An Overlooked Entry Pathway of Microplastics into Agricultural Soils from Application of Sludge-Based Fertilizers.

The widespread application of sewage sludge produced from wastewater treatment plants for agricultural use has been regarded as a primary source of microplastics (MPs) into soils. However, little is known regarding MPs in sludge-based fertilizers and their relevant fate in soils as being applied in agriculture. We comprehensively investigated the abundance, polymer size, type, and morphology of MPs in dewatered sludge, sewage sludge composts, sludge-based fertilizer-amended soils, and earthworms by stereoscopy and micro Fourier transform infrared (µ-FTIR) spectrometry methods. The results clearly showed that the quantity of MPs in soils exhibited a close correlation with the application rate of sludge-based fertilizers. The total abundances of MPs were 545.9 and 87.6 items/kg in soils after annual amendment with 30 (field A) and 15 t/ha (field B) of sludge composts, which is significantly higher than that without compost application (field C, 5.0 items/kg). Correspondingly, MPs were found in earthworms with low quantities of 1.8 and 0.4 items/individual in fields A and B, respectively, while no MP was detected in field C. We speculate that sludge composts may act as a vehicle of MPs into soils and then enter soil biota and in turn influence the spread of MPs in the environment.

Microplastics in freshwater and wild fishes from Lijiang River in Guangxi, Southwest China.

Microplastics (MPs) are ubiquitous contaminants of emerging concern that have gained great attention recently due to their widespread appearance in the environment and potential adverse effects on living biota. Lijiang in Guangxi in China is a world-famous place of tourist attraction and attracted thousands of visitors every year. However, little is known regarding occurrence and distribution of MPs in freshwater and wild fishes in the Lijiang River. In this study, we used stereoscopy and micro Fourier transform infrared spectrometry (µ-FTIR) methods to investigate the abundance, morphotype, size distribution, and polymer type of MPs in freshwater collected by plankton nets and bulk sampling by pumping and filtration. Results showed that abundance of MPs in freshwater with bulk sampling by pumping (67.5 ± 65.6 items/m3) was significantly higher than those using plankton nets (0.67 ± 0.41 items/m3 and 0.15 ± 0.15 items/m3 for mesh sizes of 75 µm and 300 µm, respectively). An average abundance of MPs detected in wild fishes was 0.6 ± 0.6 items/individual, of which, a majority was found in the gastrointestinal tracts. Large-sized (>0.3 mm) and colored MPs in morphotypes of flakes and fibers dominated in both freshwater and wild fishes. Polypropylene-polyethylene copolymer and polyethylene were the top two abundant polymer types of MPs in freshwater, while polyethylene terephthalate dominated in wild fishes. This study provides evidences for our better understanding of pollution status of MPs in the Lijiang River.

Distribution of microplastics in surface water and sediments of Qin river in Beibu Gulf, China.

As a series of pollutants, microplastics have recently attracted widespread attention worldwide. In this study, different surface water and sediment samples were collected at 12 sampling sites along the urban section of Qin River in Guangxi Province, China. Water samples were collected using plankton nets with two different pore sizes (75 µm and 300 µm) and Teflon pump system with 25 µm mesh screen. The results showed that there was no significant difference in the abundance, particle size, and type of microplastics (F = 0.302, P = 0.588) between the two plankton nets, but the microplastic abundance in the samples collected by the Teflon pump was significantly higher (F = 9.12, P = 0.001), especially for microplastic fibers (F = 9.525, P = 0.001). Compared with the plankton net sampling method, the Teflon pump sampling had a smaller sample volume, resulting in a higher estimate of microplastic abundance in the water column. The microplastic abundance in the sediments was 0-97 items·kg-1 dry weight. PE and PP were the main types of microplastics in Qin River, accounting for 67.2% and 72.3% in the water column and sediments, respectively. The microplastics in the water column and sediments were dominated by large-sized particles in the range of 1-5 mm. The sources of microplastic pollution in Qin River may be affected by many factors, including population density, industrial structure, and aquaculture activities. However, aquaculture activities were generally the main source of microplastic pollution in Qin River estuary. Wastewater treatment plants (WWTPs) could effectively decrease the microplastic abundance in urban sewage, reducing the impact of urban sewage discharge on microplastic accumulation in Qin River.

[Impact of a Sewage Treatment Plant on the Accumulation of Microplastics in Freshwater Organisms in the Lijiang River of the Guilin Urban Section].

Microplastics (MPs, particle size<5 mm), as a new pollutant, have attracted wide attention in recent years. The distributions of MPs in effluent of a sewage treatment plant (STP) were examined. Surface water, sediment, and freshwater organism samples were taken from the STP discharge outlet in the Lijiang River tributary (S1), the confluence of tributaries and main streams in the Lijiang River (S2), and downstream locations in the Lijiang River (S3). The impact of STP discharge effluent on the characteristics and spatial distribution of MPs pollution in freshwater organisms was studied. The results showed that the freshwater organisms had a probability of uptake of MPs by 94.2%. The mean abundance of MPs in S1 (2.7 n·ind-1) was significantly higher than that of S3 (1.9 n·ind-1, P<0.05). The MPs found in S1 and S3 were mainly <0.10 mm, accounting for 46.0% and 30.5%, respectively. The fiber type of MPs was observed in the body of freshwater organisms. Polyethylene terephthalate was the major polymer form in S1 organisms, while polypropylene was the major polymer form in S3. The effluent discharged from the STP led to the accumulation of MPs in freshwater organisms.