Identifying critical sources of phosphorus export from agricultural watersheds

Surface runoff accounts for much of the phosphorus (P) input to and accelerated eutrophication of the fresh waters. Several states have tried to establish general threshold soil P levels above which the enrichment of surface runoff P becomes unacceptable. However, little information is available on the relationship between soil and surface runoff P, particularly for the northeastern United States. Further, threshold soil P criteria will be of limited value unless they are integrated with site potential for runoff and erosion. In response, the Natural Resource Conservation Service (NRCS) developed a P Index (PI), which ranks the vulnerability of fields as sources of P loss in runoff, based on soil P, hydrology, and land use. This study evaluated the relationship between soil and surface runoff P in a study watershed in central Pennsylvania. The relationship was then incorporated into the (PI), and its impact on the identification of critical source areas within the watershed was examined. Using simulated rainfall (6.5 cm h^–1 for 30 min), the concentration of dissolved P in surface runoff (0.2–2.1 mg l^–1) from soils was related (r²=0.67) to Mehlich-3 extractable soil P (30–750 mg kg^–1). Using an environmentally based soil P threshold level of 450 mg kg^–1 determined from the soil-runoff P relationship, the PI identified and ranked areas of the watershed vulnerable to P loss. The vulnerable areas were located along the stream channel, where areas of runoff generation and areas of high soil P coincide, and where careful management of P fertilizers and manure should be targeted.     

Estimation of phosphorus and potassium concentrations in Bermudagrass

Equations were developed to estimate concentrations of phosphorus and potassium for Coastal bermudagrass [Cynodon dactylon, (L.) Pers.] as related to applied nutrient level and harvest interval. Data from several field studies were used in the analysis. Estimates from these agronomic studies agreed with data from fertilizer and waste application for several locations. Concentrations of phosphorus and potassium decreased linearly with harvest interval (up to 6 weeks) and increased exponentially with nutrient level. This information should be relevant to crop production and environmental quality.     

Double-cropping annual ryegrass and bermudagrass to reduce phosphorus levels in soil with history of poultry litter application

Long-term application of poultry litter may result in excessively high soil phosphorus (P). This field study determined the potential of ‘Coastal’ bermudagrass overseeded with ‘Marshall’ annual ryegrass and harvested for hay to reduce the level of Mehlich-3 extractable P (M3-P) that had accumulated in a Savannah soil due to a 30-year history of broiler litter application to bermudagrass, as well as antecedent litter rates of 0, 4.48, 8.96, 17.9, and 35.8 Mg ha⁻¹ in 1999–2001. Following the cessation of litter, the plots were overseeded in fall 2001–2003 and fertilized in summer with 268 kg N ha⁻¹ as NH₄NO₃. Applying 8.96 Mg ha⁻¹ litter significantly elevated M3-P in surface soil (0–15 cm depth) from about 183 to 263 mg kg⁻¹. Annual dry matter (DM) yield and P uptake generally increased as litter rate increased up to 17.9 Mg ha⁻¹. Analysis of M3-P at four sampling dates from October 2002 to April 2004 found no significant effect of forage system or its interaction with litter rate, and levels in both systems decreased by about 25, 27, 22, 26, and 29% at the five litter rates, respectively. Ryegrass–bermudagrass significantly increased DM yield and P uptake, but did not translate to reductions in M3-P, as compared to bermudagrass winter fallow. With no further litter additions and five harvests per year, both forage systems removed about 49 kg ha⁻¹ P with a DM yield of 15 Mg ha⁻¹ and reduced M3-P by about 26 mg kg⁻¹ annually. Bermudagrass performance is important in the remediation of high soil P.

Simultaneous removal of carbon,nitrogen and phosphorus from wastewater by coupling two-step anaerobic digestion with a sequencing batch reactor

The objective of this study was to develop an integrated process for simultaneous removal of carbon, nitrogen and phosphorus from industrial wastewaters. The process consisted of a-two step anaerobic digestion reactor, for carbon removal, coupled with a sequencing batch reactor (SBR) for nutrient removal. In the proposed process, carbon is eliminated into biogas by anaerobic digestion: acidogenesis and methanogenesis. The volatile fatty acids (VFA) produced during the first step of anaerobic digestion can be used as electron donors for both dephosphatation and denitrification. In the third reactor (SBR) dephosphatation and nitrification are induced through the application of an anaerobic–aerobic cycle. This paper describes the first trials and experiments on the SBR and a period of 210 days during which the SBR was connected to the acidogenic and methanogenic reactors. It was shown that nitrification of ammonia took place in the SBR reactor, during the aerobic phase. Furthermore, denitrification and VFA production were achieved together in the acidogenic reactor, when the efflux of nitrates from the SBR reactor was added to the first reactor influx. The proposed process was fed with a synthetic industrial wastewater, the composition of which was: total organic carbon (TOC)=2200 mg dm⁻³, total Kjeldahl nitrogen (TKN)=86 mg dm⁻³, phosphorus under phosphate form (P-PO₄)=20 mg dm⁻³. In these conditions, removals of carbon, nitrogen and phosphorus were 98%, 78% and 95% respectively. The results show that the combination of the two-step anaerobic digestion reactor and an SBR reactor is effective for simultaneous carbon, nitrogen and phosphorus removal. Reactor arrangements enabled zones of bacterial populations to exist. Complete denitrification occurred in the acidogenic reactor and hence the anaerobic activity was not reduced or inhibited by the presence of nitrate, thus allowing high TOC removal. Stable phosphorus release and phosphorus uptake took place in the SBR after coupling of the three reactors. A fast-settling compact sludge was generated in the SBR with the operational conditions applied, thus giving good separation of supernatant fluid. The benefits from this process are the saving of (i) an external carbon source for denitrification and phosphorus removal, (ii) a reactor for the denitrification step. © 1998 Society of Chemical Industry     

景观型与蔬菜型水平潜流湿地除磷动力学模型

利用景观型和蔬菜型水平潜流湿地净化经生化处理后的生活污水尾水,进行湿地除磷动力学模型研究。对比分析不同湿地单元的除磷效率。为优化湿地除磷设计,采用一级动力学模型和Monod模型模拟除磷效果,对比模拟准确性,讨论水温、水力负荷与模型反应速率常数间关系,并建立湿地除磷模型构建式。结果表明,景观型湿地除磷能力顺序:美人蕉单元>再力花单元>鸢尾单元,蔬菜型湿地:空心菜单元>茭白单元>番茄单元,除磷效果差异归因于不同类植物的生物量区别。Monod模型(模型效率值ME:0.76～0.86)对湿地除磷的预测较一级动力学模型(ME:0.53～0.72)具有更高准确性。总磷面积去除率随水温的降低而减小,Arrhenius拟合结果表明,美人蕉(θ=1.006)、再力花(θ=1.008)和空心菜(θ=1.006)单元K_max对水温变化不敏感,水温对鸢尾(θ=1.015)和茭白(θ=1.014)单元除磷效率有较大影响。K_max20与水力负荷间存在显著正相关性,两者符合乘幂方程(R²:0.657;0.805)关系。考虑了水温和水力负荷因素的Monod模型构建式,对试验湿地除磷预测具备准确性。     

A simple equation for calculating the residual effect of phosphorus fertilizers

A simple equation to calculate the residual effect of fertilizer phosphorus is derived from a model distinguishing only two soil phosphorus pools. With time intervals of one year the model calculates the phosphorus transfers between the pools, the uptake of phosphorus by the crop and the resulting pool sizes. Most input data required to operate the model can be obtained from ordinary one-season phosphorus fertilizer trials.For easily soluble phosphorus fertilizers the residual effect can also be calculated with a formula: Rt = (0.8 – R1)^t-1* R1 where Rt and R1 are the recovery fractions in year t and year 1, respectively. During the first five years after fertilizer application the residual effects, as calculated with the equation, are almost equal to those obtained with the model.     

Estimating nutrient surplus and nutrient use efficiency from farm characteristics

Research on nutrient losses from agricultural systems should try to relate these losses to farm characteristics. This was done for private farms in two districts in Poland. Using data from a farm survey, nutrient surpluses and Nutrient Use Efficiency (NUE, defined as the ratio of outgoing and incoming nutrients) were calculated for nitrogen and phosphorus. Both nutrient surplus and NUE are relatively high. A model was developed to estimate surpluses and NUE from farm characteristics like location, farm size, fertilizer application level, animal density, grass production and sugar beet or potato area. The results of the model are satisfying for nutrient surplus (R2=0.9) and nitrogen NUE (R2=0.4). Estimation of phosphorus NUE was not satisfactory. High surpluses are associated with high fertilizer applications, high animal density and high grass production while an increasing share of sugar beets leads to lower surpluses. A high nitrogen NUE is associated with low fertilizer applications, low animal density and little grass production, and with a high sugar beet area share. Results suggest that, with exception of sugar beet, fertilizer recovery in Poland is very low. Sugar beet, however, combines high fertilizer applications with low surpluses and high NUE. The outcome of the model can be used in the design of environmental policies. The paper ends with some remarks on the type of measures that can be taken, and the effects these will have on private farms in Poland.     

The uptake and distribution of mineral nutrients in the banana in response to supply of K,Mg and Mn

The effects of differential K, Mg and Mn supply on the uptake and distribution of N, P, K, Ca, Mg, Na, Mn, Cu and Zn in the Williams banana were examined over the three crop cycles. Plants were grown in sand culture in 1 m³ drainage lysimeters.In terms of total plant uptake the standard solutions used were balanced in respect of P, K and Ca, possibly low in Mg and high in Mn, Cu and Zn compared with field grown plants. K and Mg supply influenced total plant uptake of most elements similar to the way they influenced dry matter production. Exception were total plant uptake of Mg and Cu. High Mn supply depressed the uptake of Mg and Cu and increased the uptake of Mn sevenfold.Increase in K supply reduced the proportion of all nutrients, except K, retained in the roots and increased the proportion located in the fruit. A large proportion (20–36%) of N, P and K were located in the fruit, Ca, Mg and Mn accumulated in the trash (29–44%) and roots were high in Na, Cu and Zn (29–50%).     

污水除磷脱氮与磷回收技术

磷作为一种不可再生资源,在现代工农业生产中起着重要的作用。但污水中大量P元素的排放,对环境造成了一定的影响。采用除磷脱氮工艺处理污水,不但可以有效回收磷,而且可以解决水体富营养化问题。     

A2N反硝化除磷脱氮工艺的影响因素分析

A2N(厌氧/缺氧和硝化)反硝化除磷脱氮工艺是基于反硝化聚磷菌缺氧吸磷理论开发的新工艺。介绍了A2N工艺的原理和特点,对其影响因素诸如水力停留时间、溶解氧、NO3-和NO2-的浓度、原水中COD与TN的质量比、容积交换比及出水SS等进行讨论和分析,并综合国内外的研究结果给出工艺关键影响参数的设定范围。     

Chemical nature and potential mobility of phosphorus in fertilized grassland soils

This paper describes results from a study of the effects of various applications of phosphorus (P) on the amounts, forms and potential mobility of P in grassland soils (0-7.5 cm) collected from four locations in the United Kingdom (Hertfordshire, Devon) and New Zealand (Taranaki, Canterbury). A sequential extraction scheme (NH₄Cl, NH₄F, NaOH I, H₂SO₄, NaOH II, residual P) designed to isolate P associated with aluminium (Al), iron (Fe) and calcium (Ca) was used to characterise P in the grassland soils from each location which had received various quantities of mineral fertilizer, organic manure and lime. Concentrations of total P in the soils ranged from 540 to 3,994 mg P kg^-1, and sequential extraction recovered 80–94% of total soil P. Extractable forms of inorganic P and organic P accounted for 40–52% and 31–50% of total soil P respectively. Inorganic and organic P present in the NaOH I fraction (P associated with Fe, Al and organic matter) accounted for most of the P which accumulated in soil from P inputs. Distribution of accumulated soil P between the various inorganic and organic P fractions appeared to be mainly controlled by the nature and availability of sorption surfaces which act as sinks for inorganic P. Phosphate sorption index data for the various soil sets indicated that the mean value of bicarbonate extractable inorganic P (Olsen P) which represented effective P saturation ranged from 61 to 217 mg P kg^-1. Potentially mobile soil P as determined by extraction with 0.01M calcium chloride (CaCl₂) was found to be most strongly correlated to the NH₄F, NaOH I and H₂SO₄ inorganic P fractions using a Freundlich isotherm.     

Processes controlling soil phosphorus release to runoff and implications for agricultural management

Phosphorus (P) loss from agricultural land to surface waters is well known as an environmental issue because of the role of P in freshwater eutrophication. Much research has been conducted on the erosion and loss of P in sediments and surface runoff. Recently, P loss in sub-surface runoff via agricultural drainage has been identified as environmentally significant. High soil P levels are considered as a potential source of P loss. However, without favourable hydrological conditions P will not move. In this paper, we review the basis of soil P release into solution and transport in surface and sub-surface runoff. Our objectives are to outline the role of soil P and hydrology in P movement and management practices that can minimize P loss to surface waters. Remedial strategies to reduce the risk of P loss in the short-term are discussed, although it is acknowledged that long-term solutions must focus on achieving a balance between P inputs in fertilizers and feed and P outputs in production systems. This revised version was published online in June 2006 with corrections to the Cover Date.     

电化学剥离黑磷制备纳米黑磷研究进展

纳米黑磷具有可调节直接带隙、高载流子迁移率等优点,在储能、催化等领域具有广阔的应用前景。然而,纳米黑磷应用的前提在于其高效制备。在制备纳米黑磷的诸多方法中,电化学剥离法通常在温和的反应条件下进行,操作简单、高效、可控性较强,是目前最有可能实现纳米黑磷低成本、规模化的可控制备方法。根据电化学剥离过程中原料黑磷的位置,电化学剥离可分为阳极剥离、阴极剥离和电解液剥离。为系统了解电化学剥离制备纳米黑磷的研究现状与发展前景,综述了3种不同电化学剥离方式制备纳米黑磷的研究进展,同时分析了3种剥离方式的优缺点及对应的剥离机制。最后对未来电化学剥离黑磷进行了展望,并提出阴极剥离由于制备的纳米黑磷种类丰富且氧缺陷少,是一种相对较优的实现纳米黑磷高效制备的电化学剥离方式。     

人工湿地污水处理技术

人工湿地是一种新型的污水处理技术。介绍了人工湿地污水处理技术的净化原理和构造特点,探讨了人工湿地系统的工艺设计,并给出了人工湿地的处理效果。     

活性污泥法脱氮除磷数学模型的发展

利用聚磷菌在缺氧条件下的吸磷和反硝化作用,实现氮、磷的同时去除,是具有实用前景的城市污水处理方法,而建立活性污泥法脱氮、除磷的数学模型则有利于该项技术的推广应用。文中对ASM2d模型、BarkerandDold模型、Delft模型作了较为详细的介绍,提出了由聚磷菌引起的缺氧吸磷和反硝化作用中需要解决的2个问题:反硝化聚磷菌浓度的确定和由反硝化聚磷菌吸磷所引起的磷的减少量。     

利用黄磷渣生产磷渣超微粉用于水泥添加剂

每生产1 t黄磷产出9~11 t黄磷渣。介绍利用黄磷渣生产磷渣超微粉(0.074~0.038 mm)的工艺及其作为水泥添加剂的成本和品质优势,并已成功将其用于修建大坝和商业用混凝土中,实现了黄磷渣的循环利用和保护了环境。     

不同电子受体配比对反硝化除磷特性及内碳源转化利用的影响

以A²/O-生物接触氧化(biological contact oxidation,BCO)系统反硝化除磷活性污泥为研究对象,通过投加不同浓度的NO₂^--N和NO₃^--N(30 mg·L^-1),考察了反硝化聚磷菌(denitrifying polyphosphate accumulating organisms,DPAOs)在不同电子受体配比(NO₂^--N:NO₃^--N0, 0.2:0.8, 0.4:0.6, 0.5:0.5, 0.6:0.4)条件下的脱氮除磷特性。结果表明:乙酸钠为DPAOs用于反硝化除磷的理想碳源,且其浓度为200 mg·L^-1时最佳;仅以NO₃^--N为电子受体进行缺氧吸磷反应时,NO₃^--N的投加量为30 mg·L^-1时较为合适;以NO₂^--N作为电子受体,未经 驯化的DPAOs,短时间内很难利用NO₂^--N,但低浓度的 (6 mg·L^-1)不会影响DPAOs以 作电子受体进行反硝化除磷;同时,NO₂^--N对于DPAOs吸磷作用的抑制程度明显强于 反硝化作用,当NO₂^--N浓度达到18 mg·L^-1时,吸磷反应基本停止;此外,较高浓度的NO₂^--N不仅会抑制聚羟基脂肪酸酯(poly-β-hydroxyalkanoate,PHA)的分解利用,且会使PHA分解产生的能量较多地用于储存糖原(glycogen,Gly),而所分解利用的PHA中90%以上为聚-β-羟基丁酸酯(poly-β-hydroxybutyrate,PHB)。     

推行磷酸生产精准管理提高磷的综合利用率

磷矿作为一种不可再生资源,供应日趋紧张,价格持续上涨。磷矿的供应情况在很大程度上决定着磷酸磷肥企业的生存与发展。作为资源消耗型企业,应千方百计挖掘磷资源利用的潜力。为此,从生产管理的角度探讨对磷酸生产各环节的精确计算与分析,有针对性地制定相应的措施,提高磷的综合利用率。     

黄磷尾气的净化方法探讨

黄磷尾气的主要成分是一氧化碳,可作为燃料和碳一化工原料。论述黄磷尾气的几种净化方法及其净化效果,并对净化后的尾气用途作了简单介绍。分析黄磷尾气净化的难点在于脱磷,尤其是P4。