Distribution of heavy metals in the dissolved and suspended phase of the sea-surface microlayer, seawater column and in sediments of Singapore’s coastal environment

Concentrations of heavy metals were determined in the water column (including the sea-surface microlayer, subsurface, mid-depth and bottom water) and sediments from Singapore’s coastal environment. The concentration ranges for As, Cd, Cr, Cu, Ni, Pb and Zn in the seawater dissolved phase (DP) were 0.34–2.04, 0.013–0.109, 0.07–0.35, 0.23–1.16, 0.28–0.78, 0.009–0.062 and 0.97–3.66 μg L⁻¹ respectively. The ranges for Cd, Cr, Cu, Ni, Pb and Zn in the suspended particulate matter (SPM) were 0.16–0.73, 6.72–53.93, 12.87–118.29, 4.34–60.71, 1.10–6.08 and 43.09–370.49 μg g⁻¹, respectively. Heavy metal concentrations in sediments ranged between 0.054–0.217, 37.48–50.52, 6.30–21.01, 13.27–26.59, 24.14–37.28 and 48.20–62.36 μg g⁻¹ for Cd, Cr, Cu, Ni, Pb and Zn, respectively. The lowest concentrations of metals in the DP and SPM were most frequently found in the subsurface water while the highest concentrations were mostly observed in the SML and bottom water. Overall, heavy metals in both the dissolved and particulate fractions have depth profiles that show a decreasing trend of concentrations from the subsurface to the bottom water, indicating that the prevalence of metals is linked to the marine biological cycle. In comparison to data from Greece, Malaysia and USA, the levels of metals in the DP are considered to be low in Singapore. Higher concentrations of particulate metals were reported for the Northern Adriatic Sea and the Rhine/Meuse estuary in the Netherlands compared to values reported in this study. The marine sediments in Singapore are not heavily contaminated when compared to metal levels in marine sediments from other countries such as Thailand, Japan, Korea, Spain and China.     

Nanotechnology for improved production of algal biofuels: a review

Environmental Chemistry Letters - Fossil fuel depletion and carbon dioxide emissions are calling for carbon neutral energies such as algal biofuels, yet actual production of agal biofuels is...     

Remediation of soil and groundwater contaminated with organic chemicals using stabilized nanoparticles: Lessons from the past two decades

▪ Overviewed evolution and environmental applications of stabilized nanoparticles. ▪ Reviewed theories on particle stabilization for enhanced reactivity/deliverability. ▪ Examined various in situ remediation technologies based on stabilized nanoparticles. ▪ Summarized knowledge on transport of stabilized nanoparticles in porous media. ▪ Identified key knowledge gaps and future research needs on stabilized nanoparticles. Due to improved soil deliverability and high reactivity, stabilized nanoparticles have been studied for nearly two decades for in situ remediation of soil and groundwater contaminated with organic pollutants. While large amounts of bench- and field-scale experimental data have demonstrated the potential of the innovative technology, extensive research results have also unveiled various merits and constraints associated different soil characteristics, types of nanoparticles and particle stabilization techniques. Overall, this work aims to critically overview the fundamental principles on particle stabilization, and the evolution and some recent developments of stabilized nanoparticles for degradation of organic contaminants in soil and groundwater. The specific objectives are to: 1) overview fundamental mechanisms in nanoparticle stabilization; 2) summarize key applications of stabilized nanoparticles for in situ remediation of soil and groundwater contaminated by legacy and emerging organic chemicals; 3) update the latest knowledge on the transport and fate of stabilized nanoparticles; 4) examine the merits and constraints of stabilized nanoparticles in environmental remediation applications; and 5) identify the knowledge gaps and future research needs pertaining to stabilized nanoparticles for remediation of contaminated soil and groundwater. Per instructions of this invited special issue, this review is focused on contributions from our group (one of the pioneers in the subject field), which, however, is supplemented by important relevant works by others. The knowledge gained is expected to further advance the science and technology in the environmental applications of stabilized nanoparticles.     

Arsenic-contaminated groundwater and its potential health risk: A case study in Long An and Tien Giang provinces of the Mekong Delta,Vietnam

Environmental Science and Pollution Research - The occurrence of arsenic (As) in groundwater (drilled well water) that were used for drinking, cooking, and personal hygiene and its risks to human...     

Thiocyanate-induced labilization of schwertmannite: Impacts and mechanisms

Schwertmannite is an amorphous iron(III)-oxyhydroxysulfate that forms in acid mine drainage(AMD) environments. The characteristic of high heavy metal adsorption capability makes schwertmannite a potentially useful, environmentally friendly material in wastewater treatment. Unstable schwertmannite is prone to recrystallization.Understanding the mechanisms that induce schwertmannite labilization and affect its capacity to remove heavy metals are of great environmental and geochemical significance.Thiocyanate(SCNˉ) is a hazardous pseudohalide that is also normally found in AMD.However, little is known about the impact of Fe(III)-binding ligand SCNˉ on schwertmannite stability and its subsequent capacity to bind trace elements. Here, we investigated the adsorption of SCNˉ on schwertmannite and subsequent mineral transformation to characterize this little-known process. The appearance of Fe2+indicated that the interactions between schwertmannite and SCNˉ may involve complexation and reduction reactions. Results showed that the majority of the adsorbed-SCNˉ was immobilized on schwertmannite during the 60-days transformation. The transformation rates of schwertmannite increased with increasing concentrations of SCNˉ. Goethite was detected as the dominant transformation product with or without SCNˉ. The mechanisms of SCNˉ-promoted dissolution of schwertmannite can be described as follows:(1) formation of Fe(III)–NCS complexes on the schwertmannite surface and in solution, a process which increases the reactivity of solid phase Fe(III);(2) the extraction of Fe(III) from schwertmannite by SCNˉ and subsequent schwertmannite dissolution; and(3) the formation of secondary minerals from extracted Fe(III). These findings may improve AMD treatment strategies and provide insight into the use and potential reuse of schwertmannite as a trace element sorbent.     

复合多管除尘器在湿法水泥回转窑除尘中的应用

把具有惯性沉降除尘、旋风子除尘两级一体功能的复合多管除尘器用于带湿式蒸发器的湿法水泥回转窑尾气除尘，替换原“旋风除尘器＋电除尘器”除尘系统中的多筒旋风器。运行测试表明，它的除尘效率达到９４６％，确保了窑尾排放烟尘浓度达到国家标准。     

工艺安全管理系统的发展现状及建议

介绍工艺安全管理的发展历程、关键要素及各要素在企业不同生命周期的应用,总结国外发达国家的相关法规及实施工艺安全管理后重大事故发生概率的变化,对我国工艺安全管理提出建议。     

无砾石微孔管地下渗滤系统研究

针对传统无砾石管式地下渗滤系统存在的易堵塞,大气复氧率低和通量低等问题,采取了优选植物、改进渗滤管结构和布水方式等措施。在前期小试的基础上,研究了大管径和小管径在处理生活污水时的效果。结果表明,采用大管径可在一定程度上提高系统的复氧效率,对污染物的去除效果优于小管径,其COD、TP、NH4+-N和TN的平均去除率分别达到87.07%、84.97%、45.6%和52.67%。对氨氮和总氮的去除机理的分析表明,由硝化/反硝化实现生物脱氮是地下渗滤系统去除总氮的主要途径,氨氮的去除率大小反映了硝化反应的强度,改善水力负荷和土壤环境以促进硝化作用是使该系统提高氨氮和总氮去除率的关键。     

基于风险的压缩天然气加气站安全距离研究

首次以个体自然死亡概率为基础,确定个体风险标准,提出压缩天然气加气站关键设备与暴露目标之间安全距离确定方法的基本原则在此基础上,根据泄漏模式确定关键设备泄漏频率,采用几何风险消减因子对泄漏频率进行修正,选出需要计算安全距离的关键设备,按照伤害准则,确定关键设备发生危险场景的安全距离.     

天津市烟气排放连续监测系统现状分析及应用经验探讨

CEMS,即烟气连续排放监测系统,通过对固定污染源颗粒物浓度和气态污染物浓度以及污染物排放总量进行连续自动监测,并将监测数据和信息传送到环保主管部门,以确保排污企业污染物浓度和排放总量达标。本文分析了目前天津使用的烟气在线连续监测系统的三种主要技术方法,通过三种方法的比较,结合现场监测的实际经验,提出了今后CEMS运营管理的相关建议。