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Phosphate Treatment of Lead‐Contaminated Soil: Effects on Water Quality, Plant Uptake, and Lead Speciation
Author(s) -
Weber John S.,
Goyne Keith W.,
Luxton Todd P.,
Thompson Allen L.
Publication year - 2015
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2014.10.0447
Subject(s) - phosphorus , environmental chemistry , chemistry , soil water , water quality , riparian zone , effluent , phosphate , genetic algorithm , surface runoff , zoology , environmental science , environmental engineering , ecology , soil science , organic chemistry , habitat , biology
Water quality threats associated with using phosphate‐based amendments to remediate Pb‐contaminated soils are a concern, particularly in riparian areas. This study investigated the effects of P application rates to a Pb‐contaminated alluvial soil on Pb and P loss via surface water runoff, Pb accumulation in tall fescue ( Festuca arundinacea Schreb; Kentucky 31), and Pb speciation. An alluvial soil was treated with triple superphosphate at P to Pb molar ratios of 0:1 (control), 4:1, 8:1, and 16:1. After a 6‐mo reaction period, rainfall simulation (RFS) studies were conducted, followed by tall fescue establishment and a second set of RFS studies (1 yr after treatment). Results from the first RFS study (unvegetated) demonstrated that the total Pb and P concentrations in the effluents of 8:1 and 16:1 (P:Pb molar ratio) treatment levels were significantly greater ( p < 0.05) than the control. One year after P treatment and 6 mo after vegetation establishment, total P and Pb concentrations of the effluents from a second RFS decreased by one to three orders of magnitude. Total and dissolved P concentration in runoff from the 16:1 P:Pb treatment remained significantly greater than all other treatments. However, total Pb concentration in the runoff was comparable among the treatments. Phosphorus treatment also reduced Pb uptake into tall fescue by >55%. X‐ray absorption near‐edge structure spectroscopy data showed that pyromorphite [Pb 5 (PO 4 ) 3 OH,Cl,F] abundance ranged from 0% (control) to 32% (16:1 P:Pb; 1 yr after treatment) of the total soil Pb. Although P treatment stimulated pyromorphite formation, pyromorphite abundance was comparable between the P‐treated soils. These findings suggest that a 4:1 (P:Pb molar ratio) P treatment may be a sufficient means of reducing Pb bioavailability while minimizing concerns related to P loss in an alluvial setting.