Continuous flow analysis of dissolved total phosphorus in seawater by UVK_(2)S_(2)O_(8) online digestion method

Several methods for analysis of dissolved total phosphorus in seawater were reviewed. Discussions were focused on UVirradiation and persulphate oxidation methods which are the most popular dissolved organic phosphorus determinationmethods presently. The compounds used for the phosphorus recovery test were categorized into three groups accordingto their chemical structure. It was found that low power UV irradiation can decompose POC or PC bonds efficientlybut may be inefficient for POP bonds. Heating-bath in acid condition is useful for decomposing POP bonds. Usingthe continuous flow analysis system (Auto-analyzer II), UV digestion and heating-bath, series experiments were carriedout based on the above analysis. Eleven model compounds were employed for the phosphorus recovery test and thefactors influencing the decomposition efficiency of dissolved compounds containing phosphorus were clarified. Finally,the optimal design for determination of dissolved total phosphorus in seawater based on the routine continuous flowanalysis system was presented. For the organic mono-phosphate, the recovery is more than 90% and a recovery of33%~51% was obtained for inorganic or organic polyphosphates. Up to now, this is the highest decompositionefficiency for dissolved phosphorus based on the continuous flow analysis system.

Effects of Conservation Methods of Water Samples on Determination of Total Phosphorus

Effects of conservation methods of water samples on determination of total phosphorus were analyzed from aspects of methods of adding conserving agent, SS concentration, natural sedimentation time, conservation temperature and time. The results showed that SS concentration in water and natural sedimentation time had the greatest impact on the determination of total phosphorus, while the influence of methods of adding conserving agent, conservation temperature and time was relatively smaller. TP concentration in water samples conserved irregularly was higher than the standard value due to the existence of SS and microorganisms in water, and the deviation became larger with the increase of SS concentration in water. In addition, quality control measures and matters needing attention during the conservation process of water samples were put forward to improve the accuracy of TP concentration.

TOTAL PHOSPHORUS RELEASE FROM BOTTOM SEDIMENTS IN FLOWING WATER

In this paper, the bottom of the Dianshan Lake was selected as a test sample. The dynamic release of contaminated sediments into the overlying water column was experimentally investigated in an open water channel under different hydrodynamic conditions. The experimental results indicate that the Total Phosphorus （TP） release process can be divided into three stages： rapid release, slow release and equilibration release. In the initial release stage the measured TP concentration changes along the depth. The TP concentration near the sediment-water interface is higher than that near the water surface, but the TP concentration becomes uniform along the depth after 3 h. The dynamic release of re-suspension sediment pollutants is about 6 times higher than the static release of sediment-water interface. There are three main types of release mechanism： diffusion release, re-suspended pore water mixing release and re-suspended particles desorbing release.

Desorption characteristics of total phosphorus and heavy metalsfrom impervious urban surface sediments

Dry sediments were collected from one roof and two roads in the central area of Beijing. The sediments were dry and wet sieved. The concentrations of total phosphorus (TP) and heavy metals were analyzed. The highest mass proportion of the dry sediments from the roads were between 125 and 300 μm in diameter, while the roof sediments were much smaller, with 75% of the total sediment mass between 40 and 74 μm in diameter. The concentrations of TP and heavy metals in the roof sediments were much higher than in the road sediments. The concentrations of the six heavy metals investigated had a similar order for all three sampling sites, with the Zn concentration always being the highest, followed by the Mn concentration, and the Ni concentration was always the lowest. After wet sieving, 76.9% to 91% of the TP in the sediments from the three sites remained in undesorbable particulate form, and 68.9% to 97% of the heavy metals were present in undesorbable particulate form. The concentrations of undesorbed heavy metals in the roof sediments tended to increase with increasing sediment size, but a similar trend was not found in the road sediments. This study shows that more attention should be given to the particulate matter in stormwater runoff, as reducing the amount of particulates will improve the efficiency of pollution control measures.

DISTRIBUTIONS OF TOTAL, INORGANIC AND ORGANIC PHOSPHORUS IN THE SEDIMENTS NEAR THE HUANGHE RIVER ESTUARY

For some hundred surface sediment samples from five cores taken in two cruises near the Huanghe River Estuary, total phosphorus (TP (.inorganic phosphorus (IP (and organic phosphorus (OP)were determined.On the average, 527×10-6, 455×10~6 and 72×10-6 were found for TP,IP and OP for the surface sediments taken in the two cruises. The distribution of OP and IP was controlled by the sample particle size: OP content increased with the decreasing of the sample particle size, while the maximal value of IP was found in the silt fraction due to the existence of apatite in our samples. Vertical distributions reflected well the channel change of the Huanghe River. Results from the multiple regressions between the three forms of phosphorus and the percentages of different particle size agreed well with the analytical data.

Optical anisotropy of black phosphorus by total internal reflection

Although abundant research on the anisotropy of van der Waals(vd W)materials has been published,we undertake an in-depth study of their optical properties as they have an important guiding role for light control in two-dimensional(2D)nanospace.As an example,we study the reflectance of few-layered black phosphorus(BP)in the total internal reflection(TIR)mode in detail.We demonstrate that its optical anisotropy can be changed on a large scale by varying the incident angles,polarization states,and the in-plane rotation angles of the BP samples.Theoretical analysis indicates that the phenomena observed are common to all the atom-thick biaxial crystals,so these conclusions can be widely applied to other anisotropic 2D materials.This research furthers the current understanding of the properties of BP more comprehensively,and provides guidance for developing new optoelectronic applications,especially when BP and other atom-thick biaxial crystals are integrated with TIR devices.

Bioturbation Effects of Benthic Fish on the Phosphorus Dynamic in Overlying Water of Paddy Field

[Objective]The research aimed to investigate the bioturbation effects of benthic fish Misgurnus anguillicaudatus on phosphorus dynamic in overlying water of paddy field,as well as to explore the bioturbation mechanism.[Method]Based on simulation experiment,the phosphorus contents in overlying water were analyzed comparatively with and without Misgurnus anguillicaudatus by the using of ion chromatography and spectrophotometry.[Result]The concentrations of total phosphorus(TP),dissolved total phosphorus(DTP)and particular phosphorus(PP)in bioturbation group had no significant differences with those in control group in initial stage of experiment,and became significantly higher than control group in middle and late stages of experiment(P<0.05). The PP/TP ratios in bioturbation group were bigger than those in control group,the increase of TP concentration in bioturbation group was mainly due to the increase of PP. The ratios of dissolved inorganic phosphorus(DIP) to DTP (DIP/DTP) were significantly bigger than those in control group in middle and late stages of experiment(P<0.05).[Conclusion]The benthic fish had bioturbation effects on phosphorus in overlying water of paddy field,which increased the available phosphorus for rice growth.

Effects of Phosphorus Concentration on the Treatment of Domestic Wastewater by a Combination of Hydrolytic Acidification and Biological Aerated Filter Filled with Mussel Shells

The combination of hydrolytic acidification and biological aerated filter （BAF） filled with mussel shells was used to treat domestic wastewater, and the removal rates of chemical oxygen demand （COD）, ammonia nitrogen （NH3-N） and total phosphorus （TP） by the system were analyzed under different TP concentrations. When TP concentration ranged from 12.39 to 14.69 mg/L, the removal rate of COD was the best, over 90.92% ; as TP concentration varied from 2.26 to 2.61 mg/L, the removal rates of NH3-N and TP were the best, up to 100.00% and 76.38% respectively. The results show that it is feasible to use mussel shells as the media of BAF, and TP concentration has certain influence on the performance of the system dealing with domestic wastewater.

Identifying Nonpoint Sources of Phosphorus and Nitrogen: A Case Study of Pollution That Enters a Freshwater Wetland (Laguna Cartagena, Puerto Rico)

Point and nonpoint sources of phosphorus (P) and nitrogen (N) can cause reductions in water quality, including eutrophication. Nonpoint pollution represents a special challenge because of dispersed not easily identifiable sources such as the runoff from soil, nutrients, and other chemicals from agricultural fields and residential areas. Laguna Cartagena is a tropical freshwater wetland, situated in southwestern Puerto Rico. It is a eutrophic ecosystem, and its eutrophication is caused by both external nutrient loading and internal, mainly by phosphorus. This wetland has been affected by phosphorus loading from inorganic agricultural fertilizer in this historically oligotrophic wetland system until the end of subsidized fertilizer use and sugar cane cultivation in the late 1990s. This study identifies: 1) nonpoint sources of phosphorus (SRP, Soluble Reactive Phosphorus and TP, Total Phosphorus) and nitrogen (nitrate, nitrite, and ammonia) that enter Laguna Cartagena;and 2) the role of precipitation events on the contributions of phosphorus and nitrogen loading to ecosystems. Herein we assess water samples from five channelized external sources of P and N that enter Laguna Cartagena at two-week intervals from October 2013 through November 2014. Rainfall data were obtained weekly from a rain gauge. Standard methods were used for all chemical analyses. Results showed that the channelized waterways that carry water to the lagoon can be classified as hypereutrophic (>100 μg/L) for TP concentrations and oligotrophic (<200 μg/L) for nitrogen concentrations. Currently agriculture (rice and cattle) is the predominant land use at the nearby University of Puerto Rico (UPR) Lajas Agricultural Experiment Substation, the predominant nonpoint source of nutrient pollution (SRP, TP and ammonia) in the principal channelized water sources to the lagoon. Current nutrient loads are likely derived from fertilizers applied to the Substation’s rice fields, and a high density livestock. The second important cause of external surface water degradation (SRP, TP and ammonia) is the discharge from rural households in the drainage basin that discharge greywater directly to the environment, as indicated by the results from Cerro Alto hills immediately to the north of the lagoon. Precipitation also was associated with SRP, TP and ammonia loads.

Storm phosphorus concentrations and fluxes in artificially drained landscapes of the US Midwest

This study investigates phosphorus (P) concentrations and fluxes in tile drains, overland flow, and streamflow at a high temporal resolution during 7 spring storms in anagricultural watershed in Indiana, USA. Research goals include a better understanding of 1) how bulk precipitation and antecedent moisture conditions affect P concentrations and fluxes at the watershed scale;2) how P concentrations and fluxes measured in tile drains translate to the whole watershed scale;3) whether P losses to the stream are significantly affected by overland flow. Results indicate that bulk precipitation and antecedent moisture conditions are not good predictors of SRP or TP losses (either concentration or flux) to the stream. However, along with previously published storm data in this watershed, results indicate a threshold-based behavior whereby SRP and TP fluxes significantly increase with precipitation when bulk precipitation exceeds 4 cm. Although total SRP and TP fluxes are very much driven by flow, SRP and TP fluxes are somewhat limited by the amount of P available for leaching for most storms. On average, SRP fluxes in tile drains are 13% greater than in the stream, and stream SRP fluxes account for 45% of TP fluxes at the watershed scale. Our results indicate that when P is the primary concern, best management practices aimed at reducing P losses via tile drains are likely to have the most effect on P exports at the watershed scale.

Regional Distribution of Soil Phosphorus Across Congregation-Grazing Zones of Forage-Based Pastures with Cow-Calf Operations in Florida

The arrangement of supplemental feed, water, shelter, and their concurrent interactions with topographic features may influence the distribution of animals and their simultaneous use of pasture’s resources. The effects of grazing and/or congregation management that control phosphorus cycling and distribution have not been sufficiently evaluated. The objectives of this study were: 1) to determine whether cattle congregation sites typical on most Florida ranches, repre-sented by water troughs and shaded areas, are more phosphorus-rich and may contribute more soluble phosphorus to surface water run-off and groundwater than other pasture locations;and 2) to assess the regional distribution of Mehlich-1 extractable soil phosphorus (MP) across congregation-grazing zones of forage-based pastures with cow-calf operations in Florida. Soil samples were collected at increasing distance from congregations structures (water troughs and shades) in established (>10 yr), grazed beef cattle pastures located in three Florida regions. Samples were col-lected in the fall and spring of 2005, 2006, and 2007, respectively;following a radial (every 90 degrees) sampling pat-terns away from the center of the congregation structures. Averaged across years, MP and soil phosphorus saturation in the congregation zones were comparable (p ≤ 0.05) with MP values and soil phosphorus saturation in the grazing zones at all three Florida regions. Average MP at all three pasture locations did not exceed the crop requirement threshold of 50 mg P kg–1 and the water quality protection threshold of 150 mg P kg–1, suggesting that congregation zones in beef cattle pastures at all three regions of Florida are not phosphorus-rich.

不同耕作方式与有机肥施用对旱地麦田土壤磷组分的影响

为探讨耕作措施和有机肥施用对旱地麦田土壤磷组分的影响,本研究依托2007年布设的黄土高原旱地小麦耕作与施肥长期定位试验,采用Tiessen磷素分级方法,系统研究了深翻+化肥(T)、深翻+鸡粪+化肥(TM)、免耕+化肥(NT)和免耕+鸡粪+化肥(NTM) 4种农艺措施下麦田0~20 cm土层有效磷、全磷和磷组分分布特征。结果表明:1) NT处理有效磷含量较T处理提高58.37%,有机肥处理(NTM和TM)有效磷和全磷含量均显著高于不施有机肥处理(NT和T),NTM处理的有效磷和全磷含量较TM处理分别显著提高11.43%和43.41%。2)与T处理相比,NT、NTM和TM处理可不同程度提高0~20 cm土层活性无机磷组分NaHCO_(3)-Pi以及中活性无机磷组分NaOH-Pi含量,尤其以NTM和TM处理效果最好。3) NT处理的NaHCO_(3)-Po和NaOH-Po较T处理分别显著提高53.07%和55.56%,NTM处理的这2种组分含量较TM处理分别显著提高90.84%和60.31%,Residual-P NT处理较T以及NTM处理较TM分别提高12.90%和36.60%。4)长期定位试验地每年施入的磷肥在土壤中有盈余,残留的磷主要以NaHCO_(3)-Pi、D.HCl-Pi、NaHCO_(3)-Po和C.HCl-Po形态存在,免耕增施有机肥促进了稳定性磷(C.HClPo)向活性磷(NaHCO_(3)-P)和潜在活性磷(NaOH-P)的转化;偏最小二乘(PLS)回归分析结果表明,NaHCO_(3)-Pi和NaOH-Pi是最有效的磷源,对小麦产量的提升贡献较大,NTM处理对这2种磷组分积累的促进效果最明显。综上免耕增施有机肥是发展黄土高原旱作农业值得推广的农艺措施,同时在推广应用时需要考虑减少化学磷肥用量。

连续流动-钼酸铵分光光度法测定土壤全磷

利用硫酸-高氯酸湿法消解土壤,采用连续流动分析仪直接测定消解液磷酸根含量,建立了高通量测定土壤全磷的实验方法。方法检测限6.0 mg·kg^(-1),土壤样品的加标回收率为85%~100%。将该方法用于土壤标准物质(GBW07405、GBW07406a)全磷含量测定,结果准确,相对标准偏差(RSD)分别为3.5%、4.5%(n=3)。方法具备无需调节待测液pH值、分析速度快、消耗试剂少、结果准确可靠等优点,适用于大批量土壤全磷的测定分析。

人造沸石和PFS去除城镇生活污水氨氮和总磷的实验研究

采用人造沸石和聚合硫酸铁(PFS)处理污水中氨氮和总磷,人造沸石实验采取连续进水模式,从沸石投加量、曝气量和流速(水力停留时间)多角度考察对污水中氨氮的去除,PFS实验从浓度、搅拌转速、混凝时间、沉降时间和取样深度多方面考察对污水中总磷的去除。结果表明:对于NH_(3)-N去除,单独曝气或人造沸石均效果不佳,去除率分别达10.01%±1.69%和49.49%±5.08%,但两者共同作用可极大提升去除效率,达90.55%±1.41%;水力停留时间在2.4~5.5 h范围内越长氨氮出水浓度越低,5.5 h时最低为(2.81±0.14)mg/L。对于TP去除,低浓度PFS(50、100 mg/L)表现出的去除效果不明显,去除率仅达6.62%~10.39%,至400 mg/L时去除率达89.58%±0.79%;转速110 r/min增加至205 r/min,TP去除率仅相差0.27%~3.77%;混凝时间由1 min增至10 min,去除率由52.36%±3.84%提升至87.30%±0.99%,且15 min为最佳沉降时间,之后TP质量浓度趋于平衡;不同取样深度对TP去除无较大影响;最佳实验参数组为PFS浓度400 mg/L,转速110 r/min,混凝10 min后沉降15 min,液面以下池深10%(约2 cm)处取样,出水TP质量浓度可达(0.17±0.01)mg/L,去除率达(89.58±0.79)%,明显优于GB 18918-2002一级A标准。人造沸石和PFS在城镇生活污水氮磷突发状况及深度处理,如某些工艺阶段设备突发事故导致不能运转的紧急情况或出水有深度处理需求的场合具有一定的技术研究和实际应用价值。

城郊结合带流域水体富营养化特征及来源分析

选取南昌市前湖水系为研究对象,运用对数型幂函数普遍适用的指数公式,对其进行富营养化程度评估。同时,进行相关性分析探究水质环境因素与水体富养化水平之间的相互关系。研究结果显示:前湖水系中高锰酸盐指数、氨氮、总磷、总氮、五日生化需氧量5种污染物含量呈现显著的空间分布特征;前湖水系水体富营养化指数(V E)介于51.34~70.52,均呈现水体富营养化,TN、TP与富营养化的相关性分别为0.917和0.912,表明氮磷是导致水体富营养化的主因;氮磷比平均值为19.57,污水处理厂排污、城区及周边的污染汇入等是南昌市前湖水系水体污染物的主要来源。对前湖水系进行研究,旨在提高对城郊结合部水环境的关注度。

结合光谱降维的IPSO-SVR水体总磷浓度预测模型

[目的]选择最优模型对水体中总磷浓度进行预测,为准确、实时、高效检测水资源状况提供支持。[方法]以2021年在长江中下游武汉—安徽地区采集的水质样本作为研究对象,首先,对采集到的长江光谱数据进行最大最小归一化和均值中心化两种预处理操作以便统一数据的范围和均值点,并使用核主成分分析(KPCA)技术对预处理后的光谱数据进行降维操作。选取方差解释率为99.6%下的6个特征向量进行后续预测模型的训练,接着在原有粒子群算法的基础上引入自适应惯性权重更新公式和遗传—模拟退火变异思想,提高算法的寻优能力。使用改进的粒子群优化算法对支持向量回归模型中的超参数组合进行寻优,对支持向量回归模型使用输出的结果进行预测模型的训练,最后使用测试集数据进行总磷浓度的预测。[结果]提出了一种结合光谱降维的改进粒子群优化算法(IPSO)结合支持向量回归(SVR)的水体总磷含量预测模型。通过和当前预测性能较好的几种机器学习模型进行精度的比较发现,该试验模型对长江水体总磷浓度进行预测时决定系数(R^(2))为0.973920,均方根差(RMSE)为0.003012,平均绝对误差(MAE)为0.002105。[结论]使用光谱数据结合降维技术、粒子群优化算法和机器学习模型的算法融合模型检测水体总磷浓度可行性强,精确度高,且拟合效果良好。

水中总磷的测定及不确定度评定

目的:测量水样中总磷含量并进行评定。方法:采用钼酸铵分光光度法进行测定,通过测量的重复性、标准溶液的配制和标准曲线的拟合等分量对测量中影响水样总磷含量结果的不确定度因素进行评定。结果:水样中总磷质量浓度的扩展不确定度为0.027 mg/L,总磷质量浓度为0.350 mg/L±0.027 mg/L。结论:标准溶液配制引入的不确定度为影响不确定度的主要因素,水样单从总磷质量浓度来看为Ⅳ类水质。

芡实对沿淮富营养化水体的净化效果研究

为了解乡土水生植物芡实对沿淮农村富营养化河流净化效果,在模拟沿淮农村地区富营养化河流的水池中种植芡实,定期监测水体中的总氮(TN)、氨氮(NH_(4)^(+)-N)、总磷(TP)、化学需氧量(COD_(Cr))、酸碱度(pH)、可溶性盐含量(EC)、溶解氧(DO)的数值变化,综合分析芡实对富营养化河流的净化效果。结果表明,芡实作为沿淮地区乡土水生植物,对富营养化的河流有着净化作用。芡实在生长过程中能吸收水体95.53%~98.45%的NH_(4)^(+)-N和99.50%~99.65%的TP,净化效果好。芡实对富营养河流中TN和COD_(Cr)的净化效果不明显,而且水体中的pH上升11.05%~11.61%,EC值增加21.12%~22%,DO增加3.82~21.77倍。芡实作为一种乡土水生植物,对沿淮地区富营养化河流具有显著的净化潜力。

可解释性长短期记忆模型用于预测湖泊总磷浓度变化

对湖泊总磷的变化预测和来源识别对水资源调度和流域生态治理有着重要的意义,然而复杂的生化反应和水动力条件导致的非平稳性给湖泊总磷浓度的准确预测带来极大的困难。为克服这一挑战,本文引入了基于加权回归的季节趋势分解(seasonal and trend decomposition using Loess,STL)技术和夏普利加法(SHapley additive exPlanations,SHAP)结合长短期记忆网络(long short-term memory neural network,LSTM)和门控循环单元(gated recurrent unit,GRU)构建了一个可解释的预测框架,以增强对湖泊总磷浓度演变的预测并提高其可解释性。研究表明:(1)在骆马湖总磷浓度的预测中,该框架拥有较好的预报精度(R^(2)=0.878),优于LSTM和卷积长短期记忆模型(convolutional neural networks and long short term memory network,CNN-LSTM)。当预测时间步长增加到8 h时,该框架有效提高了总磷浓度的预测精度,平均相对误差和均方根误差分别降低了47.1%和33.3%。从预测趋势来看,骆马湖在汛期的总磷平均浓度为0.158 mg/L,相较于非汛期的平均浓度,增加了202.1%。(2)运河来水是骆马湖总磷浓度最重要的影响因素,贡献权重为60.0%,并且不同断面(三湾、三场)的污染源受水动力、气象等因素的影响存在显著的时空差异。本文凸显了神经网络模型在预警水体污染方面的可实施性,并且为提高传统神经网络的学习能力和可解释性的开发与验证提供了重要方向。

耕作和秸秆还田对球囊霉素和土壤生态化学计量特征的影响

为探究耕作与秸秆还田对土壤球囊霉素相关蛋白含量、生态化学计量特征以及两者之间关系的影响,本研究选择长期进行作物生产的农场土壤,采集免耕、耕作和耕作秸秆还田三种处理下的0~20 cm土层土壤样品进行分析。结果表明,免耕土壤总球囊霉素含量为4.1 mg/g,较耕作土壤显著提高5.1%,耕作秸秆还田土壤较耕作土壤提高3.6%,免耕和耕作秸秆还田土壤易提取球囊霉素含量分别较耕作土壤提高4.8%和6.1%。免耕和耕作秸秆还田土壤有机碳含量分别为17.58、17.89 mg/g,较耕作土壤显著提高14.1%、16.1%;免耕土壤全氮含量为1.49 mg/g,较耕作和耕作秸秆还田土壤分别显著提高26.3%、17.3%。耕作秸秆还田土壤碳氮比达到14.47,显著高出免耕土壤33.2%。方差分解分析及线性相关分析表明,土壤有机碳、全氮含量影响球囊霉素的分泌和释放,免耕和耕作秸秆还田有利于提高土壤有机碳、全氮含量,从而促进球囊霉素的分泌,而长期耕作对丛枝菌根真菌分泌土壤球囊霉素具有限制作用。