Microplastics in Qinghai-Tibet Plateau and Yunnan-Guizhou Plateau lakes, China

Potential risk of microplastics in plateau karst lakes: Insights from metagenomic analysis

Microplastic (MP) pollution has become one of global concern. While MP pollution in lakes has been well studied, research on MP sources, distribution, and ecological risks in the Tibetan Plateau is limited. We systematically investigated the MP abundance and distribution in alpine travertine lakes in Jiuzhai nature reserve located in east edge of Qinghai-Tibetan Plateau and assessed the distributions of microbiomes, antibiotic resistance genes (ARGs), and virulence factor genes (VFGs) in water, sediments, and MPs, using macrogenomics. MP abundance was 20.27-58.80 n/L in water and 583.33-996.67 n/kg in sediments. MPs were dominantly fibrous and transparent. The particle size distribution was 0.1-0.5 mm for MPs in water, and 0.5-1 mm in sediments. MPs were mainly composed of polyethylene and polyethylene terephthalate. The microbial community of MP biofilms differed from that in the surrounding environmental medium, and Proteobacteria were more abundant in biofilm than in water and sediment. MP biofilms exhibited more cooperative behavior with microorganisms in water than with those in sediments. MPs were selectively enriched for ARGs and VFGs, and MP biofilms had a higher diversity of ARGs, the most abundant isoform being msbA, which is a multidrug resistance gene. VFGs were more abundant in MP biofilms than in water and sediment. The study results are useful for understanding MP sources and ecological risks in plateau karst lakes and provide a valuable dataset and theoretical basis for studies on MP pollution in other alpine calcareous lakes.

Potential ecological risk of microplastics contamination to environment in protect area lakes

Microplastics (MPs) in freshwater have been extensively studied on a global scale. However, a deeper understanding is still required regarding the occurrence characteristics and ecological risks of MPs in protected area lakes(PAL). Here, the study investigated MPs pollution in PAL, outside protected areas lakes (OPAL), and ponds (OPAP) in the eastern Qinghai-Tibetan Plateau, and a comprehensive analysis was conducted comparing lakes or ponds from different income regions. The results showed that PAL has a single source of contamination, while OPAL and OPAP exhibited more diverse MP sources. The surface of all samples showed significant physicochemical changes like oxygen-containing functional groups and potential signs of biodegradation. Microbiome analysis identified potential plastic-degrading bacteria on MPs, which varied by polymer type. Ecological risk assessment revealed that OPAL and OPAP face higher ecological risks, particularly from polymers like PVC and PC, while PAL has low risk. However, we should also consider the environmental changes over the past 100 years of history in this region and emphasize the environmental health of PAL. Notably, MPs pollution is more severe in lower-middle-income regions, highlighting the urgent need for stricter controls.

Microplastic pollution in Taihu Lake: Spatial distribution from the lake inlet to the lake centre and vertical stratification in the water column

The aim of this study was to analyse the distribution characteristics of microplastics in lakes, assess their potential impacts on ecosystems, and explore effective management and control strategies. Despite a wealth of research focused on lake water, the variations in microplastics with offshore distance and their vertical distribution within the water column are not well understood. Here, we investigated the freshwater continuum from the inlet of Taihu Lake to the centre, and vertically from the surface to the bottom water. The results revealed that the distribution of microplastics (<5 mm in size) exhibited a clear spatial gradient. The microplastic abundance at the lake entrance was 2.12 times greater than that at the centre, and on the lake surface, the microplastic abundance was 1.36-1.69 times higher than that estimated from the water column. Notably, the proportion of small-sized microplastics (<0.1 mm) in the bottom water was 1.72 times higher than that in the surface water. The main types of polymers identified were polyamide (PA) and polyvinyl chloride (PVC), and their main sources may be from clothes washing and industrial activities. The Monte Carlo simulation results indicated that the overall risk of microplastics in surface water was higher than that in the water column, and the contributions of PVC and polyurethane (PU) to the ecological risk were 90.10% and 9.57%, respectively. Therefore, PVC and PU should be the priority of microplastic pollution control. This study provides the first comprehensive evaluation of the spatial ecological risk of microplastics in Taihu Lake, which improves our understanding of the distribution and environmental risks of microplastics in lake systems.

Occurrence and characteristics of microplastics across the watershed of the world's third-largest river

While rivers as primary conduits for land-based plastic particles transferring to their "ultimate" destination, the ocean, have garnered increasing attention, research on microplastic pollution at the scale of whole large river basins remains limited. Here we conducted a large-scale investigation of microplastic contamination in water and sediment of the world's third-largest river, the Yangtze River. We found concentrations of microplastics in water and sediment to be 5.13 items/L and 113.9 items/kg (dry weight), respectively. Moreover, microplastic pollution levels exhibited a clear decreasing trend from upstream to downstream. The detected microplastics were predominantly transparent in color, with fibrous shapes predominating, sizes mainly concentrated below 1 mm and composed primarily of PP and PE polymers. Our analysis results indicated that compared to geographical and water quality parameters, anthropogenic factors primarily determined the spatial distribution pattern of microplastics. Moreover, the microplastic abundance in sediment upstream of the dam was significantly higher than that in the downstream sediment, while the trend of microplastic concentrations in water was opposite. Therefore, more effort is needed to monitor microplastic contamination and their ecological environmental effects of sediment before dams in future research.

Global patterns of lake microplastic pollution: Insights from regional human development levels

Microplastics have emerged as a pervasive pollutant across various environmental media. Nevertheless, our understanding of their occurrence, sources, and drivers in global lakes still needs to be completed due to limited data. This study compiled data from 117 studies (2016-May 2024) on microplastic contamination in lake surface water and sediment, encompassing surface water samples in 351 lakes and lake sediment samples in 200 lakes across 43 countries. Using meta-analysis and statistical methods, the study reveals significant regional variability in microplastic pollution, with concentrations ranging from 0.09 to 130,000 items/m3 in surface water and from 5.41 to 18,100 items/kg in sediment. Most microplastics were under 1 mm in particle size, accounting for approximately 79 % of lake surface water and 76 % of sediment. Transparent and blue microplastics were the most common, constituting 34 % and 21 % of lake surface water and 28 % and 18 % of sediment, respectively. Fibers were the dominant shape, representing 47 % of lake surface water and 48 % of sediment. The primary identified polymer types were polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET). Countries like India, Pakistan, and China had higher contamination levels. Positive correlations were found between microplastic abundance in surface water and factors like human footprint index (r = 0.29, p < 0.01), precipitation (r = 0.21, p < 0.05), and net surface solar radiation (r = 0.43, p < 0.001). In contrast, negative correlations were observed with the human development index (r = -0.61, p < 0.01) and wind speed (r = -0.42, p < 0.001). In sediment, microplastics abundance correlated positively with the human footprint index (r = 0.45, p < 0.001). This study underscores the variability in microplastic pollution in global lakes and the role of human activities and environmental factors, offering a valuable reference for future research.

Detection of small microplastics in the surface freshwater samples of Yangcheng Lake, China

Microplastics up to 20 μm are recognized as having the highest potential to cause significant impacts on aquatic environments. Current methods face challenges in detecting and chemically characterizing small microplastics in freshwater systems. In this study, using an optical confocal micro-Raman tweezer technique, the composition of particles trapped in lake aggregates collected from surface water around Yangcheng Lake in Suzhou, China, has been identified. Surface freshwater samples were analyzed from 15 different sites around the lake. In total, 514 particles were analyzed of which 136 were small microplastics. Chemical characterization showed the presence of five different polymer types, with polystyrene being the most dominant, accounting for 63% of the detected particles. Small plastics in the range of 1.1 to 8.5 μm were detected around crab restaurants and residential villages. The smallest microplastics identified were 1.1 μm polystyrene. Fragment was the most common shape of microplastics, followed by fiber and quasisphere within the volume of sample analyzed. The results suggest that the primary sources of small microplastic contamination in Yangcheng Lake may include fishing activities, agriculture, and tourism. Study findings may be used as a reference to extend the understanding of the small microplastic contamination level in inland freshwater systems.

Effects of soil properties and land use patterns on the distribution of microplastics: A case study in southwest China

Microplastic pollution in the soil environment is of great concern. However, the current research on microplastics (MPs) in Southwest China mainly focuses on their distribution characteristics and sources in soil, making the understanding of the soil properties and land use patterns influencing soil MPs insufficient. In this study, the abundance and distribution characteristics of MPs in the soil of different land use patterns in Guizhou Province were determined. The results revealed that the average abundance of MPs in soils was 2936 items/kg, ranging from 780 to 9420 items/kg. The MPs were mainly small particle size (0-0.5 mm), granular, and black, accounting for 87.5%, 36.6%, and 82.2%, respectively. The most common polymer types of MPs were polypropylene, polyethylene terephthalate, and polyethylene, which accounted for 20.4%, 16.8%, and 16.4%, respectively. As soil bulk density increased, microplastic abundance and small particle size decreased. Soil microplastic abundance slightly decreased with increasing soil porosity. The abundance of MPs increased with the increase in soil pH, but no significant correlation was observed between soil organic matter content and microplastic abundance. pH was the major factor that affected the microplastic distribution, which accounted for 32.5%. This study provides insight into the distribution and influencing factors of soil MPs and also provides a theoretical basis for subsequent research on soil microplastic pollution.