Internal Loads and Bioavailability of Phosphorus and Nitrogen in Dianchi Lake,China

Sediments have a significant influence on the cycling of nutrient elements in lake environments. In order to assess the distribution characteristics and estimate the bioavailability of phosphorus and nitrogen in Dianchi Lake, organic and inorganic phosphorus and nitrogen forms were analysed. The 210 Pb radiometric dating method was employed to study temporal changes in the phosphorus and nitrogen pools in Dianchi Lake. The result show that the total phosphorus(TP) and total nitrogen(TN) were both at high concentrations, ranging from 697.5–3210.0 mg/kg and 1263.7–7155.2 mg/kg, respectively. Inorganic phosphorus(IP) and total organic nitrogen(TON) were the main constituents, at percentages of 59%–78% and 74%–95%, respectively, in the sediments. Spatially, there was a decreasing trend in phosphorus and nitrogen contents from the south and north to the lake centre, which is related to the distribution pattern of local economic production. The burial rates of the various phosphorus and nitrogen forms increased in same spatially and over time. Particularly in the past two decades, the burial rates doubled, with that TN reached to 1.287 mg/(cm^2·yr) in 2014. As the most reactive forms, nitrate nitrogen(NO_3-N) and ammonia nitrogen(NH_4-N) were buried more rapidly in the south region, implying that the potential for releasing sedimentary nitrogen increased from north to south. Based on their concentrations and burial rates, the internal loads of phosphorus and nitrogen were analysed for the last century. A TP pool of 71597.6 t and a TN pool of 81191.7 t were estimated for Dianchi Lake. Bioavailable phosphorus and nitrogen pools were also estimated at 44468.0 t and 5429.7 t, respectively, for the last century.

Environmental effects of mariculture in China:An overall study of nitrogen and phosphorus loads

Eutrophication in coastal area has become more and more serious and mariculture potential is a main cause.Although there are some quantitative research on nutrient loads in national and global perspective,the calculation method problems make the results controversial.In this paper,the farming activities are divided into fed culture types(include cage culture and pond culture)and extractive culture types(e.g.seaweed,filter-feeding shellfish culture).Based on the annual yield of China in 2019 and feed coefficient of fed culture types and carbon(C),nitrogen(N),and phosphorus(P)content of extractive culture types,the annual nutrient loads was estimated.The results showed that to coastal region of China(1)annual nutrient released by fed culture types were about58451 t of N,9081 t of P,and annual nutrient removed by harvest of extractive culture types were 109245 t of N,11980 t of P and 1.86×10^(6)t of C.Overall,the net amount of nutrient removed annually by mariculture industry were 50794 t of N and 2901 t of P.(2)The nutrient released from mariculture industry influenced nutrient stoichiometry.Pond farming and seaweed farming had the potential of increasing the molar concentration ratio of N and P(N:P),while cage farming and bivalve farming decreased the N:P.(3)Due to different mariculture types and layouts in the coastal regions in China,N and P loading were regional different.Among the coastal regions in China,net release of nutrient from mariculture occurred only in Hainan and Guangxi regions,while in the other regions,N and P were completely removed by harvest.We suggest decrease the amount of fed culture types and increase the amount of integrated culture with extractive culture types.This study will help to adjust mariculture structure and layout at the national level to reduce the environmental impact.

Influence of the concentration ratio of nitrogen to phosphorus on the growth and interspecies competition of two red tide algae

The growth and interspecies competition of two red tide algal species Thalassiosira pseudonana Hasle et Heimdal and Gymnodinium sp. were studied under different concentration ratios of nitrogen to phosphorus, and the algal hatch culture experiments were conducted. The physiological and biochemical indexes were measured periodically, including the maximum comparing growth rate, relative growth rate, average double time and chlorophyll a concentration. The results showed that when the concentration ratio of nitrogen to phosphorus was 16： 1, the maximum comparing growth rate, relative growth rate and chlorophyll a concentration of Thalassiosira pseudonana all reached the highest,and average double time was the shortest. This implied that the optimal concentration ratio of nitrogen to phosphorus of Thalassiosira pseudonana is 16： 1. When the concentration ratio of nitrogen to phosphorus was 6：1, the maximum comparing growth rate, relative growth rate and the chlorophyll a concentration of Gymnodinium sp. reached the highest, and average double time was the shortest, so the optimal concentration ratio of nitrogen to phosphorus of Gymnodinium sp. is 6： 1. From the growth curves as indicated both in the cell density and the chlorophyll a concentration, it is suggested that the influence of concentration ratio of nitrogen to phosphorus on the chlorophyll a concentration and the cell density are almost the same. Different concentration ratios of nitrogen to phosphorus had weak influence on community succession and the competition between the two algae. Gymnodinium sp. may use the phosphorus in vivo for growth, so it is important to pay attention to the concealment of phosphorus, in order to avoid the outbreak of red tide. On the basis of the importance of nitrogen and phosphorus and the ratio of their concentration, the possible outbreak mechanism of red tide of the two algae was also discussed.

Simultaneous nitrogen and phosphorus removal under low dissolved oxygen conditions

A full-scale test was operated by using low dissolved oxygen activated sludge process to enhance biological nitrogen and phosphorus removal. When the influent concentrations of CODCr, TN and TP varied in a range of 352.9 mg/L-1338.2 mg/L, 34.4 mg/L-96.3 mg/L, and 2.21 mg/L-24.0 mg/L, the average removal efficiencies were 94.9%, 86.7% and 93.0%, respectively. During the test period of two months, effluent meas of CODCr,, BOD5, NH3-N, TN and TP were below 50 mg/L, 25 mg/L, 10 mg/L and 1.0 mg/L respectively. The low dissolved oxygen activated sludge process has a simple flow sheet, fewer facilities and high N and P removal efficiency. It is very convenient to retrofit the conventional activated sludge process with the above process.

Characterization of the Growth,Chlorophyll Content and Lipid Accumulation in a Marine Microalgae Dunaliella tertiolecta under Different Nitrogen to Phosphorus Ratios

Microalgal lipids are regarded as main future feedstock of biofuels for its higher efficiency of accumulation and sus- tainable production. In order to investigate the effect of various nitrogen to phosphorus ratios on cells growth, chlorophyll content and accumulation of lipids in Dunaliella tertiolecta, experiments were carried out in modified microalgal medium with inorganic nitrogen （nitrate-nitrogen） or organic nitrogen （urea-nitrogen） as the sole nitrogen source at initial N：P ratios ranging from 1：1 to 32：1. The favorable N：P of 16：1 in the nitrate-N or urea-N medium yielded the maximum cell density and specific growth rate. Decrease in chlorophyll content were observed at the N：P of 4：1 in both nitrate-N and urea-N cultures. It was also observed that the maximum lipids concentration was obtained at the N：P of 4：1 in both nitrate and urea nutrient medium. The lipid productivity and lipid content of cultures in the urea-N medium at the N：P of 4： lwere markedly higher than those from cultures with other N：P ratios （p〈 0.05）. The results of this work illustrate the possibility that higher ratios of nitrogen to phosphorus have enhancing effect on cells growth of D. tertiolecta. Conversely, higher lipid accumulation is associated with a decrease in chlorophyll content under lower ratios of nitro- gen to phosphorus. The results confirm the hypothesis of this study that a larger metabolic flux has been channeled to lipid accumu- lation in D. tertiolecta cells when the ratios of nitrogen to phosphorus drop below a critical level.

Nitrogen and phosphorus removal under intermittent aeration conditions

A practice wastewater treatment plant was operated using intermittent aeration activated sludge process to enhance biological nitrogen and phosphorus removal. When the influent concentrations of COD Cr , BOD 5, TN, TP, NH 3\|N, TKN, and SS varied in a range of 207.5—1640 mg/L, 61.8—637 mg/L, 28.5—75.6 mg/L, 4.38—20.2 mg/L, 13.6—31.9 mg/L, 28.5—75.6 mg/L, and 111—1208 mg/L, the effluent means were less than 50 mg/L, 20 mg/L, 5 mg/L, 1.0 mg/L, 5 mg/L, 10 mg/L, and 20 mg/L, respectively. Based on a long time of operating results, this process is very suitable for nutrient biological removal for treating the municipal wastewater those water characteristics are similar as that of the Songjiang Municipal Waste Water Treatment Plant(SJMWTP).

Characteristics of diffuse pollution of nitrogen and phosphorous from a small town in the hilly area of the central Sichuan Basin,China

Hydrological and hydro-chemical monitoring of nitrogen(N) and phosphorus(P) in a small urbanized catchment was conducted in the hilly area of the central Sichuan Basin,China,from 2010 through 2011.The diffuse N and P loadings in different forms of total nitrogen(TN) and phosphorus(TP),dissolved nitrogen(DN) and phosphorus(DP),as well as particulate nitrogen(PN) and phosphorus(PP) were calculated based on runoff discharges and chemical analyses.The results revealed that the diffuse pollution concentrations of TN,DN,PN,TP,DP and PP exhibited large variations during rainfall events,with peak concentrations occurring during the initial period.For all of the measured parameters,the event mean concentrations(EMCs) were observed to clearly vary among rainfall events.The EMCs of TN,DN,PN,TP,DP and PP(for all of the observed rainfall events) were 10.04,6.62,3.42,1.30,0.47 and0.83 mg/L,respectively.The losses of diffuse N and P exhibited clear seasonal patterns and mainly occurred during the period from July through September,when the losses totaled 99.3 and 9.6 kg/ha for TN and TP,respectively,accounting for 75% and 74% of the total annual loadings.The mean annual loadings of TN and TP were 124.6 and 12.9 kg/ha,respectively.The results indicate that residential areas in the hilly areaof the central Sichuan Basin are subject to high diffuse N and P loadings,posing a serious risk to the receiving water quality.Ecological buffering belts are recommended to incorporate into the urbanized catchment to reduce diffuse pollution.

Process Adaption and Modifications of a Nutrient Removing Wastewater Treatment Plant in Sri Lanka Operated at Low Loading Conditions

The Sri Lankan national water authority, that is The National Water Supply and Drainage Board (NWS&DB) has taken a new wastewater treatment plant into operation at Ja Ela, North of Colombo. The plant has been in operation since September 2011. In April 2012, it was concluded how a test of the aeration efficiency and a performance test should be carried out. The tests have been based on the actual loading of the plant and the analysis results from the daily process control. The evaluation of the aeration efficiency is not reported in this paper. The paper presents the overall performance of the water treatment part of the plant during start-up conditions, from fall 2011 through the first five months of 2012. The results from the operation are found in Table 1. An important circumstance at the plant is the current very low loading in comparison with the design load. This fact has resulted in an introduction of an intermittent mode of the aeration (nitrification) reactor. Based on operation figures, during more than a month (May 2012), it has been possible to give a realistic assessment of the overall performance. The most striking results are summarized as follows: 1) The intermittent operation has enabled an energy efficient operation of the plant. By the introduction of the intermittent aeration, the energy consumption has been reduced by around 75%, compared with the continuous operation mode;2) The plant performance during the intermittent operation has been improved with respect to virtually all important pollution variables. The most striking improvement is the discharge total P level, reflecting that a substantial enhanced biological phosphorus removal takes. The typical discharge levels found during May 2012, were compared with the earlier obtained values. It is important to underline that the loading on the plant has slightly increased during May as compared with the previous operation period.

Harmful algal blooms and eutrophication: "strategies" for nutrient uptake and growth outside the Redfield comfort zone

While many harmful algal blooms have been associated with increasing eutrophication, not all species respond similarly and the increasing challenge, especially for resource managers, is to determine which blooms are related to eutrophication and to understand why particular species proliferate under specific nutrient conditions. The overall goal of this brief review is to describe why nutrient loads are not changing in stoichiometric proportion to the "Redfield ratio", and why this has important consequences for algal growth. Many types of harmful algae appear to be able to thrive, and/or increase their production of toxins, when nutrient loads are not in proportion classically identified as Redfield ratios. Here we also describe some of the physiological mechanisms of different species to take up nutrients and to thrive under conditions of nutrient imbalance.

Interactive effects of irrigation and exponential fertilization on nutritional characteristics in Populus 3 euramericana cv. ‘74/76' cuttings in an open-air nursery in Beijing, China

Nutritional characteristics determine tree stock quality to a considerable extent. Exponential fertilization can induce nutrient reserves within juvenile trees, but its validity on poplar is contingent on interaction with a scientific irrigation regime due to limited water resources under global warming. In the present study, we raised 3200 Populus 9 euramericana cv. ＇74/76＇ cuttings under four irrigation regimes of 0（I0）, 60 %（I60）, 80 %（I80）, and100 %（I100） of field capacity for soil moisture content with or without（control） the employment of nitrogen（N） addition delivered as exponential fertilization at the rate of 8 g N cutting^（-1）（E8） in an open-air nursery in Beijing, China. Both height and diameter increased with the increment of soil moisture ratio or in response to exponential fertilization（EF） without any interactive effects. In general, concentrations of N, phosphorus（P）,and potassium（K） declined with time in stem but foliar N concentration did not change. Under the I100 regime, EF increased foliar N concentration relative to the control but failed to affect N concentration in stem in September, when both N concentration and N content were increased by EF under the I80 regime. Stem-K content and concentration by EF under the I80 regime also increased in September,therefore EF-treated cuttings had a higher ratio of K content in stem to that in whole plant（%ANAR）. Vector diagnosis for nutritional status indicated that EF resulted in dilution of K concentration but induced a steady-state P uptake in leaves under all irrigation regimes. Therefore, EF of N addition could promote N uptake to leaves of P. 9 euramericana cv. ＇74/76＇ cuttings, but it had a null effect on N and P reserves in stem and impaired K reserves.In conclusion, the irrigation regime of 80 % field capacity of soil moisture content was suggested for the culture of juvenile P. 9 euramericana cv. ＇74/76＇ cuttings. As the interactive meaning, EF was also suggested for its excellent promotion on both N and K uptakes.

Bearing Capacity of Livestock and Poultry Breeding in Nanjing City Based on Planting-breeding Pattern

To assess the status of environmental beating capacity of livestock and poultry manure in Nanjing City, the environmental pollution warning value and environmental bearing potential of livestock and poultry manure in various districts of Nanjing were calculated according to livestock and poultry manure discharge coefticiem and manure content. The results showed that based on planting-breeding pattern, the livestock and poultry manure load in Nanjing City was 14.08 t/hm2 pig manure equivalent; the warning values of environmental bearing capacity of livestock and poultry breeding calculated by nitrogen and phosphor- us were 0.23 and 0.26, respectively, which were within the scope of environmental hearing capacity, with no threat to the environment. Under the premise of reasonable planing of livestock and poultry breeding and comprehensive utilization of manure, the environmental beating potential of livestock and poultry breed- ing in Nanjing City were 5. 667 3 million （nitrogen） and 11. 109 1 million （phosphorus） pigs equivalent, and there were nearly one third of bearing space more than the existing total breeding quantity.

Research on the Non-Point Pollution Loads in the Lake Uluabat Basin

Lake Uluabat, having an international significance and subject to the Ramsar Convention, is fed by the basin of Mustafakemalpasa Stream which runs through fertile lands utilized for livestock breeding and agriculture. In this study, total amount of nitrogen (TN) and phosphorus (TP) loads of non-point pollutants (agriculture, livestock breeding, vegetation, surface runoff and small settlements) was calculated. It was found out that most intensive pollution load stemmed from livestock breeding which causes dispersion of 13653.57 tons·year-1 of TN and 3224.45 tons·year-1 of TP into the Lake Uluabat. Additionally, seasonal changes in concentration of TN and TP were observed during the period of 2008-2009 in Lake Uluabat. It was concluded that the rise of agricultural activities in summer months was the reason underlying the increase in pollution during the months in question.

丹江口水库氮磷时空分布特征及水质安全保障对策

为加强丹江口水库及其上游流域水质安全保障,基于丹江口水库32个水质监测断面2017—2023年监测数据,分析丹江口水库水质及关键指标总氮和总磷的时空分布特征,核算水库氮磷的不同来源及贡献,评估水库富营养化及水华风险。结果表明:丹江口水库水质总体良好,以Ⅰ~Ⅱ类为主,总磷浓度基本保持稳定,总氮浓度波动上升;湖北库区总磷和总氮浓度高于河南库区,上游至下游呈降低趋势;2021年汛期出现持续强降雨,总磷和总氮浓度明显升高。入库河流水质稳定向好,Ⅰ~Ⅲ类占比逐渐上升,总磷和总氮浓度下降并趋于稳定;氮磷来源以上游流域污染输入为主,消落区淹没释放次之,沉积物释放影响较小;丹江口水库总体呈中营养状态,但部分水域在特定季节呈现富营养化,支流回水区和库湾水华时有发生,富营养化及水华风险不容忽视。建议加强库区上游流域污染源治理,严格消落区管理,提高水质监测预警能力,深化水质安全保障科学研究,加强体制机制建设。

白石水库总氮污染负荷分布组成特征分析

文章结合白石水库2011—2020年各形态氮及总氮浓度监测数据,研究分析了入库支流总氮输出浓度特征、水库总氮的变化趋势及其主要来源,结合实际情况提出水源区总氮防控对策。结果表明:近10a白石水库总氮浓度稍有增加,总体处于0.5~1.0mg/L之间;大凌河、牤牛河和凉水河等入库河流总氮浓度略高,其中面源对总氮贡献率约60%,硝态氮为总氮主要成分。

缓冲带截除农业面源强污染的效果

为了摸清草皮缓冲带对农田径流冲击负荷的耐受能力,通过工程尺度的现场试验,研究了高浓度污染负荷冲击对百慕大草皮缓冲带截除农业面源污染物能力的影响。结果表明:在高浓度污染负荷下,百慕大缓冲带能有效地截留农田径流中的悬浮固体(suspended solids,SS),SS浓度变化趋势与一般浓度污染负荷基本一致,前端下降速度较快,后端逐渐趋缓,2种污染负荷条件下末端出水SS质量浓度均在90mg/L以下,高浓度污染负荷冲击对农田径流SS的去除基本没有影响。缓冲带对高浓度氮磷污染负荷具有一定的净化效果,径流途径总氮(total nitrogen,TN)、氨态氮(ammonia nitrogen,NH4+-N)、总磷(total phosphorus,TP)的末端去除率为23%、16%和26%,分别为一般浓度污染负荷下末端去除率的59%、55%和70%;百慕大草皮缓冲带对渗流途径TN、TP具有一定的净化效果,2种浓度污染负荷下渗流水TN、TP浓度变化趋势基本一致,两者无显著差异(p>0.05),但TP去除速率较TN慢。该文为滨岸缓冲带的优化设计、维护管理及推广应用提供了依据。

紫色土区小流域不同土地利用类型非点源氮迁移特征

通过对紫色土区小流域旱地、居民点氮迁移过程的野外监测,研究紫色土区旱地、居民点氮流失特征。结果表明,地表径流是居民点氮迁移的主要途径,而旱地氮素主要通过壤中流迁移。次降雨事件中居民点氮迁移浓度、负荷变化显著,总氮(TN)、颗粒态氮(PN)、铵氮(AN)迁移呈现显著的"初始冲刷效应",初期25.0%的径流量携带了37.0%的TN负荷、60.0%的PN负荷和36.0%的AN负荷,而旱地径流中氮浓度、负荷变化较小。居民点氮流失与降雨量密切相关,旱地氮流失则集中在施肥后初期降水事件。旱地、居民点是紫色土区小流域氮流失的主要"源",其中旱地、居民点径流中TN年内浓度分别为16.43,14.68mg/L,TN年内流失负荷分别为41.18,222.05kg/hm2。

铜负载树脂去除电解锰废水中高浓度氨氮的研究

采用自制的铜负载D113树脂处理电解锰废水中高浓度氨氮,通过静态吸附试验,确定了最佳吸附与再生条件。模拟电解锰废水中氨氮的质量浓度为1 141.07 mg/L,在最佳试验条件下通过三级吸附交换,出水氨氮质量浓度为11 mg/L,达到GB 8978—1996《污水综合排放标准》要求,去除率达到99%;以1.5 mol/L的H2SO4作为再生剂对吸附饱和的树脂进行脱附再生,再生液多次脱附再生后可回用于电解锰生产工艺中,同时实现了废水的有效治理和资源的回收利用。

氮负荷和上升流速对单级自养脱氮工艺的效能分析

采用单级自养脱氮EGSB反应器处理质量浓度约为100 mg/L的低氨氮废水,考察了氮负荷和上升流速对反应器脱氮性能的影响。结果表明,逐步缩短HRT至2.0 h,且同步提高污泥区DO至0.32~0.36 mg/L,成功将反应器的氮负荷从100 mg/(L·d)提升至1 200 mg/(L·d),NH_4^+-N、TN平均去除率分别为93.0%和76.6%。反应器适宜的DO随氮负荷的提升而升高,对曝气量和上升流速的调控可实现对污泥区DO的精准控制。此外,EGSB较高的上升流速有利于保有较高生物量,确保反应器在较高氮负荷条件下保持稳定的脱氮性能。

污泥负荷对污水生物去除氮、磷和有机物的影响

分别改变进水浓度(C)、流量(Q)及污泥浓度(MLSS),通过对照实验考察污泥负荷改变对污水生物去除有机物、磷和氮效果的影响。结果表明:在本试验条件下,无论通过何种方式改变污泥负荷,对污水处理系统有机物、总氮和总磷去除率(ηCOD、ηTP和ηTN)均有显著影响,且ηTP受到的影响明显大于ηCOD和ηTN,而ηCOD受到的影响最小;污泥负荷改变的方式对反应器ηTP、ηCOD和ηTN也都存在不同影响。此外还讨论了提高污水处理装置净化效果的相关问题。

控制排水对油菜/黄豆农田土壤肥力及减排的影响——以漳河灌区为例

为探明控制排水对油菜/黄豆农田土壤肥力及减排的影响,于2018-2020年在湖北省漳河灌区开展3种不同控制排水处理的油菜/黄豆小区种植试验,采集各处理0~20 cm、20~40 cm及40~60 cm深度土样进行氮磷分析,监测典型时段排水水量及水质并计算氮磷排放负荷。结果表明,相较传统的自由排水FD处理,控制排水FL、CL均会造成0~20 cm土壤全氮流失,促使全氮向深层土壤迁移;控制排水FL、CL处理对20~60 cm土壤的保磷能力优于自由排水FD,土壤全磷向深层土壤迁移不明显;定出口高程FL处理削减氮磷浓度及排放负荷效果要显著优于变出口高程CL,相较自由排水FD,总氮、硝态氮、总磷浓度降低29.39%、15.99%、12.07%,负荷减排达73.93%、68.98%、67.54%。暗管出口控制深度0.6 m的控制排水处理(FL)是漳河灌区油菜/黄豆种植更优的排水模式。