Predictions of Sediment Toxicity Using Consensus-Based Freshwater Sediment Quality Guidelines

The objectives of this study were to compare approaches for evaluating the combined effects of chemical mixtures on the toxicity in field-collected sediments and to evaluate the ability of consensus-based probable effect concentrations (PECs) to predict toxicity in a freshwater database on both a national and regional geographic basis. A database was developed from 92 published reports, which included a total of 1,657 samples with high-quality matching sediment toxicity and chemistry data from across North America. The database was comprised primarily of 10- to 14-day or 28- to 42-day toxicity tests with the amphipod Hyalella azteca (designated as the HA10 or HA28 tests) and 10- to 14-day toxicity tests with the midges Chironomus tentans or C. riparius (designated as the CS10 test). Mean PEC quotients were calculated to provide an overall measure of chemical contamination and to support an evaluation of the combined effects of multiple contaminants in sediments. There was an overall increase in the incidence of toxicity with an increase in the mean quotients in all three tests. A consistent increase in the toxicity in all three tests occurred at a mean quotient > 0.5, however, the overall incidence of toxicity was greater in the HA28 test compared to the short-term tests. The longer-term tests, in which survival and growth are measured, tend to be more sensitive than the shorter-term tests, with acute to chronic ratios on the order of six indicated for H. azteca. Different patterns were observed among the various procedures used to calculate mean quotients. For example, in the HA28 test, a relatively abrupt increase in toxicity was associated with elevated polychlorinated biphenyls (PCBs) alone or with elevated polycyclic aromatic hydrocarbons (PAHs) alone, compared to the pattern of a gradual increase in toxicity observed with quotients calculated using a combination of metals, PAHs, and PCBs. These analyses indicate that the different patterns in toxicity may be the result of unique chemical signals associated with individual contaminants in samples. Though mean quotients can be used to classify samples as toxic or nontoxic, individual quotients might be useful in helping identify substances that may be causing or substantially contributing to the observed toxicity. An increase in the incidence of toxicity was observed with increasing mean quotients within most of the regions, basins, and areas in North America for all three toxicity tests. The results of these analyses indicate that the consensus-based PECs can be used to reliably predict toxicity of sediments on both a regional and national basis.     

An Evaluation of Australian Sediment Quality Guidelines

Interim sediment quality guidelines (ISQGs) adapted recently to Australia from North American effects-based guidelines were evaluated with matching chemical and toxicological data collected for sediments (n = 103) from Sydney Harbour and south coast estuaries of New South Wales. The incidence of toxicity for the test battery was low (7%) among samples with all chemical concentrations below ISQG-Low values, indicating these guidelines are accurate and protective of non-toxic conditions. The incidence of toxicity increased greatly (to 73%) when one or more ISQG-Low values were exceeded, suggesting that ISQG-Low guidelines are appropriate for compliance. Frequent toxic effects (in >75% of samples) were associated with chemical concentrations exceeding ISQG-High guidelines. As expected, the high guideline values were more predictive of adverse effects than the low guidelines. Predictive abilities of ISQGs were not markedly affected by normalization of organic compounds to organic carbon or the use of dilute acid extractions for metals, suggesting that the guidelines are applicable to a wide range of conditions.     

Sediment Quality in Freshwater Impoundments at Savannah National Wildlife Refuge

Freshwater impoundments at Savannah National Wildlife Refuge (NWR), South Carolina, provide an important habitat for wildlife species, but degraded sediment quality in the Savannah River downstream of the discharge from two impoundments have caused concern about potential contaminant problems within the impoundments. The quality of sediments from five impoundments (impoundments no. 1, 2, 6, 7, and 17) on the NWR was evaluated using physical and chemical characterization, contaminant concentrations (metals, organochlorine pesticides, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons), and toxicity testing. Survival of Hyalella azteca (freshwater amphipod) exposed for 28 days to solid-phase sediments was not significantly different from controls, but growth was significantly decreased at several sites. Survival in 96-hour exposures to sediment pore water was significantly decreased at most sites. Factors contributing to the toxic responses were low pH (3.7 to 4.1), ammonia (20 mg/L), and increased concentrations of cations in the pore water. The excess of simultaneously extracted metals over the acid volatile sulfides in the sediments was also typical of sites displaying decreased sediment quality. Elemental concentrations in pore water were negatively correlated with pH, and the highest concentrations were observed in impoundment no. 7. The acidic nature of the sediment in this impoundment was exacerbated by recent draining, burning, and disking, which allowed oxidation of the previously anoxic wetland sediment. Sediment disturbance and mixing of vegetation into the sediments by disking may also have contributed to the formation of ammonia caused by microbial decomposition of the fragmented organic matter. Contaminants were not detected in sediments from the impoundments, but releases of acidic water with increased levels of sediment cations from the impoundments may have contributed to the degraded sediment conditions previously observed in the river. The practice of dewatering sediments for vegetation control may exacerbate the acidification of vulnerable sediments within impoundments of this NWR.     

Effects of Water Chemistry on the Bioavailability of Metals in Sediment toHyalella azteca: Implications for Sediment Quality Guidelines

Risk assessments of metals in sediments are often based on sediment-quality guidelines (SQGs) and do not take into account the chemistry of the overlying water. To determine the effects of water chemistry on the toxicity of metals in sediments, both water and sediment were collected from five metal-contaminated lakes with widely differing water chemistry near Canadian smelters. Metal bioaccumulation by Hyalella azteca was measured in laboratory exposures with each sediment and with overlying water from several different sources. The effect of water chemistry on Ni bioaccumulation from sediment was minimal. However, the effect was substantial for Cd because the effect of water chemistry on sediment-water partitioning was opposite to, and augmented, the effect of water chemistry on the Hyalella/water accumulation ratio. The effect of overlying water must be considered when conducting risk assessments for some metals in sediment (e.g., Cd). Examples are provided of equations that can be used to adjust cause-and-effect–based SQGs for water chemistry (e.g., using calcium concentrations or pH).     

Aquatic Risk Assessment of Herbicides in Freshwater Ecosystems of South Florida

Widespread, high-volume use and subsequent off-site transport of herbicides, specifically photosystem II inhibitors (PSII), on agricultural and noncultivated lands in south Florida has resulted in frequent detections in freshwater systems. In light of the current restoration efforts as part of the Comprehensive Environmental Restoration Plan (CERP), increased water flows containing detectable herbicide levels into the Everglades ecosystem and adjacent areas may have adverse consequences to the unique plant communities present in the region. The potential impact of individual herbicides to aquatic plant and algae species was examined using a probabilistic risk assessment approach. Risk was characterized for nine PSII herbicides (four triazines: ametryn, atrazine, simazine, and prometryn; two triazinones: hexazinone and metribuzin; two substituted ureas: diuron and linuron; and a uracil: bromacil) and a pyridazinone herbicide (norflurazon) by comparing the overlap of the 90th percentile surface water concentration (exposure benchmark) from the exposure distributions to the 10th percentile of effects (effects benchmark) determined from species sensitivity distributions of acute laboratory toxicity data. Overall, the risk of the individual herbicides was generally low. A Multiple Substance Potentially Affected Fraction (msPAF) risk approach also was utilized to examine the joint toxicity of the herbicide mixtures based on a concentration addition model. The risk associated with the herbicide mixture (mainly bromacil, diuron, and norflurazon) was determined to be high for Lee (site S79 on the Caloosahatchee River), Martin (site S80 on St. Lucie Canal), and St. Lucie (site S99 on C25 emptying into Indian River Lagoon) counties in south Florida. This study highlights the need to consider joint action of chemical mixtures as part of an ecological risk assessment.     

Development, Evaluation, and Application of Sediment Quality Targets for Assessing and Managing Contaminated Sediments in Tampa Bay, Florida

Tampa Bay is a large, urban estuary that is located in west central Florida. Although water quality conditions represent an important concern in this estuary, information from numerous sources indicates that sediment contamination also has the potential to adversely affect aquatic organisms, aquatic-dependent wildlife, and human health. As such, protecting relatively uncontaminated areas of the bay from contamination and reducing the amount of toxic chemicals in contaminated sediments have been identified as high-priority sediment management objectives for Tampa Bay. To address concerns related to sediment contamination in the bay, an ecosystem-based framework for assessing and managing sediment quality conditions was developed that included identification of sediment quality issues and concerns, development of ecosystem goals and objectives, selection of ecosystem health indicators, establishment of metrics and targets for key indicators, and incorporation of key indicators, metrics, and targets into watershed management plans and decision-making processes. This paper describes the process that was used to select and evaluate numerical sediment quality targets (SQTs) for assessing and managing contaminated sediments. These SQTs included measures of sediment chemistry, whole-sediment and pore-water toxicity, and benthic invertebrate community structure. In addition, the paper describes how the SQTs were used to develop site-specific concentration-response models that describe how the frequency of adverse biological effects changes with increasing concentrations of chemicals of potential concern. Finally, a key application of the SQTs for defining sediment management areas is discussed.     

水体沉积物毒性的评价方法

主要介绍了在水体沉积物毒性评价时常用的3种方法：生物毒性试验、毒性鉴别评价程序（TIE）和沉积物环境质量基准（SQGs）。生物毒性试验较化学分析方法考虑了污染物的生物可利用性,但是未能阐明产生毒性的具体污染物;TIE将常规的化学方法和生物毒性试验相结合,对产生毒性的具体污染物进行逐步鉴定,为制定相应的污染物浓度控制标准提供了依据;SQGs可以快速准确地对污染物的毒性作出判定,然而各种建立方法得到的基准间的差异影响了它的利用价值,需建立更为广泛、可靠的SQGs。将化学分析、毒性试验和现场生物调查结合是今后对沉积物中持久性有机污染物进行毒性评价和复合污染研究的发展方向。     

The Effects of Motorway Runoff on Freshwater Ecosystems: 3. Toxicant Confirmation

Previous studies have demonstrated that small streams receiving road runoff have reduced water and sediment quality. These changes in quality are associated with alterations in the structure and functioning of stream communities. Laboratory studies have indicated that the community changes are due to sediment-associated contaminants, and toxicant identification evaluations have shown that the major toxicants are contained probably in a fraction of sediment extract that contains polycyclic aromatic hydrocarbons (PAHs). The aim of the present study was to determine whether PAHs were indeed the major toxicants in sediment extracts. Toxicity tests were performed with PAH mixtures, the toxic fraction of an extract of runoff-contaminated sediment, and a whole sediment extract. These indicated that three PAHs accounted for the toxicity of a sediment extract: pyrene, fluoranthene, and phenanthrene. The possibility of spatial or temporal variation in major toxicants was also investigated and tests on a number of sediment extracts obtained from a number of sites at different times demonstrated that the three PAHs accounted for 30.8 to 120% of an extract's toxicity. When the PAHs were considered individually, pyrene was shown to account for most of the toxicity (44.9%), followed by fluoranthene (16%) and phenanthrene (3.5%). Received: 26 July 1996/Revised: 28 November 1996     

互联网医患功能沟通质量测量工具开发与评价

“互联网+医疗健康”发展迅速,但医患沟通质量不高,且缺乏针对性测量工具。以高血压为例,遵循Hinkin量表开发步骤,开发了互联网医患功能沟通质量测量工具,包括患者信息收集质量、诊断信息提供质量、治疗决策制定质量、疾病及治疗相关行为促进质量4个维度共计25个条目。实证评价验证了其科学性,可以对互联网医患功能沟通质量进行测量,有助于提高我国互联网医患功能沟通质量水平。     

Distribution, Fate, and Effects of 14C-DDT in Model Ecosystems Simulating Tropical Kenyan Freshwater Environments

No abstract available.     

住院科室医疗工作质量评价系统设计与研制

目的 建立医疗质量评价系统，为实施医疗质量控制，提高医疗服务与健康水平提供理论依据。方法 充分利用计算机技术，对医疗工作质量评价系统的设计原则、技术关键进行论证，将诊疗质量、工作强度、经济效益等医疗质量指标进行定量分析。结果 建立科学客观的评价管理系统。结论 该系统简单易行，可操作性强，结果较客观合理。     

Quality Evaluation and Quality Enhancement in Preschool: A Model of Competence Development

Can quality in preschool be enhanced through competence development simultaneously to organisational changes and financial cutbacks? The aim of this study is to develop a "Model of Competence Development” to enhance quality in preschool. The Model of Competence Development takes it's point of departure in evaluations of quality, as evaluated by the Early Childhood Environment Rating Scale¹ (ECERS), and evolved in interaction with the pedagogues throughout development work. The study is divided into three parts. 1. An external evaluation of quality of 20 preschool units using the ECERS. 2. A selection of an intervention group and a control group. The intervention group takes part in a competence development work, which starts and ends with self-evaluations of quality as evaluated by the ECERS. 3. An external evaluation of quality using the ECERS on the same preschool units.     

Quality Evaluation and Quality Enhancement in Preschool: A Model of Competence Development

There is an increasing demand from the public and the field to improve the quality of early childhood education in Hong Kong. The Hong Kong Education Commission has recently released an "education blueprint for the 21st century", which presents a set of reform proposals for the education system in Hong Kong. In the document, early childhood education has been acknowledged as the foundation for life-long learning. A key reform proposal is to build a new culture for quality early childhood education through upgrading professional competence and enhancing quality assurance mechanisms. The present paper provides a general background of existing practices in the preschool years, highlights issues that require attention in order to improve quality, and outlines the reforms introduced by the Education Commission. The implications of these reforms and the associated challenges are then discussed in the areas of quality assurance, curriculum, professional development, parental involvement and financial assistance for the early childhood education sector.