Refinery evaluation of optical imaging to locate fugitive emissions

Fugitive emissions account for approximately 50% of total hydrocarbon emissions from process plants. Federal and state regulations aiming at controlling these emissions require refineries and petrochemical plants in the United States to implement a Leak Detection and Repair Program (LDAR). The current regulatory work practice, U.S. Environment Protection Agency Method 21, requires designated components to be monitored individually at regular intervals. The annual costs of these LDAR programs in a typical refinery can exceed US$1,000,000. Previous studies have shown that a majority of controllable fugitive emissions come from a very small fraction of components. The Smart LDAR program aims to find cost-effective methods to monitor and reduce emissions from these large leakers. Optical gas imaging has been identified as one such technology that can help achieve this objective. This paper discusses a refinery evaluation of an instrument based on backscatter absorption gas imaging technology. This portable camera allows an operator to scan components more quickly and image gas leaks in real time. During the evaluation, the instrument was able to identify leaking components that were the source of 97% of the total mass emissions from leaks detected. More than 27,000 components were monitored. This was achieved in far less time than it would have taken using Method 21. In addition, the instrument was able to find leaks from components that are not required to be monitored by the current LDAR regulations. The technology principles and the parameters that affect instrument performance are also discussed in the paper.     

Patterns of drinking four weeks prior to an alcohol-related vehicular crash

OBJECTIVE: The primary objective of the study was to determine if drinking patterns on the days immediately prior to an alcohol-related motor vehicle crash (ARMVC) were significantly different than drinking patterns in the weeks prior to the crash. METHODS: Following ARMVC, 187 hospitalized non-alcohol dependent young-adults (43 females, 144 males) were enrolled. Mean age was 29.03 years, mean blood alcohol level was 165.18 mg/dL, and mean injury severity score was 10.50. When alcohol-free, subjects were interviewed by nurse clinicians to determine the quantity/frequency of alcohol consumption during the 28 days prior to the crash. Subjects reported the number of standard drinks using the Timeline Followback procedure. Total drinks/day were determined, with day 1 considered 4 weeks prior to the crash and day 28 the day of the crash. A random-intercepts general linear mixed model (GLMM) was used to test the effect of several covariates (segment 1 [days 1-26], segment 2 [days 27-28], age, sex, race, holiday/non-holiday period, driver/passenger status, and weekend/weekday crash) on the amount of standard drinks/day. RESULTS: There was no significant interaction among the covariates. The only significant predictors of drinks/day were segment 2 (b = .322, p < .0001) and gender (b = -.221, p = .016). The positive, statistically significant slope for segment 2 indicated an increase in consumption of drinks/day in the two-day period prior to the ARMVC and the negative slope for gender indicated greater consumption of drinks/day for men than women. CONCLUSION: Persons injured in an ARMVC had a significant increase in alcohol consumption on the day before and the day of vehicular crashes (days 27 and 28) as compared to the first 26 days in the 28-day period preceding the crash. When non-alcohol-dependent subjects are counseled to reduce their risk of traffic crashes, they should be alerted that when their patterns of drinking change, they are at higher risk than usual for a crash.     

Identifying Reference Conditions and Quantifying Biological Variability Within Benthic Macroinvertebrate Communities in Perennial and Non-perennial Northern California Streams

Identification of minimally disturbed reference sites is a critical step in developing precise and informative ecological indicators. We tested procedures to select reference sites, and quantified natural variation (inter-site and -annual variability) among reference conditions using a macroinvertebrate data set collected from 429 mediterranean-climate stream reaches in the San Francisco Bay Area, California (USA). We determined that a landscape GIS-based stressor screen followed by a local field-based stressor screen effectively identified least-disturbed reference sites that, based on NMS ordination results, supported different biological communities than sites identified with only landscape (GIS) or local (field) stressors. An examination of least-disturbed reference sites indicated that inter-site variability was strongly associated with stream hydrology (i.e., perennial vs. non-perennial flow) and annual precipitation, which highlights the need to control for such variation when developing biological indicators through natural gradient modeling or using unique biological indicators for both non-perennial and perennial streams. Metrics were more variable among non-perennial streams, indicating that additional modeling may be needed to develop precise biological indicators for non-perennial streams. Among 192 sites sampled two to six times over the 8-year study period, the biological community showed moderate inter-annual variability, with the 100 point index of biotic integrity scores varying from 0 to 51 points (mean = 11.5). Variance components analysis indicated that inter-annual variability explained only a fraction (5–18 %) of the total variation when compared against site-level variation; thus efforts to understand causes of natural variation between sites will produce more precise and accurate biological indicators.     

Availability of phosphorus to algae from eroded soil fractions

A study was conducted to determine the concentrations of algal-available P (P_aa) in unfractionated samples and size-classified separates of soil eroded from wheat stubble plots during a simulated rainfall experiment conducted in Warren County, Indiana, U.S.A. Run-off samples were collected, concentrated, dispersed by sonification, separated according to size and incubated with algal cells (Selanastrum capricornutum) in P-free nutrient medium for 2 weeks. Algal-available P in soil separates was determined by decreases in sediment inorganic P (P_i) over the incubation period. The initial concentrations of dissolved molybdate-reactive P_i (DMRP), P_i extractable with NaOH (NaOH-P_i), P_i extractable with HCl (HCl-P_i), organic P (P_o, and total P increased with decreasing particle size. A higher proportion of P_i was HCl-extractable in fractions > 2 μm than in clay-size separates. The level of P_aa in samples increased with decreasing particle size. Available P concentrations in separates < 0.2, 0.2–2, 2–50, > 50 μm and unfractionated samples averaged 447, 282, 113, 26 and 261 μg g^?1, respectively. From 42 to 69% of the P_i and 20–37% of the total P in unfractioned samples was P_aa. A lower proportion of P_i in the > 50 μm fraction was P_aa than in the other size fractions (34 vs. 50%). There was no relationship between particle size and the proportion of total P that was available. The majority (> 84%) of P_aa originated in the P_i fraction extractable with NaOH, whereas HCl-P_i only contributed small amounts of P_aa. The proportion of initial NaOH-P_i assimilated by algae in 2 weeks ranged between 43 and 77%, whereas an average of 16% of HCl-P_i in separates was P_aa. On average, a greater proportion of NaOH-P_i was assimilated by algae in samples from no-till plots as compared to those from chisel-plowed plots.