Microplastic pollution in the environment has received growing attention worldwide. A major impediment for accurate measurements of microplastics in environmental matrixes is to extract the ...particles. The most commonly-used method for separation from soil or sediment is flotation in dense liquid based on the relatively low density of plastic particles. This study provides an improved and optimized process for extraction of microplastic particles by modifying the floatation technique and floatation solution. Microplastics in soils and sediments are extracted by adding 200 g dry soil or sediment sample to 1.3 L mix of the saturated NaCl and NaI solutions in a volume ratio of 1:1 and aerating for 40 s then filtering the supernatant. The accuracy and precision of the new approach is validated by recovery experiments using soil and sediment samples spiked with six common microplastic compounds: polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) and expanded polystyrene (EPS), and comparison with the previous method. The optimized approach is further compared with the previous approach using the real soil and sediment samples.
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•An optimized approach for extracting microplastics was proposed.•The mixture of NaCl and NaI was used as floatation solution.•Aeration was used instead of stirring by hand.•The optimization was validated by spiking and comparison experiments.
Soil microplastic pollution has caused widespread research attention worldwide. It is necessary to efficiently separate microplastic particles from soil matrixes in order to conduct studies of ...microplastic. And so far, few studies have described the separation and extraction devices of biodegradable microplastic. Here we present a commonly available device for extraction of non-degradable and biodegradable microplastics from soil samples in a NaBr solution based on density flotation. The device has a combined circulation and recovery system for the salt solution, which increases its environmental-friendliness. The accuracy and precision of the device was verified through spike and recovery experiments using three types of biodegradable microplastics (PBS, PBAT, PLA) and four types of non-degradable microplastics (LDPE, PS, PP, PVC), all with different particle sizes, and all microplastics are grinded autonomously, closer to reality. In despite of differences in particle size and density, for both biodegradable and non-degradable microplastics the device exhibited good extraction precision, with recovery rates ranging from 92% to 99.6%, over a wide range of particle densities and sizes. The recovery rates slightly increased with increased polymer density and microplastic particle size.
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•A commonly available device for extraction of microplastics from soil was proposed.•The NaBr of reusable and environmentally friendly was used as flotation solution.•The performance of the device was verified through spike and recovery experiments.•Self-grinding biodegradable and non-degradable microplastics were used.
Background: Fish consumption is considered the primary pathway of methylmercury (MeHg) exposure for most people in the world. However, in the inland regions of China, most of the residents eat little ...fish, but they live in areas where a significant amount of mercury (Hg) is present in the environment. Objectives: We assessed concentrations of total Hg and MeHg in samples of water, air, agricultural products, and other exposure media to determine the main exposure pathway of Hg in populations in inland China. Methods: We selected Guizhou Province for our study because it is highly contaminated with Hg and therefore is representative of other Hg-contaminated areas in China. We selected four study locations in Guizhou Province: three that represent typical environments with severe Hg pollution due to Hg mining and smelting (Wanshan), traditional zinc smelting (recently closed; Weining), and heavy coal-based industry (Qingzhen), and a village in a remote nature reserve (Leigong). Results: The probable daily intake (PDI) of MeHg for an adult population based on 60 kg body weight (bw) was considerably higher in Wanshan than in the other three locations. With an average PDI of 0.096 μg/kg bw/day (range, 0.015—0.45 μg/kg bw/day), approximately 34% of the inhabitants in Wanshan exceeded the reference dose of 0.1 μg/kg bw/day established by the U.S. Environmental Protection Agency. The PDI of MeHg for residents in the three other locations were all well below 0.1 μg/kg bw/day (averages from 0.017 to 0.023 μg/kg bw/day, with a maximum of 0.095 μg/kg bw/day). In all four areas, rice consumption accounted for 94—96% of the PDI of MeHg. Conclusion: We found that rice consumption is by far the most important MeHg exposure route; however, most of the residents (except those in Hg-mining areas) have low PDIs of MeHg.
•Biochar increased the pH and released dissolved organic matter from the soil.•Biochar sorbed more small aliphatic than large aromatic dissolved organic molecules.•A size exclusion effect in ...biochar’s micropores could explain the sorption pattern.
Amendments of biochar, a product of pyrolysis of biomass, have been shown to increase fertility of acidic soils by enhancing soil properties such as pH, cation-exchange-capacity and water-holding-capacity. These parameters are important in the context of natural organic matter contained in soils, of which dissolved organic matter (DOM) is the mobile and most bioavailable fraction. The effect of biochar on the content and composition of DOM in soils has received little research attention. This study focuses on the effects of amendments of two different biochars to an acidic acrisol and a pH-neutral brown soil. A batch experiment showed that mixing biochar with the acrisols at a 10wt.% dose increased the pH from 4.9 to 8.7, and this resulted in a 15-fold increase in the dissolved organic carbon concentration (from 4.5 to 69mgL−1). The pH-increase followed the same trend as the release of DOM in the experiment, causing higher DOM solubility and desorption of DOM from mineral sites. The binding to biochar of several well-characterised reference DOM materials was also investigated and results showed a higher sorption of aliphatic DOM to biochar than aromatic DOM, with DOM-water partitioning coefficients (Kd-values) ranging from 0.2 to 590Lkg−1. A size exclusion occurring in biochar’s micropores, could result in a higher sorption of smaller aliphatic DOM molecules than larger aromatic ones. These findings indicate that biochar could increase the leaching of DOM from soil, as well as change the DOM composition towards molecules with a larger size and higher aromaticity.
The production of odorant 2-methylisoborneol (MIB) in water bodies by Planktothrix sp. have not been understood very well. Through a four-year investigation in Miyun Reservoir, a huge mesotrophic ...drinking water reservoir known to have the MIB episodes, we found that the Planktothrix sp. bloomed during September and October causing the high levels of MIB in the reservoir. The concentration of MIB and the biomass of MIB-producing cyanobacteria Planktothrix were measured (n = 887) at different sites and depths during different seasons. The results indicated that the shallow region of the reservoir is the major habitat for Planktothrix sp. due to that the light is able to penetrate down to the relatively high concentrations of nutrients close to the sediments. Quantile regression analysis between Planktothrix biomass and MIB concentration shows that the risk of MIB exceeding the odor threshold (15 ng L−1) in water was as high as 90% when the Planktothrix density was more than 4.0×105 cells L−1, while the risk was reduced to 10% when the Planktothrix density remained below 1.6×104 cells L−1. This study will improve the understanding of the environmental behaviors of Planktothrix sp., and can provide useful information for better management of drinking water lakes/reservoirs experiencing the taste and odor (T&O) problems caused by deep living cyanobacterial species.
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•Water level lowering triggered the deep living cyanobacteria bloom in Miyun Reservoir.•The shallow areas in Miyun Reservoir are the major habitats for Planktothrix sp.•The Planktothrix could bloom in mesotrophic water due to its low light requirement.
Browning of Fennoscandian boreal lakes is raising concerns for negative ecosystem impacts as well as reduced drinking water quality. Declined sulfur deposition and warmer climate, along with ...afforestation, other climate impacts and less outfield grazing, have resulted in increased fluxes of Total Organic Carbon (TOC) from catchments to freshwater, and subsequently to coastal waters. This study assesses the major governing factors for increased TOC levels among several catchment characteristics in almost 5000 Fennoscandian lakes and catchments.
Normalized Difference Vegetation Index (NDVI), a proxy for plant biomass, and the proportions of peatland in the catchment, along with surface runoff intensity and nitrogen deposition loading, were identified as the main spatial predictors for lake TOC concentrations. A multiple linear model, based on these explanatory variables, was used to simulate future TOC concentration in surface runoff from coastal drainage basins in 2050 and 2100, using the forecasts of climatic variables in two of the Shared Socio-economic Pathways (SSP): 1-2.6 (+2 °C) and 3-7.0 (+4,5 °C). These scenarios yield contrasting effects. SSP 1-2.6 predicts an overall decrease of TOC export to coastal waters, while SSP 3-7.0 in contrast leads to an increase in TOC export.
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•TOC concentration in boreal lakes depends on catchment characteristics, in particular on standing biomass.•A space-for-time approach proves successful to predict future TOC concentration.•Climate change > 4.5°C will lead to a strong increase in browning of freshwater and export of TOC to coastal waters.
Spatiotemporal distribution and ecological risk of the polyethylene terephthalate (PET) plastic polymer and plasticizer di-(2-ethylhexyl) phthalate (DEHP) were investigated using both surface and ...core sediments in Jiaozhou Bay, China. The concentrations of PET and DEHP ranged 210.6–1929.7 μg/kg and 0–591.2 μg/kg, respectively. The depth profiles of PET and DEHP in the sediment cores indicated that PET and DEHP pollution increased since the 1970s, which is in accord with the regional PET and DEHP consumption history. The levels of PET in Jiaozhou Bay was found to represent low ecological risk based on the assessment models for Potential Ecological Risk factor and Potential Ecological Risk. The amounts of DEHP also posed a low risk to the aquatic organisms in the sediment phase as indicated by the Risk Quotient method.
•PET and DEHP concentrations in the surface sediments were between 210.6–19,297.7 and 0–591.2 μg/kg, respectively.•PET and DEHP loading to the sediments increased rapidly with anthropogenic activities since the 1970s.•PET and DEHP in the sediments pose a low ecological risk.•The mass concentration of PET in the bay sediment was firstly reported.
Environmental effects of microplastic are rather due to their adsorption capacity of contaminants than themselves. Aging is a key factor influencing adsorption properties of environmental ...microplastics. In order to clarify this influence, polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) microplastics with particle sizes of <0.9 mm, 0.9–2 mm, and 2–5 mm were artificially aged in seawater for 12 months. This enabled an assessment of the change in Cu(II) adsorption capacity to the microplastics particles under aging. According to the FTIR spectra, fresh microplastics were oxidized during the UV induced aging process. The adsorption capacities of microplastic were positively correlated with their aging time. After 12-months aging, the amount of Cu(II) adsorbed to the aged microplastics was 1.45–2.92 times higher than on the fresh microplastic particles. For PP and PET, the aging effect increased with decreasing size of the microplastic particles. In the case of PE, particles with the medium particle size (0.9–2 mm) had the strongest aging effect.
The Tibetan Plateau covers an area of about one fourth of Europe, has an average elevation over 4000
m above sea level, and is the water sources for about 40% of world's population. In order to ...foresee future changes in water quality, it is important to understand what pressures are governing the spatial variation in water chemistry. In this paper the chemistry including major ions and trace elements in the headwaters of four major Asian rivers (i.e. the Salween, Mekong, Yangtze River and Yarlung Tsangpo) in the Tibetan Plateau was studied. The results showed that the content of dissolved salts in these Tibetan rivers was relatively high compared to waters from other parts of the world. The chemical composition of the four rivers were rather similar, with Ca
2+ and HCO
3
− being the dominating ions. The exception was the Yangtze River on the Plateau, which was enriched in Na
+, Cl
−, SO
4
2− and Li due to silicate weathering followed by strong evaporation caused by a negative water balance, dissolution of evaporites in the catchment and some drainage from saline lakes. The concentrations of heavy metals (Cu, Co, Cr, Ni, Cd, Pb, and Hg) and As, NH
4
+ were generally low in all the rivers. Anthropogenic impacts on the quality of the rivers were identified at a few locations in the Mekong River and Yarlung Tsangpo basins. Generally, the main spatial variation in chemical compositions of these under studied rivers was found to be governed mainly by difference in geological variation and regional climatic-environment. Climate change is, therefore, one of main determining factors on the water chemical characteristics of these headwaters of Asian major rivers in the Tibetan Plateau.
Bohai Bay, a typical semi-enclosed bay, is close to the Beijing-Tianjin-Hebei Region, the economic center of north China. The release of emerging contaminants was considerably increasing with the ...fast urbanization and industrialization along the coastline. However, such data, e.g. plastic polymers, are still limited. Here, polyethylene terephthalate (PET) and di-(2-ethylhexyl) phthalate (DEHP) in surface sediments and sediment cores from the coastal area of Bohai Bay were investigated. The ranges of PET and DEHP concentrations in surface sediments are 1.49–13.90 mg/kg and 0.23–19.26 mg/kg, respectively. The relatively high contents of PET and DEHP were found near the Haihe River estuary, indicating the importance of riverine input. The PET and DEHP profiles in the cores dated by the 210Pb method showed increasing trends with time. The PET in Bohai Bay was low risk evaluated by the potential ecological risk assessment. Low ecological risks of DEHP to the benthic organisms were found in the sediments, using the environmental risk limits, risk quotient, threshold effect level and probable effect level methods. The pollution levels of PET and DEHP in Bohai Bay obtained in this study may provide important data for making pollution control strategies.
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•PET and DEHP were 1.49–13.90 and 0.23–19.26 mg/kg, respectively, in Bohai Bay.•PET and DEHP increased rapidly since the 1980s.•PET and DEHP pose a low ecological risk to the aquatic ecosystem.
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