Laboratory and field tests were made to determine if porous ceramic cups collect representative samples of nitrate and phosphate from soil water. Substantial bias and variability were found. Some of the sources of sample bias were sorption, leaching, diffusion, and screening of phosphate ions by the cup walls. Sample variability of nitrate ions was strongly influenced by sampler intake rate, plugging, sampler depth, and type of vacuum system (which simulated different sampler sizes). These factors affect timing of sample collection and, because nutrient concentration in soil water is continually changing, they in turn affect sample concentration. These factors produced as much as a 60% range in sample concentration from eight samplers installed in a small uniform plot. Added to this variability is an unknown amount of bias representing the difference between the sample concentration and the average drainable soil‐water concentration. The many factors affecting the sample concentration together with the demonstrated variability and unknown bias make interpretation of sampler data difficult. To reduce sample variability, group samplers by intake rate, and use short sampling intervals, uniform sampler lengths, and the same initial vacuum for all samplers.

No abstract

A series of fiber glass probes spaced in sand‐packed compartments in a screened well point permits the collection of a number of discrete groundwater samples from predetermined depths in a single borehole.

A model was developed to group precipitation samples from any location into four strata that represent collections of similar chemistry. Logic and cation frequency were used to first define low‐ and high‐salt samples, and then regression analysis was used to define low‐ and high‐H samples. Low‐H concentrations ranged between 0 and 13 μeq/L. Hydrogen regressed on the sum of NO3 + SO4 showed two consistent equations: one for normal H concentrations and one for emission‐related, high‐H concentrations. Delta analysis (the change in concentration between group means) and analysis of regression residuals between ion pairs and a third common ion revealed strong correlations for H: NO3, H: SO3, NH4:SO4, and Na: Cl in low‐salt, highly acid precipitation samples. Hydrogen, SO4, NO3, and NH4 compose 95% of acid precipitation chemistry in the United States. Significant correlations for NH4: NO3 and all other ion pairs did not exist in samples from highly acid, low‐salt collections. Nitrate and SO4 carried H at average portions of 36 and 64%, respectively, regardless of H concentration. Variation in these portions of ±15% was site specific and not a function of H concentration.

Infiltration rate in a frozen Fayette silt loam soil under contiguous areas of natural deciduous forest, 25‐year‐old confierous plantation, and 6‐year‐old abandoned field vegetation was measured over the winter of 1969‐70 using tin can infiltrometers and a water‐ethylene glycol solution. The deciduous forest site had a natural soil profile; the conifer plantation and abandoned field sites were once cultivated. Prefreeze infiltration rate was similar for all cover conditions. In deciduous forest and abandoned field plots, soil freezing did not change the infiltration rate sharply until late winter when infiltrating snowmelt and rainfall froze and closed soil pores. In the conifer plantation, the infiltration rate was nearly zero in early winter due to an impermeable snow‐ice layer on the ground caused by snowmelt dripping from the conifer canopy. Because of large macropores, infiltration rates were high on the deciduous forest and abandoned field plots even when the frozen soil contained nearly 50% water by volume. Conifer plantations may thus contribute more surface run‐off than deciduous forest or abandoned fields during snowmelt and winter rains.