A comparison of a persulfate digestion and the Kjeldahl procedure for determination of total nitrogen in freshwater samples

Precision and accuracy of the persulfate and Kjeldahl determinations of total nitrogen were assessed on 20 standards of known nitrogen concentrations and samples collected from a variety of aquatic habitats. The persulfate method was more precise than the Kjeldahl method for both sets of samples; accuracy and recovery of nitrogen from the samples were the same. Persulfate determinations should find wide application in laboratories analyzing freshwater samples for total nitrogen.     

凯氏定氮管蒸馏法测定土壤中的水解性氮

该方法采用凯氏定氮管做蒸馏装置,采用的是水蒸气加热蒸馏,使土壤样品完全悬于溶液中反应更充分,土壤样品中水解性氮馏出时间更短、更彻底。使原来在40℃保温箱中24 h才能释放完全的水解性氮在短时间内就被蒸馏出并被吸收液吸收,能够快速而准确地测定土壤中的水解性氮,具有快速、准确性高、稳定性好、重复性好的优点。取5 g土壤样品,检出限为1mg·kg~(-1)。用于土壤样品中水解性氮的测定,结果满意。     

An automated procedure for the determination of total Kjeldahl nitrogen

A procedure for the determination of total Kjeldahl nitrogen in surface fresh waters and organic wastes is described. Organic nitrogen compounds are converted to ammonium sulphate by a catalytic (red mercuric oxide) acid-sulphate digestion. The digest time is 3 h and allows for a maximum of 36 samples, 2 blanks and 2 standards to be processed simultaneously. There is no pH adjustment required following the digestion. Calibration curves covering the ranges (i) 0.5–100 μg NH₃---Nl⁻¹ and (ii) 10–1000 μg NH₃---Nl⁻¹ were linear within ±2%. The detection limit of the method is 0.5 μg TKNl⁻¹. The concentration range of TKN for which the method is suitable is 0.5 μg Nl⁻¹–40 mg Nl⁻¹. The method displayed a high tolerance to interferences from copper, iron, mercury and hardness. Digest procedure gave a high recovery and reproductibility over a wide range of nitrogen compounds tested.     

再生水中氨氮和总氮的相关性分析研究

通过检测某再生水厂生活出水中的氨氮和总氮含量,分析了氨氮和总氮含量之间的相关性.结果表明,再生水中氨氮和总氮两个监测因子之间的相关关系为：秋季最好,R为0.992 5;冬季其次,R为0.934 6;最后是春季和夏季,R分别为0.777 0和0.725 7.氨氮和总氮含量之间的比例系数为0.010～0.310,波动较大,根据各不同季节氨氮和总氮的比例系数K季均值,可以得到氨氮和总氮含量的比例系数K年均值为0.078.     

Simultaneous determination of total nitrogen and total phosphorus in water using peroxodisulfate oxidation

A method by which the TN and TP in water samples can be determined simultaneously employing peroxodisulfate oxidation was developed.

A solution of 0.074 mol 1⁻¹K₂S₂O₈–0.075 mol 1⁻¹ NaOH was adopted for the oxidizer, which made it possible to carry out alkaline peroxodisulfate oxidation for TN and acid peroxodisulfate oxidation for TP in turn during a single autoclaving. The pH values changed from 12.57 to approx. 2.0 and the period of alkalinity was estimated at 1.42 min at 120°C. The products of oxidation were nitrates and orthophosphates and both were measured simultaneously by an AutoAnalyzer. Good recoveries of both nitrogen and phosphorus compounds were obtained. The method was excellent in terms of its simplicity, speed and efficiency in handling large numbers of samples.     

施工现场用电总负荷的确定

介绍了施工临时用电中反复短时工作制设备、小型电气设备、电焊机、不对称负荷设备容量的计算,并结合具体实例确定了施工现场的用电总负荷,以保证施工现场临时用电设计的合理性,从而确保工程顺利进行。     

Inorganic nitrogen release kinetics and exchangeable inorganic nitrogen of the sediments from shallow lakes in the middle and lower reaches of the Yangtze River region

Inorganic nitrogen (IN) release kinetics and exchangeable inorganic nitrogen (EIN) of the sediments from shallow lakes in the middle and lower reaches of the Yangtze River region were investigated. The results showed that the EIN contents of the studied sediments ranged from 131 to 274 mg/kg. With the increase of the total nitrogen (TN) contents, their EIN also significantly increased. Their ratios of EIN to TN ranged from 5 to 17%, and with the increase of their TN contents, their ratios decreased. The relative contribution of NH₄⁺‐N and NO₃^‐N to EIN ranged from 83 and 11% to 89 and 17%, respectively. The curves of the NO₃^‐N release kinetics of the studied sediments were not completely consistent with those of IN and NH₄⁺‐N. The amounts of the IN released from sediments not only relate to their EIN contents, but also to other N fractions.     

Improved calibration of a rainfall‐pollutant‐runoff model using turbidity and electrical conductivity as surrogate parameters for total nitrogen

To address data scarcity for calibration of rainfall‐pollutant‐runoff (RPR) models, we evaluated the suitability of nutrient levels estimated based on surrogate parameters as a novel source of data, using runoff of total nitrogen (TN) in the Tegiru basin as a case study. A linear regression equation was developed for estimating TN based on turbidity and electrical conductivity; this expression was then used to generate TN data (n = 113) for calibration of a catchment‐specific RPR model. Using solely the estimated TN concentrations for calibration, the model accurately predicted TN concentrations (21% error based on measured TN, n = 13) and revealed runoff trends during periods in which TN measurements were lacking. Finally, we utilised this model to show that TN runoff was highest during months with frequent and high intensity rainfall. In summary, this study demonstrates the applicability of surrogate parameters to extend data on difficult‐to‐monitor nutrient loads for model calibration.     

Removal of organics and nutrients from food wastewater using combined thermophilic two-phase anaerobic digestion and shortcut biological nitrogen removal

A process combining pilot-scale two-phase anaerobic digestion and shortcut biological nitrogen removal (SBNR) was developed to treat organics and nutrients (nitrogen and phosphorus) from food wastewater. The thermophilic two-phase anaerobic digestion process was investigated without adjusting the pH of the wastewater for the pre-acidification process. The digested food wastewater was treated using the SBNR process without supplemental carbon sources or alkalinity. Under these circumstances, the combined system was able to remove about 99% of COD, 88% of TN, and 97% of TP. However, considerable amounts of nutrients were removed due to chemical precipitation processes between the anaerobic digestion and SBNR. The average TN removal efficiency of the SBNR process was about 74% at very low C/N (TCOD/TN) ratio of 2. The SBNR process removed about 39% of TP from the digested food wastewater. Conclusively, application of the combined system improved organic removal efficiency while producing valuable energy (biogas), removed nitrogen at a low C/N ratio, and conserved additional resources (carbon and alkalinity).     

棘洪滩水库沉积物对上覆水氮磷营养盐的影响

为了解青岛棘洪滩水库沉积物对水库水质的影响,分别在水库进水口（JSK）、库区中心（KX）和出水口（CSK）3个采样点采集库区沉积物,通过静态模拟吸附/释放实验,分析上覆水中氮磷营养盐含量变化.结果表明,除亚硝酸盐表现出微弱释放作用外,库区沉积物对氨氮、硝酸盐氮、总氮和总磷均表现出吸附作用,是氮磷营养盐的“汇”,并且不同采样点吸附能力也存在差异.其中出水口沉积物对总氮吸附作用最明显,吸附速率为4.80mg/（kg·d）,进水口沉积物对总磷吸附作用最强,吸附速率为0.06mg/（kg·d）.由此得出棘洪滩水库库区沉积物不会增加上覆水营养盐含量,库区水体营养盐可能主要来自引水.     

Determination of heavy metal uptake in transgenic plants harbouring the rabbit CYP450 2E1 using X-ray fluorescence analysis

Transgenic Sesbania grandiflora (L.) pers (Fabaceae) and Arabidopsis thaliana (L.) (Brassicaceae) plants harbouring the rabbit cytochrome p450 2E1 enzyme were evaluated for their ability to accumulate heavy metals, potassium (K), calcium (Ca), manganese (Mn), zinc (Zn), copper (Cu), iron (Fe), lead (Pb) and bromine (Br), using X-ray Fluorescence analysis. When grown for 15?days on heavy metal-contaminated soils, transgenic cuttings of S. grandiflora and T3 A. thaliana plants recorded higher dry and fresh weight compared with their respective controls (A. thaliana and S. grandiflora plants transformed with an empty vector). Dry weight of transgenic S. grandiflora plants (0.321?g) was seven times higher than that of the wildtype (0.049?g), and the fresh weight (4.421?g) was about 4.6 times higher. Likewise, the dry weight of CYP450 2E1 A. thaliana (0.198?g) was more than eight times higher than that seen in the control (0.024?g). Moreover, Fe, Mn, K, and Ca concentrations in transgenic plants were significantly higher than those in their corresponding controls. For instance, concentrations of accumulated K (~3000 and 2000?mg/kg dry weight in S. grandiflora and A. thaliana, respectively) were significantly higher than those recorded in their corresponding controls (2500 and 1500?mg/kg, respectively). In the same vein, translocation of all studied metals from soils cultured with transgenic plants was higher than in those cultured with the control plants. In conclusion, the obtained results show the potential in using transgenic Sesbania and Arabidopsis plants harbouring the rabbit CYP450 2E1 for phytoremediation of mixed environmental contaminants.     

Characteristics of organic nitrogen fractions in sediments of the shallow lakes in the middle and lower reaches of the Yangtze River area in China

The contents of different organic nitrogen (N) fractions, their contributions to total N (TN) and the relationship between their mineralisable N (MN) and different organic N fractions were investigated. Acid hydrophsable N (AHN) and nonhydrolysable N (NHN) accounted for 70.66 to 91.69% and 8.31 to 29.34% of TN. The AHN was the main organic N fraction, and its relative contribution to TN was higher than that in soil. So in terms of AHN contents and their contribution to TN, sediments are more hazardous than soils for lake eutrophication in the studied area. The ammonium N (AN), amino‐acid N (AAN), amino‐sugar N (ASN) and hydrolysable unidentified N (HUN) accounted for 30.51, 31.38, 6.42 and 31.69% of the total organic N, respectively. AN and AAN were the main sources of the MN in the studied sediments, which contributed to N release more than that of ASN and HUN.     

微波消解/流动注射光度法在线测定水中的总氮

利用微波在线消解水样，将流动注射分析技术与分光光度法相结合，建立了一种在线测定水中总氮的快速分析方法。在优化试验条件下，该方法对TN的检出限为0．04mg／L，对总氮含量为0．491mg／L的标准样品测定11次的相对标准偏差为1．2％。采用该方法测定河水、生活污水、工业废水水样中的TN含量，其相对标准偏差≤1％，加标回收率为97％～101％，结果令人满意。     

Determination of main components and anaerobic rumen digestibility of aquatic plants in vitro using near-infrared-reflectance spectroscopy

A near-infrared-reflectance (NIR) spectroscopy-based method is established to determine the main components of aquatic plants as well as their anaerobic rumen biodegradability. The developed method is more rapid and accurate compared to the conventional chemical analysis and biodegradability tests. Moisture, volatile solid, Klason lignin and ash in entire aquatic plants could be accurately predicted using this method with coefficient of determination (r²) values of 0.952, 0.916, 0.939 and 0.950, respectively. In addition, the anaerobic rumen biodegradability of aquatic plants, represented as biogas and methane yields, could also be predicted well. The algorithm of continuous wavelet transform for the NIR spectral data pretreatment is able to greatly enhance the robustness and predictive ability of the NIR spectral analysis. These results indicate that NIR spectroscopy could be used to predict the main components of aquatic plants and their anaerobic biodegradability.     

Characteristics and fate of organic nitrogen in municipal biological nutrient removal wastewater treatment plants

The aim of this study was to investigate the occurrence and fate of colloidal and dissolved organic nitrogen (CON and DON) across biological nutrient removal (BNR) activated sludge bioreactors. Primary and secondary effluent total nitrogen (TN) measurements and component fractionation, CON and DON concentration profiles across BNR bioreactors, and laboratory batch experiments with the process mixed liquor were carried out at several full-scale BNR plants in northern Poland. The organic nitrogen (ON) components were divided into high CON, low CON, and DON based on sequential filtration through 1.2, 0.45 and 0.1 μm pore-size filters. The average influent DON_0.1μm (<0.1 μm) concentrations ranged from 1.1 g N/m³ to 3.9 g N/m³ and accounted for only 4-13% of total organic nitrogen. In the effluents, however, this contribution increased to 12-45% (the DON_0.1μm concentrations varied in a narrow range of 0.5-1.3 g N/m³). Conversions of ON inside the bioreactors were investigated in more detail in two largest plants, i.e. Gdansk (565,000 PE) and Gdynia (516,000 PE). Inside the two studied bioreactors, the largest reductions of the colloidal fraction were found to occur in the anaerobic and anoxic compartments, whereas an increase of DON_0.1μm concentrations was observed under aerobic conditions in the last compartment. Batch experiments with the process mixed liquor confirmed that DON_0.1μm was explicitly produced in the aerobic phase and significant amounts of ON were converted in the anoxic phase of the experiments.     

Determination of Irgarol 1051 in Western Mediterranean sediments. Development and application of supercritical fluid extraction-immunoaffinity chromatography procedure

A supercritical fluid extraction (SFE) procedure for Irgarol 1051 (i.e. 2-(tert-butylamino)-4-(cyclopropylamino)-6-(methylthio)-1,3,5-triazine) determination in marine sediments, which minimises the solvent usage, is developed and compared to a conventional extraction technique (i.e. sonication). First, the use of methanol (MeOH) in the presence of trifluoroacetic acid (TFA) as secondary modifier of supercritical carbon dioxide was evaluated. Extraction efficiency was strongly dependent on the modifier content but lesser on pressure (100-410 bar) and temperature (60-200 degrees C). In the selected extraction conditions (20% MeOH/TFA 0.65M, 370 bar, 150 degrees C) recoveries higher than 87% were obtained and the limit of detection was 3 ngg(-1) and the relative standard deviation of 10% (N=3) by GC coupled to mass spectrometry (GC-MS) in the electron impact mode. The developed SFE procedure is more convenient to extract Irgarol 1051 than the agitation plus sonication methods concerning on solvent usage (1.5 vs. 20 mL) being compatible with immunochemical procedures avoiding any solvent transfer step. The developed SFE combined with immunoaffinity chromatography (IAC) is highly selective allowing the determination of Irgarol by gas chromatography with nitrogen-phosphorus detection or in sediments at low ngg(-1) level (11-35 ngg(-1)) from Mediterranean marina and harbour sediments.     

Characterization of bottom sediments in lakes using hydroacoustic methods and comparison with laboratory measurements

The acoustical properties of bottom sediments in two lakes were shown to be strongly correlated with clay content, organic C and total N concentrations, and other important sediment properties. The fractal dimension of the bottom echo was more strongly correlated with sediment physical and chemical properties than energy-based measures. The fractal dimension was also related to rates of PO₄-P and NH₄-N release from intact sediment cores and sediment oxygen demand. Measurements made at 430-kHz were more sensitive to differences in sediment properties than 201- or 38-kHz. Hydroacoustic measurements allow rapid assessment of properties important in lake restoration and water resource management.     

Application of pyrolysis-gas chromatography-mass spectrometry to the characterization of humic substances resulting from decay of aquatic plants in sediments and waters

Pyrolysis-GC-MS, elemental analysis and i.r. spectroscopy reveal major differences between humic substances from aquatic plants (algae and aquatic phanerogams) and lagoonal, marine and lacustrine deposits. Algae are enriched in proteins and their pyrolysis yields numerous nitrogenous by-products (alkylpyrroles, nitriles and alkylpyridines) along with aromatic compounds which are thought to reflect the decomposition of individual amino-acids (styrene, toluene, phenol and p-cresol). These compounds are less abundant in the pyrolysis products of humic substances from phanerogams with increasing amounts of methoxyphenols, characteristics of lignins.In the deposits of the Kerguelen Islands and of a “blue lake” in Greenland, the importance of algal populations is emphasized by pyrolysis products corresponding to nitrogenous and carbohydrate derivatives. Phenols and cresols in the pyrochromatograms of these samples are interpreted as evidence of polypeptides rather that lignin: p-cresol is much more abundant than the other cresols, suggesting the formation of phenols by way of tyrosine.Lagoonal sediments, in contrast, seem typical of intermixed development of algae and phanerogams.Differences between fulvic and humic acids are emphasized by the development of polyphenols and protein derivatives in humic acids compared to polysaccharide derivatives in fulvic acids. Other constituents revealed by PY-GC-MS include N-acetyl aminosugars, phthalates and aliphatic compounds.     

高压消解/流动注射光度法同时测定水中总氮与总磷

采用流动注射分析仪测定水中的总氮与总磷,结果显示,总氮在0.00～10.0 mg/L、总磷在0.00～1.00 mg/L的范围内,均可以获得良好的线性方程,相对误差<5%,相对标准差为1%～3%,方法的最低检出限分别为2.27μg/L和2.11μg/L,低于国标方法检出限,总氮的回收率为97.2%～108%,总磷的回收率为100%～106%,该方法适用于同时自动检测水中总氮与总磷的含量.     

Mercury in the River Nura and its floodplain, Central Kazakhstan: I. River sediments and water

The River Nura in Central Kazakhstan has been heavily polluted by mercury originating from an acetaldehyde plant. Mercury in the riverbed is mainly associated with power station fly ash, forming a new type of technogenic deposit. A systematic survey of the bed was carried out to establish the location, extent and nature of the contaminated sediments, and to evaluate the potential for sediment transport. The bed sediments were found to contain very high concentrations of mercury, particularly in the first 15 km downstream of the source of the pollution. Average total mercury concentrations in this section of the river are typically between 150 and 240 mg/kg, falling rapidly with increasing distance downstream. The estimated total volume of silts in the riverbed between Temirtau, the origin of the pollution, and Intumak Reservoir, located 75 km downstream, has been calculated as 463500 m3, containing an estimated 9.4 tonnes mercury. Forty-six percent of the total volume of contaminated silts containing almost 95% of the mercury are located in the upper 25 km of the river, however. The data clearly support the hypothesis that large quantities of polluted sediment are not transported long distances downstream but are removed from the aquatic environment in times of flood and deposited on the low-lying lands adjacent to the river. This process, however, does not stop mercury moving further downstream in the water column.