Runoff of metals from alum-treated horse manure and municipal sludge

Land application of organic soil amendments can increase runoff concentrati ons of metals such as Fe and Zn, metalloids such as B and As, and non-metal s such as P and S that have the potential for causing adverse environmental impacts. Aluminum sulfate, or alum (Al-2(SO4)(3).(14H(2)O), can reduce con centrations of some materials in runoff from sites treated with organic ame ndments. The objectives of this study were to (a) quantify concentrations o f selected constituents (Al, As, B, Ca, Cd, Co, Fe, K, Mg, Mn, Mo, Na, P, P b, S, Se, Ti, and Zn) in runoff from plots treated with horse manure (mixed with stall bedding) and municipal sludge, (b) assess runoff quality effect s of alum addition to those treatments, and (c) determine time variations i n concentrations of the constituents. Horse manure and municipal sludge wer e applied to twelve 2.4 by 6.1 m fescue plots (six each for the manure and sludge). Alum was added to three of the manure-treated and three of the slu dge-treated plots. Simulated rainfall (64 mm/h) was applied to the 12 treat ed plots and to three control (no treatment) plots. The first 0.5 h runoff was sampled and analyzed for the constituents described above. Addition of manure or sludge had no effect on runoff concentrations of the majority of constituents. In some cases (e.g., Al, As, Fe, Zn), however, concentrations were near or in excess of threshold values recommended for marine wildlife protection. Alum addition increased runoff of Al, Ca, K, and S, due likely to its composition and by the addition of lime to counteract the acidity o f alum. Concentration decreases of more than 50 percent were noted for P fo r the horse manure treatment. No alum effect was detected for P in runoff f rom the sludge-treated plots, possibly due to relatively stable P forms in the sludge. Runoff concentrations of Al, As, Fe, K, Mn, and P followed an a pproximately first-order decline with respect to time. Runoff concentration s of Ca and S, however, peaked during the second runoff sample (four minute s following initiation of runoff), suggesting that differences in mobility and/or transport mechanisms exist among the materials investigated.