Regional heterogeneity and driving factors of road runoff pollution from urban areas in China.

Due to the multiple influences of natural and anthropogenic factors, stormwater runoff from urban roads generally presents heterogeneous pollution among cities. The identification of regional heterogeneity and related driving factors of road runoff pollution is of significance for the optimal management of road runoff pollution according to the local circumstances. In this study, the regional heterogeneity of urban road runoff pollution from fourteen representative cities in China is analyzed for four typical pollutants including total suspended solids (TSS), chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP). The results show wide variations in TSS, COD, TN and TP pollution among cities, with the average event mean concentrations ranging from 77.0 to 1347.9, 31.4 to 488.1, 0.81 to 8.46, 0.139 to 1.930 mg/L, respectively. One-way ANOVA analyses demonstrate significant differences in road runoff pollution among cities. The TSS pollution is significantly heavier for northern and northwestern inland cities than that for eastern and southern cities. Pearson correlation analysis and Stepwise linear regression analysis are performed to identify and rank the influence of climate, population, economy, industry structure, traffic and environmental quality. Direct relationships of road runoff pollution are detected with PM2.5, PM10, secondary industry, tertiary industry, annual rainfall, and urban green coverage, among which PM10 and urban green coverage are the most important and common factors exerting positive and negative influences on road runoff pollution, respectively. Based on the findings of this work, improvement of atmospheric particulate pollution and increase in urban greenness are recommended measures to manage the road runoff pollution. Furthermore, the traffic-related emissions accompanying the upgrading of industry structure should be effectively controlled to attenuate the TSS and COD pollution in road runoff.

A novel index for assessing the water quality of urban landscape lakes based on water transparency.

Assessment of the aesthetic and recreational value of urban landscape lakes (ULLs) is often required but there has not been a water quality index specifically applicable for such a purpose. Under a consideration that water transparency in terms of Secchi Depth (SD), to a large extent, determines the landscape effect, a study was conducted to identify the major parameters that strongly influence SD and to develop a novel water quality index. By theoretical analyses, it was found that SD is mainly influenced by the contents of chlorophyll a, inorganic suspended solids and organic detritus in water, which collectively relate to eight independent water quality, hydraulic, and environmental parameters, including SS, DO, COD, NH4+-N, NO3--N, TP, HRT, and water temperature T. A composite index was then proposed in the form of WQIULL = ∏i=1nqiwi (n = 8). Using the data of field survey of 166 ULLs in China, the cumulative probability distribution curve of each sub-index qi was characterized. Sensitive analysis was conducted for the determination of the sub-index weight (wi) for each qi under the consideration of two typical scenarios of ULL replenishment by stream water (traditional source) and reclaimed water (alternative source) regarding the variation of parameter on SD. With all wi (i = 1 to 8) thus determined, WQIULL was calculated for each of the ULLs surveyed. All the calculated values of WQIULL showed a good correlative relationship with the SD values practically measured (R2 = 0.8948), indicating that the novel water quality index developed could effectively indicate the satisfactory degree of the lake water quality in terms of water landscape. Further by comparing the dimensionless WQIULL (ranging between 0 and 100) with the practically acceptable SD based on experiences in China, the method for classification of ULLs by WQIULL calculation was formulated.

Integrating stereo-elastic packing into ecological floating bed for enhanced denitrification in landscape water.

The effects of stereo-elastic packing, as additional bio-carriers, on nitrogen removal in enhanced ecological floating beds (EFBs) are evaluated. Enhanced EFBs with additional stereo-elastic packing was demonstrated to enhance maximum TN removal efficiency (65.8%) over that of EFBs with plant and ceramisite only (54.9%). Performance enhancement was attributable to a 40.6% increase in sediment N accretion and intensification of denitrification by biomass on other carriers in the presence of stereo-elastic packing. Nonetheless, nitrogen uptake by plants was inhibited slightly. Stereo-elastic packing intensified denitrification rates on plant roots and ceramisite by increasing the attached biomass and enhancing the biomass activity, albeit to different extents. The increase in denitrification rate on plant root by 25.7% was significantly higher than that of 4.6% on ceramisite via increased NO2-N removal. Moreover, bacterial diversity on the carriers was significantly altered, and the enrichment of genera such as Aridibacter, Hyphomicrobium and Gemmobacter promoted denitrification processes.

Current status and characteristics of urban landscape lakes in China.

Urban landscape lakes (ULLs) are important environmental elements in most cities. In order to understand the current situation of ULLs in China and formulate proper strategies to improve their landscape quality to meet public desire for water-front enjoyment, a study was conducted of 189 ULLs widely distributed in 26 provinces of China, based on existing data and field surveys. These ULLs were firstly categorized according to their topographic features, climatic zones, and water replenishment sources. Lake water quality was evaluated considering both single factors and a comprehensive pollution index (CPI). Results show that if the Chinese Surface Water Quality Standard was used as the sole criteria, about 60% of the ULLs investigated could not meet the lowest requirement. Excessive total nitrogen (TN) concentration was the most limiting factor especially when reclaimed water was the replenishment source. The differences in topographic and climatic conditions to a certain extent affected the availability of replenishment water sources but no significant correlation was identified with the single water quality factors or CPI. However, when public satisfaction was introduced in the evaluation of the ULLs' landscape effect, it was found that the water transparency in terms of Secchi Depth (SD) correlated well with people's appreciation of water landscape.

[Enhanced Pollutant Removal Performance of an Integrated Biological Settling Tank from Micro-polluted Water Bodies].

To improve the capacity of present drinking water purification process on the removal of soluble pollutants and solve the problem of large area requirement and single function existing in the application of horizontal sedimentation tank, a novel biological settling tank was developed based on the designing concepts of rotating biological disk and sedimentation tank. Experimental results showed that the usage of rotating biological disk did not have notable effects on the turbidity removal capacity of the horizontal sedimentation tank. When the organic loading rate was 0.46 g·(m2·d)-1, the removal rates of organic pollutants, NH4+-N, TN, and TP were determined to be 81.4%, 95.0%, 21.1% and 86.0%, respectively. Further study showed that denitrification and dephosphorization processes competed for the limited carbon source existing in the water phase. With the increase of organic loading rate in the raw water, the removal rate of TP was improved. Meanwhile, the concentrations of organic matters and NH4+-N in the settled water were not affected, which indicated that the biological settling tank showed a capacity in resisting organic loading rate shock and could be used in the enhanced pollutant removal in treating micro-polluted water.