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Stream water chemistry varies hyperbolically with stream discharge through four decades of discharge change within the Hubbard Brook Experimental Forest, New Hampshire. This dilution process is most simply explained by the mixing of rain water or surface water with deeper soil water. The resultant mixture of waters subsequently appears as stream water. Sodium and silica concentrations in stream water are markedly diluted during high discharge periods while hydrogen ion, aluminum, and nitrate concentrations are increased. Magnesium, calcium, sulfate, chloride and potassium concentrations are changed very little by stream discharge variations. During the summer, biologic activity measurably reduces the concentration of nitrate and potassium in stream water. [ABSTRACT FROM AUTHOR]

The weights of membrane filters used in gravimetric analysis of water were significantly changed by electrostatic charge, leachable material within the filters, and absorption of atmospheric moisture. Millipore type HA filters lost an average of 0.31 ± 0.07 mg or 0.32% of their dry weight as leachable material when 6 liters of distilled water were filtered. About 165 ml were required to remove 50% of the total leachable material removed by 1000 ml. These filters absorbed moisture from the atmosphere very rapidly during the first minute of exposure and at a much slower rate thereafter. The leachable material contributed to moisture absorption. Desirable drying temperature and time for Millipore type HA filters was determined. Other filters were compared; recommendations for the use of these filters are given. [ABSTRACT FROM AUTHOR]