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
OBJECTIVES: Our purpose was to assess the feasibility, safety, and effectiveness of a modified predilation for middle cerebral artery (MCA) stenosis. BACKGROUND: Wingspan stenting of MCA remains a technical challenge, and rates of residual stenosis and restenosis must be lowered. METHODS: A series of 48 patients with symptomatic MCA stenosis greater than 50% and refractory to medical therapy underwent Wingspan stenting with different balloon/artery ratios before (group 1, Boston guidelines predilation) or after (group 2, modified predilation) July of 2008. Technical success, periprocedural complications, recurrent symptoms, and restenosis were assessed retrospectively, and risk factors for restenosis were analyzed using logistic regression. RESULTS: Successful stenting occurred in 48 of 49 (98%) lesions. Primary endpoints within 30 days included one (2.12%) minor stroke and two (4.26%) transient ischemic attacks. Stenoses were reduced from 77.11% ± 10.09% to 27.50% ± 6.91% in group 1 versus from 72.56% ± 10.46% to 8.20% ± 5.41% in group 2. A total of 43 patients were followed up for 12.92 ± 5.08 months, and recurrent stroke or transient ischemic attack occurred in two (4.65%) patients. Vessels were followed with transcranial Doppler (43 vessels), angiography (23 vessels), or computed tomographic angiography (one vessel). The restenosis rate was 8 of 18 (44%) in group 1 and 3 of 25 (12%) in group 2. Restenosis was associated with residual stenosis and diabetes. CONCLUSIONS: Wingspan stenting for symptomatic MCA stenosis can be performed with high success and low complication rates, and modified predilation with the Gateway balloon can reduce the rates of residual stenosis and restenosis.
