Liming Characteristics of a High-Calcium, Dry Flue Gas Desulfurization By-product and its Effects on Runoff Water Quality

In 2013, only 37% of the 32 million Mg of flue gas desulfurization (FGD) by-products generated in the United States were reused beneficially. If FGD by-products could be used as a beneficial soil amendment, millions of megagrams may be diverted away from surface impoundments and landfills. The purpose of this research was to identify the liming characteristics of a high-Ca dry FGD (DFGD) by-product in comparison to a Class-C fly ash (FA) and reagent-grade CaCO3, and to evaluate the effects of land application to a managed grassland on runoff, plant, and soil quality. Liming characteristics were determined by measuring the calcium carbonate equivalence (CCE), degree of fineness (DOF) and calculating the effective neutralizing value (ENV). The DFGD by-product was land-applied to a managed grassland in May 2015 and runoff, plant, and soil samples were collected over a 12-mo period. The ENV of 79.4% for the DFGD by-product was lower (P \u3c 0.05) than that of reagent-grade CaCO3, but similar to the ENV of commercially available liming materials. The DFGD by-product was as effective as reagent-grade CaCO3 at raising soil pH when incubated at a rate equivalent to the soil’s lime requirement and more effective than reagent-grade CaCO¬3 when incubated at 2x the soil’s lime requirement. Seasonal flow-weighted mean Ni concentrations and seasonal V loads were 44.5 and 86.9%, respectively, greater (P \u3c 0.05) when amended compared to the unamended control during at least one season. One month after application, aboveground dry matter and tissue As, Se, Cr, Co, Hg, V, and U concentrations were between 53 and 471% greater in the amended treatment than in the unamended control. Trace element concentrations decreased to pre-application levels within six months. Results demonstrated that the high-Ca DFGD by-product used in this study is a viable liming material and has minimal effects on runoff and plant quality when applied at a rate of 9 Mg ha-1. Consequently, land application of high-Ca DFGD by-products may be a viable alternative to current disposal methods

The Potential Acidification of the Mulberry River, Arkansas

The Mulberry River is a 110 km long tributary of the Arkansas River in northwest Arkansas and has been designated as a National Wild and Scenic River since 1992. In 2008, the Mulberry River was added to the 303(d) list of impaired water bodies due to the low pH of a 14.6 km segment of the river which has since increased to 68.7 km. To date, there has been little research performed on the Mulberry River and long-term routinely sampled water quality data is unavailable. The objectives of this dissertation were 1) to evaluate changes in water quality of the Mulberry River and its tributaries over a 4-year period and 2) to evaluate the relationship between forest stand type (i.e., deciduous vs coniferous) and both stream and soil chemistry. Water samples were collected monthly from 11 locations on the Mulberry River and 10 of its tributaries from March 2015 until January 2019. Soil samples were collected from 10 locations throughout the watershed with adjacent deciduous and coniferous stands. Several different tests of soil acidity indicated in no significant differences between soil from beneath the deciduous and coniferous stands. Coniferous forest land use was not correlated with stream pH (P \u3e 0.05) neither was stream pH predicted (P \u3e 0.05; R2 \u3c 0.01) by coniferous forest land use. Trend analyses indicate that there have been significant decreases in specific conductance, total suspended solids, total organic C, total N, SO4, and flow-adjusted soluble Ca and Mg and a significant increase in Cl and total Al, Fe, and Na. Out of the 21 locations sampled, only three had significant decreases in pH suggesting that the watershed has not been acidified during the duration of this study. The decrease in specific conductance and several constituents as well as the increase in streamflow and precipitation throughout Arkansas implies that the watershed has become more dilute with time. The results of this research indicate that conifer growth is not a significant source of acidity and the watershed has not become more acidic over the last 4 years