Variations of Soil Nutrient and Organic Matter Content in a Subtropical Mangrove Ecosystem   总被引：1，自引：0，他引：1  

Tam  N. F. Y.  Wong  Y. S. 《Water, air, and soil pollution》1998,103(1-4):245-261

Variations of soil nutrient and organic matter content along tidal gradients of a small mangrove forest in Hong Kong were investigated. Effects of sampling months on nutrient status were also analysed. Two transects, A and B, were established perpendicular to the shoreline. Transect A transverse a wider band of vegetation and was less disturbed by human activities; while Transect B was close to human settlement and all mangrove plants were more frequently flooded by incoming and outgoing tides. Surface soils at 5 and 10 m intervals along Transects A and B, respectively, were collected in December 1989, March 1990, July 1990 and September 1990. Concentrations of soil organic matter, total and extractable nitrogen, phosphorus and potassium were high in landward sites and decreased gradually along tidal gradients; while pH and salinity increased with distance from landward to seaward sites. These trends along tidal gradients indicate the importance of tidal frequency and amplitude on soil properties. Significant differences in soil properties were also found between two transects. Transect A had significantly higher organic matter and nutrient content than Transect B. In both transects, there were sites with extraordinarily high levels of nutrients and organic matter (5–10 times higher than the average values) suggesting local contamination. Most of these contaminated sites were located at the landward edges. Positive correlations between organic matter, N, P and K content were found suggesting that these nutrients were from similar input sources. Variations along tidal gradients and local contaminated sites at the landward edges suggest that human discharges, litter deposition and surface runoff were major nutrient inputs. In both transects, no definite seasonal periodicity was found and temporal variations existed in a more random manner than variations along tidal gradients.  相似文献   

Effects of Landfill Gas on Growth and Nitrogen Fixation of Two Leguminous Trees (Acacia Confusa,Leucaena Leucocephala)     

Chan  Y. S. G.  Wong  M. H.  Whitton  B. A. 《Water, air, and soil pollution》1998,107(1-4):409-421

A study was made on the effects of landfill gas on ARA (acetylene reducing activity) of nodules of two woody legumes (Acacia confusa and Leucaena leucocephala) widespread on landfill sites in Hong Kong. The effects of the three main components of landfill gas, O₂, CO₂ and CH4, were first measured separately over a 1-hr period. Maximum ARA was found at 20% O₂ (close to atmospheric partial pressure) and ARA decreased as the O₂ decreased in the range of 16–1%. Acacia confusa nodular ARA was significantly inhibited at 30–50% CO₂, but not Leucaena leucocephala nodular ARA. CH₄ had no significant effect on ARA of either species. As the landfill gas concentrations in the landfill topsoil were mostly > 10% O₂ and < 10% CO₂, root nodules should fix N₂ effectively over these ranges of gases. A four-week test was conducted to assess the long-term influence of landfill gas on seedlings of the two legumes. Landfill gas and elevated CO₂ both suppressed their growth and their nodular ARA. Even under the influence of the gases, however, seedlings with nodules formed a higher biomass than seedlings lacking nodules. The growth of the two legumes under actual landfill conditions was investigated by transplanting non-inoculated and pre-inoculated seedlings to two landfill sites in Hong Kong: Junk Bay and Shuen Wan Landfill. After six months, most of the non-inoculated seedlings became infected: Acacia confusa 63 and 70%, Leucaena leucocephala 17 and 89%, respectively, at the test sites. The results indicate that there were free rhizobia at these landfill sites to infect the legumes and they had formed effective nodules to fix N₂ under landfill conditions.  相似文献   

Femtosecond dynamics of electron localization at interfaces     

N Ge  CM Wong  RL Lingle  JD McNeill  KJ Gaffney  CB Harris 《Science (New York, N.Y.)》1998,279(5348):202-205

The dynamics of two-dimensional small-polaron formation at ultrathin alkane layers on a silver(111) surface have been studied with femtosecond time- and angle-resolved two-photon photoemission spectroscopy. Optical excitation creates interfacial electrons in quasi-free states for motion parallel to the interface. These initially delocalized electrons self-trap as small polarons in a localized state within a few hundred femtoseconds. The localized electrons then decay back to the metal within picoseconds by tunneling through the adlayer potential barrier. The energy dependence of the self-trapping rate has been measured and modeled with a theory analogous to electron transfer theory. This analysis determines the inter- and intramolecular vibrational modes of the overlayer responsible for self-trapping as well as the relaxation energy of the overlayer molecular lattice. These results for a model interface contribute to the fundamental picture of electron behavior in weakly bonded solids and can lead to better understanding of carrier dynamics in many different systems, including organic light-emitting diodes.  相似文献   

牛奶蛋白的免疫潜能     

C.W.Wong  狄伯雄 《中国兽医杂志》1999,25(1):48-49

１导言随着蛋白分馏技术的进步,大规模生产多种高纯度牛奶蛋白和多肽已成为现实。其结果是许多国家,特别是奶牛业具有经济重要性的国家,利用牛奶蛋白作为用于食品和生物制药工业的天然化合物的兴趣正在高涨。本文扼要介绍牛奶蛋白免疫特性的一些重要发现。２食物牛奶蛋...  相似文献   

Tissue distribution of a peptide transporter mRNA in sheep, dairy cows, pigs, and chickens.   总被引：8，自引：0，他引：8  

H Chen  E A Wong  K E Webb 《Journal of animal science》1999,77(5):1277-1283

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Conservation of freshwater wildlife in Hong Kong: A genetic perspective     

Wai Yee Wong  Lai Him Chow  Tsz Huen Wu  Ka Yan Ma  Ling Ming Tsang  Ka Hou Chu 《水产资源保护:海洋与淡水生态系统》2019,29(12):2204-2218

Nutritional Composition and Thermal Properties of Goldstripe Sardinella (Sardinella gibbosa) Fillets and By-Products     

Tengku Mohamad Tengku-Rozaina  Wong Shu Jeng  Mat Amin Amiza 《Journal Of Aquatic Food Product Technology》2018,27(6):667-679

Fish is a nutritious food for the whole family and a good source of protein and n-3 fatty acids. The fish-processing industry produces tonnes of fish-processing waste and by-products annually. Disposal of untreated by-products of the fish-processing industry may cause environmental pollution. Sardinella gibbosa or goldstripe sardinella is commonly used in surimi and fish cracker productions in Malaysia. However, data on the nutritional composition of goldstripe sardinella fillets (GSF) and by-products (GSB) remain limited. The objectives of this study are to determine the nutritional composition and thermal properties of fillets and by-products of S. gibbosa. Results showed that the protein and moisture contents of GSF were higher than GSB. Conversely, the ash and fat levels of GSF were lower than GSB. Levels of saturated fatty acids (SFA) in GSF and GSB were higher than monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids. Palmitic acid and oleic acid were the major SFA and MUFA found in GSF and GSB. Both GSF and GSB contain higher percentages of DHA and EPA. Melting and crystallization profiles of the oil from S. gibbosa fillets were similar to by-product oil, which was related to their fatty acid content.  相似文献   

Solar Photocatalytic Mineralization of Dye New Coccine in Aqueous Phase Using Different Photocatalysts     

Wan Fadhilah Khalik  Li-Ngee Ho  Soon-An Ong  Yee-Sian Wong  Nik Athirah Yusoff  Fahmi Ridwan 《Water, air, and soil pollution》2016,227(4):118

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Cloning of a novel phytase from an anaerobic rumen bacterium,Mitsuokella jalaludinii,and its expression in Escherichia coli     

TAN Wan-qin  Phang Chiun Yee  Sieo Chin Chin  Yiap Beow Chin  Clemente Michael Wong Vui Ling  Norhani Abdullah  Son Radu  Ho Yin Wan 《农业科学学报》2015,14(9):1816-1826

The full length phytase gene of Mitsuokella jalaludinii was successfully cloned and was found to be 1 047 bp in length, with 348 amino acids, and was designated as PHY7 phytase gene. A comparison of the sequence of PHY7 phytase gene of M. jalaludinii with various microbial phytase gene sequences showed that it was not similar to those from other bacteria except Selenomonas ruminatium, thus suggesting that they may both express a new class of phytase. The PHY7 phytase gene was subsequently subcloned into bacterial expression vector, p ET32 a, for expression in Escherichia coli strain Rosetta-gami. Expression of the recombinant phytase gene was optimised and characterised. The recombinant phytase was estimated to be approximately 55 k Da by SDS-PAGE analysis. The recombinant phytase exhibited optimum activity at 55°C, p H 4.5 and showed good p H stability from p H 3.5 to 5.5(78% relative activity). Metal ions such as Ca2+, Mg2+, and K+ were found to exert significant stimulatory effect on the recombinant phytase activity while Cu2+, Fe3+, and Zn2+ greatly inhibited the enzyme activity. The recombinant phytase showed moderate resistance to trypsin proteolysis, but susceptible to pepsin proteolysis. The results of the study showed that several characteristics of recombinant phytase were slightly different from the native enzyme. Unfavourable characteristics such as reduced p H stability and metal ion effects should be taken into consideration during feed enzyme formulation.  相似文献   

Rapid testing methods for food contaminants and toxicants     

Jiachi Chiou  Arthur Ho Hon Leung  Hang Wai Lee  Wing-tak Wong 《农业科学学报》2015,14(11):2243-2264

Food safety is one of the major concerns in every country regardless of the economic and social development. The frequent occurrence of food scandals in the world has led the Chinese government to implement several strategies to fortify the food supply system to a high food safety standard. This relies heavily on laboratory testing services but conventional methods for detection of food contaminants and toxicants are limited by sophisticated sample preparation procedures,long analysis time,large instruments and professional personnel to meet the increasing demands. In this review,we have incorporated most of the current and potential rapid detection methods for many notorious food contaminants and toxicants including microbial agents,toxic ions,pesticides,veterinary drugs and preservatives,as well as detection of genetically modified food genes and adulterated edible oil. Development of rapid,accurate,easy-to-use and affordable testing methods could urge food handlers and the public to actively screen for food contaminants and toxicants instead of passively relying on monitoring by the government examination facility. This review also provides several recommendations including how to encourage the public to engage in the food safety management system and provide optimal education and financial assistance that may improve the current Chinese food safety control system.  相似文献