An IFYGL Carbon Budget for Lake Ontario

A carbon budget was produced for each month of the International Field Year for the Great Lakes (IFYGL) year (April 1972 to March 1973) to determine the importance of the various sources and sinks of carbon. Major sources were found to be CO₂ which was fixed in organic matter during primary production and inorganic carbon in tributary streams, especially the Niagara River. The major sinks were found to be inorganic carbon outflow at the St. Lawrence River and net CO₂ gas exchange between the inorganic carbon pool and the atmosphere. Inflow and outflow of organic matter in rivers, sedimentation of organic and inorganic matter, ground water transport, and municipal and industrial perturbations accounted in total for less than 10% of the annual budget.The lake had an inventory of approximately 4.0 × 10¹⁰ kg of inorganic carbon and approximately an order of magnitude less organic carbon. The riverborne flux of inorganic carbon of 0.5 × 10¹⁰ was 13% of the lake's inventory, assuming complete mixing; a minimum mean residence time of 8 years can be calculated from that inventory.The seasonal cycle inherent in the fixation of carbon in primary production was primarily balanced by a complementary seasonal cycle in the air-lake CO₂ gas exchange system. The lake acts as a sink for CO₂ gas in the warm months when primary productivity is highest and as a source of CO₂ in the colder part of the year.The IFYGL year had higher than normal rates of water flow, but this does not appear to have perturbed the inorganic carbon system. A comparison of IFYGL carbon budget results with corresponding estimates calculated for a typical year from historical data shows no major differences.     

Thermal effects on the forward characteristics of silicon p-i-n diodes at high pulse currents

When applying high pulse currents, the resulting temperature increase in the base regions of p-i-n diodes and thyristors leads to notable changes in the forward characteristics. (I) Decrease of carrier mobility noticeably increases the voltage drop across the diode and tends to limit the current density. (II) When the temperatures are sufficiently high to supply high intrinsic carrier concentrations, the temperature coefficient of the resistivity becomes negative. This can lead to current localization and destruction of the diodes.

To study these effects, the temperature of the base regions was monitored during high pulse currents using thermal i.r. emission. Indication for current limit occurs above 200°C, when the diodes are heated from room temperature. The negative temperature coefficient of the resistivity occurs at temperatures at which the intrinsic carrier concentration has reached the same order of magnitude as the injected carrier density. Simple theoretical treatment yields reasonably good agreement with the experimental results.     

Effects of changes in the atmosphere on solar insolation

A review of the nature of solar radiation and the spectral distribution of its energy is presented. The attenuation of solar radiation by scattering and absorption and the effects of atmospheric pollutants on radiation attenuation with an estimate of the long-term effects of pollutants is discussed.     

Chemical evaluation of oil from field-and storage-damaged soybeans

In recent years, prolonged wet weather during the harvest season resulted in excessive field- and storagedamaged soybeans, particularly in the Southeast. As the severity of the damage increased, analysis of the oil extracted from these beans showed a corresponding increase in free fatty acids, Lovibond color, and content of oxidative deterioration products which absorb at 270 nm. In general, there was a substantial decrease in total oil content and an almost complete deterioration of phospholipids in severely damaged beans during storage. Initially, the oxidative stability of the oils decreased rapidly. After storage damage became severe, the stability increased substantially, possibly because of the formation of unidentified deterioration products which had high antioxidant properties. The study clearly showed that the processing of field- and storage-damaged soybeans would result in substantial refining losses to processors and that the finished oil would be of inferior quality. ARS, USDA     

Chlorinated organics from chlorine used in water treatment

The contribution from impurities in chlorine to levels of chlorinated organics found in potable water after chlorination was investigated. Techniques for sampling of chlorine and gas chromatography (GC) determination of chlorinated organics in chlorine are described. The detection limits were better than 1 ppm for each of chloromethane, dichloromethane, chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene, hexachloroethane, hexachloropropane and hexachlorobenzene in chlorine. With the exception of chloroform which occasionally accounted for nearly 1 μg l⁻¹ in water, the levels of the nine compounds in chlorine accounted for less than 0.1 μg l⁻¹ of each compound in chlorinated water from 10 Canadian treatment plants. The occurrence of these nine and 28 additional chlorinated organics previously detected in water supplies was determined by aid of liquid-liquid extraction of water samples. Seven compounds, including chloroform, carbon tetrachloride, trichloroethylene and tetrachloroethylene were detected, usually at levels ranging from 0.1 to 1 μg l⁻¹ in chlorinated water from the treatment plant.