Publications

Occurrence and Characteristics of Microplastics in Soils of Greenhouse and Open-Field Cultivation Using Plastic Mulch Film

There is a major knowledge gap concerning the extent of microplastic pollution in agronomic regions of China, which represent a plastic use hotspot. This study investigated the characteristics of microplastics distributed in agricultural soils of three typical regions (Beijing (BJ), Shandong (SD), and Xinjiang (XJ)) with two plastic film mulching modes (greenhouse (G) and conventional field-based film mulching (M)) in China. The average abundance of microplastic under G and M mode was 3.60×104 particles kg-1 and 3.01×104 particles kg-1, respectively; and the estimated weight of microplastics per kg of dry soils in BJ, SD, and XJ was 3.12 mg kg-1, 5.63 mg kg-1, and 7.99 mg kg-1, respectively. Microplastics in farmland were mainly of a small particle size (50 to 250 μm), with their abundance decreasing with increasing particle size. Among the microplastics detected, polyethylene and polypropylene were the two dominant types present, accounting for 50.0% and 19.7%, respectively. In addition, plastic film mulching mode (G vs. M) had a stronger effect on microplastic distribution than agronomic region. This research provides key data to support the development of guidelines for the sustainable use of agricultural plastic film and an assessment of the environmental risk of microplastics.

Priming of the decomposition of ageing soil organic matter: concentration dependence and microbial control

Summary The amount of carbon (C) stored in soil is an important regulator for the global climate and soil fertility and is the balance between formation and decomposition of soil organic matter ( SOM ). Decomposition of SOM can be powerfully affected by labile carbon (C) supplements in, for example, the rhizosphere. A stimulation of SOM mineralisation induced by labile C additions is termed ‘priming’, and the mechanisms for this phenomenon remain elusive. The most widely held explanation assigns priming to successional dynamics in r ‐ and K ‐selected groups within the microbial community; groups which have also been connected with fungal ( K ‐selected) and bacterial ( r ‐selected) decomposers. New evidence has also suggested that recently formed SOM is particularly sensitive to priming. We investigated (i) the labile C concentration dependence of SOM mineralisation, (ii) the susceptibility of differently aged SOM to priming and (iii) if priming is due to bacterial or fungal growth dynamics. To create an age gradient of traceable SOM , we spiked a pasture soil using 14 C glucose, and subsampled plots 1 day, 2 months, 5 months and 13 months after application (i.e. SOM aged 1 day – 13 months). Glucose (0–4000 μg C g −1 ) was added in subsequent laboratory experiments, and respiration, SOM mineralisation ( 14 CO 2 evolution), bacterial growth rates (leucine incorporation) and fungal biomass (ergosterol) were tracked during ca. 1 week. Mineralisation of SOM aged 2–13 months showed similar labile C concentration dependencies, and priming increased mineralisation of SOM systematically by up to 350%. The glucose treatments induced variable microbial growth responses for differently aged SOM , which were unrelated to the priming effect. That successional dynamics in microbial r ‐ and K ‐selected groups, or bacterial and fungal decomposers, respectively, underpinned priming was incompatible with the results obtained. An alternative explanation could be that SOM transformation by extracellular enzymes, for subsequent respiration, could be triggered by labile C. In conclusion, labile C primed the mineralisation of 2–13 months aged SOM , and the mechanism for this priming was unrelated to microbial growth dynamics.

Long-Term Plastic Film Mulching Promotes Microplastic Accumulation and Alters Gross Nitrogen Transformation in Soil

No abstract is provided for this article.

Cross-continental comparative experiences of wastewater surveillance and a vision for the 21st century

The COVID-19 pandemic has brought the epidemiological value of monitoring wastewater into sharp focus. The challenges of implementing and optimising wastewater monitoring vary significantly from one region to another, often due to the array of different wastewater systems around the globe, as well as the availability of resources to undertake the required analyses (e.g. laboratory infrastructure and expertise). Here we reflect on the local and shared challenges of implementing a SARS-CoV-2 monitoring programme in two geographically and socio-economically distinct regions, São Paulo state (Brazil) and Wales (UK), focusing on design, laboratory methods and data analysis, and identifying potential guiding principles for wastewater surveillance fit for the 21st century. Our results highlight the historical nature of region-specific challenges to the implementation of wastewater surveillance, including previous experience of using wastewater surveillance, stakeholders involved, and nature of wastewater infrastructure. Building on those challenges, we then highlight what an ideal programme would look like if restrictions such as resource were not a constraint. Finally, we demonstrate the value of bringing multidisciplinary skills and international networks together for effective wastewater surveillance.

European Language Grid: An Overview

With 24 official EU and many additional languages, multilingualism in Europe and an inclusive Digital Single Market can only be enabled through Language Technologies (LTs). European LT business is dominated by hundreds of SMEs and a few large players. Many are world-class, with technologies that outperform the global players. However, European LT business is also fragmented, by nation states, languages, verticals and sectors, significantly holding back its impact. The European Language Grid (ELG) project addresses this fragmentation by establishing the ELG as the primary platform for LT in Europe. The ELG is a scalable cloud platform, providing, in an easy-to-integrate way, access to hundreds of commercial and non-commercial LTs for all European languages, including running tools and services as well as data sets and resources. Once fully operational, it will enable the commercial and non-commercial European LT community to deposit and upload their technologies and data sets into the ELG, to deploy them through the grid, and to connect with other resources. The ELG will boost the Multilingual Digital Single Market towards a thriving European LT community, creating new jobs and opportunities. Furthermore, the ELG project organises two open calls for up to 20 pilot projects. It also sets up 32 National Competence Centres (NCCs) and the European LT Council (LTC) for outreach and coordination purposes.

Photocatalysis in agricultural soils: Mineralogy and soil properties control the fixation and emission of NOx and other trace gases of N

Trace gases of nitrogen (N), such as NOx (nitric oxide, NO + nitrogen dioxide, NO2) have a negative impact on human health and the environment. Although NOx are naturally produced in volcanic eruptions, forest fires and biotic nitrification and denitrification in soils, human activity is a major source of these contaminants via e.g. the combustion of fossil fuels. Additionally, N fertilization in agricultural soils is also an important source of NOx emissions. These emissions involve a loss of soil N to the atmosphere and have a negative impact in air quality. The abiotic part of the N cycle in terrestrial ecosystems has not received as much attention as the biotic part and certain abiotic reactions could play a key role in regulating NOx emissions. Photocatalysis is an example as this is used to abate NOx gases in urban and industrial areas. This reaction requires the presence of a catalyst (e.g. titanium oxide), oxygen, water, and energy from the sun (UV-visible light) to transform NO from the atmosphere into innocuous inorganic N forms (mainly nitrate, NO3-). There is a continuous investment in the production of catalysts by the industry. However, a variety of soil minerals such as anatase or rutile (titanium oxides), hematite and goethite (iron oxides), are found in soils and they could act as catalysts; however, the occurrence of photocatalysis in soils has not been evaluated so far. In this study, we assess (i) the potential of a selection of soils with different mineralogy and a wide variety of soil properties to fix or emit NOx through photocatalysis, and (ii) the possible alterations in the fixation or emission of other N gases from the soil, i.e., nitrous oxide (N2O) and ammonia (NH3), when photocatalysis is induced. Around thirty agricultural soils were selected to meet the first objective and irradiated for 1 hour with UV-visible light under a constant flux of air and NO (100 ppm). Similar experiments were carried out with a selection of soils, whose potential to fix NO was different and tested in the previous experiment, to satisfy the second objective. However, only air (without NO) was pumped within the soil chamber in this case and the soils were previously fertilized with different N fertilisers (urea or KNO3-) and rates (0 to 250 mg N kg-1 soil). Our experiments show that weathered soils (with a high content in titanium and iron oxides) were able to fix more atmospheric NO through photocatalysis (objective i), and that NO and NH3 fixation and emissions after N fertilization depended not only on the N fertilizer and rate but also on soil properties, mainly soil pH and N content (objective ii). Soil mineralogy and properties play a key role in soil photocatalysis, and this abiotic reaction should be considered in order to design more sustainable strategies for agriculture.

Development of Microbial Diversity and Functional Potential in Bauxite Residue Sand under Rehabilitation

Sustainable plant establishment on ore processing residues requires development of a functional soil, which includes the introduction of organic matter and reestablishment of active microbial communities. This study investigated the development of microbial diversity and function in residue sand generated from alumina refining of mined bauxite ore. The residue sand embankments underwent rehabilitation with native vegetation over time, allowing study of a 3‐year chronosequence using space‐for‐time substitution. A coastal dune ecosystem was used as a natural alkaline sand analog with which to compare residue properties. Microbial biomass carbon in the residue sands were typically well below that of the coastal sand analog (< 50 mg kg −1 in residue sand compared to circa 450 mg kg −1 in coastal sand). Although the size of the microbial biomass appeared to be limited by the low organic matter content of the residue sand, a decline in microbial metabolic quotient indicated a potential alleviation of microbial stress with rehabilitation age. Despite the low microbial biomass, the ability of the residue sand microbial community to function with respect to the metabolism of added amino acids developed rapidly. Contrary to our original hypothesis, the diversity of the bacterial and fungal community also developed rapidly, and was similar to, or higher than, the coastal sand analog in 0.5‐year‐old rehabilitation. However, the bacterial, and in particular the fungal, community structure within residue sands were significantly different to that of the coastal sand analog with shifts in community structure driven, in part, by changing physicochemical conditions.

Wind and sand

A diversity of diversities: do complex environmental effects underpin associations between below- and aboveground taxa?

To predict how biodiversity will respond to global change, it is crucial to understand the relative roles of abiotic drivers and biotic interactions in driving associations between the biodiversity of disparate taxa. It is particularly challenging to understand diversity-diversity links across domains and habitats, because data are rarely available for multiple above- and below-ground taxa across multiple sites. Here we analyse data from a unique biodiversity dataset gathered across a variety of oceanic temperate terrestrial habitats in Wales, comprising 300 sites with co-located soil microbial, plant, bird, and pollinator surveys along with climate and soil physicochemical information. Soil groups are analysed using metabarcoding of the 16S, ITS1 and 18S DNA regions, allowing in depth characterisation of microbial and soil animal biodiversity. We explore biodiversity relationships along three aspects of community composition: First, we assess correlation between the alpha diversity of different groups. Second, we assess whether biotic turnover between sites is correlated across different groups. Finally, we investigate the co-occurrence of individual taxa across sites. In each analysis, we assess the contribution of linear or non-linear environmental effects. We find that a positive correlation between alpha diversity of plants, soil bacteria, soil fungi, soil heterotrophic protists, bees and butterflies is in fact driven by complex non-linear responses to abiotic drivers. In contrast, environmental variation did not account for positive associations between the diversity of plants and both birds and AM fungi, suggesting a role for biotic interactions. Both the diversity and taxon-level associations between the differing soil groups remained even after accounting for non-linear environmental gradients. Aboveground, spatial factors played larger roles in driving biotic communities, while linear environmental gradients were sufficient to explain many group- and taxon-level relationships. Synthesis. Our results show how non-linear responses to environmental gradients drive many of the relationships between plant biodiversity and the biodiversity of above- and belowground biological communities. Our work shows how different aspects of biodiversity might respond non-linearly to changing environments and identifies cases where management-induced changes in one community could either influence other taxa or lead to loss of apparent biological associations.

Resilience of soil microbial activity and of amino acid dynamics to the removal of plant carbon inputs during winter

Many temperate agricultural soils have prolonged periods in the winter when plant carbon inputs to the soil are low. Soil maintained at low temperature in the absence of plants was used to simulate the conditions in a vineyard soil during winter. In a four month simulated overwintering period we showed that the concentration of dissolved organic carbon and nitrogen in soil solution slowly declined alongside heterotrophic soil respiration. Measurements of free amino acid concentrations and turnover indicated that the amino acid pool in soil was rapidly depleted but readily replenished throughout the four-month period. This indicates that the soil contained intrinsic reserves of labile C that was capable of supporting the soil microbial community in times of reduced plant C inputs.

Epizoic barnacles act as a reservoir for pathogenic bacteria on commercial shellfish beds: implications for the shellfish industry.

Routine monitoring of commercial shellfish beds in the European Union currently focuses on quantifying the bacterial content within shellfish flesh as an indicator of faecal contamination. Previous studies have documented the presence of other significant bacterial reservoirs within commercial shellfish beds e.g. sediments. This study examined the importance of epizoic barnacles as a potential bacterial reservoir across three intertidal mussel (Mytilus edulis) beds in North Wales, UK. Results demonstrated that over 80% of the total coliform reservoir was held within the epizoic barnacles in comparison to the mussel flesh, concluding that epizoic barnacles represent a significant bacterial reservoir within commercial shellfisheries. The implications for the shellfish industry are discussed.

pH and exchangeable aluminum are major regulators of microbial energy flow and carbon use efficiency in soil microbial communities

The microbial partitioning of organic carbon (C) into either anabolic (i.e. growth) or catabolic (i.e. respiration) metabolic pathways represents a key process regulating the amount of added C that is retained in soil. The factors regulating C use efficiency (CUE) in agricultural soils, however, remain poorly understood. The aim of this study was to investigate substrate CUE from a wide range of soils (n = 970) and geographical area (200,000 km2) to determine which soil properties most influenced C retention within the microbial community. Using a 14C-labeling approach, we showed that the average CUE across all soils was 0.65 ± 0.003, but that the variation in CUE was relatively high within the sample population (CV 14.9%). Of the major properties measured in our soils, we found that pH and exchangeable aluminum (Al) were highly correlated with CUE. We identified a critical pH transition point at which CUE declined (pH 5.5). This coincided exactly with the point at which Al3+ started to become soluble. In contrast, other soil factors [e.g. total C and nitrogen (N), dissolved organic C (DOC), clay content, available calcium, phosphorus (P) and sulfur (S), total base cations] showed little or no relationship with CUE. We also found no evidence to suggest that nutrient stoichiometry (C:N, C:P and C:S ratios) influenced CUE in these soils. Based on current evidence, we postulate that the decline in microbial CUE at low pH and high Al reflects a greater channeling of C into energy intensive metabolic pathways involved in overcoming H+/Al3+ stress (e.g. cell repair and detoxification). The response may also be associated with shifts in microbial community structure, which are known to be tightly associated with soil pH. We conclude that maintaining agricultural soils above pH 5.5 maximizes microbial energy efficiency.

Model and field studies of the degradation of cross-linked polyacrylamide gels used during the revegetation of slate waste

Cross-linked polyacrylamide gels are increasingly being used in environmental restoration schemes and horticulture as a means of enhancing water supply to plants. However, the environmental impact of cross-linked polyacrylamide gel deployment in soil remains poorly understood. This study assessed the chemical, physical and biological properties of new and field-conditioned cross-linked polyacrylamide gels. Both monomeric acrylamide (11 μg l−1) and acrylic acid (285 μg l−1) were observed in new gel; however, the levels of monomers in field-conditioned gels (1–6 years old) were very low (acrylamide <1 μg l−1; acrylic acid <7 μg l−1). Generally, freeze–thaw processes and exposure to UV radiation had little effect on gel acrylic acid and acrylamide concentrations. However, elevated temperatures (35 °C) caused a significant release of up to 144 μg l−1 of acrylamide and 453 μg l−1 of acrylic acid in new gel and up to 25 μg l−1 of acrylamide and 157 μg l−1 of acrylic acid in field-conditioned gels. In contrast, gel water holding capacity was highly dependent upon environmental conditions (UV exposure and freeze/thaw cycles produced the greatest loss of water holding in new gels) and gel age. Optical microscopy revealed that after placement in the field the gels became increasingly colonised over time by fungi and bacteria. In enrichment cultures, we were unable, however, to demonstrate microbial growth when cross-linked polyacrylamide was used as the sole nitrogen source. In summary, under a range of conditions cross-linked polyacrylamide did not release acrylamide above legally permitted limits, with the exception of gel subjected to elevated temperatures. However, their capacity for holding water decreased sharply within 18 months. We therefore conclude that cross-linked polyacrylamide placed in soil is relatively stable with respect to the production of potentially toxic acrylamide, a species with a short half-life, which degrades to the much less toxic acrylic acid. However, the loss of water holding capacity raises questions about its long-term effectiveness in land restoration schemes as this is the main reason it is used in this role.

Mineralization and Transfer of Polymer-Derived Carbon from Biodegradable Mulch into the Soil Microbial Biomass and Organic Matter Pool

The use of biodegradable mulch (BDM) instead of a conventional plastic mulch film has the potential to reduce the accumulation of legacy plastic in agroecosystems. The fate of BDM polymer carbon (C) in soil, however, remains poorly understood, especially the fraction of polymer-C that enters microbial catabolic (mineralization) versus anabolic (immobilization) pathways. We present a novel approach that allows tracking of polymer-C into CO₂, macro- and microplastic residues, living microbial biomass, and soil organic matter (SOM) through the combination of CO₂ emission, ¹³C- and ¹⁴C-phospholipid fatty acid (PLFA) analysis, and plastic polymer analysis. After exposing a clear BDM piece (2 cm × 2 cm) in an agricultural soil for up to 1 year, we found that 22 ± 9% (mean and standard deviation) of the polymer-C remained as macroplastic residues (>1 mm), 19 ± 3% was present in microplastic particles (<1 mm), 22 ± 1% was emitted as CO₂, 0.9 ± 0.1% was present in living microbial biomass, and 37 ± 9% was present in microbial necromass or SOM. Similar values were observed for black BDM (21 ± 3%, 10 ± 2%, 21 ± 4%, 0.8 ± 0.0%, and 47 ± 6%, respectively). Our findings indicate that, within 1 year of soil incubation, a fraction of the macroscopic BDM pieces fragmented into microplastics, while a fraction of polymer-C was mineralized and emitted as CO₂, and another substantial fraction transferred into SOM. Our research advances knowledge on reducing reliance on polyethylene-based plastics and offers practical implications for improving agroecosystem sustainability.

Integration of biochar with animal manure and nitrogen for improving maize yields and soil properties in calcareous semi-arid agroecosystems

Declining soil quality is commonplace throughout Southern Asia and sustainable strategies are required to reverse this trend to ensure food security for future generations. One potential solution to halt this decline is the implementation of integrated nutrient management whereby inorganic fertilisers are added together with organic wastes. These organic materials, however, are often quickly broken down in soil and provide only a transitory improvement in soil quality. Biochar, which can potentially persist in soil for centuries, may offer a more permanent solution to this problem. To address this, we undertook a 2-year field trial to investigate the interactions between conventional NPK fertilisers, farmyard manure (FYM) and biochar in a maize cropping system. Biochar application to the nutrient poor soil increased maize yields after year one by approximately 20% although the yield increase was lower in the second year (ca. 12.5%). Overall, there was little difference in grain yield between the 25tha−1 and the 50tha−1 biochar treatments. In terms of soil quality, biochar addition increased levels of soil organic carbon, inorganic N, P and base cations and had no detrimental impact on pH and salinity in this calcareous soil. Overall, this field trial demonstrated the potential of biochar to induce short-term benefits in crop yield and soil quality in maize cropping systems although the long-term benefits remain to be quantified. From a management perspective, we also highlight potential conflicts in biochar availability and use, which may limit its adoption by small scale farming systems typical of Southern Asia.

Meta-analysis of the accumulation and stabilisation of particulate and mineral-associated organic carbon by fertilization

Fertilization is a crucial factor influencing soil organic carbon (SOC) accumulation. While the effects of fertilization strategies on SOC sequestration have frequently been investigated, their impacts on mineral-associated organic carbon (MAOC) and particulate organic carbon (POC) accumulation and their global distribution patterns remain unclear. We conducted a meta-analysis of 870 observations to assess the effects of fertilization on soil C fractions and their stability and identify the main drivers. Fertilization increased MAOC and POC contents by 18 % and 68 %, respectively, while reducing the ratio of MAOC to SOC by 10 %. Co-application of mineral and organic fertilisers led to the most significant increases in MAOC (30 %) and POC (125 %) contents. Significant increases in SOC pools occurred in arid regions with low soil C/N ratio, low clay content, high soil pH (≥7.3), and fertilization duration exceeding 10 years. The increase in alkyl C, carbonyl C, and carboxyl C and a decrease in O-alkyl C in soil organic matter under fertilization indicate a shift toward more stable molecular structures, reflecting the increased SOC stability. SOC responses to fertilization were enhanced in mid-latitude to high-latitude regions compared to lower latitudes. In conclusion, under fertilization, SOC accumulation is primarily driven by POC increases and greater molecular structural stability of SOC; this offers crucial insights for understanding soil carbon sequestration under agricultural management. • Fertilization reduces the contribution of mineral-associated organic carbon to soil organic carbon by 10 %. • Soil organic carbon accumulation is primarily driven by increases in particulate organic carbon (68 %) under fertilization. • Fertilization shifts soil organic carbon fractions to more stable molecular structures (alkyl C, carbonyl C). • Soil organic carbon, including mineral-associated carbon, responds more to fertilization in mid- to high-latitude regions.

Decreased soil microbial biomass and nitrogen mineralisation with Eucalyptus biochar addition to a coarse textured soil

Biochar has been shown to aid soil fertility and crop production in some circumstances. We investigated effects of the addition of Jarrah (Eucalyptus margi

In silico toxicology protocols

The present publication surveys several applications of in silico (i.e., computational) toxicology approaches across different industries and institutions. It highlights the need to develop standardized protocols when conducting toxicity-related predictions. This contribution articulates the information needed for protocols to support in silico predictions for major toxicological endpoints of concern (e.g., genetic toxicity, carcinogenicity, acute toxicity, reproductive toxicity, developmental toxicity) across several industries and regulatory bodies. Such novel in silico toxicology (IST) protocols, when fully developed and implemented, will ensure in silico toxicological assessments are performed and evaluated in a consistent, reproducible, and well-documented manner across industries and regulatory bodies to support wider uptake and acceptance of the approaches. The development of IST protocols is an initiative developed through a collaboration among an international consortium to reflect the state-of-the-art in in silico toxicology for hazard identification and characterization. A general outline for describing the development of such protocols is included and it is based on in silico predictions and/or available experimental data for a defined series of relevant toxicological effects or mechanisms. The publication presents a novel approach for determining the reliability of in silico predictions alongside experimental data. In addition, we discuss how to determine the level of confidence in the assessment based on the relevance and reliability of the information.