Laboratory and field evaluation of real-time and near real-time PM2.5 smoke monitors

ABSTRACT

Increases in large wildfire frequency and intensity and a longer fire season in the western United States are resulting in a significant increase in air pollution, including concentrations of PM_2.5 (particulate matter <2.5 µm in aerodynamic diameter) that pose significant health risks to nearby communities. During wildfires, government agencies monitor PM_2.5 mass concentrations providing information and actions needed to protect affected communities; this requires continuously measuring instruments. This study assessed the performance of seven candidate instruments: (1) Met One Environmental beta attenuation monitor (EBAM), (2) Met One ES model 642 (ES642), (3) Grimm Environmental Dust Monitor 164 (EDM), (4) Thermo ADR 1500 (ADR), (5) TSI DRX model 8543 (DRX), (6) Dylos 1700 (Dylos), and (7) Purple Air II (PA-II) in comparison with a BAM 1020 (BAM) reference instrument. With the exception of the EBAM, all candidates use light scattering to determine PM_2.5 mass concentrations. Our comparison study included environmental chamber and field components, with two of each candidate instrument operating next to the reference instrument. The chamber component involved 6 days of comparisons for biomass combustion emissions. The field component involved operating all instruments in an air monitoring station for 39.5 days with hourly average relative humidity (RH) ranging from 19% to 98%. Goals were to assess instrument precision and accuracy and effects of RH, elemental carbon (EC), and organic carbon (OC) concentrations. All replicate candidate instruments showed high hourly correlations (R² ≥ 0.80) and higher daily average correlations (R² ≥ 0.90), where all instruments correlated well (R² ≥ 0.80) with the reference. The DRX and Purple Air overestimated PM_2.5 mass concentrations by a factor of ~two. Differences between candidates and reference were more pronounced at higher PM_2.5 concentrations. All optical instruments were affected by high RH and by the EC/OC ratio. Equations to convert candidate instruments data to FEM BAM type data are provided to enhance the usability of data from candidate instruments.

Implications: This study tested the performance of seven candidate PM_2.5 mass concentration measuring instruments in two settings - environmental chamber and field. The instruments were tested to determine their suitability for use during biomass combustion events and the effects of RH, PM mass concentrations, and concentrations of EC and OC on their performance. The accuracy and precision of each monitor and effect of RH, PM concentration, EC and OC concentrations are varied. The data show that most of these candidate instruments are suitable for measuring PM_2.5 concentration during biomass combustions with a proper correction factor for each instrument type.     

Estimating the elasticity of substitution between restricted and unrestricted inputs in a regulated fishery: A probit approach

Catch, effort, vessel, and skipper characteristic data for a sample of boats involved in the Tasmanian rock lobster fishery in the 1983/1984 season are used to estimate a fishing effort production function nested in a Cobb-Douglas fishery production function. The initial effort function is translog but tests suggest that the CES form cannot be rejected. The vessel's choice of fishing ground is modeled by a probit equation, the output from which is included in the OLS estimation of the production function. The elasticity of substitution between the inputs which are restricted by regulation and the other inputs is of particular interest as it determines whether input restriction is an efficient form of regulation for the fishery. The results suggest a value significantly less than unity.     

Normal fetal cardiac anatomy–a basis for the echocardiographic detection of abnormalities

Real-time examination of the fetal heart in 350 pregnancies has allowed a composite picture of normal fetal cardiac anatomy to be established and echocardiographic interpretation has been confirmed by anatomical studies. Two echocardiographic sections are readily obtainable and are suggested as applicable to routine scanning but the specialist nature of interpreting abnormalities is stressed. Six abnormalities have been suspected during the study and five confirmed anatomically or at cardiac catheterization. In view of the low incidence of congenital heart disease in a normal obstetric population, high risk groups should perhaps be selected for cardiac scanning at the present time. These include mothers of previously affected babies, diabetic mothers and certain abnormalities of pregnancy. Fetal ascites is particularly important, being present in three of the four proven cases of cardiac abnormality.     

First-trimester amniotic fluid and extraembryonic coelomic fluid acetylcholinesterase electrophoresis

Acetylcholinesterase (AChE) gel electrophoresis was performed on samples of amniotic fluid and extraembryonic coelomic fluid obtained by high resolution transvaginal ultrasound-guided amniocentesis from 38 women between 8 and 12 weeks of pregnancy. AChE was positive in 33 per cent (12/36) of the amniotic fluid samples; the percentage of positive results decreased as gestation advanced. AChE was positive in 32 per cent (9/28) of the extraembryonic coelomic fluid samples. In 81 per cent (21/26) of matched samples, the AChE results were identical in the two fluids. Amniotic fluid and extraembryonic coelomic fluid AChE electrophoresis cannot be used to diagnose neural tube defects prior to 12 weeks of gestation.     

Early sonographic diagnosis of body stalk anomaly

Ultrasonographic features of a fetus at 18 weeks of gestation suggesting a body stalk anomaly are presented. These included a large abdominal anterior wall defect in apparent continuity with the placenta, severe kyphoscoliosis of the lower spine, the absence of one kidney, and a very short umbilical cord with only one umbilical artery. The amniotic fluid was reduced and the fetus was almost immobile at short-interval ultrasound examinations. The pregnancy was terminated and autopsy of the fetus showed abnormalities compatible with maldevelopment of both cephalic and caudal embryonic folds.     

Measurement of the fetal mandible—feasibility and construction of a centile chart

The prenatal diagnosis of micrognathia is usually based on a subjective impression of the size of the jaw when examining the fetal profile. We have constructed a centile chart for mandibular length between 12 and 27 post-menstrual weeks in a cross-sectional study of 184 fetuses. The application of this chart in clinical practice may permit a more objective diagnosis of micrognathia in the prenatal period.     

Seasonal cycles in the carotenoid content in Mytilus edulis

The carotenoid content of Mytilus edulis was studied over a period of 3 years from 1965 to 1967; a seasonal cycle was observed which appeared to be controlled by the spring bloom of phytoplankton, and the sexual cycle of the mussel. Infestation by the copepod Mytilicola intestinalis and hours of exposure in the tidal cycle were found to contribute to variations in carotenoid content. Maturation of the gonads and spawning occurred in the late spring and early summer of the period studied. In addition, a second sexual phase was recorded in October 1967. The possible effect of exposure on the time of spawning is discussed. Lack of food affects both carotenoid content and the maturation of the gonads. M. edulis kept at 10 °C with little food showed no seasonal variation in the carotenoid content when compared with animals fresh from the shore. Lack of food resulted in regression in gonadal tissue after a period of time, and an absence of mature and spawning individuals.     

Lethal levels of hypoxia for gulf coast estuarine animals

There is increasing concern about eutrophication and subsequent hypoxia problems in estuaries. The US Environmental Protection Agency has developed Water Quality Criteria (WQC) for dissolved oxygen (DO) in saltwater for Cape Cod, MA to Cape Hatteras, NC but inadequate data exists for development of such criteria for other coastal geographic areas. We performed acute tests with two species of crustaceans and seven species of estuarine fishes native to the Gulf of Mexico to complement the data base for northeastern species. Flow-through tests were conducted for either 24- or 48-h at test temperatures from 24 to 28°C and at salinities from 20 to 31.5‰. Estimated 24-h LC50 values obtained for crustaceans ranged from 1.36 mg/l for adult pink shrimp to 1.56 mg/l for 10-day-old mysids. Similarly, estimated LC50 values for fish ranged from 1.34 mg/l in one of the three tests with pinfish to 2.22 mg/l in one of the two tests with scaled sardines. The majority of mortality attributable to low DO concentrations in our experiments usually occurred within the first 4 h of exposure. LC50 values for the species tested are below the WQC recommended protective limit of 2.3 mg/l for juvenile and adult animals.