Distribution of the herbicide atrazine in a microcosm with riparian forest plants

Pesticides applied on sugarcane reach the subsoil of riparian forests and probably contaminate the river water. This work was conducted to learn about the phytoremediation of atrazine and subsoil contamination using the common riparian forest species of Cecropia hololeuca Miq. and Trema micranta (L.) Blum. These plants were grown in soil microcosms where ¹⁴C-atrazine at 1/10 of the field-recommended dose was applied at the bottom of the microcosm simulating the movement from contaminated ground water to the upper soil layers and into plants. Residues of ¹⁴C-atrazine were detected in all parts of the microcosm including soil, rhizosphere and the roots in different layers of the microcosm, stem and leaves. Atrazine mineralization was higher (10.2%) in the microcosms with plants than the control microcosms without plants (1.2%). The upward movement of this pesticide from deeper to more superficial soil layers occurred in all the microcosms with plants, powered by evapotranspiration process. From the atrazine applied in this study about 45% was taken up by C. hololeuca and 35% by T. micrantha. The highest amount of radioactivity (%) was found in the fine roots and the specific radioactivity (% g^?1) showed that thick, fine roots and leaves bioaccumulate atrazine. The enhanced mineralization of atrazine as well the phytostabilization effect of the tree biomass will reduce the bioavailability of these residues and consequently decrease the hazardous effects on the environment.     

Fate of atrazine and chlorpyrifos during solid state fermentation—examination of processes

Abstract

Solid state fermentation (SSF) was investigated as a means to dispose of two commonly used pesticides, chlorpyrifos (O, O‐diethyl O‐(3,5,6‐trichloro‐2‐pyridyl) phosphorothioate) and atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine). SSF experiments were carried out in bench‐scale bioreaetors (equipped with CO₂ and volatile organic traps) containing a mixture of lignocellulosic materials and a radiolabeled pesticide. Ethyl acetate‐extractable, alkali soluble, and alkali insoluble fractions were evaluated for radioactivity following a 60‐d incubation period at 40°C. The majority of the [2, 6‐pyridyl‐¹⁴C]chlorpyrifos was associated with the ethyl acetate extract (about 74%), 17% was trapped as organic volatiles by polyurethane foam traps and < 0.5% of the chlorpyrifos was mineralized to CO². Only small amounts of the radioactivity were associated with alkali soluble (0.0003%) and alkali insoluble (0.3%) fractions. In the [¹⁴C‐U‐ring] atrazine bioreactors, very little of the radioactivity volatilized (<0.5%) and less than 0.5% was mineralized to CO₂. Approximately 57% of the applied radioactivity was associated with the ethyl acetate extract while 9% and 24% of the radioactivity was associated with the alkali soluble (humic and fulvic acids) and alkali insoluble fractions, respectively. Possible reaction mechanisms by which covalent bonds could be formed between atrazine (or metabolites) and humic substances were investigated. The issue of bound atrazine residue (alkali soluble fraction) was at least partially resolved. Oxidative coupling experiments revealed that formation of covalent bond linkages between amino substituent groups of atrazine residue and humic substances is highly unlikely.     

Fate and distribution of 14C-atrazine in a tropical oxisol

The herbicide atrazine is the most commonly detected pesticide in groundwater world-wide. A new microcosm test-system was used to determine the fate of 14C-atrazine in a Brazilian oxisol. 14C Ring-labelled atrazine was applied in a mixture with the commercial product Gesaprim 500 (Novartis) at a rate of 3 kg ha-1. During two months, about 1% of the initially applied amount was lost by volatilization. The mineralization of the pesticide, measured directly using 14CO2 evolved from the applied pesticide, was between 0.09% and 0.16%, whereas less than 0.2% was leached. The distribution of radioactivity in the soil profile showed that most of the radioactivity remained in the top soil down to a 3 cm depth. The radioactivity in the upper 3 cm of the column was adsorbed perferably in fulvic acid (FA) and human fractions.     

Fate of 14C‐allylalcohol herbicide in soils and crop residues

Abstract

Residue disappearance and leaching of ¹⁴C‐allyl‐alcohol from different soils were studied in laboratory experiments. Additionally, the uptake of residues by lettuce and carrots was investigated in the greenhouse. In laboratory experiments, residue disappearance and leaching from soils was correlated negatively to the organic matter content. In greenhouse experiments with a sandy loam soil at an application rate normally used in practice, an average of 12.5 % of the applied radioactivity was recovered after an eight day interval between application and sowing. Furthermore, an average of 8 % (sum in soil and plants) of the applied radioactivity was recovered after lettuce or carrot growing. Uptake of residues was higher by carrots than by lettuce, and higher by lettuce roots than by lettuce tops. No bioaccumulation was observed. The residues in soils and plants were, to a high percentage, unextractable and, to a smaller extent, fully water‐soluble products. Unchanged allylalcohol could not be detected by the analytical methods used.     

Dissipation and metabolism of C-spiroxamine in soil under laboratory condition

Spiroxamine [SPX] belongs to a spiroketalamine group of substances. The biodegradation of [1,3-dioxolane-4-¹⁴C]-SPX has been examined in 2 soils of different physicochemical properties. The total recovery of radioactivity from soils was 98.6-103.5% of that applied. The total amount of extractable radioactivity declined with a simultaneous increase in non-extractable radioactivity. Volatile organics were detected at lower levels; however, mineralization played a marked effect on the route of SPX dissipation. The half-life ranges between 37 and 44 d. SPX does not undergo any enantioselective degradation. 4 metabolites: despropyl-SPX, desethyl-SPX, SPX N-oxide and SPX acid were identified, applying mass spectrometric technique. Sorption-desorption data fitted well with a Freundlich model in log form (r², 0.99). K_Dsorp ranged between 44 and 230, suggesting SPX ought to be considered as a substance with low leaching potential [groundwater ubiquity score (GUS), <1.8]. Furthermore, an overall low desorption of 1-11% indicates firm retention of SPX by the soils.     

Behaviour of [ring-C] hydroxy-simazine in a parabraun soil

[Ring-¹⁴C] hydroxy-simazine was incubated in a parabraun soil for 102 days at 22°C and 65 % of the maximum water-holding capacity. Soil samples were analyzed according to two different extraction methods on the day of application as well as after 13, 62 and 102 days. Furthermore, the influence of air-drying the soil specimens on the extraction yield was also studied. Hydroxy-simazine was converted to ¹⁴CO₂ only up to 0.2 % of the applied radioactivity. A rapid bonding of the radioactivity to the organic mass of the soil was observed, especially in the fulvic acid and humin fractions. 62 days after beginning conversion these two fractions already altogether contained up to 85 % of the labelled ring carbon applied. Whereas in the humic acids only a maximum of 4.5 % was discovered.     

Metabolic fate of the 14C-labeled herbicide clodinafop-propargyl in a sediment–water system

The metabolic fate of ¹⁴C-phenyl-labeled herbicide clodinafop-propargyl (¹⁴C-CfP) was studied for 28 days in lab assays using a sediment–water system derived from a German location. Mineralization was 5.21% of applied ¹⁴C after 28 days exhibiting a distinct lag phase until day 14 of incubation. Portions of radioactivity remaining in water phases decreased at moderate rate to 18.48% after 28 days; 62.46% were still detected in water after 14 days. Soxhlet extraction of the sediment using acetonitrile released 35.56% of applied ¹⁴C with day 28, while 33.99% remained as non-extractable residues. A remarkable increase of bound ¹⁴C was observed between 14 and 28 days correlating with the distinct increase of mineralization. No correlation was found throughout incubation with microbial activity of the sediment as determined by dimethyl sulfoxide reduction. Dissolved oxygen and pH value of water phases remained almost constant for 28 days. Analyses of Soxhlet extracts of the sediment and ethyl acetate extracts of water phases by radio-TLC and radio-HPLC revealed that CfP was rapidly cleaved to free acid clodinafop (Cf), which was further (bio-) transformed. DT₅₀ values (based on radio-HPLC) were below 1 day (CfP) and slightly above 28 days (Cf). Further metabolites were not detected. Fractionation of humic and non-humic components of the sediment demonstrated that CfP's non-extractable residues were predominantly associated with fulvic acids up to 14 days of incubation (3.36%), whereas after 28 days, the majority of radioactivity was found in the humin/mineral fraction (13.30% of applied ¹⁴C). Due to high-performance size-exclusion chromatography of the fulvic acids fraction derived from assays incubated for 28 days, this portion of ¹⁴C was firmly, possibly covalently bound to fulvic acids and did not consist of CfP or Cf. Using an isolation strategy comprising preincubation of sediment with CfP and mineralization of ¹⁴C-CfP as criterion, a microorganism was isolated from the sediment examined. It grew on ¹⁴C-CfP as sole carbon source with evolution of ¹⁴CO₂. The bacterium was characterized by growth on commonly used carbon sources and 16S rDNA sequence analysis. Its sequence exhibited high similarity with that of Nocardioides aromaticivorans strain H-1 (98.85%; DSM 15131, JCM 11674).     

Fate of ochratoxin a in goats

Abstract

The fate of ochratoxin A (OA) was studied in goats given a single oral dose of ³H‐OA (0.5 mg/kg). More than 90% of the radioactivity was found to be excreted in 7 days and the majority (53%) was found in feces. Thirty‐eight percent, 6% and 2.26% of the activity was found in urine, milk and serum, respectively. The radioactivity in the liver and kidney 6 hours after feeding amounted to 1.5 and 0.5% of the total dose administered, respectively. Subsequent fractionation of liver and kidney homogenates revealed that microsomes, ribosomes and post‐ribosomal supernatant fractions contained most radioactivity. Thin layer chromatographic analyses revealed two additional radioactive spots with Upvalues and fluorescent characteristics different from OA, Oα and 4‐OH‐OA. Whereas OA was found as the unaltered molecule in feces, the metabolites were primarily found in urine and milk. Less than 0.03% of free OA was found in milk during the 7‐day period.     

Metabolic fate of the 14C-labeled herbicide clodinafop-propargyl in soil

The metabolic fate of ¹⁴C-phenyl-labeled herbicide clodinafop-propargyl (CfP) was studied for 28 days in lab assays using a soil from Germany (A_p horizon, silt loam, and cambisol). Mineralization amounted to 12.40% of applied ¹⁴C after 28 days showing a distinct lag phase until day 7 of incubation. Portions of radioactivity extractable by means of 0.01 M CaCl₂ solution (bioavailable fraction) decreased rapidly and were 4.41% after 28 days. Even immediately after application, only 57.31% were extracted with the aqueous solvent. Subsequent extraction using accelerated solvent extraction (ASE; acetonitrile/water 4:1, v/v) released 39.91% of applied ¹⁴C with day 0 and 26.16% with day 28 of incubation from the samples. Non-extractable portions of radioactivity thus, increased with time amounting to 11.99% (day 0) and 65.00% (day 28). A remarkable increase was observed between 14 and 28 days correlating with the distinct increase of mineralization. No correlation was found throughout incubation with general microbial activity as determined by DMSO reduction. Analysis of the CaCl₂ and ASE extracts by radio-TLC, radio-HPLC and GC/MS revealed that CfP was rapidly cleaved to free acid clodinafop (Cf), which was further (bio-) transformed; DT₅₀ values (based on radio-TLC detection of the parent compound) were far below 1 day (CfP) and about 7 days (Cf). TLC analysis pointed to 2-(4-hydroxyphenoxy)-propionic acid as further metabolite. Due to fractionation of non-extractable residues, most of the ¹⁴C was associated with fulvic and humic acids, portions in humin fractions and non-humics were moderate and low, respectively. Using a special strategy, which included pre-incubation of the soil with CfP and then mineralization of ¹⁴C-CfP as criterion, a microorganism was isolated from the soil examined. The microorganism grew using CfP as sole carbon source with concomitant evolution of ¹⁴CO₂. The bacterium was characterized by growth on commonly used carbon sources and by 16S rDNA sequence analysis. The sequence exhibited high similarity with that of Rhodococcus wratislaviensis (99.56%; DSM 44107, NCIMB 13082).     

Biodegradation of Trifluralin in Harran Soil

Abstract

Degradation of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) was investigated in soils taken from three different locations at Harran region of Turkey under laboratory conditions. Surface (0–10 cm) soils, which were taken from a pesticide untreated field Gürgelen, Harran-1 and Ikizce regions in the Harran Plain, were incubated in biometer flasks for 350 days at 25°C. Ring-UL-¹⁴C-trifluralin was applied at the rate of 2 µg g^?1 with 78.7 kBq radioactivity per 100 g soil flask. Evolved ¹⁴CO₂ was monitored in KOH traps throughout the experiment. Periodically, soil sub-samples were removed and extracted by supercritical fluid extraction (SFE). Unextractable soil-bound ¹⁴C residues were determined by combustion. During the 350 days incubation period 6.6, 5.4, and 3.3% of the applied radiocarbon was evolved as ¹⁴CO₂ from the Harran-1, Gürgelen, and Ikizce soil, respectively. At the end of 350 days the SFE-extractable and bound ¹⁴C-trifluralin residues were 39.0 and 29.2% of the initially applied herbicide in Gürgelen soil. The corresponding values for Harran-1 and Ikizce soils were 36.2, 28.4% and 41.6, 18.5% respectively.     

Contributions to ecological chemistry CVII1. Fate of lindane-14C in lettuce, endives and soil under outdoor conditions.

In seven successive outdoor experiments, lindane-14C was applied to lettuce or endive leaves as an aqueous formulation (about 12 mg on 20 plants for each experiment). The growing periods varied between 21 and 37 days. After this time, between 4.5% and 13.9% of the applied radiocarbon was recovered from the plants. Conversion rates to soluble metabolites as well as to unextractable residues appeared to be dependent on weather conditions. During the summer months, the radiocarbon in plants consisted of 36% soluble metabolites and of 30% unextractable residues (average of 4 experiments); in autumn, the conversion rates were much lower. The following metabolites were identified in both plant species by gas chromatography/mass spectrometry: a polar group (a free trichlorophenol, 2,3,4,6-tetrachlorophenol, pentachlorophenol, conjugates of the latter two compounds, and unidentified water-soluble products) amounting to 35% of the radioactivity in plants cultivated in summer, and a nonpolar group (a dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,2,3,5, and/or 1,2,4,5-tetrachlorobenzene, pentachlorobenzene, hexachlorobenzene, and gamma-pentachlorocyclohexene) amounting to 1% of the radioactivity in plants cultivated in summer. The 20 cm top-soil layer had about 14% of the total radioactivity applied to all plants. Six % of the radioactivity recovered from the soil was soluble metabolites and about 50% was not extractable. The soluble metabolites comprised a polar group (free and conjugated 2,3,4,6-tetrachlorophenol, pentachlorophenol, and unidentified water soluble products) amounting to 5% of the radioactivity in the soil as well as a nonpolar group (1,2,3-trichlorobenzene, 1,2,3,4-tetrachlorobenzene, 1,2,3,5 and/or 1,2,4,5-tetrachlorobenzene, pentachlorobenzene, hexachlorobenzene, and gamma-pentachlorocyclohexene) amounting to 1% of the radioactivity in the soil.     

Fate of the veterinary antibiotic 14C-difloxacin in soil including simultaneous amendment of pig manure with the focus on non-extractable residues

The fate of ¹⁴C-labeled difloxacin (¹⁴C-DIF) was studied in time course experiments after application on soil (Ap horizon of silt loam) and amendment of authentic DIF containing pig manure (146 mL kg^?1; 4.17 MBq kg^?1; 0.85 mg kg^?1) or water (124 mL kg^?1; 0.42 MBq kg^?1; 0.09 mg kg^?1) for 56 and 120 days of incubation, respectively.

Mineralization of ¹⁴C-DIF was below 0.2% in both experiments after 56 days or 120 days. In the course of the experiments, portions of extractable radioactivity (Accelerated Solvent Extraction (ASE); acetonitrile-water) decreased to 19–21% depending only little on manure amendment. Non-extractable residues of ¹⁴C-DIF increased to 70–74% after 56 days and 120 days, respectively, and therefore were the main route of ¹⁴C-DIF in soil. According to radioanalytical HPLC and LC-MS/MS, only the parent compound was found in all extracts over the whole time of the experiment. According to fractionation of the non-extractable residues (NER) into particle size fractions, ¹⁴C portions were associated to the water used for fractionation, the silt and clay fractions, whereas no radioactivity was detected in the sand fraction. The majority of ¹⁴C was found within the clay fractions.

Fractionation of humic components showed that radioactivity derived from ¹⁴C-DIF was associated with humic acids, fulvic acids, humins and minerals and very little with soluble, non-humic HCl fraction. The highest portions of radioactivity were found in the fulvic acid fraction. Results obtained by size exclusion chromatography (SEC) of the purified fulvic acids were similar for every sample analyzed. One large portion of ¹⁴C co-eluted with fulvic acids of a molecular weight below 910 g mol^?1. Both fractionation methods demonstrated that the parent compound DIF or initial metabolites were rapidly integrated into humic materials and, thus, were major components of NER.     

Plant availability of bound anilazine residues in a degraded loess soil

Abstract

The relative biological availability of [benzene ring‐U‐¹⁴C] and Ctriazine‐U‐¹⁴C] anilazine for maize plants was studied in a degraded loess soil in a standardized microecosystem. The total uptake of radiocarbon in the course of the 4‐week experiment was 3.1 and 4 % respectively of the radioactivity applied if anilazine was uniformly mixed into the soil immediately before beginning the experiment. However, if anilazine was subjected to a degradation at 65 % of the maximum water holding capacity of the soil and temperatures varying daily between 16 and 27°C for 100 days before the plant experiment then the uptake was reduced to 0.4 or 0.7 % respectively. The uptake from soil with non‐extractable (bound) anilazine residues was similarly low. The mineralization rate of aged and bound anilazine residues was below 0.1 % of the radioactivity applied. Up to 2/3 of the radioactivity present in the soil after the plant experiment remained in the humic fraction.     

Primary photoproducts and half-lives

The photolytically induced decomposition of fluoroquinolone carboxylic acids (enrofloxacin, danofloxacin, ciprofloxacin and norfloxacin) at concentrations of 10 mg/l in pure water and an irradiation intensity of 200 W/m² (xenon lamp) led to half-lives from 20.6 min (danofloxacin) to 105.9 min (norfloxacin). The environmental half-life of enrofloxacin was calculated by the GCSOLAR program and resulted in 1.8 to 55.4 hours, depending on the season and degree of latitude. During the irradiation procedure, products were built up which primarily demonstrated alterations involving the piperazine ring as compared with the parent compounds. The amount of¹⁴CO₂ evolved by the photomineralization of¹⁴C-labeled enrofloxacin reached 26.4 % of the applied radioactivity. The main photoproducts were isolated by HPLC and their structural elucidation was carried out by different spectroscopic methods (MS, GC/MS and¹H-NMR).     

Enhancement of natural radioactivity in fertilized soil of Faisalabad, Pakistan

Background, goal, and scope

Natural radioactivity in phosphate rock (PR) is transferred to phosphate fertilizer (PF) during the manufacturing process of the PF. The continuous addition of the PF to the cultivated soil accumulates the radionuclides in the land and increases the level of radioactivity in the soil. The purpose of the present study was to investigate the enhanced level of accumulated radioactivity due to the continuous addition of the PF in the farmlands of Nuclear Institute of Agriculture and Biology (NIAB) at Faisalabad in Pakistan. The selected study area consisted of the highly fertilized farmlands and an unfertilized barren land of the NIAB.

Introduction

The understudy area is very fertile for the growth of various types of crops; therefore, four agricultural research institutes have been established at Faisalabad and NIAB is one of those. The NIAB has developed various research farmlands at different places in Pakistan. The crop yield has been increased by adding various fertilizers in the farmlands. The addition of the PF accompanied with the radionuclides enhances radioactivity in the fields. Human being is exposed directly or indirectly to this radiological hazard. A prolong exposure may become a cause of health risk.

Materials and methods

The area of study consisted of three types of lands: the land under cultivation for the last 40 and 30?years called Site 1 and Site 2, respectively, and the barren land was called Site 3. A total of 75 soil samples were collected within the crop rooting zone (up to 25?cm deep) of the soil of the NIAB farms. The samples were dried, pulverized to powder, sealed in plastic containers, and stored to achieve equilibrium between ²²⁶Ra and ²²²Rn. Activity concentrations of the radionuclides ²³⁸U (²²⁶Ra), ²³²Th, and ⁴⁰K in soil samples were determined by using a high resolution gamma ray spectrometry system, consisting of an high purity germanium detector coupled through a spectroscopy amplifier with a PC based MCA installed with Geni-2000 software.

Results

The measured activity concentration levels of ⁴⁰K were 662?±?15, 615?±?17, and 458?±?20?Bq?kg^?1, ²²⁶Ra were 48?±?6, 43?±?5, and 26?±?4?Bq?kg^?1, and that of ²³²Th were 39?±?5, 37?±?5, 35?±?5?Bq?kg^?1, respectively, in the soil of the Sites 1, 2, and 3. Gamma dose rate 1?m above the soil surface was 55, 51, and 40?nGy?h^?1 from Sites 1, 2, and 3, respectively. External dose rates in the rooms constructed of the bricks made of the soil from Sites 1, 2, and 3 were 161, 149, and 114?nGyh^?1, respectively.

Discussions

Activity concentration values of ⁴⁰K and ²²⁶Ra in the soil of Sites 1 and 2 were higher than that in the soil of Site 3. The relative rise of ⁴⁰K was 43?% and 34?% and that of ²²⁶Ra was 85?% and 65?% respectively in these sites. Activity concentrations of ²³²Th in all these sites were in the background range. Gamma dose rate 1?m above soil surface of Sites 1 and 2 was 40?% and 30?% respectively higher than that from the soil of Site 3. The rise in activity of ⁴⁰K and ²²⁶Ra and gamma dose from the Site 1 was greater than that from the Site 2. The least activity and dose were observed from the Site 3. Gamma dose in the dwellings made of fertilized soil bricks of Site 1 and Site 2 were respectively calculated to be 41?% and 32?% higher than that in the abodes made of unfertilized soil bricks of Site 3.

Conclusions

Activity concentrations of ²²⁶Ra and ⁴⁰K were observed to be enhanced in the fertilized farmlands of the NIAB. Outdoor and indoor gamma dose as radiological hazard were found to be increasing with the continuous addition of PF in the understudy farmlands.

Recommendations

It is recommended that naturally occurring radioactive metal should be removed during the process of manufacturing of the PF from the PR.

Prospective

The rise in radioactivity in the farmlands due to the addition of the PF can be a source of direct or indirect exposure to radiation that may enhance cancer risk of the exposed individuals.     

Fate of atrazine and chlorpyrifos during solid state fermentation--examination of processes

Solid state fermentation (SSF) was investigated as a means to dispose of two commonly used pesticides, chlorpyrifos (O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphorothioate) and atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine). SSF experiments were carried out in bench-scale bioreactors (equipped with CO2 and volatile organic traps) containing a mixture of lignocellulosic materials and a radiolabeled pesticide. Ethyl acetate-extractable, alkali soluble, and alkali insoluble fractions were evaluated for radioactivity following a 60-d incubation period at 40 degrees C. The majority of the [2,6-pyridyl-14C]chlorpyrifos was associated with the ethyl acetate extract (about 74%), 17% was trapped as organic volatiles by polyurethane foam traps and < 0.5% of the chlorpyrifos was mineralized to CO2. Only small amounts of the radioactivity were associated with alkali soluble (0.0003%) and alkali insoluble (0.3%) fractions. In the [14C-U-ring]atrazine bioreactors, very little of the radioactivity volatilized (<0.5%) and less than 0.5% was mineralized to CO2. Approximately 57% of the applied radioactivity was associated with the ethyl acetate extract while 9% and 24% of the radioactivity was associated with the alkali soluble (humic and fulvic acids) and alkali insoluble fractions, respectively. Possible reaction mechanisms by which covalent bonds could be formed between atrazine (or metabolites) and humic substances were investigated. The issue of bound atrazine residue (alkali soluble fraction) was at least partially resolved. Oxidative coupling experiments revealed that formation of covalent bond linkages between amino substituent groups of atrazine residue and humic substances is highly unlikely.     

Assessment of the abiotic transformation of 17β-estradiol in the presence of vegetable matter

A study using 17β-¹⁴C₄-estradiol (¹⁴C-E2) was performed to confirm and characterize the catalytic transformation of estrogens in the presence of a model vegetable matter (namely rabbit food) as a surrogate material for vegetable wastes found in sewage. Results corroborated the occurrence of an abiotic transformation. Unknown transformation byproduct(s) accounted, respectively, for 38% and 9% of the initial radioactivity in liquid and extractable solid phases after 72 h; on the other hand, only 15% and 7% of this radioactivity corresponded to ¹⁴C-E2 in those same matrices. Mass balance was closed including the radioactivity irreversibly bounded to the solid phase. Formation of ¹⁴C₄-estrone was monitored by Liquid Chromatography with tandem Mass Spectrometry detection; negative results were found in all sampling events. This process could be harnessed to optimize sustainable technologies for the removal of phenolic microcontaminants from wastewater.     

Metabolism of the14C-labeled herbicide clodinafop-propargyl in plant cell cultures of wheat and tobacco

The metabolism of ¹⁴C-clodinafop-propargyl (CfP) was examined in cell cultures of wheat (Triticum aestivum L. cv. ‘Heines Koga II’) and tobacco (Nicotiana tabacum L.). Besides the non-transgenic tobacco culture, cultures transformed separately with cDNA of human cytochrome P450-monooxygenases (P450s) CYP1A1, CYP1A2, CYP3A4, CYP2B6 and CYP2C19 were examined. Experiments with wheat were executed in the presence and absence of safener cloquintocet-mexyl (CqM). After 48 h of incubation, only about 10% of applied ¹⁴C was found in media (both tobacco and wheat). Non-extractable residues of ¹⁴C-CfP in wheat cells were 16.54% (without CqM) and 30.87% (with CqM). In all tobacco cultures, 82.41–92.46% of applied radioactivity was recovered in cell extracts. In contrast to wheat, non-extractable residues amounted only to 1.50–2.82%. As determined by radio-thin layer chromatography (TLC) and -high-performance liquid chromatography (HPLC), the parent CfP was not found in the cell extracts of wheat; in tobacco cell extracts, only traces of CfP were detected. After a hydrolysis of assumed carbohydrate conjugates of CfP derived polar ¹⁴C-labeled compounds, TLC and HPLC analysis showed that in wheat, a more complex pattern of metabolites of CfP were observed as compared to all tobacco cultures. In hydrolysates resulting from wheat, the identity of three primary products was confirmed by means of GC-EI-MS: free acid clodinafop (Cf), hydroxy-Cf hydroxylated at the pyridinyl moiety, and 4-(5-chloro-3-fluoropyridin-2-yloxy)phenol. In hydrolysates derived from all tobacco cultures, main metabolite was Cf besides only traces of further unidentified products. Differences among the different tobacco cultures (non-transgenic, transgenic) did not emerge. According to kinetics of disappearance of primary metabolite Cf as well as formation of polar soluble products and non-extractable residues, metabolization of CfP proceeded at a noticeably higher rate in wheat cells treated with safener CqM than in cells without CqM treatment. Thus, these results indicated a stimulation of CfP's metabolism by CqM, although metabolic profiles observed in CqM treated and non-treated cells (after hydrolysis) were qualitatively similar. The findings obtained from all tobacco cultures suggested that with the exception of ester cleavage to Cf, CfP cannot be metabolized by tobacco itself or by the human P450s examined.     

Analyses of airborne Be concentrations in Hong Kong using back-trajectories

A total of 71 air samples were collected in Hong Kong area from November 2001 to February 2003 using a high-volume air sampler and a high-volume cascade impactor with five atmospheric pressure stages. The ⁷Be radioactivity on each stage was measured using a high-efficiency germanium gamma-ray spectrometer. From the radioactivity of stages, the total airborne ⁷Be radioactivity was determined. The activity median aerodynamic diameter (AMAD) of ⁷Be-associated atmospheric aerosols was found to be 0.22–1.11 μm and the geometric standard deviation (GSD) was found to be 1.2–10.5. With the assumed mean growth rate (MGR) of atmospheric aerosols of 0.004–0.005 μm h⁻¹ and the size of Aitken nuclei of 0.015 μm, the residence times of ⁷Be-associated atmospheric aerosols were also found from the AMAD.Three-dimensional 4-day back-trajectories were obtained using the HYSPLIT model from NOAA Air Resources Laboratory. These trajectories were used with the measured ⁷Be radioactivity to construct regional ⁷Be intensity fields for four different altitude levels (less than 1000, 1000–2000, 2000–3000 and above 3000 m) with a Geographic Information System (GIS). Low ⁷Be intensities were found to have advected from low altitudes (less than 1000 m) and oceanic areas. The ⁷Be intensities increased for the higher intensity field layers.By comparing the time taken for air masses to come from the ⁷Be source to Hong Kong and the residence time determined from the AMAD of ⁷Be-associated atmospheric aerosols, good agreement was found if the mean growth rate of 0.005 μm h⁻¹ for atmospheric aerosols was used, and the use of back-trajectories was shown to be satisfactory even up to about 6.5 d. By using the residence time with a MGR of 0.005 μm h⁻¹, the ⁷Be source was found to be relatively well confined in the areas of Mongolia and southeastern Siberia, which further supported that the association of ⁷Be source with the Siberian anticyclone.     

Environmental dynamics of phosphate esters. II. Uptake and bioaccumulation of 2-ethylhexyl diphenyl phosphate and diphenyl phosphate by fish

Uptake, clearance and disposition of ¹⁴C-labelled 2-ethylhexyl diphenyl phosphate (EHDP) and ¹⁴C-diphenyl phosphate (DPP) by rainbow trout (Salmo gairdneri) were investigated using short-term static exposures. Bioconcentration factors of 1314 and 0.3 were calculated for EHDP and DPP, respectively. Highest levels of radioactivity were found in liver and intestine following exposure to 60 μg/L EHDP. A portion (up to 40%) of the radioactivity in each tissue was in the form of DPP while a similar portion was extractable with methanol but could not be identified.