David Lindbo

8 – Redoximorphic Features

Publisher Summary Redoximorphic features have been referred to by various terms over the past decades. The terminology used to describe redoximorphic features is derived from sedimentary petrology and soil micromorphology. Redoximorphic features are common in most soils where water saturation occurs and their presence is used extensively in making land use decisions. Although redoximorphic features are visible in the field with both the naked eye and a hand lens, micromorphological analysis can further enhance our understanding of how these features form and how to interpret them correctly. These interpretations are best made when supportive information such as water table and climatic data are available, but they can to a large extent be based on extensive micromorphological data correlating redoximorphic pedofeatures to environmental conditions.

A Method to Predict Soil Saturation Frequency and Duration from Soil Color

feature abundance. As a result, it has been difficult to extrapolate their saturation data to other sites to make Saturation frequency and duration must be estimated to determine specific interpretations regarding saturation frequency if a site is a jurisdictional wetland, and such data also aid in assessing sites for on-site waste disposal. This study developed a method to or duration. Later work has attempted to define the estimate saturation frequency and duration by calibrating redoximorrelationship between saturation duration and occurphic features to a 40-yr record of water table simulations in a catena rence of redoximorphic features, but because these studof Atlantic Coastal Plain soils in North Carolina. Thirteen plots were ies were short-term ( 3yr), the effects of saturation established along a toposequence with moderately well-drained frequency on morphology could not be addressed (Aquic Paleudults) and very poorly drained soils (Umbric Palea(Franzmeier et al., 1983; Megonigal et al., 1993; and quults) as end members. A hydrologic model (DRAINMOD) was Jacobs et al., 2002). calibrated for each plot. Redox potential measurements showed that Some land-use regulations require that frequency and an average of 21 consecutive days of continuous saturation was suffiduration of saturated conditions be determined to assess cient for Fe reduction to occur in the soils. Historic rainfall data were a soil’s suitability for a given use. For example, jurisdicused in the DRAINMOD model to estimate the number of times each plot was saturated for 21 consecutive days or longer in each tional wetlands must meet a standard for wetland hyyear of a 40-yr period. Redoximorphic features were significantly drology, which requires an area be saturated to the correlated with average number of saturation events computed to surface for at least 5% of the growing season with a have occurred at depths of 45, 60, 75, and 90 cm across all soils. frequency of at least 5 yr out of 10 (Environmental Relationships were linear and varied by depth when all soils were Laboratory, 1987). On-site wetland inspections to deteranalyzed as a single population. The r2 values for relationships between mine whether a site meets the wetland hydrology reredox depletions and saturation events were 0.85 for saturation quirement must be completed quickly to keep up with occurring during the growing season, and were 0.75 for saturation the demand. There is currently no technology known events occurring at any time during the year. These relationships to the authors that would enable a field scientist to allow prediction of the likelihood that a soil will saturate for 21 d determine whether a site affected by shallow ground by simply estimating the percentage of redoximorphic features at a given depth. water actually meets the saturation frequency and duration requirements for wetland hydrology during a single site visit. We hypothesized that rapid assessment of the freS color patterns that include low chroma or gray quency of soil saturation for specific durations may be colors are commonly used to predict where seasonal accomplished if the soil color patterns (redoximorphic saturation occurs in soils (Daniels et al., 1971; Bouma, features) were correlated with these hydrologic parame1983; Pickering and Veneman, 1984; Buol and Rebertus, ters. Testing this hypothesis requires that a hydrologic 1988; Veneman et al., 1998). Low chroma colors increase model first be calibrated on-site to simulate water table in abundance the longer a soil is saturated and chemilevels using rainfall as the major input variable. Once cally reduced (Vepraskas, 1999). Daniels et al. (1971) the model is calibrated for a specific soil, long-term (e.g., used a statistical model to compute water table levels 40 yr) rainfall data could then be read into the model in a toposequence of Paleudults and Paleaquults and to compute saturation duration and frequency for each then estimated water table levels during the course of depth in the soil. By correlating the historic data on an average year. Data were collected for a 2-yr period. saturation with the percentages of redoximorphic feaThey noted that as soils became saturated for longer tures in the soil, it should be possible to calibrate the periods the chroma of the Bt horizons decreased. Horipercentages of redoximorphic features to specific satuzons containing colors with chromas of 2 or less and ration durations and frequencies. If the statistical analyvalues of 4 or more were saturated from 10 to 50% of ses are successful, then we might be able to predict, for the year. Simonson and Boersma (1972) related faint example, that a soil having 40% redox depletions at a and distinct mottling to average durations of saturation depth of 60 cm is saturated for at least 21 d in 8 out of that were estimated for a 29-yr period. The studies of 10 yr. Once the redoximorphic features at one soil have Daniels et al. (1971) and Simonson and Boersma (1972) been calibrated in this way, they then can be used to were original, but they did not define a simple relationpredict saturation frequency and duration in similar soils ship between saturation frequency and redoximorphic where water table levels have not been measured. Vepraskas (2000) reported on a pilot study where this X. He, M.J. Vepraskas, and D.L. Lindbo, Dep. of Soil Science, Box approach was successfully applied to three soil plots. 7619, North Carolina State University, Raleigh, NC 2795; R.W. This study investigated the relationship between reSkaggs, Dep. of Biological and Agricultural Engineering, Box 7625, doximorphic feature percentage and saturation freNorth Carolina State University, Raleigh, NC 27695. Received 30 Apr. 2002. *Corresponding author (Michael_Vepraskas@NCSU.edu). Abbreviations: NSE, number of saturation events. Published in Soil Sci. Soc. Am. J. 67:961–969 (2003).

Soil Organic Matter

Publisher Summary This chapter discusses soil organic matter. Organic matter is universal to all soils. The form and distribution of soil organic matter is dependent upon a number of processes that may act independently or in concert. Most of these processes are related to the initial decomposition of the plant residues by a suite of soil fauna, and to the continued decomposition, transport and accumulation of the by-products. Descriptions of the forms, distribution and genesis of organic components in soils can range from quite simple to extremely complex. Micromorphological approaches to such descriptions are comparably varied. The most important issues that are faced are related to the effects of land-use change, global warming, pollution and invasive species on the soil environment. Because soil organic matter is the most dynamic of the soil components, effects of changing soil environment are often recorded first in the quality and distribution of organic matter.

Properties of iron oxides in streams draining the Loess Uplands of Mississippi

Abstract Iron oxide precipitates are abundant in small stream systems of NW Mississippi, USA especially during the wet winter months. The properties of these specific materials are unknown even though they have the potential to influence soil physical properties and adsorb chemical pollutants in sediment environments. Streamwater and associated precipitates were collected from 4 representative streams at Cedar Creek (CC), Lees Creek (LC), Spring Creek (SC), and Toby Creek (TC) during winter flow periods. Precipitate specimens were characterized for mineralogy, color, and solubility in oxalate (o), dithionite (d), and HNO 3 . Chemical composition of the water was dominated by Ca, Na, Mg, and K, in that order, at an average pH of 7.0. X-ray diffraction (XRD) and differential scanning calorimeter (DSC) data indicated that the precipitates were primarily poorly ordered ferrihydrite (CC, TC) and lepidocrocite (LC, SC). The Fe o /Fe d ratios were 0.40 (CC), 0.68 (LC), 0.66 (SC), and 0.67 (TC). Organic C contents were 80.6, 38.0, 63.0, and 51.3 g kg −1 for the same samples. Precipitate color was uniform among sites, averaging 6.7 YR 4.8/6.2. After oxalate extraction, redness increased slightly in the CC and SC specimens, and decreased in the others. Extraction with dithionite depleted the red color in all specimens, but had less effect on the CC and SC samples which retained hues at 7.9 and 7.3 YR, respectively. Dithionite extractable P equaled 1.02 (CC), 0.72 (LC), 0.56 (SC), and 0.99 (TC) g kg −1 . The results from this study indicated that: (1) the precipitates are either primarily poorly ordered ferrihydrite or lepidocrocite; (2) the solubility of ferrihydrite in both oxalate and dithionite is influenced by C contents; and (3) the redder, ferrihydrite specimens contain the greatest P concentrations.

Applying Soil Morphology to Long Term Acceptance Rate Determination

Abstract: Soil morphology and site conditions are used in many states to determine the suitability of a building lot for a decentralized wastewater treatment and dispersal system. Although rules in many states mention site and soil conditions, they are at times ambiguous or only assess whether the site can or can not be used for wastewater treatment and dispersal. Often the rules provide little guidance on the specific procedure for determining a final long term acceptance rate (LTAR) based on multiple soil and site conditions, relying on the discretion and experience of the field practitioner to determine the final LTAR. The end result is that two site evaluators can come up with vastly differing LTARs on the same site. Using the North Carolina rules for wastewater treatment and dispersal as a starting point we developed a standardized procedure to assign an LTAR. This procedure is based on principles of water and air movement in soil as well as expected treatment capacity. Each section of the rules that deals with a specific soil or site parameter was rated. The result is a step-by-step procedure that includes each parameter in the final LTAR determination. The procedure is reproducible from site to site and from practitioner to practitioner. Once the LTAR for the soil/site is determined it can be further adjusted based on wastewater strength, flows and other applicable factors related to expected performance.

Speaking the same language: A glossary for the decentralized wastewater treatment field

Onsite/decentralized terminology originated and evolved on the state or regional level in conjunction with regulatory or Agricultural Engineering Extension activities. Adapting terminology from one locale to match that used in another is increasingly cumbersome since resources originally developed to address local issues and inform consumers are now shared nationally. Significant advances from proprietary and academic research and development have resulted in a wide range of treatment options and best management practices in use nation wide. Several national initiatives are also underway to standardize industry practices, but inconsistent terminology is a barrier to acceptance of nationally-developed training materials and guidance documents. Ever-increasing interaction among industry sectors across the country now dictates the use of consistent vocabulary.

Wastewater Infiltration and Water Movement Around Trenches of Septic Systems

In designing septic systems it is often assumed that wastewater infiltration from the trenches into the soil and water movement away from the drainfield occurs uniformly through the soil in all directions. Soils, however, are heterogeneous and vary spatially in all directions. Wastewater infiltration and movement of water through the soil in the drainfield area of a number of actual and simulated septic systems with gravel-filled trenches installed in different soils were assessed. In one study, 56 tensiometers were installed on a 20- by 20-cm grid system perpendicular to the middle trench of three low-pressure pipe septic systems. The distance between the tensiometers in both horizontal and vertical directions was 20 cm. A series of observation wells were also installed in the trenches of these systems to evaluate infiltration rate. In another study, using a tracer dye and bromide, movement of water through the soil around the trenches of four simulated septic systems installed at three sites were assessed. Wastewater infiltration from the trenches into the soil varied along the length of the trenches as well as among different trenches. The equipotential lines generated from the tensiometer readings around the trenches showed that water flow from the trenches through the soil is neither symmetrical nor uniform. Assessment of the distribution patterns of tracer dye and bromide under the trenches of the four simulated drainfields indicated that preferential flow is the main mechanism for water movement when trenches are installed in a structured clayey Bt horizon. When trenches are installed in coarse textured materials above a clayey horizon in sloping areas, most of the water applied to the trenches move away from the area above the clayey Bt layer.

Ground Water Mounding Under Large Systems in Areas with Shallow Water Table

Large septic systems can significantly impact the local hydrology over and immediately around their drainfields. Water table fluctuations under the drainfield of two large septic systems installed in sandy soils in the Coastal Plain region of North Carolina were monitored for two years. The actual wastewater application rates for the two systems were approximately 1.2 and 1.7 cm/d. Three wells, each equipped with a pressure transducer were installed in the middle of a subdrainfield and outside the drainfield area of each system to measure water table elevation continuously. Other wells were installed in and around each drainfield for manually measuring water table. Neutron probe access tubes and time domain reflectometry (TDR) rods were also installed at various locations within each subdrainfield to measure soil water content. Rainfall data from the nearest weather station for each site were used for the study. In general, no significant change in water level elevation was observed as a result of wastewater application to the drainfields. Additionally, the water levels measured hourly in all the wells indicated that water table elevation did not show any appreciable change during days with no rainfall. The water table, however, was raised after major rainfall events, as well as following a few consecutive rainy days in the area. This shows that changes in the water table elevation were only related to the rainfall and not to the wastewater application. Lack of significant ground water mounding under the two systems is perhaps due to the high hydraulic conductivity of the relatively thick unconfined aquifer under their drainfields.

On-Site Wastewater Permit Nightmares or Easy Ways to Pay Tort Claims

Abstract: Environmental Health Specialists in North Carolina issue more than 50,000 Improvement Permits and Authorization to Construct Permits each year. The Environmental Health Specialists are employed by their respective county governments, but are trained and authorized by the North Carolina Department of Environment and Natural Resources, On-Site Water Protection Section to conduct soil and site evaluations and issue the appropriate permits. This system produces well trained individuals that are able to enforce state regulations on the local level. In the last five years problems have arisen, resulting in an alarming increase in the tort claims filed against the state and counties. A tort claim arises when an Environmental Health Specialist fails to act as a reasonable professional in performing his/her duties. In general this is documented by improper permitting of Improvement Permit/Authorization to Construct Permits that result in financial injury (i.e. system failure, permitting of unsuitable lots.). In 1995 tort claims paid was less than

Calibrating Hydric Soil Field Indicators to Long-Term Wetland Hydrology

15,000; this is compared to proposed claims of over