A modified method for pesticide transport and fate in subsurface environment of a winter wheat field of Yangling, China

Multi-objective winter wheat irrigation strategies optimization based on coupling AquaCrop-OSPy and NSGA-III: A case study in Yangling, China

The contradiction between crop water requirements and water supplies in Guanzhong Plain of Northwest China restricts the production of local winter wheat. The optimization of irrigation strategies considering multiple-objectives is of great significance to alleviate water crisis and sustainability of winter wheat production. This paper considered three typical hydrological years (dry year, normal year, and wet year), and a simulation optimization model coupling AquaCrop and NSGA-III was developed using Python language. The multi-objective optimization problem considered four objectives: (1) maximize crop yield (Y), (2) minimize irrigation water (IW), (3) maximize irrigation water productivity (IWP), and (4) maximize water use efficiency (WUE). The TOPSIS-Entropy method was then adopted for decision-making based on the Pareto fronts which were generated by multi-objective optimization, thus facilitating the optimization of the irrigation strategies. The results show that AquaCrop model could accurately simulate the growth process of winter wheat in the study area, the relative error is acceptable. The R² of canopy cover (CC) is 0.75 and 0.61, and above ground biomass production (B) is 0.94 and 0.93, respectively. In the Pareto fronts, the difference between the maximum and minimum yield of winter wheat is 9.48 %, reflecting the diversity of multi-objective optimization results. According to the analysis results of this paper, the performance of different irrigation scenarios in each typical year varies greatly. The performance of the optimization in dry years is significantly better than that in normal years and wet years. The optimization of irrigation strategies and comparison of different scenarios play a positive role in improving the local water use efficiency, the winter wheat yield, as well as the sustainable development level of water resources.

Improving screening model of pesticide risk assessment in surface soils: Considering degradation metabolites

As pesticides can be degraded to toxic metabolites in the soil, metabolite toxicity should be considered in human health risk assessments. In this study, a screening-level modeling framework was developed to manage pesticides in surface soil, which was discussed under discrete and continuous emission scenarios. In addition, we selected glyphosate and its major metabolite (aminomethylphosphonic acid or AMPA) as examples to conduct screening-level risk management at regional, national, and global scales. The results indicated that if soil AMPA were not considered, human health risks could be significantly underestimated because of the large half-life of AMPA in the soil. For example, the added concentration factors of AMPA were simulated as 0.19 and 6.72 considering all major elimination pathways and considering the degradation pathway alone, respectively, indicating that AMPA formation could lead to severe extra health burdens. Furthermore, the evaluation of current glyphosate soil standards suggested that toxic metabolites should be considered in the regulatory process; otherwise, many standards could theoretically trigger high levels of soil AMPA, which could result in serious human health damage. Our proposed screening-level model can help to improve risk assessment and regulatory management of pesticides in surface soils.

Agriculture Development, Pesticide Application and Its Impact on the Environment

Pesticides are indispensable in agricultural production. They have been used by farmers to control weeds and insects, and their remarkable increases in agricultural products have been reported. The increase in the world's population in the 20th century could not have been possible without a parallel increase in food production. About one-third of agricultural products are produced depending on the application of pesticides. Without the use of pesticides, there would be a 78% loss of fruit production, a 54% loss of vegetable production, and a 32% loss of cereal production. Therefore, pesticides play a critical role in reducing diseases and increasing crop yields worldwide. Thus, it is essential to discuss the agricultural development process; the historical perspective, types and specific uses of pesticides; and pesticide behavior, its contamination, and adverse effects on the natural environment. The review study indicates that agricultural development has a long history in many places around the world. The history of pesticide use can be divided into three periods of time. Pesticides are classified by different classification terms such as chemical classes, functional groups, modes of action, and toxicity. Pesticides are used to kill pests and control weeds using chemical ingredients; hence, they can also be toxic to other organisms, including birds, fish, beneficial insects, and non-target plants, as well as air, water, soil, and crops. Moreover, pesticide contamination moves away from the target plants, resulting in environmental pollution. Such chemical residues impact human health through environmental and food contamination. In addition, climate change-related factors also impact on pesticide application and result in increased pesticide usage and pesticide pollution. Therefore, this review will provide the scientific information necessary for pesticide application and management in the future.

A simple method of transport parameter estimation for slug injecting tracer tests in porous media

Slug (instantaneous injection) tracer tests can be used effectively to determinate solute transport parameters in porous media such as pore velocities and dispersivities, which are usually estimated with curve-fitting methods. This study proposes a simple method to estimate conservative and reactive solute transport parameters in one-, two- and three- dimensional domains with uniform flow fields based on peak times of slug tracer tests. This method requires fewer measured data than traditional curve-fitting methods. The accuracy of the method depends on the time-interval of measurement that is the time interval used in collecting observed concentrations of solutes. The error of the pore velocity estimate is very small (less than 3%) even for a relatively large time-interval of measurement. The error of the dispersivity estimate increases with the time-interval (Δt) of measurement significantly. For 1-D case, the relative error increases from 0.29% at ∆t of 0.1 min to 17.12% at ∆t of 6 min. Such an error can be reduced by refining the time-interval of measurement near the actual peak time of breakthrough curves. The error of the dispersivity estimate decreases when the retardation factor increases. The first-order decay rate constant in the liquid hardly influences the accuracies of both pore velocity and dispersivity estimates. The proposed method is applied on laboratory sand column tests. The results indicate that the estimated pore velocities and dispersivities are almost the same to that of the curves-fitting method. This method can be employed easily by scientists and practitioners for parameter estimations in laboratory column experiments if advection-dispersion equation is applicable. This method can also be used for parameter estimation of heat transport in a laboratory column experiment if a slug heat source is injected into a porous media with the presence of a uniform flow field. Limitations of the study have also been addressed.

Effects of rainfall intensity and slope gradient on runoff and sediment yield characteristics of bare loess soil

Soil erosion is a universal phenomenon on the Loess Plateau but it exhibits complex and typical mechanism which makes it difficult to understand soil loss laws on slopes. We design artificial simulated rainfall experiments including six rainfall intensities (45, 60, 75, 90, 105, 120 mm/h) and five slopes (5°, 10°, 15°, 20°, 25°) to reveal the fundamental changing trends of runoff and sediment yield on bare loess soil. Here, we show that the runoff yield within the initial 15 min increased rapidly and its trend gradually became stable. Trends of sediment yield under different rainfall intensities are various. The linear correlation between runoff and rainfall intensity is obvious for different slopes, but the correlations between sediment yield and rainfall intensity are weak. Runoff and sediment yield on the slope surface both presents an increasing trend when the rainfall intensity increases from 45 mm/h to 120 mm/h, but the increasing trend of runoff yield is higher than that of sediment yield. The sediment yield also has an overall increasing trend when the slope changes from 5° to 25°, but the trend of runoff yield is not obvious. Our results may provide data support and underlying insights needed to guide the management of soil conservation planning on the Loess Plateau.

Toxicological analysis of triadimefon on endocrine disruption and oxidative stress during rare minnow (Gobiocypris rarus) larvae development

Triadimefon (TDF) is a systemic wide-spectrum antifungal compound that is widely used in agriculture to inhibit fungal growth on various crops. Since previous studies focused on the embryo and adult life stages in the investigation of ecological impact, here we investigated the long-term effects of TDF (1, 10, 100 μg/L) on rare minnow during its larvae development. TDF caused an anti-estrogenic effect by decreasing vitellogenin (VTG) and CYP19a mRNA level, and inhibiting the aromatase activity and VTG levels after a 3, 6, 10, or 14-day exposure in rare minnow larvae. TDF also disturbed the endocrine disruption by regulating the transcription of estrogen receptors ERα, ERβ1 and ERβ2, CYP1a, CYP11, CYP17, steroidogenic acute regulator (STAR), doublesex and mab-3 related transcription factor (DMRT1), gonadotropin-releasing hormone (GnRH2), GnRH3, GnRHR1A, and GnRHR1B. Furthermore, TDF induced the accumulation of reactive oxygen species (ROS) and the activity of antioxidant proteins glutathione peroxidase (GPX), superoxide dismutase (SOD), and catalase (CAT), and significantly increased the transcriptions of stress response genes P53, growth arrest and DNA damage-inducible 45 alpha (Gadd45α), and COX1, suggested that TDF might cause oxidative stress during larvae development. The changes in transcript and biological levels represented the potential adaptive or compensatory responses to impaired oxidative stress and endocrine system after TDF exposure in rare minnow during its larvae development.