ABSTRACT
Rain-source urban rivers have the characteristics of small water capacityï¼ lack of dynamic water supplyï¼ and being easily polluted. This study analyzed the spatial and temporal distribution characteristics of river water quality and the response of characteristic pollutants to rainfall based on daily rainfall data and 21 water quality indicators of nine major river basins in Shenzhen ï¼excluding Shenzhen-Shantouï¼ from 2015 to 2021 by using the single-factor assessment methodï¼ comprehensive pollution index methodï¼ hierarchical cluster analysisï¼ and Pearson correlation. The results showed thatï¼ â in 2015ï¼ the water quality of most sections in the whole region was inferior Class V water. After October 2018ï¼ the overall water quality of rivers was greatly improvedï¼ which was consistent with the background of Shenzhen's special water control activities in 2018. By 2021ï¼ the water quality of approximately 62% of sections reached Class â -â ¢ water standards. â¡ The water pollution in the densely populated western part of Shenzhen was more serious than that in the eastern partï¼ and the water pollution in the lower reaches of the estuaries and tributaries was more serious than that in the upper reaches. ⢠The water quality of the Pingshan Riverï¼ Guanlan Riverï¼ Longgang Riverï¼ and Maozhou River was significantly affected by rainfall. ⣠The main characteristic pollution indexes of the Shenzhen River were DOï¼ permanganate indexï¼ CODï¼ BOD5ï¼ NH4+-Nï¼ TPï¼ petroleumï¼ and anionic surfactant. For the Pingshan River and Longgang Riverï¼ rainfall increased the concentrations of TP and NH4+-N. For the Maozhou Riverï¼ rainfall increased the concentrations of TP and COD. For the Shenzhen Riverï¼ rainfall increased the concentrations of CODï¼ TPï¼ and NH4+-N. The above results reveal the spatio-temporal variation in rain-source river water quality in Shenzhen and its response to non-point source pollution caused by rainfall events and provide a scientific reference for building a higher quality water environment in Shenzhen.
ABSTRACT
Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) with selective reaction monitoring (SRM) is a selective and sensitive method for quantitation of peptides. SRM is achieved via MS/MS utilizing collision-induced dissociation (CID) while monitoring unique precursor-product ion transitions. Low-energy CID tandem mass spectrometry has been, by far, the most common method used to dissociate peptide ions for sequence analysis. However, collisional scattering of product ions in CID results in decreased intensity of the primary product ion. The lower intensity of the targeted product ion can lead to a reduction in the sensitivity of a quantitative method that uses SRM. Electron transfer dissociation (ETD) is a fragmentation method that is complementary to CID. During the ETD reaction for doubly protonated peptides ([M+2H](2+)), there is a significant shift toward nondissociative electron transfer (ET) product species ([M+2H](+)). We utilized that particular defect in ETD to develop a new quantitative method for monitoring the transition of unique precursors ([M+2H](2+)) to charge-reduced ions ([M+2H](+)). We refer to this method as selective electron transfer reaction monitoring (SETRM). In ESI-MS, trypsin-digested peptides tend to generate doubly protonated peptide precursors. We found that SETRM was more suitable than SRM for these doubly charged tryptic peptides with nano-LC-MS/MS. The quantitative capabilities of SETRM provide a more sensitive way of performing quantitative experiments using the same instrument, thereby improving the application of electron transfer dissociation in proteomics.
