EFFECTIVENESS OF POLYACRYLAMIDE (PAM) IN IMPROVING RUNOFF WATER QUALITY FROM CONSTRUCTION SITES1

ABSTRACT: Erosion from construction sites significantly affects water quality in receiving streams. A rainfall simulator was used to evaluate the effectiveness of different methods for controlling erosion from construction sites. Erosion control methods investigated included dry and liquid applications of polyacrylamide (PAM), hydroseed, and straw mulch. Fertilizer was also applied to each plot to examine the effectiveness of the methods in reducing nutrient losses in runoff. Runoff samples were analyzed for total suspended solids (TSS), nitrate, total Kjeldahl nitrogen (TKN), ammonium, total phosphorus (TP), and orthophosphate. Among all treatments investigated, straw mulch was the most effective treatment for controlling TSS and nutrient losses during short term and long term simulations. The low liquid PAM (half the recommended PAM) treatment resulted in the highest reduction in runoff, TSS bound nitrogen, and total nitrogen (TN) concentrations and loadings. The study results indicate that a high application rate (twice the recommended rate) of PAM could actually increase runoff and TSS losses. At a low application rate, both liquid and dry PAM were effective in reducing TSS and nutrient losses in runoff. However, application of the liquid form of PAM to construction sites is more practical and perhaps more economical than applying the PAM in the dry form.     

Immobilizing a light,nonaqueous phase liquid

A new technique has been developed to immobilize organic chemicals at a Superfund site. In the course of predesign studies in preparing the Remedial Design for the Pioneer Sand Superfund site in Pensacola, Florida, a light, nonaqueous phase liquid (LNAPL) was discovered floating on the groundwater within the on-site landfill. The liquid, with a viscosity similar to SAE 20 motor oil, was made up of heavy organic chemicals and volatile organic chemicals (VOCs), but no pesticides or polychlorinated biphenyls (PCBs). The volatiles present included toluene, ethylbenzene, and xylenes. Regulatory agencies expressed concern over the possibility of LNAPL migration and asked that a method of LNAPL immobilization be devised.     

AN OVERVIEW OF POROUS PAVEMENT RESEARCH1

ABSTRACT: This paper discusses the economics, advantages, potential applications, and status and future research needs of porous pavements. Porous pavements are an available storm water management technique which can be used on parking lots and low volume roadways in order to reduce both storm water runoff volume and pollution. In addition, ground water recharge is enhanced. Also, cost reductions result due to elimination of curbs, drains, and small sized storm sewers. Porous asphalt pavements consist of a relatively thin course of open graded asphalt mix over a deep base of large size crushed stones. Water can be stored in the crushed stone base until it can percolate into the subbase or drain laterally. Other porous pavement types include concrete lattice blocks and a porous concrete mix.     

Development of a Grassland Integrity Index Based on Breeding Bird Assemblages

We utilized landscape and breeding bird assemblage data from three Breeding Bird Survey (BBS) routes sampled from 1965–1995 to develop and test a grassland integrity index (GII) in a mixed-grass prairie area of Oklahoma. The overall study region is extensively fragmented from long-term agricultural activity, and native habitat remnants have been degraded by recent encroachment of woody vegetation, namely eastern redcedar (Juniperus virginiana L.). The 50 individual bird survey points along the BBS routes, known as stops, were used as sample sites. Our process first focused on developing a grassland disturbance index (GDI) as a measure of cumulative landscape disturbances for these sites. The GDI was based on five key landscape variables identified in an earlier species-level study of long-term avian community dynamics: total tree, shrub, and herbaceous vegetation cover indices, overall mean landscape patch size, and grassland patch core size. The GII was then developed based on breeding bird assemblage data. Assemblages were based on commonly used response guilds reflective of five avian life history parameters: foraging mode/location, nesting location, habitat specificity, migratory pattern, and dietary guild. We tested the response of 78 candidate assemblage metrics to the GDI, and eliminated those with no or poor response or with high correlations (redundant), resulting in 13 metrics for use in the final index. Individual metric scores were scaled to fall between 0 and 10, and the cumulative index to range from 0 to 100. Although broader application and refinement are possible, the avian-based GII has an advantage over labor-intensive, habitat-based monitoring in that the GII is derived from readily available long-term BBS data. Therefore, the GII shows promise as an inexpensive tool that could easily be applied over other areas to monitor changes in regional grassland conditions.     

Evidence that plant varieties respond differently to NO2 pollution as indicated by resistance to insect herbivores

The effects of NO(2) pollution on the performance of aphids feeding on different bean varieties were investigated by fumigation experiments. The susceptibility of the different genotypes dramatically changed as the concentration of atmospheric pollutant was increased. The direction of change was not constant between varieties. Our data suggest that resistance or susceptibility of a plant variety to insect herbivory can be significantly altered when subjected to pollutant stress, thus indicating that it may be difficult to predict the susceptibility of host plants in a polluted atmosphere.     

Herbicides: A new threat to the Great Barrier Reef

The runoff of pesticides (insecticides, herbicides and fungicides) from agricultural lands is a key concern for the health of the iconic Great Barrier Reef, Australia. Relatively low levels of herbicide residues can reduce the productivity of marine plants and corals. However, the risk of these residues to Great Barrier Reef ecosystems has been poorly quantified due to a lack of large-scale datasets. Here we present results of a study tracing pesticide residues from rivers and creeks in three catchment regions to the adjacent marine environment. Several pesticides (mainly herbicides) were detected in both freshwater and coastal marine waters and were attributed to specific land uses in the catchment. Elevated herbicide concentrations were particularly associated with sugar cane cultivation in the adjacent catchment. We demonstrate that herbicides reach the Great Barrier Reef lagoon and may disturb sensitive marine ecosystems already affected by other pressures such as climate change.     

Alzheimer's disease: molecular concepts and therapeutic targets

The beta amyloid peptide is the major component of the neuritic plaques, the characteristic lesions in Alzheimer's disease. Mutations in three genes (APP, PS-1, and PS-2) cause familial Alzheimer's disease by alteration of the rate of generation of amyloid peptide or the length of this peptide. However, in the 90% non-familial cases, other factors play a major pathogenetic role. These include the apolipoprotein E genotype, the "plaque-associated" proteins promoting the formation of toxic fibrillar aggregates or the chronic inflammatory responses. The aim of this review is to explain the steps in the complex cascade leading to Alzheimer's disease and, based on this, to report the current efforts to intervene in these different pathophysiological events in order to prevent progression of Alzheimer's disease. Whereas acetylcholine substitution is currently used in clinical practice, future therapeutical strategies to combat Alzheimer's disease may include anti-inflammatory treatments, vaccination against beta amyloid peptide, or treatment with cholesterol-lowering drugs.     

Vibrations in the orbwebs of Nuctenea sclopetaria (Araneidae)

Summary Orbweaving spiders obtain much information from web-borne vibrations. One of their major problems is to distinguish relevant vibrations, particularly prey-produced signals, from irrelevant vibrations, particularly wind noise. This problem was studied by measuring the spectral characteristics of prey-and wind-induced web vibrations, and the spider's responsiveness to sinusoidal stimuli. In wind-generated vibration (Fig. 1) signal amplitude is large below 10 Hz and decreases by 30 to 40 dB/decade above the lowest resonance frequency for each type of web vibration. The lowest resonance for transverse vibration is 3 Hz with a 200 mg spider, and 10 Hz for longitudinal and lateral vibration. Below 10 Hz transverse vibration is much larger than the other two types, but this difference decreases at higher frequencies. Most of the amplitude in prey signals is below 50 Hz (Fig. 2), except for buzzing insects such as flies, bees and mosquitoes, whose high wing beats generate significant motion above 100 Hz. The spider's response threshold for sinusoidal stimuli in the prey-catching region of the web (Fig. 3) declines at 20 dB/decade over the range that could be measured (10 to 3,200 Hz for longitudinal, 18 to 560 Hz for transverse and 18 to 320 Hz for lateral vibration). The threshold curve for longitudinal vibration is 10 to 20 dB lower than for the other two types and has a minimum of 7 m RMS near 300 Hz. This difference appears to have a mechanical rather than a sensory basis, due to the better transmission of longitudinal vibration through the web (Fig. 4A). If the effect of the spider on web vibration is also considered, the resulting adjusted threshold curve (Fig. 4B: data available for longitudinal vibration only), shows a continuous decline of approximately 30 dB/decade. A possible mechanism for recognizing prey signals based on spectral information is discussed.