Determination of influential parameters for prediction of total sediment loads in mountain rivers using kernel-based approaches

It is important to have a reasonable estimation of sediment transport rate with respect to its significant role in the planning and management of water resources projects. The complicate nature of sediment transport in gravel-bed rivers causes inaccuracies of empirical formulas in the prediction of this phenomenon. Artificial intelligences as alternative approaches can provide solutions to such complex problems. The present study aimed at investigating the capability of kernel-based approaches in predicting total sediment loads and identification of influential parameters of total sediment transport. For this purpose, Gaussian process regression(GPR), Support vector machine(SVM) and kernel extreme learning machine(KELM) are applied to enhance the prediction level of total sediment loads in 19 mountain gravel-bed streams and rivers located in the United States. Several parameters based on two scenarios are investigated and consecutive predicted results are compared with some well-known formulas. Scenario 1 considers only hydraulic characteristics and on the other side, the second scenario was formed using hydraulic and sediment properties. The obtained results reveal that using the parameters of hydraulic conditions asinputs gives a good estimation of total sediment loads. Furthermore, it was revealed that KELM method with input parameters of Froude number(Fr), ratio of average velocity(V) to shear velocity(U*) and shields number(θ) yields a correlation coefficient(R) of 0.951, a Nash-Sutcliffe efficiency(NSE) of 0.903 and root mean squared error(RMSE) of 0.021 and indicates superior results compared with other methods. Performing sensitivity analysis showed that the ratio of average velocity to shear flow velocity and the Froude number are the most effective parameters in predicting total sediment loads of gravel-bed rivers.

Assessment of total suspended sediment concentrations in Poyang Lake using HJ-1A/1B CCD imagery

We explored the potential of the environment and disaster monitoring and forecasting small satellite constellations (HJ-1A/1B satellites) charge-coupled device (CCD) imagery (spatial resolution of 30 m, revisit time of 2 days) in the monitoring of total suspended sediment (TSS) concentrations in dynamic water bodies using Poyang Lake, the largest freshwater lake in China, as an example. Field surveys conducted during October 17-26, 2009 showed a wide range of TSS concentration (3-524 mg/L). Atmospheric correction was implemented using the Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH) module in ENVI with the aid of aerosol information retrieved from concurrent Terra/Moderate Resolution Imaging Spectroradiometer (MODIS) surveys, which worked well at the CCD bands with relatively high reflectance. A practical exponential retrieval algorithm was created between satellite remote sensing reflectance and in-situ measured TSS concentration. The retrieved results for the whole water area matched the in-situ data well at most stations. The retrieval errors may be related to the problem of scale matching and mixed pixel. In three selected subregions of Poyang Lake, the distribution trend of retrieved TSS was consistent with that of the field investigation. It was shown that HJ-1A/1B CCD imagery can be used to estimate TSS concentrations in Poyang Lake over synoptic scales after applying an appropriate atmospheric correction method and retrieval algorithm.

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.

Horizontal distribution of Changjiang Diluted Water in summer inferred from total suspended sediment in the Yellow Sea and East China Sea

During the summer in the Yellow Sea and East China Sea, the resuspension of the bottom sediment is obstructed by strong stratification and, as a result, the concentration of total suspended sediment（TSS） can be used as an excellent tracer for Changjiang Diluted Water（CDW）. To analyze the spatial and temporal variations of the CDW distribution, the monthly mean TSS from Moderate Resolution Imaging Spectroradiometer（MODIS） ocean color data are constructed and are converted to salinity using the relationship between salinity observed from AQUARIUS and TSS. The process produces the detailed horizontal distribution of salinity with very high resolution（1 km）. From monthly mean salinity map from 2002 to 2012 in July and August, the expansion patterns of CDW are analyzed. The southerly wind in July and southeasterly wind in August transport the CDW eastward and northeastward, respectively. It is found that the yearly variation of the expansion of CDW toward the southern sea area of Korea is mostly due to the variation of southerly wind and the fluctuations of fresh water discharge into the Changjiang estuary show relatively little impact on the eastward extend of CDW. When 11-year mean（from2002 to 2012） salinity map in August is compared with World Ocean Atlas 2013, it is revealed that wind in August strengthened six times from 1994 and it causes the expansion of CDW extended 150 km further eastward.

The Status Assessment and Preliminary Risk Assessment of Total Mercury in Sediments from Middle and Lower Reaches of the Yarlung Zangbo River

The occurrence and accumulation of total mercury (T-Hg) in sediments collected from the Yarlung Zangbo River (YLZB),the Lhasa River,the Niyang River and the Palongzangbu River were analyzed and the soil samples simultaneously collected from the bank were employed as control.Meanwhile,pollution status and potential ecological risk of Hg were calculated and assessed using index of geoaccumulation ( I geo ) and potential ecological risk assessment method (Er) in this study.The results showed that the T-Hg concentrations in sediments at eight sections of YLZB ranged from 4.23 to 48.1 μg/kg with mean concentration of 25.1 μg/kg,which was higher than background Hg value of soils in Tibet.T-Hg concentrations in sediments at three typical segments of YLZB were all significantly higher than those in soils collected from its bank (P<0.05).The Igeo and E r indexes revealed that the T-Hg pollution levels were slight pollution in two sections and moderate ecological risk in six sections of YLZB.Hg pollution risks also existed in the sediments of partial sections of the Lhasa River and the Niyang River,and slightly moderate Hg contamination with high ecological risk was presented in Lhasa urban district.The level of Hg in sediments of YLZB showed a notable spatial distribution characteristic with a trend of increasing firstly and then declining.Human activities played an important role in increasing Hg content in sediments of the river.

An improved method for quantitatively measuring the sequences of total organic carbon and black carbon in marine sediment cores

Understanding global carbon cycle is critical to uncover the mechanisms of global warming and remediate its adverse ef fects on human activities.Organic carbon in marine sediments is an indispensable part of the global carbon reservoir in global carbon cycling.Evaluating such a reservoir calls for quantitative studies of marine carbon burial,which closely depend on quantifying total organic carbon and black carbon in marine sediment cores and subsequently on obtaining their high-resolution temporal sequences.However,the conventional methods for detecting the contents of total organic carbon or black carbon cannot resolve the following specific difficulties,i.e.,(1)a very limited amount of each subsample versus the diverse analytical items,(2) a low and fluctuating recovery rate of total organic carbon or black carbon versus the reproducibility of carbon data,and(3)a large number of subsamples versus the rapid batch measurements.In this work,(i)adopting the customized disposable ceramic crucibles with the microporecontrolled ability,(ii)developing self-made or customized facilities for the procedures of acidification and chemothermal oxidization,and(iii)optimizing procedures and carbon-sulfur analyzer,we have built a novel Wang-Xu-Yuan method(the WXY method)for measuring the contents of total organic carbon or black carbon in marine sediment cores,which includes the procedures of pretreatment,weighing,acidification,chemothermal oxidation and quantification;and can fully meet the requirements of establishing their highresolution temporal sequences,whatever in the recovery,experimental efficiency,accuracy and reliability of the measurements,and homogeneity of samples.In particular,the usage of disposable ceramic crucibles leads to evidently simplify the experimental scenario,which further results in the very high recovery rates for total organic carbon and black carbon.This new technique may provide a significant support for revealing the mechanism of carbon burial and evaluating the capacity of marine carbon accumulation and sequestration.

Evaluation of Total Hydrocarbons Levels and Traces Metals in Water and Sediment from Main Outfall Drain in Al-Nassiriya City/Southern Iraq

This study was conducted during Dec2011-Nov2012 on three stations located in the south sector of Main Outfall Drain (MOD) River. Station 1 was near Al-Holandee Bridge which was the general carriage way in the center of Al-Nassiriya city, station 2 was 20 km far from the first station, while station 3 was in the beginning of the new branch. This study reveals the Seasonal Variation of Total petroleum hydrocarbons (TPHs) in both surface waters, sediment and it is related with trace metals nickel and vanadium in water (dissolved, particulate) and sediment (residual and exchangeable) phases. Also, the study shows the relationships between the concentration of Ni and V with Total Organic Carbon (TOC%) in the sediment.

Sediment Transport in Rivers and Coastal Waters

Following Bagnold's approach, a relationship between sediment transport and energy dissipation is developed. The major assumption made in the study is that the near bed velocity plays a dominant role in the process of sediment transport. A general relationship between energy dissipation and sediment transport is first proposed. Then the equations for total sediment transport are derived by introducing the appropriate expression of energy dissipation rate under different conditions, such as open channel flows, combination of wave and current, as well as longshore sediment transport. Within the flows investigated, the derived relationships are fairly consistent with the available data over a wide range of conditions.

Impact of mangrove vegetation on seasonal carbon burial and other sediment characteristics in the Vellar-Coleroon estuary, India

This work quantified the total carbon and 12 other sediment characteristics at 10 soil depths, in planted and or natural mangrove forests in comparison with non-vegetated soil for four seasons of the year 2009-2010 in the Vellar-Coleroon estuarine complex, India. The sedi- ment characteristics varied significantly between mangrove-vegetated and non-vegetated habitats or seasons of analysis, but not between soil depths. The mangrove sediments were rich in total carbon and total or- ganic carbon as compared to non-mangrove sediments （p 〈0.01）. Total carbon was 98.2% higher in mature mangroves and 41.8% in planted mangroves than that in non-mangrove soil. Total organic carbon was as much as 2.5 times greater in mature mangroves and 2 times greater in planted mangroves than that in unvegetated soil. Carbon contents also varied many fold by season. Total carbon content was 8.6 times greater during pre-monsoon, 4.1 times greater during post-monsoon and 2.5 times greater during monsoon than during summer （P〈0.01 in all cases）. Similarly, total organic carbon was 5.9 times greater during pre-monsoon, 3.1 times greater during post-monsoon and 69% greater during monsoon than during summer. In general, higher levels of sediment carbon were recorded during pre and post-monsoon seasons than during other seasons. Total carbon concentration was correlated negatively to temperature, sand and phosphorus （P 〈0.01）; positively correlated with redox potential, silt, clay, C/N ratio, potassium （P 〈0.01） and nitrogen （P〈0.05）; but not correlated with soil depth, pH or salinity. This work revealed that the carbon burial was rapid at the annual rate of 2.8% for total carbon, and 6.7% for total organic carbon in mangrove-planted sediment. Cleating of mangroves can result in significantly and rapidly reduced carbon stores.Our study highlights the importance of natural and plantation mangrove stands for conserving sediment carbon in the tropical coastal domain.

Century-scale high-resolution black carbon records in sediment cores from the South Yellow Sea, China

Black carbon(BC)has received increasing attention in the last 20 years because it is not only an absorbent of toxic pollutants but also a greenhouse substance,preserving fire-history records,and more importantly,acting as an indicator of biogeochemical cycles and global changes.By adopting an improved chemothermal oxidation method(WXY),this study reconstructed the century-scale high-resolution records of BC deposition from two fine-grained sediment cores collected from the Yellow Sea Cold Water Mass in the South Yellow Sea.The BC records were divided into five stages,which exhibited specific sequences with three BC peaks at approximately 1891,1921,and 2007 AD,representing times at which the first heavy storms appeared just after the termination of long-term droughts.The significant correlation between the times of the BC peaks in the cores and heavy storms in the area of the Huanghe(Yellow)River demonstrated that BC peaks could result from markedly strengthened sedimentation due to surface runof f,which augmented the atmospheric deposition.Stable carbon isotope analysis indicated that the evident increase in carbon isotope ratios of BC in Stage 5 might have resulted from the input of weathered rock-derived graphitic carbon cardinally induced by the annual anthropogenic modulation of water-borne sediment in the Huanghe River since 2005 AD.Numerical calculations demonstrated that the input fraction of graphitic carbon was 22.97% for Stage 5,whereas no graphitic carbon entered during Stages 1 and 3.The obtained data provide new and important understanding of the source-sink history of BC in the Yellow Sea.

Coextraction of microbial metagenomic DNA and RNA from deep-sea sediment

A protocol to coextract the microbial metagenomic DNA and RNA from deep-sea sediment was developed for the microbiological study of environmental samples. The obtained pure metagenomic DNA with the size larger than 23 kb and stable RNA could be used directly for PCR and reverse transcription - PCR （ RT - PCR） respectively. The direct lysis including the treatments of SDS, proteinase and lysozyme was applied to acquiring the metagenomic DNA and RNA furthest. Prior to the lysis treatment, the glass bead and denaturing solution were added to enhance the lysis efficiency and keep the integrity of RNA respectively. Denaturing gradient gel electrophoresis （DGGE） was applied in accessing the microbial 16S rRNA diversity by PCR and RT -PCR amplification from a single extraction. The pattern obtained by this analysis revealed some differences between them, indicating the efficiency of the protocol in extracting the metagenomic DNA and total RNA from deep-sea sediment.

Sedimentary Organic Matter Characterization on a Tropical Continental Shelf in Northeastern Brazil

In continental shelf areas works where the focus is Geochemistry are widely relevant, due to the vast complexity and uses of these relief features (social, environmental and economic). On the Brazilian Northeast tropical shelves, with emphasis on the Pernambuco Continental Shelf (PCS), the published studies are limited and have aimed at portions closer to the coastline. The objective of the present work is the description of the characteristics and origin of sedimentary organic matter (SOM) in the inner and middle Pernambuco shelf, defining and classifying the local geochemical sedimentary facies. The sampling stations (136) were collected in the study area, and the grain-size, contents of total organic matter (TOM), calcium carbonate (CaCO3) were analyzed. The samples were processed in an elemental analyzer coupled with a mass spectrometer after the elimination of calcium carbonate. The obtained data were the grain-size, TOM, CaCO3, elemental (C, N) and the stable isotopic ratios of δ13C e δ15N of SOM. Based on the measured values of carbon and nitrogen, the C/N ratio, associated to δ13C e δ15N, is observed that in the PCS predominates an organic matter of marine origin along its entire length: C < 1%, N < 1%, C/N < 5, δ13C > -21 PDB e δ15N > 8Ar. The PCS presents patches of continental origin SOM, associated to the coastal zones adjacent to estuarine systems mouths and covering the paleochannels, which may indicate that this material was carried from the coastal rivers to the offshore areas, possibly by the paleo-valleys that also act as traps of fine sediments and SOM. The statistical analysis indicates the existence of 6 different sedimentary facies and a prevalence of one of them, characterized by poorly-sorted bioclastic sandy-gravel, with low to medium organic contents of marine origin. This indicates that the coastal sedimentary material contributions are low and the local cover is autochthonous of biogenic origin, and deposited according to the surficial topography, morphosedimentary processes and meteoceanographycal conditionings of the study area, typical of moderate hydrodynamic energy environments.

Relating Fish Hg to Variations in Sediment Hg, Climate and Atmospheric Deposition

This article addresses total fish Hg concentrations (THg) by variations in lake Sediment THg, atmospheric Hg deposition (atmHgdep), and climate, i.e., mean annual precipitation (ppt) and air temperature. The Fish THg data were taken from the 1967-to-2010 Fish Mercury Datalayer (FIMDAC). This compilation was standardized for 12-cm long Yellow Perch in accordance with the USGS National Descriptive Model for Mercury in Fish (NDMMF [1]), and documents Fish THg across 1936 non-contaminated lakes in Canada. About 40% of the standardized Fish THg variations related positively to increasing ppt and Sediment THg, but negatively to increasing mean annual July temperature (TJuly). Only 20% of the Fish THg variations related positively to atmHgdep alone. Increasing TJuly likely influences Fish Hg through increased lake and upslope Hg volatilization, in-fish growth dilution, and temperature-induced demethylization. FIMDAC Fish THg effectively did not change over time while atmHgdep decreased. Similarly, the above Fish Hg trends would likely not change much based on projecting the above observations into the future using current 2070 climate-change projections across Canada and the continental US. Regionally, the projected changes in Fish Hg would mostly increase with increasing ppt. Additional not-yet mapped increases are expected to occur in subarctic regions subject to increasing permafrost decline. Locally, Fish THg would continue to be affected by upwind and upslope pollution sources, and by lake-by-lake changes in water aeration and rates of lake-water inversions.

Comparison of Dissolved Air Flotation and Sedimentation in Treatment of Typical North China Source Water

The treatment of typical north China water by dissolved air flotation(DAF)and sedimentation process was examined.A pilot plant with a water treatment capacity of 120 m^3/d constructed in the Jieyuan Water Treatment Plant(JWTP) of Tianjin,China,was utilized for the comparison of the two processes.The results show that during the pilot test,DAF process can remove particles and organic mater more efficiently than sedimentation process.The removal rate for turbidity by DAF process is 5.5% higher than that by sedimentation in normal turbidity period,and 40% higher in low turbidity period,it is 5%～10% higher for removals of algae,total organic carbon(TOC),trihalomethane formation potential(THMFP)and bacteria in all periods.The removal rates for turbidity,TOC,THMFP,algae and bacteria by DAF process can reach 95%,30%, 20%,94% and 97% respectively.From the results of the pilot test,it can be concluded that DAF is a feasible clarification process,especially for source water with low turbidity and high algal blooming.

贵州草海沉水植物现状调查与影响因素分析

为了解当前贵州草海沉水植物退化现状和原因,研究采用网格布点法和设置样带法分别调查了草海的沉积物理化性质和沉水植物群落,评价草海目前沉水植物群落时空分布格局与沉积物营养盐特征,探究影响沉水植物的关键环境因子,同时通过草海种子库萌发实验评估草海沉水植物恢复的潜力。结果发现,草海现存包括轮藻(Charophyte sp.)、穗花狐尾藻(Myriophyllum spicatum)、篦齿眼子菜(Stuckenia pectinata)、大茨藻(Najas marina)、光叶眼子菜(Potamogeton lucens)、轮叶黑藻(Hydrilla verticillata)、穿叶眼子菜(Potamogeton perfoliatus)、金鱼藻(Ceratophyllum demersum)、微齿眼子菜(Potamogeton maackianus)和单果眼子菜(Potamogeton acutifolius)在内的共10种沉水植物。草海沉水植物生物量和覆盖度均表现出明显的时空差异。沉水植物总覆盖度与水体和沉积物营养盐呈显著负相关的结果表明,沉水植物在湖泊修复中具有削减营养盐的生态学功能,同时过高的营养盐可能对沉水植物的生长具有负面作用。当前草海沉积物营养盐的释放可能是影响沉水植物生长的主要因素。相较于其他湖泊草海沉积物具有疏松、含水率高等特点,对植物根系黏着力较低,导致沉水植物较难定植和生长。松散的沉积物很容易向水体中释放可溶性营养盐,引起藻类增殖及植物残体悬浮的遮光作用降低了水体透明度,从而影响沉水植物的光合作用。草海具有良好的沉水植物自然恢复潜力,但目前沉积物的高营养盐特征及其松散易悬浮的性质是制约沉水植物恢复的关键因素。研究能为草海后续开展水生态恢复方案提供基础资料和技术参考。

雅鲁藏布江上游干、支流沉积物总有机碳分布特征初探

为探究雅鲁藏布江(雅江)上游干、支流沉积物总有机碳(TOC)含量分布特征及其影响因素,研究了雅鲁藏布江上游干、支流沉积物TOC含量对粒度的响应,并基于随机森林分析(RFA)解释了流域内土地利用类型对沉积物TOC含量空间变化趋势的影响。结果表明,雅江上游沉积物TOC含量均值[(6.56±6.37)g·kg^(-1)]低于其他地区大中型河流[范围为5.95~49.06 g·kg^(-1),均值为(19.77±14.05)g·kg^(-1)]。其中,河源段沉积物TOC含量均值最低[(2.57±0.97)g·kg^(-1)],所有采样点沉积物TOC含量与黏土含量占比呈极显著正相关(r=0.64,P<0.01)。根据统计结果,包括雅江上游在内,河流沉积物TOC含量与粒径小于63μm颗粒含量具有极显著指数相关关系(r=0.77,P<0.01)。随机森林分析进一步表明,雅江上游沉积物TOC陆源贡献率中草地贡献率最大(48.12%),且受土地利用方式从以低覆盖度草地、裸土地为主导(上游头段)逐渐过渡到以中、高覆盖度草地和农、牧、一类工业用地(M1类)等为主(上游中、末段)的影响,沉积物TOC含量在空间上表现为随流向逐渐增加的趋势。总体上,人为干扰因素少及河流沉积物以砂质为主体是雅江上游沉积物TOC含量较低的重要原因。本研究深化了对雅鲁藏布江上游沉积物总有机碳含量分布特征及其影响因素的理解,可为进一步探究高原河流碳循环、生态环境保护以及区域可持续发展提供科学依据。

上游梯级水库建成运行对长江总磷输移影响分析及管控对策建议

长江上游梯级水库的建成运行改变了河流水沙条件,河流的天然水文节律被打乱,水沙磷由同步输送转变成非平衡性和不连续性输送,总磷的通量和赋存形态也发生改变。受水量水位调控、泥沙拦截淤积和水库滞热等影响,河流的径流、泥沙、温度等均发生改变,并产生系列生态环境效应。针对新情势下长江总磷问题,尤其是水利工程建设运行导致径流、泥沙、水温和磷的输送变异,从水沙空间格局及磷迁移转化特征等方面梳理长江流域的新情势,并分析了径流泥沙温度变化对磷输送的影响。结合总磷管控现状及存在的不足,建议加强河湖库中总磷标准的衔接,完善总磷环境标准体系,推动水质基准的研究,强化地方和流域标准的制定,并坚持将总磷排放浓度与总量双重控制相结合,最终为总磷问题的有效解决提供支撑。

Assessment of Sediment and Benthic Macrofauna Distribution at Dar es Salaam Harbour Channel

Sediment and macrobenthic fauna distribution at Dar es Salaam harbour channel were investigated to attest the influence of sediment grain size distribution and total organic carbon contents on benthic macrofauna dominance and diversity. Sampling campaign was conducted from January to April, 2019 in 25 sampling stations along the channel. Sediment grain sizes ranged between 0.7405 and 0.00273 mm with an average of 0.0804 mm classified as medium silt. Sediment distribution showed an onshore-offshore pattern consisting of fine dark clay-silt sediments in the southern part of the harbour close to Mwalimu Nyerere Bridge, medium (sandy) at the harbour and coarse sandy offshore. Five classes of macrofauna were identified with sedentary Polychaetes (Diopatra cuprea) found in tubes and free forms being dominant in most of the sediment types, however more abundant in clay-silt. High species diversity index values were encountered in sediments with medium total organic carbon (TOC) and sediment grain sizes (sand-silt). Apparently, low species similarity indices were observed in all sediment type indicating significant dissimilarities in species composition among sediment grain sizes. Thus, the distribution of benthic macrofauna species along Dar es Salaam harbour channel is strongly influenced by the sediment grain sizes and organic carbon contents in sediments.

响应面法优化经UHT处理全脂复原调制乳乳化稳定体系的研究

[目的]复原奶调制乳受奶粉产地、营养指标、使用比例、乳化稳定剂、工艺参数等影响,易出现灭菌生产工艺过程中保温管结垢过多,导致蒸汽压力骤升超出安全阈值、终产品沉淀过多等不稳定现象。[方法]本研究通过单因素试验初步探究复配乳化稳定剂、缓冲盐、奶粉品牌、奶粉复水温度和时长对产品稳定性、风味影响。在单因素试验基础上,设计响应面法Box-Behnken组合试验,优化复配乳化稳定剂应用比例、奶粉复水比例及温度。[结果]单因素试验结果显示,新西兰产地的某品牌全脂奶粉优于澳大利亚优于美国;奶粉复水比例1︰7.5且复水30 min条件下,45℃复水温度优于50℃,优于40℃;奶粉复水比例1︰7.5且复水1 h条件下,40℃复水温度优于45℃,优于50℃。(单,双甘油脂肪酸酯+三聚磷酸钠+FH)复配乳化稳定剂优于(单,双甘油脂肪酸酯+三聚磷酸钠+六偏磷酸钠+FH)复配乳化稳定剂,优于(单,双甘油脂肪酸酯+六偏磷酸钠+FH)复配乳化稳定剂,优于(单,双甘油脂肪酸酯+FH)复配乳化稳定剂。结合生产实际建立响应面模型最优解结果表明,全脂复原奶调制乳最佳乳化稳定体系及关键工艺参数:(单,双甘油脂肪酸酯+三聚磷酸钠+FH)复配乳化稳定剂添加比例0.26%,新西兰产地的某品牌全脂奶粉复水比例1︰7.2,奶粉复水温度45℃,复水时长30 min,预测感官评分9.273,TSI顶部和底部平均值0.171,离心沉淀率0.31%。3个模型的P值均<0.001,对应R2为0.948~0.981,说明3个响应方程吻合程度较高。在该条件下进行中试试验验证,对应复原奶调制乳的综合感官评分9.14,上机24 h的TSI顶部和底部平均值仅为0.182,3000 rpm、30 min条件下的离心沉淀率仅为0.35%,与预测值接近,证明模型有效。测得其粘壁率0.25%,均质指数5.70%,终产品pH值6.42,变化较小,接近于中性,证明产品稳定性较好。工业化生产条件下验证结果显示连续生产90吨过程中,试产优化后的配方及工艺参数对应中间段的压力上升幅度较(单,双甘油脂肪酸酯+FH)复配乳化稳定剂生产方案(原始配方)有明显改善,感官风味结果与实验室一致。[结论]响应面法可有效拟合该调制乳的复配稳定剂添加比例,奶粉复水比例、温度和时长关系,为工业化生产中奶粉过度热循环处理等特殊生产状况提供基础依据,有助于实际操作中快速准确响应相应的对策。

千岛湖沉积物中碳、氮、磷的分布特征及污染评价

通过测定千岛湖柱状沉积物中有机质(OM)、总氮(TN)和总磷(TP)含量,分析其污染分布特征,并评价污染水平。结果表明,千岛湖沉积物中OM、TN、TP平均值分别为1.44%、1.86 mg/g、0.89 mg/g。空间分布差异明显,城区库湾、新安江干流沿线污染相对较重;垂直分布,OM、TN、TP整体上均从湖底由下而上呈逐步上升变化过程。相关性分析表明,该湖沉积物中OM、TN、TP具有较高的同源性,氮、磷多以有机形式存在。C/N值表明,该湖沉积物中有机质主要来自内源的水生生物分解。评价结果显示,综合污染指数范围为1.1~4.2,该湖整体上处于重度污染水平,TP污染重于TN;有机指数范围为0.04~0.52,整体上属于轻度污染水平。