Transport Of Glyphosate Research Articles

An Analysis of Miscible Displacement and Numerical Modelling of Glyphosate Transport in Three Different Agricultural Soils

Since the introduction of genetically modified (GM) glyphosate-resistant crops, especially in Australia, the United States, and Canada, the use of glyphosate has exploded, raising concerns about its environmental effects both in terrestrial and aquatic environments. There are several factors that can affect the transport of glyphosate in soil, including the pH of the soil, the iron and aluminium oxides in the soil, and the structure of the soil, as well as the application time and microbial biodegradation in the soil. Furthermore, some field studies have shown that glyphosate, along with its degradation products, can be found deep in the aquatic environment and can contaminate groundwater by leaching, which implies that studying glyphosate leaching through agricultural soils is very crucial. The research in this study involves column-leaching experiments on glyphosate-dosed soils using application and flow rates representative of field conditions with bromide as a non-reactive tracer. To determine whether the observed behaviour of glyphosate is consistent with commonly recognized transport processes, the results obtained were incorporated into a one-dimensional transport model (HYDRUS 1D). Initially, physical transport parameters were determined by fitting experimental bromide breakthrough curves (BTCs) with analytical solutions to advection–dispersion equations (ADEs) for pulse boundary conditions at the upper end and zero-gradient conditions at the lower end. Then, these parameters and those from the sorption experiments were used in HYDRUS 1D to describe glyphosate transport behaviour. After three different glyphosate applications, the columns with soils C and A showed the highest glyphosate leaching rates, which is closely related to their macropore structures since bromide also leached at higher rates. A similar lower glyphosate leaching rate was found for soil B as for bromide BTC, indicating that competition between phosphorus and glyphosate for sorption sites did not result in higher rates of leaching.

Modeling rainfall-driven transport of Glyphosate in the vadose zone of two experimental sites in North-East Italy

A vertical one-dimensional analysis of infiltration processes and mobility of a tracer (potassium bromide) and a glyphosate-based herbicide, both subjected to hydrological forcing, was performed. Glyphosate is a widespread herbicide whose potential harmfulness and mobility under hydrological forcing have not been fully understood yet. Here, the spatio-temporal evolution of the two compounds was monitored for one year in two experimental sites (Settolo - Valdobbiadene, Colnù - Conegliano), located within the production area of the Prosecco wine (Treviso, Italy). In each experimental site the activities were carried out on two 25 m2 plots located at distances of 50-100 m from each other. The interpretative analyses considered rainwater infiltration as the driving mechanism of the herbicide transport and allowed us to obtain the calibration of a one-dimensional hydrologic model in each monitored plot. Different scenarios of the tracer evolution were simulated considering the pedologic properties of the shallower soil layers, the status of the plant coverage and of the root apparati, leading to a satisfactory reproduction of the observations in both the experimental sites. Modeling the mobility of the herbicide, considering also the degradation to its metabolite AMPA, proved to be more challenging, due to the tendency of glyphosate to be adsorbed to the soil matrix rather than be dissolved in water and transported toward deeper soil layers. Nevertheless, the analysis of model results for tracer and herbicide, compared with in situ observations, suggests that the transport of the glyphosate can take place even when it is adsorbed to the soil, through the movement, triggered by intense precipitation events, of microscopic soil particles within preferential flow paths.

Glyphosate and AMPA dynamics during the transition towards conservation agriculture: Drivers under shallow groundwater conditions

The environmental fate of glyphosate and its metabolite AMPA were investigated in buried lysimeters in a factorial combination of two cropping systems (conservation and conventional agriculture) and two water table depths (120 and 60 cm). Glyphosate was applied at a rate of 1.44 kg ha−1 a.i., and pore-water was sampled for 48 non-consecutive days along the soil profile (15, 30 and 60 cm) as well as the groundwater. Glyphosate and AMPA concentration in soil was detected to compare the effect of different soil-crop managements on transformation/dissipation dynamics and a full characterization of the soil profile was performed. Freundlich adsorption coefficients were calculated down to 110 cm depth and correlated to laboratory-estimated soil properties. Clay minerals, soil organic carbon, phosphate content, Al and Fe amount were the driving factors influencing most of the glyphosate sorption, regardless of the crop and water management system that did not differentiate between adsorption dynamics. In contrast, conservation practices differently affected glyphosate concentration in the soil profile, although its adoption was limited to two years. Moreover, the occurrence of a shallow water table influenced glyphosate transport in the vadose zone, and its detection in groundwater supported the hypothesis of fast transport of the molecule as mediated by preferential pathways, compromising groundwater quality, especially in agricultural lands. On the contrary, AMPA has never been detected in the groundwater, giving evidence of a diverse adsorption and transport dynamic compared to glyphosate.

Revisión de los efectos contaminantes del glifosato y su posible correlato con procesos de metalurgia extractiva

A review of the contaminating effects of glyphosate and their possible correlation with an extractive metallurgy process was carried out. For such comparison, copper recovery by pyrometallurgy was chosen because the hazardous substances formed (SO2, As4O6) propagate in air and water. Next, those aspects of glyphosate that determine its sanitary tolerance were discussed: carcinogenic risk to humans and maximum concentration in drinking water. As a remarkable fact, it is mentioned that at least one of the constituents of the commercial herbicide formulations has greater toxicity in relation to the active principle. Various issues regarding the glyphosate transport through the subsoil unsaturated zone in an agricultural basin in Argentina were analyzed. According to the compiled references, the inhalation-ingestion of large amounts of the herbicide is required to affect health. This statement would not explain why children exposed to glyphosate, among other pesticides, suffered genetic damage. It was found that the survival of honey bees is threatened by the presence of the herbicide in their diet. Germany, Luxembourg and Austria banned the use of glyphosate in their territories, invoking different arguments. Finally, it was noted that when adverse effects of the herbicide are reported, the work is refuted almost immediately.

Microbiomes and glyphosate biodegradation in edaphic and aquatic environments: recent issues and trends.

Glyphosate (N-(phosphonomethyl)glycine) has emerged as the top-selling herbicide worldwide because of its versatility in controlling annual and perennial weeds and the extensive use of glyphosate-resistant crops. Concerns related to the widespread use of glyphosate and its ubiquitous presence in the environment has led to a large number of studies and reviews, which examined the toxicity and fate of glyphosate and its major metabolite, aminomethylphosphonic acid (AMPA) in the environment. Because the biological breakdown of glyphosate is most likely the main elimination process, the biodegradation of glyphosate has also been the object of abundant experimental work. Importantly, glyphosate biodegradation in aquatic and soil ecosystems is affected not only by the composition and the activity of microbial communities, but also by the physical environment. However, the interplay between microbiomes and glyphosate biodegradation in edaphic and aquatic environments has rarely been considered before. The proposed minireview aims at filling this gap. We summarize the most recent work exploring glyphosate biodegradation in natural aquatic biofilms, the biological, chemical and physical factors and processes playing on the adsorption, transport and biodegradation of glyphosate at different levels of soil organization and under different agricultural managements, and its impact on soil microbial communities.

Identification of Structural Variants in Two Novel Genomes of Maize Inbred Lines Possibly Related to Glyphosate Tolerance.

To study genetic variations between genomes of plants that are naturally tolerant and sensitive to glyphosate, we used two Zea mays L. lines traditionally bred in Poland. To overcome the complexity of the maize genome, two sequencing technologies were employed: Illumina and Single Molecule Real-Time (SMRT) PacBio. Eleven thousand structural variants, 4 million SNPs and approximately 800 thousand indels differentiating the two genomes were identified. Detailed analyses allowed to identify 20 variations within the EPSPS gene, but all of them were predicted to have moderate or unknown effects on gene expression. Other genes of the shikimate pathway encoding bifunctional 3-dehydroquinate dehydratase/shikimate dehydrogenase and chorismate synthase were altered by variants predicted to have a high impact on gene expression. Additionally, high-impact variants located within the genes involved in the active transport of glyphosate through the cell membrane encoding phosphate transporters as well as multidrug and toxic compound extrusion have been identified.

Predicting glyphosate sorption across New Zealand pastoral soils using basic soil properties or Vis–NIR spectroscopy

Glyphosate [N-(phosphonomethyl) glycine] is the active ingredient in Roundup, which is the most used herbicide around the world. It is a non-selective herbicide with carboxyl, amino, and phosphonate functional groups, and it has a strong affinity to the soil mineral fraction. Sorption plays a major role for the fate and transport of glyphosate in the environment. The sorption coefficient (Kd) of glyphosate, and hence its mobility, varies greatly among different soil types. Determining Kd is laborious and requires the use of wet chemistry. In this study, we aimed to estimate Kd using basic soil properties, and visible near-infrared spectroscopy (vis–NIRS). The latter method is fast, requires no chemicals, and several soil properties can be estimated from the same spectrum. The data set included 68 topsoil samples collected across the South Island of New Zealand, with clay and organic carbon (OC) contents ranging from 0.001 to 0.520 kg kg−1 and 0.021 to 0.217 kg kg−1, respectively. The Kd was determined with batch equilibration sorption experiments and ranged from 13 to 3810 L kg−1. The visible near-infrared spectra were obtained from 400 to 2500 nm. Multiple linear regression was used to correlate Kd to oxalate extractable aluminium and phosphorous and pH, which resulted in an R2 of 0.89 and an RMSE of 259.59 L kg−1. Further, interval partial least squares regression with ten-fold cross-validation was used to predict Kd by vis–NIRS, and an R2 of 0.93 and an RMSECV of 207.58 L kg−1 were obtained. Thus, these results show that both basic soil properties and vis–NIRS can predict the variation in Kd across these samples with high accuracy and hence, that glyphosate sorption to a soil can be determined with vis–NIRS.

Glyphosate runoff and its occurrence in rainwater and subsurface soil in the nearby area of agricultural fields in Argentina.

Glyphosate-based products are among the most important herbicides applied to enhance the production of food commodities, leading to the worldwide spread of this herbicide. The main goal of this work was to evaluate the off-site transport of glyphosate in a runoff experiment. A micro-plot experiment was conducted to assess the retention, leaching and runoff of glyphosate under rainfall simulation. Glyphosate losses due to spray drift were estimated. Concentrations of glyphosate and AMPA were determined in rainwater and subsurface soil from agricultural and riparian zones. Analyses were performed with UHPLC-MS/MS. Experimental results demonstrated that 88.1% of the applied glyphosate was retained in the surface soil layer (0–9 cm). Glyphosate leaching was negligible compared to its runoff (3.9%) and spray drift (6.9%). Thus, the risk of groundwater pollution would be lower in comparison to that of both surface waters and rainwater. Moreover, under field conditions, glyphosate and AMPA were detected in 52% of the rainwater samples and glyphosate was detected up to 1 m in both soil profiles. Although the experimental application was made with hand-held knapsack under low wind condition to minimize glyphosate aerial dispersion, the spray drift was the main source of glyphosate off-site transport, degrading air quality and rainwater for human consumption. The balance among spray drift, runoff and soil absorption of glyphosate when it was sprayed close to the soil surface (hand held equipment), demonstrated the importance of spray drift in mass balance studies during runoff and leaching experiments with glyphosate.

Interactions among Glyphosate and Phosphate in Soils: Laboratory Retention and Transport Studies.

The purpose of this study was to determine the effect of PO on the sorption and transport of glyphosate [-(phosphonomethyl) glycine, GPS] in soils. The results of batch experiments indicated significant competition between PO and GPS in two different soils, with PO being preferentially sorbed. The 24-h Freundlich partitioning coefficients for GPS sorption were decreased by 50 to 60% with PO in solution. High sorptive capacities exhibited by soils in the presence of PO suggest the existence of both competitive and ion specific sites in either soil. Miscible displacement transport studies indicated limited effects of competition when GPS was applied in conjunction with or subsequent to pulses of PO. However, when a PO pulse was applied after the application of a GPS pulse, a secondary GPS breakthrough was observed where an additional 4% of the applied herbicide mass was recovered in the effluent solution. This is likely attributed to the PO-mediated displacement of GPS bound to competitive sites. These results are further emphasized by the distribution of residual herbicide in this column, with enrichment of mass at lower depths in the column and a corresponding decrease in GPS mass closer to the column surface. These results indicate that the timing of inorganic P fertilizers relative to GPS applications has a significant impact on the fate of the herbicide in soils. In particular, these findings suggest that GPS may be more liable to leaching in scenarios in which P fertilizers are applied after the application of GPS-based herbicidal formulations.

Biogenic transport of glyphosate in the presence of LDPE microplastics: A mesocosm experiment

The accumulation of plastic debris and herbicide residues has become a huge challenge and poses many potential risks to environmental health and soil quality. In the present study, we investigated the transport of glyphosate and its main metabolite, aminomethylphosphonic acid (AMPA) via earthworms in the presence of different concentrations of light density polyethylene microplastics in the litter layer during a 14-day mesocosm experiment. The results showed earthworm gallery weight was negatively affected by the combination of glyphosate and microplastics. Glyphosate and AMPA concentrated in the first centimetre of the top soil layer and the downward transport of glyphosate and AMPA was only detected in the earthworm burrows, ranging from 0.04 to 4.25 μg g−1 for glyphosate and from 0.01 (less than limit of detection) to 0.76 μg g−1 for AMPA. The transport rate of glyphosate (including AMPA) from the litter layer into earthworm burrows ranged from 6.6 ± 4.6% to 18.3 ± 2.4%, depending on synergetic effects of microplastics and glyphosate application. The findings imply that earthworm activities strongly influence pollutant movement into the soil, which potentially affects soil ecosystems. Further studies focused on the fate of pollutants in the microenvironment of earthworm burrows are needed.

Glyphosate Transport in Two Louisiana Agricultural Soils: Miscible Displacement Studies and Numerical Modeling

Glyphosate (N-(phosphonomethyl) glycine) (GPS) is currently the most commonly used herbicide worldwide, and is generally considered as immobile in soils. However, numerous reports of the environmental occurrence of the herbicide coupled with recent evidence of human toxicity necessitate further investigation as to the behavior of GPS in the soil environment. Batch sorption studies along with miscible displacement experiments were carried out in order to assess the mobility of GPS in two Louisiana agricultural soils; Commerce silt loam and Sharkey clay. Batch results indicated a high affinity of both soils for solvated GPS, with greater affinity observed by the Sharkey soil. GPS sorption in the Commerce soil was most likely facilitated by the presence of amorphous Fe and Al oxides, whereas the high cation exchange capacity of the Sharkey soil likely allows for GPS complexation with surface exchangeable poly-valent cations. Miscible displacement studies indicate that GPS mobility is highly limited in both soils, with 3% and 2% of the applied herbicide mass recovered in the effluent solution from the Commerce and Sharkey soils, respectively. A two-site multi-reaction transport model (MRTM) adequately described GPS breakthrough from both soils and outperformed linear modeling efforts using CXTFIT. Analysis of extracted herbicide residues suggests that the primary metabolite of GPS, aminomethylphosphonic acid (AMPA), is more mobile in both soils, although both compounds are strongly retained.

Antecedent and Post-Application Rain Events Trigger Glyphosate Transport from Runoff-Prone Soils

Recent environmental surveys report widespread detections of the herbicide glyphosate [N-(phosphonomethyl)glycine] in surface waters, despite its strong immobilization and rapid biodegradation in soils. We performed four high-frequency sampling campaigns (from 2015 to 2017) following controlled spray applications on an experimental perennial grass field site with wetness-prone marginal soils. We monitored dissolved glyphosate concentrations in the outflow (runoff and shallow drainage) using liquid chromatography–mass spectrometry and enzyme-linked immunosorbent assays. Rainfall-triggered outflow events occurred between 3 and 13 days following spray application. Outflow concentrations varied widely from nondetectable levels to 90 μg L–1, peaking during the first significant outflow event in each campaign and diminishing as flows subsided. Subsequent outflow peaks caused concentrations to increase again but to a lesser extent. Cumulative mass efflux in outflow across the different campaigns ranged from 0.06...

Vegetative Buffer Strips for Reducing Herbicide Transport in Runoff: Effects of Buffer Width, Vegetation, and Season

AbstractThe effectiveness of vegetative buffer strips (VBS) for reducing herbicide transport has not been well documented for runoff prone soils. A multi‐year plot‐scale study was conducted on an eroded claypan soil with the following objectives: (1) assess the effects of buffer width, vegetation, and season on runoff transport of atrazine (ATR), metolachlor (MET), and glyphosate; (2) develop VBS design criteria for herbicides; and (3) compare differences in soil quality among vegetation treatments. Rainfall simulation was used to create uniform antecedent soil water content and to generate runoff. Vegetation treatment and buffer width impacted herbicide loads much more than season. Grass treatments reduced herbicide loads by 19‐28% and sediment loads by 67% compared to the control. Grass treatments increased retention of dissolved‐phase herbicides by both infiltration and adsorption, but adsorption accounted for the greatest proportion of retained herbicide load. This latter finding indicated VBS can be effective on poorly drained soils or when the source to buffer area ratio is high. Grass treatments modestly improved surface soil quality 8‐13 years after establishment, with significant increases in organic C, total N, and ATR and MET sorption compared to continuously tilled control. Herbicide loads as a function of buffer width were well described by first‐order decay models which indicated VBS can provide significant load reductions under anticipated field conditions.

Glyphosate sorption/desorption on biochars - interactions of physical and chemical processes.

Biochar, a carbon-rich product of biomass pyrolysis, could limit glyphosate transport in soil and remediate contaminated water. The present study investigates the sorption/desorption behavior of glyphosate on biochars prepared from different hardwoods at temperatures ranging from 350 to 900 °C to elucidate fundamental mechanisms. Glyphosate (1 mg L-1 ) sorption on biochars increased with pyrolysis temperature and was highest on 900 °C biochars; however, total sorption was low on a mass basis (<0.1 mg g-1 ). Sorption varied across feedstock materials, and isotherms indicated concentration dependence. Biochars with a greater fraction of micropores exhibited lower sorption capacities, and specific surface groups were also found to be influential. Prepyrolysis treatments with iron and copper, which complex glyphosate in soils, did not alter biochar sorption capacities. Glyphosate did not desorb from biochar with CaCl2 solution; however, up to 86% of the bound glyphosate was released with a K2 HPO4 solution. Results from this study suggest a combined impact of surface chemistry and physical constraints on glyphosate sorption/desorption on biochar. Based on the observed phosphate-induced desorption of glyphosate, the addition of P-fertilizer to biochar-amended soils can remobilize the herbicide and damage non-target plants; therefore, improved understanding of this risk is necessary. © 2017 Society of Chemical Industry.

Glyphosate and AMPA distribution in wind-eroded sediment derived from loess soil

Glyphosate is one of the most used herbicides in agricultural lands worldwide. Wind-eroded sediment and dust, as an environmental transport pathway of glyphosate and of its main metabolite aminomethylphosphonic acid (AMPA), can result in environmental- and human exposure far beyond the agricultural areas where it has been applied. Therefore, special attention is required to the airborne transport of glyphosate and AMPA. In this study, we investigated the behavior of glyphosate and AMPA in wind-eroded sediment by measuring their content in different size fractions (median diameters between 715 and 8 μm) of a loess soil, during a period of 28 days after glyphosate application. Granulometrical extraction was done using a wind tunnel and a Soil Fine Particle Extractor. Extractions were conducted on days 0, 3, 7, 14, 21 and 28 after glyphosate application. Results indicated that glyphosate and AMPA contents were significantly higher in the finest particle fractions (median diameters between 8 and 18 μm), and lowered significantly with the increase in particle size. However, their content remained constant when aggregates were present in the sample. Glyphosate and AMPA contents correlated positively with clay, organic matter, and silt content. The dissipation of glyphosate over time was very low, which was most probably due to the low soil moisture content of the sediment. Consequently, the formation of AMPA was also very low. The low dissipation of glyphosate in our study indicates that the risk of glyphosate transport in dry sediment to off-target areas by wind can be very high. The highest glyphosate and AMPA contents were found in the smallest soil fractions (PM10 and less), which are easily inhaled and, therefore, contribute to human exposure.

Transport of Glyphosate and Aminomethylphosphonic Acid under Two Soil Management Practices in an Italian Vineyard.

Worldwide, glyphosate is the most widely used herbicide in controlling the growth of annual and perennial weeds. An increasing number of studies have highlighted the environmental risk resulting from the use of this molecule in aquatic and terrestrial ecosystems. The objective of the study was to determine the transport of glyphosate and its degradation product, aminomethylphosphonic acid (AMPA), through runoff and transported sediment from a vineyard under two different soil management systems: harrowed inter-row (HR) and permanent grass covered inter-row (GR). The study was performed over a period of 4 yr. Glyphosate and AMPA concentrations were found to be higher in runoff and in transported sediment from HR compared with GR, regardless of the amount of runoff and transported sediment. The mean annual percentages of glyphosate loss, via runoff and transported sediment, were about 1.37 and 0.73% for HR and GR, respectively. Aminomethylphosphonic acid represented approximately 30.9 and 40.0% of the total glyphosate losses in GR and HR, respectively. Moreover, results suggested that rains occurring within 4 wk after treatment could cause the transport of glyphosate and AMPA in high concentrations. Soil analyses indicated that glyphosate content was below detection within 1 yr, whereas AMPA remained in the soil profiles along the vine row and in the inter-row. Results indicated that GR can reduce soil and herbicide loss by runoff in vineyard cropping system.

Modeling controlled release from hollow porous nanospheres

The kinetics of diffusion-controlled release from hollow nanoporous spheres of varying thickness were investigated using classical mass transport theory. A new model was developed to describe the time-dependent mass transport through the shell. The model was compared with experimental kinetic profiles of transport of glyphosate in hollow silica nanosphere systems. The silica spheres were synthesized via a sacrificial method using poly-(styrene-methyl acrylic acid) spheres as templates, thereby producing shell/core nanospheres with diameters ranging from roughly 367.6 to 406.8nm and shell thicknesses spanning 22.0 to 32.8nm. These nanosphere systems were loaded with glyphosate and then exposed to a reservoir of distilled water. Periodic sampling allowed determination of the glyphosate release kinetics as a function of shell thickness: the release rate decreased and the release period was prolonged by increasing shell thickness. The model was used to estimate the effective diffusivity and predict the concentration profile within the shell as well as the amounts of retained and released glyphosate. According to a scaling expression suggested by the model, it was observed that the amounts of released and retained glyphosate as functions of time could each be superimposed on a universal curve that was independent of shell thickness. Furthermore, the rate of the diffusive process with respect to shell thickness was determined by a single time constant that quantified the kinetics of the diffusive transport. It was also demonstrated that the associated diffusion coefficient of the mass transport must be calculated on a per-sphere rather than a per-mass basis. These results suggest that accurate predictions of time-released drugs and agrochemicals in diffusion-controlled nanosphere systems can be achieved via a single determination of an associated material rate constant. Predictions of the diffusion kinetics of hypothetical nanosphere systems were computed for a variety of experimental parameters, such as shell thickness and porosity.

Adsorption and mobility of glyphosate in different soils under no-till and conventional tillage

Glyphosate (N-(phosphonomethyl) glycine) is a post-emergence, non-selective, foliar herbicide. Around 200millionliters of this herbicide are applied every year in Argentina, where the main agricultural practice is no-till (NT), accounting for 78.5% of the cultivated land. In this work, we studied the adsorption of glyphosate in different soils under long-term management (more than 16years) of NT and conventional tillage (CT). Samples were taken from different regions of Argentina corresponding to: Paraná soil (PAR), a silty clay loam soil (<37% clay), Manfredi (MAN) and Pergamino (PER), both silty loam soils (<26% clay). We found that the adsorption was very high in all the soils, and it was particularly influenced by the soil clay content and CEC and negatively related to pH and phosphorus. In general, the adsorption coefficient (Kf) was higher in the CT samples. We also studied the vertical transport of glyphosate in undisturbed columns (15cm long) and compared the effect of NT and CT. Less than 0.24% of the applied pesticide leached in all soils. No significant difference was found between the total amount of leached glyphosate between soils or tillage practice. The highest glyphosate concentration (67.53% of the initially applied doses) was found in the top 5cm of the columns. The strong retention of glyphosate to the soil matrix, as confirmed by the high Kf values obtained in the isotherm studies, was the dominant factor influencing glyphosate mobility through the soil profile.

Glyphosate and AMPA in the estuaries of the Baltic Sea method optimization and field study

Water samples from ten German Baltic estuaries were collected in 2012 in order to study the presence of the herbicide glyphosate, its primary metabolite AMPA and their potential transport to the marine environment. For the analyses an LC–MS/MS based analytical method after derivatization with FMOC-Cl was optimized and validated for marine water samples. All investigated estuarine stations were contaminated with AMPA and nine of them also with glyphosate. Concentration ranges observed were 28 to 1690ng/L and 45 to 4156ng/L for glyphosate and AMPA, respectively with strong spatial and temporal fluctuations. Both contaminants were found at inbound sampling sites in the stream Muehlenfliess and concentrations decreased along the salinity gradient to the estuaries of the Baltic Sea. The data obtained in this study clearly depict the transport of glyphosate and AMPA to the Baltic Sea. Hence, detailed fate and risk assessment for both contaminants in marine environments are required.

Decay characteristics and erosion-related transport of glyphosate in Chinese loess soil under field conditions

The decay characteristics and erosion-related transport of glyphosate and aminomethylphosphonic acid (AMPA) were monitored for 35d at different slope gradients and rates of application in plots with loess soil on the Loess Plateau, China. The initial glyphosate decayed rapidly (half-life of 3.5d) in the upper 2cm of soil following a first-order rate of decay. AMPA content in the 0–2cm soil layer correspondingly peaked 3d after glyphosate application and then gradually decreased. The residues of glyphosate and AMPA decreased significantly with soil depth (p<0.05) independently of the slope inclination and application rate. About 0.36% of the glyphosate initially applied was transported from plots after one erosive rain 2d after the application. Glyphosate and AMPA concentrations in runoff were low while the contents in the sediment were much higher than in the upper 2cm of the soil. CapsuleAlthough the rate of glyphosate decay is rapid in Chinese loess soil, the risks of glyphosate and AMPA need to be taken into account especially in the area with highly erosive rainfall.