7 research outputs found
Does Long-Term Irrigation with Untreated Wastewater Accelerate the Dissipation of Pharmaceuticals in Soil?
Long-term irrigation with untreated
wastewater may increase soil
microbial adaptation to pollution load and lead to enhanced natural
attenuation. We hypothesized that long-term wastewater irrigation
accelerates the dissipation of pharmaceuticals. To test our hypothesis
we performed an incubation experiment with soils from the Mezquital
Valley, Mexico that were irrigated for 0, 14, or 100 years. The results
showed that the dissipation half-lives (<i>DT</i><sub>50</sub>) of diclofenac (<0.1–1.4 days), bezafibrate (<0.1–4.8
days), sulfamethoxazole (2–33 days), naproxen (6–19
days), carbamazepine (355–1,624 days), and ciprofloxacin were
not affected by wastewater irrigation. Trimethoprim dissipation was
even slower in soils irrigated for 100 years (<i>DT</i><sub>50</sub>: 45–72 days) than in nonirrigated soils (<i>DT</i><sub>50</sub>: 12–16 days), was negatively correlated
with soil organic matter content and soil-water distribution coefficients,
and was inhibited in sterilized soils. Applying a kinetic fate model
indicated that long-term irrigation enhanced sequestration of cationic
or uncharged trimethoprim and uncharged carbamazepine, but did not
affect sequestration of fast-dissipating zwitterions or negatively
charged pharmaceuticals. We conclude that microbial adaptation processes
play a minor role for pharmaceutical dissipation in wastewater-irrigated
soils, while organic matter accumulation in these soils can retard
trimethoprim and carbamazepine dissipation
Accumulation of Pharmaceuticals, <em>Enterococcus</em>, and Resistance Genes in Soils Irrigated with Wastewater for Zero to 100 Years in Central Mexico
<div><p>Irrigation with wastewater releases pharmaceuticals, pathogenic bacteria, and resistance genes, but little is known about the accumulation of these contaminants in the environment when wastewater is applied for decades. We sampled a chronosequence of soils that were variously irrigated with wastewater from zero up to 100 years in the Mezquital Valley, Mexico, and investigated the accumulation of ciprofloxacin, enrofloxacin, sulfamethoxazole, trimethoprim, clarithromycin, carbamazepine, bezafibrate, naproxen, diclofenac, as well as the occurrence of <em>Enterococcus</em> spp., and <em>sul</em> and <em>qnr</em> resistance genes. Total concentrations of ciprofloxacin, sulfamethoxazole, and carbamazepine increased with irrigation duration reaching 95% of their upper limit of 1.4 µg/kg (ciprofloxacin), 4.3 µg/kg (sulfamethoxazole), and 5.4 µg/kg (carbamazepine) in soils irrigated for 19–28 years. Accumulation was soil-type-specific, with largest accumulation rates in Leptosols and no time-trend in Vertisols. Acidic pharmaceuticals (diclofenac, naproxen, bezafibrate) were not retained and thus did not accumulate in soils. We did not detect <em>qnrA</em> genes, but <em>qnrS</em> and <em>qnrB</em> genes were found in two of the irrigated soils. Relative concentrations of <em>sul1</em> genes in irrigated soils were two orders of magnitude larger (3.15×10<sup>−3</sup>±0.22×10<sup>−3</sup> copies/16S rDNA) than in non-irrigated soils (4.35×10<sup>−5</sup>±1.00×10<sup>−5</sup> copies/16S rDNA), while those of <em>sul2</em> exceeded the ones in non-irrigated soils still by a factor of 22 (6.61×10<sup>–4</sup>±0.59×10<sup>−4</sup> versus 2.99×10<sup>−5</sup>±0.26×10<sup>−5</sup> copies/16S rDNA). Absolute numbers of <em>sul</em> genes continued to increase with prolonging irrigation together with <em>Enterococcus</em> spp. 23S rDNA and total 16S rDNA contents. Increasing total concentrations of antibiotics in soil are not accompanied by increasing relative abundances of resistance genes. Nevertheless, wastewater irrigation enlarges the absolute concentration of resistance genes in soils due to a long-term increase in total microbial biomass.</p> </div
Compound properties and measurement details.
a<p>at pH 7 and 25°C;</p>b<p>Data are from SciFinder Database (<a href="https://scifinder.cas.org" target="_blank">https://scifinder.cas.org</a>), accessed May 2, 2012;</p>c<p>Data are from Verlicchi et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045397#pone.0045397-Verlicchi1" target="_blank">[74]</a>;</p>d<p>Predicted Environmental Concentration (including excretion rate, mean 2003/2004);</p>e<p>Data are from Figuero-Diva et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045397#pone.0045397-FigueroaDiva1" target="_blank">[75]</a>;</p>f<p>Data are from Barron et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045397#pone.0045397-Barron1" target="_blank">[76]</a>;</p>g<p>not available.</p
Concentrations of ciprofloxacin (CIP), sulfamethoxazole (SMX), and carbamazepine (CAR) in soils irrigated repeatedly with untreated wastewater.
<p>Irrigation took place for different numbers of years. The displayed total concentrations were calculated as the sum of CaCl<sub>2</sub>-extractable and ASE-extractable concentrations (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045397#pone.0045397.s001" target="_blank">Figure S1</a> in the supporting online information). Error bars indicate the standard deviation of concentrations in four quadrant parcels of individual fields. Dashed lines mark the irrigation time until 95% of the upper limit concentration is reached.</p
Soil properties.
a<p>Data are from Siebe <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045397#pone.0045397-Siebe3" target="_blank">[73]</a>;</p>b<p>organic carbon (OC) content.</p
Absolute (panel A) and relative abundance (panel B) of <i>sul1</i>, <i>sul2</i> resistance genes in soils.
<p>Soils were irrigated repeatedly with untreated wastewater for different numbers of years. Error bars indicate the standard deviation between laboratory replications (three replicates) of the same composite soil sample for one field. The small letters “a” and “b” differentiate between fields that have been irrigated for the same period of time.</p
Tracing Copper Derived from Pig Manure in Calcareous Soils and Soil Leachates by <sup>65</sup>Cu Labeling
Copper
is used as a growth promoter in animal husbandry, resulting
in high Cu concentrations in animal manure. We tested whether Cu would
be mobilized in soils receiving excessive loads of manure, both from
recently added and from aged fractions. To discriminate between these
Cu sources, manure was labeled with <sup>65</sup>Cu. After soil application
of 0, 15, and 30 Mg manure ha<sup>–1</sup>, leachate was collected
in free-draining lysimeters (40 cm depth) under undisturbed soil over
a 53 day period. Determining the total amounts of Cu and the fractions
of <sup>65</sup>Cu in leachate and the soil profile enabled us to
trace the translocation of Cu derived from labeled manure. More than
84% of the applied Cu was retained in the top 2 cm of soil. Less than
0.01% of the applied Cu was detected overall in the leachate. Of this
amount, however, 38% (±8.9 SE) was leached within 8 days after
application. The total Cu concentration in leachates (32–164
μg L<sup>–1</sup>) frequently exceeded the Chinese groundwater
quality standard of 50 μg L<sup>–1</sup>. The added <sup>65</sup>Cu, however, accounted for less than 3.6% of the total Cu
leaching load, suggesting that Cu from older sources and/or geological
background controls contamination, regardless of current land management