Estimation of the Probability of Exceedance of Contaminant Concentrations

McBean, Edward A.; Rovers, Frank A.

doi:10.1111/j.1745-6592.1992.tb00416.x

Cited by 19 publications

(11 citation statements)

References 1 publication

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“…The likelihood of occurrence of these concentrations is unknown if they are not placed in a probabilistic framework that takes into account their variability. Recently, procedures have been proposed that take this variation into account by providing distributions of environmental concentrations rather than single values [4,[39][40][41][42].…”

Section: Probabilistic Risk Assessmentmentioning

confidence: 99%

“…These data sets were analyzed in three ways. For some data sets with relatively few values, and for data sets for which sample time information was not available, distributions of measured data were plotted on the assumption that the N data points represented a universe of N ϩ 1 measurements, and 90th percentile concentrations were obtained by regression [42], as recommended in the ARAMDG report [4]. For data sets that were clearly not log-normally distributed or were products of seasonal sampling, 90th percentiles were estimated nonparametrically from the time-weighted data.…”

Section: Analysis Of Exposure Datamentioning

confidence: 99%

“…Where multiple data points were available for a single species, the smallest value was used for regression analysis of the cumulative frequency distribution. Data were plotted using a log-Pearson type III distribution [42] using SigmaPlot [76], which also gave regression coefficients and the equations for the regression lines ( Table 28).…”

Section: Analysis Of Toxicity Datamentioning

confidence: 99%

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Ecological Risk Assessment of Atrazine in North American Surface Waters

Solomon¹,

Baker²,

Richards³

et al. 1996

Environ Toxicol Chem

296

446

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Abstract-The triazine herbicide atrazine (2-chloro-4-ethylamino-6-isopropyl-amino-s-triazine) is one of the most used pesticides in North America. Atrazine is principally used for control of certain annual broadleaf and grass weeds, primarily in corn but also in sorghum, sugarcane, and, to a lesser extent, other crops and landscaping. Atrazine is found in many surface and ground waters in North America, and aquatic ecological effects are a possible concern for the regulatory and regulated communities. To address these concerns an expert panel (the Panel) was convened to conduct a comprehensive aquatic ecological risk assessment. This assessment was based on several newly suggested procedures and included exposure and hazard subcomponents as well as the overall risk assessment. The Panel determined that use of probabilistic risk assessment techniques was appropriate. Here, the results of this assessment are presented as a case study for these techniques. The environmental exposure assessment concentrated on monitoring data from Midwestern watersheds, the area of greatest atrazine use in North America. This analysis revealed that atrazine concentrations rarely exceed 20 g/L in rivers and streams that were the main focus of the aquatic ecological risk assessment. Following storm runoff, biota in lower-order streams may be exposed to pulses of atrazine greater than 20 g/L, but these exposures are short-lived. The assessment also considered exposures in lakes and reservoirs. The principal data set was developed by the U.S. Geological Survey, which monitored residues in 76 Midwestern reservoirs in 11 states in 1992-1993. Residue concentrations in some reservoirs were similar to those in streams but persisted longer. Atrazine residues were widespread in reservoirs (92% occurrence), and the 90th percentile of this exposure distribution for early June to July was about 5 g/L. Mathematical simulation models of chemical fate were used to generalize the exposure analysis to other sites and to assess the potential effects of reduction in the application rates. Models were evaluated, modified, and calibrated against available monitoring data to validate that these models could predict atrazine runoff. PRZM-2 overpredicted atrazine concentrations by about an order of magnitude, whereas GLEAMS underpredicted by a factor of 2 to 5. Thus, exposure models were not used to extrapolate to other regions of atrazine use in this assessment. The effects assessment considered both freshwater and saltwater toxicity test results. Phytoplankton were the most sensitive organisms, followed, in decreasing order of sensitivity, by macrophytes, benthic invertebrates, zooplankton, and fish. Atrazine inhibits photophosphorylation but typically does not result in lethality or permanent cell damage in the short term. This characteristic of atrazine required a different model than typically used for understanding the potential impact in aquatic systems, where lethality or nonreversible effects are usually assumed. In addition, recovery of phytoplankto...

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Section: Probabilistic Risk Assessmentmentioning

confidence: 99%

Section: Analysis Of Exposure Datamentioning

confidence: 99%

Section: Analysis Of Toxicity Datamentioning

confidence: 99%

See 1 more Smart Citation

Ecological Risk Assessment of Atrazine in North American Surface Waters

Solomon¹,

Baker²,

Richards³

et al. 1996

Environ Toxicol Chem

296

446

View full text Add to dashboard Cite

show abstract

“…Although a much longer data record is desired for exceedance probability calculations, agro-meteorological stations with continuous, used in other water monitoring and management applications such as streamflow analysis [25], groundwater contamination analysis [26], precipitation analysis [27], and in other areas of water and risk management. In this study, five probability levels were selected for analysis: 25%, 50%, 60%, 75%, and 85%.…”

Section: Methodsmentioning

confidence: 99%

Exceedance Probability of the Standardized Precipitation-Evapotranspiration Index in the Texas High Plains

Moorhead¹,

Marek²,

Gowda³

et al. 2017

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Drought is a common occurrence in many arid and semi-arid regions that can have large negative impacts on water resources and agricultural production. Since agricultural drought is affected by both water supply and demand (precipitation and evapotranspiration), it is beneficial to include both in agricultural drought monitoring. The Standardized Precipitation-Evapotranspiration Index (SPEI) was found to be a suitable drought index for monitoring agricultural drought. In this study, the SPEI calculated from agro-meteorological weather stations was used to determine exceedance probabilities at five levels in the Texas High Plains. In addition, the kriging method was used to interpolate between the stations to generate spatial maps for the exceedance probabilities. No significant differences were found between stations, indicating any station should be suitable to represent the Texas High Plains. Results showed drought conditions occurred at all five probability levels during the summer growing season for this region. Although differences were not significantly different, the interpolated maps showed a trend where minor differences in the SPEI values were associated with the West-East precipitation gradient. However, there was no trend associated with the North-South air temperature gradient. A risk analysis showed that the SPEI probability values can provide policy and decision makers with additional information for better water management in the Texas High Plains.

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“…The use of normal and lognormal cumulative probability graphs to identify population outliers in groundwater data was modeled on a similar technique commonly used in the mineral exploration industry (Sinclair 1976) and.more recently adopted to assist in the determination of remediation standards for contaminated soils (EPA 1994;Fleischhauer and Korte 1990) and groundwater (McBean and Rovers 1992). In addition to the Y-12 Plant, Lockheed Martin Energy Systems sites in the process of completing studies by using this method are the Paducah (Kentucky) Gaseous Diffusion Plant; the Portsmouth (Ohio) Gaseous Diffusion Plant; and the Oak Site.…”

Section: Step 3: Additional Data Screening and Probability Graphingmentioning

confidence: 99%

Determination of reference concentrations for inorganic analytes in groundwater at the Oak Ridge Y-12 Plant, Oak Ridge, Tennessee

1996

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Estimation of the Probability of Exceedance of Contaminant Concentrations

Cited by 19 publications

References 1 publication

Ecological Risk Assessment of Atrazine in North American Surface Waters

Ecological Risk Assessment of Atrazine in North American Surface Waters

Exceedance Probability of the Standardized Precipitation-Evapotranspiration Index in the Texas High Plains

Determination of reference concentrations for inorganic analytes in groundwater at the Oak Ridge Y-12 Plant, Oak Ridge, Tennessee

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