Motorcycle conspicuity: An evaluation and synthesis of influential factors

Motorcycles are overrepresented in fatal motor vehicle accidents: The death rate for motorcycle riders of about 35 per 100,000,000 miles of travel compares with an overall vehicle death rate of 2.57 per 100,000,000 miles. In the attempt to reduce the frequency of automobile-motorcycle collisions, numerous studies have manipulated motorcycle and motorcyclist characteristics to enhance conspicuity. In this paper, we give a review of studies that examined the effectiveness of these measures. Subsequently, we take a critical look at the methods used in these studies to evaluate the effectiveness of conspicuity treatments. Furthermore, we identify factors yet to be considered in the empirical research in this area that may contribute to collisions with motorcycles. These include information-processing failures at the identification and decision stage, as well as more or less permanent factors potentially responsible for different information-processing failures. Transient factors related to the failure to detect motorcycles might include alcohol, fatigue/lack of sleep, inattention, and information overload, whereas more permanent factors might include “cognitive” conspicuity and fi eld dependence.     

Polycyclic aromatic hydrocarbon storage in a typical Cerrado of the Brazilian savanna

There may be important biological sources of polycyclic aromatic hydrocarbons (PAHs) to the global environment, particularly of naphthalene, phenanthrene, and perylene, that originate in the tropics. We (i) studied the distribution of PAHs among different compartments of a typical Cerrado to locate their sources and (ii) quantified the PAH storage of this ecosystem. The sum of 20 PAH (sigma20PAHs) concentrations ranged from 25 to 666 microg kg(-1) in plant tissue, 7.4 to 32 microg kg(-1) in litterfall, 206 to 287 microg kg(-1) in organic soil, and 10 to 79 microg kg(-1) in mineral soil. Among the living biomass compartments, the bark had the highest mean PAH concentrations and coarse roots the lowest, indicating that PAHs in the plants originated mainly from aboveground sources. Naphthalene and phenanthrene were the most abundant individual PAHs, together contributing 33 to 96% to the sigma20PAHs concentrations. The total storage of the X20PAHs in Cerrado was 7.5 mg m(-2) to a 0.15-m soil depth and 49 mg m(-2) to a 2-m soil depth. If extrapolated to the entire Brazilian Cerrado region, roughly estimated storages of naphthalene and phenanthrene correspond to 7300 and 400 yr of the published annual emissions in the United Kingdom, respectively. The storage of benzo[a]pyrene, a typical marker for fossil fuel combustion, in the Cerrado only corresponds to 0.19 yr of UK emissions. These results indicate that the Brazilian savanna comprises a huge reservoir of naphthalene and phenanthrene originating most likely from the aboveground parts of the vegetation or associated organisms. Thus, the Cerrado might be a globally important source of these PAHs.     

Leaching and degradation of corn and soybean pesticides in an Oxisol of the Brazilian Cerrados

Pesticide pollution of ground and surface water is of growing concern in tropical countries. The objective of this pilot study was to evaluate the leaching potential of eight pesticides in a Brazilian Oxisol. In a field experiment near Cuiabá, Mato Grosso, atrazine, chlorpyrifos, lambda-cyhalothrin, endosulfane alpha, metolachlor, monocrotofos, simazine, and trifluraline were applied onto a Typic Haplustox. Dissipation in the topsoil, mobility within the soil profile and leaching of pesticides were studied for a period of 28 days after application. The dissipation half-life of pesticides in the topsoil ranged from 0.9 to 14 d for trifluraline and metolachlor, respectively. Dissipation curves were described by exponential functions for polar pesticides (atrazine, metolachlor, monocrotofos, simazine) and bi-exponential ones for apolar substances (chlorpyrifos, lambda-cyhalothrin, endosulfane alpha, trifluraline). Atrazine, simazine and metolachlor were moderately leached beyond 15 cm soil depth, whereas all other compounds remained within the top 15 cm of the soil. In lysimeter percolates (at 35 cm soil depth), 0.8-2.0% of the applied amounts of atrazine, simazine, and metolachlor were measured within 28 days after application. Of the other compounds less than 0.03% of the applied amounts was detected in the soil water percolates. The relative contamination potentials of pesticides, according to the lysimeter study, were ranked as follows: metolachlor > atrazine = simazine > monocrotofos > endsulfane alpha > chlorpyrifos > trifluraline > lambda-cyhalothrin. This order of the pesticides was also achieved by ranking them according to their effective sorption coefficient Ke, which is the ratio of Koc to field-dissipation half-life.     

Atmospheric versus biological sources of polycyclic aromatic hydrocarbons (PAHs) in a tropical rain forest environment

To distinguish between pyrogenic and biological sources of PAHs in a tropical rain forest near Manaus, Brazil, we determined the concentrations of 21 PAHs in leaves, bark, twigs, and stem wood of forest trees, dead wood, mineral topsoil, litter layer, air, and Nasutitermes termite nest compartments. Naphthalene (NAPH) was the most abundant PAH with concentrations of 35 ng m(-3) in air (>85% of the sum of 21PAHs concentration), up to 1000 microg kg(-1) in plants (>90%), 477 microg kg(-1) in litter (>90%), 32 microg kg(-1) in topsoil (>90%), and 160 microg kg(-1) (>55%) in termite nests. In plants, the concentrations of PAHs in general decreased in the order leaves > bark > twigs > stem wood. The concentrations of most low-molecular weight PAHs in leaves and bark were near equilibrium with air, but those of NAPH were up to 50 times higher. Thus, the atmosphere seemed to be the major source of all PAHs in plants except for NAPH. Additionally, phenanthrene (PHEN) had elevated concentrations in bark and twigs of Vismia cayennensis trees (12-60 microg kg(-1)), which might have produced PHEN. In the mineral soil, perylene (PERY) was more abundant than in the litter layer, probably because of in situ biological production. Nasutitermes nests had the highest concentrations of most PAHs in exterior compartments (on average 8 and 15 microg kg(-1) compared to <3 microg kg(-1) in interior parts) and high PERY concentrations in all compartments (12-86 microg kg(-1)), indicating an in situ production of PERY in the nests. Our results demonstrate that the deposition of pyrolytic PAHs from the atmosphere controls the concentrations of most PAHs. However, the occurrence of NAPH, PHEN, and PERY in plants, termite nests, and soils at elevated concentrations supports the assumption of their biological origin.     

OPTIMAL GROUND WATER MANAGEMENT IN TWO-AQUIFER SYSTEMS1

ABSTRACT; This paper presents a numerical model for the prediction of optimal ground water withdrawal from a two-aquifer system by observing a set of constraints determined by the ecological conditions of the ground water basin. The aquifer system consists of an upper unconfined and a lower confined aquifer with a leaky stratum between them. It is assumed that water is withdrawn from the confined aquifer only, but the unconfined aquifer will also be affected due to the leakiness of the layer separating the upper and lower aquifers. Simulation and linear programming are employed for developing a computer model for the optimal management of such systems, with the objectives of determining withdrawal rates for predetermined ground water levels.     

Persistence of the fluoroquinolone antibiotic difloxacin in soil and lacking effects on nitrogen turnover

The environmental risks caused by the use of fluoroquinolone antibiotics in human therapeutics and animal husbandry are associated with their persistence and (bio)accessibility in soil. To assess these aspects, we administered difloxacin to pigs and applied the contaminated manure to soil. We then evaluated the dissipation and sequestration of difloxacin in soil in the absence and presence of plants within a laboratory trial, a mesocosm trial, and a field trial. A sequential extraction yielded antibiotic fractions of differing binding strength. We also assessed the antibiotic's effects on nitrogen turnover in soil (potential nitrification and denitrification). Difloxacin was hardly (bio)accessible and was very persistent under all conditions studied (dissipation half-life in bulk soil, >217 d), rapidly forming nonextractable residues. Although varying environmental conditions did not affect persistence, dissipation was accelerated in soil surrounding plant roots. Effects on nitrogen turnover were limited due to the compound's strong binding and small (bio)accessibility despite its persistence.     

Identification of soil contamination hotspots with veterinary antibiotics using heavy metal concentrations and leaching data—a field study in China

In regions with high livestock densities, the usage of antibiotics and metals for veterinary purposes or as growth promoters poses a risk in manured soils. We investigated to which degree the concentrations and depth distributions of Cu, Zn, Cr and As could be used as a tracer to discover contaminations with sulfonamides, tetracyclines and fluoroquinolones. Besides, we estimated the potential vertical translocation of antibiotics and compared the results to measured data. In the peri-urban region of Beijing, China, soil was sampled from agricultural fields and a dry riverbed contaminated by organic waste disposal. The antibiotic concentrations reached 110 μg kg^?1 sulfamethazine, 111 μg kg^?1 chlortetracycline and 62 μg kg^?1 enrofloxacin in the topsoil of agricultural fields. Intriguingly, total concentrations of Cu, Zn, Cr and As were smaller than 65, 130, 36 and 10 mg kg^?1 in surface soil, respectively, therewith fulfilling Chinese quality standards. Correlations between sulfamethazine concentrations and Cu or Zn suggest that in regions with high manure applications, one might use the frequently existing monitoring data for metals to identify potential pollution hotspots for antibiotics in topsoils. In the subsoils, we found sulfamethazine down to ≥2 m depth on agricultural sites and down to ≥4 m depth in the riverbed. As no translocation of metals was observed, subsoil antibiotic contamination could not be predicted from metal data. Nevertheless, sulfonamide stocks in the subsoil could be estimated with an accuracy of 35–200 % from fertilisation data and potential leaching rates. While this may not be sufficient for precise prediction of antibiotic exposure, it may very well be useful for the pre-identification of risk hotspots for subsequent in-depth assessment studies.     

Distribution and ecotoxicity of chlorotriazines in the Scheldt Estuary (B-Nl)

As part of the Endis-Risks project, the current study describes the occurrence of the chlorotriazine pesticides atrazine, simazine and terbutylazine in water, sediment and suspended matter in the Scheldt estuary (B-Nl) from 2002 to 2005 (3 samplings a year, 8 sampling points). Atrazine was found at the highest concentrations, varying from 10 to 736 ng/l in water and from 5 up to 10 ng/g in suspended matter. Simazine and terbutylazine were detected at lower concentrations. Traces of the targeted pesticides were also detected in sediments, but these were below the limit of quantification. As part of an ecotoxicological assessment, we studied the potential effect of atrazine on molting of Neomysis integer (Crustacea:Mysidacea), a resident invertebrate of the Scheldt Estuary and a proposed test organism for the evaluation of endocrine disruption. Following chronic exposure ( approximately 3 weeks), atrazine did not significantly affect mysid molting at environmentally relevant concentrations (up to 1 microg/l).