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This study examined the impact of plants on acid sulphate soils with the aim of determining whether plants are able to reduce acid production. The study was conducted with clayey acid sulphate soil under controlled conditions with treatments lasting up to 24 weeks and measurements made in the top 0–60 mm of soil. pH profiles in the soil were strongly dependent on soil moisture and the pattern of irrigation. When bare soil was allowed to dry down without further irrigation, there was very little acidification of either the surface or subsurface layers. Planting of Phragmites accelerated soil drying and caused extensive cracking and acidification of the subsoil under simulated drought conditions. Under a wetting and drying regime, both Phragmites and a surface spreading grass Paspalum increased soil acidification, while a surface spreading herbaceous shrub Cotula had little effect on acidification. There was no evidence that live plants could ameliorate acid sulphate soils. However, application of dead plant matter to the surface of the soil was effective in reducing acidification, especially if submerged.

Publisher Summary This chapter discusses the human modification of global biogeochemical cycles. Many biogeochemical and physical processes are involved in determining the climate of the Earth, and some of these are being significantly perturbed by human activity. The physical and chemical composition of the atmosphere determines the transmission, absorption, and reflection of incoming solar radiation and outgoing terrestrial radiation, and the resulting energy balance determines surface temperature. The biogeochemical cycles of sulfur—a crucial component of clouds and most aerosols—and of carbon and nitrogen, which form radiatively important trace gases, are central to the radiative properties of the atmosphere. The combustion of fossil fuels, and the consequent oxidation of nitrogen in combustion air has greatly modified the natural atmospheric cycles of C, N, and S. Although the change of atmospheric CO 2 has little effect on the chemical composition of precipitation, sulfur- and nitrogen-containing acids have a major impact on the chemical composition of rain and snow. These acids in turn perturb the cycles of important minor elements, such as aluminum, through the weathering process in rocks and soils.

Emission factors for particulate matter and carbon monoxide have been measured for wood, anthracite coal, and bituminous coal burned in residential heaters operated at less than 15 kW (50,000 Btu/hr). In these studies the stove effluent is mixed with about four volumes of outside air and samples are collected about two minutes after mixing. The main purpose of using this sampling method is to simulate atmospheric conditions more closely. Particulate samples are collected on 20 × 25 cm filters after cyclone preseparation of particles larger than 4 μm. Carbon monoxide concentrations are measured with Draeger tubes. Particulate emission factors for wood ranged from 1.6 to 6.4 g/kg (fuel) and were found to depend on the fuel load and the firing rate, as indicated by earlier studies. These values are substantially less than the values obtained previously for stoves operated under similar conditions. The average particulate emission factors for bituminous and anthracite coal are 10.4 and 0.50 g/kg, respectively...

The interrelationship of salinity management and water management is a factor which is sometimes easily overlooked in the water resources planning, even though it can place a limit on the degree of water resource development within a basin. Costs and control measures of salinity management are considered on a case study of the Colorado River basin where salinity damages are found to be higher than previously estimated. After review of the costs of salinity management, the possible control measures, and research on adaptions in agricultural use of more saline water, it can be concluded that, at very least, the management of water quantity and water quality, especially in arid regions, are closely intertwined.

Particulate emission factors for two wood stove models have been determined for two types of fuel and a range of operating conditions. The emission factors range from 1 g/kg (fuel) to 24 g/kg. A model is presented which represents the emission factor as a simple function of the ratio of fuel load to combustion rate, or the length of time between refueling. This model is felt to be appropriate for evaluating the impact of wood-based residential space heating on ambient air concentrations of particulate matter If certain assumptions can be made about stove operating conditions. An application of the emission factor model to a typical community suggests that the contribution of wood stoves to ambient particulate levels might reach 100 μg/m3 if the entire heating load were carried by wood. Preliminary analyses of the particulate matter Indicate that benzene extractables range from 42% of the total particulate mass at short refuel times to 67% at longer refuel times. About 45% of the mass of benzene extractabl...

A methodology is derived permitting determination by dynamic programming of the optimal timing of irrigation, to produce the greatest net return inclusive of the cost of irrigation. It will be particularly useful under conditions in which seasonal supply is inadequate but reasonably predictable. Analysis is based upon the principle that the adverse effects of deficiencies (nutrition, excessive salinity, soil moisture, etc.) are geometric when existing in combination. For general use, additional data concerning the yield coefficients will be required covering each of the critical stages in the growth of the crops independently.

Two experiments using a microscale approach to the organic laboratory in order to improve air quality in the lab.