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511.
Dissolved organic matter (DOM) plays a major role in ecological systems and influences the fate and transportation of many pollutants. Despite the significance of DOM, understanding of how environmental and anthropogenic factors influence its composition and characteristics is limited, especially in urban stormwater runoff. In this article, the chemical properties (pollutant loads, molecular weight, aromaticity, sources, and molecular composition) of DOM in stormwater extracted from three typical end-members (traffic, residential, and campus regions) were characterized by UV–visible (UV–vis) spectroscopy, excitation-emission matrix spectroscopy combined with parallel factor analysis (EEM-PARAFAC), and ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). There are three findings: (1) The basic properties of DOM in stormwater runoff varied obviously from three urban fields, and the effect of initial flush was also apparent. (2) The DOM in residential areas mainly came from autochthonous sources, while allochthonous sources primarily contributed to the DOM in traffic and campus areas. However, it was mainly composed of terrestrial humic-like components with CHO and CHON element composition and HULO and aliphatic formulas. (3) The parameters characterizing DOM were primarily related to terrestrial source and aromaticity, but their correlations varied. Through the combination of optical methods and UPLC-Q-TOF spectrometry, the optical and molecular characteristics of rainwater are effectively revealed, which may provide a solid foundation for the classification management of stormwater runoff in different urban regions. 相似文献
512.
513.
In this study, we report the effects of pH and divalent cations on the adsorption of arsenate (As(V)) by titanium dioxide
(TiO2) nanoparticles. The extent of As(V) adsorption on TiO2 decreased with increasing pH due to the decrease of positively charged binding sites on the TiO2 surface. The Langmuir maximum uptake capacity at pH 4 is about three times higher than that at pH 7. Here we show that the
relatively low As(V) uptake at circumneutral pH could be substantially enhanced by the addition of common divalent cations
such as magnesium and calcium. At a concentration of approximately 7 mM, magnesium and calcium increased the extent of As(V)
adsorption from 2.1 to 6.5 and 7.7 mg As(V)/g TiO2, respectively. 相似文献
514.
浅谈我国旅游环境的开发与可持续发展 总被引:1,自引:0,他引:1
分析了目前我国旅游环境存在的主要问题,阐述了旅游环境开发与可持续发展的辨证关系,提出了实现我国旅游环境可持续发展的对策与建议。 相似文献
515.
为了解深圳市坪山新区环境空气质量现状,研究运用坪山新区PM2.5浓度数据,分析该区PM2.5的污染特征及气象条件对其的影响,坪山新区PM2.5浓度呈现了明显的季节变化、月变化特征,表现为秋冬季高、夏季低、春季居中的特点;PM2.5浓度最高出现在12月,最低出现在7月.该区PM2.5浓度日间变化呈双峰分布,7:00~9:00出现短期高峰,夜间21:00~次日4:00出现长期高峰.坪山新区PM2.5超标情况多出现在秋冬季及初春.在超标日期里,区域一般温度较低、风速较小,相对湿度也较低.污染源分析模型结果表明,坪山新区PM2.5的排放强度高值区主要集中在北部和西部,南部和东部排放强度稍低.由此可见,坪山新区大气环境亟待提升,需要针对区域内大气颗粒物污染进行有效防治. 相似文献
516.
上海市崇明岛公路两侧土壤重金属污染研究 总被引:4,自引:0,他引:4
采集了上海市崇明岛陈海、北沿公路两侧土壤和灰尘样品270余个,测定了样品的Pb、Cd、Cu、 Zn和Cr重金属含量。结果表明,陈海和北沿公路两侧土壤重金属Pb、Cd、Cu、 Zn和Cr的平均含量达到277、0279、258、918和776 mg/kg,土壤Cd污染较严重。采集的路面灰尘样品Pb、Cd、Cu、 Zn和Cr的平均含量达到512、049、489、209和970 mg/kg,超过土壤背景值2~4倍,是土壤重金属的主要二次污染源。公路防护林体系较差的北沿公路路侧土壤纵向剖面(垂直于公路走向)重金属含量随距路肩距离增加呈指数下降,土壤重金属重污染区在距路肩15 m范围内。防护林体系较完善的陈海公路距路肩15 m范围内土壤重金属污染较小,土壤重金属重污染区出现在距路肩20~50 m范围内。 相似文献
517.
518.
P.F.A.M. Römkens H.Y. Guo C.L. Chu T.S. Liu C.F. Chiang G.F. Koopmans 《Environmental pollution (Barking, Essex : 1987)》2009,157(8-9):2435-2444
Cadmium (Cd) levels in paddy fields across Taiwan have increased due to emission from industry. To ensure the production of rice that meets food quality standards, predictive models or suitable soil tests are needed to evaluate the quality of soils to be used for rice cropping. Levels of Cd in soil and rice grains were measured in 19 paddy fields across the western plains in Taiwan. Cadmium levels in soil range from less than 0.1 mg kg?1 to 30 mg kg?1. Measured Cd levels in brown rice were predicted very well (R2 > 0.8) based on Cd and Zinc in a 0.01 M CaCl2 extract or a soil–plant transfer model using the reactive soil Cd content, pH, and cation exchange capacity. In contrast to current soil quality standards used in Taiwan, such models are effective in identifying soils where Cd in rice will exceed food quality standards. 相似文献
519.
As intermediaries, some heterotrophic protists can enhance the content of the long chain n-3 essential fatty acids (LCn-3EFAs),
eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), of low food quality algae for subsequent use at higher trophic
levels. However, the mechanisms that produce LCn-3EFAs are presently unknown, although LCn-3EFA production by heterotrophic
protists at the phytoplankton–zooplankton interface may potentially affect the nutritional status of the pelagic system. We
investigated whether the heterotrophic protists, Oxyrrhis marina and Gyrodinium dominans, produce LCn-3EFAs via elongation and desaturation of dietary LCn-3EFA precursors and/or synthesize LCn-3EFAs de novo by:
(1) feeding the two heterotrophic protists with a prey deficient in n-3 fatty acids, (2) incubating them in medium containing
13C-labeled sodium acetate, and (3) feeding the two protists gelatin acacia microspheres (GAMs) containing a deuterium-labeled
LCn-3EFA precursor, linolenic acid [18:3(n-3)-d4]. Both O. marina and G. dominans synthesized EPA and DHA when fed the n-3 fatty acid-deficient prey, Perkinsus marinus, a parasitic protozoan. O. marina, but not G. dominans utilized 13C-labeled acetate from the medium to produce uniformly labeled fatty acids, including DHA. Both heterotroph species consumed
GAMs containing 18:3(n-3)-d4 and catabolized 18:3(n-3)-d4 to 16:3(n-3)-d4 and 14:3(n-3)-d4, while no 20 or 22 carbon metabolites
of 18:3(n-3)-d4 were detected. These results suggest that O. marina and G. dominans do not elongate and desaturate dietary LCn-3EFA precursors to produce LCn-3EFAs, but rather they produce LCn-3EFAs de novo,
possibly via a polyketide synthesis pathway. 相似文献
520.
Accumulation, distribution and transformation of DDT and PCBs by Phragmites australis and Oryza sativa L.: I. Whole plant study 总被引:1,自引:0,他引:1
Glasshouse experiments were conducted to determine the accumulation, distribution and transformation of o,p′-DDT, p,p′-DDT and PCBs by common reed (Phragmites australis) and rice (Oryza sativa L.) under hydroponic conditions. The culture solution was spiked with the organic pollutants and samples were collected daily. Analysis of the plants at harvest showed that both species had removed DDT and PCBs from the solution. DDT appeared to have accumulated within P. australis by both passive adsorption and active absorption. Both o,p′-DDT and p,p′-DDT were transformed within P. australis. DDD was the major metabolite and the transformation was mediated by reductive dehalogenation. Plant long-distance transportation systems may be involved in the translocation of PCBs within P. australis and the affinity of the PCBs for lipids is one of the major factors affecting their uptake and translocation within the plants. Similar but less pronounced results were found in O. sativa and suggest that these wetland plants may be used for the plant-mediated remediation of persistent organic pollutants. 相似文献