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21.
This study presents an integrated k-means clustering and gravity model (IKCGM) for investigating the spatiotemporal patterns of nutrient and associated dissolved oxygen levels in Tampa Bay, Florida. By using a k-means clustering analysis to first partition the nutrient data into a user-specified number of subsets, it is possible to discover the spatiotemporal patterns of nutrient distribution in the bay and capture the inherent linkages of hydrodynamic and biogeochemical features. Such patterns may then be combined with a gravity model to link the nutrient source contribution from each coastal watershed to the generated clusters in the bay to aid in the source proportion analysis for environmental management. The clustering analysis was carried out based on 1 year (2008) water quality data composed of 55 sample stations throughout Tampa Bay collected by the Environmental Protection Commission of Hillsborough County. In addition, hydrological and river water quality data of the same year were acquired from the United States Geological Survey's National Water Information System to support the gravity modeling analysis. The results show that the k-means model with 8 clusters is the optimal choice, in which cluster 2 at Lower Tampa Bay had the minimum values of total nitrogen (TN) concentrations, chlorophyll a (Chl-a) concentrations, and ocean color values in every season as well as the minimum concentration of total phosphorus (TP) in three consecutive seasons in 2008. The datasets indicate that Lower Tampa Bay is an area with limited nutrient input throughout the year. Cluster 5, located in Middle Tampa Bay, displayed elevated TN concentrations, ocean color values, and Chl-a concentrations, suggesting that high values of colored dissolved organic matter are linked with some nutrient sources. The data presented by the gravity modeling analysis indicate that the Alafia River Basin is the major contributor of nutrients in terms of both TP and TN values in all seasons. With this new integration, improvements for environmental monitoring and assessment were achieved to advance our understanding of sea-land interactions and nutrient cycling in a critical coastal bay, the Gulf of Mexico. 相似文献
22.
The effects of different cadmium (Cd) concentrations (0, 20, 60, and 100 μmol/L) on hydroponically grown Artemisia annua L. were investigated. Cd treatments applied for 0, 4, 12, 24, 72, 144, 216, and 336 hr were assessed by measuring the changes in photosynthetic pigments, electrolyte leakage, malondialdehyde (MDA) and antioxidants (ascorbic acid and glutathione), while the artemisinin content was tested after 0, 12, 144, 216, and 336 hr. A significant decrease was observed in photosynthetic pigment levels over time with increasing Cd concentration. Chlorophyll b levels were more affected by Cd than were chlorophyll a or carotenoid levels. The cell membrane was sensitive to Cd stress, as MDA content in all treatment groups showed insignificant differences from the control group, except at 12 hr treatment time. Ascorbic acid (AsA) content changed slightly over time, while glutathione (GSH) content took less time to reach a maximum as Cd concentration increased. Cd was found to promote synthesis and accumulation of artemisinin, especially at concentrations of 20 and 100 μmol/L. In conclusion, Cd stress can damage to photosynthetic pigments, and vigorously growing A. annua showed a strong tolerance for Cd stress. Appropriate amounts of added Cd aided synthesis and accumulation of artemisinin. 相似文献
23.
Chunyan Yu Hua Wang Xuan Liu Xie Quan Shuo Chen Jianlin Zhang Peng Zhang 《环境科学学报(英文版)》2014,26(7):1383-1388
To elucidate the effect of nitrite ion (NO2^-) on the photodegradation of organic pollutants, a 300 W mercury lamp and Pyrex tubes restricting the transmission of wavelengths below 290nm were used to simulate sunlight, and the photodegradation processes of 2,4-dichlorophenoxyacetic acid (2,4-D) with different concentrations of NO2^- in freshwater and seawater were studied. The effect of reactive oxygen species (ROS) on the photolysis of 2,4-D was also demonstrated using electron paramagnetic resonance (EPR). The results indicated that the 2,4-D photolysis reaction followed the first-order kinetics in freshwater and seawater under different concentrations of NO2^-. Meanwhile, the photochemical reaction rate of 2,4-D increased with increasing concentration of NO2^-. When the concentration of NO2^- was lower than 23 mg/L, the photodegradation rate of 2,4-D in seawater was higher than that in freshwater. However, when the concentration of NO2^- was reached 230 mg/L, 2,4-D degradation slowed down in seawater. It was important to note that EPR spectra showed NO2 radical was generated in the NO5 solution under simulated sunlight irradiation, indicating that 2,4-D photodegradation could be induced by NO2. These results show the key role of NO2^- in photochemistry and are helpful for better understanding of the phototransformation of environmental contaminants in natural aquatic systems. 相似文献
24.
Li Xiang Chaoyang Liu Deng Liu Liyuan Ma Xuan Qiu Hongmei Wang Xiaolu Lu 《环境科学学报(英文版)》2022,34(1):273-281
Soils and waters are heavily contaminated by antimony in Xikuangshan(XKS) mine area.It is widely accepted that oxidative dissolution of sulfide minerals and aqueous dissolution are the most prevalent geochemical mechanisms for the release of Sb to the environment.Bosea sp. AS-1 is an antimonite-oxidizer isolated from the mine slag in Xikuangshan Sb mine. Whole genome sequencing revealed the presence of multiple sulfur-oxidizing genes,antimony(Sb) metabolism genes and carbon fixation genes in AS-... 相似文献
25.
26.
Lead has caused serious environmental pollution due to its toxicity, accumulation in food chains and persistence in nature.In this paper, lead removal from aqueous solutions was investigated using condensed tannin gel adsorbent synthesized from a natural tannin compound. It is found that the adsorption is strongly affected by pH values of aqueous solutions.Within pH range of 3.5-6,when initial lead concentration is 100 mg/L, removal efficiency is more than 90%.Adsorption equilibrium is reached within 150 minutes.The adsorption isotherm fits well with the Langmuir equation, by which the saturated adsorption uptake of 190 mg Pb^2 /g dry tannin gel adsorbent is obtained.By means of thermodynamics analysis,it is revealed that the process is exothermic and the adsorption heat is up to 38.4kJ/mol.With respect to high efficiency, moderate pH requirement and minimized second pollution, the tannin gel adsorbent exhibits a promising potential in the removal of lead from wastewater. 相似文献
27.
Effect of applying selenium fertilizer to improve soil and increase selenium level in food for prevention and treatment of Kaschin-Beck disease 总被引:3,自引:0,他引:3
Chen Daizhong Ren Shangxue Lu Wulong Li Jiyun Fan Lihong Jia Zhenhu Zhang Fujing Xu Lijing Zhang Xuan 《环境科学学报(英文版)》1993,5(3):299-309
For prevention and treatment of Kaschin-Beck disease by applying Se fertilizer to soil to increase Se up to normal level for the wheat grains is introduced in this paper. After use this measure the intake of Se by the residents in the exemplary area increased from 10.4μg to 33.6 μg per day in average. After supplementing Se to human body one year, there is no new patient found among 300 healthy children in the exemplary area but 4 patients found among 264 healthy children in the control area. It is shown that by applying Se fertilizer to KBD area is a effective way for preventing and cure this disease. 相似文献
28.
The new biofilm-electrode method was used for the phenol degradation, because of its low current requirement. The biofilm-electrode
reactor consisted of immobilized degrading bacteria on Ti electrode as cathode and Ti/PbO2 electrode as anode. With the biofilmelectrode
reactor in a divided electrolytic cell, the phenol degradation rate could achieve 100% at 18 h which was higher than using
traditional methods, such as biological or electrochemical methods. Chemical oxygen demand (COD) removal rate of the biofilmelectrode
reactor was also greater than that using biological and electrochemical method, and could reach 80% at 16 h. The results
suggested that the biofilm-electrode reactor system can be used to treat wastewater with phenol. 相似文献
29.
In China, the health risk from overexposure to particles is becoming an important public health concern. To investigate daily exposure characteristics to PM 2.5 with high ambient concentration in urban area, a personal exposure study was conducted for school children, and office workers in Beijing, China. For all participants (N = 114), the mean personal 24-hr exposure concentration was 102.5, 14.7, 0.093, 0.528, 0.934, 0.174 and 0.703 μg/m 3 for PM 2.5 , black carbon, Mn, Al, Ca, Pb, and Fe. Children's exposure concentrations of PM 2.5 were 4-5 times higher than those in related studies. The ambient concentration of PM 2.5 (128.5 μg/m 3 ) was significantly higher than the personal exposure concentration (P 0.05), and exceed the reference concentration (25 μg/m 3 ) of WHO air quality guideline. Good correlation relationships and significant differences were identified between ambient concentration and personal exposure concentration. The relationships indicate that the ambient concentration is the main factor influencing personal exposure concentration, but is not a good indicator of personal exposure concentration. Outdoor activities (commute mode, exposure to heating, workday or weekend travel) influenced personal exposure concentrations significantly, but the magnitude of the influence from indoor activities (exposure to cooking) was masked by the high ambient concentrations. 相似文献
30.
Xuan Zhu Chengsong Ye Yuxin Wang Lihua Chen Lin Feng 《Frontiers of Environmental Science & Engineering》2019,13(3):45