Transport of PPCPs and Veterinary Medicines from Agricultural Fields

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Chapter 10

Transport of PPCPs and Veterinary Medicines from Agricultural Fields following Application of Biosolids or Manure Edward Topp,*,1 Chris D. Metcalfe,2 Alistair B. Boxall,3 and David R. Lapen4 1Agriculture

and Agri-Food Canada, 1391 Sandford Street, London ON, N5V 4T3 Canada 2Worsfold Water Quality Centre, Trent University, Peterborough ON, K9J 7B8 Canada 3EcoChemistry Team, University of York, Heslington, York, United Kingdom 4Agriculture and Agri-Food Canada, 960 Carling Ave., Ottawa ON, K1A 0C6 Canada *[email protected]

Biosolids from municipal treatment plants, and manure from livestock or poultry production are frequently used as fertilizer in crop production. These materials can contain human or veterinary pharmaceuticals and organic microconstituents that can pose a threat to the environment or to human health should they be transported to surface water or groundwater. Here, we consider field experiments defining the significance and mechanisms of transport of pharmaceuticals and personal care products (PPCPs) and veterinary medicines into runoff or into tile water. An emphasis is placed on experimental and analytical challenges, key rate controlling factors governing the fate of selected PPCPs, and the toxicological significance of mass loads and maximum aqueous concentrations of the exported residues. Information is provided provided on better management practices that reduce the risk of exposure after field applications of biosolids and manure.

© 2010 American Chemical Society Halden; Contaminants of Emerging Concern in the Environment: Ecological and Human Health Considerations ACS Symposium Series; American Chemical Society: Washington, DC, 2010.


Introduction Trace concentrations of various pharmaceuticals and personal care products (PPCPs) and veterinary medicines have been widely detected in surface and groundwater. The health risks to humans and wildlife exposed to these chemicals is of some scientific and regulatory concern (1). The potential sources of environmental exposure to PPCPs include effluents from sewage treatment plants, leakage from septic systems and landfills, discharges from pharmaceutical manufacturing facilities and hospitals, and transport from land that has been irrigated with wastewater or that has been fertilized with municipal biosolids, or sewage sludge (2). Veterinary medicines may enter the environment from the application of manures and slurry, from direct excretion by pasture animals, spillage from the treatment of animals for ectoparasites, or from treatments used in aquaculture (3). Biosolids and manures are a valued source of nutrients for crop growth, and these materials are commonly used as a fertilizer in many agricultural areas worldwide. In this context, our research has focussed on characterizing the risk of contamination of adjacent surface or shallow ground water with PPCPs by evaluating the concentrations and mass transfer of PPCPs from land following the application of municipal biosolids or animal manure. This chapter gives an overview of our experimental approaches, our results that characterize the transport of selected PPCPs via key exposure pathways, and our observations within the context of assessing and managing the risk of contamination of aquatic resources from the agricultural use of these fertilizers.

Considerations and Objectives for Field Experiments Biosolids and manures are typically applied as a slurry (total solids content usually 20%). The characteristics of solid and slurry material differ in ways that strongly influence the potential for transport of PPCPs following their application to soil. Slurry amendments applied to unsaturated soil will rapidly move into soil pores, ensuring contact with soil constituents such as organic matter and soilborne microorganisms that may, respectively, augment sequestration and accelerate biodegradation. In contrast, PPCP mobilization from aggregate materials (dewatered or solid waste products) to the adjacent soil environment may be limited by restricted diffusion of PPCPs out of the solid aggregates, and delayed physical breakdown of aggregates as a result of aggregate size and consistency. Slurry amendments behave as liquids when applied, and therefore can entrain PPCPs within and over the soil at the time of application. We have evaluated and contrasted the transport of PPCPs carried in both solid and slurry material. For both slurry and solid amendments, the mode of land application and product placement in or on the soil surface will strongly control transport, biodegradation, and sequestration potential. A key element of responsible land application therefore is maintaining the applied material and associated contaminants in the rooting zone away from groundwater, artificial drainage systems, and surface water sources. These practices will permit sorptive and degradative processes that sequester and dissipate residues, attenuating off-site 228 Halden; Contaminants of Emerging Concern in the Environment: Ecological and Human Health Considerations ACS Symposium Series; American Chemical Society: Washington, DC, 2010.


movement. This can be accomplished by using better management practices (BMPs) for land application that include judicious rates of application, tillage to incorporate material into the soil and disrupt continuous macropore networks, and application of material during time periods when transport potential is low. Thus, we have systematically investigated the impact of various BMP options on the transport potential of PPCPs. Tile drainage systems (artificial subsurface drainage) are ubiquitous in many agricultural regions that require soil drainage to foster crop production. Tile drains represent a particularly efficient means of transporting agricultural pollutants in the tile/groundwater system off site to adjacent surface water systems. Solutes can be transported to tiles at high velocity through macropores following heavy rainfall or following heavy application rates of slurry. Under these circumstances there is little contact time with the soil matrix, reducing or eliminating sorptive and degradative processes that would otherwise retard and reduce mass fluxes. Thus, the objectives of some of our field experiments has been to evaluate the off-site movement of PPCPs via tile flow. Overland flow from fertilized land, particularly if it occurs shortly after application is another high risk transport pathway. Such a scenario will arise when saturated sloping soils receive precipitation in excess of the infiltration rate. Thus we have undertaken a series of experiments using artificially applied precipitation to promote runoff drainage shortly after the application of a commercial rate of dewatered biosolids. PPCPs may also leach through the soil profile down to groundwaters. For example, in a recent national reconnaissance study in the US (4), concentrations of pharmaceuticals and other organic wastewater contaminants were characterized at 47 groundwater sites. In this survey, among 65 analytes targeted, 35 were detected at least once and 81% of the sites were found to show detectable levels of PPCPs. The most commonly detected pharmaceutical was the sulfonamide antibiotic, sulfamethoxazole, which is a highly water soluble compound used in both human and veterinary medicine. Over the past ten years, we have performed a range of field and semi-field experiments to understand the movement of PPCPs from the soil surface down to groundwaters. The results of these studies are also being used to validate modelling approaches for predicting movement to groundwaters in the absence of experimental monitoring data. One of the challenges associated with these types of studies is the analysis of PPCPs and veterinary medicines in environmental matrixes (i.e. water, soil, biosolids, manure). Unlike more persistent contaminants, such as PCBs and brominated flame retardants, PPCPs and veterinary medicines are typically water soluble and in many cases are present in ionic form in the environment. These chemical characteristics make it difficult to extract the target analytes from environmental matrixes without co-extracting many organic constituents along with the compounds of interest. These co-extractives introduce “matrix effects” that complicate the analytical approach. Since PPCPs and veterinary medicines are typically not very volatile, traditional analytical approaches, such as gas chromatographic separation and detection by mass spectrometery (i.e. GC-MS) cannot be applied, and instead, liquid chromatography with tandem mass spectrometry (i.e. LC-MS/MS) is the most common analytical approach. These 229 Halden; Contaminants of Emerging Concern in the Environment: Ecological and Human Health Considerations ACS Symposium Series; American Chemical Society: Washington, DC, 2010.


LC-MS/MS systems must be capable of detecting low part per billion or part per trillion concentrations of the analytes in the small samples of water (i.e. 50-200 mL) or solid matrixes (i.e. 0.5 – 2 g dry weight) that are typically collected for field experiments or in monitoring studies. When extracting PPCPs and veterinary medicines from aqueous matrixes (e.g. runoff, tile drainage), the samples are typically filtered or centrifuged to remove suspended particulates before extraction using solid phase extraction cartridges. Therefore, any target analytes adsorbed to suspended particulates will be lost prior to extraction, leading to underestimates of the mass transport of these chemicals from agricultural fields. Our studies have shown that the total mass of highly water soluble compounds associated with particulate material is negligible (5). However, for less water soluble compounds, such as the active ingredients in antibacterial soaps (i.e. triclosan, triclocarban), our studies have shown that transport in the particulate fraction may contribute significantly to mass transfers from agricultural fields (6). Therefore, care must be taken to extract both particulate and aqueous fractions of aquatic matrixes when studying the distribution and transport of target compounds that are poorly water soluble.

Transport of PPCPs and Veterinary Drugs to Tile Drainage following Application of Biosolids and Manure We have evaluated tile drain contamination by PPCPs derived from liquid municipal biosolids (LMB) applied to an agricultural field (7). The LMB was applied at a rate of 93,500 L ha-1 using two contrasting land application methods: one that pre-tilled the soil prior to surface application (LMBA), and the other that surface applied the material on non-tilled soil that was subsequently tilled after land application (LMBSS). Here, the majority of PPCP mass lost to tile drains occurred at the time of land application as a result of rapid macropore flow of LMB to tile drains. The macropore effect was less strongly pronounced for the pre-tillage application method because tillage disrupts the macropores and augments soil porosity (i.e. increasing liquid storage potential). In fact, for PPCPs listed in Table 1, the ratios of mass lost to tile from LMBA relative to LMBSS (LMBA:LMBSS) were 0.14, 0.06, 1.17, 0.89, and 0.83 for ACE, ATN, CBZ, TCS, and SMX respectively. Peak concentrations for the selected PPCPs in tile discharge are shown in Table 1, but these peaks were highly transient in nature (i.e. minutes). Taking a modeling approach, Larsbo et al. (9) demonstrated that for situations where flow velocities in the macropores will be high, such as might occur during land application of LMB, net solute residence time in the macropores may be short. Larsbo et al. (9) improved considerably the MACRO model for providing estimates of Predicted Environmental Concentrations (PECs) of PPCPs in tile drainage after LMB land application by considering non-equilibrium sorption in the macropores. Non-equilibrium sorption is likely to occur when solute residence time is too short for reactions to reach ‘equilibrium’ at the solution-solid interface; the latter being an intrinsic assumption of many models regarding reactive solutes. By considering non-equilibrium sorption in the macropores, predictions of PPCP 230 Halden; Contaminants of Emerging Concern in the Environment: Ecological and Human Health Considerations ACS Symposium Series; American Chemical Society: Washington, DC, 2010.


concentrations improved by between roughly 56 to 125% for selected compounds (9). Using this modeling approach, carbamazepine and triclosan mass losses to tile drains were predicted, as a percent of mass applied to field, to be ~2 and 6%, respectively; similar to what was observed in field experiments (7). Unlike LMB, dewatered municipal biosolids (DMB) will not move significantly to depth in the soil at land application, unless mobilized by rainfall or irrigation. However, the nature of how the material is applied to the surface will govern PPCP persistence and mobilization. We studied the transport to tile drainage of PPCPs after application of DMB (8) using either subsurface injection (DMBDI) or surface spreading with subsequent shallow incorporation (DMBSS). After applications of DMB at a rate of 8 Mg dw ha-1, peak concentrations of most PPCPs in tile water occurred well after land application (Table 1). For instance, maximum triclosan concentrations occurred ~110 days after land application (8). DMB applied to the soil can be considered in some ways as a delayed release fertilizer, whereby environmental processes that break down the biosolids are required to release biosolid constituents into the soil environment. Peak PPCP concentrations in tile water after DMB application were never higher than those observed for the LMB study (Table 1), but in both cases, the peak concentrations were brief, over a time span of minutes to hours. Hence, from studies performed here, pulses of PPCPs in tile drain effluent resulting from both LMB and DMB applications were highly transient. Nevertheless, some target compounds demonstrated persistence in the soil-groundwater environment after LMB and DMB application, as demonstrated by the detection of residues of naproxen, atenolol, triclosan and other PPCPs in the tile water several months after application (7, 8). Triclosan showed evidence of leaching from soil in a field that was monitored after 33 years of biosolids applications (10). We conducted similar studies of the fate of veterinary medicines after application of pig manure slurry over two years at a tile-drained field site in the UK (11). The study investigated the fate of three antibiotics: oxytetracycline, tylosin and sulfachloropyridazine. Pig slurry, spiked with the study compounds at realistic concentrations, was applied to a field in arable production in two consecutive years and the concentrations of the target compounds in the soil and tile drain water were monitored over time. Both sulfachloropyridazine and oxytetracycline were detected in soil at concentrations up to 365 and 1691 μg kg-1, respectively. The oxytetracycline was seen to persist in the soil from some time, but tylosin was not detected. Oxytetracycline and sulfachloroyridazine were transported to field drains, with peak concentrations observed in drainflow in the first year of the study at 613 and 36 μg L-1 for sulfachloropyridazine and oxytetracycline, respectively. These findings could be explained by the persistence and sorption characteristics of the antibiotics, as oxytetracycline has a large sorption coefficient and sulfachloropyridazine has a small sorption coefficient, while tylosin is rapidly degraded in slurry. In the second year of the study, the soil was tilled prior to application of the slurry and concentrations observed in drainflow were an order of magnitude lower than seen in the first year of monitoring. These observations are in agreement with the no tillage vs tillage results described previously for human PPCPs applied in LMB and DMB (7, 8). 231 Halden; Contaminants of Emerging Concern in the Environment: Ecological and Human Health Considerations ACS Symposium Series; American Chemical Society: Washington, DC, 2010.

Table 1. Maximum concentrations (ng L-1) of selected PPCPs measured in tile drainage from fields where there were applications of liquid municipal biosolids (LMB) (7) or dewatered municipal biosolids (DMB) (8) using various techniques


ACE

ATN

CBZ

TCS

TCC

SMX

LMBSS

440*

267*

1136

3676

ND

322*

LMBA

432*

40*

213

296

ND

22*

DMBDI

104

57

32

227

2

Transport of PPCPs and Veterinary Medicines from Agricultural Fields

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