Buffer zone widths for honeybees from ground and aerial spraying of insecticides

The relative field hazards of insecticides to honeybees have been estimated by considering intrinsic toxicity levels and field application rates. This approach is extended here to a consideration of buffer zones downwind of sprayed areas by estimating the distance at which bees would encounter an LD(50) dose from spray drift. 'LD(50) distances' are determined for both ground and aerial spraying of ground crops in Britain using published data on spray deposition under various weather conditions. For ground spraying at low wind speeds (< or =3 m s(-1)), this zone of risk is up to 5 m for the great majority of compounds. Aerial spraying in unstable atmospheric conditions appears to produce drift deposits of about the same order of magnitude as from ground spraying at wind speeds of about 4 m s(-1), with maximum LD(50) distances of < or =40 m for chlorpyrifos, fenitrothion and triazophos. For aerial spraying in stable atmospheric conditions these distances would be much greater. Pieris brassicae larvae are contrasted with honeybees in their relative sensitivities to insecticides and consequent LD(50) distances.     

Comparison of spray drift- and runoff-related input of azinphos-methyl and endosulfan from fruit orchards into the Lourens River, South Africa.

Spray drift and edge-of-field runoff are regarded as important routes of nonpoint-source pesticide input into aquatic surface waters, with current regulatory risk assessment in Europe focussing largely on spray drift. However, the two routes of entry had rarely been compared directly in the same catchment. To this end, the concentrations and loads of the current-use insecticides azinphos-methyl (AZP) and endosulfan (END) were monitored in the Lourens River, South Africa downstream of a 400-ha fruit orchard area during normal farming practice. Spray drift-related peak pesticide levels in the tributaries were in the range of 95th-percentiles of standard drift values according to regulatory risk assessment procedures. Resulting concentrations in Lourens River water samples (n = 3) at a discharge of 0.28 m3/s were as high as 0.04 +/- 0.01 microg/l AZP and 0.07 +/- 0.02 microg/l END. Pesticide levels at the same site during runoff following 3 storm events varying in rainfall between 6.8 and 18.4 mm/d (discharge: 7.5-22.4 m3/s) were considerably higher: by factors between 6 and 37 for AZP (0.26-1.5 microg/l) and between 2 and 41 for END (0.13-2.9 microg/l). Levels of pesticides associated with suspended particles were increased during runoff only up to 1247 microg/kg AZP and 12082 microg/kg END. A possible reason for the relative importance of runoff is that runoff largely integrates potential pesticide input over both time and space, because the prerequisites for the occurrence of runoff in terms of application and plot characteristics as well as meteorological conditions are far less specific than for spray drift. A probability analysis based on pesticide application patterns and 10-yr rainfall data indicates that the frequencies of rainfall events > or = 10 and > or = 15 mm/d are 3.4 and 1.7 per spraying season, respectively.     

Assessment of the effects of herbicide spray drift on a range of plant species of conservation interest

With increasing use of herbicides there has been growing concern that spray drift from treated land will affect vegetation on adjacent nature reserves and other areas of high conservation interest. A preliminary attempt was made to assess this risk by placing a range of native plant species at different distances downwind from standardised drift events and assessing lethal effects and sublethal damage. Five herbicides were tested: asulam, 'Finesse' (chlorsulfuron + metsulfuron-methyl), glyphosate, MCPA and mecoprop. Applications were made at the appropriate time of years for each herbicide (autumn, spring and summer), and at both low and high wind speeds. The maximum safe distance at which no lethal effects were found was 6 m from the sprayer, but for most herbicides the distance was 2 m or less. Generally, damage symptoms were found at greater distances than lethal effects, but in most cases there was rapid recovery by the end of the growing season. These observations are consistent with drift-deposition models, in which the fallout of herbicide droplets has been measured. It is suggested that buffer zones surrounding nature reserves should be in the order of 5-10 m for ground sprayers to minimise the risk of herbicide impacts on these habitats.     

Defining the spatial impacts of poultry farm ammonia emissions on species composition of adjacent woodland groundflora using Ellenberg Nitrogen Index,nitrous oxide and nitric oxide emissions and foliar nitrogen as marker variables

The marker variables, Ellenberg Nitrogen Index, nitrous oxide and nitric oxide fluxes and foliar nitrogen, were used to define the impacts of NH3 deposition from nearby livestock buildings on species composition of woodland ground flora, using a woodland site close to a major poultry complex in the UK. The study centred on 2 units in close proximity to each other, containing 350,000 birds, and estimated to emit around 140,000 kg N year(-1) as NH3. Annual mean concentrations of NH3 close to the buildings were very large (60 microg m(-3)) and declined to 3 microg m(-3) at a distance of 650 m from the buildings. Estimated total N deposition ranged from 80 kg N ha(-1) year(-1) at a distance of 30 m to 14 kg N ha(-1) year(-1) at 650 m downwind. Emissions of N2O and NO were 56 and 131 microg N m(-2) h(-1), respectively at 30 m and 13 and 80 microg N m(-2) h(-1), respectively at 250 m downwind of the livestock buildings. Species number in woodland ground flora downwind of the buildings remained fairly constant for a distance of 200 m from the units then increased considerably, doubling at a distance of 650 m. Within the first 200 m downwind, trends in plant species composition were hard to discern because of variations in tree canopy composition and cover. The mean Ellenberg N Index ranged from 6.0 immediately downwind of the livestock buildings to 4.8 at 650 m downwind. The mean abundance weighted Ellenberg N Index also declined with distance from the buildings. Tissue N concentrations in trees, herbs and mosses were all large, reflecting the substantial ammonia emissions at this site. Tissue N content of ectohydric mosses ranged from approximately 4% at 30 m downwind to 1.6% at 650 m downwind. An assessment of the relative merits of the three marker variables concludes, that while Ellenberg Index and trace gas fluxes of N2O and NO give broad indications of impacts of ammonia emissions on woodland vegetation, the application of a critical foliar N content for ectohydric mosses is the most useful method for providing spatial information which could be of value to policy developers and planners.     

Effects of herbicide spray drift on selected species of nature conservation interest: the effects of plant age and surrounding vegetation structure

There has been increasing awareness of the possible impact of herbicide drift on vegetation in nature reserves and field-margin habitats adjacent to treated areas. However, relatively little is known about the impact of such drift on species typical of these habitats. To investigate this problem a series of bioassay experiments simulating spray drift were carried out with five native plant species of different age placed at different distances up to 4 downwind from a sprayer under standardized conditions. These experiments used three herbicides--glyphosate, MCPA and mecoprop--in three types of surrounding vegetation structure--short, medium-height and tall grassland. Many plants showed symptoms of damage after spraying but showed no significant growth reduction at the end of the season even underneath the sprayer. Where a reduction in yield was found, it occurred close to the sprayer. In general, young plants were more often affected than old ones. Yield promotion occurred for some species between 2 and 4 m downwind of the sprayer (curvilinear response) with unknown ecological consequences. The structure of the surrounding vegetation influenced the response for some species, which indicates that deposition patterns can be complex, and thus there may be difficulty in predicting effects in semi-natural communities from simple deposition models.     

Concentration and size distribution of ultrafine particles near a major highway

Motor vehicle emissions usually constitute the most significant source of ultrafine particles (diameter <0.1 microm) in an urban environment, yet little is known about the concentration and size distribution of ultrafine particles in the vicinity of major highways. In the present study, particle number concentration and size distribution in the size range from 6 to 220 nm were measured by a condensation particle counter (CPC) and a scanning mobility particle sizer (SMPS), respectively. Measurements were taken 30, 60, 90, 150, and 300 m downwind, and 300 m upwind, from Interstate 405 at the Los Angeles National Cemetery. At each sampling location, concentrations of CO, black carbon (BC), and particle mass were also measured by a Dasibi CO monitor, an aethalometer, and a DataRam, respectively. The range of average concentration of CO, BC, total particle number, and mass concentration at 30 m was 1.7-2.2 ppm, 3.4-10.0 microg/m3, 1.3-2.0 x 10(5)/cm3, and 30.2-64.6 microg/m3, respectively. For the conditions of these measurements, relative concentrations of CO, BC, and particle number tracked each other well as distance from the freeway increased. Particle number concentration (6-220 nm) decreased exponentially with downwind distance from the freeway. Data showed that both atmospheric dispersion and coagulation contributed to the rapid decrease in particle number concentration and change in particle size distribution with increasing distance from the freeway. Average traffic flow during the sampling periods was 13,900 vehicles/hr. Ninety-three percent of vehicles were gasoline-powered cars or light trucks. The measured number concentration tracked traffic flow well. Thirty meters downwind from the freeway, three distinct ultrafine modes were observed with geometric mean diameters of 13, 27, and 65 nm. The smallest mode, with a peak concentration of 1.6 x 10(5)/cm3, disappeared at distances greater than 90 m from the freeway. Ultrafine particle number concentration measured 300 m downwind from the freeway was indistinguishable from upwind background concentration. These data may be used to estimate exposure to ultrafine particles in the vicinity of major highways.     

Deposition and removal of fugitive dust in the arid southwestern United States: measurements and model results

This work was motivated by the need to better reconcile emission factors for fugitive dust with the amount of geologic material found on ambient filter samples. The deposition of particulate matter with aerodynamic diameter less than or equal to 10 microm (PM10), generated by travel over an unpaved road, over the first 100 m of transport downwind of the road was examined at Ft. Bliss, near El Paso, TX. The field conditions, typical for warm days in the arid southwestern United States, represented sparsely vegetated terrain under neutral to unstable atmospheric conditions. Emission fluxes of PM10 dust were obtained from towers downwind of the unpaved road at 7, 50, and 100 m. The horizontal flux measurements at the 7 m and 100 m towers indicated that PM10 deposition to the vegetation and ground was too small to measure. The data indicated, with 95% confidence, that the loss of PM10 between the source of emission at the unpaved road, represented by the 7 m tower, and a point 100 m downwind was less than 9.5%. A Gaussian model was used to simulate the plume. Values of the vertical standard deviation sigma(z) and the deposition velocity Vd were similar to the U.S. Environmental Protection Agency (EPA) ISC3 model. For the field conditions, the model predicted that removal of PM10 unpaved road dust by deposition over the distance between the point of emission and 100 m downwind would be less than 5%. However, the model results also indicated that particles larger than 10 microm (aerodynamic diameter) would deposit more appreciably. The model was consistent with changes observed in size distributions between 7 m and 100 m downwind, which were measured with optical particle counters. The Gaussian model predictions were also compared with another study conducted over rough terrain and stable atmospheric conditions. Under such conditions, measured PM10 removal rates over 95 m of downwind transport were reported to be between 86% and 89%, whereas the Gaussian model predicted only a 30% removal. One explanation for the large discrepancy between measurements and model results was the possibility that under the conditions of the study, the dust plume was comparable in vertical extent to the roughness elements, thereby violating one of the model assumptions. Results of the field study reported here and the previous work over rough terrain bound the extent of particle deposition expected to occur under most unpaved road emission scenarios.     

Sources of PM10 and sulfate aerosol at McMurdo Station, Antarctica

Source contributions to PM10 and sulfate aerosol at McMurdo Station, Antarctica during the austral summers of 1995-1996 and 1996-1997 were estimated using Chemical Mass Balance (CMB) receptor modeling. The average PM10 (particles with aerodynamic diameters less than 10 microm) concentration at Hut Point, located less than 1 km downwind of downtown McMurdo, was 3.4 microg/m3. Emissions profiles were determined for potentially important aerosol source types in McMurdo: exposed soil, power generation, space heating, and surface vehicles. Soil dust, sea salt, combustion emissions, sulfates, marine biogenic emissions as methanesulfonate, and nitrates contributed 57%, 15%, 14%, 10%, 3%, and 1%, respectively, of average estimated PM10 at Hut Point (3.2 microg/m3). Soil dust, sea salt, and combustion sources contributed 12%, 8%, and 20%, respectively, of the average PM10 sulfate concentration of 0.46 microg/m3. Marine biogenic sources contributed 0.17 microg/m3 (37%). The remaining sulfate is thought to have come from emissions from Mt. Erebus or hemispheric pollution sources.     

Concentrations of ammonia and nitrogen dioxide at roadside verges, and their contribution to nitrogen deposition

Bimonthly integrated measurements of NO2 and NH3 have been made over one year at distances up to 10 m away from the edges of roads across Scotland, using a stratified sampling scheme in terms of road traffic density and background N deposition. The rate of decrease in gas concentrations away from the edge of the roads was rapid, with concentrations falling by 90% within the first 10 m for NH3 and the first 15 m for NO2. The longer transport distance for NO2 reflects the production of secondary NO2 from reaction of emitted NO and O3. Concentrations above the background, estimated at the edge of the traffic lane, were linearly proportional to traffic density for NH3 (microg NH3 m(-3) = 1 x 10(-4) x numbers of cars per day), reflecting emissions from three-way catalysts. For NO2, where emissions depend strongly on vehicle type and fuel, traffic density was calculated in terms of 'car equivalents'; NO2 concentrations at the edge of the traffic lane were proportional to the number of car equivalents (microg NO2 m(-3) = 1 x 10(-4) x numbers of car equivalents per day). Although absolute concentrations (microg m(-3)) of NH3 were five times smaller than for NO2, the greater deposition velocity for NH3 to vegetation means that approximately equivalent amounts of dry N deposition to road side vegetation from vehicle emissions comes from NH3 and NO2. Depending on traffic density, the additional N deposition attributable to vehicle exhaust gases is between 1 and 15 kg N ha(-1) y(-1) at the edge of the vehicle lane, falling to 0.2-10 kg N ha(-1) y(-1) at 10 m from the edge of the road.     

The impact of a building implosion on airborne particulate matter in an urban community

In response to community concerns, the air quality impact of imploding a 22-story building in east Baltimore, MD, was studied. Time- and space-resolved concentrations of indoor and outdoor particulate matter (PM) (nominally 0.5-10 microm) were measured using a portable nephelometer at seven and four locations, respectively. PM10 levels varied in time and space; there was no measurable effect observed upwind of the implosion. The downwind peak PM10 levels varied with distance (54,000-589 microg/m3) exceeding pre-implosion levels for sites 100 and 1130 m 3000- and 20-fold, respectively. Estimated outdoor 24-hr integrated mass concentrations varied from 15 to 72 microg/m3. The implosion did not result in the U.S. Environmental Protection Agency (EPA) National Ambient Air Quality Standard (NAAQS) for PM10 being exceeded. X-ray fluorescence analysis indicated that the elemental composition was dominated by crustal elements: calcium (57%), silicon (23%), aluminum (7.6%), and iron (6.1%). Lead was above background but at a low level (0.17 microg/m3). Peak PM10 concentrations were short-lived; most sites returned to background within 15 min. No increase in indoor PM10 was observed even at the most proximate 250 m location. These results demonstrate that a building implosion can have a severe but short-lived impact on community air quality. Effective protection is offered by being indoors or upwind.     

Determination of pendimethalin (PROWL®480 EC) spray drift from ground applications

Abstract

Pendimethalin herbicide (PROWL^®480 EC) spray drift was determined from ground applications representing the highest rate applied to corn in eastern Canada. A novel drift collector pattern was laid out on the ground immediately before herbicide application. Most of the drift collectors were located downwind of the application target area. The maximum labelled rate of 1.68 kg ai/Ha was applied on 2 occasions on separate sites. In both applications, drift collector cards indicated that concentrations of pendimethalin were not detectable outside the target zone (<0.01 μg/cm²) at or beyond the 10 metre drift collector stations. Risk assessment calculations indicated that non‐target organisms would not be at significant risk from off‐site movement of pendimethalin.     

Evaluation of watering to control dust in high winds

A field study was conducted to determine the effectiveness of watering in controlling PM10 emissions under high wind conditions. The focus of the study was the pickup of soil by a belly scraper at a landfill. Four low-volume PM10 samplers were positioned downwind of the storage pile (at two distances, 80 and 110 m, and two elevations, 1 and 3 m) and one was located upwind at 3 m elevation. Integrating nephelometers, which measure the particulate light scattering coefficient, bsp, were also set up at locations 80 and 110 m downwind of the storage pile. Wind speed and direction were measured on-site. Samples were collected for two periods, one with and one without water being applied. Watering was effective at reducing PM10 emissions at wind speeds up to the maximum 18 m sec-1 observed at the landfill soil pickup operation. Measurement of bsp provided an indication of PM10 concentrations with better time resolution than samplers, but not with sufficient resolution, under the instrumental conditions used, to correlate with wind gusts.     

Chlorpyrifos-methyl dissipation in a small adjacent water body following application to citrus

Chlorpyrifos-methyl use in citrus, vineyards and vegetables is extensive and it has become an essential component of pest control in Southern European regions. The objective of this study was to assess surface water and sediment exposure to chlorpyrifos-methyl (RELDAN 22) under field conditions in a citrus orchard in Sicily (Italy). Pesticide drift loadings were measured in a small surface water body situated 0.5-1.0 m from the edge of the treated field. Measured drift values after the application were between 0.04% and 0.19% of the theoretical applied dose and were highly variable. However, the loadings were lower than those measured by other authors, also lower than predicted by regulatory drift models (95th percentile) typically used for aquatic risk assessment in Europe. Most of the variability occurred due to fluctuating wind speed and direction. In water samples collected in the surface water adjacent to the target field, chlorpyrifos-methyl was detected immediately after application, with concentrations ranging from less than the limit of quantification of the analytical method (0.05 microg/l) to a maximum of 0.08 microg/l. Predicted environmental concentrations in water, using the TOXSWA model, were similar to the measured data when measured drift data from the field experiment were used as inputs.     

Demolition of high-rise public housing increases particulate matter air pollution in communities of high-risk asthmatics

Public housing developments across the United States are being demolished, potentially increasing local concentrations of particulate matter (PM) in communities with high burdens of severe asthma. Little is known about the impact of demolition on local air quality. At three public housing developments in Chicago, IL, PM with an aerodynamic diameter < 10 microm (PM10) and < 2.5 microm were measured before and during high-rise demolition. Additionally, size-selective sampling and real-time monitoring were concurrently performed upwind and downwind of one demolition site. The concentration of particulates attributable to demolition was estimated after accounting for background urban air pollution. Particle microscopy was performed on a small number of samples. Substantial increases of PM10 occurred during demolition, with the magnitude of that increase varying based on sampler distance, wind direction, and averaging time. During structural demolition, local concentrations of PM10 42 m downwind of a demolition site increased 4- to 9-fold above upwind concentrations (6-hr averaging time). After adjusting for background PM10, the presence of dusty conditions was associated with a 74% increase in PM10 100 m downwind of demolition sites (24-hr averaging times). During structural demolition, short-term peaks in real-time PM10 (30-sec averaging time) occasionally exceeded 500 microg/m(3). The median particle size downwind of a demolition site (17.3 microm) was significantly larger than background (3 microm). Specific activities are associated with realtime particulate measures. Microscopy did not identify asbestos or high concentrations of mold spores. In conclusion, individuals living near sites of public housing demolition are at risk for exposure to high particulate concentrations. This increase is characterized by relatively large particles and high short-term peaks in PM concentration.     

Characterization of spatial impact of particles emitted from a cement material production facility on outdoor particle deposition in the surrounding community

The objective of this study was to estimate the contribution of a facility that processes steel production slag into raw material for cement production to local outdoor particle deposition in Camden, NJ. A dry deposition sampler that can house four 37-mm quartz fiber filters was developed and used for the collection of atmospheric particle deposits. Two rounds of particle collection (3-4 weeks each) were conducted in 8-11 locations 200-800 m downwind of the facility. Background samples were concurrently collected in a remote area located -2 km upwind from the facility. In addition, duplicate surface wipe samples were collected side-by-side from each of the 13 locations within the same sampling area during the first deposition sampling period. One composite source material sample was also collected from a pile stored in the facility. Both the bulk of the source material and the < 38 microm fraction subsample were analyzed to obtain the elemental source profile. The particle deposition flux in the study area was higher (24-83 mg/m2 x day) than at the background sites (13-17 mg/m2day). The concentration of Ca, a major element in the cement source production material, was found to exponentially decrease with increasing downwind distance from the facility (P < 0.05). The ratio of Ca/Al, an indicator of Ca enrichment due to anthropogenic sources in a given sample, showed a similar trend. These observations suggest a significant contribution of the facility to the local particle deposition. The contribution of the facility to outdoor deposited particle mass was further estimated by three independent models using the measurements obtained from this study. The estimated contributions to particle deposition in the study area were 1.8-7.4% from the regression analysis of the Ca concentration in particle deposition samples against the distance from the facility, 0-11% from the U.S. Environmental Protection Agency (EPA) Chemical Mass Balance (CMB) source-receptor model, and 7.6-13% from the EPA Industrial Source Complex Short Term (ISCST3) dispersion model using the particle-size-adjusted permit-based emissions estimates.     

Concentration and Size Distribution of Ultrafine Particles Near a Major Highway

Abstract

Motor vehicle emissions usually constitute the most significant source of ultrafine particles (diameter <0.1 μm) in an urban environment, yet little is known about the concentration and size distribution of ultrafine particles in the vicinity of major highways. In the present study, particle number concentration and size distribution in the size range from 6 to 220 nm were measured by a condensation particle counter (CPC) and a scanning mobility particle sizer (SMPS), respectively. Measurements were taken 30, 60, 90, 150, and 300 m downwind, and 300 m upwind, from Interstate 405 at the Los Angeles National Cemetery. At each sampling location, concentrations of CO, black carbon (BC), and particle mass were also measured by a Dasibi CO monitor, an aethalometer, and a DataRam, respectively. The range of average concentration of CO, BC, total particle number, and mass concentration at 30 m was 1.7?2.2 ppm, 3.4?10.0 μg/m³, 1.3?2.0 × 10⁵/cm³, and 30.2?64.6 μ/m³, respectively.

For the conditions of these measurements, relative concentrations of CO, BC, and particle number tracked each other well as distance from the freeway increased. Particle number concentration (6–220 nm) decreased exponentially with downwind distance from the freeway. Data showed that both atmospheric dispersion and coagulation contributed to the rapid decrease in particle number concentration and change in particle size distribution with increasing distance from the freeway. Average traffic flow during the sampling periods was 13,900 vehicles/hr. Ninety-three percent of vehicles were gasoline-powered cars or light trucks. The measured number concentration tracked traffic flow well. Thirty meters downwind from the freeway, three distinct ultrafine modes were observed with geometric mean diameters of 13, 27, and 65 nm. The smallest mode, with a peak concentration of 1.6 × 10⁵/cm³, disappeared at distances greater than 90 m from the freeway. Ultrafine particle number concentration measured 300 m downwind from the freeway was indistinguishable from upwind background concentration. These data may be used to estimate exposure to ultrafine particles in the vicinity of major highways.     

Real-time measurement of outdoor tobacco smoke particles

The current lack of empirical data on outdoor tobacco smoke (OTS) levels impedes OTS exposure and risk assessments. We sought to measure peak and time-averaged OTS concentrations in common outdoor settings near smokers and to explore the determinants of time-varying OTS levels, including the effects of source proximity and wind. Using five types of real-time airborne particle monitoring devices, we obtained more than 8000 min worth of continuous monitoring data, during which there were measurable OTS levels. Measurement intervals ranged from 2 sec to 1 min for the different instruments. We monitored OTS levels during 15 on-site visits to 10 outdoor public places where active cigar and cigarette smokers were present, including parks, sidewalk cafés, and restaurant and pub patios. For three of the visits and during 4 additional days of monitoring outdoors and indoors at a private residence, we controlled smoking activity at precise distances from monitored positions. The overall average OTS respirable particle concentration for the surveys of public places during smoking was approximately 30 microg m(-3). OTS exhibited sharp spikes in particle mass concentration during smoking that sometimes exceeded 1000 microg m(-3) at distances within 0.5 m of the source. Some average concentrations over the duration of a cigarette and within 0.5 m exceeded 200 microg m(-3), with some average downwind levels exceeding 500 microg m(-3). OTS levels in a constant upwind direction from an active cigarette source were nearly zero. OTS levels also approached zero at distances greater than approximately 2 m from a single cigarette. During periods of active smoking, peak and average OTS levels near smokers rivaled indoor tobacco smoke concentrations. However, OTS levels dropped almost instantly after smoking activity ceased. Based on our results, it is possible for OTS to present a nuisance or hazard under certain conditions of wind and smoker proximity.     

A validated 2-D diffusion–advection model for prediction of drift from ground boom sprayers

Correct field drift prediction is a key element in environmental risk assessment of spraying applications. A reduced order drift prediction model based on the diffusion–advection equation is presented. It allows fast assessment of the drift potential of specific ground boom applications under specific environmental wind conditions that obey the logarithmic wind profile. The model was calibrated based on simulations with a validated Computational Fluid Dynamics (CFD) model. Validation of both models against 38 carefully conducted field experiments is successfully performed for distances up to 20 m from the field edge, for spraying on flat pasture land. The reduced order model succeeded in correct drift predictions for different nozzle types, wind velocities, boom heights and spray pressures. It used 4 parameters representing the physical aspects of the drift cloud; the height of the cloud at the field edge, the mass flux crossing the field edge, the settling velocity of the droplets and the turbulence. For the parameter set and range considered, it is demonstrated for the first time that the effect of the droplet diameter distribution of the different nozzle types on the amount of deposition spray drift can be evaluated by a single parameter, i.e., the volume fraction of droplets with a diameter smaller than 191 μm. The reduced order model can be solved more than 4 orders of magnitude faster than the comprehensive CFD model.     

Utilizing vortex behaviour to minimize drift

Abstract

The ULV spray emitted from a TBM flying in a cross wind was mapped by a scanning lidar system. The fate of the spray cloud for 2 min after release from the aircraft was followed as the material was transported downwind of the flight line. Vertical scans at 6 s intervals with 1 m^‐3 resolution provided detailed insight into the entrainment of the spray into the wing‐tip vortices and ultimate release to drift or deposit. Relative concentration, dosage and deposit profiles are presented for this cross‐wind case. Vortex lifetimes were found to be significantly different for the up‐wind and downwind vortices. The majority of the near field deposit was associated with the up‐wind vortex while the drift was linked to the down‐wind vortex.     

Environmental Progress and Problems: A Chemical Industry Perspective

From 1995 to 2004, in Genoa, Italy, daily concentrations of twelve polycyclic aromatic hydrocarbons (PAHs) were measured in particulate phase (PM10), around a coke oven plant in operation from the 1950s and closed in 2002. The study permitted to identify the coke oven as the main PAH source in Genoa, causing constant exceeding of benzo(a)pyrene (BaP) air quality target (1.0 ng/m3) in the urban area till 1,900 meters distance downwind the plant. For this reason the plant was closed. Distance and daily hours downwind the coke plant were the main sources of variability of toxic BaP equivalent (BaPeq) concentrations and equations that best fitted these variables were experimentally obtained. During full plant activity, annual average BaPeq concentrations, measured in the three sampling sites aligned downwind to the summer prevalent winds, were: 85 ng/m3 at 40 m (site 2, industrial area), 13.2 ng/m3 at 300 m (site 3, residential area) and 5.6 ng/m3 at 575 m (site 4, residential area).

Soon after the coke oven's closure (February 2002) BaPeq concentrations (annual average) measured in residential area, decreased drastically: 0.2 ng/m3 at site 3, 0.4 ng/m3 at site 4. Comparing 1998 and 2003 data, BaPeq concentrations decreased 97.6% in site 3 and 92.8% in site 4.

Samples collected at site 3, during the longest downwind conditions, provided a reliable PAH profile of fugitive coke oven emissions. This profile was significantly different from the PAH profile, contemporary found at site 5, near the traffic flow.

This study demonstrates that risk assessment based only on distance of residences from a coke plant can be heavily inaccurate and confirmed that seasonal variability of BaPeq concentrations and high variability of fugitive emissions of PAHs during coke oven activities require at least one year of frequent and constant monitoring (10-15 samples each month).

Implications: Around a coking plant, polycyclic aromatic hydrocarbons (PAHs), concentrations depend mainly on downwind hours and distance. Equations that best fit these variables were experimentally calculated. Fugitive emissions of an old coke oven did not comply with the threshold BAP air concentration proposed by the World Health Organization (WHO), up to 1,900 m distance. The study identified the PAH profile of fugitive emissions of a coke oven, statistically different from the profile of traffic emissions. During its activity, in the Genoa residential area, 575 m away from the plant, 92.8% of found PAHs was due to coke oven emission only.