Phosphorus leaching in sandy outwash soils following potato-processing wastewater application.
Land application of wastewater presents potential for ground water pollution if not properly managed. In situ breakthrough tests were conducted using potato (Solanum tuberosum L.)-processing wastewater and a Br tracer to characterize P leaching in seasonally frozen sandy outwash soils. In the first test, P and Br breakthrough were measured in a 7-m deep well following wastewater [2.94 mg L(-1) total P (TP); 280 mg L(-1) Br] application at the site that had 13.1 mg water-extractable P (WEP) kg(-1)and 94.4 mg Bray-1 P kg(-1). Bromide was detected in the well after approximately 0.4 pore volumes, but there was no P break-through after 7 pore volumes. In the second breakthrough test, wastewater containing 3.6 mg L(-1) TP and 259 mg L(-1) Br was applied on 1.5-m deep lysimeters at low (0.8 mg WEP kg(-1); 12.1 mg Bray-1 P kg(-1)) and high soil test P sites (104 mg WEP kg(-1); 585 mg Bray-1 P kg(-1)). Leachate TP concentration during the test remained constant (0.04 mg L(-1)) at the low P sites but increased from approximately 3.5 to 5.6 mg L(-1) at the high P sites. These results indicate no P leaching in low P soils, but leaching in high P soils, thus suggesting that most of the P leached at the high P sites was mainly due to desorption and dissolution of weakly adsorbed P from prior P applications. This was consistent with P transport simulations using the convective-dispersive equation. We conclude that P concentration in land-applied wastewater should be regulated based on soil test-P level plus wastewater P loading.
Zvomuya
Francis
F
Agriculture and Agri-Food Canada, Lethbridge Research Center, P.O. Box 3000, 5403-1st Ave. S., Lethbridge, AB T1J 4B1, Canada.
Gupta
Satish C
SC
Rosen
Carl J
CJ
D000327:Adsorption; D001966:Bromine / Q000032:analysis; D010758:Phosphorus / Q000032:analysis; D012621:Seasons; D012822:Silicon Dioxide; D011198:Solanum tuberosum; D014865:Waste Disposal, Fluid / Q000379:methods*; D014872:Water Movements; D014873:Water Pollutants / Q000032:analysis*
D014873:Water Pollutants; D010758:Phosphorus; D012822:Silicon Dioxide; D001966:Bromine