1980—2007年我国燃煤大气汞、铅、砷排放趋势分析

基于文献调研,对1980—2007年我国汞、铅、砷3种主要燃煤大气重金属排放清单进行归纳,计算了3种重金属的逐年平均排放量,并分析排放量与燃煤量的相关性、单位煤耗大气重金属污染物排放量的变化趋势及原因. 结果表明:1980—2007年我国燃煤大气汞、铅、砷排放量与燃煤量增长趋势基本一致,均呈显著正相关(R2分别为0.911、0.971、0.996),但燃煤大气汞排放量与燃煤量间的相关性却比铅、砷排放量与燃煤量的相关性小很多,这主要是燃煤电厂对汞协同脱除能力比对铅、砷强,以及电厂汞排放所占比例较大所致. 燃煤大气汞排放量在2005年后趋于稳定,而铅、砷排放量在2000年后快速增长,年均增速均超过10%,其中电厂和工业锅炉是重金属排放的重点行业. 在燃煤量不断增长的背景下,单位煤耗的大气汞、铅排放量均呈下降趋势,其中汞排放量在2005—2007年年均降低5.0%,铅排放量在1996—2007年年均降低1.7%. 这与我国主要燃煤行业除尘、脱硫、脱硝等大气污染控制装置对重金属的协同脱除能力不断增强有密切关系.      

非贵金属催化电解无害化去除硝酸盐氮的反应机制

以Ti/Co-Fe-Cu为阴极,Ti/IrO2-RuO2为阳极组成无隔膜电解体系,对非贵金属催化电解无害化去除NO3--N的反应机制进行了实验研究和理论分析.结果表明,NO3--N阴极催化还原过程中,反应物、产物需要通过对流、扩散作用,克服电场力,迁移至目标位置;在非贵金属的催化作用下,NO3--N受还原剂攻击,逐步还原为NH4+-N;还原中间产物NO-N和NH-N直接生成N2-N的过程受抑制,产物NH4+-N难以被再度直接氧化.添加Cl-作为支持电解质,实验电解体系发生阳极析氯、Cl2水解、NH4+-N氯氧化等过程,可将NH4+-N氧化为N2-N,且出水中NO3--N、NO2--N、氯胺类浓度很低.NO3--N无害化去除的反应机制是NO3--N在催化作用下,经传质、吸脱附、电子交换过程,还原为NH4+-N,NH4+-N经由Cl-→Cl2→HOCl→Cl-电解氯氧化循环,最终生成N2-N.     

模拟酸雨对街道灰尘重金属淋溶的累积释放特征与释放模型

以泉州市交通繁忙区街道灰尘为研究对象,采用模拟酸雨动态淋溶实验和改进的BCR四步提取法研究街道灰尘中重金属元素在不同酸度(pH=3.5、4.5、5.6)模拟酸雨淋溶下的溶出规律及形态变化.结果表明,街道灰尘中重金属元素的累积释放量均随模拟酸雨pH的降低而增加,当pH值为3.5和4.5时,Cu、Pb、Mn、Ni、V、As和Co的释放过程为快速释放阶段,Cr、Zn和Fe的释放过程分为快速释放和相对平稳释放两个阶段;当pH值为5.6时,除Co、V为快速释放过程外,其余重金属都处于相对慢速的释放过程.动力学方程拟合结果表明,双常数速率方程能更好地描述上述重金属元素的累积释放特征.尘样经模拟酸雨淋溶后,弱酸可溶态中Co、Cu、Mn、Zn、Ni百分含量有所增加,Cr、Fe、Pb百分含量变化不明显;可还原态中Cr、Pb、Cu、Ni百分含量有所增加,Mn、Zn、Co百分含量有所下降;可氧化态中上述各元素的百分含量均有所降低;残渣态中除Ni、Mn百分含量有所下降外,其它元素百分含量变化均不显著.     

Response of benthic foraminifera to heavy metal contamination in marine sediments (Sicilian coasts,Mediterranean Sea)

To examine the suitability of benthic foraminifera and their test deformations as bioindicators of pollution in coastal marine environments, we studied foraminifera and metal concentrations in 72 marine sediment samples, collected from the inner shelf along the Sicilian coast (Gulfs of Palermo and Termini) and on the south-eastern coast of Lampedusa Island. These areas are characterised by different environmental conditions. On the basis of pollution sources and foraminiferal assemblages, we recognised different zones in the Gulf of Palermo. The most polluted zones showed high metal concentrations, and low diversity of benthic foraminifera with species typical of stressed environments. By contrast, the lowest polluted zones showed a high population density and the highest percentages of epiphytes. Epiphytes were abundant where a Posidonia oceanica meadow was present and decreased in the most polluted zones. Sediments of the Gulf of Termini and Lampedusa exhibited high percentages of benthic foraminifera typical of well-oxygenated waters and low concentrations of metals, with the exception of sites located near sewage outfalls and harbour areas. Furthermore, even though deformed tests are commonly known in natural stressed environmental conditions, this study shows that in the most polluted zones, benthic foraminifera were characterised by the highest percentages of deformed individuals.     

Heavy metals uptake from aqueous solutions using marine algae (Colpomenia sinuosa): kinetics and isotherms

The adsorption of copper, zinc, cobalt, lead and cadmium ions onto Colpomenia sinuosa was studied as a function of contact time, initial metal ion concentration and initial pH. In addition, desorption studies were performed. Characterisation of this adsorbent was also confirmed by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analysis. Batch adsorption experimental data were analysed using Langmuir, Freundlich and Dubinin–Raduschkevich (D–R) adsorption isotherms. The results indicated that the biosorption equilibrium was well described by both the Freudlich and D–R isotherms. Moreover, sorption kinetics was performed and it was observed that equilibrium was reached in<60 min, which could be described by the pseudo-second-order kinetic model for all heavy metals. The sorption of heavy metals onto the biomass was largely dependent on the initial solution pH. The elution efficiency for heavy metal ions desorption from C. sinuosa was determined for 0.1 M HCl, 1.0 M HCl and 1.0 M HNO₃. Desorption efficiency and also adsorption capacity were highest for Pb(II). The results indicate that C. sinuosa has great potential for the removal of heavy metals in an ecofriendly process.     

Some aspects of heavy metals contamination remediation and role of biosurfactants

Contamination by heavy metals is the result of different industrial activities. The presence of heavy metals in soil and water causes serious problems, as these materials are not biodegradable and do contaminate both biological systems and the subsoil. Biological surface-active compounds otherwise known as biosurfactants in general and rhamnolipids biosurfactants in particular have been successfully employed in the remediation of environments contaminated with heavy metal ions. The aim of the present review is to highlight potential applications of these tensioactive compounds for use in environmental heavy metals removal and bioremediation and processes involved.     

Level,pattern, and risk assessment of the selected soil trace metals in the calcareous-cultivated Vertisols

Dynamics and distribution pattern of trace metals in agricultural lands are an increasing concern due to potential risks to the environment and human health. To ascertain more knowledge of this aspect, the fractions of total and available Fe, Mn, Zn, Cu, and Cd belonging to Vertisols under intensive cultivation and adjoining uncultivated soils were investigated. The order of abundance of metals in both cultivated and uncultivated soils was Fe?>?Mn?>?Cu?>?Zn?>?Cd and Fe?>?Mn?>?Zn?>?Cu?>?Cd for both available and total fraction, respectively. A relative enrichment was observed in the value of diethylene-triamine pentaacetic acid-extractable Fe (1.2–201%), Mn (2–31%), Cu (1–40%), and Cd (21–45%) as well as total fraction of Zn (3–17%), Cu (12–32%), and Cd (42–108%) after intensive cropping, which can be contributed to repeated application of agrochemical inputs and manure over long time. The values of RI (potential ecological risk) showed that cultivation caused a low potential ecological risk (33.3% of the soil samples) to moderate potential ecological risk (66.7% of the soil samples) in the study region and that cadmium made up 88%, on average, of the RI value.     

Roe and red deer as bioindicators of heavy metals contamination in north-western Poland

The present paper examines the degree of environmental contamination in areas covered by the Natura 2000 programme, located in north-western Poland, with selected heavy metals based on their concentration in target organs of roe and red deer. Lead, cadmium, copper, iron, and zinc concentrations were determined by inductively coupled plasma–atomic emission spectrometry. Residues of lead and cadmium were found in most of the analysed samples of roe and red deer organs The concentration of cadmium in the organs of the animals studied was much higher than that of lead. The median for Pb in liver and kidneys was 0.055 and 0.092 μg/g dry weight (d.w.) in roe deer, and 0.067 and 0.081 μg/g d.w. in red deer, respectively. The median for liver and kidney cadmium was 0.770 and 6.139 μg/g d.w. in roe deer, and 0.422 and 6.365 μg/g d.w. in red deer, respectively. Our study has demonstrated that this area is laden with lead and cadmium. This is evidenced by the fact that maximum permissible levels of these elements in the organs of red and roe deer, which were used as bioindicators of environmental contamination, were exceeded.     

The gastropod Osilinus atrata as a bioindicator of Cd,Cu, Pb and Zn contamination in the coastal waters of the Canary Islands

The aim of this study was to assess the use of Osilinus atrata (Gastropoda, Mollusca) as a biomonitor of heavy metals (Cd, Cu, Pb and Zn) within the coastal zone of the Canary Islands. In general, this top-shell snail showed high intraspecific variability in its tissue metal concentrations, which decreased according to the following sequence: Cu≥Zn>Cd≥Pb. In particular, Cd and Zn concentrations were higher in males than in females, whereas Cu concentrations increased slightly with weight, and Pb concentrations decreased. Cd and Cu concentrations showed notable spatial variability; Cd concentrations were higher in the eastern islands (Alegranza, La Graciosa, Lanzarote and Fuerteventura) and La Palma, whereas Cu levels were highest in some western islands (Gran Canaria, La Gomera and El Hierro). The arrival of waters from the African coastal upwelling, the pollution of coastal waters with agricultural fertilisers and the competition for uptake between metals appear to be the likely causes within these patterns of accumulation. In conclusion, O. atrata presents a great potential as a biomonitor of heavy metals, however, more information and further studies are necessary.     

Heavy metals distribution and risk assessment in soils affected by tannery effluents

Effluents collected from tanneries in Sialkot showed considerably higher levels of heavy metals. Sodium (12 660.91 mg/L) among macronutrients and Cr (592.20 mg/L) among heavy metals were found in the highest concentrations. Effluent parameters, i.e. biological oxygen demand (BOD; 12.40), chemical oxygen demand (COD; 16.53), Cd (5.90), Cr (592.20) and Fe (18.59) were the respective times higher than Pakistan National Environmental Quality Standards and their continuous unchecked discharge into agricultural soils poses a potential risk. Mean concentrations (mg/L) of Cr (592.20), Ni (2.66), Mn (1.16), Fe (37.17), Zn (0.90), Cd (0.59) and Pb (1.18) in this study exceeded levels recorded to date from different tanning hubs in Pakistan. Factor analysis/principal components analysis (FA/PCA) for the effluent parameters resulted in six varimax factors, i.e. VF1 (salinity, electrical conductivity, total dissolved solids, chloride, phosphate, BOD and COD; including characteristic tannery effluent features), VF2 (pH, Cr and alkalinity; tanning operations), VF3 (Cd and Pb; dyeing processes), VF4 (Mn and Fe; finishing operations), VF5 (Ni; retaining processes) and VF6 (hardness, Ca and Cu; bating processes). Cluster analysis performed on metal data resulted in three clusters confirming metal–metal relations obtained either from FA/PCA or a correlation matrix. The results of this study are useful for heavy metal source apportionment, assessment of risk to peripheral soils and the future management of environments around tanneries.