خيارات البحث
النتائج 281 - 290 من 4,938
The accumulation and distribution of five antibiotics from soil in 12 cultivars of pak choi النص الكامل
2019
Yu, Xiaolu | Liu, Xiaoxia | Liu, Hang | Chen, Junhao | Sun, Ying
There is a lack of understanding about the potential accumulation of antibiotics in plants exposed to low-dose contaminated soil. 12 Brassica rapa subsp. chinensis cultivars were used to investigate the different accumulation capacities of sulfamethoxypyridazine, tetracycline, ofloxacin, norfloxacin and difloxacin from the soil. The results showed a significant variation (p < 0.05) among the 12 cultivars in the accumulation of antibiotics. Cultivars Y1 and Y2 had the highest accumulation capacity with average concentrations of 3.26 and 3.00 μg kg⁻¹, respectively, while cultivars Y4 and Y9 had the lowest accumulation capacity with average concentrations of 0.83 and 0.89 μg kg⁻¹. The average antibiotic concentration in all edible part samples (2.74 μg kg⁻¹) of the treatment group was about 3.0-fold of that of the control group (0.93 μg kg⁻¹). The average bioconcentration factors of sulfamethoxypyridazine, tetracycline, ofloxacin, norfloxacin and difloxacin were 0.051, 0.031, 0.017, 0.036 and 0.034, respectively, indicating a higher uptake of sulfamethoxypyridazine compared to ofloxacin. And the mobility of antibiotics in soil is a main factor affecting the bioavailability for plants. The average concentration of antibiotics in edible parts of cultivar Y12 on the 25th and 45th day were 1.52 and 1.73 μg kg⁻¹ and that of the roots were 3.73 and 6.61 μg kg⁻¹, respectively. The concentrations of tetracycline and difloxacin in the edible parts and roots significantly increased with growing time, while the concentration of sulfamethoxypyridazine and ofloxacin changed little throughout the growing period. The potential risks of antibiotics in vegetables on human health cannot be ignored. Overall, attention should be paid to the translocation of antibiotics from soil to plants.
اظهر المزيد [+] اقل [-]Next-generation sequencing reveals fecal contamination and potentially pathogenic bacteria in a major inflow river of Taihu Lake النص الكامل
2019
Vadde, Kiran Kumar | Feng, Qiaoli | Wang, Jianjun | McCarthy, Alan J. | Sekar, Raju
Taihu Lake is one of the largest freshwater lakes in China and serves as an important source for drinking water. This lake is suffering from eutrophication, cyanobacterial blooms and fecal pollution, and the inflow Tiaoxi River is one of the main contributors. The goal here was to characterize the bacterial community structure of Tiaoxi River water by next-generation sequencing (NGS), paying attention to bacteria that are either fecal-associated or pathogenic, and to examine the relationship between environmental parameters and bacterial community structure. Water samples collected from 15 locations in three seasons, and fecal samples collected from different hosts and wastewater samples were used for bacterial community analysis. The phyla Proteobacteria, Actinobacteria, Bacteroidetes, and Cyanobacteria were predominant in most of the water samples tested. In fecal samples, Bacteroidetes, Firmicutes, and Proteobacteria were abundant, while wastewater samples were dominated by Proteobacteria, Bacteroidetes, Acidobacteria, and Chloroflexi. The cluster analysis and principal coordinate analysis indicated that bacterial community structure was significantly different between water, fecal and sewage samples. Shared OTUs between water samples and chicken, pig, and human fecal samples ranged from 4.5 to 9.8% indicating the presence of avian, pig and human fecal contamination in Tiaoxi River. At genus level, five bacterial genera of fecal origin and sequences of seven potential pathogens were detected in many locations and their presence was correlated well with the land use pattern. The sequencing data revealed that Faecalibacterium could be a potential target for human-associated microbial source-tracking qPCR assays. Our results suggest that pH, conductivity, and temperature were the main environmental factors in shaping the bacterial community based on redundancy analysis. Overall, NGS is a valuable tool for preliminary investigation of environmental samples to identify the potential human health risk, providing specific information about fecal and potentially pathogenic bacteria that can be followed up by specific methods.
اظهر المزيد [+] اقل [-]A nationwide survey of the occurrence of melamine and its derivatives in archived sewage sludge from the United States النص الكامل
2019
Zhu, Hongkai | Halden, Rolf U. | Kannan, Kurunthachalam
Melamine-based resins are used extensively in laminates, plastics, coatings, glues, and dinnerware. Little is known, however, about the occurrence of melamine and its derivatives in the environment. In this study, a nationwide survey of melamine and its derivatives, namely ammeline, ammelide, and cyanuric acid, was conducted, using archived sewage sludge samples collected from 68 wastewater treatment plants in the United States (U.S.). The sum concentrations of four target compounds in sludge ranged from 34 to 1800 ng/g dry weight (dw), with a mean concentration of 240 ng/g dw; melamine (46%) and cyanuric acid (40%) collectively accounted for 86% of the total mass of analytes. No significant geographical variation in the concentrations of melamine and its derivatives in sewage sludge was found. The estimated emission of melamine and its derivatives via land-application of sludge was approximately 1600 kg/yr in the U.S. The hazard quotient values for melamine in sludge-amended soils ranged from 2.2 × 10−5 to 4.4 × 10−3, indicating that the current levels of melamine in sludge pose a minimal risk to the soil environment.
اظهر المزيد [+] اقل [-]Accumulation, ecological-health risks assessment, and source apportionment of heavy metals in paddy soils: A case study in Hanzhong, Shaanxi, China النص الكامل
2019
Xiao, Ran | Guo, Di | Ali, Amjad | Mi, Shenshen | Liu, Tao | Ren, Chunyan | Li, Ronghua | Zhang, Zengqiang
Contamination of agricultural soil by heavy metals has become a global issue concerning food security and human health risk. In this study, a soil investigation was conducted to evaluate metals accumulation, potential ecological and health risks as well as to identify sources of metals in paddy soils in Hanzhong City, which is located in a sedimentary basin. Ninety-two (92) surface soil samples (bulk soil) and their corresponding rice samples, 21 irrigation water samples, and 18 fertilizer samples were collected from two typical counties and quantified for the heavy metals (i.e., As, Cd, Cu, Hg, Pb, and Zn) concentrations. The results showed that As, Cd, and Zn were the main contaminants in soils in the studied area. Additionally, elevated Hg content in soils might also pose risks to the local ecosystem. Cadmium and As demonstrated high mobility, and their average contents in rice grains were slightly higher than the permissible threshold (0.20 mg kg⁻¹). Moreover, Pb, As, and Cd intake via rice consumption might result in potential risks to local residents. Metal distribution revealed that pollution in the studied area is non-homogeneous, and agricultural activities (As, Cu, and Cd), transportation emission (Cu and Pb), coal combustion (Hg and As), and smelting activities (Zn, Pb, and Cu) were ascertained as the potential sources based on the Positive matrix factorization (PMF) analysis results.
اظهر المزيد [+] اقل [-]Petroleum biomarkers as tracers of low-level chronic oil contamination of coastal environments: A systematic approach in a subtropical mangrove النص الكامل
2019
Garcia, Marina Reback | Cattani, André Pereira | Lana, Paulo da Cunha | Figueira, Rubens César Lopes | Martins, César C.
Petroleum biomarkers (hopanes, terpanes and steranes) are frequently assessed in estuarine sediments as tracers of oil input. In order to compare distinct patterns of hydrocarbon accumulation in mudflats, salt marsh and mangrove, sediments from two transects (control and impacted areas) were sampled in Paranaguá Bay, SW Atlantic. Concentrations of n-alkanes, polycyclic aromatic hydrocarbons (PAHs) and petroleum biomarkers (hopanes, terpanes and steranes) were determined, as well as bulk parameters (TOC, grain size and δ13C). N-alkanes concentrations were similar between control and impacted sites (respectively, 3.03 ± 1.20 μg g−1 and 4.11 ± 3.02 μg g−1) and reflected a high biogenic input. Conversely, PAHs and petroleum biomarker concentrations were three to six times higher in impacted site than the control site (respectively, 60.4 ± 23.3 ng g−1 and 22.0 ± 25.0 ng g−1 for PAHs and 197.7 ± 51.8 ng g−1 and 40.2 ± 32. ng g−1 for hopanes). Despite these differences, concentrations were lower than those reported for highly impacted areas worldwide. Diagnostic ratios and hydrocarbon parameters (e.g. total PAHs and total petroleum biomarkers) helped to distinguish human impact in the ecological zones, suggesting different sources and/or levels of weathering, confirmed by ANOVA tests. TOC played a fundamental role to the concentration of hydrocarbons, showing similar distributions along the transects. Petroleum biomarkers could clearly indicate the preferential sites of deposition and assign different levels of anthropic contamination by hydrocarbons, thus providing clear information about the chronic petroleum pollution in coastal sediments.
اظهر المزيد [+] اقل [-]Metal/metalloid and phosphorus characteristics in porewater associated with manganese geochemistry: A case study in the Jiulong River Estuary, China النص الكامل
2019
Pan, Feng | Liu, Huatai | Guo, Zhanrong | Cai, Yu | Fu, Yuyao | Wu, Jinye | Wang, Bo | Gao, Aiguo
Sediment porewater can be an important source of contaminants in the overlying water, but the mechanisms of metal(loid) and phosphorus (P) remobilization remain to be investigated. In this study, high-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) samplers were used to determine the porewater dissolved iron (Fe), manganese (Mn), cobalt (Co), chromium (Cr), vanadium (V), selenium (Se), arsenic (As), P and DGT-Labile S in coastal sediments in the Jiulong River Estuary (JRE), China. The results showed that high concentrations of dissolved Mn, Se and P were present in the overlying water, indicating potential water pollution with excessive amounts of Mn, Se and P. The dissolved Mn concentrations in the porewater were higher than the dissolved Fe concentrations, especially at submerged sites, demonstrating that Mn(III/IV) reduction is the dominant diagenetic pathway for organic carbon (OC) degradation, which directly affects Fe cycling by the competitive inhibition of Fe(III) reduction and Fe(II) reoxidation. Dissolved Co, Cr, V, Se, As and P show significant positive correlations with Mn but nearly no correlations with Fe, suggesting that the mobility of these metal(loid)s and P is associated with Mn but not Fe cycling in this region. In addition, the coelevated concentrations of the metal(loid)s, P and Mn at the submerged sites are attributed to the strengthened Mn reduction coupled with OC degradation fueled by hypoxia. The higher positive diffusion fluxes of Mn, Se and P were consistent with the excess Mn, Se and P concentrations in the overlying water, together with the approximately positive fluxes of the other metal(loid)s, indicating that sediment Mn(III/IV) reduction and concomitant metal(loid) and P remobilization might be vital pathways for metal(loid) and P migration to the overlying water.
اظهر المزيد [+] اقل [-]Biomonitoring and health risks assessment of trace elements in various age- and gender-groups exposed to road dust in habitable urban-industrial areas of Hefei, China النص الكامل
2019
Ali, Muhammad Ubaid | Liu, Guijian | Yousaf, Balal | Ullah, Habib | Abbas, Qumber | Munir, Mehr Ahmed Mujtaba | Irshad, Samina
The current study investigates the concentration of eleven trace elements in biomaterials including hair (85) and nails (85) along with seventy five (75) road dust samples collected from a healthy population of habitable urban-industrial areas of Hefei, China. The samples were acid digested and analyzed using ICP-MS for trace elements content. The mean concentration of Elements followed descending order of Zn > Mg > Fe > Cr > Al > Sn > Sr > Ti > Cu > As > Cd and Mg > Zn > Fe > Cr > Al > Sn > Ti > Cu > Sr > As > Cd in hair and nails, respectively. Overall, the concentration of elements was found to be high in female subject as compared to male. The concentration of trace elements in hair and nail exceeded the maximum permissible limits in most cases. The corresponding mean values from dust samples were fairly high as compared to background values of trace elements. Middle age groups (21–30 years and 31–40 years) were observed to be the most vulnerable there-by posing a high health risk, as the concentration of trace elements was significantly high in these groups except for Al, which was detected high in age < 20 in case of both male and female. A significantly high correlation was found between trace elements in biomaterials and those detected in dust samples. In hair samples, a significantly positive correlation was noticed for As with Mg, Zn, Sn and Fe, Sn/Mg and Mg/Ti. In the case of nails, a significant correlation was observed for elements like Al, Mg, Zn, Cr, and Cu. The Cluster and principal component analysis revealed industrial and vehicular emissions as main sources for trace elements exposure in humans.
اظهر المزيد [+] اقل [-]Adsorption of methylene blue and Cd(II) onto maleylated modified hydrochar from water النص الكامل
2019
Li, Bing | Guo, Jianzhong | Lv, Kangle | Fan, Jiajie
A new carboxylate-functionalized hydrochar (CFHC) was successfully prepared by reaction of hydrochar with maleic anhydride under solvent-free conditions and followed by deprotonating carboxyl group of hydrochar with NaHCO₃ solution. CFHC was characterized using X-ray photoelectron spectroscopy (XPS), elemental analysis (EA), zeta potential, Brunauer-Emmett-Teller surface area (BET) and Fourier-transform infrared spectroscopy (FTIR), and its adsorption properties and mechanisms to methylene blue (MB) and Cd(II) were investigated using the batch method. The isotherm adsorption data were accorded with Langmuir model and the maximum uptakes were 1155.57 and 90.99 mg/g for MB and Cd(II) at the temperature of 303 K, respectively. The joint analysis of batch experiments and characterizations of hydrochar confirmed the π-π interaction was accompanied by electrostatic interaction and hydrogen bond for MB adsorption, while the surface complexation and ion exchange were predominant mechanisms for Cd(II) adsorption. Therefore, a highly effective adsorbent CFHC prepared by a simple and environmentally friendly solid-phase synthesis is a promising candidate for wastewater treatment.
اظهر المزيد [+] اقل [-]Impacts of microplastics on growth and health of hermatypic corals are species-specific النص الكامل
2019
Reichert, Jessica | Arnold, Angelina L. | Hoogenboom, Mia O. | Schubert, Patrick | Wilke, Thomas
Coral reefs are increasingly affected by the consequences of global change such as increasing temperatures or pollution. Lately, microplastics (i.e., fragments < 5 mm) have been identified as another potential threat. While previous studies have assessed short-term effects caused by high concentrations of microplastics, nothing is known about the long-term effects of microplastics under realistic concentrations. Therefore, a microcosm study was conducted and corals of the genera Acropora, Pocillopora, Porites, and Heliopora were exposed to microplastics in a concentration of 200 particles L⁻¹, relating to predicted pollution levels. Coral growth and health, as well as symbiont properties were studied over a period of six months. The exposure caused species-specific effects on coral growth and photosynthetic performance. Signs of compromised health were observed for Acropora and Pocillopora, those taxa that frequently interact with the particles. The results indicate elevated energy demands in the affected species, likely due to physical contact of the corals to the microplastics. The study shows that microplastic pollution can have negative impacts on hermatypic corals. These effects might amplify corals' susceptibility to other stressors, further contributing to community shifts in coral reef assemblages.
اظهر المزيد [+] اقل [-]Forecasting China's wastewater discharge using dynamic factors and mixed-frequency data النص الكامل
2019
Ding, Lili | Lv, Zhanlei | Han, Meng | Zhao, Xin | Wang, Wei
Forecasting wastewater discharge is the basis for wastewater treatment and policy formulation. This paper proposes a novel mixed-data sampling regression model, i.e., combination-MIDAS model to forecast quarterly wastewater emissions in China based on dynamic factors at different frequencies. The results show that a significant auto-correlation for wastewater emissions exists and that water consumption per ten thousand gross domestic product is the best predictor of wastewater emissions. The forecast performances of the combination-MIDAS models are robust and better than those of the benchmark models. Therefore, the combination-MIDAS models can better capture the characteristics of wastewater emissions, suggesting that the proposed method is a good method to deal with model misspecification and uncertainty for the control and management of wastewater discharge in China.
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