ,Plant Roots ,Arsenic ,Phosphates ,chemistry.chemical_compound ,Soil ,Botany ,Environmental Chemistry ,Soil Pollutants ,Hyperaccumulator ,Biomass ,0105 earth and related environmental sciences ,Arsenite ,fungi ,Public Health, Environmental and Occupational Health ,food and beverages ,Pteris ,General Medicine ,General Chemistry ,biology.organism_classification ,Pollution ,Horticulture ,Biodegradation, Environmental ,chemistry ,Phosphorite ,Pteris vittata ,Soil water ,010606 plant biology & botany - Abstract
Phosphate rock (PR) has been shown to promote plant growth and arsenic (As) uptake by As-hyperaccumulator Pteris vittata (PV). However, little is known about its behaviors in agricultural soils. In this study, impact of 50 mg kg(-1) As and/or 1.5% PR amendment on plant As accumulation and growth was investigated by growing PV for 90 d in three agricultural soils. While As amendment significantly increased plant As uptake and substantially promoted PV growth, the opposite was observed with PR amendment. Arsenic amendment increased plant frond As from 16.9-265 to 961-6017 mg kg(-1),whereas PR amendment lowered frond As to 10.2-216 mg kg(-1). The As-induced plant growth stimulation was 69-71%. While PR amendment increased plant Ca and P uptake, As amendment showed opposite results. The PV biomass was highly correlated with plant As at r = 0.82, but with weak correlations with plant Ca or P at r < 0.30. This study confirmed that 1) As significantly promoted PV growth, probably independent of Ca or P uptake, 2) PR amendment didn't enhance plant growth or As uptake by PV in agricultural soils with adequate available P, and 3) PV effluxed arsenite (AsIII) growing in agricultural soils.
- Published
- 2015
35. Novel Speciation Method Based on Diffusive Gradients in Thin-Films for in Situ Measurement of Cr(VI) in Aquatic Systems
- Author
-
Dong-Xing Guan, Di Zhao, Jun Luo, Hao Zhang, William Davison, Pan Yue, and Lena Q. Ma
- Subjects
In situ ,Chromium ,China ,media_common.quotation_subject ,Diffusion ,chemistry.chemical_element ,Fresh Water ,Metal ,chemistry.chemical_compound ,Meglumine ,Environmental Chemistry ,Hexavalent chromium ,media_common ,Chemistry ,Aquatic ecosystem ,Osmolar Concentration ,Reproducibility of Results ,Water ,General Chemistry ,Hydrogen-Ion Concentration ,Diffusive gradients in thin films ,Speciation ,Kinetics ,Metals ,visual_art ,Environmental chemistry ,visual_art.visual_art_medium ,Gels ,Water Pollutants, Chemical - Abstract
Hexavalent chromium (Cr(VI)) is much more toxic and mobile than the trivalent species (Cr(III)) and consequently, in situ monitoring of Cr(VI) can improve the understanding of Cr biogeochemistry and toxicity in ecosystems. The passive diffusive gradients in thin-films (DGT) technique is a powerful tool for determining metal(loid) speciation, but a binding phase that absorbs only one specific species of Cr is needed. N-Methyl-d-glucamine (NMDG) functional resin was incorporated into the DGT binding phase for selective measurement of Cr(VI). This NMDG-DGT sampler exhibited a theoretically linear accumulation of Cr(VI), with negligible accumulation (5%) of Cr(III), even after 72 h deployment. The good prediction of Cr(VI) concentration in synthetic freshwater with NMDG-DGT, even in the presence of 10-time more Cr(III), further indicated the sampler's reliability in selective detection of Cr(VI). Moreover, its high capacity for Cr(VI), which exceeded 230 μg cm(-2), facilitates measurement of Cr(VI) in both uncontaminated natural waters and in slightly and heavily contaminated (ppm level) waters. Field deployment of the NMDG-DGT sampler in such waters allowed accurate measurement of time-averaged Cr(VI) concentration, indicating its robustness for in situ measurements of Cr speciation and its potential for further application in the risk assessment of Cr.
- Published
- 2015
36. Study on Aerobic Process Treat Auto Manufacturing Wastewater
- Author
-
Xing Guan Ma, Wei Cui, Chen Chen, Tie Shan Ming, and Jing Wen
- Subjects
Pollutant ,Anaerobic respiration ,Wastewater ,Chemistry ,law ,Environmental chemistry ,General Engineering ,Alkalinity ,Turbidity ,Effluent ,Anaerobic exercise ,Filtration ,law.invention - Abstract
In dealing with auto manufacturing wastewater, aerobic process was viewed as the follow-up treatment of anaerobic process. Studying on the system of aerobic contact oxidation, all kinds of factors (HRT, influent CODCr concentration, dissolved oxygen (DO), pH value, alkalinity) effect on removal efficiency of the anaerobic effluent CODCr, NH4+–N, NO3–N and turbidity. The results showed that: when the filtration rate is less than 0.0625ml•h-1, in the aerobic contact oxidation system ,the organic pollutant′s removal efficiency is very stable; in system, when dissolved oxygen concentration is greater than 10.00ml•h-1, its removal efficiency keep a higher level; aerobic process could remove 81% of COD of the influent,and the effluent COD could meet the qualityⅡ of Discharge standard of wastewater pollutants for industry(GB8978—1996) .
- Published
- 2011
37. Catecholate-siderophore produced by As-resistant bacterium effectively dissolved FeAsO4 and promoted Pteris vittata growth
- Author
-
Piyasa Ghosh, Guang-Mei Yang, Xue Liu, Dong-Xing Guan, and Lena Q. Ma
- Subjects
Siderophore ,Health, Toxicology and Mutagenesis ,Biology ,Deferoxamine ,Toxicology ,Rhizobacteria ,Plant Roots ,Arsenicals ,Pseudomonas ,Botany ,Drug Resistance, Bacterial ,Soil Pollutants ,Biomass ,Pteris ,Soil Microbiology ,Hoagland solution ,General Medicine ,biology.organism_classification ,Pollution ,Phytoremediation ,Biodegradation, Environmental ,Solubility ,Environmental chemistry ,Pteris vittata ,Soil microbiology - Abstract
The impact of siderophore produced by arsenic-resistant bacterium Pseudomonas PG12 on FeAsO4 dissolution and plant growth were examined. Arsenic-hyperaccumulator Pteris vittata was grown for 7 d in 0.2-strength Fe-free Hoagland solution containing FeAsO4 mineral and PG12-siderophore or fungal-siderophore desferrioxamine B (DFOB). Standard siderophore assays indicated that PG12-siderophore was catecholate-type. PG12-siderophore was more effective in promoting FeAsO4 dissolution, and Fe and As plant uptake than DFOB. Media soluble Fe and As in PG12 treatment were 34.6 and 3.07 μM, 1.6- and 1.4-fold of that in DFOB. Plant Fe content increased from 2.93 to 6.24 g kg(-1) in the roots and As content increased from 14.3 to 78.5 mg kg(-1) in the fronds. Besides, P. vittata in PG12 treatment showed 2.6-times greater biomass than DFOB. While P. vittata fronds in PG12 treatment were dominated by AsIII, those in DFOB treatment were dominated by AsV (61-77%). This study showed that siderophore-producing arsenic-resistant rhizobacteria may have potential in enhancing phytoremediation of arsenic-contaminated soils.
- Published
- 2015
38. Effect of aging on arsenic and lead fractionation and availability in soils: coupling sequential extractions with diffusive gradients in thin-films technique
- Author
-
Shuang Liang, Jun Luo, Jinghua Ren, Lena Q. Ma, Min Zhang, and Dong-Xing Guan
- Subjects
Environmental Engineering ,Chemistry ,Health, Toxicology and Mutagenesis ,Analytical chemistry ,chemistry.chemical_element ,Fraction (chemistry) ,Fractionation ,Chemical Fractionation ,Pollution ,Diffusive gradients in thin films ,Arsenic ,Diffusion ,chemistry.chemical_compound ,Soil ,Lead ,Environmental chemistry ,Soil water ,Correlation analysis ,Environmental Chemistry ,Carbonate ,Hydroxide ,Soil Pollutants ,Waste Management and Disposal - Abstract
We coupled the diffusive gradients in thin-films (DGT) technique with two sequential extraction methods to investigate the influence of aging on As and Pb fractionation and availability in three soils spiked with As (40 or 400 mg kg−1), Pb (150 or 1500 mg kg−1) or As + Pb (40 mg kg−1 As and 150 mg kg−1 Pb). During aging, As moved from the more available (non-specifically and specifically sorbed) to less available (amorphous and crystallized Fe/Al) fractions while Pb moved from the first three fractions (exchangeable, carbonate and Fe/Mn hydroxide) to organic fraction. However, even after 33-week aging, much more As and Pb were in the least available residual fraction in spiked soils than native soils (11–59% vs. 1.2–12%). Relatively, As in spiked soils was much more available than Pb with 11–14% As and 46–59% Pb in the residual fraction. Correlation analysis indicated that As in the non-specifically and specifically sorbed fractions and Pb in the exchangeable fraction were likely sources of DGT-measured labile As and Pb. The fact that As and Pb distribution and availability in spiked soils were significantly different from native soils suggests caution needs to be exercised when using spiked soils for research.
- Published
- 2014
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.