Charles L. Wax

Dry weather induces outbreaks of human West Nile virus infections

BackgroundSince its first occurrence in the New York City area during 1999, West Nile virus (WNV) has spread rapidly across North America and has become a major public health concern in North America. By 2002, WNV was reported in 40 states and the District of Columbia with 4,156 human and 14,539 equine cases of infection. Mississippi had the highest human incidence rate of WNV during the 2002 epidemic in the United States. Epidemics of WNV can impose enormous impacts on local economies. Therefore, it is advantageous to predict human WNV risks for cost-effective controls of the disease and optimal allocations of limited resources. Understanding relationships between precipitation and WNV transmission is crucial for predicting the risk of the human WNV disease outbreaks under predicted global climate change scenarios.MethodsWe analyzed data on the human WNV incidences in the 82 counties of Mississippi in 2002, using standard morbidity ratio (SMR) and Bayesian hierarchical models, to determine relationships between precipitation and human WNV risks. We also entertained spatial autocorrelations of human WNV risks with conditional autocorrelative (CAR) models, implemented in WinBUGS 1.4.3.ResultsWe observed an inverse relationship between county-level human WNV incidence risk and total annual rainfall during the previous year. Parameters representing spatial heterogeneity in the risk of human exposure to WNV improved model fit. Annual precipitation of the previous year was a predictor of spatial variation of WNV risk.ConclusionsOur results have broad implications for risk assessment of WNV and forecasting WNV outbreaks. Assessing risk of vector-born infectious diseases will require understanding of complex ecological relationships. Based on the climatologically characteristic drought occurrence in the past and on climate model predictions for climate change and potentially greater drought occurrence in the future, we suggest that the frequency and relative risk of WNV outbreaks could increase.

Effects of water management practices on discharge of nutrients and organic matter from channel catfish (Ictalurus punctatus) ponds

Abstract A water quality data set generated by sampling commercial ponds for 2 years was used in a hydrological model of pond overflow volume to describe the effects of water management practices on discharge of nutrients and organic matter from channel catfish Ictalurus punctatus ponds in northwest Mississippi, USA. Average concentrations of total nitrogen, total phosphorus, chemical oxygen demand, and biochemical oxygen demand in pond waters were highest in the summer but waste discharge was strongly influenced by pond overflow volume, and the model indicated that greatest quantities of nutrients and organic matter were discharged in the winter when pond overflow volume was greatest. The model also showed that managing pond water levels to maintain a minimum 7.5-cm water storage potential reduced average discharge of nitrogen, phosphorus, and organic matter in pond overflow by about 70% compared with ponds not managed to maintain storage potential. The model further showed that harvesting fish without draining ponds between fish crops could reduce average annual nutrient and organic matter discharge by over 60% relative to annually drained ponds. Maintaining water storage potential and not draining ponds between fish crops therefore appear to be simple and effective methods of reducing waste discharge from aquaculture ponds and have the added benefit of substantially reducing the need for pumped water to maintain pond water levels.

Temperature as an Indicator of Landform Influence on Atmospheric Processes

Potential land surface-atmosphere interactions were observed on satellite imagery in the lower reaches of the alluvial valley of the Mississippi River. Monthly temperature data were used to determine if a measurable relationship between the land surface and resulting atmospheric processes can be similarly found in the long-term record throughout the entire year. Comparison of temperatures inside the valley with those outside the valley revealed that annual average minimum temperature in the valley is warmer by 1°C than outside the valley. Analyses of seasonal temperature showed that average maximum temperature in the valley is warmer by 0.5°C in summer and colder by 0.5°C in winter. Average minimum temperature in the valley is consistently over 1°C warmer in all seasons. Monthly temperature analyses showed that average maximum temperature in the valley is colder from November-March and warmer from May-October, while average minimum temperature is consistently warmer in the valley in all months. Average temperature range in the valley is consistently smaller than outside the valley. Statistically significant results indicate that days are hotter in summer and colder in winter, and that nights are warmer all year in the valley. Soil type differences and consequently differing soil moisture regimes are suggested as possible causal mechanisms.

Optimizing Online Content Instruction for Effective Hybrid Teacher Professional Development Programs

ABSTRACT The Teacher Academy in the Natural Sciences (TANS) provided middle school (U.S. Grades 6–8) teachers (N = 81) with intensive professional development in chemistry, geosciences, and physics through 13 days of face-to-face instruction that was extended with 2 online science modules per discipline. Because we administered online module assessments before the summer academy (pretest), after the summer academy (Post 1), and after the online module was assigned (Post 2), we were able to analyze via dependent t tests the learning components contributed by the online module. Only 1 geosciences module resulted in significant gains after it was assigned. Other modules (2 physics, 1 geosciences) resulted in gains before module assignments, at the end of the 10-day summer academy. Although the 2 chemistry modules exhibited positive score increases, no significant gains were made. Calculated Pearson correlation coefficients revealed no association between participants’ online access times and science content gains. This research documents benefits of hybrid teacher professional development programs and offers recommendations for their optimized effectiveness, including more consistent instructor/participant online access.

Climatic criteria for land application of municipal wastewater effluent

Abstract Climatic characteristics of the coastal region require design considerations for land application systems that have been largely ignored or the bases for which have been unavailable. For example, the amount of effluent flow in a land application system increases when precipitation occurs, while at the same time the net water requirement of plants decreases. Therefore extra storage and extra land acreage is needed, but the amount required has not been established. Additionally, frequent rainfall coupled with high humidity creates an evaporation regime in the coastal region that inhibits the efficiency and viability of the land application disposal method. The bases of these problems are climatological; therefore, this study uses a climatological analysis to provide design considerations regarding the capability of this disposal method in the coastal region. The availability of long-term digitized daily weather data offers the opportunity to test the design of such systems by simulating multiple years of operation. Simulation using 30 years of weather data for a 3800 m 3 /d (1 mgd) plant in the southeastern coastal region of the United States shows that the best design requires a 256 ha (640 A) application field and a 16 ha (40 A) storage pond 3.7 m (12 ft) deep. These specifications provide system success ranging from 99% in 6 months of the year to 90% in March and prevent any failures in 90% of the years.