| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
a Agricultural and Biological Engineering Department, Pennsylvania State University, University Park, PA 16802
b Soil and Water Science Department, University of Florida, Gainesville, FL 32611
* Corresponding author (hae1{at}psu.edu)
Received for publication December 9, 2004.
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
|---|
Abbreviations: BPR, biological phosphorus removal • PAN, plant available nitrogen • PP, particulate phosphorus • PSC, phosphorus source coefficient • TDP, total dissolved phosphorus • TP, total phosphorus • WEP, water-extractable phosphorus
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
|---|
A recent survey by Shober and Sims (2003) found that 24 states have existing regulations to limit biosolids application rates based on P levels in the soil. These states typically have established numerical environmental thresholds of soil test P levels beyond which biosolids application is prohibited. However, the current consensus among states is that a comprehensive approach using P site indices is a more effective way to identify agricultural fields vulnerable to P loss. These P site indices evaluate the relative risk to P loss based on site characteristics influencing P transport, the type of P source applied, and various crop and management practices (Lemunyon and Gilbert, 1993; Leytem et al., 2004). According to Sharpley et al. (2003), 47 states have adopted a P index approach. Although efforts so far have targeted manures and commercial fertilizers, P-based management will likely apply to all land-applied residuals including biosolids. Relatively few states have explicitly addressed biosolids, despite the prevalence of land application for biosolids disposal. This is unfortunate since the solubility, bioavailability, and transport potential of P vary significantly among biosolids types (Leytem et al., 2004; Brandt et al., 2004). Coale et al. (2002) predicted that P indices will be deployed as regulation long before being objectively validated. Quantifying P losses from application of biosolids to agricultural land is critical to promote scientifically sound P management policies.
Recent studies have used simulated rainfall onto packed soil boxes and field plots to evaluate P transport in surface runoff (Kleinman and Sharpley, 2003; Kleinman et al., 2004). Runoff dissolved P concentrations from simulated rainfall have been found to be correlated to the water-extractable phosphorus (WEP) content of the organic P source (Kleinman et al., 2002b; Brandt and Elliott, 2003). The WEP content of manures and biosolids treated with Al and Fe salts or by-products is lower than their untreated counterparts (Codling et al., 2000; Elliott et al., 2002; Sims and Luka-McCafferty, 2002). Penn and Sims (2002) found that biosolids containing high amounts of Fe consistently had the lowest WEP and exhibited the lowest runoff dissolved P when added to soils. Besides metal salt additions, other processes used in wastewater treatment and biosolids generation influence biosolids P solubility and runoff potential (Penn and Sims, 2002; Brandt et al., 2004).
The objective of this study was to determine P levels in runoff from soil amended with biosolids and dairy manure under simulated rainfall. Selected biosolids represented a wide range of materials routinely applied to agricultural soils. Most simulation studies (Penn and Sims, 2002; Kleinman et al., 2004; Leytem et al., 2004) employ a common total P application rate; however, this study examined P loss from organic P sources applied at a common plant available N rate, consistent with biosolids recycling practice. A further objective was to provide quantitative evidence for the use of weighting coefficients in P site assessment indices to reflect differences in P solubility of organic amendments.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
|---|
|
Total Al, Fe, Ca, and P of the P sources was determined by acid digestion followed by elemental analysis via ICP using USEPA Methods 3051 and 6010, respectively (USEPA, 2000). Total N was determined by combustion at 1100°C using an Elementar (Hanau, Germany) CNS Analyzer. Solids content (103–105°C, 15 h) and pH (1:2 P source to distilled water) were determined by standard methods. All analyses noted above were performed in duplicate and rerun when results differed by more than 15%.
For WEP analysis, distilled and deionized water was added to 0.5 g (dry weight equivalent) of P source (as received) to give a 1:200 solid to solution ratio. Samples were agitated for 1 h at room temperature (end-over-end shaker at approximately 15 rpm), centrifuged (15 min at approximately 1250 rpm), and vacuum-filtered through prewetted 0.45-µm filter paper. Samples were prepared for ICP analysis by adding 0.5 mL HCl (1:1) to 24.5 mL of filtrate. Two replicates of WEP extractions were performed.
All P sources were applied to the soil trays at a rate equivalent to 134 kg PAN ha–1, a typical recommendation for corn in Pennsylvania. For the biosolids, agronomic N availability was based on state regulatory prescriptions for ammonia availability and organic N mineralization. Dairy manure N availability was based on recommendations provided in Beegle (2002). The resulting P application rates ranged from 122 (dairy manure) to 555 (Syracuse N-Viro biosolids) kg P ha–1 (Table 2).
|
Rainfall Simulation Experiment
The rainfall simulation followed the National Phosphorus Research Project indoor runoff box protocol (National Phosphorus Research Project, 2001). Stainless steel runoff trays (20 x 100 x 7.5 cm deep) were packed with 5 cm of the soil and the P sources were uniformly applied to the surface of the soil. Three trays were prepared for each treatment and three trays with unamended soils served as controls. The trays were first saturated until ponding was observed and the rainfall events were conducted 3 and 5 d after the initial wetting. Trays were sloped at 3% and rainfall was delivered at 71 mm h–1. For each event, the initial 30 min of runoff was collected and a subsample was immediately filtered (0.45 µm) and acidified (pH < 2). Total dissolved phosphorus (TDP) was determined on the filtered samples by ICP. Total phosphorus (TP) was measured on the unfiltered runoff samples by ICP following digestion using USEPA Method 3051 (USEPA, 2000). The difference between TP and TDP for any sample was assumed to represent particulate phosphorus (PP). Two rainfall-runoff simulations were performed, but discussion focuses on the first rainfall event since most P is lost in the initial rainfall event for biosolids-amended soils (Sims et al., 2003). Since differential effects of P sources are generally the same based on runoff P loads (mg) or concentrations (mg L–1) (Kleinman et al., 2002a), we have, like other recent rainfall simulation studies (Kleinman and Sharpley, 2003), confined the discussion to runoff P concentrations.
|
RESULTS AND DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
|---|
Although nutrient content, physical properties, and chemical constituents differ because of various wastewater and stabilization processes (Table 2), the biosolids used in this study are typical of those produced nationally and applied to agricultural land (USEPA, 1995). The solids content ranged from dewatered moist "cake" materials (13–27%) to heat-dried products (>90%). Mean total P content for the biosolids was 23 g kg–1, in close agreement with median P of 22 g kg–1 reported by Stehouwer et al. (2000) for all biosolids submitted during 1997 to the Penn State Agricultural Analytical Services Laboratory. Lower concentrations of P in Danville limed cake (DL) and Syracuse N-Viro (SN) reflect dilution from addition of lime and alkaline by-products. The WEP levels in the biosolids were typically below 1 g kg–1, with the BPR-produced Largo materials being significantly higher. The Al and Fe contents were variable, reflecting additions of Al- and Fe-salts in wastewater treatment and solids processing or, in the case of Philadelphia cake (PC), the discharge of Fe-based water treatment residuals to sanitary sewers. The TP and WEP of the dairy manure fall within the range of values previously reported (Sharpley and Moyer, 2000; Brandt et al., 2004).
Phosphorus Source Effects on Runoff Phosphorus
The effect of P sources on TDP and TP concentrations in runoff followed a similar trend for the first (Fig. 1a)
and second rainfall events (Fig. 1b). The P concentrations in runoff were generally lower for the second event, however. Other studies have documented that total and dissolved P in runoff decreased with successive rainfall events following surface application of livestock manures (Sharpley, 1997) and biosolids (Rostagno and Sosebee, 2001; Penn and Sims, 2002). For biosolids-amended field plots, Sims et al. (2003) found the initial event accounted for 52 to 73% of the total runoff P collected over four rainfall events.
|
Although the dairy manure (DM) had the lowest total P rate (122 kg P ha–1), it had greater TDP than all biosolids except the Largo cake and pellets (LC, LP), and the Baltimore Patapsco pellets (PB). The generally greater P concentration for dairy manure compared with biosolids was shown previously where the P sources were all applied at 100 kg P ha–1 (Brandt and Elliott, 2003). In this study, the lower water solubility of the P in most biosolids offset the higher total P application rates relative to the dairy manure. The TDP of the PB was statistically comparable with the dairy manure treatment, despite a 61% greater total P application rate for PB. Notably, the TP and TDP for six of the biosolids treatments (UC, DC, DL, BR, PC, SN) applied at 154 to 555 kg P ha–1 were not statistically different from the control soil treatment (Fig. 1). Elsewhere, Withers et al. (2001) reported that P in runoff from biosolids-treated field plots was not significantly different from the control plot.
The Largo BPR materials (LP and LC) produced statistically greater TDP and TP than the dairy manure treatment (Fig. 1). As a category, BPRs have the greatest WEP values among biosolids types (Brandt et al., 2004). The WEP values for the LP and LC biosolids were 4.55 and 6.76 g kg–1, respectively. The greater WEP values of the LC and LP coupled with the higher total P application rates to meet the common PAN requirement (Table 2) resulted in greater TDP compared with the dairy manure (WEP = 3.41 g kg–1). However, the low WEP for most biosolids (WEP < approximately 1 g kg–1) suggests lower P runoff potential compared with typical livestock manures, assuming biosolids and dairy manure have no effect on runoff amount. Penn and Sims (2002) also found that biosolids produced by treatment of wastewater using biological nutrient removal exhibited the greatest TDP in runoff from rainfall simulation experiments.
The Danville cake and limed biosolids (DC and DL) exhibited TDP and TP concentrations that were not statistically different (Fig. 1) where P application rates were nearly identical (Table 2). Other studies have generally found that P solubility is greater in soils amended with limed biosolids, at least relative to Fe- or Al-dominated biosolids systems (Penn and Sims, 2002). Jokinen (1990) assessed the influence of treatment process on extractable soil P in biosolids-amended soils and concluded that, while Al-sludges tended to reduce P solubility, Ca-sludge increased soluble P values in soils. Soon and Bates (1982) reported that the extractability of P from soils amended with chemically treated, anaerobically digested sludges followed the order: Ca-sludge >> Fe-sludge 
Al-sludges. The presence of lime in biosolids treated with metal salts tended to result in higher water soluble P in the amended soils (Maguire et al., 2000). Leytem et al. (2004) suggested that the higher solubility was due to the release of Ca–P complexes in response to the acidity of the amended soils. Such a mechanism would not apply to our study since the materials were not incorporated into the soil. In this case, the similar runoff P concentrations from the limed and unlimed Danville biosolids (Fig. 1) reflects the nearly equal WEP values (Table 2).
The Syracuse N-Viro (SN) had the greatest total P application rate (555 kg P ha–1), but resulted in negligible soluble P in runoff (Fig. 1). This was a reflection of the extremely low WEP concentration (0.01 g kg–1) of the N-Viro material (Table 2). Richards et al. (1997) attributed the low extractability and mobility of P in the Syracuse N-Viro product to P precipitation reactions occurring at elevated pH and Ca levels. Advanced alkaline stabilization (e.g., the N-Viro process) involves mixing biosolids with large quantities of alkaline materials so that the mixture is dried and pasteurized though heat generation. Although not statistically different (p = 0.05), the mean TDP and TP concentrations of the SN treatment were lower than the control treatment. Maguire et al. (2000) suggested that some biosolids increase the P sorption capacity of the soils and thus reduce P into runoff and drainage waters.
Treatment of the dairy manure with Al (DMA) or Fe (DMF) reduced P concentrations in runoff by about one-half compared with the unamended manure (Fig. 1). This reduction likely reflected the lower WEP concentrations of the amended dairy manure (Table 2). Alum additions to poultry manure have been shown to reduce runoff P (Moore et al., 1999). Here, we demonstrate that TDP concentrations in runoff can potentially be reduced by adding Al and Fe salts to materials such as dairy manure that have high concentrations of water-soluble P.
The importance of P-source Al and Fe content is further illustrated in Fig. 2 , which shows that the TDP levels for the first runoff event were consistently lower when the total molar Al + Fe content of the P sources was high. The critical role of Al and Fe in determining P solubility and release from biosolids-amended soils has been documented previously (Maguire et al., 2001; Brandt and Elliott, 2003). Note that several materials with molar Al + Fe contents about 0.3 to 0.4 had widely varying TDP concentrations. While very high Al + Fe contents may result in low runoff TDP, other factors (P loading rate, wastewater treatment, and solids processing) also influence susceptibility to P loss.
|
A positive correlation between runoff dissolved P and application rate (Kleinman and Sharpley, 2003) is logical for a given P-source type since the amount of soluble P available to runoff water is dependent on the application rate. Such a relationship should not necessarily hold for a broad range of P sources where the potential to release P into runoff water is highly variable. Figures 3a and 3b show the TDP and TP concentrations in runoff for Rainfall Event 1 for all 14 treatments (10 biosolids, 3 manures, and 1 control) as a function of the total P application rate (kg ha–1). Clearly, there is no positive correlation between runoff P and the total P application rate. The Syracuse N-Viro treatment had the highest total P application rate (555 kg ha–1), but the lowest TDP concentrations in runoff (<0.1 mg L–1). There were seven biosolids types with similar total P applications rates (approximately 180–220 kg ha–1), but the mean runoff TDP values ranged from <1 to >20 mg L–1 (Fig. 3a). Others have also shown that biosolids applied at the same total P rate exhibit significantly different runoff P losses (Penn and Sims, 2002; Brandt and Elliott, 2003; Sims et al., 2003).
|
|
Figures 5a and 5b show that TDP and TP are strongly correlated with total P application rates for multiple sources when multiplied by the respective PSC values. Data clearly illustrate that runoff P losses from most biosolids (8 of 10) are less than from dairy manure (DM), despite greater total P application rates for the biosolids. The BPR biosolids (LC and LP) had greater total P application rates than the DM (Table 2), but also exhibited high concentrations of TDP and TP in runoff. In the current Pennsylvania P index, dairy manure and BPR biosolids both have PSC values of 0.8. The data point for Philadelphia cake (PC) does not fit well in the correlation. This material has exceptionally high Fe (72.3 g kg–1) for biosolids because Fe-based water treatment residuals are disposed into the sanitary sewers in Philadelphia. Such high Fe causes the WEP to be very low (0.19 mg kg–1), which translates into low potential for P loss. The PSC used in this correlation was 0.3 for conventionally treated biosolids because no category currently exists for "high Fe" biosolids in the Pennsylvania P index. The results of Leytem et al. (2004) suggest that biosolids containing high levels of Fe should have lower PSC values than conventionally treated materials.
|
|
CONCLUSIONS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
|---|
Findings of this and other (Leytem et al., 2004) studies confirm the need to incorporate weighting coefficients into P site indices to reflect the portion of total applied P susceptible to off-site transport. Of the 41 state P indices evaluated by Sharpley et al. (2003), only 9 states (Arkansas, Delaware, Florida, Georgia, Louisiana, Maryland, Pennsylvania, Tennessee, and Virginia) include an estimate of the availability or solubility of the P applied to the site. Of these states, not all make specific reference to biosolids or, if they do, a single coefficient is used for all types of biosolids. If P index use is confined to one type of P source with relatively constant WEP, inclusion of PSC in the index is less important. For biosolids and treated manures, however, the susceptibility of P to leaching and runoff is so variable that the ability of a P index without PSCs to accurately predict site vulnerability risk is compromised. Moreover, unless the variable and typically lower solubility of P in biosolids is taken into account, the potential for P loss from biosolids application fields will likely be overestimated by site index assessment tools.
|
ACKNOWLEDGMENTS |
|---|
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONSREFERENCES |
|---|
Related articles in JEQ:
This article has been cited by other articles:
|
|
 |
|
  S. L. Chinault and G. A. O'Connor Phosphorus Release from a Biosolids-Amended Sandy Spodosol J. Environ. Qual., May 1, 2008; 37(3): 937 - 943. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Agyin-Birikorang, G. A. O'Connor, and S. R. Brinton Evaluating Phosphorus Loss from a Florida Spodosol as Affected by Phosphorus-Source Application Methods J. Environ. Qual., May 1, 2008; 37(3): 1180 - 1189. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Agyin-Birikorang and G. A. O'Connor Lability of Drinking Water Treatment Residuals (WTR) Immobilized Phosphorus: Aging and pH Effects J. Environ. Qual., May 25, 2007; 36(4): 1076 - 1085. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Franklin, C. Truman, T. Potter, D. Bosch, T. Strickland, and C. Bednarz Nitrogen and Phosphorus Runoff Losses from Variable and Constant Intensity Rainfall Simulations on Loamy Sand under Conventional and Strip Tillage Systems J. Environ. Qual., May 7, 2007; 36(3): 846 - 854. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. A. Ippolito, K. A. Barbarick, and K. L. Norvell Biosolids Impact Soil Phosphorus Accountability, Fractionation, and Potential Environmental Risk J. Environ. Qual., April 5, 2007; 36(3): 764 - 772. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. L. Shober and J. T. Sims Integrating Phosphorus Source and Soil Properties into Risk Assessments for Phosphorus Loss Soil Sci. Soc. Am. J., March 12, 2007; 71(2): 551 - 560. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Agyin-Birikorang, G. A. O'Connor, L. W. Jacobs, K. C. Makris, and S. R. Brinton Long-Term Phosphorus Immobilization by a Drinking Water Treatment Residual J. Environ. Qual., January 9, 2007; 36(1): 316 - 323. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. L. Shober, D. L. Hesterberg, J. T. Sims, and S. Gardner Characterization of Phosphorus Species in Biosolids and Manures Using XANES Spectroscopy J. Environ. Qual., October 27, 2006; 35(6): 1983 - 1993. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. A. Elliott, R. C. Brandt, P. J. A. Kleinman, A. N. Sharpley, and D. B. Beegle Estimating Source Coefficients for Phosphorus Site Indices J. Environ. Qual., October 27, 2006; 35(6): 2195 - 2201. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. A. Vadas and P. J. A. Kleinman Effect of Methodology in Estimating and Interpreting Water-Extractable Phosphorus in Animal Manures J. Environ. Qual., May 31, 2006; 35(4): 1151 - 1159. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| The SCI Journals | Agronomy Journal | Crop Science | |||
| Vadose Zone Journal | Journal of Plant Registrations | ||||
| Journal of Natural Resources and Life Sciences Education |
Soil Science Society of America Journal |
