In the context of pesticide pollution in hydrosystem, limiting pesticide transfer from agricultural plot to surface waterbodies appears to be crucial. Two constructed wetlands were tested at both pilot scale of an experimental constructed wetland and field scale of the outfall of a subsurface drained watershed. Tracer experiment and pesticide mass balance studies allowed us to assess the dissipation potential of a subsurface flow constructed wetland. At field scale, climatic parameters water and pesticide's flows in and out have been measured and monitored. We also recorded the conditions of implementation since we were very closed to real conditions. For this purpose inquiries addressing the various actors were carried out by sociologists. The results of the performance regarding pesticide's dissipation are given mentioning that efficiency is strongly linked to pesticide properties and hydrological transfer period (from 20 to 90% of pesticide removal). Sociologic approaches and amenities assessments have revealed unsuspected relations of the farmers with the society and the environment, and vice versa. The implementations have resulted of a co-construction where each actor had personal involvement. Even if co-construction should be a driving line, solutions for appropriate incentives and land reallocation tools should be fought with politics and authorities in order to facilitate further realisations.

Transport of pesticides from point of application via sub-surface drains can contribute significantly to contamination of surface waters. Results of 23 field drainage experiments undertaken at sites across Europe were collated and analysed by residual maximum likelihood. Both maximum concentration of pesticide in drainflow (n = 167) and seasonal loss of pesticide to drains (n = 97) were significantly related to strength of pesticide sorption to soil, half-life of the pesticide in soil, the interval between application and first drainflow and the clay content of the soil. The statistical models accounted for 71% of the variability in both maximum concentration and seasonal load. Next, the dataset was used to evaluate the current methodology for assessment of aquatic exposure used in pesticide registration in Europe. Simulations for seven compounds with contrasting properties showed a good correspondence with field measurements. Finally, the review examines management approaches to reduce pesticide transport via sub-surface drains. Despite a large amount of work in this area, there are few dependable mitigation options other than to change application rate or timing or to restrict use of a compound in the most vulnerable situations. Chemical and environmental factors influence pesticide transfer to water via drains.

Animal hormones can enter the aquatic environment along with runoff as a result of manure or litter application on agricultural landscapes. Our understanding of the transport of these hormones and their concentrations at various points along the watershed drainage is however limited. We investigated the transport of naturally produced poultry hormones in an agricultural watershed located on coastal plain soils of Delaware receiving land application of raw poultry manure. The objective of this study was to determine the concentrations of free and conjugated forms of estrogens in agricultural runoff at selected landscape positions in the agricultural watershed. Estrogen concentrations were determined for surface water, soil water, and runoff sediment. Estrogen forms that were analyzed were: Estrone (E1), Estradiol (E2β and E2α), Estriol (E3), and their sulfate and glucuronide conjugates. Poultry litter application occurred at a rate of 9 Mg ha⁻¹ in early spring (April 2010). Sampling was performed for surface runoff, subsurface drainage, and sediment for nine storm events extending over 187 days before and after manure application (March–October 2010). Runoff was collected from the field edge, upland and lowland riparian positions and from the stream. Samples were analyzed by for liquid chromatography with tandem mass spectrometry (LC-MS/MS). Concentrations of estrogens were low (<20 ng l⁻¹) for most of the samples and decreased from the field edge into the riparian zone. Estrogens were not detected in soil water and runoff sediments. Overall, this study suggests that manure application practices at our sites in Delaware such as incorporation of litter into the soil likely reduced the concentrations of estrogens in runoff and reduced the threat posed to aquatic ecosystems.

Drainage water from agricultural fields with applied manure can degrade the bacterial quality of surface and groundwater. The impact of conventional tillage (CT) and zero tillage (ZT) practices on Escherichia coli (E.coli) discharge through artificially drained soils is not well understood. Consequently, two field trials were conducted during 2002–2004. The first trial involved fall applications of beef manure while the second involved spring applications of dairy manure. Both surface and subsurface drainage water were monitored in the first trial while only subsurface drainage water was monitored in the second. Under fall applied beef manure (trial 1), no differences (p > 0.05) were observed in E.coli concentrations (cfu/100 ml) in combined drainage water under both tillage systems. However, during 2003–2004, subsurface drainage water under ZT had higher E.coli concentrations and loads than drainage water under CT. When the combined (surface + subsurface) annual E.coli loads were considered, CT loads were greater than ZT during 2002–2003 with an opposite situation during 2003–2004. Overall, annual E.coli loads were similar under ZT (4.7 × 10¹⁰ cfu/ha) and CT (4.8 × 10¹⁰ cfu/ha). Spring dairy manure application (trial 2) produced significant (p > 0.03) tillage effect on E.coli loads in subsurface drainage water only during the second year. During the study period, ZT plots (1.55 × 10¹⁰ cfu/ha) discharged 5× more E.coli than CT (0.23 × 10¹⁰ cfu/ha). A longer duration of ZT practices resulted in higher subsurface flow volumes and subsequently greater loads of E.coli discharge in both trials.

Subsurface tile drainage systems with drainspacings of 15 m in 0.4 ha and 25 m in 3.2 ha wereinstalled at the farmers' field in 1986 and 1987,respectively, to study their effect on the reclamationof the coastal saline sodic clay soils. The system'sperformance in terms of the changing physical andchemical properties of the soil and rice yield wascontinuously monitored for a decade. Field datasuggested the possibility of adopting wider drainspacings and thus, drainage system with 35 and 55 mspacings was laid in 1997 in a 4 ha area. On theseinstallations the losses of NH₄ ⁺-N throughsub-surface drainage effluent were estimated. Thearea under 25 m drain spacing was the control with nocrops, fertilization and irrigation. Analysis ofwater samples collected daily for 10 days startingfrom 40 DAT from the drain laterals revealed thatthere were no trace of NH₄ ⁺-N in theeffluent from 15 and 25 m drain spacings. However,the effluent from 35 and 55 m spacings contained anaverage of 6.704 mg L⁻¹ and 4.205 mg L⁻¹ of NH₄ ⁺-N, respectively, before irrigation and2.438 and 1.650 mg L⁻¹ after irrigation. Themagnitudes of the losses of NH₄ ⁺-N duringthe crop season were 6.43 kg ha⁻¹ in 35 m spacingwith a drainage rate of 5.6 mm d⁻¹ and 2.14 kgha⁻¹ in 55 m spacing with a drainage rate of 3.5 mm d⁻¹. The rice yield was 6.5 Mg ha⁻¹ in15 m drain spacing where no ammonium losses throughsubsurface drainage effluent occurred. The rice yieldsunder 35 and 55 m drain spacings were 1.9 and 1.8 Mgha⁻¹, respectively. The poor yield was due tosignificant loss of ammonium form of nitrogen throughthe drainage effluent and lesser availability of totalnitrogen to the plants. The plant uptake of nitrogen in the unreclaimed area with 55 m spacing was half ofthat in the reclaimed area with 15 m spacing.

Diverting the infiltrating water away from the zone of N application can reduce nitrate-nitrogen (NO₃-N) leaching losses to groundwater from agricultural fields. This study was conducted from 2001 through 2005 to determine the effects of N-application methods using a localized compaction and doming (LCD) applicator and spoke injector on NO₃-N leaching losses to subsurface drainage water and corn (Zea mays L.)-soybean (Glycine max L.) yields. The field experiments were conducted at the Iowa State University's northeastern research center near Nashua, Iowa, on corn-soybean rotation plots under chisel plow system having subsurface drainage ‘tile' system installed in 1979. The soils at the site are glacial till derived soils. The N-application rates of 168 kg-N ha⁻¹ were applied to corn only for both the treatments each replicated three times in a randomized complete block design. For combined 5 years, the LCD N-applicator in comparison with spoke injector showed lower flow weighted NO₃-N concentrations in tile water (16.8 vs. 20.1 mg L⁻¹) from corn plots, greater tile flow (66 vs. 49 mm), almost equivalent NO₃-N leaching loss with tile water (11.5 vs. 11.3 kg-N ha⁻¹) and similar corn grain yields (11.17 vs. 11.37 Mg ha⁻¹), respectively, although treatments effects were found to be non-significant (p = 0.05) statistically. The analysis, however, revealed that amount and temporal distribution of the growing season precipitation also affected the tile flow, NO₃-N leaching loss to subsurface drain water, and corn-soybean yields. Moreover, the spatial variability effects from plot to plot in some cases, resulted in differences of tile flow and NO₃-N leaching losses in the range of three to four times despite being treated with the same management practices. These results indicate that the LCD N-applicator in comparison with spoke injector resulted in lower flow weighted NO₃-N concentrations in subsurface drain water of corn plots; however, strategies need to be developed to reduce the offsite transport of nitrate leaching losses during early spring period from March through June.

The objective of this study was to check the effect of the use of a physico-chemical treatment on the clogging process of horizontal subsurface flow constructed wetlands by means of dynamic modelling. The hydraulic submodel was based on series as well as parallel branched complete stirred tanks of equal volume. The model was validated with data obtained from 2 identical experimental wetlands, which had a surface area of 0.54 m² and a water depth of 0.30 m, and that were monitored over a period of 5 months. One of the wetlands was fed with settled urban wastewater, whereas the other with the same wastewater, but previously treated with a physico-chemical treatment. In the model, pore volume reduction depends on the growth of bacteria and on solids retained. The effluent concentrations of COD and ammonium in both experimental wetlands were very similar in all the conditions tested, and therefore the physico-chemical treatment did not improve the removal efficiency. The model indicated that after 120 days of operation in some regions of the wetland fed with settled wastewater the porosity decreased in a 17%, whereas in the other wetlands it only decreased as much as 6%. The use of a prior physico-chemical treatment is a good alternative for avoiding an anticipated clogging of subsurface flow constructed wetlands.

In this study, the experimental and kinetic modeling investigations were performed to evaluate the ability of mesoporous and microporous canola stalk-derived activated carbon (CSAC) on 2,4-dichlorophenoxyacetic acid (2,4-D) removal from synthetic and natural water in both batch and continuous systems. Three empirical models (pseudo-first-order equation (PFOE), pseudo-second-order equation (PSOE), and the Elovich equation (EE)) and three theoretical models (film diffusion model (FDM), particle diffusion model (PDM), and second-order chemical reaction rate model (SOCRRM)) were compared in terms of diffusion coefficients, maximum 2,4-D adsorption, and rate constants at various operating conditions. CSAC was prepared at 600 °C and activated with water steam under a controlled flow and subsequently characterized by various analytical methods. The results showed that the maximum 2,4-D uptake by CSAC was achieved as 135.8 mg g⁻¹ under a pH of 2 and an initial 2,4-D concentration of 150 mg L⁻¹. The CSAC removed 38.3% of Na⁺, 43.49% of K⁺, 8.96% of Mg²⁺, 45.14% of Ca²⁺, 17.2% of Cl⁻¹, 39.48% of HCO₃⁻, 63.74% of SO₄²⁻, and 100% of the herbicide from agricultural subsurface drainage water and also retained its usability after regenerated by acetone for five cycles. It was concluded that the 2,4-D was adsorbed on the surface of the CSAC through its aromatic ring interaction with the reactive functional groups of the adsorbent. The model result indicated that the PDM is the best-fitting kinetic model for the adsorption of 2,4-D by CSAC, followed by FDM, SOCRRM, PSOE, PFOE, and EE. The mass balance equation based on PDM describes the dynamic behavior of the column satisfactorily. Graphical abstract

Leaching of nitrogen (N) and phosphorus (P) from agricultural lands can cause serious environmental problems such as eutrophication. The objective of this study was to investigate the impacts of biochar application, tillage practices, and irrigation systems on nitrate and dissolved phosphorus (DP) concentrations in subsurface drainage water and grain yield of winter wheat using a strip-split plot design with 3 replications. Irrigation at three different levels (flood (Ifₗ), furrow (Ifᵤ), and sprinkler (Iₛ) systems) considered as main factor, tillage at two levels (reduced tillage (Tᵣ) and conventional systems (Tc)) as subplot factor, and bagasse biochar at two levels (without biochar (B₀) and 20 ton ha⁻¹ biochar (B₁)) as sub-subplot factor. Polyvinyl chloride (PVC) standpipes were used in each sub-subplot to collect leachate water at 100-cm depth. The results indicated that irrigation had significant effects on yield, collected water volume (CWV), nitrate, and DP concentrations (P < 0.01). Interaction of tillage and irrigation was significant for grain yield (P < 0.05). Biochar application only caused a significant decrease in nitrate concentration under sprinkler irrigation (P < 0.05), while no significant impact was observed under flood and furrow irrigation systems. Under sprinkler irrigation, the total nitrate collected in the PVC standpipes decreased by 37.51 and 34.29% compared with flood and furrow irrigations, respectively. Biochar application reduced the total nitrate collected by 16.84%, while difference among tillage treatments was negligible (4.51%). The total DP collected under sprinkler irrigation was lower in comparison with flood and furrow irrigations by 42.24 and 38.76%, respectively. Biochar application reduced the total DP collected by 10.84%, while reduced tillage increased the total DP collected by 8.90% compared with the conventional tillage.