Characterization of Soils and Saprolites from the Piedmont Region for WasteDisposal Purposes

摘要

There is great interest in using saprolite for on-site wastewater disposalpurposes in the Piedmont and Mountain regions of North Carolina. However, information regarding hydraulic properties and attenuation capacity of various saprolites for pollutants found in domestic wastewater is limited. Field and laboratory studies were initiated to assess characteristics of a number of soil-saprolite sequences in the Piedmont region. A laboratory soil column experiment was conducted to evaluate movement of 5 inorganic constituents of domestic wastewater through three different soils and their associated saprolites that were collected from Franklin, Orange and Wake Counties. Directional saturated hydraulic conductivities (K) and other physical and mineralogical properties at Bt (soil), B/C (transitional) and C (saprolite) horizons were measured at 3 different landscape positions (a ridge top, shoulder and ridge nose) over a Cecil soil mapping unit in Wake County (referred to as site number 1). In addition, the macropore network of the three horizons at each landscape position was assessed in the field. Samples collected from four different color zones around Mn oxide coated fractures (a type of macropore) at the shoulder position were also analyzed, and profiles for vertical K were obtained for the three landscape positions. At a second site in Wake County (referred to as site number 2), contributions of different types of water-conducting pores to water flow under saturated and unsaturated conditions were evaluated through thin section analysis.