Effects of a diesel oxidation catalyst on gaseous pollutants and fine particles from an engine operating on diesel and biodiesel

The effects of a diesel oxidation catalytic (DOC) converter on diesel engine emissions were investigated on a diesel bench at various loads for two steady-state speeds using diesel fuel and B20. The DOC was very effective in hydrocarbon (HC) and CO oxidation. Approximately 90%–95% reduction in CO and 36%–70% reduction in HC were realized using the DOC. Special attention was focused on the effects of the DOC on elemental carbon (EC) and organic carbon (OC) fractions in fine particles (PM_2.5) emitted from the diesel engine. The carbonaceous compositions of PM_2.5 were analyzed by the method of thermal/optical reflectance (TOR). The results showed that total carbon (TC), OC and EC emissions for PM_2.5 from diesel fuel were generally reduced by the DOC. For diesel fuel, TC emissions decreased 22%–32% after the DOC depending on operating modes. The decrease in TC was attributed to 35%–97% decrease in OC and 3%–65% decrease in EC emissions. At low load, a significant increase in the OC/EC ratio of PM_2.5 was observed after the DOC. The effect of the DOC on the carbonaceous compositions in PM_2.5 from B20 showed different trends compared to diesel fuel. At low load, a slight increase in EC emissions and a significant decrease in OC/EC ratio of PM_2.5 after DOC were observed for B20.     

草地退化对三江源区高寒草甸生态系统CO2通量的影响及其原因

为了揭示草地退化对三江源地区高寒草甸生态系统碳通量的影响,利用涡度相关技术,于2006年12月1日~2007年11月30日对三江源地区的退化高寒草甸生态系统的碳通量及生物和环境因子进行观测.结果发现:草地退化对高寒草甸生态系统的碳通量产生了深刻影响,与未退化的高寒草甸生态系统相比,退化高寒草甸生态系统全年总初级生产力(GPP)下降了36.6%,全年生态系统呼吸(Reco)下降了7.9%,全年净生态系统CO2交换(NEE)也由退化前的负值(碳吸收)转变为正值(碳排放),二者相差132.5gC/(m2·a),生态系统由原来的碳汇转变为目前的碳源.这些变化与高寒草甸退化后,生态系统植物地上生物量锐减、植物生长期缩短(NEE<0的天数)、植物多样性下降、土壤含水量降低等因素密切相关.     

再生水灌溉对土壤团聚体中有机碳、氮和磷的形态及分布的影响

为了解再生水灌溉对砂质紫色土土壤有机碳、氮和磷的形态及其在不同粒级团聚体中分布的影响,比较了四川省彭州市灌溉年限分别为3a和8a的2个再生水灌溉区土壤中不同粒径团聚体中有机碳、氮和磷的分布及化学形态.结果表明,再生水灌溉区土壤有机碳、氮和磷主要分布在>2mm和2mm的大粒径团聚体所占比例下降,向较小粒径转化;>0.25mm团聚体中有机碳和氮含量显著上升,在所有5个粒级的团聚体中磷素含量都有显著提高.再生水灌溉还有利于紫色土重颗粒态有机碳和颗粒态氮的形成,且灌溉时间越长,效果越明显.在除<0.053mm的其它4个粒级团聚体中,再生水灌溉区土壤中交换态磷及钙结合态磷比例上升,而铁铝结合态磷比例下降.综上,再生水灌溉有效的改善了砂质紫色土土壤的有机碳库、氮库和磷库,长期灌溉可以减少人工施肥量.     

MBR去除水中新型微污染物PPCPs的效果及影响因素

结合MBR和新型微污染物药品和个人护理用品(PPCPs)的特性,论述了MBR对水中PPCPs的去除效果,并分析其处理过程中的主要影响因素,以期为进一步的研究应用提供理论基础及参考。     

河流流域生态安全综合评估方法

在国内外生态安全相关研究的基础上,提出了河流流域生态安全的定义. 以河流流域生态安全为研究对象,基于DPSIR(驱动力-压力-状态-影响-响应)模型框架,构建了评估指标体系,并利用多准则群体决策模型的层次分析法和熵权法确定指标权重. 以晋城市沁河流域为例,对该流域2005─2009年生态安全状况进行了综合评估. 结果表明:5年内沁河流域的生态安全综合指数从2005年的0.487升至2009年的0.641,状态从“安全”区域底部逐步提升到顶部,人均GDP增长、单位工业产值COD_Cr和NH₃-N排放强度的降低、污水处理厂投入使用和环保投资的逐年增加是影响其变化的关键因素.      

Human health impacts of exposure to metals through extreme consumption of fish from the Colombian Caribbean Sea

The health risks of metal exposure due to the high consumption of fish were assessed for a riverine population living on the Caribbean coast of Colombia. The concentrations of metals (Cd, Cr, Cu, Hg, Ni, Pb and Zn) in the edible tissues of fish were determined and used for risk assessment. The daily fish consumption of residents (n = 95) was as high as 283, 366 and 469 g/day in children (CH), women of childbearing age (WCHA) and the remaining population groups (RP), respectively. The estimation of the potential risk (HQ) indicated that there was no health risk from most of the metals, because they did not exceed their related reference doses, with values of HQ < 1. Although the concentrations of Pb and Hg were not particularly high in fish (<0.2 µg/g), their possible health effects for vulnerable groups are of great concern due to the extremely high fish intake. The Pb intake for all groups was higher than the lower confidence limit of the benchmark dose for nephrotoxicity and neurodevelopmental effects in children. The weekly intake of methylmercury was also elevated, with values approximately 3, 2 and 1.5 times the provisional tolerable weekly intake for CH, WCHA and RP, respectively. Moreover, higher Hg levels were found in top predators, whereas maximum levels for other metals were found in bottom-feeding fish. This study highlights that an accurate data of daily intake, a continuous monitoring of metals in fish and their related fish consumption advisories to protect subsistence fishing communities are recommended in a local and worldwide context.     

Hydrogeochemistry study and groundwater quality assessment in the north of Isfahan,Iran

This study presents the groundwater quality assessment in the north of Isfahan, Iran. In the study area, assessment and measurement of groundwater hydrochemical parameters such as pH, total dissolved solids (TDS), electrical conductivity (EC), sodium absorption ratio (SAR), total hardness, major cations (K⁺, Na⁺, Ca²⁺ and Mg²⁺) and major anions (Cl^?, \({\text{HCO}}_{ 3}^{ - } ,{\text{CO}}_{3}^{2 - }\) and \({\text{SO}}_{4}^{2 - }\)) concentrations were performed. Accordingly, the 66 water samples from different locations were collected during April and May 2015. Water samples collected in the field were analyzed in the laboratory for cations and anions using the standard methods. In this research, the analytical results of physiochemical parameters of groundwater were compared with the standard guideline values as recommended by the world health organization (WHO) for drinking and public health purposes. The pH values of groundwater samples varied from 7.05 to 8.95 with a mean of 7.78, indicating a neutral to slightly alkaline water. TDS values showed that 14% of the samples exceeds the desirable limit given by WHO. EC values varied from 213 to 4320 µS/cm, while 23% of the samples were more than the standard limit. Gibbs diagram had shown that 90% of the samples in the study area fall in the rock weathering zone, and this means that chemical weathering of rock-forming minerals is the main factor controlling the water chemistry in the study area. Irrigation suitability and risk assessment of groundwater are evaluated by measuring EC, %Na, SAR and RSC. According to the dominant cations and anions, five types of water were identified in the water samples: Ca-HCO₃, Ca-SO₄, Na-Cl, Na-HCO₃ and Na-SO₄. The results show that the majority of samples (30 samples, 45%) belongs to the mixed Na-SO₄ water type. Correlation analysis and principal component analysis was used to identify the relationship between ions and physicochemical parameters. Results indicated that 18 stations of the study area had the best quality and can be used for irrigation and drinking purposes in the future.     

Mercury contamination in selected foodstuffs and potential health risk assessment along the artisanal gold mining,Gilgit-Baltistan,Pakistan

This study investigates the mercury (Hg) contaminations in soil and foodstuffs along the artisanal gold mining areas, Gilgit-Baltistan Province, Pakistan. For this purpose, soils were analyzed for Hg concentrations and evaluated for the enrichment/contamination using enrichment factor or contamination factors (CF). The CF values ranged from 18.9 to 153 showed multifold higher levels of Hg contamination as compared to background or reference site. Foodstuffs including vegetables, seeds or grains and fish muscles showed Hg accumulation. Results revealed that Hg concentrations in foodstuffs were higher than the critical human health value set by European Union. The Hg in foodstuffs was consumed and, therefore, evaluated for the risk assessment indices using the daily intake (DI) and health risk index (HRI) for the exposed human population both children and adults. Results of this study revealed that cumulative HRI values through foodstuffs consumption were <1 (within safe limit), but if the current practices continued, then the Hg contamination could pose potential threat to exposed population in near future.     

Human lung injury following exposure to humic substances and humic-like substances

Among the myriad particles the human respiratory tract is exposed to, a significant number are distinctive in that they include humic substances (HS) and humic-like substances (HULIS) as organic components. HS are heterogeneous, amorphous, organic materials which are ubiquitous occurring in all terrestrial and aqueous environments. HULIS are a complex class of organic, macromolecular compounds initially extracted from atmospheric aerosol particles which share some features with HS including an aromatic, polyacidic nature. As a result of having a variety of oxygen-containing functional groups, both HS and HULIS complex metal cations, especially iron. Following particle uptake by cells resident in the lung, host iron will be sequestered by HS- and HULIS-containing particles initiating pathways of inflammation and subsequent fibrosis. It is proposed that (1) human exposures to HS and HULIS of respirable size (<10 µm diameter) are associated with inflammatory and fibrotic lung disease and (2) following retention of particles which include HS and HULIS, the mechanism of cell and tissue injury involves complexation of host iron. Human inflammatory and fibrotic lung injuries following HS and HULIS exposures may include coal workers’ pneumoconiosis, sarcoidosis, and idiopathic pulmonary fibrosis as well as diseases associated with cigarette smoking and exposures to emission and ambient air pollution particles.     

Distribution,source apportionment and health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in intertidal sediment of Asaluyeh,Persian Gulf

Surface sediment samples were collected from intertidal zone of Asaluyeh, Persian Gulf, to investigate distribution, sources and health risk of sixteen polycyclic aromatic hydrocarbons (PAHs). Total PAH concentrations ranged from 1.8 to 81.2 μg kg^?1 dry weight, which can be categorized as low level of pollution. Qualitative and quantitative assessments showed that PAHs originated from both petrogenic and pyrogenic sources with slight pyrogenic dominance. Source apportionment using principal component analysis indicated that the main sources of PAHs were fossil fuel combustion (33.59%), traffic-related PAHs (32.77%), biomass and coal combustion (18.54%) and petrogenic PAHs (9.31%). According to the results from the sediment quality guidelines, mean effects range-median quotient (M-ERM-Q) and benzo[a]pyrene toxic equivalents (BaP_eq), low negative ecological risks related to PAH compounds would occur in the intertidal zone of Asaluyeh. The total benzo[a]pyrene (BaP) toxic equivalent quotient (TEQ^carc) for carcinogenic compounds ranged from 0.01 to 7 μg kg^?1-BaP_eq, indicating low carcinogenic risk. The human health risk assessment of PAH compounds via ingestion and dermal pathways suggests low and moderate potential risk to human health, respectively.