重量法测定水中悬浮物和全盐量的不确定度评定

依据不确定度评定准则,采用一种新的方法,即忽略量取样品体积的不确定分量,只考虑样品前后两次恒重的不确定分量,对重量法测定水中悬浮物和全盐量的不确定度来源进行了识别、分析和量化,确定了不确定度分量,据此计算出合成标准不确定度。重量法测定水中悬浮物和全盐量的不确定度评定的方法适用于实验室内部不确定度的评定。     

检测时间和保存方式对饮用水源水中粪大肠菌群测定的影响

研究了检测时间、保存方式和分析方法对饮用水源水中粪大肠菌群检测结果的影响。通过在不同季节采集样品,采取常温保存、冷藏保存、不同的检测时间间隔和不同的检测方法 4种处理方式,对粪大肠菌群检测结果进行差异性分析。结果表明：在冬季,检测时间和保存方式对粪大肠菌群检测结果的影响不明显,不具有统计学意义（P>0.05）;在夏季,检测时间和保存方式对粪大肠菌群检测结果影响极显著（P<0.001）,其差异性在取样0.5 h后即显现出来。无论是在冬季,还是在夏季,不同检测方法之间的差异都无统计学意义（P>0.05）。     

精密度法评定水中镉的测量不确定度

根据分析人员在连续6周每周4次水质中镉实验室质控样品的分析数据,利用Top-down技术中的精密度法,对环境水样中镉的测量不确定度进行了评定,建立了用实验室内精密度和偏差的数据来评定水中镉的测量不确定度的方法。文章依据GB/T 7475-1987《水质铜、锌、铅、镉的测定原子吸收分光光度法》测定水中镉的质控样品,利用能力验证结果和质控样品的重复性、精密度实验,对实验室测量偏倚和精密度控制情况进行评估,并在保证实验室的测量过程处于统计受控状态下,参考能力验证的室间标准差作为测量不确定度的估计值。     

基于Top-down精密度法评定水质钒测定的不确定度

文章基于实验室内标准样品测试数据和实验室间能力验证分析数据,以Top-down技术评定电感耦合等离子体质谱测定水中钒含量的测量不确定度,建立了利用实验室质控数据评定测量不确定度的方法。通过实验室内标准物质重复测定结果计算实验室内期间标准差和重复性标准差,通过能力验证结果计算检测过程偏倚,并计算不确定度。该评定方法系统、完整地评价了检测结果的可靠性与分散程度。结果表明Topdown法相较于Bottom-up法避免了复杂的分量计算和模型建立过程,操作更为简便,具有较好的应用前景。     

氢化物发生-原子荧光光谱法测定环境空气中汞的结果不确定度评定

对氢化物发生-原予荧光光谱法测定环境空气中汞含量不确定度进行了评定.由测定过程的数学模型分析了产生不确定度因素.通过不确定度评定得出不确定度主要来源于样品的制备过程.其中消解过程带来的不确定度最大.     

水质的生化需氧量(BOD5)稀释与接种法测定结果不确定度评定

在实际工作中，运用测量过程的合并样本标准差来评定A类不确定度比较客观。本文根据JJF1059—1999《测量不确定度评定与表示》，通过实例，阐述了用稀释接种法测定水中生化需氧量不确定度的评定方法。     

水中砷的原子荧光光谱测定结果的不确定度评定

目的 对原子荧光光谱法测定水中砷含量的不确定度来源及其对测量不确定度的影响进行分析。方法 利用相对标准不确定度进行测量不确定度的评定。过程采用直观的因果图，建立有效的数学模型，利用相对标准不确定度分量进行测量不确定度评定，并在砷含量为1．7μg/L的水样测定中，获得其相对标准不确定度为3．4％，有效自由度为25。结论 原子荧光光谱法对水中砷浓度测量不确定度影响因素中，工作曲线拟合产生的不确定度较大。     

环境空气颗粒物中重金属的不确定度评定

使用滤膜采集环境空气颗粒物,样品经过消解后用ICP-MS测定。以锌、镉、铅为例,对可能引入的不确定度分量,包括样品采集体积、样品消解、定容体积、标准溶液配制、标准曲线拟合、重复测定等进行分析和评定,得出扩展不确定度。通过不确定度的分析,样品消解和曲线拟合是质量控制的关键,并提出提高不确定度引入分量的质量控制措施,为类似的不确定度评定提供参考依据。     

连续流动分析法测定水中总氮的不确定度评定

在实验室分析基础上,对连续流动分析法测定水中总氮过程的不确定度进行评定。本文建立了数学模型,对不确定度来源进行了分析,并计算了不确定度分量、合成不确定度及扩展不确定度,最后给出了总氮测量结果的标准表示方法。     

钼酸铵分光光度法测定水中总磷的不确定度评定

本文按照GB11893-89中测量步骤制备工作曲线,根据实际测量过程建立数学模型,分析钼酸铵分光光度法测定水中总磷不确定度的来源,并对各不确定度分量进行详细评定和量化分析,得出本法测定总磷不确定度的来源并讨论降低不确定度的方法措施,以提高测量的准确性,为实验室不确定度评定提供参考依据。     

ENHANCING FECAL COLIFORM TOTAL MAXIMUM DAILY LOAD MODELS THROUGH BACTERIAL SOURCE TRACKING1

ABSTRACT: Surface water impairment by fecal coliform bacteria is a water quality issue of national scope and importance. In Virginia, more than 400 stream and river segments are on the Commonwealth's 2002 303(d) list because of fecal coliform impairment. Total maximum daily loads (TMDLs) will be developed for most of these listed streams and rivers. Information regarding the major fecal coliform sources that impair surface water quality would enhance the development of effective watershed models and improve TMDLs. Bacterial source tracking (BST) is a recently developed technology for identifying the sources of fecal coliform bacteria and it may be helpful in generating improved TMDLs. Bacterial source tracking was performed, watershed models were developed, and TMDLs were prepared for three streams (Accotink Creek, Christians Creek, and Blacks Run) on Virginia's 303(d) list of impaired waters. Quality assurance of the BST work suggests that these data adequately describe the bacteria sources that are impairing these streams. Initial comparison of simulated bacterial sources with the observed BST data indicated that the fecal coliform sources were represented inaccurately in the initial model simulation. Revised model simulations (based on BST data) appeared to provide a better representation of the sources of fecal coliform bacteria in these three streams. The coupled approach of incorporating BST data into the fecal coliform transport model appears to reduce model uncertainty and should result in an improved TMDL.     

PREDICTING FECAL COLIFORM BACTERIA LEVELS IN THE CHARLES RIVER,MASSACHUSETTS, USA1

In Massachusetts, the Charles River Watershed Association conducts a regular water quality monitoring and public notification program in the Charles River Basin during the recreational season to inform users of the river's health. This program has relied on laboratory analyses of river samples for fecal coliform bacteria levels, however, results are not available until at least 24 hours after sampling. To avoid the need for laboratory analyses, ordinary least squares (OLS) and logistic regression models were developed to predict fecal coliform bacteria concentrations and the probabilities of exceeding the Massachusetts secondary contact recreation standard for bacteria based on meteorological conditions and streamflow. The OLS models resulted in adjusted R²s ranging from 50 to 60 percent. An uncertainty analysis reveals that of the total variability of fecal coliform bacteria concentrations, 45 percent is explained by the OLS regression model, 15 percent is explained by both measurement and space sampling error, and 40 percent is explained by time sampling error. Higher accuracy in future bacteria forecasting models would likely result from reductions in laboratory measurement errors and improved sampling designs.     

Fecal coliform loadings and stocks in buttermilk bay,Massachusetts, USA,and management implications

Abundance of fecal caliform bacteria is a weak index of the presence of human pathogens in wastewater entering coastal waters. In spite of this, use of fecal caliform indices for management purposes is widespread. To gain insight into interpretation of fecal coliform data, we evaluated size of stocks of fecal coliforms in water, sediments, and sea wrack, in Buttermilk Bay, a coastal embayment in Massachusetts. Sediments contained most of the fecal coliforms. Fecal coliforms in sediments were as much as one order of magnitude more abundant than in the water column or in sea wrack. The fecal coliforms in sediments of Buttermilk Bay were so abundant that resuspension of fecal coliforms from just the top 2 cm of muddy sediments could add sufficient cells to the water column to have the whole bay exceed the federal limit of fecal coliforms for shellfishing. The major sources of fecal coliforms to the bay were water-fowls, surface runoff, groundwater, and streams. Waterfowl were the largest source of fecal coliforms during cold months; surface runoff, streams, and groundwater were most important during warm months. Redirection of surface runoff pipes is unlikely to be a very successful management action since contributions via this source are insufficient to account for the measured increases in concentrations of fecal coliforms in water. Removal of waterfowl is also unlikely to be useful, since fecal coliform concentrations leading to closures of shellfish beds and swimming areas are most frequent during warm months when waterfowl are rarest. Rates of loss of fecal caliform cells from the water column by death and tidal exchange were high. Mortality of cells was about an order of magnitude larger than losses by tidal exchange. The amounts of fecal coliforms brought into the bay by waterfowl, surface runoff, groundwater, and streams are an order of magnitude smaller than the losses by mortality and tidal removal. This implies that there is an additional source of fecal coliforms within the bay. We suggest that resuspension of the upper layers of sediments can easily account for the fecal coliforms present in the water. Fecal coliform content of water and shellfish were not correlated. In contrast, sediment and shellfish fecal coliform abundances were significantly related. Monitoring of fecal coliforms in sediments may provide a better assessment of shellfish than sampling of water. The large fecal coliform stock in sediments should be the first priority for management. Efforts ought to be directed toward the reduction of sediment fecal coliform stocks. Lowering nutrient additions to coastal water bodies may be one practical approach.     

FECAL COLIFORM RELEASE FROM CATTLE FECAL DEPOSITS1

ABSTRACT: Cowpies molded to a standard configuration and size were subjected to simulated rainfall, and the fecal coliform counts were determined using the most probable number (MPN) method of enumeration. The standard cowpie deposits were exposed to simulated rainfall once at ages 2 through 100 days. The effects of rainfall intensity and recurrent rainfall were also tested. Naturally-occurring fecal deposits were also tested to compare their results with those from the standard cowpies. A log-log regression was found to describe the decline in peak fecal coliform release with fecal deposit age. The 100-day-old fecal deposits produced peak counts of 4,200 fecal coliform per 100 milliliters of water. This quantity of release is minimal compared to the release from fresher fecal material. Rainfall intensity had little effect on peak fecal coliform release from fecal deposits that were 2 or 10 days old. At age 20 days the effect of rainfall intensity was significant; the highest intensity gave the lowest peak counts, and the lowest intensity gave the highest peak counts. The effect of rainfall intensity appears to be related to the dryness of the fecal deposits. Peak fecal coliform counts were significantly lowered when the fecal deposits were rained on more than once. This decline was thought to be produced by the loss of bacteria from the fecal deposits during the previous wettings. Standard cowpies produced a peak release regression that was not significantly different from the regression for the natural fecal deposits. Apparently, grossly manipulating the fecal deposits did not significantly change the release patterns.     

Bacterial water quality: Springs and streams in the Great Smoky Mountains National Park

Water samples from streams and springs in the Great Smoky Mountains National Park were analyzed for fecal coliform, fecal streptococcus, and total coliform bacteria. Levels of bacteria were found to be highly variable but related to elevation, time of year, type of water source, and water level of the streams. Visitors did not seem to be major contributors to bacterial contamination. Levels of fecal coliform and total coliform in most water samples were unsuitable for drinking without treatment. Tennessee state standards for body contact recreation (swimming and wading) were exceeded in a few samples but none from streams suitable for swimming. As a result of these findings, park managers increased efforts to inform visitors of the need to treat drinking water and removed improvements at backcountry springs which tended to give the springs the image of safe, maintained water sources.     

AN ANALYSIS OF COLIFORM BACTERIA IN THE UPPER ILLINOIS WATERWAY1

ABSTRACT: During the summer of 1971 about 150 water samples were examined for total and fecal coliform bacteria in the Upper Illinois Waterway at 19 river stations. The data per station were found to be normal geometric distributed. Bacteria densities changed with sampling dates and generally decreased with water movement downstream. Several sewage treatment effluents made marked pulses along the bacterial die-off curves. The observed fecal coliform results were evaluated in terms of the Illinois Pollution Control Board's standards. The FC:TC ratio on the waterway for each station were presented. Using Chick's Law, coliforms death rates were estimated. Efforts to correlate observed total and fecal densities with temperature, flow, algal densities, dissolved oxygen, and 5-day biochemical oxygen demand were not successful. (KEY TERMS: algae; biochemical oxygen demand; coliform bacteria; dissolved oxygen; flow; stream survey; temperature; water pollution; water quality standards)     

MODELING FECAL COLIFORM CONTAMINATION IN THE RIO GRANDE1

This study examines sources of fecal coliform in Segment 2302 of the Rio Grande, located south of the International Falcon Reservoir in southern Texas. The watershed is unique because the contributing drainage areas lie in Texas and Mexico. Additionally, the watershed is mostly rural, with populated communities known as “colonias.” The colonias lack sewered systems and discharge sanitary water directly to the ground surface, thus posing an increased health hazard from coliform bacteria. Monitoring data confirm that Segment 2302 is not safe for contact recreation due to elevated fecal coliform levels. The goal of the study was to simulate the observed exceedences in Segment 2302 and evaluate potential strategies for their elimination. Fecal coliform contributions from ranching and colonia discharges were modeled using the Hydrologic Simulation Program‐Fortran (HSPF). Model results indicated that the regulatory 30‐day geometric mean fecal coliform concentration of 200 colony forming units (cfu) per 100 milliliters is exceeded approximately three times per year for a total of 30 days. Ongoing initiatives to improve wastewater facilities will reduce this to approximately once per year for 14 days. Best management practices will be necessary to reduce cattle access to streams and eliminate all exceedences. The developed model was limited by the relatively sparse flow and fecal coliform data.     

Studies on the effect of Bladex and Etazine on bacterial indices of pollution

The effect of the triazine herbicides Etazine and Bladex on coliform and fecal streptococci groups was studied in Nile river water, Nile water seeded with sewage, and autoclaved Nile water. The results indicate the fecal streptococci were able to persist and multiply in Nile water containing Bladex or Etazine and seeded with sewage. The successive addition of Bladex and Etazine (up to 10 mg/liter) increased its degradation rate and had no inhibitory effect on the bacterial parameters.     

AGRICULTURAL LAND USE IMPACTS ON BACTERIAL WATER QUALITY IN A KARST GROUNDWATER AQUIFER1

ABSTRACT: The impact on water quality by agricultural activity in karst terrain is an important consideration for resource management within the Appalachian Region. Karst areas comprise about 18 percent of the Region's land area. An estimated one-third of the Region's farms, cattle, and agricultural market value are on karst terrain. The purpose of this study was to compare fecal bacteria densities in karst groundwater impacted by two primary agricultural land uses in central Appalachia. Fecal bacteria densities were measured in cave streams draining two primary land management areas. The first area was pasture serving a beef cow-calf operation. The second area was a dairy. Neither area had best management practices in place for controlling animal wastes. Median fecal coliform and fecal streptococcus densities were highest in cave streams draining the dairy. Median fecal coliform densities in the dairy-impacted stream were greater than 4,000 CFU/100 ml and the median fecal coliform densities in the pasture-impacted streams were less than 10 CFU/100 ml. Median fecal streptococcus densities in the same streams were greater than 2,000 CFU/100 ml and 32 CFU/100 nil, respectively. A second dairy, with best management practices for control of animal and milkhouse waste, did not appear to be contributing significant amounts of fecal bacteria to the karst aquifer. It was concluded that agriculture was affecting bacterial densities in the karst aquifer. New management practices specifically designed to protect karst groundwater resources may be one way to protect the groundwater resource.     

A GEOGRAPHIC INFORMATION SYSTEM TO PREDICT NON-POINT SOURCE POLLUTION POTENTIAL1

ABSTRACT: Bacterial densities (total coliform, fecal coliform, and fecal streptococci) and suspended solids in runoff from a feedlot, pasture, and corn field were measured. Densities of fecal coliform were highest from the feedlot but were 1000 to 10,000 times greater than the water quality standard for swimmable waters from all three land uses. Densities of fecal streptococci were highest from the corn field, which suggests that wildlife are the source of bacteria. Fecal coliform/fecal streptococci ratios distinguished cattle from wildlife as the source of bacterial pollution both among land uses and among seasons of the year. Suspended solids concentrations in runoff ranged from 423 to 925 mg/l and were highest from the corn field. A Geographic Information System (GIS), which utilizes a raster or grid-cell format, was developed to include algorithms associated with non-point source pollution. The system accepts digitally mapped information on soil type, topography, and land use. It calculates characteristics such as slope and slope length, and relates these characteristics to soils and land use parameters in order to produce three dimensional maps of runoff potential, sediment pollution potential, and bacterial pollution potential. It offers the advantages of retaining the geographic character of pollution potential information and of conveying in three-dimensional graphical terms the effects of topography, soil type, land use, and land management practices.