Self-assembly of eugenol-loaded particles to regulate the adhesion of carriers on leaves for efficient foliar applications and ecotoxicological safety

Currently, there is a pressing need to develop an agrochemical-loaded system that is both uncomplicated and efficient, thereby enhancing the adhesion of agrochemical to leaf surfaces and optimizing their insecticidal efficacy, while concurrently mitigating environmental risks. The flexible eugenol-loaded particles were synthesized via a one-step polyurethane self-assembly reaction, utilizing polyethylene glycol (PEG) as the soft segment and 4,4-diphenylmethane diisocyanate (MDI) as the hard segment. The increase in the length of the soft segment enhances the flexibility of the particles, thereby improving the contact area and adhesion with the foliar surface. When flexible particles are applied on the foliar surface, they can achieve satisfactory resistance to rainfall erosion. When the PEG molecular weight is 800, the residual concentration of eugenol can still reach 42.11% after 6 washes. The carrier protects the active ingredients and improves the resistance to ultraviolet irradiation. After 5 h of ultraviolet irradiation, the concentration of eugenol remained at 59.03% when PEG with a molecular weight of 200 was employed. Greenhouse experiments showed that the flexible transformation of particles greatly enhanced the application effect of spray on the foliar surface of particles. After undergoing three washes, the mortality of the particles can be enhanced by 5.4-8.4 times compared to that of emulsion concentrate (EC) sample. The enhancement of leaf retention performance reduces environmental risks caused by pesticide loss. Meanwhile, the controlled release of particles also reduces the acute toxicity to zebrafish. The toxicity selection pressure of the EUG@P800-Ps sample is 10.6 times that of the EC sample. In conclusion, the preparation process of the system is simple, and the flexible transformation is an effective strategy to improve the foliar application effect of spray and improve the environmental safety.

Research on freeze-thaw and dry-wet durability of enzymatic calcification for surface protection

The enzymatically induced carbonate precipitation (EICP) technique is currently studied for dust control because of the formation of cemented crust layer. In the present study, polyvinyl acetate (PVAc) was used with EICP together as the EICP-PVAc treatment to solidify dust soils. In addition, several treated dust soil areas always experience repeated freeze-thaw (FT) or dry-wet (DW) cycles, both of which result in the damage of structure. Therefore, the FT cycle test and the DW cycle test were conducted to study the durability of EICP-PVAc treatment. Results showed that both FT cycles and DW cycles affected the EICP-PVAc-treated dust soils. The wind-erosion resistance and rainfall-erosion resistance were impaired, and the surface strength decreased. However, the decreasing range resulted from the FT cycle was smaller than the decreasing range resulted from the DW cycle. It indicated the EICP-PVAc-treated dust soils had better FT durability, but the DW durability was worse. Moreover, a field test was used to study the durability of application of EICP-PVAc treatment in practical field test site. Based on the surface pattern observation after 9 months, the grasses in the treated area are in good growth condition; however, few grasses grew in the untreated area. The field test demonstrated that the combined EICP-PVAc and grass seeds treatment can ensure the long-term solidification effect and durability. The results lay a solid foundation for the applications of EICP-PVAc treatment to solidify dust soils for dust control.

Mineralization crust field experiment for desert sand solidification based on enzymatic calcification

Sandstorms have been recognized as severe natural disasters worldwide and it is of great significance to propose an effective and environmentally friendly method to combat sandstorm. In this study, the enzymatic calcification (EC) treatment technology was used for mineralization crust and desert sand solidification. Both laboratory experiments and field site tests were conducted to demonstrate the feasibility of EC treatment to improve wind-erosion resistance and rainfall-erosion resistance. Results showed that with the concentration of reactants higher than 0.25 M or the ratio of urease solution to the cementation solution above 0.8, the improvement effects of wind-erosion resistance and rainfall-erosion resistance decreased. Therefore, the 0.25 M of reagent concentration and 0.8 of ratio of urease solution to the cementation solution were chosen for subsequent field site test. The two test sites had similar CaCO₃ contents, thus obtaining a similar increasing range of surface strength. However, the test site one had larger surface strengths due to thicker cemented crust layers. Both the two test sites had sufficient wind-erosion resistance because of crust layer. Moreover, rainfalls decreased surface strength; the surface strength recovered to a high level after water evaporation. In addition, the effect of rainfall on thickness of crust layer and CaCO₃ was small. The EC treatment had good ecological compatibility, and the combined EC and grass seed treatment was effective for mitigation of desertification. The results demonstrated that EC treatment significantly improved both wind-erosion and rainfall-erosion resistance, which presents promising potential for anti-desertification.

Application of enzymatic calcification for dust control and rainfall erosion resistance improvement

Globally, most cities are facing severe challenges associated with dust pollution and it is of great significance to propose an effective and environmentally friendly dust control method. This study used enzymatically induced calcite precipitation (EICP) technology for dust control. Moreover, polyvinyl acetate (PVAc) was added to the cementation solution to improve its rainfall erosion resistance. The results showed that the optimum ratio of urease solution to cementation solution differed according to the concentrations of reactants in the cementation solution. Under combined EICP and PVAc (50 g/L) treatment, the stability of the dust-slope significantly improved. Moreover, little dust soil loss was washed out by simulated rainfall because of the more stable spatial structure of CaCO₃ precipitation. Furthermore, PVAc addition increased the surface strength of slopes, while the cemented layer became thinner. With this combined EICP and PVAc (50 g/L) treatment, in a field test, the treated area of the slope had higher surface strengths and stronger erosion resistance than untreated areas. These higher surface strengths were attributed to the smaller particle size, and the stronger cementing effect of grass seeds. These results demonstrated that EICP-PVAc treatment significantly controlled dust and mitigated surface erosion of dust-slopes. This represents promising potential for the prevention of dust pollution.

A comparison of the abilities of the USLE-M, RUSLE2 and WEPP to model event erosion from bare fallow areas

Traditionally, the Universal Soil Loss Equation (USLE) and the revised version of it (RUSLE) have been applied to predicting the long term average soil loss produced by rainfall erosion in many parts of the world. Overtime, it has been recognized that there is a need to predict soil losses over shorter time scales and this has led to the development of WEPP and RUSLE2 which can be used to predict soil losses generated by individual rainfall events. Data currently exists that enables the RUSLE2, WEPP and the USLE-M to estimate historic soil losses from bare fallow runoff and soil loss plots recorded in the USLE database. Comparisons of the abilities of the USLE-M and RUSLE2 to estimate event soil losses from bare fallow were undertaken under circumstances where both models produced the same total soil loss as observed for sets of erosion events on 4 different plots at 4 different locations. Likewise, comparisons of the abilities of the USLE-M and WEPP to model event soil loss from bare fallow were undertaken for sets of erosion events on 4 plots at 4 different locations. Despite being calibrated specifically for each plot, WEPP produced the worst estimates of event soil loss for all the 4 plots. Generally, the USLE-M using measured runoff to calculate the product of the runoff ratio, storm kinetic energy and the maximum 30-minute rainfall intensity produced the best estimates. As to be expected, ability of the USLE-M to estimate event soil loss was reduced when runoff predicted by either RUSLE2 or WEPP was used. Despite this, the USLE-M using runoff predicted by WEPP estimated event soil loss better than WEPP. RUSLE2 also outperformed WEPP.