نتایج جستجو برای: 1 gypsum in reducing sediment concentration diminished 35 min after runoff initiation whereas

تعداد نتایج: 17723790  

Journal: :Environmental science & technology 2014
Peter C Van Metre Barbara J Mahler

Recent studies have concluded that coal-tar-based pavement sealants are a major source of polycyclic aromatic hydrocarbons (PAHs) in urban settings in large parts of the United States. In 2006, Austin, TX, became the first jurisdiction in the U.S. to ban the use of coal-tar sealants. We evaluated the effect of Austin's ban by analyzing PAHs in sediment cores and bottom-sediment samples collecte...

2011
J. Yu Y. Fu Y. Li G. Han Y. Wang D. Zhou W. Sun Y. Gao F. X. Meixner

The Yellow River, which is the second largest river in China, is regarded as the world’s largest contributor of fluvial sediment load to the ocean. In recent decades, the dramatic reduction in water discharge and sediment load due to climate change and human activities in the drainage basin has greatly constrained the evolution process of Yellow River delta. We highlight how runoff and sediment...

2001
Mathew P. Johansen Thomas E. Hakonson David D. Breshears

Rainfall simulations allow for controlled comparisons of runoff and erosion among ecosystems and land cover conditions. Runoff and erosion can increase greatly following fire, yet there are few rainfall simulation studies for post-fire plots, particularly after severe fire in semiarid forest. We conducted rainfall simulations shortly after a severe fire (Cerro Grande) in ponderosa pine forest n...

ژورنال: علوم آب و خاک 2018

One of the main sources of runoff in arid and semi-arid mountainous highlands is typically composed of before Quaternary formations. Since the structure and lithology of formations are different, varying formations can have different significance in terms of runoff and sediment. The present study aimed to investigate the sediment production potential and the runoff generation threshold on three...

2015
Tsung-Yu Lee Jr-Chuan Huang Jun-Yi Lee Shih-Hao Jien Franz Zehetner Shuh-Ji Kao Chon-Lin Lee

Fluvial sediment export from small mountainous rivers in Oceania has global biogeochemical significance affecting the turnover rate and export of terrestrial carbon, which might be speeding up at the recognized conditions of increased rainfall intensity. In this study, the historical runoff and sediment export from 16 major rivers in Taiwan are investigated and separated into an early stage (19...

Journal: :Journal of environmental quality 2002
Ranjith P Udawatta J John Krstansky Gray S Henderson Harold E Garrett

A paired watershed study consisting of agroforestry (trees plus grass buffer strips), contour strips (grass buffer strips), and control treatments with a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation was used to examine treatment effects on runoff, sediment, and nutrient losses. During the (1991-1997) calibration and subsequent three-year treatment periods, runoff was measured in...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه فردوسی مشهد 1388

two groups of students were assigned as experimental and control ones, and were given instruction on directed reading-thinking activities and after some treatment, they were post-tested. although the initial pre-test did not show any significant differences, the final post-test result revealed that the cooperative reading comprehension helped the experimental group. the cooperative students’...

2000

Potential contamination (pollution) of surface waters with sediment, nutrients, and pesticides in agricultural runoff is an important water quality issue. Conservation tillage has been promoted and adopted by many row crop farmers because of its effectiveness in decreasing exposure to rainfall and reducing runoff and sediment loss. Vegetative filter strips (VFS), also known as buffer strips or ...

2016
M. E. Mohammad

Estimation of runoff volume and sediment load is a problem that directly affects the performance of dams due to the reduction in the storage capacity of their reservoirs and their effect on dam efficiency and operation schedule. The simulation models can be considered for evaluation of sediment potential if the continuous field measurements are not available. Soil and Water Assessment Tool (SWA...

Journal: :Archives of environmental contamination and toxicology 2007
J L Bouldin J L Farris M T Moore S Smith C M Cooper

Constructed wetlands for mitigation of nonpoint agricultural runoff have been assessed for their ability to decrease potential toxicity from associated contaminants. After a simulated runoff event, constructed wetlands positioned in series were used to measure the effects of the organophosphate insecticide diazinon. Water, sediment, and plant samples from five sites were analyzed for diazinon c...

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