Heavy metals in coastal wetland sediments of the Pearl River Estuary, China

Sediment quality in coastal wetlands of the Pearl River Estuary was concerned since the wetlands were used for land reclamation, aquaculture and wildlife protection, and meanwhile served as one of the main ultimate sinks for large amount of heavy metals discharged from the rapidly developing Pearl River Delta. Total concentrations of heavy metal, such as Zn, Ni, Cr, Cu, Pb, and Cd, and their chemical speciation were investigated. Results showed that the sediments were significantly contaminated by Cd, Zn and Ni with concentration ranges of 2.79-4.65, 239.4-345.7 and 24.8-122.1mg/kg, respectively. A major portion (34.6-46.8%) of Pb, Cd, and Zn was strongly associated with exchangeable fractions, while Cu, Ni and Cr were predominantly associated with organic fractions, residual, and Fe-Mn oxide. Cd and Zn would be the main potential risk and the sediment quality is no longer meeting the demand of the current wetland utilization strategies.     

Significant concurrent decrease in PM2.5 and NO2 concentrations in China during COVID-19 epidemic

The strict control measures and social lockdowns initiated to combat COVID-19 epidemic have had a notable impact on air pollutant concentrations. According to observation data obtained from the China National Environmental Monitoring Center, compared to levels in 2019, the average concentration of NO₂ in early 2020 during COVID-19 epidemic has decreased by 53%, 50%, and 30% in Wuhan city, Hubei Province (Wuhan excluded), and China (Hubei excluded), respectively. Simultaneously, PM_2.5 concentration has decreased by 35%, 29%, and 19% in Wuhan, Hubei (Wuhan excluded), and China (Hubei excluded), respectively. Less significant declines have also been found for SO₂ and CO concentrations. We also analyzed the temporal variation and spatial distribution of air pollutant concentrations in China during COVID-19 epidemic. The decreases in PM_2.5 and NO₂ concentrations showed relatively consistent temporal variation and spatial distribution. These results support control of NO_x to further reduce PM_2.5 pollution in China. The concurrent decrease in NO_x and PM_2.5 concentrations resulted in an increase of O₃ concentrations across China during COVID-19 epidemic, indicating that coordinated control of other pollutants is needed.     

Revealing the characteristics of dissolved organic matter in urban runoff at three typical regions via optical indices and molecular composition

Dissolved organic matter (DOM) plays a major role in ecological systems and influences the fate and transportation of many pollutants. Despite the significance of DOM, understanding of how environmental and anthropogenic factors influence its composition and characteristics is limited, especially in urban stormwater runoff. In this article, the chemical properties (pollutant loads, molecular weight, aromaticity, sources, and molecular composition) of DOM in stormwater extracted from three typical end-members (traffic, residential, and campus regions) were characterized by UV–visible (UV–vis) spectroscopy, excitation-emission matrix spectroscopy combined with parallel factor analysis (EEM-PARAFAC), and ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). There are three findings: (1) The basic properties of DOM in stormwater runoff varied obviously from three urban fields, and the effect of initial flush was also apparent. (2) The DOM in residential areas mainly came from autochthonous sources, while allochthonous sources primarily contributed to the DOM in traffic and campus areas. However, it was mainly composed of terrestrial humic-like components with CHO and CHON element composition and HULO and aliphatic formulas. (3) The parameters characterizing DOM were primarily related to terrestrial source and aromaticity, but their correlations varied. Through the combination of optical methods and UPLC-Q-TOF spectrometry, the optical and molecular characteristics of rainwater are effectively revealed, which may provide a solid foundation for the classification management of stormwater runoff in different urban regions.     

Enhanced adsorption of arsenate on titanium dioxide using Ca and Mg ions

In this study, we report the effects of pH and divalent cations on the adsorption of arsenate (As(V)) by titanium dioxide (TiO₂) nanoparticles. The extent of As(V) adsorption on TiO₂ decreased with increasing pH due to the decrease of positively charged binding sites on the TiO₂ surface. The Langmuir maximum uptake capacity at pH 4 is about three times higher than that at pH 7. Here we show that the relatively low As(V) uptake at circumneutral pH could be substantially enhanced by the addition of common divalent cations such as magnesium and calcium. At a concentration of approximately 7 mM, magnesium and calcium increased the extent of As(V) adsorption from 2.1 to 6.5 and 7.7 mg As(V)/g TiO₂, respectively.     

浅谈我国旅游环境的开发与可持续发展

分析了目前我国旅游环境存在的主要问题，阐述了旅游环境开发与可持续发展的辨证关系，提出了实现我国旅游环境可持续发展的对策与建议。     

PM2.5污染特征及污染源模拟研究

为了解深圳市坪山新区环境空气质量现状,研究运用坪山新区PM2.5浓度数据,分析该区PM2.5的污染特征及气象条件对其的影响,坪山新区PM2.5浓度呈现了明显的季节变化、月变化特征,表现为秋冬季高、夏季低、春季居中的特点;PM2.5浓度最高出现在12月,最低出现在7月.该区PM2.5浓度日间变化呈双峰分布,7:00～9:00出现短期高峰,夜间21:00～次日4:00出现长期高峰.坪山新区PM2.5超标情况多出现在秋冬季及初春.在超标日期里,区域一般温度较低、风速较小,相对湿度也较低.污染源分析模型结果表明,坪山新区PM2.5的排放强度高值区主要集中在北部和西部,南部和东部排放强度稍低.由此可见,坪山新区大气环境亟待提升,需要针对区域内大气颗粒物污染进行有效防治.     

上海市崇明岛公路两侧土壤重金属污染研究

采集了上海市崇明岛陈海、北沿公路两侧土壤和灰尘样品270余个,测定了样品的Pb、Cd、Cu、 Zn和Cr重金属含量。结果表明,陈海和北沿公路两侧土壤重金属Pb、Cd、Cu、 Zn和Cr的平均含量达到277、0279、258、918和776 mg/kg,土壤Cd污染较严重。采集的路面灰尘样品Pb、Cd、Cu、 Zn和Cr的平均含量达到512、049、489、209和970 mg/kg,超过土壤背景值2~4倍,是土壤重金属的主要二次污染源。公路防护林体系较差的北沿公路路侧土壤纵向剖面（垂直于公路走向）重金属含量随距路肩距离增加呈指数下降,土壤重金属重污染区在距路肩15 m范围内。防护林体系较完善的陈海公路距路肩15 m范围内土壤重金属污染较小,土壤重金属重污染区出现在距路肩20~50 m范围内。     

基于污染物总量控制的流域预警体系构建研究

文章通过对中国目前水环境质量现状分析,指出流域环境预警体系建立的必要性,并选择总量控制指标作为预警体系的评价指标。利用层次分析法建立基于污染物总量控制的流域预警体系,确定预警因子的权重和评分标准。设立临界状态,不良状态预警、缓慢恶化预警和迅速恶化预警4个级别,为建立流域环境质量预警体系提供借鉴。     

Prediction of Cadmium uptake by brown rice and derivation of soil–plant transfer models to improve soil protection guidelines

Cadmium (Cd) levels in paddy fields across Taiwan have increased due to emission from industry. To ensure the production of rice that meets food quality standards, predictive models or suitable soil tests are needed to evaluate the quality of soils to be used for rice cropping. Levels of Cd in soil and rice grains were measured in 19 paddy fields across the western plains in Taiwan. Cadmium levels in soil range from less than 0.1 mg kg^?1 to 30 mg kg^?1. Measured Cd levels in brown rice were predicted very well (R² > 0.8) based on Cd and Zinc in a 0.01 M CaCl₂ extract or a soil–plant transfer model using the reactive soil Cd content, pH, and cation exchange capacity. In contrast to current soil quality standards used in Taiwan, such models are effective in identifying soils where Cd in rice will exceed food quality standards.