A fast and simple SPE-LC-MS/MS procedure for extraction and quantitative analysis of 1,2,4-triazole, N,N-dimethylsulfamide, and other small polar organic compounds in groundwater

Leaching of unexpected cyazofamid degradation products into groundwater demonstrates gaps in current pesticide risk assessment

To investigate the formation and leaching potential of degradation products N,N-dimethylsulfamide (DMS) and dimethylsulfamic acid (DMSA) from cyazofamid under real-world agricultural conditions, the fungicide cyazofamid was applied in a potato crop as part of the Danish Pesticide Leaching Assessment Programme (PLAP). Leaching of DMS, DMSA, 4-chloro-5-(4-methylphenyl)-1H-imidazole-2-carbonitrile (CCIM), and 4-chloro-5-(4-methylphenyl)-1H-imidazole-2-carboxylicacid (CTCA) was monitored in water from the variably saturated zone (suction cups) and groundwater for more than two years following the applications. In total, 424 samples were analyzed for the content of the four degradation products. An additional laboratory study was executed in parallel with the field monitoring study. Here, cyazofamid was applied to soil columns and leaching of the four degradation products was studied under controlled conditions. In the EFSA conclusion on cyazofamid, CCIM and CTCA are mentioned as major relevant metabolites; DMS is not mentioned in the risk assessment and DMSA is only included in acute oral toxicity studies and an in vitro bacterial mutation assay. In contrast to the EFSA conclusion on cyazofamid, our studies showed no leaching of the two major metabolites, CTCA and CCIM, but instead, major leaching of DMS and DMSA in both the field and laboratory studies was observed. That is, both DMS and DMSA leached to the groundwater in concentrations >0.1 μg/L for more than half a year. Based on this, we suggest improvements to the current pesticide risk assessment.

Effects of wavelength on the treatment of contaminants of emerging concern by UV-assisted homogeneous advanced oxidation/reduction processes

Pollutants of emerging concern in aqueous environments present a significant threat to both the aquatic ecosystem and human health due to their rapid transfer. Among the various treatment approaches to remove those pollutants, UV-assisted advanced oxidation/reduction processes are considered competent and cost-effective. The treatment effectiveness is highly dependent on the wavelength of the UV irradiation used. This article systematically discusses the wavelength dependency of direct photolysis, UV/peroxides, UV/chlor(am)ine, UV/ClO2, UV/natural organic matter, UV/nitrate, and UV/sulfite on the transformation of contaminants. Altering wavelengths affects the photolysis of target pollutants, photo-decay of the oxidant/reductant, and quantum yields of reactive species generated in the processes, which significantly impact the degradation rates and formation of disinfection byproducts. In general, the degradation of contaminants is most efficient when using wavelengths that closely match the highest molar absorption coefficients of the target pollutants or the oxidizing/reducing agents, and the contribution of pollutant absorption is generally more significant. By matching the wavelength with the peak absorbance of target compounds and oxidants/reductants, researchers and engineers have the potential to optimize the UV wavelengths used in UV-AO/RPs to effectively remove pollutants and control the formation of disinfection byproducts.

The fate of nitrification and urease inhibitors in simulated bank filtration

The application of nitrification and urease inhibitors (NUI) in conjunction with nitrogen (N) fertilizers improves the efficiency of N fertilizers. However, NUI are frequently found in surface waters through leaching or surface runoff. Bank filtration (BF) is considered as a low-cost water treatment system providing high quality water by efficiently removing large amounts of organic micropollutants from surface water. The fate of NUI in managed aquifer recharge systems such as BF is poorly known. The aim of this work was to investigate sorption and degradation of NUI in simulated BF under near-natural conditions. Besides, the effect of NUI on the microbial biomass of slowly growing microorganisms and the role of microbial biomass on NUI removal was investigated. Duplicate sand columns (length 1.7 m) fed with surface water were spiked with a pulse consisting of four nitrification (1,2,4-triazole, dicyanodiamide, 3,4-dimethylpyrazole and 3-methylpyrazole) and two urease inhibitors (n-butyl-thiophosphoric acid triamide and n-(2-nitrophenyl) phosphoric triamide). The average spiking concentration of each NUI was 5 μg/L. Experimental and modeled breakthrough curves of NUI indicated no retardation for any of the inhibitors. Therefore, biodegradation was identified as the main elimination pathway for all substances and was highest in zones of high microbial biomass. Removal of 1,2,4-triazole was 50% and n-butyl-thiophosphoric acid triamide proved to be highly degradable and was completely removed after a hydraulic retention time (HRT) of 24 h. 50% of the mass recovery for nitrification inhibitors except for 3,4-dimethylpyrazole was observed at the effluent (4 days HRT). In addition, a mild effect of NUI on microbial biomass was noted. This study highlights that the degradation of NUI in BF depends on HRT and microbial biomass.

Nano liquid chromatography, an updated review

Low flow chromatography has a rich history of innovation but has yet to reach widespread implementation in bioanalytical applications. Improvements in pump technology, microfluidic connections, and nano-electrospray sources for mass spectrometry have laid the groundwork for broader application, and innovation in this space has accelerated in recent years. This article reviews the instrumentation used for nano-flow liquid chromatography , the types of columns employed, and strategies for multi-dimensionality of separations, which is key to the future state of the technique to the high-throughput needs of modern bioanalysis. An update of the current applications where nano-LC is widely used, such as proteomics and metabolomics, is discussed. But the trend towards biopharmaceutical development of increasingly complex, targeted, and potent therapeutics for the safe treatment of disease drives the need for ultimate selectivity and sensitivity of our analytical platforms for targeted quantitation in a regulated space. The selectivity needs are best addressed by mass spectrometric detection, especially at high resolutions, and exquisite sensitivity is provided by nano-electrospray ionization as the technology continues to evolve into an accessible, robust, and easy to use platform.

Leaching of 1,2,4-triazole from commercial barley seeds coated with tebuconazole and prothioconazole

Seed dressing with fungicide or insecticide is a standard procedure for growing major crops, but very little is known about the leaching risk and the general fate of pesticides from coated seeds. Triazole fungicides are commonly used seed dressing fungicides and recently, there has been increasing concern that 1,2,4-triazole, a major degradation product of several triazole fungicides, may leach to groundwater in concentrations exceeding the 0.1 μg/L threshold limit of the European Union. We therefore carried out a laboratory column experiment with commercial barley seeds coated with the triazole fungicides tebuconazole and prothioconazole to study the fate of the fungicides and their degradation products, especially 1,2,4-triazole. Our experiment showed that the fungicides themselves were relatively immobile in the soil columns, but also that leaching of 1,2,4-triazole will occur no matter if tebuconazole or prothioconazole is used as seed dressing. Relatively high 1,2,4-triazole concentrations (up to 0.8 μg/L) were measured in the column leachates, but when the experiment was terminated after 63 days, a total of only 1 % of the fungicides was recovered as 1,2,4-triazole in the leachate. Our results suggest that seed dressing pesticides should be considered together with spray applications when estimating the total 1,2,4-triazole load from agriculture and that seed dressing pesticides and their degradation products should be included when evaluating leaching risks from pesticide applications in agriculture.

Biodegradation of third-generation organic antifouling biocides and their hydrolysis products in marine model systems

The environmental fate for some selected antifouling biocides, dichlofluanid, tolylfluanid, tralopyril, and medetomidine, is relatively poorly understood with nearly all data derived from the assessment reports. Water/sediment systems and biofilms were used to determine biodegradation of the antifouling biocides. Dichlofluanid and tolylfluanid are known to hydrolyze to form DMSA (N,N-dimethyl-N'-phenylsulfamide) and DMST (N,N-Dimethyl-N'-(4-methylphenyl)sulfamide), respectively. DMSA did not show biodegradation, but it was shown to transform abiotically into N,N-dimethylsulfamide (N,N-DMS). In contrast, the structurally similar DMST did show biodegradation with a half-life of 5.78 days. The resulting transformation product of the biodegradation of DMST is also N,N-DMS. N,N-DMS accounted for the majority of the mass balance after 27 days in the water/sediment systems. Moreover, the biofilm systems also degraded both DMSA and DMST to N,N-DMS. The hydrolysis product of tralopyril, called BCCPCA (3-bromo-5-(4-chlorophenyl)-4-cyano-1 H-pyrrole-3-carboxylic acid), was not metabolized in the experiments and remained persistent. For this compound, a new log K_ow of 2.47 was determined since the previously reported K_ow value seemed to overestimate sediment partitioning. Medetomidine was removed from the water/sediment system, though, not significantly more than the control. However, a transformation product (medetomidine-acid) was detected in the incubation but not in the control, pointing to limited biodegradation. These results show that tolylfluanid can be rapidly removed by biodegradation in the marine environment, while dichlofluanid, tralopyril, and medetomidine remained in the system for a longer period of time. The prolonged stability of these biocides could mean that there is potential for accumulation in the environment. This potential is also there for the DMSA (dichlofluanid) and DMST (tolylfluanid) derived transformation product N,N-DMS, which was recalcitrant.

Abiotic fate of tolylfluanid and dichlofluanid in natural waters

To prevent the growth of unwanted organisms on ship hulls, antifouling paints, containing biocides such as tolylfluanid (N-[dichlor(fluor)methyl]sulfanyl-N-(dimethylsulfamoyl)-4-methylaniline) and dichlofluanid (N-(dichlorfluormethylthio)-N',N'-dimethyl-N-phenylsulfamid), are applied. There are concerns over their occurrence and fate in the marine environment due to long-term immersion in water. In the present study, the hydrolysis and photolysis of these compounds were investigated. Results showed that tolylfluanid and dichlofluanid hydrolyzed completely to their respective hydrolysis products DMST (N,N-dimethyl-N'-p-tolylsulfamide) and DMSA (N,N-dimethyl-N'-phenylsulfamide) in coastal water within 24 h. Furthermore, the transformation of tolylfluanid and dichlofluanid under natural sunlight was determined in selected marine waters (coastal water and sea water) in comparison to deionized water. The experiments revealed that photodegradation rates of DMST and DMSA in coastal water were higher than in sea water or deionized water. The indirect phototransformation of the hydrolysis products with selected reactive species (triplet state organic matter, singlet oxygen, and hydroxyl radicals) showed that DMST and DMSA mainly display triplet reactivity. The measured half-lives of the hydrolysis products in natural waters were 2.7 and 23 days, with DMST being considerably faster transformed than DMSA. However, several direct and indirect photoproducts have been newly identified and measured. DMS (N,N-dimethylsulfamide), was identified as the major phototransformation product in natural waters. It is generated by indirect photodegradation processes and exhibits potential persistence in the environment.