Long-term monitoring of sulfonamides and tetracyclines in manure amended soils and leachate samples - A follow-up study.

Antibiotics can be detected in manure and digestate samples worldwide. As manure is a frequently used fertilizer, antibiotics are found in soil and leachate samples. Only little is known about the long-term fate of antibiotics in the soil environment. One shortcut is the lack of appropriate monitoring studies. Here we present the results of an unequalled soil monitoring study over 18 years from an agricultural field site in Lower Saxony (Germany). Sulfonamides and tetracycline are mainly fixed in the upper soil layer. Contents showed a sharp decrease below sampling depth of 30 cm (plough depth). Sulfaguanidine and sulfamethazine (SMZ) were detected down to 90 cm. Water samples taken below the field site revealed the transfer of sulfonamides into leachate. High variances were observed between sampling points emphasizing the need for sampling strategies for environmental studies. In addition, field lysimeters with defined input of sulfonamides enabled a long-term monitoring and mass balance of antibiotic transfer into leachate over 10 years. SMZ showed the highest mobility with concentrations up to 65 ng L-1. Less than 0.5% of the applied SMZ was transferred into the leachate. Data of lysimeter and field water samples support the theory of a steady state process with a continuous input of sulfonamides such as SMZ into leachate. Soils contaminated with antibiotics can be a long-term source for the input of antibiotic active compounds into deeper soil layers and groundwater.

Long-term monitoring of sulfonamide leaching from manure amended soil into groundwater.

Veterinary antibiotics such as sulfonamides are frequently applied in livestock farming worldwide. Due to poor absorption in the animal gut and/or reversible metabolization sulfonamides are excreted in considerable amounts and can subsequently be detected in liquid manure. As manure is utilized for soil fertilization, sulfonamides can enter the environment via this pathway. Water samples taken below an agriculture field in Lower Saxony revealed the permanent entrance of sulfamethazine into groundwater and concentrations up to 100 ng L-1 were determined. During a long-term lysimeter study, nine sulfonamides were applied to two different soil types by using fortified liquid manure. Divert mobilities were found with sulfamethazine und sulfamethoxazole showing the highest detection frequency in water samples taken below both bedrock and sandy soil. Four years after the last application of fortified manure, sulfonamides were still detectable in the leachate. Based on analyses of manure and fermentation residue samples, a permanent input of sulfonamides to the soil can be excluded. Thus, the positive findings must be caused by the antibiotics once applied. Soils fertilized with manure contaminated with sulfonamides can consequently be a long-time source for the transfer of antibiotics into groundwater.

High emissions of greenhouse gases from grasslands on peat and other organic soils.

Drainage has turned peatlands from a carbon sink into one of the world's largest greenhouse gas (GHG) sources from cultivated soils. We analyzed a unique data set (12 peatlands, 48 sites and 122 annual budgets) of mainly unpublished GHG emissions from grasslands on bog and fen peat as well as other soils rich in soil organic carbon (SOC) in Germany. Emissions and environmental variables were measured with identical methods. Site-averaged GHG budgets were surprisingly variable (29.2 ± 17.4 t CO2 -eq. ha-1  yr-1 ) and partially higher than all published data and the IPCC default emission factors for GHG inventories. Generally, CO2 (27.7 ± 17.3 t CO2  ha-1  yr-1 ) dominated the GHG budget. Nitrous oxide (2.3 ± 2.4 kg N2 O-N ha-1  yr-1 ) and methane emissions (30.8 ± 69.8 kg CH4 -C ha-1  yr-1 ) were lower than expected except for CH4 emissions from nutrient-poor acidic sites. At single peatlands, CO2 emissions clearly increased with deeper mean water table depth (WTD), but there was no general dependency of CO2 on WTD for the complete data set. Thus, regionalization of CO2 emissions by WTD only will remain uncertain. WTD dynamics explained some of the differences between peatlands as sites which became very dry during summer showed lower emissions. We introduced the aerated nitrogen stock (Nair ) as a variable combining soil nitrogen stocks with WTD. CO2 increased with Nair across peatlands. Soils with comparatively low SOC concentrations showed as high CO2 emissions as true peat soils because Nair was similar. N2 O emissions were controlled by the WTD dynamics and the nitrogen content of the topsoil. CH4 emissions can be well described by WTD and ponding duration during summer. Our results can help both to improve GHG emission reporting and to prioritize and plan emission reduction measures for peat and similar soils at different scales.

Different behavior of tetracyclines and sulfonamides in sandy soils after repeated fertilization with liquid manure.

Recently we showed that tetracyclines tend to persist and may accumulate in sandy soils after repeated fertilizations with liquid manure. We continued these field investigations from 2001 to 2003 and observed no further accumulation of tetracyclines in soil, but found that the average tetracycline concentration remained higher than 150 microg/kg soil. From 2000 to 2002, approximately 330 g tetracycline, 7 g chlortetracycline, 28 g sulfamethazine, and 57 g sulfadiazine per hectare were transferred via liquid manure to the topsoil (0-30 cm). Nevertheless, no leaching of tetracyclines into deeper soil segments or groundwater was observed. Furthermore, we developed new analytical methods for the detection of various sulfonamides in liquid manure, soil, and groundwater. Investigation of the same fields used in the tetracycline study showed that sulfamethazine occurred in concentrations approximately two orders of magnitude lower than that of tetracycline in the plow layer. Although there apparently were very low concentrations of sulfamethazine in soil, we detected it in groundwater sampled by suction probes at 1.4 m below soil surface in the spring of 2002. Further investigations confirmed these findings. To our knowledge, this is the first direct evidence of continuous leaching of a veterinary drug from soil into groundwater under field conditions. We conclude that tetracyclines and sulfonamides show distinctly different environmental behaviors. One explanation may be their different sorption coefficients in soil, indicating (in part) their different mobilities in this ecosystem.

Soil microbial parameters and luminescent bacteria assays as indicators for in situ bioremediation of TNT-contaminated soils.

In situ bioremediation is increasingly being discussed as a useful strategy for cleaning up contaminated soils. Compared to established ex situ procedures, meaningful and reliable approaches for monitoring the remediation processes and their efficiency are of special importance. The subject of this study was the significance of two bioassays for monitoring purposes. The work was performed within the scope of a research project on the in situ bioremediation of topsoil contaminated with 2,4,6-trinitrotoluene (TNT). To evaluate changes within different experimental fields during a 17-month remediation period, the results of soil microbial assays and luminescent bacteria assays were compared with chemical monitoring data. The luminescent bacteria assays showed a significant reduction of the water-soluble soil toxicants in the treated fields. This bioassay proved to be a sensitive screening indicator of toxicity and may effectively aid the ecotoxicological interpretation of chemical monitoring data. Microbial biomass (C(mic)), the metabolic quotient (qCO2), and the ratio of microbial to organic carbon (C(mic)/C(org)) showed a highly significant correlation with total concentrations of TNT in the soil. But, in contrast to luminescent bacteria assays, this approach did not reveal any recovery of the soil at the end of the remediation period. There is clear evidence for persistent adverse effects of chronic TNT contamination on the site-specific microbial community and the local carbon cycle in the soil. The study clearly exhibits the differences between, as well as the complementary value of both bioassay approaches for monitoring short-term and long-term effects of soil contamination and the efficiency of remediation.

Determination of persistent tetracycline residues in soil fertilized with liquid manure by high-performance liquid chromatography with electrospray ionization tandem mass spectrometry.

Little is known about the occurrence and the fate of veterinary drugs in the environment. Therefore, a liquid chromatography/tandem mass spectrometry method was developed and employed to investigate in detail the distribution and persistence of the frequently used tetracyclines and tylosin in a field fertilized with liquid manure on April 2000 and April 2001; soil sampling was performed in May 2000, November 2000, and May 2001. We detected 4.0 mg/kg tetracycline and 0.1 mg/kg chlortetracycline in the liquid manure of April 2000, as well as comparable amounts in the liquid manure of April 2001. In the soil samples of May 2001, the highest average concentrations of 86.2 (0-10 cm), 198.7 (10-20 cm), and 171.7 microg/kg (20-30 cm) tetracycline and 4.6-7.3 micro/kg chlortetracycline (all three sublayers) were found. At soil depths between 30 and 90 cm, as well as in soil or groundwater, tetracyclines could not be detected. In addition, oxytetracycline and tylosin could not be detected in any sample investigated. We conclude that tetracyclines enter the environment in significant concentrations via repeated fertilizations with liquid manure, build up persistent residues, and accumulate in soil. Therefore, tetracyclines may have a potential risk and investigations on the environmental effects of these antibiotics are necessary.