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Urban parks play an important role in the urban residents' daily leisure life, the provision of satisfying and sufficient leisure services are the urgent tasks of urban government and urban park management department. However, there are few literatures that focus on this topic in the domestic and international academic circles. Based on the background of 32 municipal parks free opening in Guangzhou in 2009, the authors carried out an random sampling questionnaire survey on the residents' perception of urban park free opening policy in the 5 typical urban parks. Using quantitative methods such as factor analysis, variance analysis, this research found that: 1. nearly half of the respondents hold a positive attitude toward park free open-door policy while one-third of respondents are opposed to the park free open policy. 2. Using factor analysis to study the positive and negative perception of the urban park free open policy, this study found three positive common factors and four negative common factors. 3. Using the variance method to test the significance of the common factors, the study found that different ages and occupational groups are different on the factors: "enrich our leisure life", "promote the development of leisure and tourism", "raising the price of the commodities and entertainment facilities", "degenerate the environment of the parks and recreation". Finally, this paper puts forward some suggestions to improve park management policies according to the problems and the above study. [ABSTRACT FROM AUTHOR]

Prior investigations on the associations of polyfluoroalkyl substances (PFASs) with fetal growth are mixed. Moreover, little research has accrued pertaining to the association between isomers of PFASs with gestational age and birth weight. To address this gap and present novel information, we conducted a study including 321 pairs of mothers and their infants recruited from Guangzhou, China. High performance liquid chromatography-mass spectrometry was utilized to analyze isomers of perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA) along with other PFAS levels in cord serum samples. Mothers' and infants' characteristics were gathered from medical records. The resulting data revealed that higher PFOS, PFOA and isomers of PFOS were associated with lower birth weight. Per ln-unit (ng/mL) increase in cord serum total branched PFOS isomers was associated with a 126.3 g (95% CI: − 195.9, − 56.8) reduction in the weight of infants at birth, while an ln-unit (ng/mL) increase of serum linear PFOS isomers ( n -PFOS) was associated with a 57.2 g (95% CI: − 103.1, − 11.3) reduction in the weight of infants at birth upon the subsequent adjustment for potential confounding variables. Notably, the association between cord PFAS level and birth weight was more pronounced in male infants. Furthermore, a positive association among branched PFOS isomers (1m-PFOS and 3 + 4 + 5m-PFOS) and gestational age was found. No associations could be found among other PFASs in conjunction with gestational age or birth weight. In conclusion, this investigation suggests that higher PFAS concentrations are associated with lower birth weight, and branched PFOS isomers show greater impact on infant birth weight than linear PFOS. [ABSTRACT FROM AUTHOR]