Monitoring a flood event in a densely instrumented catchment, the Upper Eden, Cumbria, UK

Multi‐day rainfall events appear to be an important cause of recent flooding in the UK. Hydrological data from an extensive, nested hydrometric network in the unregulated, predominantly rural Upper Eden catchment in northern England are presented for one such flood event. These highlight antecedent catchment conditions and the propagation of the multi‐day flood event during February 2004. An assessment of flood response is provided over varying scales and land use between the upland Gais Gill catchment (1.1 km²) and the larger Upper Eden catchment (616 km²). Large spatial variations in rainfall totals are identified from a dense raingauge network during the flood event and are principally related to catchment elevation. High cumulative rainfall totals for the 6‐day event, particularly at upland sites appear to be the exceptional feature of the flood event with return periods in the order of 100 years at some upland gauges. Resultant patterns of flood attenuation and translation are quantified in different areas of the catchment, highlighting the flashy response of the headwater catchments and the attenuated downstream response in the lowland environment. The study forms part of the national Catchment Hydrology And Sustainable Management (CHASM) programme.     

Temporal variability of nitrate transport through hydrological response during flood events within a large agricultural catchment in south-west France

The temporal variability of nitrate transport was monitored continuously in a large agricultural catchment, the 1110 km² Save catchment in south-west France, from January 2007 to June 2009. The overall aim was to analyse the temporal transport of nitrate through hydrological response during flood events in the catchment. Nitrate loads and hysteresis were also analysed and the relationships between nitrate and hydro-climatological variables within flood events were determined. During the study period, 19 flood events were analysed using extensive datasets obtained by manual and automatic sampling. The maximum NO₃⁻ concentration during flood varied from 8.2 mg l⁻¹ to 41.1 mg l⁻¹ with flood discharge from 6.75 m³ s⁻¹ to 112.60 m³ s⁻¹. The annual NO₃⁻ loads in 2007 and 2008 amounted to 2514 t and 3047 t, respectively, with average specific yield of 2.5 t km⁻¹² yr⁻¹. The temporal transport of nitrate loads during different seasonal flood events varied from 12 t to 909 t. Nitrate transport during flood events amounted to 1600 t (64% of annual load; 16% of annual duration) in 2007 and 1872 t (62% of annual load; 20% of annual duration) in 2008. The level of peak discharge during flood events did not control peak nitrate concentrations, since similar nitrate peaks were produced by different peak discharges. Statistically strong correlations were found between nitrate transport and total precipitation, flood duration, peak discharge and total water yield. These four variables may be the main factors controlling nitrate export from the Save catchment. The relationship between nitrate and discharge (hysteresis patterns) investigated through flood events in this study was mainly dominated by anticlockwise behaviour.     

Atmospheric NH3 and NO2 concentration and nitrogen deposition in an agricultural catchment of Eastern China

To assess the atmospheric environmental impacts of anthropogenic reactive nitrogen in the fast-developing Eastern China region, we measured atmospheric concentrations of nitrogen dioxide (NO₂) and ammonia (NH₃) as well as the wet deposition of inorganic nitrogen (NO₃⁻ and NH₄⁺) and dissolved organic nitrogen (DON) levels in a typical agricultural catchment in Jiangsu Province, China, from October 2007 to September 2008_. The annual average gaseous concentrations of NO₂ and NH₃ were 42.2 μg m⁻³ and 4.5 μg m⁻³ (0 °C, 760 mm Hg), respectively, whereas those of NO₃⁻, NH₄⁺, and DON in the rainwater within the study catchment were 1.3, 1.3, and 0.5 mg N L⁻¹, respectively. No clear difference in gaseous NO₂ concentrations and nitrogen concentrations in collected rainwater was found between the crop field and residential sites, but the average NH₃ concentration of 5.4 μg m⁻³ in residential sites was significantly higher than that in field sites (4.1 μg m⁻³). Total depositions were 40 kg N ha⁻¹ yr⁻¹ for crop field sites and 30 kg N ha⁻¹ yr⁻¹ for residential sites, in which dry depositions (NO₂ and NH₃) were 7.6 kg N ha⁻¹ yr⁻¹ for crop field sites and 1.9 kg N ha⁻¹ yr⁻¹ for residential sites. The DON in the rainwater accounted for 16% of the total wet nitrogen deposition. Oxidized N (NO₃⁻ in the precipitation and gaseous NO₂) was the dominant form of nitrogen deposition in the studied region, indicating that reactive forms of nitrogen created from urban areas contribute greatly to N deposition in the rural area evaluated in this study.     

液氮冻结技术在地铁端头井加固中的应用

液氮冻结具有系统简单、冻结速度快、温度低和冻土强度高等特点,在城市地下工程建设中得到广泛应用。为了对某一地铁端头井进行加固,保证盾构机进洞安全,利用液氮冻结技术进行加固。经现场温度实测与分析,冻结效果达到了设计要求。运用数值模拟软件对液氮冻结和常规盐水冻结效果进行模拟,结果表明,液氮冻结土体5d左右就基本交圈,而常规盐水冻结需要30d左右才可以交圈,充分显示了液氮冻结技术低温、快速等优点。     

Quantitative assessment of groundwater vulnerability using index system and transport simulation, Huangshuihe catchment, China

Groundwater vulnerability assessment has been an increasingly important environment management tool. The existing vulnerability assessment approaches are mostly index systems which have significant disadvantages. There need to be some quantitative studies on vulnerability indicators based on objective physical process study. In this study, we tried to do vulnerability assessment in Huangshuihe catchment in Shandong province of China using both contaminant transport simulations and index system approach. Transit time of 75% of hypothetical injected contaminant concentration was considered as the vulnerability indicator. First, we collected the field data of the Huangshuihe catchment and the catchment was divided into 34 sub areas that can each be treated as a transport sub model. Next, we constructed a Hydrus1D transport model of Huangshuihe catchment. Different sub areas had different input values. Thirdly, we used Monte-Carlo simulation to improve the collected data and did vulnerability assessment using the statistics of the contaminant transit time as a vulnerability indicator. Finally, to compare with the assessment result by transport simulation, we applied two index systems to Huangshuihe catchment. The first was DRASTIC system, and the other was a system we tentatively constructed examining the relationships between the transit time and the input parameters by simply changing the input values. The result of comparisons between the two index systems and transport simulation approach suggested partial validation to DRASTIC, and the construction of the new tentative index system was an attempt of building up index approaches based on physical process simulation.     

Predicting runoff-induced pesticide input in agricultural sub-catchment surface waters: linking catchment variables and contamination

An urgent need exists for applicable methods to predict areas at risk of pesticide contamination within agricultural catchments. As such, an attempt was made to predict and validate contamination in nine separate sub-catchments of the Lourens River, South Africa, through use of a geographic information system (GIS)-based runoff model, which incorporates geographical catchment variables and physicochemical characteristics of applied pesticides. We compared the results of the prediction with measured contamination in water and suspended sediment samples collected during runoff conditions in tributaries discharging these sub-catchments. The most common insecticides applied and detected in the catchment over a 3-year sampling period were azinphos-methyl (AZP), chlorpyrifos (CPF) and endosulfan (END). AZP was predominantly found in water samples, while CPF and END were detected at higher levels in the suspended particle samples. We found positive (p<0.002) correlations between the predicted average loss and the concentrations of the three insecticides both in water and suspended sediments (r between 0.87 and 0.94). Two sites in the sub-catchment were identified as posing the greatest risk to the Lourens River mainstream. It is assumed that lack of buffer strips, presence of erosion rills and high slopes are the main variables responsible for the high contamination at these sites. We conclude that this approach to predict runoff-related surface water contamination may serve as a powerful tool for risk assessment and management in South African orchard areas.     

Nitrogen pollution and source identification in the Haicheng River basin in Northeast China

A survey was conducted in the Haicheng River near Liaodong Bay to analyze the characteristics and sources of the in-stream nitrogen pollution throughout the year 2010. The results indicated that the total nitrogen (TN) concentrations in the river water all exceeded the GB3838-2002 standard for Class V guideline of 2.0 mg/l at all sampling sites during the sampling seasons. Ammoniacal nitrogen (NH₃-N) dominated TN during the spring season, while nitrate nitrogen (NO₃-N) dominated during the summer and autumn seasons. Different forms of nitrogen had significant seasonal variations (p < 0.01 or p < 0.05). Only NH₃-N and NO₃-N displayed distinct spatial differences at p < 0.05 and p < 0.001, respectively. Most forms of nitrogen were interrelated with physicochemical parameters during different seasons, displaying nitrification and denitrification processes that occurred in the river rather than seasonal biological demand. Based on the nitrogen parameters, the 30 sampling sites were divided into three clusters, by which the pollution sources from chemical nitrogen fertilizers, animal wastes, domestic sewage, and industrial wastewater were identified. Generally, the Haicheng River basin provided about 700 tons of the annual TN flux, contributing to the eutrophication of the Liaodong Bay and Bohai Sea.     

Thermal modelling of an industrial building with solar reflective coatings on external surfaces: case studies in China and Australia

Most industrial buildings rely almost entirely on air-conditioning systems to provide thermal comfort to staff and customers who use the premises. As an alternative to this active approach, passive strategy is recommended to either fulfil this task or to help reduce energy consumption of air-conditioning systems already installed. Applying solar reflective coatings on external surfaces of the building, a key passive strategy, appears to offer an effective solution to reduce solar heat, especially during the summer, penetrating through the building fabric. This article discusses a study that uses computer thermal modelling to investigate the effectiveness of this strategy and to explore its contribution to operational energy savings. Detailed mathematical modelling in accordance with thermodynamic and heat transfer theories through the building fabric is illustrated and solutions to the mathematical problems are presented. The study consists of a comparison between two scenarios (normal coating and reflective coating) in three locations in China and one in Australia. The application of solar reflective coatings on external surfaces of the building produces energy savings for all the four locations and is found to be more beneficial in hot climates where there is a considerable need to reduce summer solar gains.     

An integrated modelling and multicriteria analysis approach to managing nitrate diffuse pollution: 2. A case study for a chalk catchment in England

The site-specific land use optimisation methodology, suggested by the authors in the first part of this two-part paper, has been applied to the River Kennet catchment at Marlborough, Wiltshire, UK, for a case study. The Marlborough catchment (143 km(2)) is an agriculture-dominated rural area over a deep chalk aquifer that is vulnerable to nitrate pollution from agricultural diffuse sources. For evaluation purposes, the catchment was discretised into a network of 1 kmx1 km grid cells. For each of the arable-land grid cells, seven land use alternatives (four arable-land alternatives and three grassland alternatives) were evaluated for their environmental and economic potential. For environmental evaluation, nitrate leaching rates of land use alternatives were estimated using SHETRAN simulations and groundwater pollution potential was evaluated using the DRASTIC index. For economic evaluation, economic gross margins were estimated using a simple agronomic model based on nitrogen response functions and agricultural land classification grades. In order to see whether the site-specific optimisation is efficient at the catchment scale, land use optimisation was carried out for four optimisation schemes (i.e. using four sets of criterion weights). Consequently, four land use scenarios were generated and the site-specifically optimised land use scenario was evaluated as the best compromise solution between long term nitrate pollution and agronomy at the catchment scale.     

扩散火焰在聚甲基丙烯酸甲酯(PMMA)上蔓延研究:理论、试验和数值模拟

对PMMA进行数字模拟和试验,对描述自然边界层扩散火焰理论的假设进行评价。我们把流动特性（二维边界层）和表面热平衡作为评价的关键假设。试验、数字模拟和理论模型证实了对质量传递数值定义的假设是正确的,但研究也表明,有必要对流动特性进行三维模拟。     

Changes of soil organic carbon in an intensively cultivated agricultural region: a denitrification-decomposition (DNDC) modelling approach

Regional modelling of soil organic carbon (SOC) dynamics is important for predicting large-scale patterns in carbon cycling and for assessing potential responses of soil carbon pools to land-use change. However, data uncertainties related to both spatial heterogeneity and small-scale differences in farming practice related to cropping systems affect the accuracy of regional models. A case study is presented from Quzhou County in the North China Plain, an area characterized by highly intensive farming. For this county, the DNDC model was validated using sampling data from 68 sites around the county under generalized farm practices. Unique modelling units based on soil type, soil texture and crop type were created and then used to model the spatial change of SOC under different farming practices. Considering the main factors affecting SOC sequestration, the results indicate that the DNDC model delivers acceptable modelling results at county level. The results show that there is a great potential for SOC sequestration in Quzhou County in its central, southern and eastern parts. Changes in farming practices show a strong effect on carbon sequestration. A very efficient and environmental friendly sequestration of SOC pools could be achieved even by decreasing nitrogen fertilizer inputs, when the amount of straw returned to the field is greatly increased.     

Biotic condition assessment and the implication for lake fish conservation: a case study of Lake Qionghai, China

Conserving fish in lakes requires the systematic analysis and assessment of fish species. The issues, conservation needs and fish assemblage changes are described for Lake Qionghai (China). The annual fishery production (AFP) was analysed from 1949 to 2003, which indicated a high disturbance of the aquatic ecosystem in Lake Qionghai caused especially by fisheries. The continuous increase in AFP and the introduction of economically important fish species have changed the fish species structure and diversity of the lake. Only five of 20 native fish species remained extant in 2003. The alien species accounted for 83.58% of the total fish production in 2003. Scoring criteria for 10 indexes of biotic integrity (IBI metrics) were selected for Lake Qionghai. The overall IBI score decreased from 40 in the 1940s to 26 in the 1980s to 20 in 2003. Changes in biotic condition were mainly caused by the destruction of fish physical habitat, pollution, bycatch and the invasion of alien species. Based on the IBI analysis, an ecosystem approach was developed for fish conservation in Lake Qionghai, including conservation at the watershed scale, habitat improvement and restoration, rebuilding of aquatic ecosystems and adaptive ecosystem-based fishery management.     

Landscapes,land covers and linear features in a river catchment in Northern England

A national land classification developed by the Institute of Terrestrial Ecology (ITE) was used to stratify a sample‐based survey of land cover and linear boundary features within the catchment of the River Tyne, Northern England. A total of 115 1‐km grid‐squares from four land classes representative of Lowland Pastoral, Lowland Arable, Marginal Upland and Upland landscapes were surveyed in the field. The land classes are described with an emphasis on the variability of land cover types and linear features. Considerable variation between squares of the same land class was observed, but statistically significant differences between the land classes were identified. Variation in the lengths of linear features was related to the land cover compositions of sample squares. The origins of the intra‐land class variation and the application of the ITE land classification in large‐scale surveys are discussed.     

Anthropogenic nutrient sources and loads from a Mediterranean catchment into a coastal lagoon: Mar Menor, Spain

The Mar Menor is a coastal lagoon increasingly threatened by urban and agricultural pressures. The main watercourse draining into the lagoon is the Rambla del Albujón. A fortnightly campaign carried out over one annual cycle enabled us to characterize the treated urban sewage effluents and agricultural sources which contribute to the nutrient fluxes in the watercourse. Multivariate analysis provided information for establishing chemical signatures and for assessing the relative influence of the various sources on the water quality at the outlet. Mass balances were used to examine net gains and losses, and cross-correlations with rainfall to analyze climatic influence and control factors in the trends of the nutrient flux. The rainfall pattern was significantly cross-correlated with nitrate and phosphorus fluxes from agricultural sources, while fluctuations in the resident population explained the phosphorus flux trend in urban sources. 50% of dissolved inorganic nitrogen was from agricultural sources, while 70% of total phosphate and 91% of total organic carbon were from urban point sources. The net amounts of all the nutrients fell as a result of plant uptake and/or denitrification in the channel. The control of urban point sources (phosphorus-enriched) is suggested as a promptly action for improving the health of the coastal lagoon.     

Transfer, distribution and bioaccumulation of microcystins in the aquatic food web in Lake Taihu, China, with potential risks to human health

In this paper, accumulation and distribution of microcystins (MCs) was examined monthly in six species of fish with different trophic levels in Meiliang Bay, Lake Taihu, China, from June to November 2005. Microcystins were analyzed by liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS). Average recoveries of spiked fish samples were 67.7% for MC-RR, 85.3% for MC-YR, and 88.6% for MC-LR. The MCs (MC-RR + MC-YR + MC-LR) concentration in liver and gut content was highest in phytoplanktivorous fish, followed by omnivorous fish, and was lowest in carnivorous fish; while MCs concentration in muscle was highest in omnivorous fish, followed by phytoplanktivorous fish, and was lowest in carnivorous fish. This is the first study reporting MCs accumulation in the gonad of fish in field. The main uptake of MC-YR in fish seems to be through the gills from the dissolved MCs. The WHO limit for tolerable daily intake was exceeded only in common carp muscle.     

某基坑工程支护方案的对比和探讨

以太原某一深基坑工程为研究背景,采用性价比较高的工程材料,结合理正软件,对基坑采用两种不同的支护形式进行数值模拟分析,研究了位移、弯矩、剪力随开挖深度的变化,得出一些可供实际工程参考的结论。     

Seeking a compromise between pharmaceutical pollution and phosphorus load: Management strategies for Lake Tegel, Berlin

Lake Tegel (Berlin, Germany) is controlled by two main inflows: inflow #1 (River Havel) is heavily phosphorus-laden, whereas inflow #2 is an artificial confluence that includes discharge from a municipal wastewater treatment plant distinguished by high levels of phosphorus and pharmaceuticals. To reduce the phosphorus load on the lake, a phosphorus elimination plant (PEP) is situated at inflow #2. Moreover, the two inflows are short-circuited by a pipeline that transfers part of the inflow #1 water to the PEP and finally releases it into inflow #2. The pipeline and the PEP have contributed to a continuous reduction in the total phosphorus concentration of Lake Tegel in the past 25 years. We investigate the question of whether the existing lake pipeline can also be used to reduce the amount of pharmaceuticals in Lake Tegel originating from inflow #2 by dilution with water from River Havel, by diverting part of inflow #2 around the lake, or by a combination of both strategies. The circulation pattern of Lake Tegel is complicated by complex bathymetry and numerous islands and is therefore highly sensitive to winds. We tested seven different management scenarios by hydrodynamic modeling for a period of 16 years with the two-dimensional version of the Princeton Ocean Model (POM). None of the scenarios provided a strategy optimal for both pharmaceuticals and phosphorus. Nonetheless, compound regimes, such as alternating the pipe flow direction or adding another pipeline, allowed the most abundant pharmaceutical (carbamazepine) to be reduced while maintaining the current phosphorus level. This study demonstrates the ability of immediate lake regulation measures to maintain water quality. In the case of Lake Tegel, the pipeline can be fully effective with regard to pharmaceuticals only in combination with additional efforts such as advanced pharmaceutical treatment of wastewater and/or phosphorus reduction in the River Havel catchment.     

双区域房间气流组织的数值模拟和实验研究

以双向风扇通风房间作为实验研究和数值模拟分析的对象,通过数值模拟给出了通风扇在排风和送风两种状态下双区域房间内三维空气流场分布,并与实验结果进行对比。研究结果表明利用数值模拟建立相应模型研究复杂形式房间内气流组织是可行的。此外,研究中发现房间风扇处于送风档更有利于室内空气的流动,气流组织状况明显优于风扇开在排风档状态。研究结果可以为通风设备的安装提供参考。     

Comparison of the simplified methods of the ISO 13790 standard and detailed modelling programs in a regulatory context

The CEN standards that support the European Energy Performance of Buildings Directive requirement for calculation of the energy consumption of buildings allow various methods to be used for the same calculation. The impact of using the different methods within the updated ISO 13790 standard for space heating and cooling energy calculations was examined with a parametric analysis of a common building specification. The impact was assessed by considering the energy band, which would be assigned for the building based on the calculation results. The standard describes three different methods that can be used for the calculations: a monthly quasi-steady state method, a simplified hourly method and detailed simulation. For most cases studied, differences in the building rating given by the various methods were a maximum of one band. More significant differences were noticed in some cases. Parameter values in the monthly method were determined, which would lead to improved matching.