药物清塘方法种种

所谓药物清塘，是利用药物杀死野杂鱼、敌富生物和鱼体的寄生虫、病原菌等，为池塘养殖中心不可少的生产环节之一。目前我国的药物清塘方法很多，下面笔者综述常见几种，以飧读者。

Inorganic Phosphorus Fractions and Phosphorus Availability in a Calcareous Soil Receiving 21-Year Superphosphate Application

A long-term （21-year） field experiment was performed to study the responses of soil inorganic P fractions and P availability to annual fertilizer P application in a calcareous soil on the Loess Plateau of China. Soil Olsen-P contents increased by 3.7, 5.2, 11.2 and 20.6 mg P kg-1 after 21-year annual fertilizer P application at 20, 39, 59, and 79 kg P ha-1, respectively. Long-term fertilizer P addition also increased soil total P and inorganic P （Pi） contents significantly. The contents of inorganic P fractions were in the order of Ca10-P 〉 Cas-P 〉 Fe-P 〉 A1-P 〉 occluded P 〉 Ca2-P in the soil receiving annual fertilizer P application. Fertilizer P application increased Cas-P, A1-P and Ca2-P contents as well as their percentages relative to Pi. Pi application increased Fe-P and occluded P contents but nor their percentages. Soil Ca10- P content remained unchanged after fertilizer P application while its percentage relative to Pi declined with increasing fertilizer P rate. All Pi fractions but Ca10-P were correlated with Olsen-P significantly. 90% of variations in Olsen-P could be explained by Pi fractions, and the direct contribution of Cas-P was predominant. Long-term annual superphosphate application would facilitate the accumulation of soil Cas-P, and thus improve soil P availability.

Assessment of noise and ground vibration induced during blasting operations in an open pit mine——A case study on Ewekoro limestone quarry,Nigeria

Our study was carried out to assess the level of noise generated and ground vibrations induced during blasting operations at the Ewekoro limestone quarry in Nigeria.To achieve this objective,vibro monitor equipment was used to take readings related to noise generated and ground vibrations during all blasting operations that took place in the quarry for a period of one month.As well,a digital camera was used to take photographs of residential structures within villages near the quarry.The results obtained indicate that the ground vibration readings fall between 0.5 mm/s and 2.1 mm/s and the noise generated during the blasting operations between 82 dB and 89 dB.These readings when compared with the limits set by FEPA(Federal Environmental Protection Agency) of 5.0 mm/s and 150 dB) all fall within the permissible limits.However the photographs of most structures near the quarry reveal cracks and dilapidated building walls.Recommendations are made on how to sustain and improve current blasting techniques.

Dechlorination Behavior of Mixed Plastic Waste by Employing Hydrothermal Process and Limestone Additive

The usage of plastic-impregnated waste derived solid fuel in conventional combustor is hindered by many technical factors, especially its organic chlorine content. In this paper, experimental study of hydrothermal treatment on mixed plastic waste using the mixture of polypropylene, polystyrene, polyethylene and polyvinyl chloride （PVC） has been performed to observe the dechlorination effect of hydrothermal treatment on the waste. The system was generally applying saturated steam at around 2.4 MPa in a stirring reactor for about 90 minutes. After undergoing the process, the organic chlorine in treated plastic waste was reduced to 1,700 ppm level while the inorganic chlorine content was increased, suggesting an organic chlorine conversion phenomenon to inorganic chlorine, accompanied with low pH due to dehydrochlorination process. Additional limestone （Ca（OH）2） in subsequent experiment showed that the similar phenomenon was occurred but with higher pH and lower chlorine content in the condensed water, suggesting the production of inorganic salt rather than hydrochloric acid. Laboratory scale experiment was also performed to confirm the dechlorination phenomena especially for PVC, and the result showed that the main parameter which affected the dechlorination phenomena was the amount of water in hydrothermal process rather than limestone addition. It is suggested that a combination ofhydrothermal process and alkali addition would produce a low-chlorine solid product from plastic waste, promoting its usage as alternative solid fuel.

Effects of synthesis factors on the morphology, crystallinity and crystal size of hydroxyapatite precipitation

The growing necessity of biomaterials has increased the interest in hydroxyapatite. Small differences in particle sizes, stoichiometry, morphology, crystallinity could lead to different clinical behaviors. In the present work, stoichiometry and nanocrystal hydroxyapatite were prepared by wet chemical precipitation method. The effects of concentration of reagents, reaction temperatures and reaction time were studied. Transmission Electron Microscopy, Electron Diffraction, X - ray Diffraction, Fourier Transform Infrared Spectroscopy, arid Inductively Coupled Plasma Spectroscopy were used to characterize the precipitated hydroxyapatite powders. X - ray Diffraction and TEM micrographs results showed that crystallinity, morphology and particle sizes were largely dependent on reaction temperature. Chemical analysis showed that the purity of the precipitated hydroxyapatite depends on reaction time and reaction temperature. Degree of supersaturation and stirring could affect the crystallization process. Particles showed acicular morphology, and had a size of 20 - 30 nm in length at 20 ℃ and 37 ℃ and 150 - 160 nm in length at 75 ℃. Particles were monocrystalline at 20 ℃ and 37 ℃ , and were polycrystalline at 55 ℃ and 75 ℃. The results showed that hydroxyapatite powders with different particle size and morphology could be obtained with carefully controlled reaction conditions.

Transitional geology and its effects on development and longwall mining in Pittsburgh Seam

This paper presents the geologic and ground control challenges that were encountered by Consol Energy＇s coal mining operations in southwestem Pennsylvania, USA. Geologic encounters, such as sandstone- to-limestone geology transition, massive sandstone channels, shale channels, pyritic rich green claystone, laminated roof, and soft floor, have significantly impacted the development and longwall mining in Consol＇s Pittsburgh Seam coal mines. Experience from different mines shows that, in the sandstone-to-limestone geology transition zone, 1.83 m high-tension, fully-grouted primary bolts employed along with 4.88 m cen- ter cable bolts at every other strap greatly improved beam building and ensured proper anchorage into the competent roof. Hydraulic fracturing of the massive sandstone was often necessary to enhance caving of the massive sandstone behind the shields to relieve pressure at the face. The presence of soft floor coupled with presence of thick floor coal and deep cover, induced excessive headgate convergence during retreat of the first right hand longwall panel. In all, it is important to explore the roof and in-seam geology in detail to delineate normal and anomalous geologic conditions prior to and during development. With diligent geologic reconnaissance, geotechnical monitoring, and assessment, site-specific geotechnical solutions have been provided to mine operations to improve safety and productivity.