There has been an increasing interest in the pollution caused by meso- and microplastics (MMPs) in terrestrial ecosystems. Mulch film was once considered to be the most important source of MMPs in the mulching cultivated soil. However, the academic community has not given sufficient scientific evidence. In this study, stratified random sampling method was used to selectively interview households in Hebei province, China (400 households, 20 villages, 5 counties). Finally, household characteristics and mulch film use behavior of 41 households were collected, and corresponding soil samples were sampled. The results showed that 1) the abundance of MMPs was 29.3 ± 33.1 items·kg⁻¹ (DW) and the particle size of MMPs was 2.95 × 10³±1.75 × 10³ μm, and the proportion of MMPs derived from Polyethylene (PE) was only 18.8%; 2) the mass of MMPs was 2.90 ± 3.72 mg kg⁻¹ (DW) and the proportion of PE MMPs was 43.75%, which has the highest mass percentage; 3) After controlling the endogenous and dummy variables, the use history of mulch film (HistMF) was found to be positively correlated to the abundance of MMPs and inversely correlated to the particle size, but nor with the mass of MMPs; 4) Regarding the heterogeneous characteristics of MMPs, including particle size, color, shape, and type, the findings found the absence of a significant correlation between HistMF and the abundance and mass of PE. In summary, mulch-derived MMPs are not the primary source of MMPs in the mulching cultivated soil in terms of abundance but probably be in terms of mass.

Phytostabilization of sulfidic PbZn tailing landscapes may be one of interim options of tailings management, but which is limited by acute phytotoxicity of heavy metals in the tailings. The present study aimed to investigate the effectiveness of soluble phosphate (i.e., K2HPO4) in immobilizing soluble Pb, Cd and Zn and lowering their acute phytotoxicity. The addition of soluble phosphate improved the growth of native plants Acacia chisholmii and survival rate of A. ligulata, where the latter exhibited 100% survival rate. This was in contrast to effects of conventional organic amendment in the tailings on metal solubility (e.g., elevated metal levels in porewater) and plant survival (e.g., only 42%). Organic amendment with mulch did not lower the levels of water-soluble Cd, Pb and Zn and their concentrations in plant tissues after 56 days of plant growth in the treatment. In contrast, the tailings amended with K2HPO4 significantly decreased metal concentrations in the porewater and plant tissues by about 80–92% and 56–88%, respectively. The metal immobilization by phosphate was due to the formation of insoluble or sparingly soluble metal (Pb, Cd and Zn)-phosphate minerals in the tailings with circumneutral pH conditions, as revealed by using X-ray diffraction and scanning electron microanalyses. The reduced metal concentrations in roots and shoots of Acacia species after direct root contact with the K2HPO4 amended tailings suggested that metals (i.e., Pb, Cd and Zn) were effectively immobilized by the phosphate treatment of the tailings. These findings indicate that addition of high dosage of soluble phosphate may provide a low cost option to treat sulfidic PbZn tailings for rapid phytostabilization of the tailings surface, as an interim option to manage environmental risks of sulfidic PbZn tailings.

Mulch film (MF) residues is an important source of microplastics (MPs) in farmland, but its transportation risk to the wider environment was still unknown. Some researches have pursued the sources of MPs found in exorheic rivers. Even so, a systematic study depicting the occurrence, source and fate of microplastics derived from mulch films (MPMF), the crucial component of MPs in farmlands, in exorheic rivers still lacking. Here, the combination of UV–Vis Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) was used to identify the full-size MPMF (1–5000 μm) in field sediment samples collected by single-diagonal systematic sampling. This study verified that MPMF, a polyethylene-matrix composite doped with additives, contributed a considerable part of MPs detected in upstream farmland soil and riverine sediments, and even had an abundance of 38 ± 11 items/kg to 82 ± 15 items/kg, accounting for 9.0%–13.7% of the total MPs in estuary sediments. Notably, upstream farmland was identified to the main source of the riverine MPMF by partial least square path modeling (PLS-PM), contributing to 94.7% of MPMF in riverside sediments and 85.0% of MPMF in estuary sediments. Our study first demonstrates that MPMF constitutes a non-negligible component of MPs in estuarine sediments and underlines the urgency of strengthening the management of MPs pollution in drainage areas with a high agricultural intensity.

Agricultural mulch film (AMF) is deemed an important source of microplastics (MPs) in agricultural soil (AS). However, quantitating the contribution of AMFs to MPs in farmland soil and surface water remains a considerable challenge to date. In the present study, a basic framework was developed to address these concerns. First, the concentrations of MPs in soil derived from AMF abrasion (CMP) and the total MPs from all sources in AS (CTMP) were measured. Then, the ratios of CMP to CTMP, i.e., the contribution of AMFs to MPs in AS, were calculated. The contribution of AMFs to MPs in surface water via soil erosion was calculated based on CTMP values, the ratios of CMP to CTMP, soil erosion intensities (SEIs), and farmland areas. Furthermore, the potential contribution of soil erosion to MPs in the ocean was estimated. In China, the inventory of MPs in surface AS in 2018 ranged from 4.9 × 10⁶ to 1.0 × 10⁷ tons according to our results. AMFs contributed 10%–30% of the CTMP with certainties of 60–95%. Assuming that all MPs in AS can be exhaustively transferred to surface water via soil erosion, the national mass transfer amount of MPs (MTTMP) from AS to surface water reached 1.2 × 10⁵−2.2 × 10⁵ tons (∼2% of the inventory of MPs in the AS of China); the fluxes of MPs into the ocean from AS were 3.4 × 10⁴−6.6 × 10⁴ tons, assuming that all MPs in the AS of coastal provinces enter the ocean. It is likely that AMFs contributed 10%–30% MTTMP and fluxes of MPs to the ocean according to the ratios of CMP to CTMP. Apparently, approximately 30% of the national MTTMP (i.e., the rate of MP flux to the ocean to MTTMP) was input to the ocean.

Lab scale mulch biofilm barriers were constructed and tested to evaluate their performance for preventing the migration of aqueous and surfactant solubilized PAHs. The spatial distribution of viable PAH degrader populations and resultant biofilm formation were also monitored to evaluate the performance of the biobarrier and the prolonged surfactant effect on the PAH degrading microorganism consortia in the biobarrier. Sorption and biodegradation of PAHs resulted in stable operation of the system for dissolved phenanthrene and pyrene during 150 days of experimentation. The nonionic surfactant could increase the solubility of phenanthrene and pyrene significantly. However, the biobarrier itself couldn't totally prevent the migration of micellar solubilized phenanthrene and pyrene. The presence of surfactant and the resultant highly increased phenanthrene or pyrene concentration didn't appear to cause toxic effects on the attached biofilm in the biobarrier. However, the presence of surfactant did change the structural composition of the biofilm. Mulch biofilm barrier showed potential for surfactant enhanced bioremediation, and the presence of surfactant changed the structural composition of the biofilm.

Plastic residues have become a serious environmental problem in areas where agricultural plastic film are used intensively. Although numerous of studies have been done to assess its impacts on soil quality and crop yields, the understanding of meso-plastic particles effects on plant is still limited. In this study, low density polyethylene (PE) and biodegradable plastic (Bio) mulch film were selected to study the effects of meso-plastic debris on soybean germination and plant growth with the accumulation levels of 0%, 0.1%, 0.5% and 1% in soil (w: w, size ranging 0.5–2 cm) by a pot experiment under field condition. Results showed that the germination viability of soybean seeds was reduced to 82.39%, 39.44% and 26.06% in the treatments with 0.1%, 0.5% and 1% added plastic debris compared to the control (CK), respectively, suggesting that plastic residues in soil inhibit the viability of soybean seed germination. The plastic debris had a significant negative effect on plant height and culm diameter during the entire growth stage of soybean. Similarly, the leaf area at harvest was reduced by 1.97%, 6.86% and 11.53% compared to the CK in the treatments with 0.1%, 0.5% and 1% plastic debris addition, respectively. In addition, the total plant biomass under plastic addition was reduced in both the flowering and harvesting stages, compared to the CK. For the different type of plastic residues, plant height, leaf area and root/shoot ratio at group PE were significantly lower than those of groups treated by Bio. In conclusion, PE debris had a greater negative effects on plant height, culm diameter, leaf area and root/shoot ratio while Bio debris mainly showed the adverse effects on germination viability and root biomass especially at the flowering stage. Therefore, further research is required to elaborate plastic particles’ effects on different stages of crops and soil quality.

Application of greenwaste compost to brownfield land is increasingly common in soil and landscape restoration. Previous studies have demonstrated both beneficial and detrimental effects of this material on trace element mobility. A pot experiment with homogenised soil/compost investigated distribution and mobility of trace elements, two years after application of greenwaste compost mulch to shallow soils overlying a former alkali-works contaminated with Pb, Cu and As (∼900, 200 and 500 mg kg−1, respectively). Compost mulch increased organic carbon and Fe in soil pore water, which in turn increased As and Sb mobilization; this enhanced uptake by lettuce and sunflower. A very small proportion of the total soil trace element pool was in readily-exchangeable form (<0.01% As, <0.001% other trace elements), but the effect of compost on behaviour of metals was variable and ambiguous. It is concluded that greenwaste compost should be applied with caution to multi-element contaminated soils.

The rapid growth in solar PV construction means a concurrent growth in used solar panels and end of life packaging materials. The current study assesses the risks in an integrated manner, from applying shredded end of life packaging materials (EOLPM) to soil at a utility-scale solar energy (USSE) plant. Its aim and purpose is to determine if the EOLPM would pose a potential risk to human health and/or the environment if placed as a soil amendment incorporated into the surface soil (as a surface-incorporated mulch). An integrated risk assessment, drawing upon existing chemical and phytotoxicity data and introducing carbon emissions impacts (including social cost of carbon emissions) from treatment options, was undertaken confirming effective controls and risk treatments from on-site application as a soil amendment (soil improver). Landfilling (30 t CO₂e per MW) was estimated to cost $AUD6.8k per MW, compared to the most appropriate and selected on-site option of mulching (0.5 t CO₂ per MW and $UAD7.1k per MW). There is broad application of this approach to other remote USSE construction projects where solar PV construction growth is occurring exponentially globally.

The objectives of this study were investigating the photodegradation of the polycyclic aromatic hydrocarbons (PAHs) in modified petroleum impregnated bentonite mulch through solar radiation, determining PAHs’ translocation in the soils that underlay the mulch and finding a solution to prevent the uncontrolled release of petroleum into the environment. For this research, various formulated mulches were prepared: mulch no. 1 was a mixture of 5:1 sandy soil: natural bentonite + petroleum; mulch no. 2 composed a mixture of 5:1 sandy soil: modified bentonite + natural bentonite + petroleum; and mulch no. 3 composed a mixture of 5:1:0.5 ratio of sandy soil: natural bentonite: modified bentonite mixed with petroleum at a ratio of 1:1. PAHs in surface mulches and subsurface sandy soil were monitored over 5, 20, 40 and 80 days. The results demonstrated that PAHs undergo numerous changes over time because of sunlight. Photodegradation is the most dominant process for low molecular weight (LMW) PAHs (≤ 3 fused aromatic rings) and high molecular weight (HMW) PAHs (≥ 4 fused aromatic rings). HMW PAHs could be sequestrated strongly within the soil particles because of their higher aromaticity and lower polarity; they were more resilient in the soil matrices than LMW PAHs. Mulch no. 2 retained more PAHs compounds (p > 95%) than mulch nos. 1 and 3, which could be attributed to the retention of numerous PAHs in its interlayers, preventing its movement into the underlying soil, environment and atmosphere.

End-of-life packaging materials (EOLPM) present an important challenge from an environmental and financial perspective at utility-scale solar energy (USSE) sites. Reuse on-site represents, in particular for remote sites, a significant contribution to sustainable business practice as it provides a higher value end use when used to develop on-site mulch to enable soil improvement, reducing transport emissions (from the least preferred option of off-site disposal to landfill), reducing costs, and employing local contractors. The objective of the study was to enable on-site reuse, which was primarily achieved through chemical and physicochemical characterization of EOLPM streams; cardboard, and wood. Given the common occurrence of these materials in the rapidly growing renewable energy sector, it represents an important scope of work for the sector internationally. The methods used for characterization of the EOLPM, the first of its type reported, included a range of organic and inorganic chemical analyses, phytotoxicity testing, followed by an environmental and high-level (or initial) financial benefit cost analysis. Key scientific findings were that only trace concentrations of chemicals of potential concern (COPC) were detected; the material was not phytotoxic and has potential for soil improvement at the site, and the selected option of on-site reuse (of the materials as a mulch) had a global warming potential of 50 times less than the business as usual option (transport to landfill). The results also demonstrated the broader potential for using EOLPMs from USSE sites for soil improvement at remote locations rather than transporting offsite for disposal or reuse. Structural changes will need to be made to the way in which markets operate to achieve circular economy outcomes for these EOLPMs.