摘要:

ABSTRACT:Lake water sulfate values were examined for two areas in western Norway and the western United States presently receiving low levels of sulfate in atmospheric deposition. Data from these areas were used to estimate background concentrations of sulfate in lakes found in areas currently receiving acidic deposition. The two areas contain dilute lakes with concentrations of sea‐salt corrected Ca+ Mg less than 50 μeq/l or conductivity4.8. Based on observations from these areas, we conclude that background sulfate concentrations were probably no more than 10 to 15 μeq L‐1for areas of Norway and the U.S. containing lakes with low concentrations of base cations. For southern Norway and the northeastern U.S., present lakewater sulfate concentrations represent an increase of 7 to 10 fold above these estimated backgro

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb03059.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:Water samples for dissolved mercury require special treatment because of the high chemical mobility and volatility of this element. Widespread use of mercury and its compounds has provided many avenues for contamination of water. Two laboratory tests were done to determine the relative permeabilities of glass and plastic sample bottles to mercury vapor. Plastic containers were confirmed to be quite permeable to airborne mercury, glass containers were virtually impermeable. Methods of preservation include the use of various combinations of acids, oxidants, and complexing agents. The combination of nitric acid and potassium dichromate successfully preserved mercury in a large variety of concentrations and dissolved forms. Because this acid‐oxidant preservative acts as a sink for airborne mercury and plastic containers are permeable to mercury vapor, glass bottles are preferred for sample collection. To maintain a healthy work environment and minimize the potential for contamination of water samples, mercury and its compounds are isolated from the atmosphere while in storage. Concurrently, a program to monitor environmental levels of mercury vapor in areas of potential contamination is needed to define the extent of mercury contamination and to assess the effectiveness of mercury clean‐up procedu

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb03060.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:A new method has been developed for estimating future reservoir storage capacities, allowing for sediment deposition and compaction. Reservoir sedimentation surveys for 117 reservoirs, conducted by the Illinois State Water Survey over the past 60 years, were used to determine regional constants K to represent the severity of sediment deposition in the reservoirs. More than half of the 82 water supply reservoirs investigated had records of reservoir sedimentation surveys, and their K values were calculated by using data from those sediment surveys. The average K values of the remaining non‐surveyed water supply reservoirs were estimated from the regional distribution of the K values. Other important factors considered in the estimation of future reservoir storage capacities are the trap efficiency of the reservoirs and the variation of density of sediment deposits due to compaction. The model can also be used for analyzing the economics of alternative sites and of design features that can be incorporated in dams for reducing reservoir sedimentatio

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb03061.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTS: Modeling error can be divided into two basic components: use of an incorrect model and input parameter uncertainty. Incorrect model usage can be further subdivided into inappropriate model selection and inherent modeling error due to process aggregation. Total modeling error is a culmination of these various modeling error components, with overall optimization requiring reductions in all.A technique, utilizing Monte Carlo analysis, is employed to investigate the relative importance of input parameter uncertainty versus process aggregation error. An expanded form of the Streeter‐Phelps dissolved oxygen equation is used to demonstrate the application of this technique. A variety of scenarios are analyzed to illustrate the relative obfuscation of each modeling error component. Under certain circumstances an aggregated model performs better than a more complex model, which perfectly simulates the real system. Alternately, process aggregation error dominates total modeling error for other situations. The ability to differentiate modeling error impact is a function of the desired or imposed model performance level (accuracy tolerance

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb03062.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:Toxic organic compounds, such as DBCP, EDB, and c TCP, that are associated with pineapple cultivation in Hawaii have been discovered in drinking water wells on Oahu. In order to reach and contaminate the Pearl Harbor aquifer, pesticides must be transported quickly downward away from the soil surface prior to complete volatilization, degradation, or adsorption of residuals. This paper assesses the role of pesticide application timing relative to subsequent rainfall‐induced recharge events in determining the amount and extent of chemical leaching from the soil. A water balance model for a pineapple crop is developed to estimate the time series of recharge from two fields for which soil contamination profiles are available. In general, the amounts of DBCP, EDB, and TCP found in the soil profiles of the two fields are consistent with expectations of leaching based on an analysis of the recharge time series. The results indicate that recharge during and immediately following the application of pesticides is important in determining whether groundwater contamination will resul

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb03063.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:Finite element and finite difference representations of the convective‐dispersive equation have been widely used in determining contaminant transport in ground water. Due to inherent uncertainties of the transport process, those representations are inexact and contain errors. Errors in field measurements are unavoidable. By combining a numerical model, a measurement equation, and the Kalman filter, optimal estimates of the state variable (contaminant concentration) can be obtained. This paper describes the algorithm and gives a numerical example of contaminant transport in a two‐dimensional ground water flow. The results show significant improvement in the estimated concentration distribution by using the filtering techni

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb03064.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:Carbon content was measured in sediments deposited in 58 small reservoirs across the United States. Reservoirs varied from 0.2 to 4000 km2 in surface area. The carbon content of sediment ranged from 0.3 to 5.6 percent, with a mean of 1.9 ± 1.1 percent. No significant differences between the soil and sediment carbon content were found using a paired t‐test or ANOVA. The carbon content of sediments in reservoirs was similar to the carbon content of surface soils (0–10 cm) in the watershed, except in watersheds with shrub or steppe (desert) vegetation. Based on the sediment accumulation rates measured in each reservoir, the calculated organic carbon accumulation rates among reservoirs ranged from 26 to 3700 gC m‐2yr‐1, with a mean of 675 ± 739 gC m‐2yr‐1. The carbon content and accumulation rates were highest in sediments from grassland watersheds. High variability was found in carbon content, carbon accumulation, and sediment accumulation rates due to individual watershed and reservoir characteristics rather than to any broad physiographic patterns. The carbon accumulation rates in these reservoir sediments indicate that reservoir sediments could be a significant sink for o

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb03065.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:The potential for joint public and private action for lake restoration is examined using Lake Apopka, Florida, as a case study. Initial calculations indicate that private incentives alone are inadequate to attract investment in a facility to grow and harvest water hyacinths for conversion to methane gas. However, the private externality of water quality improvement associated with harvesting water hyacinths provides a key linkage between the public's water quality objectives and the private gas producer's actions. In order to establish the potential basis for negotiation, the public's willingness‐to‐pay for environmental services associated with improved water quality is estimated and compared with the estimated subsidy required to induce private action. A conceptual framework is then presented for coordinating actions between private firms and public water management agencies in order to internalize the private externality of water quality improvement while simultaneously achieving the public and private objectives. Results indicate that the subsidization of water hyacinth production and harvesting compares favorably with alternative means of enhancing the water quality of Lake Apo

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb03066.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:The longitudinal dispersion of tracer material in rivers is simulated by a dead‐zone model that involves two coupled differential equations. For an instantaneous injection of tracer material, the problem is solved by the Laplace. Transform and numerical inversion to obtain the time‐concentration curve at any sampling station. The optimal values of the model parameters are estimated from field measurements. Applications of the model to three different rivers generally show that the model reproduces the longitudinal dispersion characteristics in natural streams with sufficient accur

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb03067.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:Ten topographic analysis methods were employed to estimate watershed mean slopes for 13 small forested watersheds (32 to 131 mi2) in East Texas. Of the ten methods employed, the mean slope curve is the most accurate but also the most tedious and laborious one. The method can be simplified by measuring only the lengths of five contours and the areas between these contours within the watershed with little loss of its accuracy. Watershed slopes estimated by the contour length method, the grid contour method, the systematic slope sampling method, and the simplified contour length method are satisfactory for general purposes and relatively simple. The watershed circumference‐stream length method, the length‐width axis method, the Justin method, and the regression plane method are not suitable for estimating watershed slopes in East Texas without modificat

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb03068.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY