Concentrations of semi-volatile organic compounds in dissolved and particulate forms in precipitation are related to those measured concurrently in air measured at multiple locations along the tracks ...of several storms. In 14 paired (air and precipitation) samples collected at urban, over-water, and downwind stations around southern Lake Michigan, compound-specific total (gas + particle) precipitation scavenging ratios range from 180 to 8.2 × 107 (fluorene and benzoapyrene, respectively) for PAHs and from 0.5 to 1.1 × 107 for PCBs (PCB26 and PCB194, respectively). Particle scavenging, rather than gas scavenging, is the dominant removal mechanism for both PAHs and PCBs in all samples collected along the urban to over-water transect. Variations in measured total scavenging ratios within the 14 samples are large (from 69 to 1.00 × 106 for ∑-PAHs and from 290 to 88 000 for total ∑-PCBs), with larger variation between samples of differing storms collected at a single location than among samples of the same storm collected along the urban to rural transect. This minimal variance of scavenging ratio during the transport of a storm across multiple locations holds in two of three storms measured at multiple locations along the urban to over-water to rural storm track. This suggests that scavenging mechanisms are largely variable between storms and that the relative importance of each mechanism can occasionally also vary greatly during the progression of the storm from the urban to downwind locations. Furthermore, precipitation scavenging appears to be more variable between storms and generally less variable during progression of a storm down transect, indicating that meteorologic and precipitation characteristics, generally referred to here as storm type, control precipitation scavenging.
Dissolved and gas-phase concentrations of nine polycyclic aromatic hydrocarbons and 46 polychlorinated biphenyl congeners were measured at eight sites on the Chesapeake Bay at four different times of ...the year to estimate net diffusive air−water gas exchange rates. Gaseous PAHs are absorbed into the bay's surface waters during the spring, and lighter compounds revolatilize in the late summer and early fall due to seasonal changes in surface water temperature and atmospheric PAH levels. On an annual basis, the atmosphere is a net source of volatile PAHs to the Chesapeake Bay, and gas absorption may be the largest external source of fluorene and phenanthrene, providing up to three times the combined loadings from wet and dry aerosol deposition and from tributaries. Largest PAH absorptive fluxes occurred in the northern Chesapeake when prevailing winds carried PAH-enriched air from the Baltimore-Washington urban area over the bay. In contrast to PAHs, PCBs volatilize from the Chesapeake Bay throughout the year, with the largest fluxes occurring in September and the smallest fluxes in June. However, higher chlorinated ( − ) homologues are absorbed by bay waters during most of the year. Highest PCB volatilization rates were observed in the northern Chesapeake Bay and near the James River in the southern bay, indicating volatilization offsets PCB loading from the bay's tributaries. Volatilization is the dominant removal process for PCBs from the Chesapeake Bay, removing an estimated 400 kg/year. This value is larger than current external PCB loadings, suggesting that release of PCBs from historically contaminated sediments supports volatilization from the bay.
Concentrations of polycyclic aromatic hydrocarbons (PAHs) were measured on size segregated airborne particulate matter and in the gas phase during 12
h periods in urban Chicago and over southern Lake ...Michigan during July 1994 and January 1995 as part of the atmospheric exchange over lakes and oceans (AEOLOS) project. In the 19 paired gas phase and size segregated particle samples, partition coefficients of polycyclic aromatic hydrocarbons are well correlated with the sub-cooled liquid vapor pressure, (
p
l
0) within an aerosol size class. However, partition coefficients differ systematically according to particle size and aerosol organic carbon content. Approximately 68% of the observed variability in measured PAH partition coefficients is explained by a three dimensional multiple linear regression that includes vapor pressure of the compound of interest, aerosol particle aerodynamic equivalent diameter, aerosol organic carbon content and interaction terms. However, addition of both particle size and the fraction organic carbon terms, while statistically significant, appear to be of minimal importance in improving our ability to model gas/particle partitioning in the atmosphere. The influence of either particle size or fraction organic carbon is nearly as large as the calculated random error in partition coefficients, and suggests that an important factor in predicting gas/particle partitioning has not yet been incorporated in the current model.
The heavily urbanized and industrialized Baltimore Harbor/Patapsco River/Back River system is one of the most highly contaminated regions of the Chesapeake Bay. In June 1996, surficial sediments were ...collected at 80 sites throughout the subestuarine system, including historically undersampled creeks and embayments. The samples were analyzed for a suite of hydrophobic organic contaminants (HOCs) consisting of 32 polycyclic aromatic hydrocarbons (PAHs) and 113 polychlorinated biphenyl (PCB) congeners. Total PAH and total PCB concentrations ranged from 90 to 46,200 and 8 to 2,150 ng/g dry weight, respectively. There was enormous spatial variability in the concentrations of HOCs, which was not well correlated to grain size or organic carbon content, suggesting nonequilibrium partitioning and/or proximity to sources as important factors explaining the observed spatial variability. High concentrations of both classes of HOCs were localized around major urban stormwater runoff discharges. Elevated PAH concentrations were also centered around the Sparrow's Point Industrial Complex, most likely a result of the pyrolysis of coal during the production of steel. All but 1 of the 80 sites exceeded the effects range‐low (ERL) for total PCBs and, of those sites, 40% exceeded the effects range‐medium (ERM), suggesting toxicity to marine benthic organisms would frequently occur. Polychlorinated biphenyl homolog patterns most closely resembled Aroclor 1260 at sites around areas of high concentration of industrial outflows and urban runoff. Conversely, those sites further from suspected municipal and industrial discharges had patterns resembling that of Aroclor 1254. We suggest the heavier chlorinated pattern is indicative of near‐source emissions of PCBs. The lighter chlorinated PCB patterns observed are similar to those found in mainstem Chesapeake Bay sediments and may reflect a more weathered pattern or one derived, in part, from air‐water exchange of gaseous PCBs. Using principal component analysis, differences in PAH signatures were discerned. Higher molecular weight PAHs were enriched in signatures from sediments close to suspected sources (i.e., urban stormwater runoff and steel production complexes) compared to those patterns observed at sites further from outfalls or runoff. Due to varying solubilities and affinities for organic matter of the individual PAHs, partitioning of the heavier weight PAHs may enrich settling particles with high molecular weight PAHs. Lower molecular weight PAHs, having lower affinity for particles, may travel from the source to a greater extent.
Assessing trends of persistent organic pollutants (POPs) in marine mammals is difficult due to age, gender, and metabolism influences on accumulation. To help elucidate these effects in dolphins, POP ...concentrations were determined in the Atlantic white-sided dolphin, Lagenorhynchus acutus, a pelagic delphinid inhabiting North Atlantic waters, and in the rough-toothed dolphin, Steno bredanensis, a pelagic delphinid inhabiting tropical and subtropical waters. The specific objectives of this study were to determine baseline POP concentrations in L. acutus and S. bredanensis blubber samples and to examine the effects of age, gender, and metabolism on POP concentrations in dolphin blubber. Focus was aimed at contaminants of emerging concern, specifically, toxaphene and polybrominated diphenyl ethers (PBDEs). Samples collected from L. acutus (n = 47) stranding events in Massachusetts (1993−2000) and S. bredanensis samples (n = 15) were analyzed for PCBs, toxaphene, and other organic pesticides by gas chromatography/mass spectrometry (GC/MS). Age and gender influences were similar between the two species, with adult females having significantly lower POP concentrations as compared to adult males and juveniles. Mean ∑toxaphene concentrations were highest in juvenile L. acutus, 13.0 (6.7) μg/g wet mass (1 SD), and lowest in adult female S. bredanensis, 1.49 (1.4) μg/g wet mass. ∑PBDE (sum of congeners 47, 99, 100, 153, and 154) concentrations were highest in juvenile L. acutus, 2.41 (1.2) μg/g wet mass, and lowest in adult female S. bredanensis, 0.51 (0.6) μg/g wet mass. POP concentrations did not significantly differ between adult males and juveniles, suggesting metabolism of congeners and/or dilution with growth. PBDE concentrations in juvenile white-sided dolphins were not significantly related to collection year, suggesting that there may be a lag period for higher concentrations to be detected in pelagic marine mammals such as L. acutus or that concentrations have already peaked in this species prior to the first collection in 1993.
Aerosol mass size distributions of elemental carbon (EC) and organic carbon (OC) were measured to determine the extent to which carbon speciations within ambient aerosols differ between urban and ...over-water atmospheres. Samples were collected during twenty-one 12-h periods in urban Chicago and over Lake Michigan during the July 1994 and January 1995 sampling intensives. Total particle bound concentrations (sum of all size fractions) of elemental and organic carbon ranged from 0.15 to 0.96 and from 0.94 to 3.04
g
m
−3, respectively. On average, organic material (OM=1.4×OC) accounts for 18% of the total aerosol mass collected, but ranges from 10% (over-water, winter) to 39% (urban, summer). With regard to individual size fractions, organic matter ranges from 3% (>12
μm over-water, winter) to 49% (0.15–0.45
μm, urban, summer) of the particulate matter mass in the size class. Geometric mean aerodynamic equivalent diameters (GMDs) range from 0.72 to 2.4
μm for suspended particulate matter (
Σ-PM), from 0.52 to 1.4
μm for EC, and from 0.60 to 1.9
μm for OC. Elemental and organic carbon GMDs are larger in the urban atmosphere than over the water during winter, while this trend is not observed in
Σ-PM. Furthermore, geometric standard deviations are larger at the urban location in January for both EC and OC, indicating broader size distributions of both species under winter conditions due to greater quantities of EC and OC in large particles.
Gastroesophageal reflux disease (GERD) is a common medical problem in the United States. As a result, laparoscopic antireflux surgery is a common surgical procedure. At the authors' institution, the ...barium esophagram before and after antireflux surgery is a critical examination in patients with GERD. This article summarizes the authors' examination protocol and describes how the findings are integrated in the care of these patients.
The reported success rate of pneumatic dilation in patients with achalasia varies from 50% to 93%. This wide variability may be due to using symptom relief post-dilation as the only assessment of ...success. There are no studies comparing subjective symptom improvements to objective improvement in esophageal emptying after pneumatic dilation.
Patients with achalasia undergoing pneumatic dilation from 1995 to 1997 were evaluated. Pre- and post-dilation symptoms were recorded using a standardized scoring system. Barium column height was measured 1 min and 5 min after upright ingestion to assess esophageal emptying. Based on percentage of total symptom and barium height improvement post-dilation, patients were grouped according to one of nine outcomes; the association between subjective and objective parameters of improvement was tested.
A total of 37 patients underwent 53 pneumatic dilations. There was a significant association (p < 0.001) between improvement in patient symptoms and barium height. In 38 of 53 (72%) pneumatic dilations, the degree of symptom and barium height improvement was similar. Near complete symptom resolution was reported after 26 dilations. In eight of 26 (31%) patients however, there was < 50% improvement in barium height (group A). Compared with the 16 patients with 91-100% improvement in both symptoms and barium height (group B), forward stepwise regression identified age as the only difference between the two groups, with group A patients being significantly (p = 0.04) older.
Objective assessment of esophageal emptying pre- and post-dilation identifies an important subset of patients with poor esophageal emptying who report near complete symptom resolution. This group may benefit from any early repeat pneumatic dilation.
The Henry's law constants for 26 polychlorinated biphenyl (PCB) congeners were measured using a gas-stripping apparatus at five environmentally relevant temperatures between (4 and 31) °C. The ...Henry's law constants ranged between (0.079 ± 0.003) Pa·m3·mol-1 for 2,2‘,3,3‘,4,4‘,5,6-octachlorobiphenyl (IUPAC congener #195) at 4 °C and (308 ± 29) Pa·m3·mol-1 for 2,2‘,3,3‘,4,5‘,6,6‘-octachlorobiphenyl (IUPAC congener #201) at 31 °C. The temperature dependence of each PCB congener's Henry's law constant was modeled to calculate the enthalpy and entropy of the phase change between the gaseous and dissolved phases. For many PCB congeners, this study reports the first experimentally measured temperature variations of their Henry's law constants. The enthalpies of phase change (ΔH H) ranged between (14.5 ± 3.4) kJ·mol-1 for 2,2‘,4,6,6‘-pentachlorobiphenyl (IUPAC congener #104) and (167 ± 13) kJ·mol-1 for 2,2‘,3,3‘,4,4‘,5,6-octachlorobiphenyl (IUPAC congener #195). These data can be used to predict PCB congener Henry's law values within the experimental temperature range within a relative standard error of less than 10%.
A study was conducted to measure atmospheric concentrations of PAHs and PCBs and estimate their fluxes between air and water in the northern San Francisco Estuary. Ambient air samples were collected ...once every 12 days at a single sampling site in Concord, CA, from June to November 2000, using a modified high-volume air-sampling device equipped with glass fiber filters and polyurethane foam. Concentrations of total PAHs and PCBs ranged from 5.7 to 56 and 0.17 to 0.32 ng/m3, respectively. PAHs and PCBs in the ambient air were predominantly in the vapor phase (83−99%). Gaseous fluxes of PAHs in the estuary showed high seasonal variation, ranging from 110 ng·m-2·day-1 efflux in August to 1050 ng·m-2·day-1 influx in November. Gaseous PCBs showed consistent net volatilization (2.2−24 ng·m-2·day-1) for this period. Particle settling contributed estimated net deposition fluxes of 45−960 ng·m-2·day-1 for PAHs and 0.39−2.1 ng·m-2·day-1 for PCBs. Combining these fluxes, PAHs were either deposited to or lost from the estuary via the atmosphere, depending on the month. In contrast, there consistently was net emission of PCBs from the estuary to the atmosphere.
