遂宁城乡集中式饮用水水源地钡分布特征及健康风险评价

为考察遂宁市辖区内集中式饮用水水源地污染物钡的分布特征和健康风险水平,通过电感耦合等离子体原子发射光谱法对研究区域内市级、县级和乡镇级所有在用的56个集中式饮用水水源地钡的浓度进行分析检测,借助空间分析与统计分析的结果,探讨了其空间分布和浓度差异,并利用环境健康风险评价模型,对不同类型水源地钡的健康风险进行了评价。结果表明,38个地表水水源地钡的浓度范围为0.065~0.180 mg/L,均值为0.110 mg/L;18个地下水水源地钡的浓度范围为0.027~0.370 mg/L,均值为0.130 mg/L。地表水与地下水水源地间钡的浓度差异具有统计学意义(P0.05),钡的空间分布也存在不同程度的差异性。各水源地中的钡经饮用和皮肤暴露两种途径对成人和儿童所引起的非致癌风险值为1.34×10~(-8)~1.62×10~(-8),远低于推荐的最大可接受风险水平(1.0×10~(-6)),各水源地因污染物钡导致的非致癌风险极低。     

Fecal source tracking by antibiotic resistance analysis on a watershed exhibiting low resistance

The ongoing development of microbial source tracking has made it possible to identify contamination sources with varying accuracy, depending on the method used. The purpose of this study was to test the efficiency of the antibiotic resistance analysis (ARA) method under low resistance by tracking the fecal sources at Turkey Creek, Oklahoma exhibiting this condition. The resistance patterns of 772 water-isolates, tested with nine antibiotics, were analyzed by discriminant analysis (DA) utilizing a five-source library containing 2250 isolates. The library passed various representativeness tests; however, two of the pulled-sample tests suggested insufficient sampling. The resubstitution test of the library individual sources showed significant isolate misclassification with an average rate of correct classification (ARCC) of 58%. These misclassifications were explained by low antibiotic resistance (Wilcoxon test P < 0.0001). Seasonal DA of stream E. coli isolates for the pooled sources human/livestock/deer indicated that in fall, the human source dominated (P < 0.0001) at a rate of 56%, and that human and livestock respective contributions in winter (35 and 39%), spring (43 and 40%), and summer (37 and 35%) were similar. Deer scored lower (17–28%) than human and livestock at every season. The DA was revised using results from a misclassification analysis to provide a perspective of the effect caused by low antibiotic resistance and a more realistic determination of the fecal source rates at Turkey Creek. The revision increased livestock rates by 13–14% (0.04 ≤ P ≤ 0.06), and decreased human and deer by 6–7%. Negative misclassification into livestock was significant (0.04 ≤ P ≤ 0.06). Low antibiotic resistance showed the greatest effect in this category.     

Receptor modeling for source apportionment of polycyclic aromatic hydrocarbons in urban atmosphere

This study reports source apportionment of polycyclic aromatic hydrocarbons (PAHs) in particulate depositions on vegetation foliages near highway in the urban environment of Lucknow city (India) using the principal components analysis/absolute principal components scores (PCA/APCS) receptor modeling approach. The multivariate method enables identification of major PAHs sources along with their quantitative contributions with respect to individual PAH. The PCA identified three major sources of PAHs viz. combustion, vehicular emissions, and diesel based activities. The PCA/APCS receptor modeling approach revealed that the combustion sources (natural gas, wood, coal/coke, biomass) contributed 19–97% of various PAHs, vehicular emissions 0–70%, diesel based sources 0–81% and other miscellaneous sources 0–20% of different PAHs. The contributions of major pyrolytic and petrogenic sources to the total PAHs were 56 and 42%, respectively. Further, the combustion related sources contribute major fraction of the carcinogenic PAHs in the study area. High correlation coefficient (R ² > 0.75 for most PAHs) between the measured and predicted concentrations of PAHs suggests for the applicability of the PCA/APCS receptor modeling approach for estimation of source contribution to the PAHs in particulates.     

Assessment of sediment quality in the Mediterranean Sea–Boughrara lagoon exchange areas (southeastern Tunisia): GIS approach-based chemometric methods

Concentrations of selected heavy metals (Cd, Pb, Zn, Cu, Mn, and Fe) in surface sediments from 66 sites in both northern and eastern Mediterranean Sea–Boughrara lagoon exchange areas (southeastern Tunisia) were studied in order to understand current metal contamination due to the urbanization and economic development of nearby several coastal regions of the Gulf of Gabès. Multiple approaches were applied for the sediment quality assessment. These approaches were based on GIS coupled with chemometric methods (enrichment factors, geoaccumulation index, principal component analysis, and cluster analysis). Enrichment factors and principal component analysis revealed two distinct groups of metals. The first group corresponded to Fe and Mn derived from natural sources, and the second group contained Cd, Pb, Zn, and Cu originated from man-made sources. For these latter metals, cluster analysis showed two distinct distributions in the selected areas. They were attributed to temporal and spatial variations of contaminant sources input. The geoaccumulation index (I _geo) values explained that only Cd, Pb, and Cu can be considered as moderate to extreme pollutants in the studied sediments.     

Tree-ring analysis for the assessment of anthropogenic changes and trends

Investigation of Pine (Pinus sylvestris L.)annual radial increment (width of annual tree rings) was carriedout in the surroundings of one of the largest pollution sources inLithuania – Jonava Nitrogen Fertilizers Plant. The main objectiveof investigation was to analyse different sides of anthropogenictransformations of tree-ring series in the polluted environment:changes in tree growth intensity; variance changes in tree-ringseries; changes in the relations with natural external factors.Three different periods of tree reaction to the environmentalpollution were singled out – fertilization period, depressionperiod and recovery period since annual emissions were essentiallyreduced. The variance of tree-ring series has increased severaltimes in the polluted environment. Reaction of trees to the impactof climatic factors (temperature, precipitation) has changedsignificantly in the polluted environment and their sensitivity hasalso increased.     

Parameter uncertainty and sensitivity in a liquid-effluent dose model

Radioactive materials which are released into streams on the Savannah River Site (SRS) eventually flow into the Savannah River. Tritium, ⁹⁰Sr, ¹³⁷Cs, and ²³⁹Pu account for the majority of the radiation dose received by users of the Savannah River. This paper focuses on the dose uncertainties originating from variability in parameters describing the transport and uptake of these nuclides. Parameter sensitivity has also been determined for each liquid pathway exposure model. The models used here to estimate radiation dose to an exposed individual provide a range of possible dose estimates that span approximately one order of magnitude. A pathway analysis reveals that aquatic food and water consumption account for more than 95% of the total dose to an individual.     

Exposure assessment of endocrine disruptors in bottled drinking water of Lebanon

Bisphenol A (BPA) is a commonly used monomer in various products including bottled water. Numerous studies have reported endocrine adverse effects and neoplasia associated with BPA exposure in animals. However, considerable discrepancies exist among these studies with respect to both the nature of the toxic effects and the threshold dose. In Lebanon, 19-L polycarbonate (PC) bottles of drinking water are widely used in urban areas. The present study aims at assessing BPA human exposure and associated health risks from drinking water in Lebanese. A total of 22 bottled water sources, packaged in PC, were identified from licensed and non-licensed sources. Water samples were analyzed following exposure to sunlight for 72 h. BPA in water was quantified by HPLC, and other potential organic pollutants were screened by GC/MS. Fifty-nine percent of samples showed BPA levels above detection limits (>0.05 ng/mL). The median BPA level was 0.1 ng/mL (range 0.05 to 1.37 ng/mL). The mean BPA level for the total number of samples was 0.169 ng/mL (±0.280). A higher mean BPA level was found in water from licensed companies compared to non-licensed sources, however, not statistically significant. Screening showed the presence of dibutyl-phthalate and dioctyl-phthalate in only two samples. Endocrine disruptors (EDR) are ubiquitous contaminants in bottled water in Lebanon with potential health risk implications. Although estimated exposure levels are below the reference dose (RfD), further studies are needed to quantitate exposure from various sources and to investigate EDR contribution to existing epidemics in the country.     

中国北方山区水库与引黄水库富营养化特征

于2012年10月—2013年8月对中国北方地区2种典型水库:山区水库(卧虎山、锦绣川)和引黄水库(鹊山、玉清)进行了采样调查,对其水质特征和富营养化现状进行分析研究。结果表明:2类水库水质的最大差异在于山区水库的氮含量显著高于引黄水库,这主要与水源、氮素来源和水库的进水方式有关。山区水库中SD与藻类生物量、TP关系密切;而引黄水库中,影响SD的环境因素较复杂,除藻类生物量和氮、磷外,碱度和水温也与SD密切相关。全年水平上,卧虎山水库营养状态指数显著高于其他水库,属中-富营养水体,锦绣川水库、鹊山水库和玉清水库均属中营养水平。时间上,同类型水库的营养状态指数季节变化基本一致。参与营养状态计算的4个因子中,Chla和TN对营养状态指数的贡献最大,表明这两者是引起2类水库营养状态加重的重要原因。典型的水源及进水方式、流域人类活动类型和强度是影响山区水库和引黄水库营养状态的主要外部因素。     

Sensitivity analysis of water quality for Delhi stretch of the River Yamuna,India

Simulation models are used to aid the decision makers about water pollution control and management in river systems. However, uncertainty of model parameters affects the model predictions and hence the pollution control decision. Therefore, it often is necessary to identify the model parameters that significantly affect the model output uncertainty prior to or as a supplement to model application to water pollution control and planning problems. In this study, sensitivity analysis, as a tool for uncertainty analysis was carried out to assess the sensitivity of water quality to (a) model parameters (b) pollution abatement measures such as wastewater treatment, waste discharge and flow augmentation from upstream reservoir. In addition, sensitivity analysis for the “best practical solution” was carried out to help the decision makers in choosing an appropriate option. The Delhi stretch of the river Yamuna was considered as a case study. The QUAL2E model is used for water quality simulation. The results obtained indicate that parameters K ₁ (deoxygenation constant) and K ₃ (settling oxygen demand), which is the rate of biochemical decomposition of organic matter and rate of BOD removal by settling, respectively, are the most sensitive parameters for the considered river stretch. Different combinations of variations in K ₁ and K ₂ also revealed similar results for better understanding of inter-dependability of K ₁ and K ₂. Also, among the pollution abatement methods, the change (perturbation) in wastewater treatment level at primary, secondary, tertiary, and advanced has the greatest effect on the uncertainty of the simulated dissolved oxygen and biochemical oxygen demand concentrations.     

Using Multiple Antibiotic Resistance and land use characteristics to determine sources of fecal coliform bacterial pollution

Multiple Antibiotic Resistance (MAR) analysis and regression modeling techniques were used to identify surface water areas impacted by fecal pollution from human sources, and to determine the effects of land use on fecal pollution in Murrells Inlet, a small, urbanized, high-salinity estuary located between Myrtle Beach and Georgetown, South Carolina. MAR analysis was performed to identify areas in the estuary that are impacted by human-source fecal pollution. Additionally, regression analysis was performed to determine if an association exists between land use and fecal coliform densities over the ten-year period from 1989 to 1998. Land-use variables were derived using Geographic Information System (GIS) techniques and were used in the regression analysis.MAR analyses were conducted by comparing the frequency and patterns of antibiotic resistance found in Escherichia coli isolates derived from surface water samples and from sewage sources in the Murrells Inlet sewage collection system. The MAR results suggest that the majority of the fecal pollution detected in the Murrells Inlet estuary may be from non-human sources, including fecal coliforms isolated from areas in close proximity to high densities of active septic tanks.A MAR Index, which measures the frequency of antibiotic resistance, was calculated for each of twenty-three water samples and nine sewage samples. The antibiotic resistance pattern comparisons were performed using cluster analysis. Although the MAR indices indicated that several surface water sites had potential human-source contamination, the cluster analysis suggests that only one sampling site had MAR patterns that were similar to those found in the sewage samples. This site was in close proximity to several large pleasure boats as well as a sewage collection system lift station, but was not near areas with active septic tanks. The results of the regression analysis also suggest that sewage sources and rainfall runoff from urbanized areas may contribute to fecal pollution in the estuary.     

Genotoxicity at Low Level Dose of Inspirable Urban Ambient Air Particulate in a Semiarid Regime

Samples of inspirable air particulate(inhalable + ingestable) were obtained at two urbanlocations in southern Argentina which differ in theirexposure to pollution by class B2 polynuclear aromatichydrocarbons (PAHs). Sample extracts were tested in vitro for induction of chromosomal aberrations incultured rat hepatocytes. The average induced amountof chromosomal aberrations did not vary amonggeographic locations, but significant differences wereidentified in samples near known emitting sources. Thedifferences were analyzed in the frame of a model ofthe emissions and their subsequent distribution andre-suspension from the soil and other surfaces. Theresults show that the rat hepatocyte test is sensitiveto genotoxic activity of the urban air particulate inthe low dose range of the tested fractions. Adequatemodels of human exposure to these materials shouldconsider emissions and re-suspension of pollutants bywind. The implications of these results on theformulation of policies of emission reduction, urbansoil management and the design of cancer epidemiologystudies are discussed.     

Chemometric application in identifying sources of organic contaminants in Langat river basin

Increasing urbanization and changes in land use in Langat river basin lead to adverse impacts on the environment compartment. One of the major challenges is in identifying sources of organic contaminants. This study presented the application of selected chemometric techniques: cluster analysis (CA), discriminant analysis (DA), and principal component analysis (PCA) to classify the pollution sources in Langat river basin based on the analysis of water and sediment samples collected from 24 stations, monitored for 14 organic contaminants from polycyclic aromatic hydrocarbons (PAHs), sterols, and pesticides groups. The CA and DA enabled to group 24 monitoring sites into three groups of pollution source (industry and urban socioeconomic, agricultural activity, and urban/domestic sewage) with five major discriminating variables: naphthalene, pyrene, benzo[a]pyrene, coprostanol, and cholesterol. PCA analysis, applied to water data sets, resulted in four latent factors explaining 79.0% of the total variance while sediment samples gave five latent factors with 77.6% explained variance. The varifactors (VFs) obtained from PCA indicated that sterols (coprostanol, cholesterol, stigmasterol, β-sitosterol, and stigmastanol) are strongly correlated to domestic and urban sewage, PAHs (naphthalene, acenaphthene, pyrene, benzo[a]anthracene, and benzo[a]pyrene) from industrial and urban activities and chlorpyrifos correlated to samples nearby agricultural sites. The results demonstrated that chemometric techniques can be used for rapid assessment of water and sediment contaminations.     

嘉善前体物与气象因子对臭氧生成的影响及臭氧潜在源区分析

利用2017年嘉善善西超级站臭氧（O₃）及其前体物（NO_x和VOCs）以及气象因子（温度、湿度、风速）逐小时数据，分析了2017年全年NO_x和O₃的变化特征以及春季（4—5月）、夏季（7—8月）NO_x和气象因子对O₃生成的影响，利用O₃生成潜势（OFP）评估了VOCs大气化学反应活性，并通过潜在源区贡献（PSCF）和浓度权重轨迹（CWT）方法分析了嘉善春、夏季O₃潜在源区贡献特征。研究发现：O₃日变化特征为单峰结构，NO_x为弱双峰结构。O₃浓度在3—9月较高，春、夏季O₃浓度峰值分别出现在15：00和14：00，春、夏季的NO_x、O₃日变化与2017年全年日变化趋势基本一致。NO_x对O₃存在滴定作用，且低湿高温有利于O₃浓度的升高。春、夏季O₃生成潜势贡献均表现为烯烃 > 芳香烃 > 烷烃，由于烯烃光化学活性较高，夏季烯烃浓度升高导致其贡献较春季增长约18.1个百分点，且夏季VOCs平均最大O₃增量反应活性高于春季。PSCF和CWT分析结果表明，嘉善春季的潜在源区主要为本地、西南方向和东南方向，夏季的潜在源区主要为本地、西北方向、西南方向以及东南方向。     

Statistical methods to apportion the sources of particles in the industrial region of Estarreja—Portugal

Factor analysis models are very attractive for source apportionment and have been widely applied. They do not require a priori knowledge of the number and composition of the sources, and they can actually uncover previously unsuspected sources and estimate the composition of the sources using only ambient monitoring data.Aerosol particles were collected from an industrial atmosphere and analyses for water soluble and carbon components. Principal components analysis permitted the evaluation of the contribution due to industries, soil fraction, secondary pollutants and sea spray particles of the total suspended aerosol mass.It can be concluded that the atmospheric aerosol in the Industrial Area of Estarreja (Portugal) contains a relative important fraction that is water soluble. Ammonium sulphates and nitrates are the main components of this fraction. Carbon compounds constitute about 30% of the total aerosol mass. These compounds are mainly formed by organic matter emitted by the industries. Due to the mutagenic and carcinogenic characteristics of some organic compounds processed in the Industrial Area (vinyl chloride, benzene, aniline, etc.), the concern exists of negative human health effects as a result of prolonged inhalation. Soil compounds is another important fraction of the aerosol mass, mainly in summer with dry, sunny and windy weather conditions.A more conclusive idea of the sources and effects of aerosol matter can only be obtained with the specific analysis of organic compounds and the determination of trace elements, characteristic of each particular source.     

Variations in sensitivity of two populations of Corophium Orientale (Crustacea: Amphipoda) towards cadmium and sodium laurylsulphate

The aim of this work was to monitor the sensitivity of two populations of Corophium orientale (Crustacea: Amphipoda) living at the outfall of two rivers (Magra and Serchio), comparing their responses towards two different toxicant solutions. Sensitivity was monthly checked performing the 96h-LC₅₀ static water only test with Cd(NO₃)₂ and SDS. If no significant differences were found between the two populations, they could have been employed without distinction to perform sediment toxicity bioassays. As regard to Cd, an increasing in LC₅₀ values from summer to winter was evident in each population (Serchio River: August 2003  =  1,36 mg/l, February 2004  =  7,23 mg/l; Magra River: August  =  1,21 mg/l, April  =  5,01 mg/l). This pattern was correlated to the droop of temperatures in winter period. The responses of the two populations towards the cadmium were compared using the ANOVA. The analysis showed any significant differences between the populations (p  =  0.12). The pattern of sensitivity towards SDS for the population living on Magra River was similar to the same pattern found for Cd; as regard to the population living on Serchio River, data were not enough to describe the annual pattern. Anyway, statistical analysis was performed and no significant differences were found between the two populations (p  =  0.34).     

Chemical Compositions and Sources of Organic Matter in Fine Particles of Soils and Sands from the Vicinity of Kuwait City

Fine particles in the atmosphere from soil and sand resuspension contain a variety of organic compounds from natural biogenic and anthropogenic matter. Soil and sand samples from various sites near Kuwait city were collected, sieved to retain the fine particles, and extracted with a mixture of dichloromethane and methanol. The extracts were derivatized and analyzed by gas chromatography-mass spectrometry in order to characterize the chemical compositions and sources of the organic components. The major inputs of organic compounds were from both natural biogenic and anthropogenic sources in these samples. Vegetation was the major natural source of organic compounds and included n-alkanols, n-alkanoic acids, n-alkanes, sterols and triterpenoids. Saccharides had high concentrations (31–43%) in the sand dune and seafront samples, indicating sources from decomposed vegation materials and/or the presence of viable microbiota such as bacteria and fungi. Vehicular emission products, leakage of lubricating oils, discarded plastics and emissions from cooking operations were the major anthropogenic inputs in the samples from the urban areas. This input was mainly UCM, n-alkanes, hopanes, plasticizers and cholesterol, respectively.     

渭河陕西段表层沉积物重金属污染特征及潜在风险

为了解渭河陕西段表层沉积物重金属的污染特征，采用ICP-MS分析了13个采样断面表层沉积物中As、Cd、Cr、Cu、Mn、Ni、Pb和Zn 8种重金属的含量，并对其来源和生态风险进行了评价。结果表明：渭河陕西段8种重金属的平均含量顺序依次为Mn > Zn > Cr > Cu > Ni > Pb > As > Cd；除Ni外的其余7种重金属的平均含量均超过陕西省A层土壤背景值。各断面表层沉积物重金属的潜在生态风险指数（RI）介于111.4~7 043.7，其中23.1%的断面有极强生态风险，46.2%的断面为中等生态风险，其余为轻微生态风险。Cd污染最为严重，对各断面的潜在生态风险介于较强生态风险与极强生态风险之间，对RI的贡献平均为85.2%；其余7种重金属在所有断面均属于轻微生态危害。渭河陕西段表层沉积物As、Cd、Cu和Zn主要为工业与农业来源；Cr和Ni主要为自然来源；Pb和Mn与城市污水和交通污染来源有关。     

Spatial based compromise programming for multiple criteria decision making in land use planning

Today, competing land use is continuing to occur in many developed regions. In the Agricultural Development Zone of Western Sydney Region, which is characterised by complex landscape patterns, land use competition is widespread. From a land use planning perspective, identification of suitable locations for a given type of land use is necessary for decision makers to formulate land use alternatives in different locations, based on existing land potential and constraints. For such a region, use of a simple method that implements a categorical system and considers only inherent land characteristics in the analysis is often inadequate to arrive at an optimal spatial decision. The primary aim of this paper is to develop spatial modelling procedures for agricultural land suitability analysis using compromise programming (CoPr) and fuzzy set approach within a geographical information systems (GIS) environment. Five main sets of spatial data for use as decision criteria were developed by using fuzzy set methodology: a land suitability index (LSI) for maximising the land productivity objective; an erosion tolerance index (ETI) for minimising the erosion risk objective; a runoff curve number (CN) for maximising the water discharge regulation objective; an accessibility (RP) measure for maximising the land accessibility objective; and the proximity to water body (WP) for minimising the water pollution objective. An L _p -metric was used in the analysis utilising different strategies with representative indices ranging from a situation where full tradeoff among criteria occurs to a noncompensatory condition. Different weighting combinations were also applied, and decision analysis was carried out by using values ranging from 0 to 1.0, where 1.0 is considered as an ideal point. The CoPr model demonstrated in this paper yielded a promising result, as several different techniques of sensitivity analysis show reasonably good results. Likewise, an overlay of that result with the present land use/land cover indicates a good corresponding spatial matching between existing land use (orchard and cultivated land), and the cells (land parcels) classified as the best in CoPr. The results are amenable to various map display techniques, either using continuous values or by defining different cut off points in the data space within a raster GIS environment.     

Assessment of the impact of petroleum and petrochemical industries to the surrounding areas in Malaysia using mosses as bioindicator supported by multivariate analysis

Biomonitoring of multi-element atmospheric deposition using terrestrial moss is a well-established technique in Europe. Although the technique is widely known, there were very limited records of using this technique to study atmospheric air pollution in Malaysia. In this present study, the deposition of 11 trace metals surrounding the main petroleum refinery plant in Kerteh Terengganu (eastern part of peninsular Malaysia) has been evaluated using two local moss species, namely Hypnum plumaeforme and Taxithelium instratum as bioindicators. The study was also done by means of observing whether these metals are attributed to work related to oil exploration in this area. The moss samples have been collected at 30 sampling stations in the vicinity of the petrochemical industrial area covering up to 15 km to the south, north, and west in radius. The contents of heavy metal in moss samples were analyzed by energy dispersive x-ray fluorescence technique. Distribution of heavy metal content in all mosses is portrayed using Surfer software. Areas of the highest level of contaminations are highlighted. The results obtained using the principal components analysis revealed that the elements can be grouped into three different components that indirectly reflected three different sources namely anthropogenic factor, vegetation factor, and natural sources (soil dust or substrate) factor. Heavy metals deposited mostly in the distance after 9 km onward to the western part (the average direction of wind blow). V, Cr, Cu, and Hg are believed to have originated from local petrochemical-based industries operated around petroleum industrial area.     

A terrain-based paired-site sampling design to assess biodiversity losses from eastern hemlock decline

Biodiversity surveys are often hampered by the inability tocontrol extraneous sources of variability introduced intocomparisons of populations across a heterogenous landscape. If not specifically accounted for a priori, this noisecan weaken comparisons between sites, and can make itdifficult to draw inferences about specific ecologicalprocesses. We developed a terrain-based, paired-sitesampling design to analyze differences in aquaticbiodiversity between streams draining eastern hemlock (Tsuga canadensis) forests, and those draining mixedhardwood forests in Delaware Water Gap National RecreationArea (USA). The goal of this design was to minimize variancedue to terrain influences on stream communities, whilerepresenting the range of hemlock dominated streamenvironments present in the park. We used geographicinformation systems (GIS) and cluster analysis to define andpartition hemlock dominated streams into terrain types basedon topographic variables and stream order. We computedsimilarity of forest stands within terrain types and usedthis information to pair hemlock-dominated streams withhardwood counterparts prior to sampling. We evaluated theeffectiveness of the design through power analysis and foundthat power to detect differences in aquatic invertebratetaxa richness was highest when sites were paired and terraintype was included as a factor in the analysis. Precision ofthe estimated difference in mean richness was nearly doubledusing the terrain-based, paired site design in comparison toother evaluated designs. Use of this method allowed us tosample stream communities representative of park-wide forestconditions while effectively controlling for landscapevariability.