Quantification of agricultural plastic debris loss through soil erosion and associated phthalic acid esters emissions into the aquatic environment.

Terrestrial agricultural plastic film (APF) residue migration triggered by soil erosion constitutes a primary disruption in the plastic waste cycle. However, the migration mechanisms of APF residue and phthalate acid esters (PAEs) emissions from APF debris into China's aquatic environment remain inadequately understood. This study assessed APF residue loss induced by soil erosion and the associated PAEs emissions from 14 crop categories across China for 1998-2020, employing an integrated estimation framework and high-resolution agricultural activity data. Our findings indicate that the APF residue loss ranged in 968.95-2081.76 tons yr-1 during the study period, peaking in 2016. Areas with high APF residue losses were concentrated in southwestern, central, northwestern, northeastern, northern, and eastern China. Moreover, PAEs emitted from APF debris ranged in 29.57-59.42 kg yr-1 over the same period, with emission hotspots identified in northwestern, southwestern, and eastern China. The APF application, meteorological factors, and soil properties collectively accounted for 33.82 %, 33.33 %, and 13.66 % of the total variance, respectively. Finally, the potential ecological risk posed by PAEs to the aquatic environment was found to be low. Overall, our findings offer crucial insights into the dynamics of plastic contamination and provide foundational knowledge for safeguarding aquatic environments in China.

Mechanical and friction properties of agricultural plastic film during autumn harvest period of cotton in Xinjiang, China.

Agricultural plastic films have caused serious plastic pollution. There are many studies that consider mechanical recycling an appropriate system for the recovery of post-consumption agricultural mulch film. The recovery effect of plastic film depends on the mechanical properties, the level of dirtiness of the post-consumption film, and the recycling process itself. In this study, the mechanical properties of four types of polyethylene plastic films with a thickness of 8, 10, 12, and 10 µm, weather-resistant, commonly used in Xinjiang cotton fields, were tested. As well as the friction coefficient between the film and soil, the cotton stalk, boll shell, and leaf with different moisture contents were measured. Then, the self-propelled straw chopping and residual film recycling combined machine collected the four types of mulch films. The results showed that the longitudinal mechanical properties of the plastic film were greater than the transversal ones, with the exception of the nominal tensile strain at break, and the tensile characteristics of the mulching film covered with soil were greater than those without soil. The dynamic or static friction coefficient between the film and the contact material had a linear relationship with the moisture content of the material. During the recycling operation, the better the mechanical properties of the plastic film, the higher the pick-up rate of the mulch film. The maximum longitudinal tensile force of 12-µm plastic film was 3.42 N, and the nominal tensile strain at break was 303.09%. The pick-up rate reached more than 93% when the 12-µm plastic film was recovered in autumn, which effectively reduced the residue of plastic film coverage in the current year. Moreover, the more soil that was present on the much film, the greater the soil content of the recycled film roll, and the stalk content also increased, but the change was small. The research provides a reference for the mechanical and the friction features of agricultural plastic film in Xinjiang, and provides a theoretical basis for the formulation of standards for film thickness and mechanical properties, as well as the design and optimization of a residual film collecting machine in the cotton field.

Selection and evaluation of microorganisms for biodegradation of agricultural plastic film.

Three Bacillus amyloliquefaciens isolates (HK1, GSDM02, and GSDM15) were tested for effectiveness in biodegradation of plastic films. Isolates were screened by plate on carbon-free medium and by using the clear-zone formation test. Their biodegradation ability was analyzed based on: film weight reduction, pH change of the fluid medium, a soil microbial biomass carbon test, scanning electron microscopy (SEM), and Fourier transform infrared spectrometry (FTIR). Polyvinyl alcohol (PVA) clear-zone and film weight reduction results revealed that the strain with a bigger clear-zone had a better biodegradation effect, that PVA can be evenly distributed in the medium, and that PVA can be a substitution for polyethylene in screening the biodegradation of strains. SEM and FTIR revealed that HK1 can tear the film apart and make surface chemical changes within 30 days. HK1 exhibited a better biodegradation effect in all tests, indicating its potential for helping solve the plastic pollution problems.

A national assessment of the effect of intensive agro-land use practices on nonpoint source pollution using emission scenarios and geo-spatial data.

China's intensive agriculture has led to a broad range of adverse impacts upon ecosystems and thereby caused environmental quality degradation. One of the fundamental problems that face land managers when dealing with agricultural nonpoint source (NPS) pollution is to quantitatively assess the NPS pollution loads from different sources at a national scale. In this study, export scenarios and geo-spatial data were used to calculate the agricultural NPS pollution loads of nutrient, pesticide, plastic film residue, and crop straw burning in China. The results provided the comprehensive and baseline knowledge of agricultural NPS pollution from China's arable farming system in 2014. First, the nitrogen (N) and phosphorus (P) emission loads to water environment were estimated to be 1.44 Tg N and 0.06 Tg P, respectively. East and south China showed the highest load intensities of nutrient release to aquatic system. Second, the amount of pesticide loss to water of seven pesticides that are widely used in China was estimated to be 30.04 tons (active ingredient (ai)). Acetochlor was the major source of pesticide loss to water, contributing 77.65% to the total loss. The environmental impacts of pesticide usage in east and south China were higher than other parts. Third, 19.75% of the plastic film application resided in arable soils. It contributed a lot to soil phthalate ester (PAE) contamination. Fourth, 14.11% of straw produce were burnt in situ, most occurring in May to July (post-winter wheat harvest) in North China Plain and October to November (post-rice harvest days) in southeast China. All the above agricultural NPS pollution loadings were unevenly distributed across China. The spatial correlations between pollution loads at land unit scale were also estimated. Rising labor cost in rural China might be a possible explanation for the general positive correlations of the NPS pollution loads. It also indicated a co-occurred higher NPS pollution loads and a higher human exposure risk in eastern regions. Results from this research might provide full-scale information on the status and spatial variation of various agricultural NPS pollution loads for policy makers to control the NPS pollution in China.

Rapid fabrication of TiO2@carboxymethyl cellulose coatings capable of shielding UV, antifog and delaying support aging.

Agricultural plastic films capable of shielding UV, filtering visible light and antifog are important to prolong their life and protect safeties of agriculturists and crops. In this work, high stable and small size TiO2@polymer nanoparticles (NPs) were prepared by an efficient one-pot microwave synthesis using titanic sulfate as Ti resource, carboxymethyl cellulose sodium (CMC) as complexing agent and stabilizer. The TiO2@CMC NPs obtained were then utilized to fabricate poly(ethylene imine) (PEI)/TiO2@CMC coatings on the surface of polypropylene films by a layer-by-layer assembly technique. The TiO2@CMC NPs show rapid deposition rate because small, spherical and anion-rich TiO2@CMC NPs possess large specific surface area and fast diffusion rate. More importantly, property experiments confirm that (PEI/TiO2@CMC)*15 coatings can not only effectively shield UV rays, filter visible light and prevent fogging but also delay the aging of their supports.