降雨径流时农田沟渠水体中氮、磷迁移转化规律研究

为有效阻控降雨条件下农田土壤流失氮、磷通过沟渠进入水体,通过对降雨时农田排水沟渠系统中总氮、总磷的测定和分析,研究降雨径流下沟渠系统水体中氮、磷的迁移转化规律和时空分布.结果表明,农田排水沟渠系统本身不太稳定,在外界条件(降雨)的作用下可以引起一系列的变化,同时农田排水沟渠系统又具有抗冲击可修复能力,可以使氮、磷的各项转化作用恢复.该特征使得总氮、总磷在沿程迁移过程中表现出一定的变化规律:总氮浓度沿程呈3次多项式曲线变化,总磷浓度整体呈指数递减变化;同时各断面的总氮、总磷自身转化也有其降解规律,总氮和总磷浓度随时间均呈3次多项式曲线变化.     

西苕溪流域沉积物及土壤对磷吸附/解吸特性研究

以赋石水库和其上游河道沉积物以及流域内代表性水稻土为对象,通过分析其理化性质,改变上覆水磷浓度和pH的方法探讨沉积物和土壤对磷吸附/解吸的影响。结果表明:(1)沉积物内较高的磷含量,导致吸附/解吸平衡浓度较高,因此在水库和水体中起着磷"源"的作用;(2)土壤最大磷吸附量为566.45mg/kg,远大于沉积物的吸附量,同时吸附/解吸平衡浓度较低,因此在治理湖泊富营养化时,要加大水土保持的力度,尽量减少作为最主要污染源的农田土壤磷素流入水体;(3)无论上覆水中磷浓度升高还是降低,在未达到吸附/解吸平衡浓度前,土壤和沉积物会持续释放磷,故应把水体治理的重点放在降低土壤和沉积物的磷含量上;(4)上覆水的pH对样品的磷吸附和释放都有显著的影响。在酸性(pH3)或碱性(pH9)环境下,样品的磷吸附量均急剧下降,而水体酸化更易导致平衡后上覆水磷浓度的降低。     

黄河兰州段消落带表层沉积物对磷的吸附

为探究黄河消落带表层沉积物对磷的吸附特征,基于吸附动力学、吸附热力学及单因子实验,现场采集黄河(兰州段)消落带表层沉积物进行实验室模拟研究。结果表明：沉积物对磷的吸附动力学经历快速吸附、慢速吸附、吸附平衡3个阶段,扰动条件下,在10 min内吸附量达到最大吸附量的85%以上,480 min达到吸附平衡;沉积物对磷的吸附符合Langmuir吸附等温方程,随着温度的升高最大理论吸附量Q_m随之增加,25℃时Q_m达到119.831 mg·kg^-1;单因子实验中,扰动频率增加对磷的吸附量具有明显的促进作用;pH为7～8时沉积物吸附效果最佳,偏酸性条件次之,偏碱性条件下吸附效果较差;增大上覆水KH₂PO₄浓度,吸附量增加,吸附率整体呈下降趋势。由此可知,黄河消落带表层沉积物对磷元素具有一定的拦截效应,河水的扰动能够促进沉积物对PO₄^3--P的吸附,但是水体的pH值变化及高浓度陆源污染物均会削弱消落带对磷元素的吸附拦截作用。该研究结果可为黄河上游的...     

阳宗海沉积物中磷的稳定性

絮凝剂(Fe Cl3)治理阳宗海砷污染的过程中,水体中的磷被大量沉积进入底泥,弄清其是否会在环境条件变化后发生反溶形成二次污染对湖泊富营养化防治具有重要意义。通过模拟实验模拟泥-水界面p H变化、物理扰动和微生物活动的变化,旨在分析这些环境因子变化对沉积物中磷溶出的影响。结果表明,阳宗海水体在目前这种磷浓度下,底泥的磷会随时间的增加而溶出再次造成水体磷污染,当暴露在清洁水条件下时磷的释放率会增加;这种由于絮凝剂吸附沉淀到湖底的磷,在上覆水p H增加0.5时底泥磷解吸附释放速率增加;每年秋季湖泊上下层水的交换活动会造成水体磷浓度的季节性升高,形成不可忽视的磷内源。而夏季水温分层导致湖泊底部厌氧,使厌氧微生物活性增强,这将进一步促进底泥中磷的释放。     

城市道路沉积物氮、磷溶出特性

国内外众多研究表明,城市不透水表面沉积物是雨水径流中污染物的重要来源。以北京市某道路沉积物为研究对象,对城市道路沉积物的粒径分布进行了分析,并通过批量实验,研究了不同粒径道路沉积物中氮、磷营养物及有机物(COD)的溶出特性。实验结果表明,粒径较大的沉积物中氮含量较高,而粒径较小的沉积物中磷含量较高;虽然TP、PO3-4、TN、NO-3、NH+4、COD的溶出浓度、溶出速率变化特征各不相同,但总体趋势是粒径越小氮、磷及COD溶出浓度和溶出速率越大,且最大溶出速率都出现在前5 min。因此,为实现对城市雨水径流污染的有效控制,应采用源头控制措施对小粒径道路沉积物和初期雨水进行有效控制。     

赤泥在控制沉积物磷释放中的应用研究

利用烧结法赤泥中富含Ca、Fe等金属元素的氧化物而具有吸附性的特点,通过室内模拟研究赤泥投加对沉积物中各种磷形态含量及分布比例的影响,进而探讨利用赤泥控制沉积物中磷释放的可行性。对经过处理后的沉积物磷形态分析后表明,投加赤泥能促使沉积物中铁铝磷向钙磷转化（Pearson相关分析,r=-0.892,P<0.01,n=9）,且赤泥的强碱性使沉积物pH值逐渐升高。确定了赤泥最佳投加比例为5%,此时沉积物的pH为9.03,铁铝磷含量由初始的148 mg/kg降至107 mg/kg,占总磷比例也由18.1%降至13.4%,钙磷含量由486 mg/kg升至546 mg/kg,其占总磷比例则由60%增至68.7%,铁铝磷和钙磷之间的转化已基本完成,继续增加赤泥投加量对沉积物中磷形态间的相互转化影响甚微。由于铁铝磷较钙磷活性高而易释放,可见投加赤泥能降低沉积物中磷的释放风险。赤泥可以作为吸附材料被应用于沉积物磷污染控制技术中,为有效控制水体内源磷负荷提供一种新思路和廉价材料。     

三垟湿地沉积物-间隙水-上覆水界面磷形态研究

沉积物与上覆水间营养物质交换,成为导致水体发生富营养化的首要化学变迁过程.分别在三垟湿地的柑橘林(S1)、景观用地(S2)和生活用地(S3)取样,研究了沉积物-间隙水-上覆水界面磷形态以及相互关系.结果表明:(1)沉积物TP增加时,间隙水PO3-4和可溶性总磷(TDP)也增加.要削减磷在上覆水中的含量,控制间隙水PO3-4或TDP是一良策.(2)随着沉积物铁磷、铝磷的增加,间隙水PO3-4也增加.在三垟湿地沉积物中,铁磷和铝磷含量都可作为间隙水PO34-含量的指示.(3)S1、S2和S3的沉积物活性磷、间隙水TDP和上覆水TDP存在明显的浓度梯度,沉积物活性磷＞间隙水TDP＞上覆水TDP.说明在三垟湿地中,沉积物活性磷是磷释放的关键因子,而沉积物-间隙水界面则是磷释放的关键界面.     

汪洋沟表层沉积物中总氮含量和氨氮释放特征

对汪洋沟6个样点沉积物样品的总氮含量以及沉积物中NH4+-N的释放动力学特征、释放潜能进行了研究.结果表明,汪洋沟沉积物中总氮含量在0.368 ～ 2.036 g/kg之间,平均值为1.037 g/kg.NH4+-N最大释放量在0.258～0.705 g/kg之间,释放主要集中在0～5 min内,约占最大释放量的79％ ～ 84％;随后释放速率逐渐放缓,到120 min后基本达到释放平衡.运用无限稀释法对沉积物NH4+-N释放潜能进行测定表明,汪洋沟沉积物NH4+-N释放潜能在0.351～0.706g/kg之间,在水土质量比约为2 500时,NH4+-N释放量达到最大,随后释放逐渐趋于平衡.汪洋沟沉积物NH4+-N释放潜能及最大释放量与总氮含量呈正相关.汪洋沟沉积物中总氮含量与NH;-N释放潜能低于洱海,与长江中下游湖泊相近,汪洋沟沉积物氨氮释放存在一定的风险.     

河道沉积物中磷的分布、吸附及释放规律研究

为科学评价磷在河道沉积物中的环境行为,在模拟条件下研究了上海市进木港和苏州河沉积物中磷的分布形态、吸附特征及释放规律.结果表明:(1)2种沉积物中碎屑钙磷(De-P)浓度最高,闭蓄态磷(Oc-P)次之,其他形态磷浓度相对较低,而活性磷中以铁磷(Fe-P)为主;(2)2种沉积物对磷的吸附均符合线性方程,在4.0h时基本达...     

河岸带土壤对不同pH雨水中截留磷的影响

通过河岸带土柱淋滤模拟实验,研究了不同pH值模拟雨水条件下河岸带土壤对雨水中磷的截留效应,分析了pH对河岸带土壤吸附磷素的影响机制。结果表明:在不同pH的模拟雨水处理下,河岸带土壤对TDP和MRP的吸附具有显著的差异;且在pH=5条件下河岸带土壤对磷素的吸附量最低。河岸带土壤对雨水中磷的去除率随着降雨时间的进行而不断下降,pH=5时,河岸带对磷的去除率最低,截留能力最弱。不同pH值的模拟雨水对土柱中TP的含量产生显著影响,pH=5时,土柱中TP含量最高,pH=3时,TP含量最低。土柱中的TP在表层10 cm含量最高,随深度的增加而不断降低。研究河岸带土壤对不同pH雨水中磷的截留效应对于理解磷在河岸带土壤中的迁移转化机理以及防治水体富营养化具有十分重要的意义。     

Optimization of Height of Release of Air Pollutants

A number of key projects in the Environmental Protection Agency (EPA) particulate R&;D program having applicability to industry are presented. For electrostatic precipitators (ESP) there is presented the result of work on large diameter discharge electrodes which provide a decrease in penetration of up to a factor of 4 when compared to conventional small diameter electrodes. Also discussed is the multistage ESP which provides a collection efficiency that would require a collecting plate area 4 or 5 times larger with conventional ESP technology. The E-SOX technology makes use of the multistage concept to free up space in the ESP for SO₂ removals of up to 90%. Electrostatically augmented fabric filtration provides a reduction in pressure drop of about 5 0% as compared to conventional fabric filtration. Wind tunnel modeling of windbreaks for material storage piles indicates a potential for providing engineering design data that would allow significant emission reduction caused by wind erosion     

Investigation of the characteristics of the reflectivity of clouds

This paper investigates some of the reflectivity characteristics that clouds (when modelled as solid bodies) must exhibit to be compatible with observations that the reflecting surface of a cloud (i) appears almost equally bright across its face, (ii) is brightest when the cloud is opposite to the Sun but decreases in brightness as the cloud moves to other positions and (iii) increases in brightness with increasing optical thickness of the cloud in the observer's line of sight. These observations, respectively, are shown to imply that the peak value of the bidirectional total reflectivity from a cloud surface (i) increases in inverse proportion to the cosine of the angle between the Sun and the normal to the cloud surface, as the incident angle increases, (ii) appears to be directed back in the direction of the incident radiation, and (iii) increases as optical thickness of the cloud in the observer's line of sight increases. The results could have application in many fields (e.g. modelling diffuse radiance distributions for cloudy skies).     

Estimation of uncertainty of sampling for analysis of pesticide residues

Abstract

A computer model was used to take random samples from primary sample populations obtained from field trials to simulate the uncertainty of sampling for residue analysis of plant commodities and soil. The results indicate about 40%, 30% and 20% relative uncertainty when random samples of size 5, 10 and 25 are taken respectively, from a single lot. Therefore the sample size should be the same for establishing and enforcing legal limits.     

扬中生态环境建设的思考与实践

结合扬中生态环境的基本情况和存在的不足，进行了具体分析，对扬中未来生态建设的发展方向提出了建议及实施措施。     

实验室质量管理体系内部审核的实施

在实施ISO／IEC17025：1999标准《检测和校准实验室能力的通用要求》过程中，通过实验室质量管理体系内部审核的实践与系统分析，识别出内部审核实施阶段的关键环节，提出召开首次会议、收集审核证据、确定审核发现和召开末次会议的技术方法，对提高内部审核的质量和有效性、获得可靠的审核结论具有重要意义。     

次氯酸钠发生器的研制

介绍了电解法生产次氯酸钠的原理 ,并在原有生产工艺的基础上进行了重新设计和对设备的重新选择、改造 ,得出了各个工艺参数的最佳值 ,生产出高品质的次氯酸钠     

An application of the theory of kinematics of mixing to the study of tropospheric dispersion

The most common technique used for numerical simulations of tracer mixing is that of the numerical solution of the advection–diffusion equation with the unresolved fluxes parameterized using the similarity theory. Despite correct predictions of the overall directions of transport, models based on a numerical solution of the advection–diffusion equation lack sufficient accuracy to correctly reproduce the coupling of mixing with small scale processes which are sensitive to the microstructure of the tracer distribution. The objective of this paper is to revisit the basic formalism employed in numerical models used to investigate atmospheric tracers. The main mathematical method proposed here is the theory of kinematics of mixing which could be applied effectively for simulations of atmospheric transport processes. At the beginning of the paper, we introduce simple mathematical transformations in order to demonstrate how complex topological structures are created by mixing processes. These idealistic flow systems are essential to explain transport properties of much more complex three-dimensional geophysical flows. An example of the application of the kinematics of mixing to the analysis of tracer transport on a planetary scale is presented in the following sections. The complex filamentary structures simulated in the numerical experiment are evaluated using some commonly applied statistical measures in order to compare the results with the data published in the literature. The results of the experiment are also analysed with the help of simple conceptual models of fluid filaments. The microstructure of the tracer distribution introduced in the paper is essential to increase our understanding of atmospheric transport and to develop more realistic parameterizations of small-scale mixing. The presented results could also be used to improve calculations of the coupling between microphysical processes and tracer mixing.     

Impact of overexploitation of shellfish: northeastern coast of India

India has a very extensive coastline of about 7515 km, rich in diverse living resources. These resources continue to deteriorate with rampant harvesting or are altered for other uses such as aquaculture and fisheries. The present paper deals with degrading coastal habitats in northeastern India, and projects the intensity of the stress arising from the collection of tiger prawn seeds (Penaeus monodon) for aquacultural farms and molluskan shells for poultry feed and edible lime. Indiscriminate exploitation of these resources leads to a heavy reduction of the species concerned and other associated marine communities. The magnitude of such destruction has been quantified. The impacts of biodiversity loss and their after-effects on the ecobalance of this coastal system have become a matter of great concern to ecologists to maintain security and sustainability. The authors propose a public awareness program on themes relating to the importance of biodiversity for human livelihoods.     

Comparison of methods for evaluation of activity of photocatalytic films

Objective

This work aims to investigate the correlation between the photocatalytic activity determined by methylene blue bleaching (DIN 52980), stearic acid degradation, and degradation of acetone in gas phase.

Method

The photocatalytic TiO₂ coatings included in this investigation ranged from thin commercially available coatings (Activ^TM and BioClean^TM) and ready to use suspensions (Nano-X PK1245) to lab-produced PVD and sol?Cgel coatings. XRD analysis of the photocatalytic coatings showed that all the coatings consisted of nanocrystalline anatase, although the thickness and porosity varied considerably.

Results

The study showed that the reproducibility of the activity measurements was good. However, more importantly, the investigation showed that there is a good correlation between the activities determined by the different methods even though the characteristics of the photocatalytic coatings and the organic probe molecules varied considerably.

Conclusion

The overall findings of this work suggest that there is a good correlation between the investigated methods. These results are promising for the future work concerning standardization of methods for determination of the activity of photocatalytic films.