Spatial glyphosate and AMPA redistribution on the soil surface driven by sediment transport processes - A flume experiment

Hazardous impacts of glyphosate on human and environment health: Occurrence and detection in food

With the ever-increasing human population, farming lands are decreasing every year, therefore, for effective crop management; agricultural scientists are continually developing new strategies. However, small plants and herbs always impart a much loss in the yields of the crop and farmers are using tons of herbicides to eradicate that problem. Across the world, several herbicides are available in the market for effective crop management, however, scientists observed various environmental and health effects of the herbicides. Over the past 40 years, the herbicide glyphosate has been used extensively with the assumption of negligible effects on the environment and human health. However, in recent years, concerns have increased globally about the potential direct and indirect effects on human health due to the excessive use of glyphosate. As well, the toxicity on ecosystems and the possible effects on all living creatures have long been at the center of a complex discrepancy about the authorization for its use. The World Health Organization also further classified glyphosate as a carcinogenic toxic component and it was banned in 2017 due to numerous life-threatening side effects on human health. In the present era, the residues of banned glyphosate are more prevalent in agricultural and environmental samples which are directly affecting human health. Various reports revealed the detailed extraction process of glyphosate from different categories of the food matrix. Therefore, in the present review, to reveal the importance of glyphosate monitoring in the food matrix, we discussed the environmental and health effects of glyphosate with acute toxicity levels. Also, the effect of glyphosate on aquatic life is discussed in detail and various detection methods such as fluorescence, chromatography, and colorimetric techniques from different food samples with a limit of detection values are revealed. Overall, this review will give an in-depth insight into the various toxicological aspects and detection of glyphosate from food matrix using various advanced analytical techniques.

Can calcite play a role in the adsorption of glyphosate? A comparative study with a new challenge

Calcite as a sorbent can interact with both inorganic and organic substances through their functional groups. To measure its adsorption ability, another sorbent, saponite was selected because it can sorb glyphosate, an organic compound with a polar molecule and widely used as a herbicide. In this study, the two sorbents calcite and saponite were saturated by calcium chloride, and characterized by SEM-EDX, X-ray diffraction, and Zeta Potential Analyzer to investigate their capacity to sorb glyphosate. After saturation, the saponite became homoionic Ca-saponite with minor changes in morphology and specific surface area. But, the morphology of calcite transformed from rhombohedron to scalenohedron, with an increase of 75-folds in its specific surface, and the zeta potential became positive in alkaline pH, which contradicts the results of all previous research. The modified sorbents (Ca-calcite and Ca-saponite) were added to two soil samples to investigate each sorbent's effect on glyphosate sorption. Adsorption isotherm and percentage of glyphosate desorbed revealed the difference in binding and adsorption sites. The Langmuir and Temkin models fitted isotherm data in low concentrations better and suggested chemosorption for the uptake of glyphosate. FTIR analyses of samples with and without glyphosate were compared and results suggested that the bulk of adsorption happened in siloxane groups and on calcium carbonates surfaces.

Glyphosate used as desiccant contaminates plant pollen and nectar of non-target plant species

Pesticide products containing glyphosate as a systemic active ingredient are some of the most extensively used herbicides worldwide. After spraying, residues have been found in nectar and pollen collected by bees foraging on treated plants. This dietary exposure to glyphosate could pose a hazard for flower-visiting animals including bees, and for the delivery of pollination services. Here, we evaluated whether glyphosate contaminates nectar and pollen of targeted crops and non-target wild plants. Oilseed rape was selected as focal crop species, and Rubus fruticosus growing in the hedgerows surrounding the crop was chosen as non-target plant species. Seven fields of oilseed rape, where a glyphosate-based product was applied, were chosen in east and southeast Ireland, and pollen and nectar were extracted from flowers sampled from the field at various intervals following glyphosate application. Pollen loads were taken from honeybees and bumblebees foraging on the crop at the same time. Glyphosate and aminomethylphosphonic acid (AMPA) residues were extracted using acidified methanol and their concentrations in the samples were determined by a validated liquid chromatography tandem mass spectrometry (LC-MS/MS) method. Glyphosate was detected in R. fruticosus nectar and pollen samples that were taken within a timeframe of two to seven days after the application on the crop as a desiccant. No glyphosate was detected when the application took place before or more than two months prior to our sampling in any of the evaluated matrices. The metabolite AMPA was not detected in any samples. To gain further insight into the potential extent of translocation within both plants and soil when a crop is desiccated using glyphosate before harvesting, and the potential impacts on bees, we recommend a longitudinal study of the presence and fate of glyphosate in non-target flowering plants growing nearby crop fields, over a period of several days after glyphosate application.

Removal and fate of pesticides in a farm constructed wetland for agricultural drainage water treatment under Mediterranean conditions (Italy)

A non-waterproofed surface flow constructed wetland (SFCW), treating agricultural drainage water in Northern Italy, was investigated to gain information on the potential ability for effective pesticide abatement. A mixture of insecticide imidacloprid, fungicide dimethomorph, and herbicide glyphosate was applied, by simulating a single rain event, into 470-m-long water course of the SFCW meanders. The pesticides were monitored in the wetland water and soil for about 2 months after treatment. Even though the distribution of pesticides in the wetland was not uniform, for each of them, a mean dissipation of 50% of the applied amount was already observed at ≤7 days. The dissipation trend in the water phase of the wetland fitted (r² ≥ 0.8166) the first-order model with calculated DT₅₀ of 20.6, 12.0, 5.8, and 36.7 days for imidacloprid, dimethomorph, glyphosate, and the glyphosate metabolite AMPA, respectively. The pesticide behavior was interpreted based on the chemical and physical characteristics of both the substances and the water-soil system. Despite the fast abatement of glyphosate, traces were detected in the water until the end of the trial. The formation of soluble 1:1 complex between glyphosate and calcium, the most representative cation in the wetland water, was highlighted by infrared analyses. Such a soluble complex was supposed to keep traces of the herbicide in solution.

Glyphosate, aminomethylphosphonic acid, and glufosinate ammonium in agricultural groundwater and surface water in China from 2017 to 2018: Occurrence, main drivers, and environmental risk assessment

Glyphosate and glufosinate ammonium are the main herbicides used to control weeds in no-tillage agricultural fields in China. However, their leaching risk to groundwater and ecological risk to aquatic organisms remain unclear. From the agricultural basins among 10 provinces of China, glyphosate, its main metabolite aminomethylphosphonic acid (AMPA), and glufosinate ammonium were detected in 1.01%, 0.86%, 0% of 694 groundwater samples with the maximum concentrations of 2.09, 5.13, and <0.05 μg/L, and were detected in 14.3%, 15.8%, and 2.6% of 196 surface water samples with the maximum levels of 32.49, 10.31 and 13.15 μg/L. Furthermore, to evaluate the main drivers of exposure to the targets in water bodies, the fate models were used. The model simulation indicated that spray drift and overflow runoff were the key factors affecting the exposure to targets in surface water adjacent to rice field, whereas the spray drift deposition, runoff, and erosion induced the exposure to the targets in pond water close to dry land crop fields under different meteorological conditions and soil characteristics. The targets in groundwater posed a low risk to water consumption, while fish embryos might be at unacceptable risk due to glufosinate ammonium exposure in surface water with median risk quotient (RQ) equal to 55.6. The results highlight the spatial and seasonal distribution of glyphosate, AMPA, and glufosinate ammonium in groundwater and surface water in agricultural basins of China, providing the first evidence to the environmental risk of the targets to drinking water consumption and aquatic organism safety in China agriculture system.

Reduced bacterial network complexity in agricultural soils after application of the neonicotinoid insecticide thiamethoxam

Pesticides may alter soil microbial community structure or diversity, but their impact on microbial co-occurrence patterns remains unclear. Here, the effect of the widely used neonicotinoid insecticide thiamethoxam on the bacterial community in five arable soils was deciphered using the 16S rRNA gene amplicon sequencing technique. The degradation half-life of thiamethoxam in nonsterilized soils was significantly lower than that in sterilized soils, suggesting a considerable contribution from biodegradation. Soil bacterial community diversity diminished in high concentration thiamethoxam treatment and its impact varied with treatment concentration and soil type. Bacterial co-occurrence network complexity significantly decreased after exposure to thiamethoxam. Under thiamethoxam stress, the relative changes in bacterial co-occurrence networks were closely related (the majority of p-values < 0.05) to the soil physicochemical properties, yet the diversity and dominant phyla were slightly related (the majority of p-values > 0.05). Additionally, three bacterial genera, Sphingomonas, Streptomyces, and Catenulispora, were identified to be relevant to the degradation of thiamethoxam in soils. This finding deciphers the succession of the bacterial community under thiamethoxam stress across multiple soils, and emphasizes the potential role of physicochemical properties in regulating the ecotoxicological effect of pesticides on the soil microbiome.

Sensitivity analysis of the Pesticide in Water Calculator model for applications in the Pampa region of Argentina

Despite the widespread use of pesticides in the Pampa region of Argentina, mathematical models are rarely employed to predict pesticide fate due to the lack of regionally tested models and the absence of readily available databases to run such models. The objective of the current study was to perform a sensitivity analysis of the Pesticide in Water Calculator (PWC) model for the Pampa Region of Argentina. The sensitivity analysis was performed while simulating applications of 2,4-D (mobile, low Kd) and glyphosate (soil-binding, high Kd) in five localities of the Pampa region: Anguil, Paraná, Marcos Juárez, Pergamino and Tres Arroyos. The sensitivity of the various parameters involved in PWC modelling was evaluated though a two-steps sensitivity analysis which included a first screening of less sensitive parameters with Morris method, followed by a fully global sensitivity analysis of the remaining parameters using Sobol method. When ran under soil and climate conditions typical of the Pampa region of Argentina, PWC was most sensitive to 25% of the parameters evaluated. The sensitive parameters identified depended mainly on the nature of the pesticide molecule being modelled; the location and endpoint considered having much less influence on the sensitivity results. Sensitive parameters belonged to two main grand categories: (i) degradation rates of the pesticide in soil and water, and (ii) parameters descriptive of soil binding, runoff and erosion. The sensitivity analysis of the model PWC performed in the current study represents a crucial first step towards the development and expansion of probabilistic pesticide risk assessment in Argentina, and provides important parameterization criteria that will help obtaining more certain modelling results from PWC in Argentina and elsewhere.

Microcosm experiments and kinetic modeling of glyphosate biodegradation in soils and sediments

Glyphosate (GLP) is one of the most widely-used herbicides globally and its toxicity to humans and the environment is controversial. GLP is biodegradable, but little is known about the importance of site exposure history and other environmental variables on the rate and pathway of biodegradation. Here, GLP was added to microcosms of soils and sediments with different exposure histories and these were incubated with amendments of glucose, ammonium, and phosphate. GLP concentrations were measured with a newly-developed HPLC method capable of tolerating high concentrations of ammonium and amino acids. GLP biodegradation occurred after a lag-time proportional to the level of GLP pre-exposure in anthropogenically-impacted samples (soils and sediments), while no degradation occurred in samples from a pristine sediment after 180 days of incubation. Exposure history did not influence the rate of GLP degradation, after the lag-time was elapsed. Addition of C, N, and P triggered GLP degradation in pristine sediment and shortened the lag-time before degradation in other samples. In all microcosms, GLP was metabolised into aminomethylphosphonic acid (AMPA), which was highly persistent, and thus appears to be a more problematic pollutant than GLP. Bacterial communities changed along the gradients of anthropogenic impacts, but in some cases, taxonomically very-similar communities showed dramatically different activities with GLP. Our findings reveal important interactions between agriculturally-relevant nutrients and herbicides.

Dynamics of glyphosate and AMPA in the soil surface layer of glyphosate-resistant crop cultivations in the loess Pampas of Argentina

This study investigates the dynamics of glyphosate and AMPA in the soil surface layer of two fields growing glyphosate-resistant crops in the loess Pampas of Córdoba Province, Argentina. Glyphosate decay and AMPA formation/decay were studied after a single application, using decay kinetic models. Furthermore, glyphosate and AMPA concentrations were investigated in runoff to evaluate their off-site risk. During a 2.5-month study, cultivations of glyphosate-resistant soybean and maize received an application of 1.0 and 0.81 kg a.e. ha-1, respectively, of Roundup UltraMax©. Topsoil samples (0-1, 1-2 cm) were collected weekly (including before application) and analysed for glyphosate, AMPA and soil moisture (SM) contents. Runoff was collected from runoff plots (3 m2) and weirs after 2 erosive rainfall events, and analysed for glyphosate and AMPA contents (water, eroded-sediment). Under both cultivations, background residues in soil before application were 0.27-0.42 mg kg-1 for glyphosate and 1.3-1.7 mg kg-1 for AMPA. In the soybean area, the single-first-order (SFO) model performed best for glyphosate decay. In the maize area, the bi-phasic Hockey-Stick (HS) model performed best for glyphosate decay, due to an abrupt change in SM regimes after high rainfall. Glyphosate half-life and DT90 were 6.0 and 19.8 days, respectively, in the soybean area, and 11.1 and 15.4 days, respectively, in the maize area. In the soybean area, 24% of the glyphosate was degraded to AMPA. In the maize area, it was only 5%. AMPA half-life and DT90 were 54.7 and 182 days, respectively, in the soybean area, and 71.0 and 236 days, respectively, in the maize area. Glyphosate and AMPA contents were 1.1-17.5 times higher in water-eroded sediment than in soil. We conclude that AMPA persists and may accumulate in soil, whereas both glyphosate and AMPA are prone to off-site transport with water erosion, representing a contamination risk for surface waters and adjacent fields.

Effects of a glyphosate-based herbicide on Fucus virsoides (Fucales, Ochrophyta) photosynthetic efficiency

Herbicides are increasingly recognised as sources of water pollution. Glyphosate-based herbicides (GBHs) are widely used because of their low cost and high effectiveness. By measuring the photosynthetic efficiency of Fucus virsoides fronds exposed to a GBH (Roundup® Power 2.0), we investigated the effect of a continuous exposure (6 days) and the potential of recovery after a short exposure (24 h). Both experiments were carried out combining GBH with and without nutrient enrichment, simulating a runoff event. A factorial experimental design allowed us to assess the potential of interactions between GBH and nutrients, which are likely to co-occur in coastal areas. Our results show deleterious effects of GBH at low concentration on F. virsoides, independently from the duration of exposure and the presence of nutrients.