Keywords

1 Introduction

Since the mass production of plastic started, the biosphere of the earth has been confronting a steadily increasing threat. Cumulative thrust for convenient yet cheaper products and modern lifestyle has boosted the annual production of plastic materials by leaps and bounds which is estimated to be about 34,000 million tons by 2050 (Plastics Europe, 2019; Maity & Pramanick, 2020). Trends of overdependence, indiscriminate utilization, less recycling propensity (only 9%), improper management of used products, etc. are leading the global annual plastic waste production to 6300 million tons approximately; a lion’s share of this finds a way to the terrestrial ecosystem (Geyer et al., 2017; Van Sebille et al., 2015). Consequently, soil possesses a far greater concentration of plastic materials than aquatic sediments as reported by Horton et al. (2017a, b) and Fischer et al. (2016). Furthermore, agro-ecosystem was reported as the most plastic contaminated terrestrial ecosystem by Nizzetto et al. (2016a, b). However, the distributive nature and interaction with components in the terrestrial ecosystem, specifically in agricultural soils, are still unclear.

Plastic products have gained universal popularity; hence widespread occurrence and distribution of plastic materials can be traced easily. Worldwide contamination of soil by smaller plastic particles has been mentioned by several studies (Fuller & Gautam, 2016; Scheurer & Bigalke, 2018; Koutnik et al., 2021). Zhang et al. (2021) identified the variation in abundance of global soil MPs which is thought to be connected with the physiographical nature, development activities, population densities, soil properties, and other features of that area (Harms et al., 2021; Kim et al., 2015). Recently, detection of plastic particles has been confirmed in distant places like the Polar Regions and the Tibetan Plateau where anthropogenic interference is severely less (Jiang et al., 2019; Peeken et al., 2018). Upon deposition on surface soil, plastics undergo disintegration and degradation processes resulting in smaller MPs and even NPs (Rocha-Santos & Duarte, 2015; Cole & Galloway, 2015; Barnes et al., 2009). Meanwhile, previously generated MPs can also directly enter the terrestrial ecosystem as primary MPs (Napper et al., 2015) (Fig. 3.1).

Fig. 3.1
A world map indicates the global abundance and is categorized based on the distribution of microplastics. The different concentrations of microplastics and boundaries in the country are marked on the map.

Showing the global abundance and distribution of microplastics on the agricultural soil

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Previous studies have identified the sources and pathways of MP contamination in farmland soil and reported plastic mulch, application of compost and sludge, irrigation with untreated and partially treated water, plastic container, atmospheric deposition, etc. as the main sources (Corradini et al., 2019; Blasing & Amelung, 2018; Rillig, 2012; Sanchez-Hernandez et al., 2018).

Once entered the agricultural soils, MPs and NPs can be transferred both vertically and horizontally through soil pore spaces (Zhang et al., 2019; Lwanga et al., 2017a, b; Horton et al. 2017a, b; Rillig et al., 2017b) or can be bioaccumulated into the human food chain and endanger health (Zhang et al., 2019; Machado et al., 2019). Hence, a detailed understanding of the distribution and transportation of MP and NP in soil may serve as a vital factor for controlling plastic contamination. Unfortunately, the scarcity of published reports on the movement and transportation nature of MPs in the terrestrial ecosystem reveals the fact that it has gained less attention from the researcher community, compared to aquatic systems (Möller et al., 2020; Brady & Weil, 2000). As a result, several information gaps need to be addressed. Consequently, a knowledge gap has been created.

This review study aims to gather data about the global trend of accumulation and abundance of MPs and NPs in the terrestrial ecosystem. Moreover, several factors which control the distribution behavior of MPs and NPs in farmland soils have been discussed with a view to providing a base material for the better realization of transportability of smaller plastic particles in agro-ecosystem.

2 Factors Controlling the Distribution of MPs and NPs in Soil

Since plastic has got an overwhelmingly ubiquitous nature, it is obvious that MPs and NPs will be found in the terrestrial ecosystem. Smaller plastic materials enter into the agro-ecosystem as manufactured MPs and NPs primarily or secondarily as produced from the bigger plastic materials (Rillig, 2012; Duis & Coors, 2016; Koelmans et al., 2015). Plastic mulch, greenhouse materials, atmospheric deposition, etc. are considered as direct sources, while indirect sources include application of organic amendments, irrigation with wastewater, application of sludge, etc. (Ng et al., 2018; Duis & Coors, 2016; Horton et al. 2017a, b). Once entered, plastic materials may undergo disintegration and degradation processes, generating MPs and NPs eventually (Napper & Thompson, 2019; Chamas et al., 2020). Having convenient size compared to the pores of the soil, MPs and NPs can be distributed spatially and horizontally. This phenomenon of movement in agro-ecosystem is governed by several factors: morphology of the plastic, precipitation, properties of soil, cultivation, etc. (Zhang et al., 2018).

2.1 Properties of Soil

Physicochemical properties of soil such as texture, moisture content, temperature, soil reaction, etc. directly affect the movement of MPs and NPs in soil. Soil texture straightly determines the pore space distribution which is very crucial for the translocation of smaller plastic particles within the layers of soil (Rahmatpour et al., 2018; Cey et al., 2009). Light textured soil (containing higher sand percentage) tends to have bigger pore spaces (macropores) which will enable the soil to permit more vertical movement of microplastics (Rillig et al., 2017b) than soils with higher clay and silt content, respectively. In addition, Ding et al. (2021) recently studied the abundance of MP in soils of three sites, and they found that sand soil had higher MP content than grassland and woodland.

Soils containing a greater amount of montmorillonite and other expanding clay minerals will generate cracks and fissures upon drying. These cracks can pave the way for massive transportation of plastic particles of various sizes directly at the deeper part of the soil profile very quickly (Rillig & Lehmann, 2020). Similar findings were observed in several other studies (O’Connor et al. 2019a, b; El-Farhan et al., 2000; Majdalani et al., 2008) implying the significant effects of interconnected pore space pathways and wet-dry cycles on the transport of MPs in a terrestrial ecosystem. Meanwhile, previous experiments reported the significant reduction of microplastic movement with increasing ionic attachment in a media of quartz sand (Treumann et al., 2014; Pelley & Tufenkji, 2008). Moreover, chemical properties of soil, namely, soil pH and Fe/Al content, influence the distribution of MPs and NPs as mentioned by some studies (Wu et al., 2020; Scheurer & Bigalke, 2018).

2.2 Morphology of MP and NP

The distribution of MP and NP in the soil is most reliant on their various morphological characteristics, such as size, density, shape, hydrophobicity, etc. (Rillig et al., 2017a). Previous several studies have enlightened on the influence of size and hydrophobicity of plastic materials upon their movement in the terrestrial ecosystem (O’Connor et al. 2019a, b; Pelley & Tufenkji, 2008). David O’Connor et al. (2019a, b) studied the mobility of five different MPs and found that mobility of smaller-sized PE-MP was greater than any other with the longest penetration. A same observation regarding the size-mobility inverse relation of MPs has also been reported by Rillig et al. (2017b). Furthermore, Liu et al. (2018) investigated arable soils around the suburbs of Shanghai and noticed relatively larger MPs in topsoil varying significantly from deeper soil (Hurley & Nizzetto, 2018).

Shape is another morphological factor that affects the fate of mobility of plastic materials in a terrestrial system. MPs and NPs are found with various shapes in soil, for instance, sphere, particle, fiber, and film mostly. Among them, sphere and particle are being widely used for recent relevant researches showing that microplastic particles of these two shapes can easily translocate to the deeper part of the soil (Lwanga et al., 2017a, b; Rillig et al., 2017b; Treumann et al., 2014; Zhuang et al., 2005). On the other hand, in a review study, Rillig et al. (2017b) assumed different distributive behavior of other shapes such as film, fiber, etc. from the sphere. They predicted that fiber and film-shaped smaller plastic particles have a possibility to be trapped in the soil matrix and can become surrounded by an eco-corona likewise aquatic system (Galloway et al., 2017). In addition, the reviewers also reported that the movement of MPs and NPs in the soil system would be substantially influenced by eco-corona. Their findings are consistent with Zhang et al. (2019). Meanwhile, low-density microplastics had fewer tendencies to move downward as mentioned by O’Connor et al. (2019a, b).

After the entrance, MPs and NPs confront several processes like attachment, sedimentation, etc. which can hinder the strolling of plastic particles in soil (Zhang & Liu, 2018; Rillig et al., 2017a). Previous experiments on movement behavior of colloids in different media found straining, attachment at the solid-liquid interface, pore exclusion, and air-water interfacial bond as the significant factors in particle movements through soil (Zhuang et al., 2005; Bradford & Torkzaban, 2012; Bradford et al., 2002).

2.3 Soil Biota

Previous experiments have mentioned that biogenic activities could instigate the transfer of smaller particles from the surface into the deeper part of the soil by creating interconnected pore space pathways (Blasing & Amelung, 2018; Zubris & Richards, 2005). In a review study, Rillig et al. (2017b) reported earthworms and roots as the most important producers of bio-macrospores in soil. They expected similar results from micro arthropods. Moreover, Huerta Lwanga et al. (2016) reported that earthworms can contribute to microplastic movement from the surface soil to the deep soil by ingestion/excretion mechanism. The capability of the conversion of primary MPs to secondary MPs and NPs through ingestion by earthworms and some other soil-dwelling organisms, for instance, burrowing mammals, collembolan, mites, etc., has been reported in some studies as well (Zhu et al., 2019; Rillig, 2012).

Previous studies found evidence of vertical and horizontal movement of LDMPs in soil facilitated by collembolan, earthworms, and other organisms (Maaß et al., 2017; Rillig et al., 2017b; Lwanga et al., 2017a, b). Besides, direct transportation of LDMPs by preferential flow through the pore space pathways was mentioned by Yu et al. (2019). Moreover, Zhang et al. (2019) conducted a study combining field investigations and laboratory simulations to examine LDMP distribution and controlling factors in agricultural soils. They found evidence of vertical as well as horizontal movement of LDMPs along with water through pore space pathways of soil. Maaß et al. (2017) conducted a study with two species of collembola and confirmed the movement and distribution of MPs by both species. In another study, Zhu et al. (2018) mentioned that mites can also disperse commercial PVC particles.

Root penetration, expansion, and water extraction create pores and channels within soils which facilitate downward translocation of smaller particles as reported by Gabet et al. (2003). In addition, the decomposition of roots produces macropores of nearly the same size, which can distribute MPs in soils (Li et al. 2019a, b). Another study revealed that fungal hyphae might facilitate MP movement by serving as preferential paths (Wick et al., 2007). Leaching contributes significant microplastic transportation vertically in soils through pore spaces created by naturally or biogenic activities (Cey et al., 2009). However, there is no comparative analysis of microplastic particles movement by earthworm or other soil biota and leaching in soil.

2.4 Cultivation

Agronomic activity such as plowing, mulching with plastics, application of sludge, application of organic amendments, irrigation with wastewater, etc. cause the mobilization of MP and NP in surface soil and subsurface soil. The findings of several recent pieces of research have proven the fact that cultivation activities help to spread around plastic particles in any agro-ecosystem (Nizzetto et al., 2016b; Zhang et al., 2019). Ding et al. (2020) found a significantly higher number of MPs in orchards which they thought for massive utilization of plastic for packaging. Rillig and Lehmann (2020) reviewed the effect of different tillage practices on microplastic incorporation in different depths of agricultural soil. They noted that mould board plowing brings most of the MPs present on the soil surface at the plowing depth. Besides, they noted that other tillage practices would show mixing effects throughout the tillage layer.

Mulching with plastics, a widely practiced trend of modern farming, has been established as a major source of plastic materials in agro-ecosystem by numerous studies (Sintim & Flury, 2017; Zhou et al. 2019a, b; Gao et al., 2019). Once embedded in the soil, it can be converted into MPs and NPs (Blasing & Amelung, 2018). Wang et al. (2021) studied samples of different land-use patterns from five provinces of China and found significantly higher particle abundance where plastic mulching was used. Furthermore, they noticed that the MP abundance of paddy fields was significantly higher than wheat lands. Plastic mulch affects the agro-ecosystem inversely since plastic covering can raise both soil temperature and moisture which can intensify the degradation and transportation rate of MPs (Subrahmaniyan et al., 2006). Moreover, decomposition of other agricultural plastic materials such as seed bags, packaging materials, agricultural plastic tools, etc. can add MP in farmlands (Antunes et al., 2013). Chen et al. (2020) added polytunnels, bale twines, fertilizer bags, containers, and nets to the list which can be a source factor of plastic materials in agro-ecosystem.

Application of sludge to amend the soil is reported by many studies to be a significant input pathway of smaller fractions of plastics in farmland soil (Ziajahromi et al., 2016; Zhou et al., 2020; Nizzetto et al., 2016b). An estimation made by Nizzetto et al. (2016b) revealed that about 4.4 × 104–3 × 105 tons and about 6.3 × 104–4.3 × 105 tons of MPs enter arable soil annually because of use as the amendment in North America and Europe, respectively. The findings of Chen et al. (2020) are consistent with this. Meanwhile, organic farming involves the utilization of organic fertilizers (namely composts) which are commonly produced from household waste or municipal waste. These composts may have a MP concentration of 895 items kg−1 as reported by Weithmann et al. (2018). On the other hand, irrigation with wastewater can serve as a source and distributor of plastic materials both spatially and vertically in agricultural soil (Scheurer & Bigalke, 2018). Mintenig et al. (2017) showed that about 20 million hectares of arable land worldwide are irrigated with untreated or partially treated sewage water on which about 10% of the world’s population depends on the food. On the other hand, Rillig and Lehmann (2020) considered bio-pores created by decomposed roots after harvesting as a massive transport pathway of MPs and NPs in agricultural systems. They also reported that harvesting submerged parts of plants beneath the surface (carrots, potatoes, etc.) can also facilitate to incorporation and transportation of microplastics in farmland. Li et al. (2019a, b) also attributed that harvesting of rhizome may serve the downward movement of microplastics.

2.5 Weather Pattern

The weather pattern of an area can affect the distribution and accumulation of MPs and NPs significantly. An area with annual heavy rainfall may experience surface runoff which can mobilize plastic materials spatially over a huge area. With the flow coming from the source, plastic materials can be floated away to distant locations. Previous studies indicated that flow length and catchment size showed a positive correlation with the number of possible plastic sources and distribution (Klein et al., 2015; Tibbetts et al., 2018; Fischer et al., 2016; Ballent et al., 2016). A study on the abundance of plastics in the Swiss floodplain was carried out by Scheurer and Bigalke (2018). They identified the distribution of plastic as diffuse and found a linkage of the lateral distribution process with flood dynamics. Moreover, such flushing movement of water determined by topographical and weather factors can carry smaller plastic materials even through soil pores spaces of soil horizontally and vertically (Zhang et al., 2017; Zhang et al., 2011). Meanwhile, O’Connor et al. (2019a, b) reported upward migration of MPs if saturation prevails in soil pore spaces since MPs have relatively low specific density. On the contrary, during hot days with no precipitation, dry soils will likely have natural cracks, which can serve as entryways for microplastics to deeper soils (Li et al. 2019a, b). In addition, dry hot days will intensify MP conversion to NP with the help of UV radiation and elevated temperature (Horton et al. 2017a, b).

Ding et al. (2020) conducted a research with agricultural soils from nine sites across Shaanxi province, and they observed that in northern Shaanxi, MPs were not gone by surface runoff, causing massive accumulation while the situation appeared reverse in the case of southern Shaanxi, where they found degraded smaller MPs. They explained their findings focusing on the weather pattern difference between northern and southern Shaanxi since the northern part had the temperate monsoon climate and less rainfall for the southern Shaanxi; it was just the opposite.

Weather patterns involving subsequent cycles of rainfall events and dry periods may have an impact on the mobility of MPs into the soil (O’Connor et al. 2019a, b; McCarthy & McKay, 2004). O’Connor et al. (2019a, b) studied the mobility of five different MPs in sand soil column experiments. They found a significant positive relationship between MP penetration and wet-dry cycles. However, more research should be carried out for a better understanding of the effects of weather patterns on the distribution of MPs and in soil.

3 Summary of Regional MP and NP Abundance in Soil

3.1 Africa

The first report on the abundance and occurrence of microplastic in the African continent was done by Ryan in 1988 where the accumulation of pieces of plastic at the seafloor of the southwestern Cape Province of South Africa was studied from August 1977 to August 1978. After 27 years of the first study done in Africa, microplastic in the surface water of south-eastern major bays of South Africa was evaluated (Nel & Froneman, 2015).

In the region of South Africa, an extent of 13.3–563.8 items/kg of microplastic and nanoplastic have been detected in the river sediments of Eastern Cape Town (Nel et al., 2018), and the concentration in the region of Braamfontein Spruit, Johannesburg, has been found to be 166.8 items/kg (Dahms et al., 2020). Particles identified in the Lake Ziway sediments of Ethiopia have a range from 6.3 to 115.9 items per kg of freshwater sediments (Merga et al., 2020).

Comparatively, a high concentration of MP and NP has been found in Tunisia where an amount of more than 6920 particles has been reported in the region of Bizerte (Toumi et al., 2019). A much lower distribution (316.03 ± 123 items/kg) has been detected in the sediments of Tunis lake (Abidli et al., 2019) (Table 3.1).

Table 3.1 Distribution of microplastics and nanoplastic in terrestrial ecosystems across Africa
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3.2 America

Several pieces of research have been gathered in this study to give an overview of the abundance of microplastics in the soil of the Americas. These researches looked at the usage of sewage sludge and biosolids as a source of microplastics. In a study, it has been estimated that biosolid applications might provide up to 300,000 tons of MPs to farmed soils in North America each year (Nizzetto et al., 2016a, b). In Ontario, Canada, microplastic abundance is found to be at a range of 8700–14,000 MPs/kg in biosolid samples (Crossman et al., 2020).

A study had been conducted in the city of New York, USA, where samples were collected from four sites, and the findings revealed MP concentration ranged from 370 to 2060 items/kg−1 with a mean of 1235 items per kg. This result is comparable to the amount of sewage sludge applied to worldwide soils (Zubris & Richards, 2005).

A study (Corradini et al., 2019) of 31 agricultural fields in Chile found that the concentrations of those areas range from 0.6 to 10.4 MPs/g. But it revealed that after five sewage sludge applications, the concentration amount increased to 3600 items/kg from 1200 items/kg.

In Brazil, it has been found that the sediments near municipal dumping sites have a significant concentration of MP (Neto et al., 2019), and the study also expressed that the presence of MP was detected in 100% of the samples; however, no specific data on agricultural soil was obtained.

Another study (Lwanga et al., 2017a, b) measured plastic particles in a rural field on the Yucatán Peninsula of Mexico where a total of 870 ± 1900 items/kg of microplastics were discovered (Table 3.2).

Table 3.2 Distribution of microplastics and nanoplastic in terrestrial ecosystems across America
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3.3 Asia

In Asian countries, the pervasiveness of microplastics (MP) is a severe environmental concern. According to the literature, Asia is home to seven of the top ten trash-dumping countries (Jambeck et al., 2015). To acquire an overview of the abundance and distribution of microplastics across Asia, a variety of studies have been collated and discussed.

Southern Asia

In Southern Asia, the highest abundance is found in Pakistan. A study was carried out in Pakistan to map out the regional dispersion of microplastics in the topsoil Lahore, Pakistan. The distribution of MPs in topsoil throughout the Lahore district was discovered to range from 1750 to 12,200 MPs per kg, with a mean of 4483 ± 2315 items/kg. In agricultural soil MP concentration was found in the range of 2200–6875 MPs per kg with a mean concentration of 3712 ± 2156 MPs per kg of soil (Rafique et al., 2020). In India, MPs were identified in soils collected from electronic waste-dumping sites. In Bangalore and Chennai, the average MP estimates were 302 and 1908 items/kg, respectively (Tun et al., 2022). Traditional plasticizers like dibutyl phthalate, dimethyl phthalate, and di(2-ethylhexyl) phthalate were detected in high abundance (Chakraborty et al., 2019). PE was also found to be a dominated polymer in Indian soils of dumping sites which account for 55% of total MP (Chai et al., 2020a, b).

In the case of Bangladesh, most of the recent studies have reported the abundance of microplastic in the sediments of the coastal environment (Rahman et al., 2020; Tajwar et al., 2021, 2022a, b; Rakib et al., 2021), where MP concentration had been found about 8.1 ± 2.9 particles/kg. However, the concentration of MP & NP based on the terrestrial ecosystem is yet to be evaluated (Table 3.3).

Table 3.3 Distribution of microplastics and nanoplastic in terrestrial soil across Southern Asia
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South-eastern Asia

MPs have also been discovered in alarming figures in the countries of Southeast Asia. In Indonesia, many areas continue to operate open dumping sites, which are a potential source of MPs (The Jakarta Post, 2019). In one Indonesian sampling site, MP distribution was highest at 43,704 particles per kg, followed by 16,842 and 11,111 pieces/kg in two other sites. The dumping site’s entrance revealed a significant MP abundance (16,842 pieces/kg). The median number of MPs in the soil is 6061 pieces/kg (Tun et al., 2022).

According to research in Cambodia, the median MP concentration in Cambodian soils was determined to be 4360 pieces per kilogram. It demonstrated the maximum abundance of MP (218,182 pieces/kg) in one Cambodian sampling site, with 48 MP found in only 0.22 g of soil (Tun et al., 2022). From a study on Asian countries, it is found that the average value of microplastic was highest in the Philippines counted for 24,000 pieces/kg. MP levels were found to be high in soils from two sampling sites of the Philippines, containing 31,000 and 24,000 pieces/kg, respectively (Tun et al., 2022). In Vietnam, the median of MPs in soils was about 11,337 pieces/kg, but the highest abundance is found about 83,606 pieces/kg, followed by 28,358 pieces/kg and 26,768 particles per kg. Soil samples accumulated from two e-waste recycling areas close to Ho Chi Minh City showed high abundance of MP, containing 17,568 and 26,761 items per kg (Tun et al., 2022). In Laos, the highest MP abundance was accounted for 22,222 pieces/kg from a dumping site. MPs were detected from the other three sampling sites ranging from 893 to 4651 items per kg, and the samples had been taken from a rice field near a landfill area. The median value of MPs in soils of Laos was 4651 pieces/kg (Tun et al., 2022) (Table 3.4).

Table 3.4 Distribution of microplastics and nanoplastic in terrestrial soil across South-eastern Asia
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Middle East

Rezaei et al. (2019) investigated the transmission of MPs by wind erosion measuring the abundance of MPs (low-density) in the soils of Iran’s Fars province. 1.2 ± 0.6 and 205 ± 186 mg per kg had been identified at agriculture-based locations, but only 0.2 ± 0.1 and 38 ± 17 particles per kg were found on rangelands. The primary source of MPs in these areas was assumed to be insufficient removal of plastic mulch films (Büks & Kaupenjohann, 2020) (Table 3.5).

Table 3.5 Distribution of microplastics and nanoplastic in terrestrial soil across the Middle East
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Eastern Asia

In Eastern Asia, China is the only country that performed MP measurement in more than 15 regions, and from those researches, it is found that MPs are highly distributed all over China. As significant amounts of plastics are manufactured, consumed, and discharged in China each year, soil microplastic pollution deserves special attention (Gourmelon, 2015). In China, the amount of plastic garbage that had been improperly managed was found to be the highest in 2010, at 8.82 million tons (Jambeck et al., 2015). Ding et al. (2020) examined the abundance of MPs in the agriculture-based sites of Shaanxi Province, China. They discovered that MPs were present in all agricultural soils. MP concentrations in soil ranged from 1430 to 3410 items/kg. The findings of this research validated the existence of a high concentration of MPs in farmland soil and demonstrated that activities related to agriculture could have contaminated the soil with MPs. If we look carefully, it will be observed that soils with a history of sewage sludge application, wastewater irrigation, and mulching contain more MPs (Zhang & Liu, 2018). It is estimated that sludge application in China contributes approximately 1.56 × 1014 sludge-based MPs to the natural ecosystem (Liu et al., 2018).

A distant agricultural area in China’s Loess Plateau consisted only of 0.54 mg of MPs per kg of a soil sample, whereas the use of sewage sludge to agricultural soil enhanced the MPs concentration to 15,800 MPs/kg (Mahon et al., 2017; Zhang et al., 2018). Huang et al. (2020) investigated agricultural soils by examining 384 sediment samples gathered from 19 provinces across China. In places where plastic mulching was employed consistently, microplastic particle abundance rose over time, with an amount of 80.3 49.3, 308138.1, and 1075.6346.8 items per kg soil in fields with 5, 15, and 24 years of continuous mulching, respectively.

Zhang and Liu (2018) took polymer samples from one untreated afforested site close to Kunming and four farmland locations with sewage sludge and wastewater application. They discovered average concentrations of 26,070 items/kg with a minimum concentration of 13,470 items/kg and a maximum concentration of 42,960 particles per kg in farmland Gleysol, 14,440 particles per kg (min, 8180 particles/kg; max, 18,100 particles/kg) in an afforested Gleysol and 12,050 particles per kg (min, 7100 particles/kg; max, 26,630 particles /kg) in farmland Nitsol. This suggests that not only the plastic load but also the soil type are considered as factors in MP concentrations in soils. Zhou et al. (2019a, b) investigated the prevalence and quantity of MPs, as well as their interactions with heavy metals, across three different subareas in central China. The concentration of MPs ranged from 2.2 × 104 to 6.9 × 105 items/kg according to the findings. MP distribution was much greater in the forest (4.1 × 105 items/kg) compared to the vegetable land (1.6 × 105 items/kg) or barren land (1.2 × 105 items/kg) (Table 3.6).

Table 3.6 Distribution of microplastics and nanoplastic in terrestrial soil across Eastern Asia
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Another study on Yunnan, China, showed MP concentrations ranged from 7100 to 42,960 particles/kg with an average concentration of 18,760 particles/kg in cropped soils (Zhang & Liu, 2018). In Shanghai, the abundance of microplastics in shallow and deep soils was 78.00 ± 12.91 and 62.50 ± 12.97 items/kg, respectively. Furthermore, topsoil had a higher amount and greater sizes of micro(meso)plastics compared to deep soil, according to this study (Liu et al., 2018). Chai et al. (2020a, b) studied 33 samples of soil collected from an e-waste disposal region in China’s Guangdong Province. MP was found in 30 soils, with a maximum distribution of 34,100 items/kg, indicating that an e-waste disposal location has developed into a hotspot for MP. In another study, MP abundance is found in soils from an e-waste recycling facility ranging from 600 to 14,200 pieces/kg (Zhang et al., 2021).

According to a Korean study, the soils of Yeoju had a mean of 700 items/kg of microplastics, with the highest amount of microplastics detected from upland soil (3440 items/kg). Though the average dispersion of microplastics in soils samples of agricultural land was 664 pieces/kg, this varied by farming type; orchard sites had the highest abundance, followed by greenhouse, upland, and paddy field sites (Choi et al., 2021). The high concentration of microplastics in agricultural soils (664 ± 83 pieces/kg) highlighted the influence of agricultural activities on soil microplastic contamination, which is likely related to the mulching and usage of vinyl films (Rodríguez-Seijo & Pereira, 2019).

3.4 Antarctica

Analysis of the abundance of MPs & NPs has been done along the nearshore region of Ross Sea, Antarctica, where the range has been detected to be 0.0032 to 1.18 particles/m3 with an average amount of 0.17 ± 0.34 particles/m3 (Cincinelli et al., 2017) (Table 3.7).

Table 3.7 Distribution of microplastics and nanoplastic in terrestrial ecosystems across Antarctica
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3.5 Australia

The concentration of MPs and NPs in soils near an industrial facility has been detected to be of the amount 2400 mg/kg on an average in Sydney of Australia. The min amount has been found to be 300 mg/kg, and the max amount has been recorded to be 67,500 mg/kg, which can be considered as a high contamination region. (Fuller & Gautam, 2016) (Table 3.8).

Table 3.8 Distribution of microplastics and nanoplastic in terrestrial ecosystems across Australia
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3.6 Europe

According to several studies, MPs and NPs have been found in sediments, seawater, and freshwater across Europe. The Table 3.9 represents the distribution of MP and NP in the terrestrial ecosystem across Europe. Italy, Spain, the Netherlands, and the UK recorded the presence of a high amount of MPs and NPs within the sediments with Spain showing the highest amount MP and NP of 3330 items/kg detected in the croplands of the rural areas of Valencia (van den Berg et al., 2020).

Table 3.9 Distribution of microplastics and nanoplastic in terrestrial ecosystems across Europe
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The highest amount of MPs and NPs has been found to be 1108 ± 983 items/m2 in the sediments of the Lake Garda (Imhof et al., 2017). Concentration in the regions of Lake Bolsena and Lake Chiusi has been detected to be 112 and 234 items/kg (Fischer et al., 2016). The distribution of MPs and NPs in the country of Italy has been found to be directly proportionate to the presence of industries and human-induced contamination. Human activities, tourism, industrial activities, and urban development are directly related to the pollution of MPs and NPs (Frère et al., 2017; Gündoğdu & Çevik, 2017; Tubau et al., 2015; de Lucia et al., 2014; Barnes et al., 2009). MP and NP contamination in sediment is found to be higher where there’s a high human settlement (Collet & Engelbert, 2013).

A higher concentration of MPs and NPs has been reported in the sediments of the Meuse River (1400 items/kg) of the Netherlands compared to the abundance detected in the sewage sludge (650 items/kg) by Leslie et al. (2017). A high concentration of MP and NP (660 and 300 items/kg) has also been recorded in the regions of River Thames Basin and Edgbaston Pool, Birmingham, of the UK (Horton et al. 2017a, b; Vaughan et al., 2017).

However, the distribution of detected MP and NP has been found to be significantly low compared to the other studied regions in the terrestrial ecosystem of France and Germany where the amount has been reported to be 0.06 to 1 and 0.892777 items/kg, respectively (Schmidt et al., 2018; Mani et al., 2015).

The presence of buoyant MPs and NPs detected in the sediment serves as a testament to the existence of different types of microplastic getting trapped in sediment during the process of sedimentation (Chae et al., 2015). The deposition of these sorts of MPs within the sediments relates to the extent of maturity which modifies the item thickness, shape, and the improvement of surface biofilm (Long et al., 2015; Cózar et al., 2014).