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George, IA, United States

Pannu M.W.,University of Florida | O'Connor G.A.,University of Florida | Toor G.S.,Soil Quality Laboratory
Environmental Toxicology and Chemistry | Year: 2012

Triclosan (TCS) is a common constituent of personal care products and is frequently present in biosolids. Application of biosolids to land transfers significant amounts of TCS to soils. Because TCS is an antimicrobial and is toxic to some aquatic organisms, concern has arisen that TCS may adversely affect soil organisms. The objective of the present study was to investigate the toxicity and bioaccumulation potential of biosolids-borne TCS in terrestrial micro- and macro-organisms (earthworms). Studies were conducted in two biosolids-amended soils (sand, silty clay loam), following U.S. Environmental Protection Agency (U.S. EPA) guidelines. At the concentrations tested herein, microbial toxicity tests suggested no adverse effects of TCS on microbial respiration, ammonification, and nitrification. The no observed effect concentration for TCS for microbial processes was 10mg/kg soil. Earthworm subchronic toxicity tests showed that biosolids-borne TCS was not toxic to earthworms at the concentrations tested herein. The estimated TCS earthworm lethal concentration (LC50) was greater than 1mg/kg soil. Greater TCS accumulation was observed in earthworms incubated in a silty clay loam soil (bioaccumulation factor [BAF]=12±3.1) than in a sand (BAF=6.5±0.84). Field-collected earthworms had a significantly smaller BAF value (4.3±0.7) than our laboratory values (6.5-12.0). The BAF values varied significantly with exposure conditions (e.g., soil characteristics, laboratory vs field conditions); however, a value of 10 represents a reasonable first approximation for risk assessment purposes. © 2011 SETAC. Source

Waria M.,University of Florida | O'Connor G.A.,University of Florida | Toor G.S.,Soil Quality Laboratory
Environmental Toxicology and Chemistry | Year: 2011

Land application of biosolids can constitute an important source of triclosan (TCS) input to soils, with uncertain effects. Several studies have investigated the degradation potential of TCS in biosolids-amended soils, but the results vary widely. We conducted a laboratory degradation study by mixing biosolids spiked with [ 14C]-TCS (final concentration=40mg/kg) with Immokalee fine sand and Ashkum silty clay loam soils at an agronomic application rate (22 Mg/ha). Biosolids-amended soils were aerobically incubated in biotic and inhibited conditions for 18 weeks. Subsamples removed at 0, 2, 4, 6, 9, 12, 15, and 18 weeks were sequentially extracted with an operationally defined extraction scheme to determine labile and nonlabile TCS fractions. Over the 18-week incubation, the proportion of [ 14C] in the nonlabile fraction increased and the labile fraction decreased, suggesting decreasing availability to biota. Partitioning of TCS into labile and nonlabile fractions depended on soil characteristics. Less than 0.5% of [ 14C]-TCS was mineralized to carbon dioxide ( 14CO 2) in both soils and all treatments. A degradation metabolite, methyl triclosan (Me-TCS), was identified in both soils only in the biotic treatment, and increased in concentration over time. Even under biotic conditions, biosolids-borne TCS is persistent, with a primary degradation (TCS to Me-TCS) half-life of 78d in the silty clay loam and 421d in the fine sand. A half-life of approximately 100d would be a conservative first approximation of TCS half-life in biosolids-amended soils for risk estimation. © 2011 SETAC. Source

Pannu M.W.,University of Florida | Toor G.S.,Soil Quality Laboratory | O'Connor G.A.,University of Florida | Wilson P.C.,University of Florida
Environmental Toxicology and Chemistry | Year: 2012

Triclosan (TCS) is an antimicrobial compound commonly found in biosolids. Thus, plants grown in biosolids-amended soil may be exposed to TCS. We evaluated the plant toxicity and accumulation potential of biosolids-borne TCS in two vegetables (lettuce and radish) and a pasture grass (bahia grass). Vegetables were grown in growth chambers and grass in a greenhouse. Biosolids-amended soil had TCS concentrations of 0.99, 5.9, and 11mg/kg amended soil. These TCS concentrations represent typical biosolids containing concentrations of 16mg TCS/kg applied at agronomic rates for 6 to 70 consecutive years, assuming no TCS loss. Plant yields (dry wt) were not reduced at any TCS concentration and the no observed effect concentration was 11mg TCS/kg soil for all plants. Significantly greater TCS accumulated in the below-ground biomass than in the above-ground biomass. The average bioaccumulation factors (BAFs) were 0.43±0.38 in radish root, 0.04±0.04 in lettuce leaves, 0.004±0.002 in radish leaves, and <0.001 in bahia grass. Soybean (grain) and corn (leaves) grown in our previous field study where soil TCS concentrations were lower (0.04-0.1mg/kg) had BAF values of 0.06 to 0.16. Based on the data, we suggest a conservative first approximate BAF value of 0.4 for risk assessment in plants. © 2012 SETAC. Source

Banger K.,Soil Quality Laboratory | Toor G.S.,Soil Quality Laboratory | Chirenje T.,The Richard Stockton College of New Jersey | Ma L.,University of Florida
Soil and Sediment Contamination | Year: 2010

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic pollutants in urban environments and are considered as the priority pollutants by the U.S. Environmental Protection Agency. The objective of this study was to determine the depth-wise distribution (0-15, 15-30, and 30-45 cm) of 16 PAHs compounds in four urban soils of different land uses (residential, public parks, public buildings, and commercial areas) in Miami, Florida, USA. The PAHs were analyzed using a Gas Chromatograph equipped with a Flame Ionization Detector. Results showed that across use soils, total PAHs were significantly greater at surface (1,869 μg/kg) than sub-surface (478-1,079 μg/kg). Among land uses at 0-15 cm, PAHs were significantly greater in commercial areas (2,364 μg/kg) than the residential and public parks (1,508-1,595 μg/kg), but not the public buildings (2,007 μg/kg). However, at lower depths, PAHs were greater in residential soils (15-30 cm: 1,454 μg/kg; 30-45 cm: 834 μg/kg) compared with other land uses (15-30 cm: 839-1,104 μg/kg; 30-45 cm: 251-456 μg/kg). The contents of high molecular weight PAHs (HMWPAHs) were greater than the low molecular weight PAHs (LMWPAHs) in all soils at all depths. For example, at 0-15 cm, HMWPAHs were twice as much (1,039-1,602 μg/kg) as LMWPAHs (467-762 μg/kg). All three source identification indices, including the predominance of HMWPAHs over the LMWPAHs, 0.42 to 0.50 ratio of fluoranthene to fluoranthene + pyrene, and 0.78 to 1.36 ratio of phenanthrene to anthracene, suggest that the dominant source of PAHs in the urban soils originated from the pyrogenic processes, particularly the burning of fossil fuel. These results can help set baseline concentrations and the exposure risk to terrestrial organisms of PAHs in the urbanized and rapidly urbanizing areas. © Taylor & Francis Group, LLC. Source

Lusk M.G.,Soil Quality Laboratory | Toor G.S.,Soil Quality Laboratory
Water Research | Year: 2016

A portion of the dissolved organic nitrogen (DON) is biodegradable in water bodies, yet our knowledge of the molecular composition and controls on biological reactivity of DON is limited. Our objective was to investigate the biodegradability and molecular composition of DON in streams that drain a gradient of 19-83% urban land use. Weekly sampling over 21 weeks suggested no significant relationship between urban land use and DON concentration. We then selected two streams that drain 28% and 83% urban land use to determine the biodegradability and molecular composition of the DON by coupling 5-day bioassay experiments with high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Both urban streams contained a wide range of N-bearing biomolecular formulas and had >80% DON in lignin-like compounds, with only 5-7% labile DON. The labile DON consisted mostly of lipid-and protein-like structures with high H/C and low O/C values. Comparison of reactive formulas and formed counterparts during the bioassay experiments indicated a shift toward more oxygenated and less saturated N-bearing DON formulas due to the microbial degradation. Although there was a little net removal (5-7%) of organic-bound N over the 5-day bioassay, there was some change to the carbon skeleton of DON compounds. These results suggest that DON in urban streams contains a complex mixture of compounds such as lipids, proteins, and lignins of variable chemical structures and biodegradability. © 2016 Elsevier Ltd. Source

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