IMPROVED RAINFALL/RUNOFF ESTIMATES USING REMOTELY SENSED SOIL MOISTURE1

ABSTRACT: Remotely sensed soil moisture data measured during the Southern Great Plains 1997 (SGP97) experiment in Oklahoma were used to characterize antecedent soil moisture conditions for the Soil Conservation Service (SCS) curve number method. The precipitation‐adjusted curve number and the soil moisture were strongly related (r²= 0.70). Remotely sensed soil moisture fields were used to adjust the curve numbers and the runoff estimates for five watersheds, in the Little Washita watershed; the results ranged from 2.8 km² to 601.6 km². The soil moisture data were applied at two spatial scales, a finer one (800 m) measuring spatial resolution and a coarser one (28 km). The root mean square error (RMSE) and the mean absolute error (MAE) of the runoff estimated by the standard SCS method was reduced by nearly 50 percent when the 800 m soil moisture data were used to adjust the curve number. The coarser scale soil moisture data also significantly reduced the error in the runoff predictions with 41 percent and 28 percent reductions in MAE and RMSE, respectively. The results suggest that remote sensing of soil moisture, when combined with the SCS method, can improve rainfall runoff predictions at a range of spatial scales.     

Greening government procurement in developing countries: building capacity in China

With increasing environmental issues and depleting resources, the effective application of green government procurement (GGP) is urgently needed and potentially can have greater impacts in the developing world rather than in the developed world. Such an approach can help promote the general goal of sustainable development and address environmental issues through purchasing and facilitating the use of environmentally friendly services and products. This paper addresses this issue by employing a case study on China. We first trace the development of the GGP concept, its spread to Asian countries, and a number of approaches used to expand GGP adoption. We then review current practices in China on GGP, and analyze and identify some of the current barriers and problems in promoting green procurement in the Chinese governmental sector. We finally seek to identify possible appropriate capacity-building solutions, in order to facilitate the application of GGP in China.     

The water footprint of hydroelectricity: a methodological comparison from a case study in New Zealand

Hydroelectricity has been rated to have a large water footprint (WF) on global average. We assessed the WF of hydroelectricity by three different methods using New Zealand as a case study. The first (WF-1) and second (WF-2) methods only consider the consumptive water use of the hydroelectricity generation system, while our third method (WF-3) accounts for the net water balance. Irrespective of the method, the WF of New Zealand’s hydroelectricity was found much smaller than the commonly cited international value of 22 m³ GJ⁻¹. Depending on the method, the national WF ranged from 1.55 m³ GJ⁻¹ (WF-3) to 6.05 m³ GJ⁻¹ (WF-1). The WF- 3 considers the net water balance including rainfall, which is the key driver for replenishing water resources. It provides meaningful information that helps our understanding of the differences of the WF in locations, which are diverse in terms of water resource availability. We highlight the effects of local climatic differences and the structural specifics of a hydroelectricity scheme on the WF. The large variation in the WF of hydropower across New Zealand illustrates the inappropriateness of using global average values. Local values, calculated using our hydrologically rational method, must be used.     

Real-World Vehicle Emissions: A Summary of the Ninth Coordinating Research Council On-Road Vehicle Emissions Workshop

ABSTRACT

In April 1999, the Coordinating Research Council sponsored a workshop focusing on our understanding of real-world emissions from motor vehicles. This summary presents the latest information on in-use light- and heavy-duty vehicle tailpipe and evaporative emissions, the effects of fuels on emissions, field programs designed to understand the contribution of mobile sources to emission inventories, efforts to evaluate and improve mobile source emission models, progress of vehicle inspection/ maintenance programs, and topics for future research. While significant progress has been made in understanding in-use vehicle emissions, further improvements are necessary. Moreover, the impact of current and future changes in emission control technologies and control programs will have to be monitored for effectiveness and incorporated into the emission factor models.     

The Influences of Ambient Particle Composition and Size on Particle Infiltration in Los Angeles,CA, Residences

Abstract

Particle infiltration is a key determinant of the indoor concentrations of ambient particles. Few studies have examined the influence of particle composition on infiltration, particularly in areas with high concentrations of volatile particles, such as ammonium nitrate (NH₄NO₃). A comprehensive indoor monitoring study was conducted in 17 Los Angeles–area homes. As part of this study, indoor/outdoor concentration ratios during overnight (nonindoor source) periods were used to estimate the fraction of ambient particles remaining airborne indoors, or the particle infiltration factor (F_INF), for fine particles (PM_2.5), its nonvolatile (i.e., black carbon [BC]) and volatile (i.e., nitrate [NO₃ ^?]) components, and particle sizes ranging between 0.02 and 10 μm. F_INF was highest for BC (median = 0.84) and lowest for NO₃ ^? (median = 0.18). The low F_INF for NO₃ ^? was likely because of volatilization of NO₃ ^? particles once indoors, in addition to depositional losses upon building entry. The F_INF for PM_2.5 (median = 0.48) fell between those for BC and NO₃ ^?, reflecting the contributions of both particle components to PM_2.5. F_INF varied with particle size, air-exchange rate, and outdoor NO₃ ^? concentrations. The F_INF for particles between 0.7 and 2 μm in size was considerably lower during periods of high as compared with low outdoor NO₃ ^? concentrations, suggesting that outdoor NO₃ ^? particles were of this size. This study demonstrates that infiltration of PM_2.5 varies by particle component and is lowest for volatile species, such as NH₄NO₃. Our results suggest that volatile particle components may influence the ability for outdoor PM concentrations to represent indoor and, thus, personal exposures to particles of ambient origin, because volatilization of these particles causes the composition of PM_2.5 to differ indoors and outdoors. Consequently, particle composition likely influences observed epidemiologic relationships based on outdoor PM concentrations, especially in areas with high concentrations of NH₄NO₃ and other volatile particles.     

Human-, Ovine-, and Bovine-Specific Viral Source Tracking Tools to Discriminate Between the Major Fecal Sources in Agricultural Waters

This study evaluated the sources of fecal contamination in different river catchments, using a combination of microbial source tracking tools, for human, ruminant, ovine and bovine livestock, in order to define appropriate water management strategies. Every source of waterway pollution was evaluated in river water samples from one urban river catchment and two important farming regions in New Zealand. Fecal pollution was initially measured by testing Escherichia coli and evaluating the presence of human- and ruminant-associated DNA markers of Bacteroidales (BiAdo, BacHum-UCD, BacH, and BacR) and human and ruminant fecal sterols/stanols ratios. Then specific fecal pollution sources were assessed with previously reported quantitative PCR assays targeting human-, bovine-, and ovine-specific viruses: human adenoviruses (HAdV), human JC polyomaviruses, bovine polyomaviruses (BPyV), and ovine polyomaviruses (OPyV). High level of ruminant fecal contamination was detected all over the farming areas, whereas no ruminant sources were identified in the urban river sampling sites. BacR was the most frequently observed ruminant marker and OPyV and BPyV allowed the identification of ovine and bovine fecal sources. The human fecal viral marker (HAdV) was the most frequently observed human marker, highly abundant in the urban sites, and also present in farming areas. This is the first study using simultaneously the ovine and the bovine viral markers to identify and quantify both bovine and ovine fecal pollution.     

Headspace and small-chamber studies of airborne diacetyl release from selected food flavoring mixtures: activity coefficients and air modeling implications

Laboratory studies were conducted to evaluate airborne release of diacetyl from selected mixtures simulating butter flavorings added to foods. The test materials included diacetyl (97% purity); 0.015%, 0.15%, 1.5%, and 3.0% diacetyl in a water/propylene glycol mixture; 1.5% diacetyl in deionized water or soybean oil; and 3% or 6% diacetyl in a commercial steam distillate from milk fermentation known as “butter starter distillate.” Diacetyl was quantified by gas chromatography with flame ionization detection. Expected concentration-dependent emission patterns based on liquid diacetyl content were demonstrated, but were significantly altered by mixture composition. Soybean oil and deionized water more readily released diacetyl when compared with starter distillate, propylene glycol solutions, and pure diacetyl. Measured diacetyl concentrations under static headspace and dynamic flow-chamber conditions were compared to estimated concentrations utilizing Raoult's law with published and fitted activity coefficient corrections for each mixture, indicating that published coefficients often understated the measured concentrations. It is concluded that headspace (static) and small-chamber (dynamic) measurements of airborne diacetyl provide data to assist in validating model-estimated airborne diacetyl concentrations by using mixture-specific activity coefficients. Implications of these empirical data for validating exposure estimates for diacetyl based on near-field/far-field modeling in workplace settings are discussed.