Influences of sediment properties and macrophytes on phosphorous speciation in the intertidal marsh

Phosphorus (P) in wetlands is mainly bound to sediment in various species, which is essential to predict water column P levels. The purpose of this work is to understand the influences of sediment properties and vegetation types on P speciation. Sediments under four vegetation types in the tidal flat and offshore sandbar in Hangzhou Bay of China were collected seasonally. The rank order of P species in sediment based on concentration was exchangeable P (Exch-P)?相似文献   

不同水肥管理对太湖流域稻田磷素径流和渗漏损失的影响

于2010和2011年在太湖流域开展了为期2年的田间定位试验,对2种灌溉模式(常规连续淹灌与干湿交替节灌)和4种施肥管理(不施氮、常规尿素、控释BB肥与树脂包膜尿素)条件下稻田田面水和渗漏水总磷(TP)、溶解态磷(DP)和颗粒态磷(PP)浓度的动态变化及磷素径流和渗漏损失进行了研究.结果表明:田面水TP和DP浓度变化趋势相同,均在施肥后1 d达到最高值,之后急剧下降;渗漏水TP和DP浓度变化趋势也相同,均在施肥后7 d达到最高值,然后逐渐下降.PP是田面水磷素的主要形态,DP是渗漏水磷素的主要形态.节灌降低了田面水和渗漏水磷浓度但对DP/TP影响不大,同时降低了TP径流流失量(24.7%~57.4%)和渗漏淋失量(21.0%~25.3%).施氮增加了田面水和渗漏水的磷浓度,也导致了更高的TP径流和渗漏损失.与常规尿素相比,控释BB肥提高了田面水和渗漏水的磷浓度及TP损失量,而树脂包膜尿素降低了田面水和渗漏水的磷浓度和TP损失量.综上,干湿交替节灌结合树脂包膜尿素施用能有效降低稻田磷素径流和渗漏损失,削减农业面源污染.     

温度环境试验及其标准综述(四)温度试验技术

<正>1温度试验设备和辅助仪器1.1对温度试验箱的要求温度试验设备包括高温箱、低温箱、高低温箱、温度冲击箱和快速温度变化箱。虽然都是用来产生温度条件,不同的温度试验项目对温度试验设备的要求有所不同。对试验箱的结构和参数要求也略有区别(见表1)但不管什么试验箱,它们都应能产生并保持试验方法标准中所规定的试验条件,并在规定的容差范围,以确保试验结果的重现性。1.2对辅助设备和仪器的要求     

APEC期间北京空气质量改善对比分析

为了评估APEC期间强化减排措施对北京空气质量的改善效果,利用2014年11月1~15日中国环境监测总站发布的奥体中心监测点空气质量监测数据,分析其空气质量演变特征,并与2013年同期监测数据进行对比研究.结果表明:1PM_(2.5)是当前北京最重要的污染物,APEC期间空气质量以优良为主,期间有3次明显的污染过程,与2013年同期相比较有所好转,显示出强化减排措施对北京空气质量的改善有显著的效果;2与世界卫生组织(WHO)的标准值相比,APEC期间PM_(2.5)有5d在WHO标准值(25μg·m~(-3))以下,而SO_2均小于标准值;3APEC期间,在空气质量为优时PM_(2.5)/PM_(10)小于0.5,且随污染浓度的增加比值逐渐增大,在严重污染情况下PM_(2.5)/PM10达到0.9以上;4与2013年同期相比,强化减排措施对PM_(2.5)的减少有一定的贡献,但与SO_2和CO的减少量相比,颗粒物的减少量又相对较少,NO_2减少量相对最小,实施强化减排措施对污染物减排的排序为SO_2COPMNO_2,说明北京空气污染中的PM_(2.5)的来源、影响和减排的复杂性,有待进一步深入研究.     

上海港区船舶防污漆中Irgarol 1051的环境风险评价

Irgarol 1051是一种常用于船舶防污漆的杀生活性物质。为了评价船舶防污漆杀生活性物质Irgarol 1051的海洋环境风险,根据ISO 13073-1的评价原则和程序,对其进行环境危害评价、环境暴露评价和风险表征。通过对公共数据库的文献检索获取数据,从理化性质、环境行为、生态毒性3个方面评价Irgarol 1051的环境危害。采用评估因子法计算Irgarol 1051的预测无效应浓度(PNEC)。采用质量守恒法计算Irgarol 1051在海水中的释放率,通过MAMPEC v3.0模型推导上海洋山深水港的集装箱船区、码头、航道等暴露场景的预测环境浓度(PEC)。经过比较上述暴露场景的风险商值(PEC/PNEC)发现,港口的海水相风险商值大于1,Irgarol 1051的环境风险需要关注。     

一起电力线路球头挂环断裂失效的事故分析

针对某电力线路上一起球头挂环断裂事故,通过外观检查、力学性能测试及金相组织检验等方法进行分析,找出事故原因并提出治理措施。金属检测和金相分析结果表明:受力异常是球头挂环失效的外因,显微组织异常是球头挂环失效的内因,内外因共同作用导致球头挂环断裂。     

Review on the study of mercury/silver ions-pyrimidine base pairs in DNA duplexes and their application in detection technology北大核心CSCD

Nucleic acids and their analogues are getting more and more attention. Metal-mediated base pairs as a kind of simple and functionalized nucleic acids in special positions have widened the scope of application of functional nucleic acids and their analogues. In this type of base pairs, the representative is the interaction between metal ions and pyrimidine bases, especially the research on thymine-Hg2+-thymine (T-Hg2+-T) and cytosine-Ag+-cytosine (C-Ag+-C) base pairs. This review summarizes the structure and mechanism of metal-mediate pyrimidine base pairs as well as the application in the biochemical analysis. It explores the mode and ratio of coordination between metal ions and base pairs, the effects on the stability of DNA helical structure, the related crystal structure and the three-dimensional configuration information in the DNA helix. The analytical application mainly includes various probes of metal ions, small molecules, protein and the detection of single nucleotide polymorphism. Among them the most widely used metal ions detection, and its combination with spectrum technology, visualization and amplification technology greatly promoted the rapid development of sensitive detection technology. In further studies, it is necessary to reveal the mechanism of interaction between T-Hg2+-T and C-Ag+-C, and more attention should be paid to combining of T-Hg2+-T and C-Ag+-C base pairs with other new technologies. The scope of practical application should also be further extended.     

Phosphorus speciation and effects of environmental factors on release of phosphorus from sediments obtained from Taihu Lake,Tien Lake,and East Lake

Phosphorus is considered the primary nutrient limiting eutrophication. The release of phosphorus from sediments not only provides hydrophytes with essential nutrients, but can also produce entrophication in lakes. In this study, the sediment characteristics, phosphorus speciation, and environmental factors affecting phosphorus release from sediments from Taihu Lake, Tien Lake, and East Lake were investigated. The results indicated that phosphorus levels of sediments ranged from 647 ± 67 to 2343 ± 122 mg/kg. Inorganic phosphorus comprised the majority of total phosphorus. The main phosphorus speciation of sediments obtained from Taihu Lake and Tien Lake was Residual-P, and the main phosphorus speciation of sediment obtained from East Lake was NaOH-P. Phosphorus release occurred in acidic and alkaline conditions but more frequently under alkaline conditions. The amount of phosphorus released from the sediments increased as the disturbing intensity rose. In addition, less phosphorus was released in natural than anaerobic conditions. The amount of phosphorus released was elevated as temperature increased.     

Growth and alkaline phosphatase activity of Chattonella marina and Heterosigma akashiwo in response to phosphorus limitation

The growth and alkaline phosphatase activity(APA) of two raphidophyceae species Chattonella marina and Heterosigma akashiwo were investigated in response to P-limitation and subsequent addition of dissolved inorganic phosphorus(DIP, Na H2PO4) and two dissolved organic phosphorus(DOP) compounds: guanosine 5-monophosphate(GMP) and triethyl phosphate(TEP). APA levels increased greatly after P-starvation as the decrease of the cellular phosphorus quotes(Qp). C. marina responded to P-limitation quickly and strongly, with 10-fold increase in APA within 24 hr after P-starvation. The larger difference between maximal and minimal QP values in C. marina indicated its high capacity in P storage. APA of H. akashiwo was maximally enlarged about 2.5 times at 48 hr of P-starvation. After the addition of nutrients, cell numbers of C. marina increased in all treatments including the P-free culture, demonstrating the higher endurance of C. marina to P-limitation. However, those of H. akashiwo increased only in DIP and GMP cultures. APA increased only after the addition of the monophosphate ester GMP. The results suggest that quick responses of C. marina to P-limitation, high capacity in P storage as well as endurance for P-depletion provide this species an ecological advantage in phytoplankton community competition under DIP-limited conditions.     

Vertical distribution of aerosol optical properties based on aircraft measurements over the Loess Plateau in China

Vertical distributions of aerosol optical properties based on aircraft measurements over the Loess Plateau were measured for the first time during a summertime aircraft campaign, 2013 in Shanxi, China. Data from four flights were analyzed. The vertical distributions of aerosol optical properties including aerosol scattering coefficients (σ_sc), absorption coefficients (σ_ab), Angström exponent (α), single scattering albedo (ω), backscattering ratio (β_sc), aerosol mass scattering proficiency (Q_sc) and aerosol surface scattering proficiency (Q_sc^′) were obtained. The mean statistical values of σ_sc were 77.45 Mm^− 1 (at 450 nm), 50.72 Mm^− 1 (at 550 nm), and 32.02 Mm^− 1 (at 700 nm). The mean value of σ_ab was 7.62 Mm^− 1 (at 550 nm). The mean values of α, β_sc and ω were 1.93, 0.15, and 0.91, respectively. Aerosol concentration decreased with altitude. Most effective diameters (ED) of aerosols were less than 0.8 μm. The vertical profiles of σ_sc,, α, β_sc, Q_sc and Q_sc^′ showed that the aerosol scattering properties at lower levels contributed the most to the total aerosol radiative forcing. Both α and β_sc had relatively large values, suggesting that most aerosols in the observational region were small particles. The mean values of σ_sc, α, β_sc, Q_sc, Q_sc^′, σ_ab and ω at different height ranges showed that most of the parameters decreased with altitude. The forty-eight hour backward trajectories of air masses during the observation days indicated that the majority of aerosols in the lower level contributed the most to the total aerosol loading, and most of these particles originated from local or regional pollution emissions.