The hadal zone(ocean depths of 6 – 11 km) is one of the least-understood habitats on Earth because of its extreme conditions such as high pressure, darkness, and low temperature. With the development of deep-sea vehi...The hadal zone(ocean depths of 6 – 11 km) is one of the least-understood habitats on Earth because of its extreme conditions such as high pressure, darkness, and low temperature. With the development of deep-sea vehicles such as China's 7000 m manned submersible Jiaolong, abyssal science has received greater attention. For decades, gravity-piston corers have been widely used to collect loose subsea-sediment long-core samples. However, the weight and length of the gravity sampler cables and the operating environment limit sampling capacity at full ocean depths. Therefore, a new self-floating sediment sampler with a spring-loaded auto-trigger release and that incorporates characteristics from traditional gravity-driven samplers is designed. This study analyzes the process by which a gravity-piston corer penetrates the sediment and the factors that affect it. A formula for obtaining the penetration depth is deduced. A method of optimizing the sampling depth is then developed based on structure design and parametric factor modeling. The parameters considered in the modeling include the sampling depth, balance weight, ultimate stress friction coefficient, dimensions of the sampler, and material properties. Thus, a new deep-sea floating parametric sampler designed based on virtual prototyping is proposed. Accurate values for all the design factors are derived from calculations based on the conservation of energy with penetration depth, analyses of the factors affecting the penetration depth, and analyses of the pressure bar stability. Finally, experimental data are used to verify the penetration-depth function and to provide theoretical guidance for the design of sediment samplers.展开更多
A fast MUltiple SIgnal Classification (MUSIC) spectrum peak search algorithm is devised, which regards the power of the MUSIC spectrum function as target distribution up to a constant of proportionality, and uses Metr...A fast MUltiple SIgnal Classification (MUSIC) spectrum peak search algorithm is devised, which regards the power of the MUSIC spectrum function as target distribution up to a constant of proportionality, and uses Metropolis-Hastings (MH) sampler, one of the most popular Markov Chain Monte Carlo (MCMC) techniques, to sample from it. The proposed method reduces greatly the tremendous computation and storage costs in conventional MUSIC techniques i.e., about two and four orders of magnitude in computation and storage costs under the conditions of the experiment in the paper respectively.展开更多
The issues of how to quickly collect seawater samples and of how to make sure that those samples truly reflect the in-situ information on gas composition and concentration have therefore become a hot but difficult top...The issues of how to quickly collect seawater samples and of how to make sure that those samples truly reflect the in-situ information on gas composition and concentration have therefore become a hot but difficult topic in the field of ocean technology.Most conventional seawater samplers only focus on collecting seawater itself,but take little consideration on gas preservation.A set of new oceanographic tools are presented for ocean resource exploration such as hydrothermal sulfide and gas hydrate,and for investigations on the processes and mechanisms of marine physical,chemical and biological evolutions.A gas-tight deep-sea water sampling system(GTWSS) is designed for the collection of deep-sea geochemical samples.This set of tools mainly consists of a conductivity temperature depth profiler(CTD),release devices and gas-tight deep-sea water samplers(GTWS).The GTWS is able to hold the gases in deep-sea water samples tightly,providing in-situ information on gas contents in the seawater samples and can be deployed on a routine wire-deployed CTD sampler for multi-layer discrete sampling of gas-tight seawater.Sea trials are performed successfully in 2008 and 2009,on a research vessel named HaiYang Si Hao in South China Sea,with the deepest trial depth 3 930 m.GTWSS is capable of quickly sampling 12 discrete gas-tight seawater samples(8.3 L per sample) during its single deployment.The head space method is employed to separate the gases from the seawater samples immediately after recovery of the seawater samples on the vessel.Field geochemical analysis is carried out by gaseous hydrocarbon sensors and an infrared gas analyzer.Results show that the concentrations of CH4 and CO2 in the seawater sampled by GTWSS are higher than those sampled by general non-gas-tight water samplers,thus confirming the gas tightness of GTWSS.Seawater samples can be collected quickly by using GTWSS,and GTWSS can keep the samples' integrity quite well.展开更多
Aiming at the requirement of the full-ocean-depth(operating water depth 11000 m)manned submersible to carry out the gas-tight sampling operation of the abyss seabed sediment,a kind of full-ocean-depth carrier submersi...Aiming at the requirement of the full-ocean-depth(operating water depth 11000 m)manned submersible to carry out the gas-tight sampling operation of the abyss seabed sediment,a kind of full-ocean-depth carrier submersible mechanical hand-held,full-ocean-depth gas-tight sediment sampler(GTSS)with the function of pressure-retaining and coring is designed.Firstly,the volume change model of pressure compensator is established,and it is pointed out that the volume of pressure compensator is about 16.14%equal to the volume of gas-tight sediment sampler(GTSS).Secondly,the pressure compensator is analyzed and calculated,and the relationship between the precharge pressure of the pressure compensator,the nominal volume of the pressure compensator and the pressure holding effect of the gas-tight sediment sampler(GTSS)is studied.The results show that with the increase of gas precharge pressure in the pressure compensator,the final pressure of the sampler also increases.Under the same precharge pressure condition,the larger the nominal volume of the pressure compensator,the greater the final pressure of the sampler.Finally,the air tightness test method is designed by using the developed gas tightness sampler of the full-ocean-depth product,and the change of the final pressure in the gas tight sampler under different precharge pressure is observed.The test results are consistent with the simulation results,indicating the correctness of the pressure compensation system(PCS)model.展开更多
A new seabed sediment fidelity sampler was developed and its thermal insulation performance was studied and analyzed. The temperature distribution simulation indicated that the sample quality could be insured by using...A new seabed sediment fidelity sampler was developed and its thermal insulation performance was studied and analyzed. The temperature distribution simulation indicated that the sample quality could be insured by using this new sampler. Based on ANSYS10, the temperature finite element model of the sample cylinder was established. According to the law of conservation of energy, the unsteady heat transmit equation of the sampler under solid-liquid coupling condition was derived, then the mathematical model calculation was carried out by using a mixed finite-element finite-difference method, and two thermal insulation methods were used. The simulation was carried out by using the thickness of the thermal insulation layer and heat conductivity as the variable parameters and the temperature distribution of the sampler and related influencing factors were obtained. Optimization analysis was conducted using the simulation data and related parameters and the magnitude ranges of the parameters were obtained that could meet the design temperature requirements. The experimental data and simulation results indicated that the results were in good agreement with the realities, and this sampler might be of value for seabed sediment sampler design and manufacture.展开更多
This paper describes the design, construction and preliminary test results for a gas-tight serial sampler intended to be deployed at seafloor for long-term operation to take time-series fluid samples from deep-sea env...This paper describes the design, construction and preliminary test results for a gas-tight serial sampler intended to be deployed at seafloor for long-term operation to take time-series fluid samples from deep-sea environments such as cold seeps, water column and hydrothermal vents. The serial sampler is a modular system that is based on independent and identical sampling modules, which are designed to collect six 160 ml gas-tight fluid samples maintained at high pressure to a depth of 4000 meters. With two working modes, the sampler can be deployed either with seafloor cabled observatory for remote control or as a stand-alone device for autonomous operation. A prototype of the instrument has been constructed and tested on the MARS cabled observatory for two months. The laboratory and field tests proved the success of the design and construction of the serial sampler, and indicated the potential for future ocean sciences.展开更多
In this paper,the structure of 'double juts' soil sampler and a series of new soil samplers are introduced.The internal diameter of auger tip the sampler is less than that of sampling tube, but the external di...In this paper,the structure of 'double juts' soil sampler and a series of new soil samplers are introduced.The internal diameter of auger tip the sampler is less than that of sampling tube, but the external diameterof auger tip is larger than that of sampling tube. Therefore, adhesion and cutting resistance can be reducedby limiting connection areas between sampler and the soil. Such a new structure makes it possible to bewidely used for the production of a series of special soil samplers.展开更多
A diagnostic procedure based on maximum likelihood estimation, to study the convergence of the Markov chain produced by Gibbs sampler, is presented. The unbiasedness, consistent and asymptotic normality are considered...A diagnostic procedure based on maximum likelihood estimation, to study the convergence of the Markov chain produced by Gibbs sampler, is presented. The unbiasedness, consistent and asymptotic normality are considered for the estimation of the parameters produced by the procedure. An example is provided to illustrate the procedure, and the numerical result is consistent with the theoretical one.展开更多
To understand food webs functioning in intertidal soft-sediments, it is critical to assess the macrobenthic prey fraction accessible to waders. Here we describe a simple core sampler device allowing to directly relati...To understand food webs functioning in intertidal soft-sediments, it is critical to assess the macrobenthic prey fraction accessible to waders. Here we describe a simple core sampler device allowing to directly relating the vertical distribution of macrozoobenthos to waders bill length. Bill length measurements were used as a proxy of probing depth to estimate the amount of food supply accessible. Several metal plates can be inserted in the core sampler at different heights according to the bill length data of the studied species. These data are provided in a literature survey. For each species, the bill length variability is then explicitly taken into account in the estimation of food accessibility. The core is transparent to check for the quality of the sample. It could also be used to estimate a Benthic Habitat Quality index (BHQ) based on characteristics of the vertical structure of the sediment. This multilevel core is easy to build and to adapt to any studied wader species of the intertidal zone, floodplains or other wetlands. The samples are obtained with the same effort as with usual circular cores leading to the possibility to survey large area. With one core sample, the ecological information that can be achieved at once is threefold: 1) benthic community structure (partitioned in several depths), 2) estimate of the accessible food fraction to waders (range of values) and 3) habitat quality index assessment.展开更多
Passive sampling for the monitoring of organic pollutants (PAHs, PCBs, PBDEs) in ambient air has received increased attention in the last two decades. However, the accuracy of the concentration of organics obtained wi...Passive sampling for the monitoring of organic pollutants (PAHs, PCBs, PBDEs) in ambient air has received increased attention in the last two decades. However, the accuracy of the concentration of organics obtained with passive samplers under varying environmental conditions is a subject of controversy. In this study, effect of ambient temperature on passive samplers was evaluated by using three different sampler configurations. Additionally, passive samplers with polyurethane disks (PUF) were applied throughout the Island for the determination of the airborne concentration of polycyclic aromatic hydrocarbons (PAHs). The passive samplers were deployed in seven municipalities for three-month periods in two different sampling campaigns, representing hurricane and non-hurricane seasons. Here we present preliminary results obtained from those sampling campaigns. The total concentrations of 15 PAHs varied from 3.1 to 19.6 and from 5.5 to 38.5 ng/m3 for hurricane and non-hurricane seasons, respectively. Hurricane and non-hurricane season concentrations of PAH were significantly different for the samples taken in the northern municipalities of the Island. However, there was no significant difference in PAH concentrations between the hurricane and non-hurricane seasons for the southern sites. Increased rainfall and high-relative humidity during the hurricane season had an influence on the concentrations of PAHs derived by the passive PUF sampler.展开更多
For the gradual maturity of Bayesian survival analysis theory,as well as the defects of the traditional methods for storage reliability evaluation,the Bayesian survival analysis method is proposed to build regression ...For the gradual maturity of Bayesian survival analysis theory,as well as the defects of the traditional methods for storage reliability evaluation,the Bayesian survival analysis method is proposed to build regression models for reliability in the random truncated test.These models can reflect the influences of different environments on the ammunition storage lifetime.As an example,the common exponential distribution is used here,and Markov chain Monte Carlo(MCMC)method based on Gibbs sampling dynamically simulates the Markov chain of the parameters' posterior distribution.Also,the parameters' Bayesian estimations are calculated in the random truncated condition.The simulation results show that the proposed method is effective and directly perceived.展开更多
Measurements of gaseous SO2, NO, NO2, H2S, O3, NH3 and VOCs, in Kuwait city using IVL passive sampler technology, were obtained on monthly basis during the period from March 2011 to February 2012 at 10 locations. The ...Measurements of gaseous SO2, NO, NO2, H2S, O3, NH3 and VOCs, in Kuwait city using IVL passive sampler technology, were obtained on monthly basis during the period from March 2011 to February 2012 at 10 locations. The results of this study reveal that those compounds had low concentrations compared to Kuwait Environment Public Authority standards for residential areas. It is found that nitrogen oxides, benzene and xylene were mostly emitted from motor vehicles;in contrast, industrial sources including oil industries were a major contributor to sulfur dioxide and toluene pollution. Higher concentrations of NOx and SO2?were recorded during winter season where the inversion layer is quite pronounced thus trapping more pollutants in ambient air, while higher O3 values were recorded in summer period;the hot season in Kuwait. The spatial distributions of the measured gaseous air pollutants were extremely consistent with the influence of the prevailing wind direction NW. In general and except for PM10, the yearly average air quality indices (AQI) of SO2, NO2, CO and O3?concentrations are coming under the category of “good” and “moderate”.展开更多
Efforts have increased to measure nitrate losses from farmland under different management practices due to environmental and public concerns over levels of nitrate-nitrogen (NO<sub>3</sub>-N) in surface an...Efforts have increased to measure nitrate losses from farmland under different management practices due to environmental and public concerns over levels of nitrate-nitrogen (NO<sub>3</sub>-N) in surface and ground waters. This study evaluated the effect of conventional tillage (CT) and strip tillage (ST) practices and three N application rates on NO3-N concentrations in soil water at a 76 cm depth under irrigated sugarbeet (Beta vulgaris L.) in a clay loam soil. Nitrogen rates were applied as dry urea at 120, 150, 180 kg N ha-1</sup> in 2006;130, 160, 190 kg N ha-1 in 2007;and 110, 140, 170 kg N ha<sup>-1</sup> in 2008. Soil water volumes were measured weekly during each growing season using three ceramic suction cup samplers per plot placed at a 76 cm depth below the soil surface under each tillage. Results indicated that NO<sub>3</sub>-N concentrations at the 76 cm depth in the soil profile were not significantly affected by either tillage practice or by N application rate due to soil variability across the field and due to suction cup samplers’ biased estimate of soil water. The three N rates under CT and ST practices maintained NO<sub>3</sub>-N concentrations below the root zone to levels exceeding the 10 mg L<sup>-1</sup> safe drinking water maximum level in all three years. There were large variations in NO<sub>3</sub>-N concentrations among replicates within each tillage and N rate that were likely caused by variability in soil physical, hydraulic and chemical properties that impacted water movement through the soil profile, N dynamics and leaching below the root zone of sugarbeet. In conclusion, suction cup samplers are point water measurement devices that reveal considerable variability among replicates within each treatment due to the heterogeneity of field soils. Further, these samplers are not recommended in heterogeneous soils with preferential flow characteristics.展开更多
基金jointly supported by the Stable Supporting Fund of Science and Technology on Underwater Vehicle Technology (No. JCKYS2019604SXJQR-06)the National Natural Science Foundation of China-Marine Science Research Center of Shandong Provincial Government Joint Funding Project (No. U1606401)+3 种基金the National Natural Science Foundation of China (No. 61603108)the Taishan Scholar Project Funding (No. tspd20161007)the National Key Research and Development Plan (Nos. 2016YFC03007042017YFC030660)。
文摘The hadal zone(ocean depths of 6 – 11 km) is one of the least-understood habitats on Earth because of its extreme conditions such as high pressure, darkness, and low temperature. With the development of deep-sea vehicles such as China's 7000 m manned submersible Jiaolong, abyssal science has received greater attention. For decades, gravity-piston corers have been widely used to collect loose subsea-sediment long-core samples. However, the weight and length of the gravity sampler cables and the operating environment limit sampling capacity at full ocean depths. Therefore, a new self-floating sediment sampler with a spring-loaded auto-trigger release and that incorporates characteristics from traditional gravity-driven samplers is designed. This study analyzes the process by which a gravity-piston corer penetrates the sediment and the factors that affect it. A formula for obtaining the penetration depth is deduced. A method of optimizing the sampling depth is then developed based on structure design and parametric factor modeling. The parameters considered in the modeling include the sampling depth, balance weight, ultimate stress friction coefficient, dimensions of the sampler, and material properties. Thus, a new deep-sea floating parametric sampler designed based on virtual prototyping is proposed. Accurate values for all the design factors are derived from calculations based on the conservation of energy with penetration depth, analyses of the factors affecting the penetration depth, and analyses of the pressure bar stability. Finally, experimental data are used to verify the penetration-depth function and to provide theoretical guidance for the design of sediment samplers.
基金Supported by the National Natural Science Foundation of China (No.60172028).
文摘A fast MUltiple SIgnal Classification (MUSIC) spectrum peak search algorithm is devised, which regards the power of the MUSIC spectrum function as target distribution up to a constant of proportionality, and uses Metropolis-Hastings (MH) sampler, one of the most popular Markov Chain Monte Carlo (MCMC) techniques, to sample from it. The proposed method reduces greatly the tremendous computation and storage costs in conventional MUSIC techniques i.e., about two and four orders of magnitude in computation and storage costs under the conditions of the experiment in the paper respectively.
基金supported by National Hi-tech Research and Development Program of China(863 Program,Grant Nos. 2006AA09A204-1,2006AA09Z222-1,2009AA09A20401-1)
文摘The issues of how to quickly collect seawater samples and of how to make sure that those samples truly reflect the in-situ information on gas composition and concentration have therefore become a hot but difficult topic in the field of ocean technology.Most conventional seawater samplers only focus on collecting seawater itself,but take little consideration on gas preservation.A set of new oceanographic tools are presented for ocean resource exploration such as hydrothermal sulfide and gas hydrate,and for investigations on the processes and mechanisms of marine physical,chemical and biological evolutions.A gas-tight deep-sea water sampling system(GTWSS) is designed for the collection of deep-sea geochemical samples.This set of tools mainly consists of a conductivity temperature depth profiler(CTD),release devices and gas-tight deep-sea water samplers(GTWS).The GTWS is able to hold the gases in deep-sea water samples tightly,providing in-situ information on gas contents in the seawater samples and can be deployed on a routine wire-deployed CTD sampler for multi-layer discrete sampling of gas-tight seawater.Sea trials are performed successfully in 2008 and 2009,on a research vessel named HaiYang Si Hao in South China Sea,with the deepest trial depth 3 930 m.GTWSS is capable of quickly sampling 12 discrete gas-tight seawater samples(8.3 L per sample) during its single deployment.The head space method is employed to separate the gases from the seawater samples immediately after recovery of the seawater samples on the vessel.Field geochemical analysis is carried out by gaseous hydrocarbon sensors and an infrared gas analyzer.Results show that the concentrations of CH4 and CO2 in the seawater sampled by GTWSS are higher than those sampled by general non-gas-tight water samplers,thus confirming the gas tightness of GTWSS.Seawater samples can be collected quickly by using GTWSS,and GTWSS can keep the samples' integrity quite well.
基金Supported by National Key Research and Development Program of China(Grant No.2016YFC0300502)National Natural Science Foundation of China(Grant No.517779092)+1 种基金Special Project for the Construction of Innovative Provinces in Hunan(Grant No.2019GK1012)Postgraduate Scientific Research Innovation Project of Hunan Province(Grant No.CX20210985).
文摘Aiming at the requirement of the full-ocean-depth(operating water depth 11000 m)manned submersible to carry out the gas-tight sampling operation of the abyss seabed sediment,a kind of full-ocean-depth carrier submersible mechanical hand-held,full-ocean-depth gas-tight sediment sampler(GTSS)with the function of pressure-retaining and coring is designed.Firstly,the volume change model of pressure compensator is established,and it is pointed out that the volume of pressure compensator is about 16.14%equal to the volume of gas-tight sediment sampler(GTSS).Secondly,the pressure compensator is analyzed and calculated,and the relationship between the precharge pressure of the pressure compensator,the nominal volume of the pressure compensator and the pressure holding effect of the gas-tight sediment sampler(GTSS)is studied.The results show that with the increase of gas precharge pressure in the pressure compensator,the final pressure of the sampler also increases.Under the same precharge pressure condition,the larger the nominal volume of the pressure compensator,the greater the final pressure of the sampler.Finally,the air tightness test method is designed by using the developed gas tightness sampler of the full-ocean-depth product,and the change of the final pressure in the gas tight sampler under different precharge pressure is observed.The test results are consistent with the simulation results,indicating the correctness of the pressure compensation system(PCS)model.
基金supported by The Key Technologies Research and Development Program of Shandong Province (Grant No.2006GG2206013)Foundation Sciences Funds of Qingdao (2007-2-3-15-jch)State Key Laboratory of Ocean Engineering at Shanghai Jiao Tong University (Grant No. XXXX0701)
文摘A new seabed sediment fidelity sampler was developed and its thermal insulation performance was studied and analyzed. The temperature distribution simulation indicated that the sample quality could be insured by using this new sampler. Based on ANSYS10, the temperature finite element model of the sample cylinder was established. According to the law of conservation of energy, the unsteady heat transmit equation of the sampler under solid-liquid coupling condition was derived, then the mathematical model calculation was carried out by using a mixed finite-element finite-difference method, and two thermal insulation methods were used. The simulation was carried out by using the thickness of the thermal insulation layer and heat conductivity as the variable parameters and the temperature distribution of the sampler and related influencing factors were obtained. Optimization analysis was conducted using the simulation data and related parameters and the magnitude ranges of the parameters were obtained that could meet the design temperature requirements. The experimental data and simulation results indicated that the results were in good agreement with the realities, and this sampler might be of value for seabed sediment sampler design and manufacture.
基金financially supported by the National High Technology Research and Development Program of China(863 Program,Grant No.2010AA09Z202)the National Natural Science Foundation of China(Grant No.41106081)+2 种基金the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(Grant No.51221004)the United States National Science Foundation(Grant No.0927615)the Knowledge Innovation Project from Sanya Institute of Deep-sea Science and Engineering(Grant No.SIDSSE-201204)
文摘This paper describes the design, construction and preliminary test results for a gas-tight serial sampler intended to be deployed at seafloor for long-term operation to take time-series fluid samples from deep-sea environments such as cold seeps, water column and hydrothermal vents. The serial sampler is a modular system that is based on independent and identical sampling modules, which are designed to collect six 160 ml gas-tight fluid samples maintained at high pressure to a depth of 4000 meters. With two working modes, the sampler can be deployed either with seafloor cabled observatory for remote control or as a stand-alone device for autonomous operation. A prototype of the instrument has been constructed and tested on the MARS cabled observatory for two months. The laboratory and field tests proved the success of the design and construction of the serial sampler, and indicated the potential for future ocean sciences.
文摘In this paper,the structure of 'double juts' soil sampler and a series of new soil samplers are introduced.The internal diameter of auger tip the sampler is less than that of sampling tube, but the external diameterof auger tip is larger than that of sampling tube. Therefore, adhesion and cutting resistance can be reducedby limiting connection areas between sampler and the soil. Such a new structure makes it possible to bewidely used for the production of a series of special soil samplers.
文摘A diagnostic procedure based on maximum likelihood estimation, to study the convergence of the Markov chain produced by Gibbs sampler, is presented. The unbiasedness, consistent and asymptotic normality are considered for the estimation of the parameters produced by the procedure. An example is provided to illustrate the procedure, and the numerical result is consistent with the theoretical one.
文摘To understand food webs functioning in intertidal soft-sediments, it is critical to assess the macrobenthic prey fraction accessible to waders. Here we describe a simple core sampler device allowing to directly relating the vertical distribution of macrozoobenthos to waders bill length. Bill length measurements were used as a proxy of probing depth to estimate the amount of food supply accessible. Several metal plates can be inserted in the core sampler at different heights according to the bill length data of the studied species. These data are provided in a literature survey. For each species, the bill length variability is then explicitly taken into account in the estimation of food accessibility. The core is transparent to check for the quality of the sample. It could also be used to estimate a Benthic Habitat Quality index (BHQ) based on characteristics of the vertical structure of the sediment. This multilevel core is easy to build and to adapt to any studied wader species of the intertidal zone, floodplains or other wetlands. The samples are obtained with the same effort as with usual circular cores leading to the possibility to survey large area. With one core sample, the ecological information that can be achieved at once is threefold: 1) benthic community structure (partitioned in several depths), 2) estimate of the accessible food fraction to waders (range of values) and 3) habitat quality index assessment.
文摘Passive sampling for the monitoring of organic pollutants (PAHs, PCBs, PBDEs) in ambient air has received increased attention in the last two decades. However, the accuracy of the concentration of organics obtained with passive samplers under varying environmental conditions is a subject of controversy. In this study, effect of ambient temperature on passive samplers was evaluated by using three different sampler configurations. Additionally, passive samplers with polyurethane disks (PUF) were applied throughout the Island for the determination of the airborne concentration of polycyclic aromatic hydrocarbons (PAHs). The passive samplers were deployed in seven municipalities for three-month periods in two different sampling campaigns, representing hurricane and non-hurricane seasons. Here we present preliminary results obtained from those sampling campaigns. The total concentrations of 15 PAHs varied from 3.1 to 19.6 and from 5.5 to 38.5 ng/m3 for hurricane and non-hurricane seasons, respectively. Hurricane and non-hurricane season concentrations of PAH were significantly different for the samples taken in the northern municipalities of the Island. However, there was no significant difference in PAH concentrations between the hurricane and non-hurricane seasons for the southern sites. Increased rainfall and high-relative humidity during the hurricane season had an influence on the concentrations of PAHs derived by the passive PUF sampler.
基金Sponsored by National Nature Science Foundation of China(70771038).
文摘For the gradual maturity of Bayesian survival analysis theory,as well as the defects of the traditional methods for storage reliability evaluation,the Bayesian survival analysis method is proposed to build regression models for reliability in the random truncated test.These models can reflect the influences of different environments on the ammunition storage lifetime.As an example,the common exponential distribution is used here,and Markov chain Monte Carlo(MCMC)method based on Gibbs sampling dynamically simulates the Markov chain of the parameters' posterior distribution.Also,the parameters' Bayesian estimations are calculated in the random truncated condition.The simulation results show that the proposed method is effective and directly perceived.
文摘Measurements of gaseous SO2, NO, NO2, H2S, O3, NH3 and VOCs, in Kuwait city using IVL passive sampler technology, were obtained on monthly basis during the period from March 2011 to February 2012 at 10 locations. The results of this study reveal that those compounds had low concentrations compared to Kuwait Environment Public Authority standards for residential areas. It is found that nitrogen oxides, benzene and xylene were mostly emitted from motor vehicles;in contrast, industrial sources including oil industries were a major contributor to sulfur dioxide and toluene pollution. Higher concentrations of NOx and SO2?were recorded during winter season where the inversion layer is quite pronounced thus trapping more pollutants in ambient air, while higher O3 values were recorded in summer period;the hot season in Kuwait. The spatial distributions of the measured gaseous air pollutants were extremely consistent with the influence of the prevailing wind direction NW. In general and except for PM10, the yearly average air quality indices (AQI) of SO2, NO2, CO and O3?concentrations are coming under the category of “good” and “moderate”.
文摘Efforts have increased to measure nitrate losses from farmland under different management practices due to environmental and public concerns over levels of nitrate-nitrogen (NO<sub>3</sub>-N) in surface and ground waters. This study evaluated the effect of conventional tillage (CT) and strip tillage (ST) practices and three N application rates on NO3-N concentrations in soil water at a 76 cm depth under irrigated sugarbeet (Beta vulgaris L.) in a clay loam soil. Nitrogen rates were applied as dry urea at 120, 150, 180 kg N ha-1</sup> in 2006;130, 160, 190 kg N ha-1 in 2007;and 110, 140, 170 kg N ha<sup>-1</sup> in 2008. Soil water volumes were measured weekly during each growing season using three ceramic suction cup samplers per plot placed at a 76 cm depth below the soil surface under each tillage. Results indicated that NO<sub>3</sub>-N concentrations at the 76 cm depth in the soil profile were not significantly affected by either tillage practice or by N application rate due to soil variability across the field and due to suction cup samplers’ biased estimate of soil water. The three N rates under CT and ST practices maintained NO<sub>3</sub>-N concentrations below the root zone to levels exceeding the 10 mg L<sup>-1</sup> safe drinking water maximum level in all three years. There were large variations in NO<sub>3</sub>-N concentrations among replicates within each tillage and N rate that were likely caused by variability in soil physical, hydraulic and chemical properties that impacted water movement through the soil profile, N dynamics and leaching below the root zone of sugarbeet. In conclusion, suction cup samplers are point water measurement devices that reveal considerable variability among replicates within each treatment due to the heterogeneity of field soils. Further, these samplers are not recommended in heterogeneous soils with preferential flow characteristics.