INVESTIGATION OF SOILS IN A CREATED WETLAND NEAR HAYMARKET, VIRGINIA

Created wetlands are made to replace wetlands destroyed by human activity. Commonly these wetlands do not perform as well as their natural counterparts and the reasons for this are poorly understood. The North Fork Wetland Bank (NFWB) is a created wetland system that is approximately five years old and consists of two types of cells. Vernal pool cells in which all water in the system is theoretically derived from precipitation and a large overland flow cell in which all water is derived form precipitation and stream input. The area of the vernal pool wetlands is 25 acres and the overland flow system consists of 47 acres of wetlands and a 7 acre lake.

Several soil profiles from the overland flow cell of the NFWB were investigated to provide better understanding of the nature of materials used in this system. Several deep and shallow pits indicate that the stratigraphy of the soil in this cell consists of a reworked material approximately 30 cm thick that overlies a clay liner. This unit commonly consists of approximately 10-15 % clasts, 50% clay, 10-15% sand, and 20-30% silt. The unit is poorly sorted and Munsell colors of the soil matrix are variable and range from 10 YR 4/6 to 10 YR 3/4. Clasts are dominantly greenstones with lesser amounts of yellow-orange quartzite. Rock varnish is common on clasts and X-ray diffraction indicates it is dominated by poorly crystalline Mn-oxides and illite. Magnetite is also a common constituent in the silt and sand size fraction. The clay liner is approximately 75% clay, 15 % silt, 5% sand, and 5% clasts of variable size. Matrix material has a dominant Munsell color of Gley 1 4/5. Pits dug after significant rainfall indicate that a perched water table occurs at 10-12 cm depth in some areas and appears to be related to clay-rich regions in the matrix.

Results thus far indicate that the soil texture and mineralogy of the system is complex and may provide insight in explaining variation in bulk physical and chemical properties.