Predawn leaf water potential of grapevines is not necessarily a good proxy for soil moisture.

BACKGROUND: In plant water relations research, predawn leaf water potential (Ψpd) is often used as a proxy for soil water potential (Ψsoil), without testing the underlying assumptions that nighttime transpiration is negligible and that enough time has passed for a hydrostatic equilibrium to be established. The goal of this research was to test the assumption Ψpd = Ψsoil for field-grown grapevines. RESULTS: A field trial was conducted with 30 different cultivars of wine grapes grown in a single vineyard in arid southeastern Washington, USA, for two years. The Ψpd and the volumetric soil water content (θv) under each sampled plant were measured multiple times during several dry-down cycles. The results show that in wet soil (Ψsoil > - 0.14 MPa or relative extractable water content, θe > 0.36), Ψpd was significantly lower than Ψsoil for all 30 cultivars. Under dry soil conditions (Ψsoil < - 0.14 MPa or θe < 0.36) Ψpd lined up better with Ψsoil. There were differences between cultivars, but these were not consistent over the years. CONCLUSION: These results suggest that for wet soils Ψpd of grapevines cannot be used as a proxy for Ψsoil, while the Ψpd = Ψsoil assumption may hold for dry soils.

Minimal Impacts of Microplastics on Soil Physical Properties under Environmentally Relevant Concentrations.

Agricultural soils are a major reservoir of microplastics, and concerns have arisen about the impacts of microplastics on soil properties and functioning. Here, we measured the physical properties of a silt loam in response to the incorporation of polyester fibers and polypropylene granules over a wide range of concentrations. We further elucidated the underlying mechanisms by determining the role of microplastic shape and the baseline effects from the amendment of soil particles. The incorporation of microplastics into soil tended to increase contact angle and saturated hydraulic conductivity and decrease bulk density and water holding capacity, but not affect aggregate stability. Polyester fibers affected soil physical properties more profoundly than polypropylene granules, due to the vastly different shape of fibers from that of soil particles. However, changes in soil properties were gradual, and significant changes did not occur until a high concentration of microplastics was reached (i.e., 0.5% w/w for polyester fibers and 2% w/w for polypropylene granules). Currently, microplastic concentrations in soils not heavily polluted with plastics are far below these concentrations, and results from this study suggest that microplastics at environmentally relevant concentrations have no significant effects on soil physical properties.

Enhanced Transport of TiO2 in Unsaturated Sand and Soil after Release from Biodegradable Plastic during Composting.

Biodegradable plastics can reach full degradation when disposed of appropriately and thus alleviate plastic pollution caused by conventional plastics. However, additives can be released into the environment during degradation and the fate of these additives can be affected by the degradation process. Here, we characterized TiO2 particles released from a biodegradable plastic mulch during composting and studied the transport of the mulch-released TiO2 particles in inert sand and agricultural soil columns under unsaturated flow conditions. TiO2 particles (238 nm major axis and 154 nm minor axis) were released from the biodegradable plastic mulch in both single-particle and cluster forms. The mulch-released TiO2 particles were fully retained in unsaturated soil columns due to attachment onto the solid-water interface and straining. However, in unsaturated sand columns, the mulch-released TiO2 particles were highly mobile. A comparison with the pristine TiO2 revealed that the mobility of the mulch-released TiO2 particles was enhanced by humic acid present in the compost residues, which blocked attachment sites and imposed steric repulsion. This study demonstrates that TiO2 particles can be released during composting of biodegradable plastics and the transport potential of the plastic-released TiO2 particles in the terrestrial environment can be enhanced by compost residues.

Collaborative optimization of depot location, capacity and rolling stock scheduling considering maintenance requirements.

Generally, when optimizing a rolling stock schedule, the locations of the depots, or places in the network where the composition changes and maintenance occurs, are assumed known. The locations where maintenance is performed naturally influence the quality of any resulting rolling stock schedules. In this paper, the problem of selecting new depot locations and their corresponding capacities is considered. A two-stage mixed integer programming approach for rolling stock scheduling with maintenance requirements is extended to account for depot selection. First, a conventional flow-based model is solved, ignoring maintenance requirements, to obtain a variety of rolling stock schedules with multiple depot locations and capacity options. Then, a maintenance feasible rolling stock schedule can be obtained by solving a series of assignment problems by using the schedules found in the first stage. The proposed methodology is tested on real-life instances, and the numerical experiments of different operational scenarios are discussed.

Aggregation kinetics and stability of biodegradable nanoplastics in aquatic environments: Effects of UV-weathering and proteins.

Plastic pollution caused by conventional plastics has promoted the development and use of biodegradable plastics. However, biodegradable plastics do not degrade readily in water; instead, they can generate micro- and nanoplastics. Compared to microplastics, nanoplastics are more likely to cause negative impacts to the aquatic environment due to their smaller size. The impacts of biodegradable nanoplastics highly depend on their aggregation behavior and colloidal stability, which still remain unknown. Here, we studied the aggregation kinetics of biodegradable nanoplastics made of polybutylene adipate co-terephthalate (PBAT) in NaCl and CaCl2 solutions as well as in natural waters before and after weathering. We further studied the effect of proteins on aggregation kinetics with both negative-charged bovine serum albumin (BSA) and positive-charged lysozyme (LSZ). For pristine PBAT nanoplastics (before weathering), Ca2＋ destabilized nanoplastic suspensions more aggressively than Na+, with the critical coagulation concentration being 20 mM in CaCl2 vs 325 mM in NaCl. Both BSA and LSZ promoted the aggregation of pristine PBAT nanoplastics, and LSZ showed a more pronounced effect. However, no aggregation was observed for weathered PBAT nanoplastics under most experimental conditions. Further stability tests demonstrated that pristine PBAT nanoplastics aggregated substantially in seawater, but not in freshwater, and only slightly in soil pore water; while weathered PBAT nanoplastics remained stable in all natural waters. These results suggest that biodegradable nanoplastics, especially weathered biodegradable nanoplastics, are highly stable in the aquatic environment, even in the marine environment.

Formation, behavior, properties and impact of micro- and nanoplastics on agricultural soil ecosystems (A Review).

Micro and nanoplastics (MPs and NPs, respectively) in agricultural soil ecosystems represent a pervasive global environmental concern, posing risks to soil biota, hence soil health and food security. This review provides a comprehensive and current summary of the literature on sources and properties of MNPs in agricultural ecosystems, methodology for the isolation and characterization of MNPs recovered from soil, MNP surrogate materials that mimic the size and properties of soil-borne MNPs, and transport of MNPs through the soil matrix. Furthermore, this review elucidates the impacts and risks of agricultural MNPs on crops and soil microorganisms and fauna. A significant source of MPs in soil is plasticulture, involving the use of mulch films and other plastic-based implements to provide several agronomic benefits for specialty crop production, while other sources of MPs include irrigation water and fertilizer. Long-term studies are needed to address current knowledge gaps of formation, soil surface and subsurface transport, and environmental impacts of MNPs, including for MNPs derived from biodegradable mulch films, which, although ultimately undergoing complete mineralization, will reside in soil for several months. Because of the complexity and variability of agricultural soil ecosystems and the difficulty in recovering MNPs from soil, a deeper understanding is needed for the fundamental relationships between MPs, NPs, soil biota and microbiota, including ecotoxicological effects of MNPs on earthworms, soil-dwelling invertebrates, and beneficial soil microorganisms, and soil geochemical attributes. In addition, the geometry, size distribution, fundamental and chemical properties, and concentration of MNPs contained in soils are required to develop surrogate MNP reference materials that can be used across laboratories for conducting fundamental laboratory studies.

In-field degradation of soil-biodegradable plastic mulch films in a Mediterranean climate.

Soil-biodegradable plastic mulch films are a promising alternative to polyethylene mulches, but adoption has been slow, in part because of uncertainties about in-field degradation. The international biodegradability standard EN-17033 requires 90% degradation within 2 years in an aerobic incubation at constant temperature (20-28 °C). However, in-laboratory biodegradability does not guarantee in-field degradation will follow the same timeframe. Field test protocols are needed to assess biodegradable mulches under a range of environmental conditions and collate site-specific information to predict degradation. Our objectives were to (1) monitor in-field degradation of soil-biodegradable plastic mulches following successive applications and incorporations, (2) quantify mulch recovery 2 years after the final incorporation, and (3) compare in-field degradation with the laboratory standard in terms of calendar and thermal times based on a zeroth-order kinetics model. A field experiment was established in spring 2015 in Mount Vernon, WA testing five biodegradable mulches laid each spring and incorporated each fall until 2018. Mulch recovery was quantified every 6 months until fall 2020, 2 years after the final incorporation. While mulches were incorporated annually, recovery of visible fragments (>2.36 mm) was constant or decreasing over time, indicating mulch deterioration kept pace with new additions. In fall 2020, mulch recovery was 4-16% of total mulch mass incorporated. A zeroth-order kinetics model was used to analyze mulch degradation after the final application. Model extrapolations indicate it would take 21 to 58 months to reach 10% recovery (90% degradation), exceeding the laboratory standard's 24-month benchmark by up to a factor of 2.4. However, when the analysis is done with thermal time, better agreement between in-field and laboratory degradation rates is observed. While other factors, including soil type, soil moisture, and mulch fragment size are also at play, thermal time, rather than calendar time, will be more applicable for assessing site-specific, in-field mulch degradation.

How to take representative samples to quantify microplastic particles in soil?

The amount of plastic particles in terrestrial ecosystems is not well known, not only because it is difficult to extract and identify plastic particles from terrestrial samples, but also because it is challenging to take representative samples from soils or sediments. Here, we numerically simulated how to take representative terrestrial samples to quantify plastic particles, and we evaluated the accuracy (error) of reported plastic concentrations in the literature. Fields with randomly distributed plastic particles (uniform and clustered) were numerically generated and sampled to determine the representative elementary volume (REV) and the required number of samples to quantify plastic concentrations (10 to 106 particles/m2) with different relative errors (5%, 10%, 15%). The REV and the required number of samples decrease hyperbolically as the plastic concentration increases, indicating a strong non-linear relation. For instance, hundreds to thousands of soil cores (8-cm diameter) would be required to quantify plastics at low concentrations (102 particles/m2), while a few cores are sufficient at high plastic concentrations (105 particles/m2). For an accurate measurement of plastic concentrations, the total surface area of samples taken should approach or exceed the REV. We recommend to take replicated samples with each sample as large as possible (e.g., 1 m × 1 m) rather than multiple small cores, and then reduce the soil volume by the quartering method.

DJ-1 promotes development of DEN-induced hepatocellular carcinoma and proliferation of liver cancer cells.

Chronic liver inflammation and injuries play a critical role in development of hepatocellular carcinoma (HCC). Parkinson disease (autosomal recessive, early onset) 7, encoding PARK7 protein (also called DJ-1), plays important roles in many carcinogenesis processes and is essential in modulating inflammation. However, whether DJ-1 is involved in HCC development remains largely unknown. To determine the effect of DJ-1 on HCC development, we accessed the correlation of hepatic DJ-1 expression with overall survival (OS) and TNM stage in 96 HCC patients and found a significant inverse correlation between DJ-1 expression and OS. By adopting a classic diethylnitrosamine (DEN)-induced murine HCC model, DJ-1 knockout (KO) mice displayed reduced tumorigenesis and cell proliferation, accompanied by decreased hepatic inflammation and IL-6/STAT3 activation. Furthermore, after an acute DEN challenge, DJ-1 KO mice showed significant decreases in liver injury, hepatocyte proliferation and DNA damage. In a human HCC cell line (MHCC-97L), cancer cell proliferation was induced by overexpression of DJ-1 and is related to oncogenic signaling of MAPKs and AKT. Induction of DJ-1 may serve as a novel regulator for HCC cell proliferation and HCC development possibly through enhanced MAPK signaling and inflammation.

Deficiency of DJ-1 Ameliorates Liver Fibrosis through Inhibition of Hepatic ROS Production and Inflammation.

Liver fibrosis is a global health problem and previous studies have demonstrated that reactive oxygen species (ROS) play important roles in fibrogenesis. Parkinson disease (autosomal recessive, early onset) 7 (Park7) also called DJ-1 has an essential role in modulating cellular ROS levels. DJ-1 therefore may play functions in liver fibrogenesis and modulation of DJ-1 may be a promising therapeutic approach. Here, wild-type (WT) and DJ-1 knockout (DJ-1 KO) mice were administrated with carbon tetrachloride (CCl4) to induce liver fibrosis or acute liver injury. Results showed that DJ-1 depletion significantly blunted liver fibrosis, accompanied by marked reductions in liver injury and ROS production. In the acute CCl4 model, deficiency of DJ-1 showed hepatic protective functions as evidenced by decreased hepatic damage, reduced ROS levels, diminished hepatic inflammation and hepatocyte proliferation compared to WT mice. In vitro hepatic stellate cells (HSCs) activation assays indicated that DJ-1 has no direct effect on the activation of HSCs in the context of with or without TGFß treatment. Thus our present study demonstrates that in CCl4-induced liver fibrosis, DJ-1 deficiency attenuates mice fibrosis by inhibiting ROS production and liver injury, and further indirectly affecting the activation of HSCs. These results are in line with previous studies that ROS promote HSC activation and fibrosis development, and suggest the therapeutic value of DJ-1 in treatment of liver fibrosis.