CALIBRATION OF STORM LOADS IN THE SOUTH PRONG WATERSHED,FLORIDA, USING BASINS/HSPF1

ABSTRACT: The South Prong watershed is a major tributary system of the Sebastian River and adjacent Indian River Lagoon. Continued urbanization of the Sebastian River drainage basin and other watersheds of the Indian River Lagoon is expected to increase runoff and nonpoint source pollutant loads. The St. Johns River Water Management District developed watershed simulation models to estimate potential impacts on the ecological systems of receiving waters and to assist planners in devising strategies to prevent further degradation of water resources. In the South Prong system, a storm water sampling program was carried out to calibrate the water quality components of the watershed model for total suspended solids (TSS), total phosphorous (TP), and total nitrogen (TN). During the period of May to November 1999, water quality and flow data were collected at three locations within the watershed. Two of the sampling stations were located at the downstream end of major watercourses. The third station was located at the watershed outlet. Five storm events were sampled and measured at each station. Sampling was conducted at appropriate intervals to represent the rising limb, peak, and recession limb of each storm event. The simulations were handled by HSPF (Hydrologic Simulation Program‐Fortran). Results include calibration of the hydrology and calibration of the individual storm loads. The hydrologic calibration was continuous over the period 1994 through 1999. Simulated storm runoff, storm loads, and event mean concentrations were compared with their corresponding observed values. The hydrologic calibration showed good results. The outcome of the individual storm calibrations was mixed. Overall, however, the simulated storm loads agreed reasonably well with measured loads for a majority of the storms.     

Modelling nitrogen cycles of farming systems as basis of site- and farm-specific nitrogen management

The paper describes a model designed for analysing interrelated nitrogen (N) fluxes in farming systems. It combines the partial N balance, farm gate balance, barn balance and soil surface balance, in order to analyse all relevant N fluxes between the subsystems soil–plant–animal–environment and to reflect conclusive and consistent management systems. Such a system approach allows identifying the causes of varying N surplus and N utilisation.The REPRO model has been applied in the experimental farm Scheyern in southern Germany, which had been subdivided into an organic (org) and a conventional (con) farming system in 1992. Detailed series of long-term measuring data are available for the experimental farm, which have been used for evaluating the software for its efficiency and applicability under very different management, yet nearly equal site conditions.The organic farm is multi-structured with a legume-based crop rotation (N₂ fixation: 83 kg ha⁻¹ yr⁻¹). The livestock density is 1.4 LSU ha⁻¹. The farm is oriented on closed mass cycles.The conventional farm is a simple-structured cash crop system based on mineral N (N input 145 kg ha⁻¹ yr⁻¹). Averaging the years 1999–2002, the organic crop rotation reached, with regard to the harvested products, about 81% (6.9 Mg ha⁻¹ yr⁻¹) of the DM yield and about 93% (140 kg ha⁻¹ yr⁻¹) of the N removal of the conventional rotation. Related to the cropped area, the N surplus calculated for the organic rotation was 38 kg ha⁻¹ yr⁻¹ versus 44 kg ha⁻¹ yr⁻¹ for the conventional rotation. The N utilisation reached 0.77 (org) and 0.79 (con), respectively. The different structure of the farms favoured an enhancement of the soil organic nitrogen stock (35 kg ha⁻¹ yr⁻¹) in the organic crop rotation and caused a decline in the conventional system (−24 kg ha⁻¹ yr⁻¹). Taking account of these changes, which were substantiated by measurements, N surplus in the organic rotation decreased to 3 kg ha⁻¹ yr⁻¹, while it increased to 68 kg ha⁻¹ yr⁻¹ in the conventional system. The adjusted N utilisation value amounted to 0.98 (org) and 0.69 (con), respectively.     

湖泊水体中营养盐控制技术研究进展

营养盐物质是造成湖泊水体富营养化的关键因素,在对湖泊水体营养盐控制技术探讨过程中,分析了营养盐的来源形式,从物理、化学、生物生态学角度分别对营养盐的控制技术进行了论述和思考,并指出了今后湖泊水体中营养盐控制技术发展方向。     

Atmospheric deposition contributes little nutrient and sediment to stream flow from an agricultural watershed

Atmospheric deposition of nutrients within agricultural watersheds has received scant attention and is poorly understood compared to nutrient transport in surface and subsurface water flow pathways. Thus, we determined the deposition of phosphorus (P), nitrogen (N), and sediment in a mixed land use watershed in south-central Pennsylvania (39.5 ha; 50% corn–wheat–soybean rotation, 20% pasture, and 30% woodland), in comparison with stream loads at several locations along its reach between 2004 and 2006. There was a significant difference in deposition rates among land uses (P < 0.05) with more P and N deposited on cropland (1.93 kg P and 10.71 kg N ha⁻¹ yr⁻¹) than pasture (1.10 kg P and 8.06 kg N ha⁻¹ yr⁻¹) and woodland (0.36 and 2.33 kg N ha⁻¹ yr⁻¹). Although not significant, sediment showed the same trends among land uses. A significant relationship was found between P in deposition and P in soil <10-m away from the samplers suggesting much of the deposited sample was derived from local soil. Samplers adjacent to the stream channel showed deposition rates (1.64 kg P and 8.83 kg N ha⁻¹ yr⁻¹) similar to those on cropland. However, accounting for the surface area of the stream, direct deposition of P, N, and sediment probably accounted for <3% of P and <1% of N and sediment load in stream flow from the watershed (1.41 kg P, 27.09 kg N, and 1343 kg sediment ha⁻¹ yr⁻¹ at the outlet). This suggests that strategies to mitigate nutrient and sediment loss in this mixed-land use watershed should focus on runoff pathways.     

Ammonia stomatal compensation point of young oilseed rape leaves during dark/light cycles under various nitrogen nutritions

The plant can be a source or a sink of ammonia (NH₃) depending on its nitrogen (N) supply, metabolism and on the background atmospheric concentrations. Thus plants play a major role in regulating atmospheric NH₃ concentrations. For a better understanding of the factors influencing the NH₃ stomatal compensation point, it is important to analyse the dynamics of leaf NH₃ fluxes. The relationship between the leaf NH₃ fluxes and the leaf apoplast ammonium and nitrate concentrations, N nutrition and the light and dark periods was studied here.We designed an experiment to quantitatively assess leaf-atmosphere NH₃ exchange and the stomatal compensation point and to identify the main factors affecting the variation of NH₃ fluxes in oilseed rape. We tested day and night dynamics as well as the effect of five different N treatments. Two experimental methods were used: a dynamic open flux chamber and extraction of the apoplastic solution.Chamber measurements showed that there was a good correlation between plant NH₃ fluxes and water fluxes. Compensation points were calculated by two different methods and ranged between 0.8 and 12.2 μg m⁻³ NH₃ (at 20 °C) for the different N treatments. Apoplastic solution measurements showed that there was no significant differences in the apoplastic NH₄⁺ concentrations ([NH₄⁺]_apo) extracted in dark and light periods for the same N treatment. Statistical analysis also showed that [NH₄⁺]_apo was correlated with [NH₄⁺] in the nutrient solution and weakly correlated with [NO₃⁻]. Apoplast NH₄⁺ concentrations ranged between 0.1 and 2.1 mM, bulk tissue NH₄⁺ concentrations between 3.9 and 6.6 mM and xylem concentrations between 2.4 and 6.1 mM depending on the N supply.Calculated NH₃ emission potential from the extraction measurements were over-estimated when compared with the value calculated from chamber measurements. Errors related to chamber measurements included separation of the cuticular and stomatal fluxes and the calculation of total resistance to NH₃ exchange. Errors related to the extraction measurements included assessing the amount of cytoplasmic contamination. We do not have another method to assess the NH₃ stomatal compensation point and the choice between these two measurement techniques should depend on the scales to which the measurements apply and the processes to be studied.     

水泥行业SO2和NOX排放总量核算方法选取

就水泥企业SO₂和NO_X排放总量核算方法的选取问题,以3家不同类型水泥企业为例,以监测数据法核算结果为依据,对排污系数法和物料衡算法的核算结果进行统计学描述和差异性检验。结果表明:排污系数法能基本反映各类企业SO₂、NO_X实际排放状况;物料衡算法不适合各类企业NO_χ的总量核算;对含熟料生产线的水泥企业,物料衡算法核算得出的SO₂排放量偏小,实际工作中不建议采用;对粉磨站水泥企业,物料衡算法与排污系数法均能反映实际SO₂排放情况,建议以"取大值"原则选取。     

湘江干流水体无机氮污染现状分析

于2009年1月(枯水期)、5月(繁殖期)和9月(索饵期)对湘江流域湖南段5个监测区域(衡阳、株洲、湘潭、长沙和岳阳)29个监测位点进行水体无机氮污染的分布特征及时空变化进行调查与分析.结果表明:湘江流域湖南段的索饵期无机氮含量最高为1.71 mg/L,其次是越冬期1.14 mg/L,最低的是繁殖期只有0.77 mg/...     

Environmental impacts of irrigated sugarcane production: Nitrogen lost through runoff and leaching

There is concern about environmental impacts of cropping in catchments of Australia's Great Barrier Reef, especially losses of nitrogen (N) from cropping systems. Sugarcane production in the Burdekin region in the dry tropics stands out from other crops/regions because it is grown with the highest applications of irrigation water and N fertiliser rates of any sugarcane producing region in Australia, attributes which may enhance losses of N. Little is known about N losses from sugarcane production systems, especially irrigated systems. We measured parts of the water and N balance over three sugarcane crops at three contrasting sites in different parts of the Burdekin region, covering a range of soil types/textures and irrigation managements. The experimental data were used to parameterise the APSIM-Sugarcane cropping systems model, and the model then used to ‘infill’ missing data and develop more complete water and N balances for each of the crops at the three sites. The model was also used to simulate long-term yields and N losses through runoff and leaching below the root zone at the sites under a range of N fertiliser and irrigation management practices. Unlike the experience in other cropping systems, N losses through runoff and leaching below the root zone were not higher at our sites than measured in rainfed sugarcane production systems. The long-term simulations showed there were clear opportunities for reducing N losses while maintaining yields through reducing N fertiliser application rates. Simulations results suggested that long-term N surpluses of 50 kg ha⁻¹ yr⁻¹, considerably less than those during the experiment or common in the study region, were sufficient to maintain yields but reduce N losses by 50-57%. So, N fertiliser management should aim to keep surpluses to that level. Improved irrigation management could also help reduce N losses but generally to a much lesser extent than reduced N fertiliser applications. Research is required to confirm these predicted benefits, and investigate potential interaction between N fertiliser and irrigation management practices, and impacts of other management practices.     

NOx photocatalytic degradation on active concrete road surface — from experiment to real-scale application

The use of titanium dioxide (TiO₂) as a photocatalyst in concrete pavements has received considerable attention in recent years due to its ability to decontaminate via photocatalytic processes. The objective of this study is to assess the effectiveness of activated concrete road in the degradation of nitrogen oxides (NO_x). We have used a TiO₂ and activated carbon (AC) permeable spray solution to coat concrete to assess its NO_x purifying ability. A number of experiments were undertaken to ascertain the conditions that affect NO_x purification. Indoor simulation experiments with active concrete road at optimum conditions show that it has good purification ability, self-regeneration and repetition ability, with a minimum decontamination rate for NO and NO₂ of 37.4% and 25.84%, respectively. Outdoor experiments show that the photodegradation of NO_x is related to light intensity and temperature. As the light intensity increases the reaction rate increases, and conversely as temperature increases the reaction rate decreases.     

Inhibition of decomposing leaf litter of Cinnamomum camphora on growth of Pharbitis nil and the alleviation effect of nitrogen application北大核心CSCD

In plant configuration of landscaping, herbaceous plant is often inter-planted with ornamental tree species. But unreasonable plant collocation may reduce the effectiveness of afforestation for the inhibition effect of tree on the growth of understory, and further more affect the greening effect. Camphor (Cinnamomum camphora) is widely planted in landscaping accompanying herbaceous plants including morning glory (Pharbitis nil). But camphor was reported to have allelopathic effect on its adjacent plant, therefore correct selection and collocation of plants has important significance to obtain good greening effect. This research aimed to study by a pot experiment the effects of decomposing leaf litter of Cinnamomum camphora on the growth, phenological traits of Pharbitis nil, as well as modification of these effects by nitrogen application. Three application rates of C. camphora leaf litter including 25, 50 and 100 g/pot (denoted by L25, L50 and L100, respectively) and a control (CK) were implemented. Nitrogen application began on the 34th d of decomposition, with 0.39 g urea being divided into three equal portions and added continuously to each pot. The results showed that (1) The height, basal diameter, leaf area and biomass production of Pharbitis nil were all inhibited sharply by exposure to the leaf litter, being decreased by 32.85%-83.78%, 5.23%-23.00%, 30.31%-58.47%, and 40.34%-84.54%, respectively, with the inhibition effect increasing both in intensity and stability with the increase of leaf litter. Such inhibition effect was obviously alleviated by exogenous nitrogen application. (2) The flowering dynamics of Pharbitis nil was greatly impacted by the leaf litter, with the flower initiation 2.5-10.0 d later and the flowering duration 6.3-11.4 d longer compared to the control. Although the leaf litter-treated plants exhibited more (0.5-3.3) flowers than the control, their quality decreased, and the hundred-grain weight of the seed decreased with the increase of leaf litter. However, the differences among treatments in the reproductive parameters mentioned above reduced after nitrogen fertilization. The results indicated that leaf litter of C. Camphora has a great allelopathic effect on morphological and reproductive growth of Pharbitis nil, which may be attributed to the release of phototoxic substances during the decomposition process.