Agent based simulation of a small catchment water management in northern Thailand: Description of the CATCHSCAPE model

Due to mounting human pressure, stakeholders in northern Thailand are facing crucial natural resources management (NRM) issues. Among others, the impact of upstream irrigation management on downstream agricultural viability is a growing source of conflict, which often has both biophysical and social origins. As multiple rural stakeholders are involved, appropriate solutions should only emerge from negotiation. CATCHSCAPE is a Multi-Agent System (MAS) that enables us to simulate the whole catchment features as well as farmer’s individual decisions. The biophysical modules simulate the hydrological system with its distributed water balance, irrigation scheme management and crop and vegetation dynamics. The social dynamics are described as a set of resource management processes (water, land, cash, labour force). Water management is described according to the actual different levels of control (individual, scheme and catchment). Moreover, the model’s architecture is presented in a way that emphasises the transparency of the rules and methods implemented. Finally, one simulated scenario is described along with its main results, according to different viewpoints (economy, landscape, water management).     

Influence of ageing of residues on the availability of herbicides for leaching

Losses by leaching of chlorotoluron, isoproturon and triasulfuron from small intact columns of a structured clay loam and an unstructured sandy loam soil were measured in five separate field experiments. In general, losses of all three herbicides were greater from the clay loam than from the sandy loam soil and the order between herbicides was always triasulfuron > isoproturon > chlorotoluron. Differences between experiments were also consistent for every soil/herbicide combination. There was no relationship between total loss and either total rainfall or cumulative leachate volume. When weighting factors were applied to the rainfall data to make early rainfall more important than later rainfall, there were significant positive relationships between cumulative weighted rainfall and total losses. Also, there were significant negative correlations between total losses and the delay to accumulation of 25 mm rainfall (equivalent to one pore volume of available water) in the different experiments. In laboratory incubations, there was a more rapid decline in aqueous (0.01 M calcium chloride) extractable residues than in total solvent extractable residues indicating increasing sorption with residence time. However, the rate of change in water extractable residues could not completely explain the decrease in leachability with ageing of residues in the field. Short-term sorption studies with aggregates of the two soils indicated slower sorption by those of the clay loam than by those of the sandy loam suggesting that diffusion into and out of aggregates may affect availability for leaching in the more structured soil. Small scale leaching studies with aggregates of the soils also demonstrated reductions in availability for leaching as residence time in soil was increased, which could not be explained by degradation. These results therefore indicate that time-dependent sorption processes are important in controlling pesticide movement in soils, although the data do not give a mechanistic explanation of the changes in leaching with ageing of residues.     

Comparison of beach bacterial water quality indicator measurement methods

Three methods (membrane filtration, multiple tube fermentation, and chromogenic substrate technology kits manufactured by IDEXX Laboratories, Inc.) are routinely used to measure indicator bacteria for beach water quality. To assess comparability of these methods, quantify within-laboratory variability for each method, and place that variability into context of variability among laboratories using the same method, 22 southern California laboratories participated in a series of intercalibration exercises. Each laboratory processed three to five replicates from thirteen samples, with total coliforms, fecal coliforms or enterococci measured depending on the sample. Results were generally comparable among methods, though membrane filtration appeared to underestimate the other two methods for fecal coliforms, possibly due to clumping. Variability was greatest for the multiple tube fermentation method. For all three methods, within laboratory variability was greater than among laboratories variability.     

Air pollution exposure monitoring and estimation. Part II. Model evaluation and population exposure

The air pollution dispersion model EPISODE has been developed at the Norwegian Institute for Air Research (NILU) over the past several years in order to meet the needs of modern air quality management work in urban areas. The model has recently been used as a basis for exposure calculations of NOx and NO2 in order to assess the effects of different traffic diversion measures on health and well being for the residents in the V?lerenga-Ekeberg-Gamlebyen area in Oslo. Here we describe some results from the most recent evaluations of the model for NOx and NO2 at station Nordahl Brunsgate in Oslo for the period 1 October 1996-19 November 1996. In addition examples of population exposure calculations for Oslo performed during the winter period of 1995-96, are also presented.     

Characterization,source apportionment and risk assessment of PAHs in urban surface dust in Shenyang city,China

Environmental Geochemistry and Health - Characteristics, profile composition, ecological and human health risk of polycyclic aromatic hydrocarbons in surface dust collected from Shenyang city,...     

Development and Analysis of Oxygen-Sensing Probes for In Situ Monitoring of Unsaturated Solid-State Biodegradation Processes

ABSTRACT

Oxygen (O₂) sensors have been developed for in situ measurement of O₂ in high-solids degradation processes. The O₂ sensor has been shown to withstand the corrosive environment of the biodegradation process with high humidity and temperatures exceeding 60 ^oC. Calibration tests prior to and after in situ operation showed the sensor to perform accurately and reproducibly after 71 days of in situ operation.

A linear relationship between O₂-sensor output and water vapor pressure was confirmed through calibration experiments. To compensate for the effect of water vapor pressure on O₂-sensor measurements, O₂ concentration was expressed on a dry air basis using the confirmed linear relationship. In situ O₂-sensor output expressed on a dry air basis was found to follow trends of gas samples analyzed by gas chromatography with good agreement.     

Fluorescent Tracer Studies of Pollutant Transport in the San Francisco Bay Area

To simulate the transport and diffusion of airborne contaminants across a metropolitan region, point-source releases of fluorescent tracer material were made near various urban centers and some 50 samplers were arrayed in expected downwind directions. The effects of land-water, hill-valley, and urban-rural differences on airflow and diffusion were observed in their existing interrelationships during these experiments. Since the tracer could be assessed with high sensitivity over great distances, tracer results provided a quantitative indicator of pollutant dispersion across an extensive metropolitan complex.

From July 1967 through June 1968, the test series included typical seasonal weather patterns, with emphasis on those conducive to the travel and accumulation of pollutants. In each test about 15 kilograms of tracer material were released during two-hour periods, and significant dosages were found at downwind distances up to 80 kilometers. All tests were conducted during daylight hours, to coincide better with the oxidant-type pollution important in this region.

Dispersion characteristics showed much greater complexity than predictable from classical models, thus limiting the applicability of such models in this region. Built-up urban areas increased the initial dispersion rates of tracer clouds, and travel over water tended to decrease them. Hilly terrain resulted in increased dispersion, but channeling associated with such terrain caused locally higher concentrations. The complex horizontal dosage patterns obtained did confirm previously observed airflow patterns as aids in predicting pollutant distributions.     

Building resilience and adaptation to manage Arctic change

Unprecedented global changes caused by human actions challenge society's ability to sustain the desirable features of our planet. This requires proactive management of change to foster both resilience (sustaining those attributes that are important to society in the face of change) and adaptation (developing new socioecological configurations that function effectively under new conditions). The Arctic may be one of the last remaining opportunities to plan for change in a spatially extensive region where many of the ancestral ecological and social processes and feedbacks are still intact. If the feasibility of this strategy can be demonstrated in the Arctic, our improved understanding of the dynamics of change can be applied to regions with greater human modification. Conditions may now be ideal to implement policies to manage Arctic change because recent studies provide the essential scientific understanding, appropriate international institutions are in place, and Arctic nations have the wealth to institute necessary changes, if they choose to do so.     

Inorganic PM2.5 at a U.S. agricultural site

In this study, we present approximately two years (January 1999-December 2000) of atmospheric NH3, NH4+, HCl, Cl-, HNO3, NO3-, SO2, and SO4= concentrations measured by the annular denuder/filter pack method at an agricultural site in eastern North Carolina. This site is influenced by high NH3 emissions from animal production and fertilizer use in the surrounding area and neighboring counties. The two-year mean NH3 concentration is 5.6 (+/-5.13) microg m(-3). The mean concentration of total inorganic PM2.5, which includes SO4=, NO3-, NH4+, and Cl-, is 8.0 (+/-5.84) microg m(-3). SO4=, NO3-, NH4+, and Cl- represent, respectively, 53, 24, 22, and 1% of measured inorganic PM2.5. NH3 contributes 72% of total NH3 + NH4+, on an average. Equilibrium modeling of the gas+aerosol NH3/H2SO4/HNO3 system shows that inorganic PM2.5 is more sensitive to reductions in gas + aerosol concentrations of sulfate and nitrate relative to NH3.