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151.
152.
153.
Fengyu Zan Shouliang Huo Beidou Xi Xiulan Zhao 《Frontiers of Environmental Science & Engineering in China》2012,6(1):51-58
The biosorption of Cd2+ and Cu2+ onto the immobilized Saccharomyces cerevisiae (S. cerevisiae) was investigated in this study. Adsorption kinetics, isotherms and the effect of pH were studied. The results indicated
that the biosorption of Cd2+ and Cu2+ on the immobilized S. cerevisiae was fast at initial stage and then became slow. The maximum biosorption of heavy metal ions on immobilized S. cerevisiae were observed at pH 4 for Cd2+ and Cu2+. by the pseudo-second-order model described the sorption kinetic data well according to the high correlation coefficient
(R
2) obtained. The biosorption isotherm was fitted well by the Langmuir model, indicating possible mono-layer biosorption of
Cd2+ and Cu2+ on the immobilized S. cerevisiae. Moreover, the immobilized S. cerevisiae after the sorption of Cd2+ and Cu2+ could be regenerated and reused. 相似文献
154.
历史时期瘟疫的研究对现代瘟疫的防治具有重要的意义。本文选取陕西省为研究区域,在大量收集历史文献资料的基础上,初步考察了康熙三十至三十一年(1691—1692年)陕西瘟疫发生的情况,并着重分析了这次瘟疫爆发的相关原因。结果表明,干旱灾害、社会风俗、治疫政策等是瘟疫爆发的主要诱因。 相似文献
155.
Phosphorus is an important limiting nutrient in many ecosystems. Consequently, there is increasing interest on phosphate uptake and
algal growth due to the increasing frequency and magnitude of algal blooms induced by eutrophication. The co-existence of surface
adsorbed and intracellular phosphorus pools indicate that phosphate uptake by phytoplankton is, to some extent, a two-stage kinetic
process. However, almost all previous uptake models considered the internal uptake stage only and ignored the possible impact of
surface adsoption. In this article, a two-stage kinetic uptake model considering both surface adsorption and P-stress on phosphate
uptake by algae was constructed and compared to conventional one-stage models, based on experimental data on short-term uptake
kinetics of a green algae S. quadricauda. Results indicated that with suitable parameters, the two-stage uptake model not only fit
the experimental data better, but also gave more reasonable and realistic explanations to the phosphate uptake process. The results
are meaningful as surface-adsorption of phosphate may a ect the uptake process of phosphate and assist in understanding realistic
phosphate uptake kinetics in phytoplankton. 相似文献
156.
Yanli Cheng Ying Liu Mingqun Huo Qian Sun Huixiang Wang Zhongming Chen Yuhua Bai 《环境科学学报(英文版)》2011,23(8):1350-1358
To study the characteristics of precipitation in eastern China, an automatic sampler was used to collect rainwater samples from 19
precipitation events at Mangdang Mountain, Nanping City, Fujiang Province, in the spring of 2009. We used ion chromatography to
analyze the ionic components and concentrations, and inductively coupled plasma mass spectrometry (ICP-MS) to analyze element
compositions and contents. The results demonstrated remarkable acidic characteristics: in more than 80% of precipitation events the
pH was less than 5.6, with an average of 4.81. Mass concentration results showed SO4
2?? was the main anionic component (36.2%
of the total anion mass), while NH4
+ was the main cationic component (47.7% of the total cation mass) and main ion for acidity
neutralization in the rainwater. Organic acid content accounted for 30.9% of total anion mass. The main trace metals were Ca, K, and
Na. The SO4
2??/NO3?? ratio was 1.4, indicating that precipitation in this region was influenced by complex air pollution – the product of
individual coal-burning combined with vehicle exhaust pollution. Correlation analysis of the chemical composition of the precipitation
indicated that acidity in this region was determined by a combination of all acidic and neutralization ions rather than any single ion
component. The results also showed that Na+ and Cl?? contributions were mainly by seawater; Mg2+ by seawater and crustal materials;
the NH4
+, K+, Ca2+, NO3?? and SO4
2?? by anthropogenic sources; the trace metals were from the Earth’s crust; and organic acids were
potentially from combustion of biomass. 相似文献
157.
以稻田湿地中磷化氢为研究对象,采用室内模拟的方法,考察了不同浓度的磷化氢(0,1.4,4.2,7.0 mg·m-3)对水稻根际与非根际土壤的p H值、氧化还原电位、Fe2+、Mn2+、磷酸酶活性及有效磷的影响.结果表明:磷化氢导致根际土壤p H明显下降,非根际土壤中p H变化不明显.而氧化还原电位(Eh)则不同,磷化氢使水稻根际与非根际土壤的Eh均增大.磷化氢对Fe2+、Mn2+和碱性磷酸酶的影响具有相似性,磷化氢处理的前15 d,根际土壤中的Fe2+、Mn2+和碱性磷酸酶变化不明显,随着水稻的生长,根际土壤中的Fe2+和Mn2+随磷化氢浓度的增大而增加,随暴露时间的增加而减少;而根际土壤中的碱性磷酸酶随磷化氢浓度和暴露时间的增加而增加.非根际土壤中的Fe2+、Mn2+和碱性磷酸酶在磷化氢作用下变化不明显.水稻在磷化氢的环境影响下,根际与非根际土壤的有效磷含量都提高,表明一定浓度的磷化氢对土壤磷表现出活化效应. 相似文献
158.
为研究硝酸异辛酯在储存及运输过程中的危险特性,有效预防和减少事故的发生,按照危险货物分类测试程序,通过隔板、克南、时间压力、撞击、摩擦等试验对硝酸异辛酯的固有危险性进行了评价;利用热分析技术考察了不同温升速率、水及酸雨等条件对硝酸异辛酯的热分解特性的影响.结果表明:硝酸异辛酯在相对封闭空间内遇热量、火焰、爆炸冲击及外部的机械刺激条件下表现出轻微的燃爆危险性,但不足以将其按照爆炸品进行管理;随着温升速率的增加,硝酸异辛酯热分解起始放热温度也逐渐增大,而水和酸雨均对硝酸异辛酯的分解具有促进作用,与纯硝酸异辛酯相比,其反应起始放热温度分别降低了12.4℃和27.2℃,放热量分别增大了387.439J/g和568.076J/g,失控分解危险性大大增加. 相似文献
159.
160.
Spatial heterogeneity of lake eutrophication caused by physiogeographic conditions: An analysis of 143 lakes in China 总被引:1,自引:0,他引:1
Jingtao Ding Jinling Cao Qigong Xu Beidou Xi Jing Su Rutai Gao Shouliang Huo Hongliang Liu 《环境科学学报(英文版)》2015,27(4):140-147
In order to identify the effect of geographic characteristics on the variations of nutrient concentrations and the utilization efficiency of nutrients by phytoplankton, data from 143 lakes, from 2008 to 2010, including three very different types of topography, i.e., the first topography ladder(FTL), second topography ladder(STL), and third topography ladder(TTL), were statistically analyzed. Lakes in the FTL and STL, located at high elevation(above1000 m) and low longitudes(lower than 105° E), were sporadically oligotrophic, whereas lakes in the TTL were almost all mesotrophic and eutrophic. The trophic level index(TLI)became higher with the rise of longitude. Two turning points(5 and 15°C) on the curve of TLI as function of the average annual temperature(AAT) corresponded with the AAT in different lake regions in the STL and TTL. Because the responses of TLI to AAT differ significantly, there were variations of nutrient and algal biomass concentrations in different lake regions in the same type of topography ladder. According to the differences in utilization efficiency of total nitrogen or total phosphorus by phytoplankton, China could be partitioned into six lake regions. Scientific nutrient criteria for each lake region shall be established considering these differences in China. 相似文献