环境归趋模型参数估计方法的比较

大量的研究表明,参数估计方法的可行性和有效性,决定着环境归趋模型的成功与否。在文献检索的基础上,简单介绍了环境归趋模型参数估计方法的类型和最优化原理,分析了各种方法的优点与不足,并初步探讨了环境归趋模型参数估计方法的研究趋势。     

面向我国化学物质环境管理的计算毒理学模型评估思路及建设路径

计算毒理学模型正逐渐成为我国化学物质环境管理的重要工具之一.为了推动建立面向我国化学物质环境管理的计算毒理学模型评估方法体系,掌握模型评估核心技术,本文分析了我国发展和评估计算毒理学模型的必要性,总结了我国计算毒理学模型评估的管理需求,系统梳理了美国、欧盟、国际经济合作与发展组织(OECD)的模型评估方法.研究发现,发达国家普遍建立了一套相对完善的计算毒理学模型评估技术,构建了包含模型开发、评估、验证和应用的模型生命周期评估体系.当前,我国尚未建立计算毒理学模型评估技术方法,借鉴发达国家的经验做法,构建具有我国国情特征的计算毒理学模型评估体系,指导我国计算毒理学模型征集与评估工作,具有重要意义.     

农药混配制剂环境风险评估现状与展望

本文综述了欧洲和美国农药混配制剂的环境风险评估方法。详细介绍了欧洲食品安全局(EFSA)评估体系中的2种方法,即,基础的"整体测试法"和近年来提倡的"基于组分的方法"。"基于组分的方法"的特点是以浓度加和模型(CA模型)作为默认假设进行初级评估,以独立作用模型(IA模型)等作为高级评估手段的农药混配制剂环境风险评估方法。此外,本文还介绍了模型偏差率(MDR)、毒性相似度及毒力单元(TU)等概念以及混配制剂风险评估流程。本文的目的旨在为建立我国农药混配制剂的环境风险评估方法体系提供参考。     

多环芳烃光解活性的量子化学研究

应用量子化学从头算HF／6-311 G(d)和B3LYP／6-311 G(d)方法计算了16种PAHs的多种量子化学参数,选取六种参数为分子结构的描述符,采用最小二乘法对16种PAHs的光解半衰期进行逐步多元线性回归分析,得到两个PAHs光解半衰期的QSAR模型,模型具有较高的相关系数,可有效地用于预测PAHs的光解半衰期,结果表明,HF方法所得模型优于B3LYP方法所得的模型,所得模型与基于半经验PM3算法的QSAR模型相比较,HF从头算方法所建立的QSAR模型比半经验PM3算法的结果要好,在所考查的诸多参数中,分子最高占有轨道特征值EHOMO对PAHs光解半衰期起着决定作用,最后,运用所得模型预测了3种PAHs的光解半衰期。     

城市给水管网余氯的预测模型

选择余氯为研究对象,以南方某市给水管网水质监测的数据为基础,使用线性回归和非线性神经网络(ANN)方法建立模型,找到了一种利用在线监测数据和人工监测数据实时预测管网余氯的方法。通过建立给水管网水质模型,可以由监测系统动态回传的数据来实时的预测下一天人工点的水质。模拟的结果显示ANN模型比线性回归模型有更好的预测能力,预测的平均相对误差:ANN模型为14.9%,线性回归模型为25.8%。使用ANN模型可以实现实时预测。     

欧美农药环境降解动力学评估方法比较

农药在环境中的降解行为是评估农药环境安全性的基础,农药的降解动力学通常以一级动力学模型描述。现有的环境暴露模型也均需要输入一级动力学模型的农药在土壤中50%消失时间(DT50)。但有时一级动力学模型不适用于描述农药在环境中,特别是土壤中的降解。因此欧盟和北美自由贸易区已发布了一系列关于使用非一级动力学模型计算DT50的导则。介绍了欧美降解动力学评估方法,并用多组降解数据比较了2种评估方法的区别。     

种间关系预测(ICE)模型在水质基准研究中的应用

水质基准研究主要是基于物种的实验室测试的毒性数据开展的。对于一些毒性数据相对缺乏的化学品,水质基准研究就会受到一定的影响。本文从水质基准研究方法的角度,阐述了种间关系预测(ICE)的基本原理和基本方法,系统介绍了ICE模型的毒性预测方法在水质基准研究中的应用,并通过锌的ICE案例研究证明了模型在中国的可利用性。同时,对ICE模型的不确定性和适用性进行了分析。最后,对ICE模型存在的问题和未来的发展方向进行了探索和展望。     

厌氧条件下土壤中有机氯降解动力学模型及其参数优化——以五氯酚（PCP）为例

研究厌氧条件下土壤中有机氯降解动力学模型及其参数优化方法,对阐明有机氯降解的动力学反应机制具有十分重要的理论意义。文章以厌氧条件下土壤中五氯酚（PCP）降解为例,归纳介绍了两类用于描述土壤中PCP降解动力学过程的模型：一类模型是不考虑微生物生长的基质降解模式,以一级动力学模型最有代表性,但这类模型多数情况下没有或没有完全体现环境因素对PCP降解的抑制作用;另一类模型是考虑微生物生长的基质降解模式,以Monod动力学模型使用最普遍,但这类模型只在微生物生长的指数期适用,对延迟期、稳定期和衰亡期需经扩展才可应用。logistic动力学模型可广泛用于以上两类模型,是可以近似地描述微生物经适应过程和共代谢作用而致有机氯降解的简单模型。文章还总结了有机氯降解非线性模型参数的优化方法,并对其优缺点进行了分析和比较。针对目前土壤中有机氯降解动力学模型及其参数优化研究中存在的问题,对今后的研究方向进行了展望。     

基于净初级生产力的生态足迹模型及其与传统模型的对比分析

生态足迹模型因其可以定量度量生态可持续发展、计算简单、结论易懂、全球可比等特点,提出之后得到了大量的关注和应用,同时也面临着一些质疑和争论。文章介绍了一种基于净初级生产力的生态足迹理论和计算方法,并以该方法和传统生态足迹模型分别计算了中国1961-2007年的生态足迹,对计算结果进行了对比分析。结果表明,两种生态足迹模型的计算结果具有较高的相关性,表明基于净初级生产力的生态足迹模型结果可信。该种方法能够克服传统生态足迹模型的部分缺陷,在均衡因子选取、土地生态功能假设、CO2吸收等方面有了较大改进,能够较好地反映不同生态系统在生产力上的差异;在时间序列分析方面也更加合理。但该方法本身同时存在着计算方法不完善、对生态系统变化不敏感等问题,如何更紧密地结合生态足迹和净初级生产力是需要进一步研究的内容。     

区域能源碳足迹计算模型比较研究——以湖北省为例

能源消费排放是最主要的碳排放来源,研究能源碳足迹重要理论和现实意义。如何准确计算和表征能源碳足迹的大小成为该研究领域的重要问题。在文献回顾的基础上,文章总结了3种目前应用较广泛的计算区域能源消费碳足迹的方法和模型,它们分别是碳汇法、净初级生产力改进模型和净生态系统生产力改进模型。分别介绍了其计算公式、输入参数和计算过程。以湖北省1998-2009年能源消费碳足迹的计算为例,分别用这几种方法计算了能源消费碳足迹的总量和人均碳足迹。得到的主要结论有：研究区域能源消费碳排放量增长较快,3种方法和模型计算得到的碳足迹总量和人均量从时间序列上看,整体变化趋势一致,碳足迹亦呈现快速增长。但3种模型计算出的碳足迹大小差异较大,碳汇法模型足迹最大,净生态系统生产力改进模型次之,净初级生产力改进模型结果最小,并且碳汇法的计算结果明显大于其他两种模型。计算结果差异的原因在于,传统碳汇法模型只考虑林地的碳吸收能力,忽略了区域其他用地类型的碳吸收能力。净初级生产力改进模型考虑了各种用地类型的吸收能力,但从生态系统来说忽略了异氧呼吸的碳释放,高估了区域的碳吸收能力。几种模型都运用了固定值或者平均统计量,未能考虑地域差异,同时未考虑各统计量随时间和气候等变化而变化的可能,存在一定的不合理性,这也是今后研究值得深人研究的方向。     

Simulation modeling of material and energy flow through an ecosystem: Methods and documentation

This paper discusses the process of development of large-scale ecological simulation models as it proceeds through steps divided between two major phases — conceptualization and implementation. The activities in these phases are strongly influenced by model objectives. Activities transpiring in each step are discussed and documentation methods both for the modelling process and its product are introduced for each of the steps. Examples are given from CONIFER, a large-scale coniferous forest model developed by the author in cooperation with another investigator. The role of the model documentation, both in aiding model development and in clearly communicating and allowing criticism of the model, is emphasized. Model evaluation, checking that the model satisfies its objectives, is seen as an area of model development which indicates which parts of the model need reworking.     

An adjoint data assimilation approach for estimating parameters in a three-dimensional ecosystem model

In this paper an ecosystem model, including phytoplankton, zooplankton, nitrate, ammonium, phosphate and detritus, is described. The model is driven by physical fields derived from a three-dimensional physical transport model. Simulation includes nitrate input from a river. Simulated results are then sampled and the sampled data are used in sequential numerical experiments to assess the ability of using an adjoint data assimilation approach for estimating the poorly known parameters of the ecosystem model, such as growth and death rate, half-saturation constant of nutrients, etc. Data with different spatial and temporal resolution over 1 week are assimilated into the ecosystem model. Assimilation of data at 30 grid stations with a sampling interval of 6 h is proved to be adequate for recovering all the parameters of the ecosystem model. Both the spatial and temporal resolution of the data are mutually complementary in the assimilative model. Thus, improvement of either of them can result in improvement of model parameter recoveries. The assimilation of phytoplankton data is essential to recover the model parameters. Phytoplankton is the core of the food web and without the information on phytoplankton, the structure of the ecosystem cannot be constructed correctly. The adjoint method can work well with the noisy data. In the twin experiments with noisy data, the parameters can be recovered but the error is increased. The results of the model and parameter recovery are sensitive to the initial conditions of state variables, so the determination of the initial condition is as important as that of the model parameter. The spatial and temporal resolution and the data type of the observations in Analysis and Modelling Research of the Ecosystem in the Bohai Sea (AMREB) are suitable for the recovery of the model parameters used in this study.     

有机污染土壤通风去污技术优化设计

有机污染土壤通风去污技术（SVE）是一种经济，安全的场内治理技术，SVE优化设计包括建立污染土壤通风去污模型和抽排去污流场模型，并以此为基础算工程费用，用一虚拟工况对提出的模型及计算公式进行了验证。     

An engineering model for countercurrent flow under wind-induced waves and current

A general model for the phase-averaged velocity field in wind-induced countercurrent flow is proposed. The influence of waves on the time-averaged velocity is accounted for by introducing a skewness factor in a parabolic eddy viscosity model. The skewness factor represents the net effect of the wavy surface in the engineering model for velocity. The coherent velocity components are described separately by an orbital velocity obtained from linear wave theory and are added to the time-averaged components to give a complete model for the phase-averaged velocity field. The proposed model collapses to the standard model for deep-water conditions, but is also shown to yield the correct behavior for intermediate conditions. Moreover, the bed shear stress, derived from the proposed velocity model, is also shown to be in agreement with experiments.     

The demand for site-specific recreational activities: A characteristics approach

A model of constrained utility maximizing behavior is developed to explain how a representative individual allocates his ski days among alternative sites. The physical characteristics of the ski areas and the individual's skiing ability are explicit arguments in the utility function; the budget allocation is given along with the parametric costs to ski (including travel costs, entrance fees, equipment costs, and the opportunity cost of his time). Shares (a site's share being the proportion of ski days that the individual spends at that site) are derived and assumed multinomially distributed, a stochastic specification which maintains the inherent properties of the shares. Maximum likelihood estimation confirms the basic hypothesis that costs, ability, and characteristics all are important determinants of the sites' shares. The model explains a large proportion of the skier's allocation of ski days. A multinomial logit model of skier behavior is also developed and maximum likelihood estimates of its parameters are obtained. Examination of the summary statistics from my model and the logit model indicates that my model predicts the skier's choice of sites better than the logit model.     

A hierarchical analysis of terrestrial ecosystem model Biome-BGC: Equilibrium analysis and model calibration

The increasing complexity of ecosystem models represents a major difficulty in tuning model parameters and analyzing simulated results. To address this problem, this study develops a hierarchical scheme that simplifies the Biome-BGC model into three functionally cascaded tiers and analyzes them sequentially. The first-tier model focuses on leaf-level ecophysiological processes; it simulates evapotranspiration and photosynthesis with prescribed leaf area index (LAI). The restriction on LAI is then lifted in the following two model tiers, which analyze how carbon and nitrogen is cycled at the whole-plant level (the second tier) and in all litter/soil pools (the third tier) to dynamically support the prescribed canopy. In particular, this study analyzes the steady state of these two model tiers by a set of equilibrium equations that are derived from Biome-BGC algorithms and are based on the principle of mass balance. Instead of spinning-up the model for thousands of climate years, these equations are able to estimate carbon/nitrogen stocks and fluxes of the target (steady-state) ecosystem directly from the results obtained by the first-tier model. The model hierarchy is examined with model experiments at four AmeriFlux sites. The results indicate that the proposed scheme can effectively calibrate Biome-BGC to simulate observed fluxes of evapotranspiration and photosynthesis; and the carbon/nitrogen stocks estimated by the equilibrium analysis approach are highly consistent with the results of model simulations. Therefore, the scheme developed in this study may serve as a practical guide to calibrate/analyze Biome-BGC; it also provides an efficient way to solve the problem of model spin-up, especially for applications over large regions. The same methodology may help analyze other similar ecosystem models as well.     

A Voronoi diagram based population model for social species of wildlife

A population model is presented that accounts for spatial structure within habitat patches. It is designed for social species of wildlife that form social group home ranges that are much smaller than patch size. The model represents social group home ranges by Voronoi regions that tessellate a patch to form a Voronoi diagram. Neighbouring social groups are linked with habitat-confined shortest paths and form a dispersal network. The model simulates population dynamics and makes use of Voronoi diagrams and dispersal networks as a spatial component. It then produces density maps as outputs. These are maps that show predicted animal densities across the patches of a landscape. A construction procedure for the particular Voronoi diagram type used by the model is described. As a test case, the model is run for the squirrel glider (Petaurus norfolcensis), a small arboreal marsupial native to Australia. A time series of density maps are produced that show squirrel glider density changing across a landscape through time.     

Combined integral and particle model for describing the dispersion,dilution, terminal layer formation and influence area from a point source discharge into a water body

Contamination of coastal water is a persistent threat to ecosystems around the world. In this study, a novel model for describing the dispersion, dilution, terminal layer formation and influence area from a point source discharge into a water body is presented and compared with field measured data. The model is a Combined Integral and Particle model (CIPMO). In the initial stage, the motion, dispersion and dilution of a buoyant jet are calculated. The output from the buoyant jet model is then coupled with a Lagrangian Advection and Diffusion model describing the far-field. CIPMO ensures that both the near- and far-field processes are adequately resolved. The model either uses empirical data or collects environmental forcing data from open source hydrodynamic models with high spatial and temporal resolution. The method for coupling the near-field buoyant jet and the particle tracking model is described and the output is discussed. The model shows good results when compared with measurements from a field study.