ABSTRACT
Wastewater treatment plants (WWTPs) have been proposed as significant sources of microplastics (MPs) in freshwater and estuarine environments. WWTPs, even those with high removal efficiencies, release millions of MPs per plant daily. China is the largest plastic producer worldwide, but only a few studies of MP pollution from WWTPs have been carried out in China. In this work, we present a comprehensive report concerning the MPs in effluent from six WWTPs in Guangzhou, which is the third largest city in China. The six WWTPs employ different treatment processes and serve different populations and types of factories. The average abundance of MPs in the effluents of all six WWTPs was 1.719 ± 1.035 MP/L. Fiber was the most common type of MP in the effluent, accounting for 39.48 ± 6.37% of all MPs. Fourier transform infrared spectroscopy confirmed that 35.7% of the particles were plastics, including polyethylene terephthalate (31.9%), polypropylene (26.6%), and polyethylene (9.7%). The results showed that advanced or tertiary treatment technologies could substantially remove MPs and that the size of the population served was positively associated with the abundance of MPs. The number of textile factories was a key factor contributing to the total release of MPs. In addition, the MP shapes and polymer compositions showed that the occurrence of MP types is regional, varies regionally, and is related to the types of factories in the vicinity. More studies on the effects of specific industries are suggested in order to improve the management of wastewater discharge and reduce MPs presence in the natural environment.
Subject(s)
Water Pollutants, Chemical , Water Purification , China , Cities , Environmental Monitoring , Microplastics , Plastics , Waste Disposal, Fluid , Wastewater , Water Pollutants, Chemical/analysisABSTRACT
To explore the effect of heterotrophic nitrification-aerobic denitrification mixed strains on urea removal, the removal characteristics of urea and effects of heavy metals and salinity on urea removal by mixed strains (DM01+YH01+YH02) were investigated. The results showed that urea could be efficiently degraded by mixed strains at 24 h in 200.0 mg·L-1 urea wastewater when the carbon source was sodium citrate, C/N was 10, temperature was 30â, pH was 7, and rotation speed was 130 r·min-1. Heavy metal ions (Ni2+, Cd2+, Cu2+, and Zn2+) can reduce the removal efficiency of urea by mixed strains, and the degree of influence was Cd2+ > Cu2+ > Ni2+ > Zn2+. Fe2+ (<20.0 mg·L-1) in urea wastewater can enhance the removal efficiency of urea by mixed strains. Furthermore, a salinity of more than 10.0 mg·L-1 in urea wastewater can reduce the removal efficiency of urea by mixed strains.
ABSTRACT
Optic Atrophy 1 (OPA1) has well-established roles in both mitochondrial fusion and apoptotic crista remodeling and is required for the maintenance and distribution of mitochondrial DNA (mtDNA), which are essential for energy metabolism. However, the relationship between OPA1 and mitochondrial metabolism and the underlying mechanisms remain unclear. Here, we show that OPA1-Exon4b modulates mitochondrial respiration and rescues inner mitochondrial membrane potential (Δψm), independent of mitochondrial fusion. OPA1-Exon4b is required for the maintenance of normal TFAM distribution and enhances mtDNA transcription by binding the D-loop of mtDNA. Finally, we show that mRNA levels of OPA1 isoforms containing Exon4b are specifically downregulated in hepatocellular carcinoma (HCC), leading to a reduction in Δψm. Thus, our study demonstrates a novel mitochondrial functional self-recovery pathway involving enhanced mtDNA transcription-mediated recovery of mitochondrial respiratory chain proteins. This mitochondrial fusion-independent pathway may contribute to mitochondrial multi-functional switches in tumorigenesis.
