Sedimentary characterization of Tagus estuarine beaches (Portugal)

Background, Aim and Scope  The distribution of sediments in estuarine beaches is controlled by the interactions between sediment supply, hydrodynamic processes and human intervention. The main purpose of this study is to characterize the sediments of Tagus estuarine beaches in order to understand their origin and to contribute to a better knowledge of the Tagus estuary sediment budget. Methods  Surface sediment samples were collected across beach profiles and sand grain size analysis was performed by dry sieving. Grain size statistics for the median (d₅₀) and standard deviation (SDM) were obtained using the Moment method. This study was complemented by a qualitative evaluation of the sediment composition. Cross-shore topographic surveys were conducted for selected sampling sites. Results  Tagus estuarine beach sediments are mainly composed of quartz sand particles which are fine-grained and well sorted near the mouth of the estuary and medium to coarse-grained and moderately sorted in the inner domain. Compositional results show evidence of active anthropogenic sediment sources, especially in the coarser fractions. Discussion  The analysis of the textural and compositional characteristics of beach sediments in the inner estuarine domain is compatible with local sedimentary sources, while a marine signature is present at the mouth and inlet channel sediments. In the inner domain, differences in the sedimentary processes are represented by the textural characteristics of the sediments, such as the sorting degree and the gravel content. Sediment characteristics also reflect human intervention in the system, with the introduction of anthropogenic and allochthonous particles and the mixture of sediments from different sources. Conclusions  The sediments of the inner Tagus estuarine beaches are derived from local Plio-Pleistocene outcrops while inlet and outer estuary beaches reveal a dominant marine source. Beach textural variability observed in the inner domain is not related to wave forcing gradients, but mainly to variations in the sedimentary processes along the estuarine margins and to human intervention. Results show that the Tagus estuarine beaches depended, almost exclusively, on sediment input from local sources until the last century. With increasing human occupation, sediment transfers became dominated by anthropogenically related activities mainly connected with the occupation of estuarine margins and dredging. Recommendations and Perspectives  Further studies should extend the present level of knowledge in what concerns sand transport patterns through additional compositional and geochemical analysis, and the development of new techniques in order to allow the quantitative evaluation of the impact of human activities on the sediment budget.     

Composition,distribution and sources of polycyclic aromatic hydrocarbons in sediments of the western harbour of alexandria,egypt

Aim and Background  Little data are available on the levels of polycyclic aromatic hydrocarbons (PAHs) in the sediments of the Mediterranean Sea Coast of Egypt in general and the Alexandria coastal zone in particular. It was therefore deemed necessary to set up a monitoring programme to determine the current concentrations of PAHs in bottom sediments, and to identify any area where high concentrations of these potential hazardous contaminants were present in the Western Harbour of Alexandria. Methods  The composition, distribution and the source of PAHs in surficial sediments of the harbour were investigated. To document the spatial PAH input, surficial sediment samples from 23 locations throughout the harbour were analysed. as]Results and Discussion The total PAH load determined in the surficial sediment samples ranged from 8 to 131150 ng g¹ dry wt, generally with most of the samples having total concentrations of PAHs greater than 5000 ng g¹ dry weight. The highest concentration of total PAHs was recorded in sediments of the inner harbour. Ratio values of specific compounds such as phenanthrene to anthracene, fluoranthrene to pyrene, methyl-phen-anthrene to phenanthrene, methyl-dibenzothiophenes to dibenzothiophenes, alkylated to non-alkylated and high molecular weight to low molecular weight PAH, were calculated to evaluate the possible source of PAH contamination in the harbour sediments. Conclusions  Two main sources of PAH in the study area have been found: pyrolytic and petrogenic. Interferences of rather petrogenic and pyrolytic PAH contaminations were noticed for most samples. The dominant sources of PAH appear to be the combustion processes through run-off, industrial and sewage discharges, and atmospheric input. The concentrations of PAHs were generally above levels expected to cause adverse biological effects. Recommendations and outlook  Information from this study and any other relevant studies should be useful in designing future strategies for environmental protection and management of the harbour.     

不同锌源对断奶仔猪生长性能和血液指标的影响

试验选用杜洛克×长白×约克夏29日龄断奶仔猪27头,随机接受锌添加量同为100 mg/kg、但锌源来自无机锌(ZnSO4)和两种有机锌(Zn-AAC和Available Zn)的3种处理饲粮,研究不同锌源对断奶仔猪生长性能和血液指标的影响。试验结果表明:与ZnSO4比较,添加Zn-AAC和Available Zn显著提高了ADG和ADFI,FCR3个处理之间差异不显著(P>0.05);血清锌浓度有机锌与无机锌差异极显著(P<0.01),两种有机锌的血清锌浓度亦存在明显差异(P<0.05);不同锌源对血清IgG含量和血清ALP活性无明显影响(P>0.05)。断奶仔猪补饲常规剂量的锌氨基酸络合物,与ZnSO4比较,能够提高仔猪ADG和ADFI,增加血清锌浓度。     

不结球白菜抗病育种的研究 Ⅳ不结球白菜抗芜菁花叶病、霜霉病及黑斑病的多抗性鉴定及筛选

选取８４份经芜菁花叶病毒（ＴｕＭＶ）、霜霉病菌［Ｐｅｒｏｎｏｓｐｏｒａｐａｒａｓｉｔｉｃａ（Ｐｅｒｓ．）Ｆｒ．］、黑斑病菌［Ａｌｔｅｒｎａｒｉａｂｒａｓｉｃａｅ（Ｂｅｒｋ）Ｓａｃ．］单抗鉴定后筛选出的自交系，于１９９２～１９９３年对其进行上述３种病害苗期人工诱发接种多抗性联合鉴定，获得２１份三抗材料。经鉴定，确认为三抗抗源材料。探讨了多抗性联合鉴定的技术与方法。     

液体深层培养贵州绿僵菌分生孢子的研究

本文对贵州绿僵菌液体深层培养的研究表明，不同氮源对生长量、液生芽孢子和液生分生孢子产孢量影响显著．不同碳源对生长量和液生芽孢子产孢量影响显著，但对液生分生孢子产量无明显影响．同时试验还表明，液生分生孢子的形成与培养液的碳氮比、pH以及通气量有关．     

太湖水体富营养化与流域农业面源污染的控制

通过对太湖“零点行动”前后的水质状况进行分析和比较,发现虽然水质得到改善但尚不能控制富营养化趋势,提示了控制农业面源污染的紧迫性;进一步对环太湖流域重点农业面源污染源水肥流失和畜禽养殖业污染进行了研究与评价,分析了农业面源污染对太湖水体富营养化的影响,提出了农业面源污染的控制对策。     

地源热泵技术在中国温室设施中的应用探讨

当前在中国温室设施中应用和推广地源热泵技术尚存在诸多不利因素,大大限制了该项技术在设施农业领域中的发展。为探寻合理的解决途径,对地源热泵空调系统的关键技术和其在中国的发展概况进行了相关的阐述和分析,并以中国农业大学上庄实验站已经建成使用的地下水式温室地源热泵空调系统为实例,介绍该系统的组成、工作流程、性能参数和使用情况,探讨温室地源热泵空调系统在推广和使用中可能出现的投资较高,长时间运行性能不稳定等问题,分析其原因并提出相应的对策建议。     

适于玫烟色拟青霉液相发酵生产的培养基和初始接种量及pH

从美国引进对刺吸式口器害虫具侵染力的玫烟色拟青霉(Paecilomyces fumosoroseus)菌株Pfr116,用5种培养液在25 ℃下进行深层培养,以菌丝生物量作为指标筛选出了适合于工业生产的发酵液配方(w/v):食用蔗糖2%,马铃薯20%,蛋白胨0.1%,NaNO3 0.01%,KCl 0.01%,MgSO4 0.025%,MnSO4 0.005%,FeSO4 0.005%及KH2PO4 0.05%.用此培养液对Pfr116 菌株进行48 h的深层发酵,可获>20 mg/mL的干菌丝产量,与萨氏培养液的菌丝产量无显著差异.通过对液培初始接种量和pH值进行优化,确定最佳初始接种量为培养液的菌丝含量1.5 ～2.0 mg/mL,最佳初始pH值为5～7.     

茶树生态系中的立体污染链与阻控

 运用农业立体污染的新概念，针对茶树和茶叶本身的特点，剖析了来自土壤、水源、空气中性质各异的污染物，包括农药残留、铅、氟、铝、硝酸盐、多环芳烃（PAHs）、多氯代二苯并二恶英/呋喃（PCDD/PCDF）等，在水-土、土-气、土-植物等不同相或界面间的相互交换和迁移特性。论述了茶园生态系中的立体污染链以及污染物对不同界面的偏嗜性和界面间转移的时空特征，分析了中国茶叶生产中的立体污染问题。在对茶叶中几种污染物安全性风险评价的基础上，从清洁化生产角度，讨论了不同界面间污染源的控制和污染链防阻技术和应用，探讨了未来创新研究的重点领域。     

提高农民信息网络意识推动农业信息化建设

本文通过对农村信息网络建设及现状的认识和分析，提出了加速农村信息网络建设的一些措施和方法，并着重就农民利用网络信息的心理提出了很多个人见解。