Managing phosphorus bioaccessibility is critical for the bioremediation of hydrocarbons in calcareous soils. This paper explores how soil mineralogy interacts with a novel biostimulatory solution to both control phosphorus bioavailability and influence bioremediation. Two large bore infiltrators (1 m diameter) were installed at a PHC contaminated site and continuously supplied with a solution containing nutrients and an electron acceptor. Soils from eight contaminated sites were prepared and pretreated, analyzed pretrial, spiked with diesel, placed into nylon bags into the infiltrators, and removed after 3 months. From XAS, we learned that three principal phosphate phases had formed: adsorbed phosphate, brushite, and newberyite. All measures of biodegradation in the samples (in situ degradation estimates, mineralization assays, culturable bacteria, catabolic genes) varied depending upon the soil's phosphate speciation. Notably, adsorbed phosphate increased anaerobic phenanthrene degradation and bzdN catabolic gene prevalence. The dominant mineralogical constraints on community composition were the relative amounts of adsorbed phosphate, brushite, and newberyite. Overall, this study finds that total phosphate influences microbial community phenotypes whereas relative percentages of phosphate minerals influences microbial community genotype composition.
Chemical form of phosphorus (P) in soils influences both plant accessibility and solute transport of P. Soil P speciation receiving inorganic and organic fertilizers is extensively studied to address a range of agronomic and environmental concerns. It is known inorganic P sources react over long time scales in soils, but relatively few studies have focused upon long-term P speciation changes in soils receiving organic amendments. This study was conducted to address this gap by providing detailed information on the speciation of P in agricultural soils from short-(2 yr) and long-term (11 yr) applications of liquid hog manure (LHM) and solid cattle manure (SCM) made at a field research site. Chemical speciation was performed with a combination of laboratory-based soil test P extraction methods and solid-state synchrotron-based techniques. There was clear evidence that initial phosphate minerals in the manures rapidly transform into new phases after short-term soil application. The X-ray absorption near edge spectroscopy results for SCM soil samples were consistent with high solubility (likely Mg-substituted) dicalcium phosphate minerals and phosphate (PO 4) adsorption species present after short-term period, whereas long-term SCM application resulted in transformation of soil phosphate into more crystalline calcium phosphate minerals. In contrast, phosphate speciation after short term of LHM application revealed predominantly magnesium phosphate and adsorbed P compounds. Soils under long-term LHM amendment still had phosphate speciation dominated by poorly crystalline dicalcium phosphate minerals. This suggests that the manure form plays a strong role not only in short-term plant availability but also in long-term P speciation.
Adsorption and precipitation reactions often dictate the availability of phosphorus in soil environments. Tripolyphosphate (TPP) is considered a form of slow release P fertilizer in P limited soils, however, investigations of the chemical fate of TPP in soils are limited. It has been proposed that TPP rapidly hydrolyzes in the soil solution before adsorbing or precipitating with soil surfaces, but in model systems, TPP also adsorbs rapidly onto mineral surfaces. To study the adsorption behavior of TPP in calcareous soils, a short-term (48 h) TPP spike was performed under laboratory conditions. To determine the fate of TPP under field conditions, two different liquid TPP amendments were applied to a P limited subsurface field site via an in-ground injection system. Phosphorus speciation was assessed using X-ray absorption spectroscopy, total and labile extractable P, and X-ray diffraction. Adsorption of TPP to soil mineral surfaces was rapid (< 48 h) and persisted without fully hydrolyzing to ortho-P. Linear combination fitting of XAS data indicated that the distribution of adsorbed P was highest (~ 30–40%) throughout the site after the first TPP amendment application (high water volume and low TPP concentrations). In contrast, lower water volumes with more concentrated TPP resulted in lower relative fractions of adsorbed P (15–25%), but a significant increase in total P concentrations (~ 3000 mg P kg soil) and adsorbed P (60%) directly adjacent to the injection system. This demonstrates that TPP application increases the adsorbed P fraction of calcareous soils through rapid adsorption reactions with soil mineral surfaces.Electronic supplementary materialThe online version of this article (10.1186/s12932-017-0046-z) contains supplementary material, which is available to authorized users.
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