An integrated monitoring system is proposed for India that will monitor terrestrial, coastal, and oceanic environments.

Following the 1984 divestiture of AT&T, local telephone service was provided by several Regional Bell. Operating Companies (RBOCs). The RBOCs served as monopoly providers of local telephone service in their respective territories but were prohibited from offering long-distance service to their in-region subscribers. Section 271 of the landmark Telecommunications Act of 1996 allows an RBOC to offer in-region long-distance service if it demonstrates that the local telephone exchange market is open to competitive entry. This study empirically evaluates the efficacy of this policy by considering the impact of RBOC entry into long-distance on the development of competitive entry into local telephony. The results suggest that section 271 has been successful in promoting entry into local telephony. However, aggregate price data suggest that this entry has not been realized with lower rates for residential telephone subscribers.

In 1996 Congress passed the landmark Telecommunications Act (hereafter "the Act"). The Act, under Section 271, allowed the Regional Bell Operating Companies to offer long distance service to their local customers in exchange for opening their own local networks to local competitors in that state. Using a state-level panel data set we evaluate the effect of FCC Section 271 decisions on entry into the local telephone exchange market. OLS and Poisson estimates suggest that Section 271 approvals increase the number of local competitive entrants before and during the year the approval is granted. We obtain no statistically significant and robust results for the effects of Section 271 approval on entry during the following year. In addition, the estimates suggest that Section 271 denials have no statistically significant effect on the entry of local competitors.

The incentive of the Regional Bell Operating Companies (RBOCs) to degrade the quality of interstate access services, an essential input provided to rival long-distance carriers, once they begin offering long-distance services has been a controversial issue in the academic literature. Using a panel of state-level data over the years 1996-2001, this paper investigates whether the RBOCs engage in such 'non-price discrimination' upon entering the long-distance market. The results suggest the RBOCs improve the quality of some of their interstate access service offerings before entering the interexchange market, but begin degrading the quality of these services immediately afterward. Copyright (C) 2003 John Wiley Sons, Ltd.

This paper presents an overview of the Experiment for Regional Sources and Sinks of Oxidents (EXPRESSO) including the objectives of the project, a detailed description of the characteristics of the experimental region and of field instrumentation deployed, and a summary of the main results of all components of the experiment. EXPRESSO is an international, multidisciplinary effort to quantify and better understand the processes controlling surface fluxes of photochemical precursors emitted by vegetation and biomass burning along a tropical forest to savanna gradient in central Africa. The experiment was conducted at the beginning of the dry season in November‐December 1996. Three main research tools were deployed during this period: (1) the French research aircraft (Avion de Recherche Atmosphérique et de Télédétection, Fokker 27), instrumented for chemistry and flux measurements (CNRS‐ France), (2) two satellite receivers for in situ acquisition of National Oceanic and Atmospheric Administration‐advanced very high resolution radiometer (NOAA‐AVHRR) imagery for fire detection (EC‐JRC, Ispra, Italy), and (3) a 65‐m walkup tower installed at a tropical forest site in the Republic of Congo (National Center for Atmospheric Research, Boulder, Colorado). Average dynamic and turbulence characteristics over savanna and forest ecosystems were retrieved from aircraft measurements. They illustrate the complex atmospheric circulation occurring in this region in the vicinity of the Intertropical Convergence Zone. Satellite receivers were operated three times a day to produce maps of fire distribution. Statistics and mapping of burned surfaces from NOAA‐AVHRR and ERS‐Along Track Scanning Radiometer space systems have been developed. The influence of biogenic and biomass burning sources on the chemical composition of the lower atmosphere was studied through both aircraft and tower measurements. The EXPRESSO field campaign was followed by modeling efforts (regional and global scales) in which model components are evaluated using the experimental data.

Methyl bromide is the single largest contributor of stratospheric Br and an important contributor to stratospheric ozone depletion. Soils have recently been identified as a significant sink of methyl bromide (Shorter et al., 1995, Nature 377 (6551), 717–719). As is the case for other trace gases, methyl bromide deposition rates vary for different ecosystems and depend on soil characteristics. The limited data available prevents an accurate global estimate but does allow initial attempts to establish the importance of this sink. We have investigated the methyl bromide sink for four different ecosystems, and found deposition rates that range from about 0.02±0.005–0.38±0.170 cm s-1. These rates result in a global sink that is higher, although of the same order of magnitude, than that reported by Shorter et al. (1995). The partial lifetime of methyl bromide with regard to soil sink is estimated to be between 0.97 and 3.54 yr resulting in a mean total lifetime of 0.61 yr. Estimates of a methyl bromide ozone depletion potential (ODP) range between 0.22 and 0.48. About half of the uncertainty in the ODP estimates is associated with current global methyl bromide soil-sink estimates.

ABSTRACTNests of a fungus-growing termiteMacrotermes jeannelidischarge all their metabolic gases through a single outlet to the atmosphere. This made it possible to measure the production of metabolic gases, and the rates of water loss, for intact nests in the field. Rates of production of carbon dioxide and methane from isolated nest components (different termite castes and intact fungus combs) were measured. Using previously published nest population data and fungus comb weights in relation to nest size, the expected gas production rates for intact nests were calculated. These estimates were compared with direct observations of the gaseous outflow from intact nests. The rates were in reasonable agreement, but some nests emitted excess carbon dioxide, probably produced by respiration of tree roots and non-termite soil organisms. Large nests may have a total gas outflow of 100,000 to 400,000 1 d–1including 800 to 1500 1 d–1of CO2and 0.5 to 1.3 1 d–1of CH4. Nests lose water at the rate of up, to 13 1 d–1gross, but allowing for ambient humidity the net water loss was up to about 5 1 d–1. Some of this is metabolic water, but the larger proportion comes from the soil. Area-based estimates of gas production were made for this and two other species ofMacrotermes, but they are not accurate because the field distribution and mound density are not adequately known.

Measurements of carbon monoxide and nonmethane hydrocarbons were made in situ at the Mauna Loa Observatory from September 1991 through August 1992. A distinct seasonal cycle in concentrations was observed for CO and most NMHCs, with higher average concentrations from January through April and much lower average concentrations from mid‐May through October. The sources of CO and NMHCs appeared to vary with season and appeared more homogeneous in winter (urban/industrial) and spring (unidentified). The ocean around Hawaii did not appear to be a major source of CO and most NMHCs, but was the major source of ethane and propene. Ethene and propene were always present in free tropospheric air sampled, indicating daily exchange between the free troposphere and the marine boundary layer. Air arriving at MLO during free tropospheric flow periods had seasonally similar photochemical age (approximately 20 days), with no significant fresh source inputs of NMHCs (except ethene and propene) within at least 10 days. The influence of atmospheric dilution processes on atmospheric concentrations was weakest in the spring period, when the influence of chemical loss processes was greatest. Aircraft measurements made during the spring agreed in trends and absolute concentrations with ground‐based measurement made at MLO. The temporal trends in concentrations of NMHCs within altitude ranges were similar. These trends varied with altitude and characterized a layered atmosphere with differing chemical composition. Acetone and methyl ethyl ketone were detected in most samples. N‐alkyl aldehydes were also detected but may be artifacts formed from organic aerosols collected in the sampling process.

A global three-dimensional atmospheric tracer transport model is used to study the sources and sinks of atmospheric carbon monoxide (CO). Source functions are included for the release of CO from the oxidation of methane, technological sources, biomass burning, the oxidation of hydrocarbons and the oceans. The removal of CO from the atmosphere is assumed to be largely due to oxidation through reaction with hydroxyl radicals (OH) and removal by soils. To compute CO destruction, a parameterised OH field, calibrated to reproduce the loss of methyl chloroform, is employed. For the removal of CO by soils, a model is used which assumes that the flux of CO into soils is dependent on net primary productivity. To constrain the magnitude of the CO sources and sinks, atmospheric observations of CO are used. The deduced total CO source is 1855–2355 Tg. If present estimates of the release of CO from biomass burning and oxidation of hydorcarbons are correct then removal by soils could potentially be a substantial sink for CO.

Patterns and controls of carbon trace gas emissions from wetlands may vary depending upon the spatial and temporal scale being examined. The factors affecting these emissions are thought to be hierarchically related according to their respective scales of importance. A hierarchical model of processes controlling methane emissions from wetlands is presented and examined here. During the 1990 Northern Wetlands Study (NOWES) methane (CH4), carbon dioxide (CO2), and non‐methane hydrocarbon (NMHC) fluxes were measured in static chambers along a 100 km transect in the Hudson Bay lowland (HBL). Environmental variables, vegetation abundance, and ecosystem age and structure were also quantified at each sampling site. The findings indicate that CH4 emissions from peatlands (e.g., bogs and fens) and other wetlands (e.g., salt marshes) in the region were low, and were nil or negative (i.e., CH4 uptake) in forests and bog forests dominated by aspen and black spruce. Site to site variations in mean CH4 flux appeared to be most closely related to mean water table and sedge productivity, both of which are intercorrelated. Seasonal changes in CH4 flux tend to follow soil temperature fluctuations. Instantaneous CO2 and CH4 daytime fluxes exhibit a negative correlation, suggesting that photosynthetic assimilation of carbon may be related to CH4 emissions, although the processes of CO2 and CH4 production are occurring at somewhat different temporal scales. No diurnal variations in CH4 flux could be detected. While soil water pH trends are not fully explored, there is some indication that high CH4 fluxes are concentrated around pH 4 and pH 7. Soil temperature closely follows the seasonal progression of CH4 flux. Estimated CH4 seasonal flux (1.5–3.9 g CH4 m−2 season−1) and estimated aboveground net primary productivity (NPP) (90–400 g dry weight m−2 season−1) show systematic changes along a successional sequence which are consistent with patterns predicted from successional theory. Estimated seasonal NMHC emissions (0.5–1.4 g C m−2 season−1) exhibit an increase along the succession from salt marsh to Sphagnum bog communities. Data from several studies were combined to estimate seasonal CO2 flux from three sites. The estimated fluxes range from a net uptake of 23 g CO2 m−2 season−1 to a net loss of 77 g CO2 m−2 season−1, although there are large uncertainties in these estimates. It is inferred from the assessment of ecosystem age and structure that disturbance effects and successional changes occurring over hundreds to thousands of years in the HBL strongly control regional CH4, CO2 and NMHC emissions by influencing NPP, species composition, community structure, soil (peat) development, and landscape hydrology. Given this, it is likely that models of carbon trace gas flux based on succession models may be useful in predicting climate change‐landscape change feedbacks.

A completely automated gas chromatography-flame ionization detector system with cryogenic sample freeze-out for measuring atmospheric non-methane hydrocarbons was deployed at the Mauna Loa Observatory, Hawaii during the MLOPEX II experiment, September 1991 through August 1992. The system was designed to (1) rapidly trap air samples of up to 4 litres volume to allow for sub-parts per trillion detection limits, (2) eliminate interferences from ambient ozone, water vapor carbon dioxide, (3) reduce to negligible levels any contamination in the analytical systems, and (4) allow for continuous, unattended operation. The instrumentation consisted of two parallel analytical systems, employing packed capillary chromatographic columns, which allowed quantification of C2–C10, non-methane hydrocarbons from sub-parts per trillion to parts per million concentrations. A dynamic dilution system was used to calibrate the analytical system over the range of concentrations measured (low parts per trillion to parts per billion) at this site.

A new technique for estimating surface fluxes of trace gases, the mixed-layer gradient technique, is used to calculate isoprene and terpene emissions from forests. The technique is applied to tethered balloon measurements made over the Amazon forest and a pine-oak forest in Alabama at altitudes up to 300 m. The observations were made during the dry season Amazon Boundary Layer Experiment (ABLE 2A) and the Rural Oxidants in the Southern Environment 1990 experiment (ROSE I). Results from large eddy simulations of scalar transport in the clear convective boundary layer are used to infer fluxes from the balloon profiles. Profiles from the Amazon give a mean daytime emission of 3630 +/- 1400 mu g isoprene m(-2) h(-1), where the uncertainty represents the standard deviation of the mean of eight flux estimates. Twenty profiles from Alabama give emissions of 4470 +/- 3300 mu g isoprene m(-2) h(-1), 1740 +/- 1060 mu g alpha-pinene m(-2) h(-1), and 790 +/- 560 mu g beta-pinene m(-2) h(-1), respectively. These results are in agreement with emissions derived from chemical budgets. The emissions may be overestimated because of uncertainty about how to incorporate the effects of the canopy on the mixed-layer gradients. The large variability in these emission estimates is probably due to the relatively short sampling times of the balloon profiles, though spatially heterogeneous emissions may also play a role. Fluxes derived using this technique are representative of an upwind footprint of several kilometers and are independent of hydrocarbon oxidation rate and mean advection.

Isoprene emission from plants represents one of the principal biospheric controls over the oxidative capacity of the continental troposphere. In the study reported here, the seasonal pattern of isoprene emission, and its underlying determinants, were studied for aspen trees growing in the Rocky Mountains of Colorado. The springtime onset of isoprene emission was delayed for up to 4 weeks following leaf emergence, despite the presence of positive net photosynthesis rates. Maximum isoprene emission rates were reached approximately 6 weeks following leaf emergence. During this initial developmental phase, isoprene emission rates were negatively correlated with leaf nitrogen concentrations. During the autumnal decline in isoprene emission, rates were positively correlated with leaf nitrogen concentration. Given past studies that demonstrate a correlation between leaf nitrogen concentration and isoprene emission rate, we conclude that factors other than the amount of leaf nitrogen determine the early-season initiation of isoprene emission. The late-season decline in isoprene emission rate is interpreted as due to the autumnal breakdown of metabolic machinery and loss of leaf nitrogen. In potted aspen trees, leaves that emerged in February and developed under cool, springtime temperatures did not emit isoprene until 23 days after leaf emergence. Leaves that emrged in July and developed in hot, midsummer temperatures emitted isoprene within 6 days. Leaves that had emerged during the cool spring, and had grown for several weeks without emitting isoprene, could be induced to emit isoprene within 2 h of exposure to 32°C. Continued exposure to warm temperatures resulted in a progressive increase in the isoprene emission rate. Thus, temperature appears to be an important determinant of the early season induction of isoprene emission. The seasonal pattern of isoprene emission was examined in trees growing along an elevational gradient in the Colorado Front Range (1829-2896 m). Trees at different elevations exhibited staggered patterns of bud-break and initiation of photosynthesis and isoprene emission in concert with the staggered onset of warm, springtime temperatures. The springtime induction of isoprene emission could be predicted at each of the three sites as the time after bud break required for cumulative temperatures above 0°C to reach approximately 400 degree days. Seasonal temperature acclimation of isoprene emission rate and photosynthesis rate was not observed. The temperature dependence of isoprene emission rate between 20 and 35°C could be accurately predicted during spring and summer using a single algorithm that describes the Arrhenius relationship of enzyme activity. From these results, it is concluded that the early season pattern of isoprene emission is controlled by prevailing temperature and its interaction with developmental processes. The late-season pattern is determined by controls over leaf nitrogen concentration, especially the depletion of leaf nitrogen during senescence. Following early-season induction, isoprene emission rates correlate with photosynthesis rates. During the season there is little acclimation to temperature, so that seasonal modeling simplifies to a single temperature-response algorithm.

Isoprene, a biogenic hydrocarbon emitted from vegetation, has been detected at sub-ppb levels, using a commercially available reduction gas detector (RGD) with an isothermal, portable gas chromatograph. For 1 ml samples, a detection limit of 300–500 parts per trillion (over an order of magnitude less than the traditional gas chromatography-flame ionization detection technique [GC-FID]) was achieved. The detector response was linear up to 500 ppb. This technique (GC-RGD) is compared with GC-FID measurements in studies of ambient isoprene mixing ratios within and above an oak forest in northeastern U.S.A. Applications of laboratory studies of the mechanism of isoprene production at the leaf level are also discussed.

The exchange of various trace species and energy at the earth's surface plays an important role in climate, ecology, and human health and welfare. Surface exchange measurements can be difficult to obtain yet are important to understand physical processes, assess environmental and global change impacts, and develop robust parameterizations of atmospheric processes. The physics and turbulent structure of the atmospheric boundary layer are reviewed as they contribute to dry surface exchange rates (fluxes). Micrometeorological, budget, and enclosure techniques used to measure or estimate surface fluxes are described, along with their respective advantages and limitations. Various measurement issues (such as site characteristics, sampling considerations, sensor attributes, and flow distortion) impact on the ability to obtain representative surface-based and airborne flux data.

The emission of isoprene and monoterpenes from plants is influenced by light and leaf temperature, which account for almost all short‐term variations (minutes to days) and a large part of spatial and long‐term variations. The temperature dependence of monoterpene emission varies among monoterpenes, plant species, and other factors, but a simple exponential relationship between emission rate (E) and leaf temperature (T), E = Es [exp (β(T − Ts))], provides a good approximation. A review of reported measurements suggests a best estimate of β = 0.09 K−1 for all plants and monoterpenes. Isoprene emissions increase with photosynthetically active radiation up to a saturation point at 700–900 μmol m−2 s−1. An exponential increase in isoprene emission is observed at leaf temperatures of less than 30°C. Emissions continue to increase with higher temperatures until a maximum emission rate is reached at about 40°C, after which emissions rapidly decline. This temperature dependence can be described by an enzyme activation equation that includes denaturation at high temperature. Algorithms developed to simulate these light and temperature responses perform well for a variety of plant species under laboratory and field conditions. Evaluations with field measurements indicate that these algorithms perform significantly better than earlier models which have previously been used to simulate isoprene emission rate variation. These algorithms account for about 90% of observed diurnal variability and can predict diurnal variations in hourly averaged isoprene emissions to within 35%.

We report trace gas measurements made both inside and outside the Kuwait oil‐fire smoke plume during a flight of an instrumented research aircraft on May 30, 1991. Concentrations of SO2, CO, and NOx averaged vertically and horizontally throughout the plume 80 km downwind of Kuwait City were 106, 127, and 9.1 parts per billion by volume (ppbv), respectively, above background concentrations. With the exception of SO2, trace gas concentrations were far below typical U.S. urban levels and primary national ambient air quality standards. Ambient ozone was titrated by NO in the dark, dense core of the smoke plume close to the fires, and photochemical ozone production was limited to the diffuse edge of the plume. Photochemical O3 production was noted throughout the plume at a distance of 160 km downwind of Kuwait City, and averaged 2.3 ppbv per hour during the first 3 hours of transport. Little additional photochemical production was noted at a downwind range of 340 km. The fluxes of sulfur dioxide, carbon monoxide, and reactive nitrogen from the roughly 520 fires still burning on May 30, 1991 are estimated at 1.4 × 107 kg SO2/d, 6.9 × 106 kg CO/d, and 2.7 × 105 kg N/d, respectively. Generally low concentrations of CO and NOx indicate that the combustion was efficient and occurred at low temperatures. Low total nonmethane hydrocarbon concentrations suggest that the volatile components of the petroleum were burned efficiently.

ABSTRACT Estimates were made of the populations of seven nests of Macrotermes jeanneli of different sizes in Kenya. Caste and instar composition were examined, and relationships of these to the dimensions of the mound were investigated. Survival of nests of different sizes was followed over four years.

Atmospheric methane, nonmethane hydrocarbons, and carbon monoxide were measured at the Mauna Loa Observatory on the island of Hawaii in May and June 1988. The daily island upslope/downslope circulation resulted in a variable mixture of boundary layer and free tropospheric air at the observatory. Mixing ratios of these gases were higher during upslope flow than during downslope flow. Mixing ratios characteristic of the free troposphere at this altitude were most often measured during nighttime, downslope flow. Local marine emissions of ethylene and propylene and emissions of isoprene from island vegetation were detected during upslope circulation, but ethylene and propylene were also often detected at night during downslope circulation, indicating that air sampled during nighttime downslope flow may have included some air recently transported from the marine boundary layer. Comparison of data for methane, carbon monoxide, ethane, and propane from in situ measurements with measurements made from canister samples collected during the experiment showed very good agreement. Fluxes of isoprene from selected dominant island flora were also measured.