“源汇理论”在土壤重金属污染监测中的应用现状、问题与展望

随着工业化和城市化的发展,土壤重金属污染问题日益突出,通过对土壤重金属污染状况监测以及污染来源解析,制定适宜的污染防治措施将有助于食品安全和人类健康。通过引入“源汇理论”,在系统梳理国内外相关研究成果的基础上,阐明“源汇理论”的定义、原理、特点及其在土壤重金属污染中的应用意义,并从污染区域监测、污染来源解析、污染源汇关系3个方面总结研究进展。结果表明,“源汇理论”在应用于土壤重金属污染的监测和分析过程中存在信息提取难、精度不高、难以准确验证、未能实现动态分析、未能形成体系等问题。随着“源汇理论”的不断丰富,在其指导下,未来土壤重金属污染研究应围绕“从传统机器学习走向深度学习,点-线-面结合监测验证框架,天-空-地一体化监测网络和验证体系,从‘3S’上升到‘5S’技术集成,监测、评估、溯源、预警与防治相结合”等方向发展,以期为构建大面积土壤重金属污染智慧动态监测与风险预警决策系统奠定基础。

电动汽车替代燃油车的气候和健康影响及社会成本--基于单车视角的成本效益分析

构建基于能源周期和全生命周期的分析框架,借助基于概率分布的成本效益分析方法,通过评估单辆纯电动汽车替代汽油车的气候和健康影响及相关社会成本,探讨现阶段电动汽车替代传统燃油车能否实现气候、健康和社会福利的改进。研究结果表明,在现有技术条件和电厂超低排放改造背景下,尽管电动汽车替代传统燃油车在能源周期能够实现碳减排(约324元/(辆年))、健康损害降低(约343元/(辆年))以及可观的能源节约(约4315元/(辆年)),但由于两种车辆之间巨大的制造成本差异(约1.6万元/(辆年)),现阶段电动汽车对传统燃油车的全面替代并不能实现社会总体福利的改进。因此,中国电动汽车推广政策短期内不应以全面替代为目标,而应识别具有较高气候和健康效益以及具有较大能源节约潜力的区域优先推广。

Numerical investigation of the control factors driving Zhe-Min Coastal Current

During the northeast monsoon season,Zhe-Min Coastal Current(ZMCC)travels along the Chinese mainland coast and carries fresh,cold,and eutrophic water.ZMCC is significantly important for the hydrodynamic processes and marine ecosystems along its path.Thus,this bottom-trapped plume deserves to be further discussed in terms of the major driving factor,for which different opinions exist.For this purpose,in this study,a high resolution Semi-implicit Cross-scale Hydroscience Integrated System Model(SCHISM)is established and validated.High correlation coefficients exist between along-shelf wind speeds and seasonal variations of both ZMCC volume transport and the freshwater signal.These coefficients imply that the wind is important in regulating ZMCC.However,for similar annual mean ZMCC volume transports,the extreme south boundaries of Zhe-Min Coastal Water(ZMCW)are different among different years.This difference is attracting attention and is explored in this study.According to the low wind/discharge experiment,it was found that although the volume transport of ZMCC is more sensitive to the variation of local wind speeds,the carried freshwater is limited by the Changjiang River discharge,which ultimately determines the south boundary of ZMCW.The momentum analysis at transects I and II shows that,for driving ZMCC,the along-shore wind forcing is as important as the buoyancy forcing.Note that this conclusion is supported by a zero-discharge experiment.It was also found that the buoyancy forcing varies with respect to time and space,which is due to variations of the discharge of Changjiang River.In addition,a particle tracking experiment shows that the substance carried by the Changjiang River diluted water would distribute along the Zhe-Min coastal region during the northeast monsoon season and it may escape due to the wind relaxation.

The Effect of the Width of the Incident Pulse to the Dielectric Transition Layer in the Scattering of an Electromagnetic Pulse–a Qubit Lattice Algorithm Simulation

The effect of the thickness of the dielectric boundary layer that connects amaterial of refractive index n1 to another of index n2 is considered for the propagation of an electromagnetic pulse.A qubit lattice algorithm(QLA),which consists of a specially chosen non-commuting sequence of collision and streaming operators acting on a basis set of qubits,is theoretically determined that recovers theMaxwell equations to second-order in a small parameterǫ.For very thin but continuous boundary layer the scattering properties of the pulse mimics that found from the Fresnel discontinuous jump conditions for a plane wave-except that the transmission to incident amplitudes are augmented by a factor of√n2/n1.As the boundary layer becomes thicker one finds deviations away from the discontinuous Fresnel conditions and eventually one approaches the expectedWKB limit.However there is found a small but unusual dip in part of the transmitted pulse that persists in time.Computationally,the QLA simulations still recover the solutions to Maxwell equations even when this parameterǫ→1.On examining the pulse propagation in medium n1,ǫcorresponds to the dimensionless speed of the pulse(in lattice units).

Marsh persistence under sea-level rise is controlled by multiple,geologically variable stressors

Introduction:Marshes contribute to habitat and water quality in estuaries and coastal bays.Their importance to continued ecosystem functioning has led to concerns about their persistence.Outcomes:Concurrent with sea-level rise,marshes are eroding and appear to be disappearing through ponding in their interior;in addition,in many places,they are being replaced with shoreline stabilization structures.We examined the changes in marsh extent over the past 40 years within a subestuary of Chesapeake Bay,the largest estuary in the United States,to better understand the effects of sea-level rise and human pressure on marsh coverage.Discussion:Approximately 30 years ago,an inventory of York River estuary marshes documented the historic extent of marshes.Marshes were resurveyed in 2010 to examine shifts in tidal marsh extent and distribution.Marsh change varied spatially along the estuary,with watershed changes between a 32%loss and an 11%gain in marsh area.Loss of marsh was apparent in high energy sections of the estuary while there was marsh gain in the upper/riverine section of the estuary and where forested hummocks on marsh islands have become inundated.Marshes showed little change in the small tributary creeks,except in the creeks dominated by fringing marshes and high shoreline development.Conclusions:Differential resilience to sea-level rise and spatial variations in erosion,sediment supply,and human development have resulted in spatially variable changes in specific marsh extents and are predicted to lead to a redistribution of marshes along the estuarine gradient,with consequences for their unique communities.

Low-cost wave characterization modules for oil spill response

Marine oil spills can be remediated by mechanical skimmers in calm waters,but performance degrades with increased wave height.We have developed and demonstrated a system that quantifies local wave characteristics with an uncertainty of four inches of heave.Our system is intended for the measurement of wave characteristics during oil spill recovery.It conveys this information to coordinators and responders in real time via WiFi and remote reporting through a satellite network.This information will allow for enhanced situational awareness during an oil spill response,assisting stakeholders and optimizing mechanical skimming operations.Our wave characterization module(WCM)uses accelerometer outputs from a very small inertial measurement unit(IMU)to generate wave statistics and calculate wave characteristics.It is configured such that a WCM can either be attached to a skimmer float or incorporated into a microbuoy.Wave height and period are transmitted via WiFi and/or a satellite-enabled mesh-grid network to a cloud-hosted geographic information system(GIS).Here,we discuss the bare-bones sensors-plus-algorithm approach we developed by using spring-mass systems to approximate the wave height and period regime of interest.We then describe open water tests carried out using that development system both mounted to a weir skimmer mockup and packaged in a microbuoy.Finally,we present controlled tests in the wave tank at Ohmsett,the National Oil Spill Response Test Facility in New Jersey,with the WCMs communicating the wave characteristics via WiFi to tankside laptops and via satellite to the cloud-based GIS.Snapshot determinations of wave height calculated using the scalar magnitude of the three-axis accelerometer in the IMU were within four inches of the benchmark wave measurement system at Ohmsett.

MHD Turbulence Studies using Lattice Boltzmann Algorithms

Three dimensional free-decaying MHD turbulence is simulated by lattice Boltzmann methods on a spatial grid of 80003 for low and high magnetic Prandtl number.It is verified that∇·B=0 is automatically maintained to machine accuracy throughout the simulation.Isosurfaces of vorticity and current show the persistence of many large scale structures(both magnetic and velocity)for long times—unlike the velocity isosurfaces of Navier-Stokes turbulence.