Effect of Precipitation Variability on Pollutant Concentrations in Soil: Implications for Exposure and Risk Assessments

Concentrations of toxic pollutants in surface soils must be predicted in order to assess exposures and risks that may arise from emissions at incinerators and other air pollution sources. At present, concentrations are predicted using deterministic models and time-averaged values of input parameters. This steady-state equilibrium approach does not address variability in the underlying transport and fate processes. This paper explores the variability of pollutant concentrations in surface soils that arises from precipitation, an intermittent process that governs wet deposition and leaching processes. Using long-term (45 to 50 years) historical records at 6 climato-logically diverse sites, concentrations predicted using the steady-state approach are compared to those predicted using a dynamic numerical model that simulates dry and wet deposition, leaching, and pollutant accumulation in the surface layer of soil using a daily time step. The models are compared for pollutants of low, medium, and high water solubility. Both models show that predictions depend strongly on the pollutant solubility and the precipitation pattern at the location. Average concentrations differed between locations by a factor of up to 4 due to precipitation patterns; the solubility of the pollutant had a much more pronounced effect. Both models produced similar long-term trends, for example, the duration of the period needed to achieve a quasi-steady-state pollutant concentration. However, for soluble pollutants, the dynamic model produced maximum 24-hr average concentrations that exceeded long-term averages by 4 to 8 times, and long-term predictions of the dynamic model exceeded predictions of the steady-state model by 1.9 to 3.6 times (depending on the site). These differences are caused by the steady-state assumption that deposition and leaching occur continuously. While the steady-state model can be used to estimate long-term trends of moderately to highly insoluble pollutants, the dynamic model should be used to predict short-term, maximum concentrations and both short- and long-term averages of soluble pollutants. Site-specific exposure and risk assessments should consider temporal variation and the use of a dynamic model if concentrations of soluble pollutants approach risk-based target levels.     

An Extreme Value Analysis of Pollutant Concentrations in Surface Soils Due to Atmospheric Deposition

Risk assessments often rely on deterministic models using long-term averages or “steady-state” values of input variables. Such models do not provide the information needed to estimate acute exposures. This study uses extreme value theory to examine the frequency and magnitude of daily pollutant concentrations in surface soils predicted at six U.S. locations. Concentrations are predicted using a deposition-leaching model and 50 years of historical precipitation data. A stochastic model also is used to generate 1000 years of precipitation data as modeling inputs for each location. The annual maximum concentrations at each site are fitted to a Gumbel type I distribution to estimate occurrence probability. For soluble pollutants, the predicted concentration varied substantially with precipitation, and the maximum daily concentrations exceeded annual averages by 4 to 8 times. Observed and synthetic precipitation data produced similar results at most study locations, though the synthetic data provided a slightly better fit to the Gumbel type I distribution. The precipitation model allows the generation of representative precipitation data that extend limited historical records. The extreme value analysis facilitates the evaluation of maximum pollutant concentrations, return periods, and other statistics that are important in evaluating acute exposures.     

Simulated predictions of insect phenological events made by using mean and median functional lower developmental thresholds

A computer-simulated study was conducted to determine whether mean or median functional lower developmental thresholds and required degree-days were superior for predicting the dates on which insect phenological events occurred. In addition, these simulations allowed us to determine if the type of year (weatherwise) influenced those predictions. Results indicated that when median functional lower developmental thresholds and required degree-days were used their predictions were closer to the dates on which the phenological events occurred than were predictions that were made using mean thresholds and required degree-days. Also, the predictions of phenological events made when using median functional lower developmental thresholds and required degree-days were not strongly influenced by the type of year. However, the influence of type of year was quite strong when predictions were made when using mean thresholds and required degree-days. The variability in predictions that were made when using median functional lower developmental thresholds and required degree-days was greater than the variability in predictions that were made when using mean thresholds and required degree days. However, the increased variability was caused by many predictions being closer to, rather than farther from, the actual dates on which the phenological events occurred. Based on these findings, we suggest that median functional lower developmental thresholds, along with median required degree-days, be considered for use when predicting insect phenological events in the field.     

A measurement error model for time-series studies of air pollution and mortality

One barrier to interpreting the observational evidence concerning the adverse health effects of air pollution for public policy purposes is the measurement error inherent in estimates of exposure based on ambient pollutant monitors. Exposure assessment studies have shown that data from monitors at central sites may not adequately represent personal exposure. Thus, the exposure error resulting from using centrally measured data as a surrogate for personal exposure can potentially lead to a bias in estimates of the health effects of air pollution. This paper develops a multi-stage Poisson regression model for evaluating the effects of exposure measurement error on estimates of effects of particulate air pollution on mortality in time-series studies. To implement the model, we have used five validation data sets on personal exposure to PM10. Our goal is to combine data on the associations between ambient concentrations of particulate matter and mortality for a specific location, with the validation data on the association between ambient and personal concentrations of particulate matter at the locations where data have been collected. We use these data in a model to estimate the relative risk of mortality associated with estimated personal-exposure concentrations and make a comparison with the risk of mortality estimated with measurements of ambient concentration alone. We apply this method to data comprising daily mortality counts, ambient concentrations of PM10measured at a central site, and temperature for Baltimore, Maryland from 1987 to 1994. We have selected our home city of Baltimore to illustrate the method; the measurement error correction model is general and can be applied to other appropriate locations.Our approach uses a combination of: (1) a generalized additive model with log link and Poisson error for the mortality-personal-exposure association; (2) a multi-stage linear model to estimate the variability across the five validation data sets in the personal-ambient-exposure association; (3) data augmentation methods to address the uncertainty resulting from the missing personal exposure time series in Baltimore. In the Poisson regression model, we account for smooth seasonal and annual trends in mortality using smoothing splines. Taking into account the heterogeneity across locations in the personal-ambient-exposure relationship, we quantify the degree to which the exposure measurement error biases the results toward the null hypothesis of no effect, and estimate the loss of precision in the estimated health effects due to indirectly estimating personal exposures from ambient measurements.     

The effect of lead on fitness components and developmental stability in Drosophila subobscura

We analyzed the developmental time, egg-to-adult viability, and developmental stability (fluctuating wing size asymmetry) in Drosophila subobscura, maintained for six generations on different concentrations of lead. Development time is significantly affected by generation and lead concentration, but interaction of these factors is not a significant source of variability for this fitness component. Generation and the interaction generation x concentration of lead significantly affect egg-to-adult viability. Levene's test of heterogeneity of variance showed that variability of FA is not significant in any of the samples. Within both lead concentrations females showed significantly higher FA indices for the wing width than males. Within sexes, a significantly higher FA was found only in females for wing width FA between the control and the lower concentration of lead. The results show that if strong relationship between FA and the studied fitness components exists, it results in a stronger selection of unstable genotypes under lead as a stress factor and, consequently, FA needs to be used with caution as a biomarker in natural populations under environmental stress.     

Habitat preferences of the Syrian Woodpecker Dendrocopos syriacus in urban environments: an ambiguous effect of pollution

Capsule The occurrence of the Syrian Woodpecker Dendrocopos syriacus in an urbanized habitat is determined by the number of trees and pollutant emissions. Air pollution may weaken trees and increase the number of insects inhabiting them.

Aims To determine the habitat preferences of the Syrian Woodpecker in the highly urbanized environment of the city of Kraków.

Methods A set of 13 habitat and environmental parameters of 50 breeding territories and 50 random points were evaluated. A logistic regression was used to determine the probability of species occurrence, and Akaike's information criterion was used for model selection.

Results The number of trees, coverage of woody vegetation, total vegetation cover and level of pollutant emissions were significantly higher in Syrian Woodpecker breeding territories than in the random points. The model best explaining the probability of species occurrence consisted of four parameters: the number of trees, coverage of the total built-up area, total vegetation cover and pollutant emissions. The parameters best explaining a high probability of species occurrence were high number of trees and high pollutant emissions.

Conclusion Air pollution may weaken trees and potentially increase the number of insects inhabiting them, an important component of the Syrian Woodpecker's diet. However, the negative impact of air pollution on birds may impact on their condition. Urban habitats could, therefore, act as an ecological trap for this species.     

Association between Air Pollution and Suicide in South Korea: A Nationwide Study

Suggestive associations of suicide with air pollutant concentrations have been reported. Recognizing regional and temporal variability of pollutant concentrations and of suicide, we undertook a detailed meta-analysis of completed suicides in relation to 5 major pollutants over 6 years in the 16 administrative regions of the Republic of Korea, while also controlling for other established influences on suicide rates. Of the 5 major pollutants examined, ozone concentrations had a powerful association with suicide rate, extending back to 4 weeks. Over the range of 2 standard deviations (SD) around the annual mean ozone concentration, the adjusted suicide rate increased by an estimated 7.8% of the annual mean rate. Particulate matter pollution also had a significant effect, strongest with a 4-week lag, equivalent to 3.6% of the annual mean rate over the same 2 SD range that approximated the half of annual observed range. These results strongly suggest deleterious effects of ozone and particulate matter pollution on the major public health problem of suicide.     

Epiphytic lichens as biomonitors of airborne heavy metal pollution

The research aims to assess the performance of the lichen Parmotrema reticulatum as an air pollution biomonitor of four heavy metals, namely, chromium (Cr), copper (Cu), lead (Pb) and zinc (Zn). Four contrasting land use sites within the greater Auckland region of New Zealand are used. One site is located within the relatively clean air shed of conservation land, the others within residential, commercial, and industrial areas, characterised by increasingly polluted air sheds, respectively. Three groups of lichens are monitored over a two-year period using active and passive biomonitoring methods to assess ‘on-thallus’ and ‘in-thallus’ concentrations of heavy metals. Seasonal transplants are used to quantify heavy metals accumulated by the lichen during each season. Long-term transplants are used to measure how fast lichens accumulate heavy metals and to better understand how and when heavy metals within the lichen thallus achieve equilibrium with air pollutant concentrations over time. The results show that the lichens continuously accumulates pollutants from the air until equilibrium is reached, thus transplanted lichens are useful for monitoring air pollution concentrations over time. Since pollutant concentration in the transplanted lichen at equilibrium stabilises, at this point the lichen ceases to be useful for monitoring temporal trends in air pollution, but may useful for spatial air pollution monitoring. The industrial location has the highest total accumulation for all four heavy metals, followed by the commercial and residential locations, respectively. Overall, the results show that the lichen P. reticulatum may be successfully used to monitor spatial and temporal pollution patterns caused by even very low concentrations of Cr, Cu, Pb and Zn.     

Managing microcystin: identifying national‐scale thresholds for total nitrogen and chlorophyll a

相似文献   

Ozone in Spain's national parks and protected forests

In general, it is difficult to measure air pollutant concentrations in remote areas, as they are mostly national parks and protected areas. Passive samplers provide an accurate and inexpensive method for measuring cumulative exposures of different air pollutants. They have been used to collect ozone data in both laboratory and field at different geographical scales. The objective of the present study is to fill the knowledge gap regarding air quality in remote areas of Spain, such as national parks and protected areas. Because there were no systematic data sets on the main air pollutants that could affect these areas, an air quality measurement network was established between 2001 and 2004 on 19 locations inside Spanish national parks and protected areas. The data collected suggest that ozone levels in mountainous areas are high enough to affect sensitive vegetation. Most of the locations registered moderate-to-high ozone levels, with important interannual variability. Altitudinal ozone gradients were observed in most of the parks with complex topography due to the establishment of local circulations that incorporate polluted air masses from polluted airsheds or even long-range transport (i.e., Canary Islands). Different latitude-dependent, yearly cycles were also observed, showing two, one, or no clear peaks depending on the region. These findings extend to the most southerly locations, except in the Canary Islands, where pollution transported from other regions in the upper transport layers probably led to the high concentrations observed.     

Spatial Modeling of Air Pollution in Studies of Its Short‐Term Health Effects

Summary In studies that estimate the short‐term effects of air pollution on health, daily measurements of pollution concentrations are often available from a number of monitoring locations within the study area. However, the health data are typically only available in the form of daily counts for the entire area, meaning that a corresponding single daily measure of pollution is required. The standard approach is to average the observed measurements at the monitoring locations, and use this in a log‐linear health model. However, as the pollution surface is spatially variable this simple summary is unlikely to be an accurate estimate of the average pollution concentration across the region, which may lead to bias in the resulting health effects. In this article, we propose an alternative approach that jointly models the pollution concentrations and their relationship with the health data using a Bayesian spatio‐temporal model. We compare this approach with the simple spatial average using a simulation study, by investigating the impact of spatial variation, monitor placement, and measurement error in the pollution data. An epidemiological study from Greater London is then presented, which estimates the relationship between respiratory mortality and four different pollutants.     

Viscosity of semiflexible chitosan solutions: influence of concentration, temperature, and role of intermolecular interactions

The influence of polymer concentration and temperature on the rheological behavior of chitosan solution was studied. The threshold concentrations for the different viscometric regimes were determined and the different power laws exponents were calculated and compared with those predicted from models. Different observations and the high values of these exponents within the high concentration region lead to consideration of the presence of intermolecular interactions as soon as the polymer concentration is larger than the overlap concentration. The activation energy was determined as a function of the polymer concentration, and its evolution was compared with theoretical predictions. A gel-sol transition was demonstrated at high concentrations.     

大气污染对大鼠呼吸道微生态的影响研究

探讨了大气污染引起呼吸道症状和机体健康效应的作用机理,为防治大气污染及其对机体的损害提供理论依据。采用模拟现实大气污染的方法,分高、中、低浓度用Wistar大鼠制备大气污染动物模型,对大鼠口咽部菌群进行定性、定量、定位检测,动态研究。大气污染大鼠模型口咽部微生态发生改变。与污染前比,肺炎克雷伯杆菌等致病菌检出率明显增加(P<0.05),厌氧菌含量明显减少(P<0.05),并且随着染毒时间厌氧菌和细菌总量都呈明显下降趋势(P<0.05);口咽部菌群含量在一定范围内波动,没有随着染毒浓度改变而呈明显改变。大气污染对呼吸道正常菌群有毒害作用,对微环境有破坏作用,导致微环境改变,正常菌群含量减少,致病菌定植,是呼吸道疾病发病率升高的重要因素之一。     

The contribution of intra‐ and interspecific tolerance variability to biodiversity changes along toxicity gradients

The worldwide distribution of toxicants is an important yet understudied driver of biodiversity, and the mechanisms relating toxicity to diversity have not been adequately explored. Here, we present a community model integrating demography, dispersal and toxicant‐induced effects on reproduction driven by intraspecific and interspecific variability in toxicity tolerance. We compare model predictions to 458 species abundance distributions (SADs) observed along concentration gradients of toxicants to show that the best predictions occur when intraspecific variability is five and ten times higher than interspecific variability. At high concentrations, lower settings of intraspecific variability resulted in predictions of community extinction that were not supported by the observed SADs. Subtle but significant species losses at low concentrations were predicted only when intraspecific variability dominated over interspecific variability. Our results propose intraspecific variability as a key driver for biodiversity sustenance in ecosystems challenged by environmental change.     

Intermittent exposure to aquatic pollutants: assessment,toxicity and sublethal responses in fish and invertebrates

Aquatic animals are often exposed to intermittent, variable poison concentrations during pollution incidents. However, current understanding of ecotoxicology has evolved primarily from continuous exposure studies. This review summarises the relatively dispersed toxicity literature on intermittent exposures. Methodologies used in existing continuous exposure toxicity tests may be adapted to intermittent regimes provided the exposure profile is known and “poison concentration” is defined to give toxicologically relevant lethality estimate. Such tests rely on assuming that continuous and intermittent exposures of equivalent dose have the same toxicity. This assumption is untrue for some chemicals. The toxicity of intermittent events may be assessed by correlating mortality with poison accumulation, biochemical, haematological or physiological response syndromes. Such bioassays can be performed without knowledge of the exposure profile, and are often sufficiently rapid to record short pollution events. Intermittent and continuous exposures of equivalent dose may not have the same toxicities. Intermittent exposures are less toxic than continuous events, but only when peak concentrations of pollutant are the same in each regime. Exceptionally, sulphuric acid, acid/Al and ammonia are much more toxic to fish when administered intermittently. Variations in intermittent exposure frequency or duration do not produce proportional changes in lethality, since apparently large changes in exposure dose may not significantly alter toxicity. The short-lived nature of intermittent exposures suggests that equilibriums in poison concentrations between the external environment and the body compartments of the test species are not achieved. The overall accumulation response depends particularly on the duration of peak concentrations and any “recovery periods” between multiple episodes relative to poison uptake and depuration rates respectively. Transient biochemical and physiological disturbances occur during intermittent exposures. Latent effects include reduced post-exposure growth and reproductive failure in the F₁ generation, or increased deformities in the F₂ generation of fish.     

Determination of COD,BOD, and suspended solids loads during combined sewer overflow (CSO) events in some combined catchments in Spain

The main topic of the research project presented here in part is the determination of pollutant loads during combined sewer overflow events in several experimental catchments in Spain that were determined to obtain a pollution pattern which may be applied to other catchments in Spain or an order of magnitude of pollution loads in Spanish catchments. The existence or non-existence of a first-flush is also examined. Five catchments were monitored in five Spanish cities, and both hydraulic parameters and pollutant amounts were measured in dry conditions and during rainfall events. From the data obtained, some parameters were extracted for each catchment and an order of magnitude of the pollution amounts was proposed for Spanish catchments, in terms of event mean concentration (EMC) and maximum concentrations, since the moderate differences between catchments permit an estimation of a mean value.     

Natural and man-made selection for air pollution resistance

All manner of domestic and industrial activities lead to the injection of potentially toxic contaminants in to the air. Most have little or no discernible impact on the environment, because the resulting concentrations in the atmosphere fall well below the threshold for effects. Others attain levels that are known to exceed the recognized thresholds for damage to both fauna and flora. In this review the focus is on two of the most ubiquitous air pollutants-sulphur dioxide (SO2) and ozone (O3). In many industrialized regions, ground-level concentrations of these gases are know to be high enough to depress crop yields and cause subtle shifts in the composition of natural (and semi-natural) plant communities. Consequently, these pollutants constitute a novel evolutionary challenge for natural and managed ecosystems. Herein, evidence is presented that some species are capable of responding to this challenge by evolving the ability to grow and reproduce in areas subjected to potentially phytotoxic pollutant concentrations. The prospects for breeding plants with enhanced resistance to the most common air pollutants are discussed and the tangible prospects of incorporating modern molecular approaches into existing strategies for the identification, isolation and manipulation of air pollution resistance in new stock are highlighted.     

珠海竹银水库入库污染现状评估及水环境容量分析

以珠海竹银水库为对象,针对水库面临的入库污染问题,分析入库主要的污染物类型与污染负荷总量,全面评估水库的污染现状,并对水库水环境容量状况进行评价.研究结果表明,入库河流的主要问题是氮、磷浓度较高,但其它污染物的浓度不高.每种污染物的水环境容量值都很大,其中氯化物的容量最大,重金属的容量较小,表明水库蓄水初期水质较好,纳污能力较强.这些结果为今后竹银水库的污染控制与水质管理,为实现安全供水目标提供基础数据.     

Deriving nutrient targets to prevent excessive cyanobacterial densities in U.S. lakes and reservoirs

相似文献