Soil Properties, Irrigation Water Quality, and Soil Moisture Level Influences on the Movement of Nickel in Sewage Sludge‐Treated Soils

Abstract

AbstractA column study was conducted to assess the effects of soil properties, irrigation water quality, and soil moisture level on the movement of Ni in sewage sludge‐treated soils. Surface layer samples of six soil series were packed into 24 columns, 10.2 cm in diameter and 110 cm in length. An air‐dried, anaerobically digested sewage slude was mixed into the top 15 cm of soil at a rate of 300 Mg ha−1. The columns were maintained at moisture levels of saturation and unsaturation (16.7 kPa tension) and leached with two waters of different quality. The unsaturated columns were irrigated about every 12 d with 5.08 cm of water for 13 months. The saturated columns were leached for 7 months. At the termination of the experiment the columns were cut open and the soil sectioned into 3‐cm intervals the entire length of each column. Samples were extracted with water and 4 M HNO3 and analyzed for chemical constituents. Irrigation water quality did not affect the amount of Ni leached from the sludge‐amended soil layer nor the depth of Ni movement. Mass balance calculations showed that an average of 3.3% of sludge‐applied Ni leached from the sludge‐amended soil layer of the saturated columns compared to 10.7% for the unsaturated columns. An average of 96.7% of sludge‐applied Ni remained in the sludge‐amended soil layer of the saturated columns compared to 89.3% for the unsaturated columns. For the saturated columns an average of 74.9% of sludge‐applied Ni leached from the sludge‐amended soil layer was accumulated in the 0‐ to 3‐cm soil interval compared to 46.5% for the unsaturated columns. Nickel movement below the sludge‐amended soil layer for the saturated columns ranged from 3 to 15 cm with an average of 9 cm compared to a range of 3 to 45 cm and an average of 18 cm for the unsaturated columns. Correlation and regression analysis indicated that pH and soil texture were the soil properties that best predicted the depth of Ni movement.