The dispersion of pollutants beneath open channels     

John C. Bruch Jr.  Paul Smith 《Water, air, and soil pollution》1973,2(1):23-34

An experiment and a numerical scheme which combine previously given methods for the dispersion and seepage phenomena have been presented to describe the dispersion of a pollutant in porous media beneath a triangular channel. The combined effect of longitudinal and lateral dispersion was considered. Numerical concentration profiles are given along with a comparison of experimental and numerical data. The technique suggested herein can be extended to other channel shapes and flow fields accounting for the capillary fringe.  相似文献   

Alkalinity destruction by sediment organic matter dissolution during neutralization of acidified lakes     

James J. Bisogni Jr.  Scott A. Kishbaugh 《Water, air, and soil pollution》1988,38(1-2):85-95

In this study we report on the effect of sediment, from an acidified lake, on the neutralization of the acidified water column. The results of this experimental study show that organic acids (presumably humic or fulvic acids) can dissolve from the sediment and destroy alkalinity as measured by a Gran plot analysis. Alkalinity destruction by organic acid dissolution was shown to be a function of pH. Some Na ion exchange for sediment H⁺ was also observed. This ion exchange was shown to be a function of pH and Na concentration.  相似文献   

Mercury species in potable ground water in southern New Jersey     

Eileen A. Murphy  John Dooley  Herbert L. Windom  Ralph G. Smith Jr. 《Water, air, and soil pollution》1994,78(1-2):61-72

Water samples from 78 private potable wells in southern New Jersey were collected for mercury analysis in 1991–1992. Analyses were performed for the quantification of reactive, volatile and methyl mercury species. Relationships of mercury with other water quality parameters were evaluated also. Total mercury concentrations varied from <1 ng L^?1 to over 36 Μg L^?1. The dominant forms in which mercury occurred in the wells sampled were Hg? and HgCl₂?, although methyl mercury was present in some wells and comprised up to 8% of the total mercury in the ground water samples.  相似文献   

Episodic acidification of freshwater systems in Canada — Physical and geochemical processes     

Martyn Tranter  Trevor D. Davies  P. J. Wigington Jr.  Keith N. Eshleman 《Water, air, and soil pollution》1994,72(1-4):19-39

The occurrence of episodic acidification in Canadian streams, lake waters and shallow groundwaters has been reviewed, and the contolling mechanisms identified. ‘Episodes’, which are periods of depressed alkalinity during hydrological events, have been studied mainly in southeastern Canada, and occur at all sites where there is sufficient time resolution of the observations, viz. Ontario, Quebec and Nova Scotia. An ‘alkaline episode’, where acidity decreases during an event, has been reported from one lake in the Canadian Artic. There is a bias towards the examination of episodes stimulated by snowmelt or rain-on-snow, since rainfall-stimulated episodes are poorly documented. Pre-event, rather than event, water dominates runoff during episodes. For this reason, biogeochemical reactions and the hydrological flowpaths in operation through the vadose and saturated zones are the principal controls on the chemical characteristics of episodes. Most episodes are dominated by base cation ‘dilution’ in circumneutral systems, and ‘increase in strong acid anions’ (particularly sulphate) in acidic systems. Episodes dominated by nitrification or organic acids or stimulated by sea salt input are rare or have not been decumented. Direct input of event water may dominate only during particular circumstances at snowmelt. Then, direct chemical inputs from lake ice and lake snow cover may be of importance in some systems.  相似文献   

Arbuscular mycorrhizal fungus (Glomus aggregatum) influences biotransformation of arsenic in the rhizosphere of sunflower (Helianthus annuus L.)   总被引：2，自引：0，他引：2  

Venecio U. Y. ULTRA Jr    Sota TANAKA  Katsutoshi SAKURAI  K&#;z&#; IWASAKI 《Soil Science and Plant Nutrition》2007,53(4):499-508

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Bird communities, roads and development: prospects and constraints of applying empirical models     

Kevin J. Gutzwiller  Wylie C. Barrow Jr. 《Biological conservation》2003,113(2):239-243

Our objectives were to explain the prospects and constraints of applying empirical models that relate bird community metrics to broad-scale characteristics of roads and development. We explored the practical value of regression models that were derived for a large protected area in the Chihuahuan Desert. These models related bird species richness, relative abundance, or probability of occurrence to total length of roads within each of two spatial extents (1- and 2-km radii), distance to the nearest road, distance to the nearest development, or the two-way interactions of these variables. Empirical models can be used to inform conservation decisions, to parameterise simulation models for conservation planning, to identify threshold levels of road and development variables, and to determine the focus of management experiments for confirmatory hypothesis testing and improvement of model realism.  相似文献   

Quantitative monitoring of airborne lead pollution by a foliose lichen     

David Schwartzman  Margaret Kasim  Lorin Stieff  James H. Johnson Jr. 《Water, air, and soil pollution》1987,32(3-4):363-378

The potential use of lichens as quantitative monitors of airborne heavy metal pollution has been demonstrated by measurements of Po²¹⁰, Pb, Cd, Zn, and V levels in sequential growth of the foliose lichen Pseudoparmelia baltimorensis from three localities in the greater Washington, D.C. area. Samples were dated using the growth rate measured by Lawrey and Hale (1977). Po²¹⁰, Pb, and V increase with age in a given colony. Higher levels of Pb, V, Cd, and Zn are present in samples from the two more polluted sites. The retention of heavy metals is consistent with trapping by an ion exchange mechanism. Since Po²¹⁰ is the daughter product of in situ decay of Pb²¹⁰, accumulated from atmospheric fallout of known rate, its levels can be used to calculate trapping efficiencies of Pb and retrospective fallout rates. These rates are similar to published data from rural and urban areas.  相似文献   

Kepone effects on larval development of mud-crab and blue-crab     

C. G. Bookhout  J. D. Costlow Jr.  R. Monroe 《Water, air, and soil pollution》1980,13(1):57-77

Laboratory experiments wer conducted to determine the effects of Kepone on the larval development of the mud-crab,Rhithropanopeus harrisii, and the commercial blue crab,Callinectes sapidus, from the time of hatching until the 1st crab stage was reached. Differential survival ofR. harrisii from hatching to 1st crab stage occurred in a range of 35 to 125 ppb Kepone, whereas differential survival ofC. sapidus over the same period of development occurred in a range of 0.1 to 1.0 ppb. Statistical analysis indicated that, for every 10 ppb Kepone added, duration from hatching to 1st crab stage ofR. harrisii was increased by 0.391±0.043 days; whereas for each increase of 0.1 ppb, the duration from hatching to 1st crab stage ofC. sapidus is prolonged by 0.38±0.10 days. The 1st and 2nd zoeal stages ofR. harrisii were the most sensitive developmental stages to Kepone, but the 1st zoeal stage ofC. sapidus was not sensitive, statistically, to any concentration of Kepone tested. In zoeal stages II, III and IV, there were significant increases in mortality ofC. sapidus over the previous stage in all media tested.  相似文献   

Intermediate mixing of thermal discharges into a uniform current     

John Eric Edinger  Edward M. Polk Jr. 《Water, air, and soil pollution》1971,1(1):7-31

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Effects of increasing acidity on aquatic protozoan communities     

B. R. Niederlehner  John Cairns Jr. 《Water, air, and soil pollution》1990,52(1-2):183-196

Laboratory tests were conducted to evaluate the chronic effects of increased acidity on protozoan communities. Taxonomic richness of the protozoan component of these communities was severely affected at pH ≤ 5.33. Taxonomic composition was significantly affected at much higher pH. A permissible concentration was defined as the pH affecting no more than 20% of the species and estimated from concentration-response regression as 6.92 (5.92 to 8.04) pH units. A similar value estimated from more conventional chronic toxicity tests was 6.28 (6.16 to 6.45) pH units. Bacterial abundance decreased at pH levels ≤ 5.34 pH units. Other nontaxonomic responses (e.g., biomass, algal biomass, fungal biomass, net oxygen metabolism) were not sensitive to increases in acidity.  相似文献