Nitrification kinetics of biofilm as affected by water quality factors

Various types of fixed film biofilters have been used in recirculating aquaculture systems under different water quality and operating conditions. The effectiveness of the nitrification process can be evaluated by nitrification kinetics. Nitrification in the bacterial film of the biofilter involves physical, chemical and biological processes that are governed by a variety of parameters such as substrate and dissolved oxygen concentrations, organic matters, temperature, pH, alkalinity, salinity and turbulence level. The impacts of these parameters upon nitrification kinetics make predicting the performance of a biofilter for a given application an engineering challenge. Knowing the performance of a biofilter is critical for both designers and managers. This paper summarizes the current knowledge on nitrification kinetics as affected by the aforementioned factors based on literature and the results from the authors’ laboratories. These factors were ranked according to their significance of impact on biofilter nitrification performance. The information presented can be used as a reference for the design and operation of biofilters in recirculating aquaculture systems.     

The pelagic habitat analysis module for ecosystem‐based fisheries science and management

We have developed a set of tools that operate within an aquatic geographic information system to improve the accessibility, and usability of remote‐sensed satellite and computer‐modeled oceanographic data for marine science and ecosystem‐based management. The tools form the Pelagic Habitat Analysis Module (PHAM), which can be applied as a modeling platform, an investigative aid in scientific research, or utilized as a decision support system for marine ecological management. Applications include fisheries, marine biology, physical and biological oceanography, and marine spatial management. The GIS provides a home for diverse data types and automated tools for downloading remote sensed and global circulation model data. Within the GIS environment, PHAM provides a framework for seamless interactive four‐dimensional visualization, for matching between disparate data types, for flexible statistic or mechanistic model development, and for dynamic application of user developed models for habitat, density, and probability predictions. Here we describe PHAM in the context of ecosystem‐based fisheries management, and present results from case study projects which guided development. In the first, an analysis of the purse seine fishery for tropical tuna in the eastern Pacific Ocean revealed oceanographic drivers of the catch distribution and the influence of climate‐driven circulation patterns on the location of fishing grounds. To support management of the Common Thresher Shark (Alopias vulpinus) in the California Current Ecosystem, a simple empirical habitat utilization model was developed and used to dynamically predict the seasonal range expansion of common thresher shark based on oceanographic conditions.     

河湖水生态系统服务价值核算研究及应用展望

科学有效地界定河湖水生态系统服务价值评估体系与评估指标,可以促进河湖水生态的可持续发展、合理制定水资源价格、为河湖水生态系统服务价值评估提供参考,同时也为河湖水资源纳入国民经济核算体系提供借鉴,为绿色经济核算提供有力的依据。从河湖水生态系统服务功能、评估体系和评估方法等方面总结了国内外研究进展,分析了现有河湖水生态系统服务体系和评估方法的优缺点。对河湖水生态系统服务评估体系进行了优化,优化后的评估体系包括供给服务、调节服务、文化服务和支持服务4大类以及水资源供给、水质净化、科研教育和固碳能力等19项指标,优化了水资源供给、提供水产品、水质净化、防洪减灾、休闲娱乐、生物多样性保护等6个指标的评估方法。对河湖水生态系统服务价值核算在生态文明建设考核、生态产品价值实现机制、自然资源资产审计以及新时期河湖长制考核实施方面的应用进行了展望。下一步要制订GEP核算技术标准,建设市场化、多元化的生态产品交易体系,将水资源开发、利用及保护情况、水资源管理生态环境效益等指标纳入审计范围,建立以水生态系统为整体、以维护河湖生态系统健康为总目标、以定量评判和可操作性为抓手的新的河湖长制考核体系。     

Tracking change in a human‐dominated landscape: developing conservation guidelines using freshwater fish

• 1. To conserve biodiversity in a human‐dominated landscape, a science‐based inventory and monitoring plan is needed that quantifies existing resources, isolates drivers that maintain natural communities, determines harmful stressors, and links ecological drivers and human stressors. A tactical approach is proposed for conservation planning using freshwater fish at the Cape Cod National Seashore.
• 2. Freshwater fish are well studied and occur across environmental gradients. The lentic systems at the national park are relatively pristine yet are enveloped by a region of high population density. Using fish community data, three steps were taken for tracking anthropogenic impacts in a human dominated landscape. First, fish and potential drivers were sampled intensively along a gradient to determine which fish metrics reflect natural communities and which abiotic and biotic factors structure them. Second, emerging and existing regional human threats were identified. Third, these human threats were linked to the potential drivers that maintain natural communities to identify the most informative metrics to monitor and track change.
• 3. Fish communities, water quality, habitat, and food resources were sampled concurrently in 18 ponds in 1999 and 2000. Three common fish species explained 98% of variation in numbers across systems. Based on ecological relationships, pH, depth, vegetation, prey, and community complexity were determined to maintain biodiversity of freshwater fish communities.
• 4. The primary human threats here included: development‐related, land‐use changes; non‐point source pollution; eutrophication from septic systems; and introduced species that are a byproduct of high human visitation. These are common threats in many rapidly urbanized areas and are likely to have relevance to many sites.
• 5. To track the impact of emerging threats to freshwater ponds related to increased human population, monitoring changes in water quality, vegetated habitat, fish diversity, and trophic interactions are recommended.

Copyright © 2008 John Wiley & Sons, Ltd.     

Livestock water productivity in mixed crop–livestock farming systems of the Blue Nile basin: Assessing variability and prospects for improvement

Water scarcity is a major factor limiting food production. Improving Livestock Water Productivity (LWP) is one of the approaches to address those problems. LWP is defined as the ratio of livestock’s beneficial outputs and services to water depleted in their production. Increasing LWP can help achieve more production per unit of water depleted. In this study we assess the spatial variability of LWP in three farming systems (rice-based, millet-based and barley-based) of the Gumera watershed in the highlands of the Blue Nile basin, Ethiopia. We collected data on land use, livestock management and climatic variables using focused group discussions, field observation and secondary data. We estimated the water depleted by evapotranspiration (ET) and beneficial animal products and services and then calculated LWP. Our results suggest that LWP is comparable with crop water productivity at watershed scales. Variability of LWP across farming systems of the Gumera watershed was apparent and this can be explained by farmers’ livelihood strategies and prevailing biophysical conditions. In view of the results there are opportunities to improve LWP: improved feed sourcing, enhancing livestock productivity and multiple livestock use strategies can help make animal production more water productive. Attempts to improve agricultural water productivity, at system scale, must recognize differences among systems and optimize resources use by system components.     

物料悬浮速度测试方法研究

悬浮速度是物料空气动力学的一个重要参数,一直是从事物料特性研究者关心的问题。但是国内外对物料悬浮速度测试的研究一直很少,主要以简单的机械机构控制和理论计算测试为主,存在着操作繁琐、计算复杂、数据误差大等缺点。为此,重点对比分析了几种物料悬浮速度测试方法的测试原理与特点,旨在为相关研究提供参考。     

基于Web的农机选型智能决策支持系统设计

根据农业机械在农业生产中的应用,结合计算机网络技术,设计了基于Web的农业机器选型智能决策支持系统;同时,阐述了其设计目标及原理,讨论和分析了系统的体系结构,给出了系统的4个主要功能模块,并确定了系统的总体结构。     

温室环境控制系统的MPT智能算法

针对温室环境的大滞后、多输入、多输出、非线性和难以建立数学模型等特点,对传统的PID算法进行改进,并加入自适应控制、模糊控制和专家自整定等智能控制功能,建立了MPT智能控制算法.在论域内用不同控制方式分段控制,当偏差大于某一域值时,根据操态选择模糊控制,不存在抗饱和积分问题,使用模糊控制规则确定输出;当偏差减小到域值以下时,切换转入MPT算法控制,减小响应过程中的超调,并最终消除余差.该算法具有无超调、控制精度高和鲁棒性强等特点..     

基于粗糙集的属性约简算法在农业机械中的应用

传统的利用区分矩阵进行属性约简算法,其时间复杂度和空间复杂度很大.近年来提出了各种启发式算法,其时间复杂度由原来指数级递增降到了平方级递增,但此算法并不能保证找到最优解.为此,提出了属性约简的改进算法,其在时间复杂度和空间复杂度上都降低很多,易于求出最优解.把此算法用于对一款农业机械的评估判断和规则提取,用VC++和SQL Server 2000进行实现,并通过专家数据验证其正确性.