Sewage sludge application as a vehicle for microplastics in eastern Spanish agricultural soils

Microplastic pollution is becoming a major challenge with the growing use of plastic. In recent years, research about microplastic pollution in the environment has become a field of study with increased interest, with ever expanding findings on sources, sinks and pathways of microplastics. Wastewater treatment plants effectively remove microplastics from wastewater and concentrate them in sewage sludge which is often used to fertilise agricultural fields. Despite this, quantification of microplastic pollution in agricultural fields through the application of sewage sludge is largely unknown. In light of this issue, four wastewater treatment plants and 16 agricultural fields (0–8 sewage sludge applications of 20–22 tons ha−1 per application), located in the east of Spain, were sampled. Microplastics were extracted using a floatation and filtration method, making a distinction between light density microplastics (ρ −3) and heavy density microplastics (ρ > 1 g cm−3). Sewage sludge, on average, had a light density plastic load of 18,000 ± 15,940 microplastics kg−1 and a heavy density plastic load of 32,070 ± 19,080 microplastics kg−1. Soils without addition of sewage sludge had an average light density plastic load of 930 ± 740 microplastics kg−1 and a heavy density plastic load of 1100 ± 570 microplastics kg−1. Soils with addition of sewage sludge had an average light density plastic load of 2130 ± 950 microplastics kg−1 and a heavy density plastic load of 3060 ± 1680 microplastics kg−1. On average, soils’ plastic loads increased by 280 light density microplastics kg−1 and 430 heavy density microplastics kg−1 with each successive application of sewage sludge, indicating that sewage sludge application results in accumulation of microplastics in agricultural soils. Microplastics concentrations in soils are highly proportional to the number of sludge applications.</p

Interactions between agricultural mulching plastic debris and pesticides

In semi-arid regions, the use of plastic mulch and pesticides in conventional agriculture is nearly ubiquitous. The use of plastics and pesticides lead both to the release of residues in the soils. The degradation of plastic and pesticide residues in the soil have been previously studied, but not together despite the fact that pesticides may be sorbed to plastics and that the sorption may change the degradation rate. In fact, the sorption of pesticides on Low Density Polyethylene (LDPE) has been previously studied, but no data is available for other plastics such as Pro-oxidant Additive Containing (PAC) plastics or "biodegradable" (Bio) plastics. The aim of this research was to measure the sorption pattern of active substances from 38 pesticides on LDPE, PAC and Bio plastic mulches and to compare the decay of the active substances in the presence and absence of plastic debris. For this purpose, 38 active substances from 17 insecticides, 15 fungicides and 6 herbicides commonly applied with plastic mulching in South-east Spain were incubated at 35°C for 15 days with a 3×3 cm² square of plastic mulch (LDPE, PAC and Bio). The QuEChERS (Quick Easy Cheap Effective Rugged Safe) approach was adapted to extract the pesticides. The sorption behaviour depended on both, the pesticide and the plastic mulch type. On average, the sorption percentage was ~23% on LDPE and PAC, and ~50% on Bio. The decay of active substances in the presence of plastic was, on average, 30% lower than the decay of active substances in solution alone. Therefore, efficacy, transport, degradability and/or eco-toxicity of active substances from pesticides may be affected by sorption on plastics. Additionally the sorption of pesticides on plastic debris may affect the plastic degradability due to the toxicity of pesticides to some soil organisms

Fragmentation and depolymerization of microplastics in the earthworm gut: a potential for microplastic bioremediation?

The accumulation of microplastics poses potential risks to soil health. Here, we did a preliminary exploration on the potential of Lumbricus terrestris (Oligochaeta) to reduce low-density polyethylene (LDPE), polylactic acid (PLA), and polybutylene adipate terephthalate (PBAT) microplastic (20–648 µm) contamination in soils. The ingestion of microplastics-contaminated soil (1% of microplastics, dw/dw) in a mesocosm system and the ingestion of pure microplastics in the Petri Dish by earthworms were studied. Results show that earthworms survived in the microplastics-contaminated soil (0% mortality in 35 days) but barely when exposed solely to microplastics (30–80% mortality in 4 days). Size-dependent ingestion of microplastics was not observed. The fragmentation of LDPE microplastics in the gizzard facilitated by soil was confirmed by the significantly increased ratio of small-sized (20–113 µm) microplastics from the bulk soil to the gut (from 8.4% to 18.8%). PLA and PBAT microplastics were fragmented by gizzard without the facilitation of soil, the ratios of small-sized (20–113 µm) PLA and PBAT microplastics in the gut were 55.5% and 108.2% higher than in respective pristine distributions. Substantial depolymerization of PLA (weight-average molar mass reduced by 17.7% with shift in molecular weight distribution) and suspected depolymerization of PBAT were observed in the worm gut, while no change in the molar mass was observed for PLA and PBAT microplastics buried in the soil for 49 days. Our results suggest that ingested microplastics could undergo fragmentation and depolymerization (for certain polymers) in the earthworm gut. Further research is needed to reveal the mechanisms of polymer depolymerization in the earthworm gut and to evaluate the feasibility of microplastic bioremediation with earthworms

Abundance and diversity of soil macroinvertebrates in sugarcane (Saccharum spp.) plantations under organic and chemical fertilization in Belize

Many studies suggest that sugarcane management practices have negative impact on soil quality, especially on soil organisms, however, information on macroinvertebrate abundance and diversity in conventional sugarcane fields is scarce. This study determined the abundance and diversity of soil macroinvertebrates in sugarcane plantations under 2 types of soils, Cambisol and Fluvisol, with three types of fertilizer management: chemical fertilizer, vinasse and filter mud, and in a secondary forest (on a Cambisol). Sampling was carried out in northern Belize during two crop cycles (from May 2013 to May 2015). Soil macroinvertebrates were collected using monoliths based on Tropical Soil Biology and Fertility (TSBF) Handbook of Methods at the end of the rainy seasons. The parameters evaluated were biomass, density and diversity of soil macroinvertebrates (number of morphospecies, an ecological index for tropical soil quality based on macrofauna, and a converted Shannon index (H_exp)), yield and plant response variables (number of stool, number of stem, number of active leaves, stem length and stem diameter). A total of 7,634 individuals were identified, grouped into 52 morphospecies belonging to 16 orders and three species of annelids. No significant differences existed among management systems (application of chemical fertilizer, vinasse, filter mud and secondary forest) on abundance and diversity of soil macroinvertebrates, yield and plant variables. However, there were significant differences between soils and cycles in some evaluated parameters. Presuming that soil type and seasonal conditions, in a two years trial, had higher weight on determine the studied parameters than the different management systems.Muchos estudios sugieren que las prácticas de manejo de la caña de azúcar tienen un impacto negativo en la calidad del suelo, especialmente en los organismos del suelo, sin embargo, la información sobre la abundancia y diversidad de macroinvertebrados en los campos de caña de azúcar convencionales es escasa. Este estudio determinó la abundancia y diversidad de macroinvertebrados del suelo en plantaciones de caña de azúcar en dos tipos de suelo, Cambisol y Fluvisol, tres tipos de manejo de fertilizantes: fertilizante químico, vinaza, cachaza, y en un bosque secundario (en un Cambisol). El muestreo fue llevado a cabo en el norte de Belice durante dos ciclos agrícolas (de mayo 2013 a mayo 2015). Los macroinvertebrados del suelo fueron colectados usando monolitos basados en el método del Manual de Métodos Tropical Soil Biology and Fertility (TSBF) al final de las temporadas de lluvia. Los parámetros evaluados fueron biomasa, densidad y diversidad de macroinvertebrados del suelo (número de morfoespecies, un índice ecológico para la calidad del suelo tropical y un índice de Shannon convertido (H_exp)), rendimiento y variables de las plantas (número de cepas, número de tallos, número de hojas activas, largo del tallo y diámetro del tallo). Un total de 7,634 individuos fueron identificados, agrupados en 52 morfoespecies pertenecientes a 16 Ordenes y tres especies de anélidos. No existió diferencias significativas entre los sistemas de manejo (aplicación de fertilizante químico, vinaza, cachaza y bosque secundario) en la abundancia y diversidad de macroinvertebrados, rendimiento y variables de las plantas. Sin embargo, hubo diferencias significativas entre suelos y ciclos en algunos de los parámetros. Suponiendo que el tipo de suelo y las condiciones estacionales, en un ensayo de dos años, tuvieron mayor peso para determinar los parámetros estudiados que los diferentes sistemas de manejo

Abundance and Diversity of Earthworms in Managed and Non- Managed Fallow Lands of Calakmul Reserve of Campeche, Mexico

In Mexico, the best preserved tropical rain forest is found in Calakmul Reserve, where fallow land management has been established. Fallow lands are developed as a consequence of a successional vegetation process after clearing the primary vegetation and milpa production. Forty-nine sites were studied, where 17 were managed fallow lands, 24 non-managed fallow lands, and 8 tropical rain forests. Earthworms were collected at the end of the raining season, and four monoliths of 25 × 25 × 30 cm were developed per site according to the TSBF method. We observed how Zapatadrilus siboney, a native species was dominant in managed and non-managed fallow lands. Earthworm’s total biomass and density were not significantly different between the managed and non-managed fallow lands. Earthworm’s species richness was significantly low in non-managed fallow lands. We observed a strong correlation between earthworm density and richness with the age of the fallow lands (r2: 0.9 and 0.7; p < 0.05, respectively). The management type of the fallow land seems to affect earthworm biomasses (r2: 0.56; p < 0.05)

Perceptions and Attitudes Regarding Organic Waste: Feasibility of Establishing an Urban Composting Program in Chiapas, Mexico

The poor management of household and municipal waste is a threat to the sustainability of urban communities throughout the world, and also constitutes a missed opportunity for community and economic development. Additionally, many innovations in household solid waste management are never adopted because they do not take into account existing local knowledge, preferences, behaviors, and management practices. In order to contribute to solving solid waste problems in small multicultural cities in Latin America, we conducted an interdisciplinary study that (1) documents current practices for managing organic waste; (2) identifies citizens' willingness to compost household refuse and farmers' willingness to use this compost; and (3) analyzes whether composting municipal results in compost of adequate quality. We also identify innovative urban practices for organic waste management. Compost obtained during the study fulfilled minimum requirements for nutrients in compost according to international standards, despite the fact that no consistent composting methods were followed. The results indicates that household or neighborhood composting could contribute to solving urban organic waste problems as well as the lack of organic fertilizer available for agriculture in urban and peri-urban areas. While distributing compost could be a challenge, it also provides an opportunity to strengthen links between farmers and consumers

Respuesta olfativa de larvas de phyllophaga raviday p. tumulosa ( melolonthidae) a volátiles de raíces de cuatro plantas hospederas

The olfactory responses of third instar larvae of Phyllophaga ravida (Blanchard 1850) and Phyllophaga tumulosa (Bates 1888) to Zea mays L. (Gramineae), Cynodon dactylon (L.) Pers. (Gramineae), Phaseolus vulgaris L. (Leguminosae) and Physalis philadelphica Lam. (Solanaceae) roots were studied in the laboratory. The olfactory response was investigated using a Y olfactometer. P. ravida larvae did not show any preference for roots of any of the four plant species, while P. tumulosa larvae preferred green tomato roots. The preference of both species of larvae for roots of maize, bean or green tomato was investigated in a glass terrarium. Phyllophaga ravida larvae were more frequently found in maize roots than in bean or green tomato roots, and larvae of this species increased significantly their weight in the combinations between bean-maize and green tomato-maize. Phyllophaga tumulosa larvae preferred green tomato roots to those of maize or beans and increased significantly their weight in the green tomato-maize combination. The olfactory preference of P. tumulosa for green tomato roots was corroborated in the terrariums. En este trabajo se investigó la respuesta olfativa de larvas de terceros estadios de Phyllophaga ravida (Blanchard 1850) y Phyllophaga tumulosa (Bates 1888) ante las raíces de Zea mays L. (Gramineae), Cynodon dactylon (L.) Pers. (Gramineae), Phaseolus vulgaris L. (Leguminosae) y Physalis philadelphica Lam. (Solanaceae). Se utilizó un olfatómetro Y, con una raíz de papel filtro como testigo; las larvas de P. ravida no mostraron preferencia olfativa por ninguna de las raíces probadas; mientras que las larvas de P. tumulosa prefirieron la del tomate verde. En terrarios de cristal se sembraron una planta de maíz (control) y otra de frijol o tomate verde, y se infestaron con dos larvas de P. ravida o de P. tumulosa, excepto los testigos, para registrar la preferencia hacia un tipo de raíz en el suelo. Las larvas de Phyllophaga ravida tuvieron mayor presencia en las raíces del maíz que en las del frijol o del tomate verde y aumentaron significativamente de peso en las combinaciones frijol-maíz y tomate verde-maíz. Las larvas de P. tumulosa prefirieron las raíces del tomate verde que las del maíz o del frijol, y aumentaron significativamente de peso en la combinación tomate verde-maíz. La preferencia olfativa de P. tumulosa por la raíz del tomate verde se corroboró en los terrarios

Lombricomposta para recuperar la fertilidad de suelo franco arenoso y el rendimiento de cacahuate (Arachis hypogaea L.)

La producción de cacahuate es una fuente de ingresos económicos importante para Chiapas, ocupando el segundo lugar a nivel nacional como productor. Jiquipilas es uno de los municipios productores del estado, pero su rendimiento ha disminuido en los últimos cuatro años (de 2.4 a 1.45 Mg ha-1) debido al manejo intensivo del cultivo, propiciando el deterioro paulatino de las propiedades físicas, químicas y biológicas de los suelos (pérdida de fertilidad) franco arenosos en que se cultiva. Así, el manejo de los suelos se ha convertido en una necesidad de subsistencia, por lo que el propósito de esta investigación fue evaluar el efecto de la incorporación de lombricomposta en el mejoramiento de las propiedades del suelo y el rendimiento del cacahuate (Arachis hypogaea L.), bajo condiciones de campo en la comunidad de José María Pino Suárez, municipio de Jiquipilas. El estudio se realizó en un solo ciclo (2016) en una parcela tradicionalmente sembrada con cacahuate. La lombricomposta se elaboró con residuos agrícolas de la región (estiércol, rastrojo de maíz y cacahuate). Se experimentó con cuatro diferentes dosis de lombricomposta (300, 225, 150 y 75 g), las cuales se complementaron con manejo agroecológico (sin insumos químicos e incorporación del deshierbe manual entre surcos como cobertura muerta); como tratamientos control se consideraron suelo con manejo intensivo (aplicación de fertilizantes, insecticidas, herbicidas sintéticos) y suelo con manejo agroecológico. La adición de lombricomposta al suelo tuvo efecto en las propiedades físicas (capacidad de campo, densidad real y en los espacios porosos); en cuanto a las propiedades químicas hubo resultados positivos en la disponibilidad de fósforo, potasio, hierro y manganeso, así como en el pH. También se obtuvieron mayores emisiones de CO2 por la actividad microbiana. La emergencia de plantas y su floración se dieron en menor tiempo con lombricomposta. Aunque se mostró una clara tendencia en el rendimiento del cultivo con la adición de lombricomposta, no se presentaron diferencias estadísticamente significativas

Leaching of microplastics by preferential flow in earthworm (Lumbricus terrestris) burrows

In the current study, we examine how the activities of earthworms (Lumbricus terrestris) affect microplastic (MP) distribution and concentration in soil, with a focus on low density polyethylene (LDPE). We also want to determine if MPs can be flushed out with water. We used a laboratory sandy soil column (polyvinyl chloride tube) experimental set-up and tested five different treatments: (1) treatment with just soil (control) to check if the saturated conductivity (Ksat) could be impacted by MP, (2) treatment with MP, (3) treatment with MP and litter, (4) treatment with earthworms and litter as a second control for treatment 5 and (5) treatment with MPs, earthworms and litter. Each treatment consisted of eight replicates. For the treatments with MP, the concentration of MP added at the start of the experiment was 7 % by weight (3.97 g, polyethylene, 50 % 1 mm-250 μm, 30 % 250 μm-150 μm and 20 % <150 μm) based on 52.78 g of dry litter from Populus nigra. In the treatments using earthworms, two adult earthworms, with an initial average weight of (7.14 ± 0.26) g, were placed in each column. Results showed that LDPE particles could be introduced into the soil by the earthworms. MP particles were detected in each soil sample and within different soil layers for the earthworm treatments. Earthworms showed a tendency to transport the smaller MP particles and that the amount of MPs in size class <250 μm increased in soil samples with increasing soil depth in comparison to the other size classes. After leaching, MPs were only detected in the leachate from the treatments with the earthworms, and the MP had similar size distributions as the soil samples in the 40-50 cm layer of the treatment with MP, earthworms and litter. The results of this study clearly show that biogenic activities can mobilise MP transport from the surface into the soil and even be leached into drainage. It is highly likely that biogenic activities constitute a potential pathway for MPs to be transported into soil and groundwater.</p

Microplastic appraisal of soil, water, ditch sediment and airborne dust: the case of agricultural systems

Although microplastic pollution jeopardizes both terrestrial and aquatic ecosystems, the movement of plastic particles through terrestrial environments is still poorly understood. Agricultural soils exposed to different managements are important sites of storage and dispersal of microplastics. This study aimed to identify the abundance, distribution, and type of microplastics present in agricultural soils, water, airborne dust, and ditch sediments. Soil health was also assessed using soil macroinvertebrate abundance and diversity. Sixteen fields were evaluated, 6 of which had been exposed to more than 5 years of compost application, 5 were exposed to at least 5 years of plastic mulch use, and 5 were not exposed to any specific management (controls) within the last 5 years. We also evaluated the spread of microplastics from the farms into nearby water bodies and airborne dust. We found 11 types of microplastics in soil, among which Light Density Polyethylene (LDPE) and Light Density Polyethylene covered with pro-oxidant additives (PAC) were the most abundant. The highest concentrations of plastics were found in soils exposed to plastic mulch management (128.7 ± 320 MPs.g-1 soil and 224.84 ± 488 MPs.g-1 soil, respectively) and the particles measured from 50 to 150 μm. Nine types of microplastics were found in water, with the highest concentrations observed in systems exposed to compost. Farms applying compost had higher LDPE and PAC concentrations in ditch sediments as compared to control and mulch systems; a significant correlation between soil polypropylene (PP) microplastics with ditch sediment microplastics (r2 0.7 p < 0.05) was found. LDPE, PAC, PE (Polyethylene), and PP were the most abundant microplastics in airborne dust. Soil invertebrates were scarce in the systems using plastic mulch. A cocktail of microplastics was found in all assessed matrices