A SELF-VERIFYING HYBRID COMPUTER MODEL OF RIVER-BASIN HYDROLOGY1

ABSTRACT. As demands upon available water supplies increase, there is an accompanying increase in the need to assess the downstream consequences resulting from changes at specific locations within a hydrologic system. The problem is approached in this study by hybrid computer simulation of the hydrologic system. Modeling concepts are based upon the development of basic relationships which describe the various hydrologic processes. Within a system these relationships are linked by the continuity-of-mass principle. Spatial resolution is achieved by considering the modeled areas as a series of subbasins. The time increment adopted for the model is one month, so that time varying quantities are expressed in terms of mean monthly values. The model is general in nature and is applied to a particular hydrologic system through a programmed verification procedure whereby model coefficients are evaluated for the particular system. In this study the model is applied to the Bear River basin of western Wyoming, southern Idaho, and northern Utah. Comparisons between observed and computed outflow hydrographs show good agreement. The utility of the model is demonstrated by predicting the effects of various possible water resource management alternatives. The verified hybrid computer program can be digitized for application to the digital computer.     

Methane emissions of rice increased by elevated carbon dioxide and temperature

Methane (CH4) effluxes by paddy-culture rice (Oryza sativa L.) contribute about 16% of the total anthropogenic emissions. Since radiative forcing of CH4 at current atmospheric concentrations is 21 times greater on a per mole basis than that of carbon dioxide (CO2), it is imperative that the impact of global change on rice CH4 emissions be evaluated. Rice (cv. IR72) was planted in sunlit, closed-circulation, controlled-environment chambers in which CH4 efflux densities were measured daily. The CO2 concentration was maintained at either 330 or 660 micromol mol(-1). Air temperatures were controlled to daily maxima and minima of 32/23, 35/26, and 38/29 degrees C at each CO2 treatment. Emissions of CH4 each day were determined during a 4-h period after venting and resealing the chambers at 0800 h. Diurnal CH4 effluxes on 77, 98, and 119 d after planting (DAP) were obtained similarly at 4-h intervals. Emissions over four-plant hills and over flooded bare soil were measured at 53, 63, and 100 DAP. Emissions were negligible before 40 DAP. Thereafter, emissions were observed first in high-CO2, high-temperature treatments and reached a sustained maximum efflux density of about 7 mg m(-2) h(-1) (0.17 g m(-2) d(-1)) near the end of the growing season. Total seasonal CH4 emission was fourfold greater for high-CO2, high-temperature treatments than for the low-CO2, low-temperature treatment, probably due to more root sloughing or exudates, since about sixfold more acetate was found in the soil at 71 DAP. Both rising CO2 and increasing temperatures could lead to a positive feedback on global warming by increasing the emissions of CH4 from rice.     

Recovery of Francisella tularensis from soil samples by filtration and detection by real-time PCR and cELISA

The aim of this study was to develop a specific and highly sensitive method able to detect very low concentrations of Francisella tularensis in soil samples by real-time PCR (qPCR) with SYBR Green I. tul4 gene, which encodes the 17-kDa protein (TUL4) in F. tularensis strains, was amplified using a LightCycler (LC) device. We achieved a detection limit of 0.69 fg of genomic DNA from F. tularensis subp. holarctica live vaccine strain (LVS), corresponding to a value less than 3.4 genome equivalents per reaction. The qPCR was shown to be specific, highly sensitive and reproducible. In addition, we evaluated 2 new methods for recovering bacteria from soil based on 1-step filtration using glass fiber filters and PVDF filters. These filtration methods enabled us to recover F. tularensis efficiently from soil samples. As few as 50 CFU per 0.5 g of soil were detected by qPCR. Capture enzyme-linked immunosorbent assay (cELISA) allowed us to detect and quantify the amount of bacteria recovered from soil by an immunological method. Although qPCR was more sensitive than cELISA, we did not observe substantial differences in the amount of bacteria quantified by both methods.     

Air Pollution Patterns In New York City

Some preliminary analyses of data selected from three years of smoke shade and sulfur dioxide measurements from the forty air monitoring stations in New York City are presented. The purpose of these analyses is to investigate the spatial-temporal variation in concentration of these pollutants throughout the five boroughs of the city. Air pollution health effects studies in New York City have often used city-wide daily morbidity or mortality statistics and related them to air pollution levels obtained from a single monitoring station. The question of whether readings at one station in New York City can adequately represent the air pollution exposure for the population in the five boroughs is examined in this paper. Some samples of correlation matrices of daily pollution averages obtained from the forty air monitoring stations are presented to illustrate the day-to-day variation in pollution in various sections of New York City. It was found that interstation correlations are not high enough to justify the use of one central pollution measuring station as representative of a large metropolitan area. Sulfur dioxide correlates better between stations than smoke shade; this may reflect the different nature and spatial distribution of sources of the two pollutants. Close proximity of stations, or the fact that they were at similar heights above street or sea level did not necessarily lead to higher correlation coefficients.     

The Effect of California’s Wintertime Oxygenated Fuels Program on Ambient Carbon Monoxide Concentrations

Abstract

The U.S. Environmental Protection Agency (EPA) mandated the use of oxygenated gasoline beginning in the winter of 1992 to reduce the unhealthful carbon monoxide concentrations in many urban areas. The California Air Resources Board (CARB), weighing the potential effects of the program on other pollutants, implemented a modified version of the federal wintertime oxygenated fuels program. In California, the number of violations of the carbon monoxide air quality standard during the three winters associated with the program was dramatically lower than during any winter prior to the program. Because meteorological conditions during the program were very favorable for dispersion of pollutants, any analysis of the impacts of the program must account for the influence of variable meteorological conditions. Analyses of ambient pollutant concentrations suggest that most of the air quality improvement was due to increased atmospheric dispersion. The analyses presented here account for the large influence of meteorology on ambient concentrations and indicate that California’s modified oxygenated fuels program was responsible for an approximately 5–10% reduction in mean ambient carbon monoxide concentrations, depending on the statistical approach used.     

Sperm competition and the level of polyandry in a bushcricket with large nuptial gifts

Variation in paternity due to sperm competition or post-copulatory female choice has a major influence on animal mating system evolution and on the levels of genetic variability in natural populations. However, there are relatively few studies comparing the outcome of sperm-competition experiments in the laboratory with natural variation in polyandry among families from the field. In the bushcricket Ephippiger ephippiger, females mate multiply, and the males provide them with a large, nutritious, and probably expensive, donation at mating. We examined paternity in a series of laboratory matings, where females mated with two males, and amongst a series of families collected from a natural population. In the laboratory, paternity was highly bimodally distributed: 24% of families had offspring fathered by the first male to mate, 68% by the second male (in only 8% was paternity shared). In the field, paternity was more mixed: only 27% of families had a single father, 14% had more than two fathers, whilst 59% had two fathers. While unsuccessful matings may contribute to the highly biased paternity in the laboratory, they cannot fully explain the high incidence of complete P2 families. Nonrandom sperm utilisation is therefore likely. Greater sperm mixing in the field probably results from females mating with more males, but the distribution of paternity also reflects an active process of nonrandom sperm utilisation. Confidence of paternity due to last male advantage may be relatively high in this species, and therefore may have facilitated the evolution of the large spermatophore in E. ephippiger.Communicated by D. Gwynne     

The effects of current water management practices on methane emissions in Japanese rice cultivation

Cultivated wetland rice fields are a source of methane (CH₄) emissions. To estimate CH₄ emissions and develop policies to reduce such emissions, information on water management at the farm level is crucial. It is known that farmers implement midseason drainage (MD) to increase rice yields and save water. However, little is known about whether MD is carried out in soils where CH₄ emissions are high and how part-time status will influence management. The objective of this study is to identify factors that determine MD implementation using a binomial logistic regression model based on a farm-level survey in Japan and to indicate possible changes in estimates of CH₄ emissions, accounting for current water management practices. The implementation rates were significantly higher where the soil types were classified as having the potential for high CH₄ emissions. Under current water management practices, the duration of MD and the percentage of continuous flooding were 5 to 7 days longer and approximately 7 % higher, respectively, than the values used by the Greenhouse Gas Inventory Office of Japan, which in turn are used to report greenhouse gas emissions to the United Nations Framework Convention on Climate Change. By accounting for current water conditions with the Tier 2 method, this study indicates that national estimates of CH₄ emissions from rice straw application areas could be lowered by 12.7 %. These results may contribute to the development of a mitigation policy that will help to further reduce CH₄ emissions.     

“Community in Bloom”: local participation of community gardens in urban Singapore

Community gardens offer a space that allows facilitation of leisure activities, encourages interaction within different factions in a community and helps forge a sense of belonging towards the overall community. Using the case study of “Community in Bloom” (CIB) programme initiated by the National Parks Board of Singapore, this article highlights how such community gardens are also viewed by some as exclusionary spaces due to their close links with government apparatus. More broadly, it argues that a constrained civic activism not only affects the extent to which these gardens can forge communal bonds, but they also challenge their integral spirit. Despite promising signs of politically opening up in the early 2000s, the soft authoritarianism of the Singaporean state continues to be wary of non-governmental sanctioned community projects and civic activism. This attitude may prove to be resilient in the foreseeable future, thereby preventing the “CIB” programme from truly blossoming.     

Electrochemical removal of metal ions from aqueous solution: a student workshop

An environmental electrochemistry workshop program on metal ion removal is described. The program was designed for undergraduate students in chemistry, chemical engineering or environmental science and teaches environmental electrochemistry through a combination of hands-on experiments, understanding of research concepts, completion of project reports and in class discussion. The students are encouraged to quantitatively describe the performance of the electrochemical cells (containing 2-D and 3-D carbon cathodes) and to consider the advantages and shortcomings of electrochemical routes to environmental treatment.