Bacillus anthracis Aerosolization Associated with a Contaminated Mail Sorting Machine

On October 12, 2001, two envelopes containing Bacillus anthracis spores passed through a sorting machine in a postal facility in Washington, D.C. When anthrax infection was identified in postal workers 9 days later, the facility was closed. To determine if exposure to airborne B. anthracis spores continued to occur, we performed air sampling around the contaminated sorter. One CFU of B. anthracis was isolated from 990 L of air sampled before the machine was activated. Six CFUs were isolated during machine activation and processing of clean dummy mail. These data indicate that an employee working near this machine might inhale approximately 30 B. anthracis-containing particles during an 8-h work shift. What risk this may have represented to postal workers is not known, but the risk is approximately 20-fold less than estimates of sub-5 micron B. anthracis-containing particles routinely inhaled by asymptomatic, unvaccinated workers in a goat-hair mill

Swell impact on reef sedimentary processes: A case study of the La Reunion fringing reef

Two surface-sediment sampling campaigns were carried out in November and December 2003, before and after a strong swell event, in the back-reef area of a microtidal fringing reef on the western coast of La Reunion, Indian Ocean. The spatial distributions of the mean grain size, sorting and skewness parameters are determined, and grain-size trend analysis is performed to estimate the main sediment transport pathways in the reef. The results of this analysis are compared with hydrodynamic records obtained in the same reef area during fair weather conditions and during swell events. Sediment dynamics inferred from the hydrodynamic records show that significant sediment erosion and transport occur only during swell events and under strongly agitated sea states. Under normal wave conditions, there is a potential for onshore sediment transport from the reef-flat to the back-reef, but this transport is episodic and occurs principally during high-tide stages. Sediment transport trends revealed by the grain-size trend analysis method show onshore and alongshore low-energy transport processes that are in agreement with the hydrodynamic records. The grain-size trend analysis method also provides evidence of an offshore high-energy transport trend that could be interpreted as a real physical process associated with return flow from the shore to the reef. The impact of swell on the reef sediment dynamics is clearly demonstrated by onshore and alongshore transport. Considering different combinations of the vector transport trends computed through the grain-size trend analysis approach, more realistic and pertinent results can be obtained by applying an exclusive OR operation (XOR case) on the vectors. The main results presented here highlight a trend towards the accumulation of carbonate sands in the back-reef area of the fringing reef. These sediments can only be resuspended during extreme events such as storms or tropical cyclones

Evaluating Cover Crops (Sudex, Sunn Hemp, Oats) for Use as Vegetative Filters to Control Sediment and Nutrient Loading From Agricultural Runoff in a Hawaiian Watershed

A study was conducted to determine the effects of three land covers (sunn hemp -Crotalaria juncea, sudex, a sorghum-sudangrass hybrid -Sorghum bicolor x S. bicolor var. sudanese, and common oats -Avena sativa) planted as vegetative filter strips on the reduction of sediment and nutrient loading of surface runoff within the Kaika-Waialua watershed on the island of Oahu, Hawaii. Runoff samples were collected and analyzed for total suspended solids (TSS), total dissolved solids (TDS), phosphorous, and three forms of nitrogen (nitrate, ammonium, total nitrogen). Study results show that during seven out of 10 runoff events, the three cover crop treatments significantly reduced TSS as compared to the fallow treatment. Average removal efficiencies were 85, 77, and 73% for oats, sunn hemp, and sudex, respectively, as compared to the fallow treatment. Nutrient concentrations were low with phosphorous concentrations, lower than 1 (μg/ml) for all treatments, and total nitrogen (TN) concentrations below 7 (μg/ml) except in the sunn hemp treatment, where TN concentrations were less than 10 (μg/ml). Results of analysis of TDS showed that the cover crop treatments did not decrease dissolved solids concentrations in comparison with the fallow treatment. Analysis of nutrient concentrations in runoff samples did not detect any significant decreases in phosphorous, nitrogen, ammonium, or TN concentrations in comparison to the fallow treatment. However, a significant increase in TN concentrations in the sunn hemp treatment was detected and showed the nitrogen fixing capacity of sunn hemp. No treatment effects on runoff volume were detected, and runoff volumes were directly correlated with rainfall amounts showing no crops significantly impacted soil infiltration rates. These results were attributed to extremely low soil hydraulic conductivities (0.0001-7 cm/day at the soil surface, 15 and 30 cm below the soil surface). This study showed that cover crops planted as vegetative filters can effectively reduce sediment loads coming from idle and fallow fields on moderately steep volcanically derived highly weathered soils. © 2008 American Water Resources Association