Environmental Fate And Behavior Of Three Commonly Used Pharmaceuticals And Novel Chiral Pesticide Paichongding In Soil

Pharmaceutical and personal care products (PPCPs) are emerging contaminants in the environment and may lead to their introduction into the environment at trace levels and exert adverse effects on non-target aquatic and terrestrial organisms. PPCPs usually enter the environment through the effluent discharge from. wastewater treatment plants (WWTPs) or in association with biosolids that are deposited in landfills or spread onto agricultural land as soil amendment. Therefore, soil is a primary environmental compartment receiving PPCPs through wastewater irrigation and biosolid application. The antiepileptic drugs carbamazepine (CBZ) and acetaminophen (APAP) are among the most detected human pharmaceuticals in wastewater effluents and biosolids.In this study, we explored the transformation of CBZ and APAP to biologically active intermediates in soil. Both 14C-labeling and LC-MS/MS were used to track transformation kinetics and identify major degradation intermediates. Through 120-d incubation under aerobic conditions, CBZ dissipated rather slowly, and mineralization did not exceed 2% of the spiked rate in different soils. The fraction of non-extractable (i.e., bound) residue also remained negligible (<5%). Amendment of biosolids further prolonged the persistence of CBZ, increasing its half-life to>100 d. Five degradation intermediates were identified, including 10, 11-dihydro-10-hydroxy carbamazepine, carbamazepine-10,11-epoxide, acridone-N-carbaldehyde,4-aldehyde-9-acridone and acridine, of which acridone-N-carbaldehyde was formed in a large fraction and also appeared to be persistent. Electrocyclization, ring cleavage, hydrogen shift, carbonylation and decarbonylation contributed to CBZ transformative reactions in soil, producing biologically active products. The persistence of parent compound and formation of incomplete intermediates suggest that CBZ has a high risk for off-site transport from soil, such as accumulation into plants and contamination of groundwater.Throughout 120-d aerobic incubation, up to 17.0 ± 0.8% of 14C-acetaminophen was mineralized, but mineralization was greatly inhibited after sterilization or amendment of biosolids. Immediately after treatment, the majority of 14C-residue became non-extractable or bound, with the level accounting for 73.4 to 93.3% of the applied amount at the end of incubation. A total of 8 intermediates were identified, including 3-hydroxyacetaminophen, hydroquinone,1,4-benzoquinone, N-acetyl-p-. benzoquinoneimine, p-acetanisidide,4-methoxyphenol,-2-hexenoic acid, and 1, 4-dimethoxybenzene. Mineralization and rapid conversion to bound residues suggest that acetaminophen is quickly detoxified in soil, decreasing the potential for off-site transport such as leaching or runoff. On the other hand, the formation of a large number of degradation intermediates, and their potential biological activity, may pose unknown risks, such as accumulation into edible plants. This risk warrants further investigation.In this study, effects of different types of soil amendments, including biosolids, compost, inorganic N, and activated carbon (AC) on the fate of two commonly detected PPCPs, APAP and SMX, in soil were assessed. There was a gradual dissipation of both acetaminophen and sulfamethoxazole in the soils and soil treatments. Mineralization of 14C-SMX in all soils was rather limited (< 6.8%) during the incubation and the mineralized fraction was much smaller than that of 14C-APAP. After 84 d,30.06% of the applied APAP was lost via mineralization from the unamended soil I.Application of biosolids or compost significantly inhibited the mineralization of both compounds and when soil was amended with biosolids, as the amendment ratio increased, the mineralization further decreased. In addition, biosolids and compost appeared to further enhance the rate of BR formation. For instance, after 84 d of incubation, BR accounted for 64.85% and 66.04% of the initial spiked 14C-APAP in the 5% and 10% compost-amended soil I, which is higher than the fraction of BR in soil I without compost (39.46%). Based on these observations, the N effect and the relationship between sorption strength and degradation kinetics have been studied for the the two pharmaceuticals by adding inorganic fertilizer (NH4NO3) and sorbent material (activated carbon, AC).Mineralization of 14C-SMX was slightly enhanced when 0.2 μg/g NH4NO3 was added in soil I while it was a little suppressed in soil I mixed with 0.5 μg/g NH4NO3. There was no significant difference in mineralization of 14C-acetaminophen as well as ER and BR kinetics of both compounds between NH4NO3 added soil and the soil control. Given that SMX contains N, SMX could be used as N sources by the degrading microorganisms. It is likely that SMX-degrading microorganisms preferentially used nitrogen from NH4NO3, resulting in the decreased.mineralization in the inorganic-N amended soil. There was a significant reduction in mineralization of both APAP and SMX in soils added with AC, especially when the addition ratio was higher than 0.05%. When soil was amended with AC, as the amendment ratio increased, the mineralization further decreased. For instance,30.06% of 14C-APAP was mineralized to 14CO2 in the soil control on day 84,12.79%,6.60% and 6.27% was observed as 14CO2 while 0.05%,0.5% and 2% AC were amended, respectively. On the other hand, AC amendment was appeared to further enhance the rate of BR formation and BR gradually increased as the ratio of AC increased. The dramatic reduction in 14C-APAP and 14C-SMX mineralization and the increase of BR formation found with soils containing relatively high concentrations of AC in this study may be due to enhanced sorption and a subsequent decrease in the bioavailability of both Pharmaceuticals. The sorption test demonstrated that sorption is very important for acetaminophen and sulfamethoxazole degradation. The Kd values increased while soil . amendments added, especially the addition of AC. When AC was applied in soil, the kd value was increased by up to 5683.5 times for SMX, indicating that sorption of the main influencing factor for mineralization and formation of BR of APAP and SMX.In this study, four stereoisomers of 14C-IPP were applied in flooded soils. Kinetics of mineralization, extractable and bound residues or the dissipation kinetics of PP and its metabolites showed diastereoselectivity in IPP degradation, with the enantiomers (5S,7R)-IPP (IPP-SR) and (5R,7S)-IPP (IPP-RS) being more readily mineralized and preferentially bound to soils than enantiomers (5R,7R)-IPP (IPP-RR) and (5S,7S)-IPP (IPP-SS). The overall mineralization was rather limited and did not exceed 4% of the spiked rate. Concurrent to the decreases of extractable residues, the fraction of bound residues increased with time and reached about 34% of the applied radioactivity for 14C-IPP-SR and 14C-IPP-RS as compared to about 23% for 14C-IPP-RR or 14C-IPP-SS. Soil properties such as organic matter content and pH likely contributed to the variability. Relatively rapid formation of bound residue suggests that IPP may be quickly detoxified in flooded paddy soil, decreasing the potential for off-site transport such as leaching or runoff, especially for enantiomers IPP-SR and IPP-RS.14C-labelling coupled with LC-MS/MS were used to evaluate the dissipation routes and transformation pathways of IPP in soils under a range of conditions. A total of 9 intermediates were identified, including 1-((6-chloropyridin-3-yl)methyl)-7-methyl-8-nitro-1,2,3,5,6,7-hexahydroimidazo[1,2-a]pyridin-5-ol (IPP-M1), 1-((6-chloropyridin-3-yl)methyl)-7-methyl-5-propoxyoctahydroimidazo[1,2-a] pyrid ine (IPP-M2), 1-((6-chloropyridin-3-yl)methyl)-6,7-dimethyl-8-nitro-1,2,3,5,6,7-hexahy-droimidazo[1,2-a]pyridin-5-ol (IPP-M3),5-hydroxy-7-methyl-1-(pyridin-3-ylmethyl) hexahydroimidazo[1,2-a]pyridin-8(5H)-one (IPP-M4),1-((6-chloropyridin-3-yl) methyl)-8-nitro-5-propoxy-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine (IPP-M5), 1-((6-chloropyridin-3-yl)methyl)-2,3-dihydroxy-7-methyl-8-nitro-2,3,6,7-tetrahydroimidazo [1,2-a]pyridin-5(1H)-one (IPP-M6), 1-((6-chloropyridin-3-yl)methyl)-7-methyl-2,3,6, 7-tetrahydroimidazo [1,2-a]pyridin-5(1 H)-one(IPP-M7),1-((6-chloropyridin-3-yl)met-hyl)-7-methyl-8-nitro-5-propoxyoctahydroimidazo[1,2-a]pyridine-2,3-diol (IPP-M8), 1-((6-chloropy ridin-3-yl)methyl)-7-methyl-8-nitro-5-propoxy-1,2,3,5,6,7-hexahydro imidazo[1,2-a] pyridin-6-ol (IPP-M9). Depropylation, nitrosylation, denitration, demethylation, dehydroxylation, and ketonization contributed to IPP transformation in flooded soil.