扬州市不同功能区表层土壤中多环芳烃的含量、来源及其生态风险

对扬州市6个不同功能区（公园、菜地、文教区、居民区、加油站和工业区）共59个表层土壤样品（0~10 cm）中15种美国环境保护署优控的多环芳烃（PAHs）的含量和来源进行了分析,并利用苯并[a]芘（BaP）毒性当量浓度（TEQ_BaP）评价了土壤中PAHs的生态风险.结果表明,扬州市土壤中Σ15PAHs总量范围为21~36118 μg·kg^-1,中值为295 μg·kg^-1,PAHs组成中以4~6环为主.不同功能区Σ15PAHs总量平均值高低顺序为工业区 > 加油站 > 文教区 > 菜地 > 居民区 > 公园.相关性分析表明,整个扬州市土壤中Σ15PAHs总量与土壤总有机碳（TOC）（P<0.05）和黑碳（BC）（P<0.01）含量都呈显著性正相关,但除了加油站土壤中Σ15PAHs总量与BC含量呈显著性正相关（P<0.01）外,不同功能区土壤中Σ15PAHs总量与TOC、BC含量都无显著相关性.特征比值法结果表明,不同功能区土壤中PAHs来源虽有些差异,但都主要来源于石油泄漏以及石油、煤和生物质等的燃烧.扬州市土壤中15种PAHs总TEQ_BaP值的范围是2~4448 μg·kg^-1.以荷兰土壤环境标准中的10种PAHs总TEQ_BaP值33 μg·kg^-1为标准,扬州市有45.8%的土样超标,各功能区点位超标率高低顺序为工业区（70%） > 加油站（60%） > 文教区（55.6%） > 菜地（50.0%） > 居民区（30%） > 公园（10%）.因此,扬州市不同功能区中都有部分表层土壤存在潜在的生态风险,工业区和加油站风险相对较高,而居民区和公园风险相对较低.     

南京北郊PM2.5中有机组分的吸光性质及来源

对南京北郊2018年9月~2019年9月PM_2.5中有机组分的吸光性质进行了研究,并利用PM_2.5化学组成及主成分分析法分析该地区吸光性有机碳（棕碳,brown carbon,BrC）的主要来源.结果表明,水溶性有机碳（water-soluble organic carbon,WSOC）和甲醇可提取有机碳（methanol extractable organic carbon,MEOC）在365 nm处光吸收系数（Abs_365,w和Abs_365,m）的平均值分别为（3.22±2.18）Mm^-1和（7.69±4.93）Mm^-1.Abs_365,w和Abs_365,m分别与WSOC（r=0.72,P<0.01）和MEOC（r=0.62,P=0.04）的质量浓度显著相关,均表现为冬高夏低,夜高昼低的时间变化特征.这可归结于冬季和夜间的气象特征（例如边界层高度降低和大气稳定度升高）、冬季一次源排放的增加以及夏季和白天更强的"光漂白作用".Abs_365,m/Abs_365,w的年均值（2.60±0.92）远高于MEOC/WSOC（质量浓度比值,1.37±0.30）,表明MEOC中非水溶性组分的吸光作用更强,在BrC的吸光作用中占主导地位.WSOC、MEOC、Abs_365,m和K⁺均未表现出强相关性（r<0.60）,因此生物质燃烧不是该地区BrC的主要一次来源.WSOC和MEOC质量吸收效率（MAE_365,w和MAE_365,m）及其比值（MAE_365,m/MAE_365,w）的季节变化和Abs₃₆₅相同.MEOC中非水溶性组分的MAE₃₆₅［（4.10±5.15）m²·g^-1］分别是MAE_365,w和MAE_365,m的6.0和2.9倍,支持BrC的吸光作用受非水溶性有机组分主导这一推断.和WSOC的埃氏吸收指数（Å_WSOC）相比,MEOC的埃氏吸收指数（Å_MEOC）随时间变化更显著,这可能与非水溶性吸光组分排放的季节变化有关.主成分分析结果显示,本研究PM_2.5中有机组分的吸光作用主要来源于二次形成过程和人为活动相关的一次排放,而不是生物质燃烧.     

太原市城区夏季VOCs来源及其对O3生成的贡献

采集太原市城区夏季VOCs样品并分析其浓度特征,使用参数修正法得到VOCs初始浓度,分析其来源及对O₃生成的贡献.结果显示：太原市城区总VOCs平均浓度为48.13 μg/m³,烷烃（25.52 μg/m³）为主要组分.VOCs浓度呈明显日变化特征,在日间（10：00~14：00）光化学产生O₃的关键时段浓度最低.油品挥发、机动车排放、燃煤、植物排放与液化石油气/天燃气（LPG/NG）使用源对修正后环境VOCs的贡献分别为26.89%、25.55%、21.14%、14.99%、11.44%,对O₃生成的贡献分别为21.44%、33.10%、24.07%、13.77%、7.62%.机动车为新鲜排放气团VOCs的重要来源,而油品挥发、燃煤的输送与本地积累是其他（混合、夜间与反应）气团VOCs的重要来源.机动车排放、油品挥发与燃煤为VOCs与O₃生成的重要贡献源,控制此类源排放可减少太原市城区环境VOCs浓度并有效降低O₃生成.     

重稀土元素钇对短程反硝化工艺的影响

研究重稀土元素钇（Y（III））对短程反硝化工艺的短期和长期影响.结果表明,1~50mg/L的Y（III）对亚硝酸盐的积累量无明显影响,60~100mg/L的Y（III）会影响硝酸盐的还原和亚硝酸盐的积累.1~10mg/L的Y（III）对细菌活性呈现促进作用,20~100mg/L的Y（III）对细菌活性呈现抑制作用.胞外吸附的Y（III）是抑制细菌活性的主要因子,线性拟合的相关性系数R²为0.957,半抑制浓度IC_50（吸附）为1.079mg/L（以湿重计）,对应水中Y（III）浓度为54.35mg/L.SEM显示,添加Y（III）会使细菌产生更多的胞外聚合物（EPS）将细菌包裹以抵抗Y（III）的毒性,EDS显示被包裹的细菌表面碳、氮元素含量大幅度降低,EPS影响了底物的传质.130d的长期实验表明,5mg/L的Y（III）会使反应器的反硝化性能逐渐消失,停止添加稀土后,反应器的亚硝酸盐积累功能也不能恢复.     

Marine aquaculture regulates dissimilatory nitrate reduction processes in a typical semi-enclosed bay of southeastern China

Marine aquaculture in semi-enclosed bays can significantly influence nutrient cycling in coastal ecosystems. However, the impact of marine aquaculture on the dynamics of dissimilatory nitrate reduction processes (DNRPs) and the fate of reactive nitrogen remain poorly understood. In this study, the rates of DNRPs and the abundances of related functional genes were investigated in aquaculture and non-aquaculture areas. The results showed that marine aquaculture significantly increased the denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) rates and decreased the rate of anaerobic ammonium oxidation (ANA), as compared with non-aquaculture sites. DNF was the dominant pathway contributing to the total nitrate reduction, and its contribution to the total nitrate reduction significantly increased from 66.72% at non-aquaculture sites to 78.50% at aquaculture sites. Marine aquaculture can significantly affect the physicochemical characteristics of sediment and the abundances of related functional genes, leading to variations in the nitrate reduction rates. Although nitrate removal rates increased in the marine aquaculture area, ammonification rates and the nitrogen retention index in the aquaculture areas were 2.19 and 1.24 times, respectively, higher than those at non-aquaculture sites. Net reactive nitrogen retention exceeded nitrogen removal in the aquaculture area, and the retained reactive nitrogen could diffuse with the tidal current to the entire bay, thereby aggravating N pollution in the entire study area. These results show that marine aquaculture is the dominant source of nitrogen pollution in semi-enclosed bays. This study can provide insights into nitrogen pollution control in semi-enclosed bays with well-developed marine aquaculture.     

Spatiotemporal trends of PM2.5 and its major chemical components at urban sites in Canada

To evaluate the effectiveness of emission control regulations designed for reducing air pollution, chemically resolved PM_2.5 data have been collected across Canada through the National Air Pollution Surveillance network in the past decade. 24-hr time integrated PM_2.5 collected at seven urban and two rural sites during 2010-2016 were analyzed to characterize geographical and seasonal patterns and associated potential causes. Site-specific seven-year mean gravimetric PM_2.5 mass concentrations ranged from 5.7 to 9.6 µg/m³. Seven-year mean concentrations of SO₄^2?, NO₃^?, NH₄⁺, organic carbon (OC), and elemental carbon (EC) were in the range of 0.68 to 1.6, 0.21 to 1.5, 0.27 to 0.71, 1.1 to 1.9, and 0.37 to 0.71 µg /m³, accounting for 10.8%-18.1%, 3.7%-16.7%, 4.7%-7.4%, 18.4%-21.0%, and 6.4%-10.6%, respectively, of gravimetric PM_2.5 mass. PM_2.5 and its five major chemical components showed higher concentrations in southeastern Canada and lower values in Atlantic Canada, with the seven-year mean ratios between the two regions being on the order of 1.7 for PM_2.5 and 1.8-7.1 for its chemical components. When comparing the concentrations between urban and rural sites within the same region, those of SO₄^2? and NH₄⁺ were comparable, while those of NO₃^?, OC, and EC were around 20%, 40%-50%, and 70%-80%, respectively, higher at urban than rural sites, indicating the regional scale impacts of SO₄^2? and NH₄⁺ and effects of local sources on OC and EC. Monthly variations generally showed summertime peaks for SO₄^2? and wintertime peaks for NO₃^?, but those of NH₄⁺, OC, and EC exhibited different seasonality at different locations.     

Spatiotemporal variations of ambient air pollutants and meteorological influences over typical urban agglomerations in China during the COVID-19 lockdown

To investigate the air quality change during the COVID-19 pandemic, we analyzed spatiotemporal variations of six criteria pollutants in nine typical urban agglomerations in China using ground-based data and examined meteorological influences through correlation analysis and backward trajectory analysis under different responses. Concentrations of PM_2.5, PM₁₀, NO₂, SO₂ and CO in urban agglomerations respectively decreased by 18%–45% (30%–62%), 17%–53% (22%–39%), 47%-64% (14%–41%), 9%–34% (0%–53%) and 16%-52% (23%–56%) during Lockdown (Post-lockdown) period relative to Pre-lockdown period. PM_2.5 pollution events occurred during Lockdown in Beijing-Tianjin-Hebe (BTH) and Middle and South Liaoning (MSL), and daily O₃ concentration rose to grade Ⅱ standard in Post-lockdown period. Distinct from the nationwide slump of NO₂ during Lockdown period, a rebound (～40%) in Post-lockdown period was observed in Cheng-Yu (CY), Yangtze River Middle-Reach (YRMR), Yangtze River Delta (YRD) and Pearl River Delta (PRD). With slightly higher wind speed compared with 2019, the reduction of PM_2.5 (51%–62%) in Post-lockdown period is more than 2019 (15%–46%) in HC (Harbin-Changchun), MSL, BTH, CP (Central Plain) and SP (Shandong-Peninsula), suggesting lockdown measures are effective to PM_2.5 alleviation. Although O₃ concentrations generally increased during the lockdown, its increment rate declined compared with 2019 under similar sunlight duration and temperature. Additionally, unlike HC, MSL and BTH, which suffered from additional (> 30%) air masses from surrounding areas after the lockdown, the polluted air masses reaching YRD and PRD mostly originated from the long-distance transport, highlighting the importance of joint regional governance.     

Chemical characteristics, oxidative potential, and sources of PM2.5 in wintertime in Lahore and Peshawar, Pakistan

The chemical characteristics, oxidative potential, and sources of PM_2.5 were analyzed at the urban sites of Lahore and Peshawar, Pakistan in February 2019. Carbonaceous species, water soluble ions, and metal elements were measured to investigate the chemical composition and sources of PM_2.5. The dithiothreitol (DTT) consumption rate was measured to evaluate the oxidative potential of PM_2.5. Both cities showed a high exposure risk of PM_2.5 regarding its oxidative potential (DTT_v). Carbonaceous and some of the elemental species of PM_2.5 correlated well with DTT_v in both Lahore and Peshawar. Besides, the DTT_v of PM_2.5 in Lahore showed significant positive correlation with most of the measured water soluble ions, however, ions were DTT-inactive in Peshawar. Due to the higher proportions of carbonaceous species and metal elements, Peshawar showed higher mass-normalized DTT activity of PM_2.5 compared to Lahore although the average PM_2.5 concentration in Peshawar was lower. The high concentrations of toxic metals also posed serious non-carcinogenic and carcinogenic risks to the residents of both cities. Principle component analysis coupled with multiple linear regression was applied to investigate different source contributions to PM_2.5 and its oxidative potential. Mixed sources of traffic and road dust resuspension and coal combustion, direct vehicle emission, and biomass burning and formation of secondary aerosol were identified as the major sources of PM_2.5 in both cities. The findings of this study provide important data for evaluation of the potential health risks of PM_2.5 and for formulation of efficient control strategies in major cities of Pakistan.     

Influence of urban morphological parameters on the distribution and diffusion of air pollutants: A case study in China

Air pollution has a serious fallout on human health, and the influences of the different urban morphological characteristics on air pollutants cannot be ignored. In this study, the relationship between urban morphology and air quality (wind speed, CO, and PM_2.5) in residential neighborhoods at the meso-microscale was investigated. The changes in the microclimate and pollutant diffusion distribution in the neighborhood under diverse weather conditions were simulated by Computational Fluid Dynamics (CFD). This study identified five key urban morphological parameters (Building Density, Average Building Height, Standard Deviation of Building Height, Mean Building Volume, and Degree of Enclosure) which significantly impacted the diffusion and distribution of pollutants in the neighborhood. The findings of this study suggested that three specific strategies (e.g. volume of a single building should be reduced, DE should be increased) and one comprehensive strategy (the width and height of the single building should be reduced while the number of single buildings should be increased) could be illustrated as an optimized approach of urban planning to relief the air pollution. The result of the combined effects could provide a reference for mitigating air pollution in sustainable urban environments.     

Preparation and characterization of boron-doped corn straw biochar: Fe (Ⅱ) removal equilibrium and kinetics

Nowadays, iron ions as a ubiquitous heavy metal pollutant are gradually concerned and the convenient and quick removal of excessive iron ions in groundwater has become a major challenge for the safety of drinking water. In this study, boron-doped biochar (B-BC) was successfully prepared at various preparation conditions with the addition of boric acid. The as-prepared material has a more developed pore structure and a larger specific surface area (up to 897.97 m²/g). A series of characterization results shows that boric acid effectively activates biochar, and boron atoms are successfully doped on biochar. Compared with the ratio of raw materials, the pyrolysis temperature has a greater influence on the amount of boron doping. Based on Langmuir model, the maximum adsorption capacity of 800B-BC_1:2 at 25 °C, 40 °C, 55 °C are 50.02 mg/g, 95.09 mg/g, 132.78 mg/g, respectively. Pseudo-second-order kinetic model can better describe the adsorption process, the adsorption process is mainly chemical adsorption. Chemical complexation, ions exchange, and co-precipitation may be the main mechanisms for Fe²⁺ removal.