Quantitative evaluation of urban green exposure and its impact on human health: A case study on the 3-30-300 green space rule.

BACKGROUND AND AIMS: Urban green spaces offer various health benefits, yet the impact of comprehensive green exposure criteria on multidimensional health remains unclear. The 3-30-300 green space rule represents the green exposure indicators with specific thresholds. This study aims to quantitatively evaluate urban green exposure in cities and can support investigation of its relationship with human health. METHODS: We conducted a cross-sectional study based on 902 investigated individuals in 261 residential locations aged 11-95 years from Xiamen City, China. 3-30-300 green exposure was calculated using field surveys, GIS, and Baidu Maps Application Programming Interface (API). Physical health data was based on Occupational Stress Indicator (OSI)-2. Mental health was from the 12-item General Health Questionnaire (GHQ-12). Social health was from a self-constructed evaluation questionnaire. Statistical analyses were conducted using Geographically Weighted Regression and Geographically Weighted Logistic Regression for global and local effects on green exposure and multidimensional health. RESULT: Among the investigated individuals, only 3.55 % (32/902) fully meet the 3-30-300 rule in Xiamen. Global results show that individuals achieved at least 30 % vegetation coverage (Yes) is associated with better physical (ß: 0.76, p < 0.01) and social (ß: 0.5, p < 0.01) health. GWLR global results indicate that individuals can "see at least 3 trees from home" meeting one (OR = 0.46, 95%CI: 0.25-0.86, p < 0.05) or two (OR = 0.41, 95%CI: 0.22,0.78, p < 0.01; OR = 0.24, 95%CI: 0.07-0.77, p < 0.05) 3-30-300 rule components are significantly associated with reduced medical visits and hospitalizations refer to not met these criterias. In the GWR local analysis, achieved 30 % vegetation cover is significantly related to improved social health at all locations. Meeting any two indicators also contribute to improved social health (n = 511, ß: 0.46-0.51, P < 0.05). CONCLUSION: Green exposure indicators based on the 3-30-300 rule guiding healthy urban green space development. We observed multidimensional health benefits when 1/3 or 2/3 of the indicators were met.

Removal and recovery of phosphorus from secondary effluent using layered double hydroxide-biochar composites.

Removal of phosphorus (P) from wastewater and its recovery as a fertilizer are solutions to both P pollution control and resource recycling for agriculture. In this study, various layered double hydroxide biochar composites (LDH/BCs), namely, Zn-Al-LDH/BC, Mg-Al-LDH/BC, and Mg-Fe-LDH/BC, were synthesized to remove P from secondary effluents and then applied as fertilizers. Batch experiments showed that LDH/BCs could adsorb P in fast kinetics, with adsorption capacities ranging 35.19-55.76 mg P/g. A dynamic experiment was performed under different column heights and flow rates, and the results fitted well with Thomas model (R2 > 0.90). These LDH/BCs effectively removed P in the continuous mode, even when treating secondary effluents. Furthermore, when the used LDH/BCs applied as fertilizers, the adsorbed Mg-Al-LDH/BC and Mg-Fe-LDH/BC stimulated crop growth; however, Zn-Al-LDH/BC did not. These differences were attributed to not only the availability of P, but also the stimulation or inhibition of photosynthetic pigment synthesis in crops by adsorbents. Overall, we synthesized LDH/BCs, which effectively removed and recovered P from secondary effluents, and investigated the factors influencing the effects of LDH/BCs on crops. We suggest that both P availability and physiological influences of adsorbents on crops should be considered when using adsorbents as fertilizers.

Impacts of carbon-based nanomaterials on nutrient removal in constructed wetlands: Microbial community structure, enzyme activities, and metabolism process.

The increasing use of raw carbon-based nanomaterials (CBNs) will inevitably affect wastewater treatment systems. Constructed wetlands (CWs) are ecological wastewater treatment facilities and can intercept the vast particles pollutant, including CBNs. However, the impacts of CBNs on the treatment performance of CWs have no available knowledge. Therefore, we systematically inspected the effects of single-walled and multi-walled carbon nanotubes (SWCNTs and MWCNTs) and fullerene nanoparticles (C60) on CW performance under 180-day exposure to 0, 10 and 1000 µg/L concentrations. The results showed that CBNs had marginally adverse impacts on chemical oxygen demand (COD) and total phosphorus (TP) removal, whereas nitrogen removal declined by 24.1 %-42.7 % following long-term exposure to CBNs. MWCNTs had the greatest inhibition effect on nitrogen removal, followed by SWCNTs and C60. The CBNs also induced reactive oxygen species (ROS) overproduction as the increasing concentration, which confirmed that CBNs have biotoxic effects in CWs. The variation of functional microbial community and the inhibition of enzyme activities were the dominant reasons for the decline in nitrogen removal efficiency. Furthermore, predictive functional profiling showed that CBNs affected functional gene abundance, and caused a decline in the enzymes abundance connected to nitrogen removal by the end of the 180-day exposure period.

Nanoplastics Disturb Nitrogen Removal in Constructed Wetlands: Responses of Microbes and Macrophytes.

Nanosized plastics (nanoplastics) releasing into the wastewater may pose a potential threat to biological nitrogen removal. Constructed wetland (CW), a wastewater treatment or shore buffer system, is an important sink of nanoplastics, while it is unclear how nitrogen removal in CWs occurs in response to nanoplastics. Here, we investigated the effects of polystyrene (PS) nanoplastics (0, 10, and 1000 µg/L) on nitrogen removal for 180 days in CWs. The results revealed that total nitrogen removal efficiency decreased by 29.5-40.6%. We found that PS penetrated the cell membrane and destroyed both membrane integrity and reactive oxygen species balance. Furthermore, PS inhibited microbial activity in vivo, including enzyme (ammonia monooxygenase, nitrate reductase, and nitrite reductase) activities and electron transport system activity (ETSA). These adverse effects, accompanied by a decline in the relative abundance of nitrifiers (e.g., Nitrosomonas and Nitrospira) and denitrifiers (e.g., Thauera and Zoogloea), directly accounted for the strong deterioration observed in nitrogen removal. The decline in leaf and root activities decreased nitrogen uptake by plants, which is an important factor of deterioration in nitrogen removal. Overall, our results imply that the presence of nanoplastics in the aquatic environment is a hidden danger to the global nitrogen cycle and should receive more attention.

[Spatiotemporal variability characteristics and driving forces of land use in the Pan-Pearl River Basin, China]. / æ³›ç æ±ŸæµåŸŸåœŸåœ°åˆ©ç”¨æ—¶ç©ºå˜åŒ–ç‰¹å¾åŠé©±åŠ¨å› å­.

The Pan-Pearl River Basin is a bridgehead for China's reform and opening-up and the construction of the Belt and Road at Sea, with vital strategic significance in Chinese overall development. Land use data and climate and socio-economic indicators were integrated to probe the spatiotemporal change and its driving forces of land use in the Pan-Pearl River basin with ArcGIS spatial analysis tool and SPSS factor analysis tool. Results showed that land use in the Pan-Pearl River Basin significantly changed between 1990 and 2015, with decreases of the area of paddy field and woodland and rapid increases of urban land and other construction land. Outflow of grassland occurred in the northwestern part of the basin. Reduction of cultivated field was mainly concentrated in the central part of the basin and coastal areas. Increases in urban and rural land, industrial and mining land, and residential land were centrally distributed in the Guangdong-Hong Kong-Marco Greater Bay Area. The prominent change areas were Guangdong-Hong Kong-Marco Greater Bay Area : central and southeast of Guangxi Province : northern Hainan Province. Land use changes during 1990-2000 were most obvious in the basin. The main driving factor of spatiotemporal variation of land use was the rapid development of social economy and industry and the improvement of residents' consumption level.

Impact of biochar on greenhouse gas emissions from constructed wetlands under various influent chemical oxygen demand to nitrogen ratios.

Biochar is widely used for nutrient removal in constructed wetlands (CWs); however, its influence on greenhouse gas (GHG) emissions from CWs remains unclear. Here, biochar was used to mitigate the global warming potential (GWP) from CWs and promote the removal of contaminants from simulated domestic wastewater under different influent chemical oxygen demand to nitrogen ratios (COD/N = 3, 6, 9, 12). Results demonstrated that biochar could improve the removal of COD, NH4+- N, and TN. The average N2O and CO2 fluxes were significantly lower and CH4 fluxes were higher in biochar-added CWs than those in none-biochar CWs. Biochar reduced GWP values of N2O and CH4 from 18.5% to 24.0%. N2O fluxes and GWP decreased, while CH4 and CO2 fluxes increased as COD/N ratios increased. Additionally, biochar increased the abundance of Geobacter and denitrifiers such as Hydrogenophaga. Overall, biochar could not only promote the removal of nutrients but also mitigate GWP in CWs.

Global nitrogen input on wetland ecosystem: The driving mechanism of soil labile carbon and nitrogen on greenhouse gas emissions.

Greenhouse gas emissions from wetlands are significantly promoted by global nitrogen input for changing the rate of soil carbon and nitrogen cycling, and are substantially affected by soil labile carbon and nitrogen conversely. However, the driving mechanism by which soil labile carbon and nitrogen affect greenhouse gas emissions from wetland ecosystems under global nitrogen input is not well understood. Working out the driving factor of nitrogen input on greenhouse gas emissions from wetlands is critical to reducing global warming from nitrogen input. Thus, we synthesized 72 published studies (2144 paired observations) of greenhouse gas fluxes and soil labile compounds of carbon and nitrogen (ammonium, nitrate, dissolved organic carbon, soil microbial biomass nitrogen and carbon), to understand the effects of labile carbon and nitrogen on greenhouse gas emissions under global nitrogen input. Across the data set, nitrogen input significantly promoted carbon dioxide, methane and nitrous oxide emissions from wetlands. In particular, at lower nitrogen rates (<100 kg ha-1·yr-1) and with added ammonium compounds, freshwater wetland significantly promoted carbon dioxide and methane emissions. Peatland was the largest nitrous oxide source under these conditions. This meta-analysis also revealed that nitrogen input stimulated dissolved organic carbon, ammonium, nitrate, microbial biomass carbon and microbial biomass nitrogen accumulation in the wetland ecosystem. The variation-partitioning analysis and structural equation model were used to analyze the relationship between the greenhouse gas and labile carbon and nitrogen further. These results revealed that dissolved organic carbon (DOC) is the primary factor driving greenhouse gas emission from wetlands under global nitrogen input, whereas microbial biomass carbon (MBC) more directly affects greenhouse gas emission than other labile carbon and nitrogen.