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171.
172.
The comparative experimental study of inorganic mercury (HgII), methylmercury (MeHg) and cadmium (Cd) bioaccumulation in the Asiatic clam Corbicula fluminea was based on a 14 days' exposure to the water column or sediment compartments, as initial contamination sources. For each contaminant and exposure source, a five-point concentration range was set up in order to quantify the relationships between the contamination pressure and bioaccumulation capacity, at the whole soft body level and in five organs: gills, mantle, visceral mass, kidney and foot. Hg and Cd bioaccumulation at the whole organism level was proportional to the metal concentrations in the water column or sediment. For similar exposure conditions, the average ratios between the metal concentrations in the bivalves - [MeHg]/[HgII] and [MeHg]/[Cd] - were close to 10 and 5 for the sediment source and 8 and 15 for the water column source. Metal distribution in the five organs revealed strong specificities, according to the different contamination modalities studied: kidney and gills were clearly associated with Cd exposure, mantle and foot with MeHg exposure and the visceral mass with inorganic Hg exposure. 相似文献
173.
采用生物活性剂对无机粉体进行表面处理,利用碱性无机材料的吸水性能制备出含少量淀粉和碱性无机材料的光钙型可环境消纳聚乙烯制品,通过力学性能、ASTM生物降解性能和卫生性能等分析,结果表明,该制品达到了HJBZ12-2000标准中规定的包装制品的标准要求和生物降解率的技术要求. 相似文献
174.
Background, Aims and Scope Secondary inorganic aerosol (SIA), i.e. particulate sulphate (S(VI)), ammonium and nitrate (N(V)) is formed from gaseous
precursors i.e., sulfur dioxide (S(IV)), ammonia and nitrogen oxides, in polluted air on the time-scale of hours to days.
Besides particulate ammonium and nitrate, the respective gaseous species ammonia and nitric acid can be formed, too. SIA contributes
significantly to elevated levels of respirable particulate matter in urban areas and in strongly anthropogenically influenced
air in general.
Methods The near-ground aerosol chemical composition was studied at two stationary sites in the vicinity of Berlin during a field
campaign in summer 1998. By means of analysis of the wind field, two episodes were identified which allow to study changes
within individual air masses during transport i.e., a Lagrangian type of experiment, with one station being upwind and the
other downwind of the city. By reference to a passive tracer (Na+) and estimates on dry depositional losses, the influences
of dispersion and mixing on concentration changes can be eliminated from the data analysis.
Results and Discussion Chemical changes in N(-III), N(V) and S(VI) species were observed. SIA i.e., N(V) and S(VI), was formed from emissions in
the city within a few hours. The significance of emissions in the city was furthermore confirmed by missing SIA formation
in the case of transport around the city. For the two episodes, SIA formation rates could be derived, albeit not more precise
than by an order of magnitude. N(V) formation rates were between 1.4 and 20 and between 1.9 and 59 % h-1 on the two days,
respectively, and S(VI) formation rates were > 17 and > 10 % h-1. The area south of the city was identified as a source of
ammonia.
Conclusion The probability of occurrence of situations during which the downwind site (50 km downwind of Berlin) would be hit by an
urban plume is > 7.4%. Furthermore, for the general case of rural areas in Germany it is estimated that for more than half
of these there is a significant probability to be hit by an urban plume (> 8%). The S(VI) formation rates are higher than
explainable by homogeneous gas-phase chemistry and suggest the involvement of heterogeneous reactions of aerosol particles.
Recommendation and Outlook The possible contribution of heterogeneous processes to S(VI) formation should be addressed in laboratory studies. Measurements
at more than two sites could improve the potential of Lagrangian field experiments for the quantification of atmospheric chemical
transformations, if a second downwind site is chosen in such a way that, at least under particular stability conditions, measurements
there are representative for the source area. 相似文献
175.
176.
177.
山西省稷山和永济两地矮牡丹体内无机元素含量的比较 总被引:3,自引:0,他引:3
采用原子吸收分光光度法和比色法测定了山西省稷山和永济两地区矮牡丹体内和生境土壤中的10种元素(K、Mg、Mn、Fe、Ni、Zn、Cu、Cd、Cr、Pb),分析比较了各种元素在不同地区矮牡丹体内和生境土壤中的分布规律及不同地区矮牡丹对无机元素的吸收富集能力.结果表明,两地区矮牡丹体内和生境土壤中无机元素含量无显著性差异;土壤及植株不同器官间元素含量也无显著性差异;两地区矮牡丹对不同元素的富集系数有显著差异,差异主要表现在对Cd(永济0.457,稷山0.213)和Ni(永济0.093,稷山0.167)的富集上,植株不同器官之间的富集系数无显著差异.表4参9 相似文献
178.
施用化肥对农业生态环境的负面影响及对策 总被引:109,自引:9,他引:109
论述了肥料的过量使用对我国的农业生态环境质量的负面影响,提出了合理施用化肥防治环境污染的对策。认为过量施用化肥引起土壤酸化和板结、重金属污染、硝酸盐污染和土壤次生盐渍化,从而导致土壤肥力下降,并且造成水体富营养化,淋溶污染地下水,致使作物品质下降,硝酸盐含量超标,并通过食物链危害人体健康。此外,认为化肥对大气环境的影响主要集中在氮肥上,氨挥发和NOx、CH4及CO2的释放,不仅能引起温室效应,而且还能够引起臭氧层的破坏。提出了相应的对策:增加科技教育的投入,提高农民的科学文化素质,提高全民的环境意识;合理施肥;结合国家的调控政策,在粮食产量与环境保护、作物产量与产品品质之间找到平衡点。 相似文献
179.
无机分离膜与环境保护 总被引:15,自引:0,他引:15
本文综述了无机分离膜的制备方法及其在环境保护领域中的应用现状,并对无机分离膜在工业废水和工业废气治理中的应用前景进行了展望。 相似文献
180.
《环境科学学报(英文版)》2023,35(4):408-422
A series of organic compounds were successfully immobilized on an N-doped graphene quantum dot (N-GQD) to prepare a multifunctional organocatalyst for coupling reaction between CO2 and propylene oxide (PO). The simultaneous presence of halide ions in conjunction with acidic- and basic-functional groups on the surface of the nanoparticles makes them highly active for the production of propylene carbonate (PC). The effects of variables such as catalyst loading, reaction temperature, and structure of substituents are discussed. The proposed catalysts were characterized by different techniques, including Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy/energy dispersive X-ray microanalysis (FESEM/EDX), thermogravimetric analysis (TGA), elemental analysis, atomic force microscopy (AFM), and ultraviolet–visible (UV-Vis) spectroscopy. Under optimal reaction conditions, 3-bromopropionic acid (BPA) immobilized on N-GQD showed a remarkable activity, affording the highest yield of 98% at 140°C and 106 Pa without any co-catalyst or solvent. These new metal-free catalysts have the advantage of easy separation and reuse several times. Based on the experimental data, a plausible reaction mechanism is suggested, where the hydrogen bonding donors and halogen ion can activate the epoxide, and amine functional groups play a vital role in CO2 adsorption. 相似文献