Relationship between aquatic insects and heavy metals in an urban stream using multivariate techniques

In the study, the relationship between some aquatic insect species (Ephemeroptera, Plecoptera, Trichoptera and Odonata) and some heavy metals (cadmium, lead, copper, zinc, nickel, iron and manganese) and boron were assessed using data obtained from the Ankara Stream, which flows through Ankara, the capital city of Turkey and receives high organic and industrial wastes. Sampling was carried out monthly along the Ankara Stream in 1991. environmental data were used to explain biological variation using multivariate techniques provided by the program canonical correspondence analysis ordination. The ordination method canonical correspondence analysis was applied to evaluate the relationships between environmental variables and distribution of aquatic insect larvae. Data sets were classified by two way indicator species analysis. In this study, aquatic insecta communities have been shown by canonical correspondence analysis ordination as related to total hardness, pH, cadmium, lead, copper, zinc, nickel, iron, manganese and boron. Cadmium, lead, copper and boron exceeded limits of the United States Environmental Protection Agency criteria for aquatic life. Trichopteran, Dinarthrum iranicum was an indicator of two way indicator species analysis and was placed close to the arrow representing copper. Odonate, Aeschna juncea was an indicator of two way indicator species analysis in site 10 and was placed close to the arrows representing manganese, lead, and nickel. Trichopteran, Cheumatopsyche lepida and odonate, Platycnemis pennipes were indicators of two way indicator species analysis for sites 6, 7, 11, 14, 15, 18 and were placed close to the arrows representing cadmium, boron, iron and total hardness.     

Heavy metals contamination in water and sediments of an urban river in a developing country

Water and sediment samples were collected from 20 location of the Buriganga river of Bangladesh during Summer and Winter 2009 to determine the spatial distribution, seasonal and temporal variation of different heavy metal contents. Sequential extraction procedure was employed in sediment samples for the geochemical partitioning of the metals. Total trace metal content in water and sediment samples were analyzed and compared with different standard and reference values. Concentration of total chromium, lead, cadmium, zinc, copper, nickel, cobalt and arsenic in water samples were greatly exceeded the toxicity reference values in both season. Concentration of chromium, lead, copper and nickel in sediment samples were mostly higher than that of severe effect level values, at which the sediment is considered heavily polluted. On average 72 % chromium, 92 % lead, 88 % zinc, 73 % copper, 63 % nickel and 68 % of total cobalt were associated with the first three labile sequential extraction phases, which portion is readily bioavailable and might be associated with frequent negative biological effects. Enrichment factor values demonstrated that the lead, cadmium, zinc, chromium and copper in most of the sediment samples were enriched sever to very severely. The pollution load index value for the total area was as high as 21.1 in Summer and 24.6 in Winter season; while values above one indicates progressive deterioration of the sites and estuarine quality. The extent of heavy metals pollution in the Buriganga river system implies that the condition is much frightening and may severely affect the aquatic ecology of the river.     

The concentrations and distribution of mercury in aquatic ecosystem of Baihua Reservoir

1Introduction Thebiogeochemicalcycleofmercuryinaqueous systemisthekeyfactorleadingtotheexpansionof mercurypollutiononaglobalscaleandthesafetyof fishconsumers.Dissolvedgaseousmercury(DGM)e vasionisconsideredasoneofthemostimportantmer curysourcesforatmosphere.Atthesametime,this procedurewillreducetheHgburdeninthewatercol umnandmaythusdecreasemethylmercuryproduction andaccumulationinfish(Nriagu,1994).TheBaihua ReservoirissituatedinGuizhouProvince,andithas sufferedseriousmercurycontaminationfr…     

Geochemical distribution of trace metal pollutants in water and sediments of downstream of an urban river

A study was conducted to investigate the trace metal pollution of water and sediments of downstream of Tsurumi River, Yokohama, Japan. Twenty samples of water and sediments were collected from the river starting from Tokyo bay side up to the junction point of the Yagami River. Results show that the mean concentrations of chromium, cupper and nickel in water greatly exceed (>100 times) the surface water standard. The concentration of molybdenum and lead was also higher than standard values while iron and manganese was lower than that of surface water standard. The mean concentration of zinc, cupper, cadmium, lead, chromium, vanadium, bromine and iodine was 381.1, 133.0, 1.0, 40.8, 102.9, 162.0, 71.5 and 10.6 μg/g sediments, respectively and was greatly exceed the average worldwide shale concentrations and average Japanese river sediment values. However, mean concentration of arsenic, nickel and strontium was 11.0, 36.6 and 164.6 μg/g sediments, respectively which was lower than the average shale value. Other analyzed trace metals, including barium, zirconium, rubidium, yttrium, tin, antimony, cesium, lanthanum, cerium, praseodymium and neodymium were detected in river sediments; the concentration of which was close to the Japan’s river sediment average values. Pollution load index values of the sites of the studied area ranged from 1.24 to 7.65 which testify that the river sediments are polluted. The PLI value of the area was, however, high (6.53) as the concentration of trace metals like zinc, cupper, cadmium, lead and chromium were very high and were the major pollutants.     

桂林市及近郊土壤汞的分布和污染研究

通过对桂林市区及近郊表层、底层土壤汞的系统取样,测试和编图,阐明了本区土壤汞的分布规律,确定了土壤汞的污染区段和污染程度。在上述工作的基础上,结合基岩汞测量、热释汞方法和重金属元素组合分析,对土壤汞的来源、污染无比汞的赋存状态进行了初步探讨。     

Release of volatile mercury from soils and non-vascular plants

Vegetation plays a significant role in the biogeochemical cycling of mercury. This conclusion is drawn from data presented here on bioaccumulation and subsequent release of volatile mercury from non-vascular plants together with the results of previous work. There is no obvious relation between total plant Hg or soil Hg and rate of release from the plant. Heat of vaporization for Hg⁰ was calculated at 13.99 kcal/g-atom; from soil it was experimentally determined at 13.81 kcal/g-atom but from the most active vascular plant was only 9.49 kcal/g-atom.     

Heavy metal flows in aquatic systems of the Don and Kuban river deltas

This paper presents the calculated heavy metal (Fe, Mn, Zn, Ni, Cu, Cr, Co, Cd, and Pb) flows in suspended and dissolved forms in the main navigable branches of the Don and Kuban river deltas during the low-water period of 2013–2014. This work is based on the data of field studies in which water and suspended matter samples were collected and the turbidity and water discharge in deltas were measured. A quantitative estimate of heavy metal inflows into the deltas of the Don and Kuban rivers is provided. Transformation of flows of suspended and dissolved metal forms from the delta top to the sea edge is discussed. The influence of localities (Rostov-on-Don, Temryuk) on the increase in heavy metal flows downstream is shown, and the heavy metal flows in the deltas of the Don and Kuban rivers are compared.

     

Arsenic accumulation and speciation in plants from different habitats

Understanding As accumulation in plants is necessary in order to alleviate problems with As in the environment and to improve sustainable As phytotechnologies. To find suitable candidates for phytoremediation purposes and to investigate specific accumulation patterns due to growth habitat and plant groups, As accumulation in 124 plant species collected from different habitats and speciation in 6 of these plant species, was determined. The data show that submerged plants have a higher accumulation than emergent and terrestrial plants. The As concentration in terrestrial and emergent plants were correlated with the [As]_soil, while the accumulation factor correlated negatively with [As]_soil. Gymnosperms had a high [As]_shoot:[As]_root ratio. The inorganic As species, arsenate and arsenite were found in plants from all habitats and methylarsonic acid (MMA) in all but one plant species. Arsenate predominated in submerged plants. The results suggest that the habitat and the [As]_soil have a strong influence on the As accumulation in plants and that submerged plants and/or gymnosperms might be suitable for phytoremediation of As.     

城市河道淤泥特性及改良试验初探

以南京内秦淮河疏浚淤泥为例,通过土工试验、XRD和X射线荧光光谱试验等方法,研究了城市河道淤泥的物理性质、矿物成分、化学成分等特性。试验结果显示:秦淮河淤泥粘粒含量低、有机质含量极高,矿物成分主要有石英和少量粘土矿物等。为了实现淤泥的资源化处理,运用水泥、石灰无机固化材料对淤泥进行固化改良试验及改性土无侧限抗压强度试验,结果表明随着水泥掺量增加,水泥固化土由塑性破坏向脆性破坏过渡,破坏应变在1.8%~2.2%,而石灰固化土均表现为脆性破坏,且破坏应变小于水泥土,为1%左右。水泥固化土28d强度为670kPa,固化效果优于石灰,但略低于处理一般软土的固化土强度。研究结果对处置城市河道淤泥有一定参考价值。     

Assessment of the ultra-trace mercury levels in selected desert plants

Conventional methods that assessed the mercury (Hg) levels were not only an outcome of atmospheric pollution, but also the possibility of Hg contamination from the sample collection to laboratory analyses. Our studies used the direct mercury analyzer that measured Hg rapidly and precisely at ultra-trace concentrations with detection limit of 0.0015 ng g^?1 on six favored desert plants and their surrounding soil in Kuwait. Analysis revealed elevated Hg concentrations in Tamarix chinensis Lour., and Salsola imbricate Forssk., among the chosen desert plants, especially during summer than in winter, thus labeling the qualities of a bio-indicator to Hg pollution. The overall parts-wise analysis on the six selected plants showed the elevated mean Hg concentrations in the leaves (0.89 ng g^?1) followed by root (0.51 ng g^?1) and stem (0.39 ng g^?1) in the desert plants. Reasons attribute to the capability of these plant parts to absorb, accumulate, and assimilate Hg at varying concentrations. The overall mean Hg concentration was high in soil (2.24 ng g^?1) in comparison with the mean Hg concentrations in the desert plants (0.60 ng g^?1) irrespective of the two seasons. Translocation and bioaccumulation factors indicated low uptake of Hg translocation in the plant parts from the soil. Furthermore, the mean Hg concentration was found high in samples collected from Governorates (GIII) in comparison with the samples collected from other Governorates indicating the effect of pollution from various sources. The present study characterizes the selected plants as bio-indicators and also validates the impact of regional and seasonal variations to Hg pollution at ultra-trace levels in the arid ecosystem.     

Uptake of metals by plants in urban areas

In the present study, bulk contents of Ni, Zn, Cu, Pb and Mn in urban area of Tehran city are determined. Subsequently, the chemical bonds of metals with various soil fractions are brought out. Chemical partitioning studies revealed that various percentile of Ni, Zn, Cu, Pb and Mn is found in anthropogenic portion of soils. Zinc, Ni, Cu, Pb and Mn fall within “low pollution” class in accordance with index of pollution (I _POLL). The trend of anthropogenic share of studied metals in soils of Tehran is Zn (55 %) > Cu (31 %) > Ni and Pb (30 %) > Mn (12 %). The overall potential of studied plants in metal removal from soil is Salvia > Viola > Portulaca. It should be pointed out that roots have higher potential in metal removal from soil when compared with leaf and stem. Lithogenic portion of metals remains intact before and after pot analysis. Thus, phytoremediation is highly dependent on the chemical bonds of metals. Present study showed that metal contents of loosely bonded ions, sulfide bonds and organometallic bonds are reduced after 90 days of plant cultivation. The overall removal trend of studied metals is Zn (16 %) > Cu (14 %) > Ni (11 %) > Pb (7 %) > Mn (6 %). The obtained results show that the anthropogenic portion of metals is reduced after the phytoremediation practice. For instance, the initial anthropogenic portion of Zn (55 %) is changed to 39 % showing an overall reduction of about 16 %. The anthropogenic portions of Cu, Ni, Pb and Mn are also reduced by 14, 11, 7 and 6 %, respectively.     

Source apportionment and distribution of atmospheric mercury in urban Beijing,China

The concentration of gaseous elemental mercury (GEM) in the atmosphere of urban Beijing was measured from October 2003 to September 2004 to investigate the origins and spatial-temporal variations of atmospheric Hg. The mean value of Hg concentration is 17.1 ng·m-3 (n=653). The atmospheric Hg data showed spatial-temporal variations throughout the duration of our observation. The maximum GEM concentration (53.7 ng·m-3) was observed at Gucheng in the western area of urban Beijing. The GEM concentrations increased from the north to the south of the studied area, and were higher in winter than in summer. The highest and lowest monthly averages of GEM concentrations were measured to be 23.3 and 4.1 ng·m-3 in January and July, respectively. In addition, GEM concentrations are higher in the daytime than at night in Autumn and from 14 March to 15 April, but daily GEM variation showed an inverse pattern from 22 April to 22 May. In winter, two peak values of GEM concentrations occurred at 13:30 and 21:30. Daily variation of GEM concentrations in summer was the lowest in the four seasons. Mercury from coal combustion was estimated to be the main source of anthropogenic emissions in Beijing from October 2003 to September 2004. Additionally, Hg emission from natural gas burning was estimated to be another dominant source of atmospheric Hg in Beijing.     

Analysis of current directions in the bends of an ephemeral river and its geological implications

Sediment transport directions in four point bars of an ephemeral meandering river Usri, India, were measured from sedimentary structures and compared with the flow directions of the adjacent river-channel flow. As the bars were crescentic in shape, each bar has been divided into several sectors along with the adjacent river-channel bend. Vector means of sediment transport directions in each sector were computed and compared with the vector means of the flow directions of the corresponding river-channel sector. The relationship between the sediment transport direction in the bar and the water flow direction of the adjacent river-channel is sometimes divergent and sometimes convergent. However, the difference between the vector means of the sediment transport direction in the bar and the flow direction of the adjacent river-channel water is subtle. Hence, it can be concluded that the sediment transport direction in the bar is parallel to the flow direction of the adjacent river-channel water. Therefore, the result of the present study implies reconstructing the paleo-river channel course.     

Nitrogen and phosphorus removal and physiological response in aquatic plants under aeration conditions

To analyze the variation of physiological responses between Nymphaea tetragona Georgi. and Pontederia cordata L. and the water qualities under aeration conditions, the selected plants were cultivated in 12 purifying-tanks (aeration, non aeration), to treat heavily polluted river water. The characteristics of both plants were investigated, which included contents of chlorophyll and soluble protein, activities of peroxidase and catalase, accumulations of nitrogen and phosphorus, densities of tillers and roots, lengths of roots, culms and leaves, biomass of roots and shoots. The water qualities were analyzed correspondingly. Results indicated that aeration affected morphological and physiological characteristics of the plants and the water qualities and effects became more significant on N. tetragona than P. cordata. Biomass and length of roots, culms and leaves under the non aeration conditions exceeded that under the aeration conditions. Aeration contributed to the activities increase of peroxidase and catalase of the roots and the contents decrease of chlorophyll and soluble protein of the leaves. Nitrogen and phosphorus contents of the roots, culms and leaves increased under the non aeration conditions. Aeration resulted in tillers and roots densities of N. tetragona decreased, while they increased for P. cordata. Total phosphorus and soluble phosphorus removals decreased 8.42 % and 8.05 % in the tank with N. tetragona under the aeration conditions. In the tank with P. cordata, total nitrogen and NH₄+ ?N removals increased 14.44 % and 16.06 % under the aeration conditions. This work provided valuable data for optimizing the plants allocation in the ecological restoration project of the polluted water.     

Interactions of mercury with different molecular weight fractions of humic substances in aquatic systems

Interactions of mercury (Hg) with different molecular weight fractions of humic substances (HS) play an important role in controlling distribution, diffusion, speciation, and bioavailability of Hg in natural systems. This study suggests that Hg prefers to associate with higher molecular weight fractions of HS and this association particularly predominates at low pH and high ionic strengths of the medium. The concentrations of aggregated HS (with higher molecular weight) become high at lower pH (acidic condition) and high ionic strength. Molecular weight of HS gradually decreases with the increasing pH (basic condition) and low ionic strength of the medium. The disaggregation property of HS which involves the release of monomers from the surface of the aggregates produces HSs of different intermediate molecular weight with different Hg complexing capacity. Distribution of Hg in different molecular weight fractions of HS is dependent on aggregational and disaggregational properties of HS in aquatic medium. Association of Hg with high molecular weight fraction of HS may alter distribution and bioavailability of Hg in a system as the bioreactivity of organic matter decrease along a continuum of size in aquatic medium.     

Quantifying baseflow and water-quality impacts from a gravel-dominated alluvial aquifer in an urban reach of a large Canadian river

Groundwater discharge and non-point source (NPS) loading were evaluated along an urban reach of an eastern-slopes Rocky Mountains river (Bow River, Canada) to understand sources of water-quality impacts and baseflow. The discharge did not increase measurably over a 16-km reach. Groundwater in the river-connected alluvial aquifer was a mixture of river and prairie groundwater, with elevated chloride concentrations (average 379 mg L^–1) from road salt. Alluvial groundwater was the major NPS of chloride discharging to the river. Although the mass-flux based estimates of groundwater discharge were small (mean 0.02 m³ s^–1 km^–1, SD = 0.04 m³ s^–1 km^–1, n?=?30), the associated chloride mass flux over 16 km was significant (equivalent to that discharged from the city’s largest wastewater-treatment-plant effluent). Although local groundwater baseflow was previously thought to contribute significantly to overwinter baseflow in this reach, little contribution was measured in this study. Low baseflow generation is consistent with long-term river discharge data that show almost all of the baseflow generation occurs in the Rocky Mountain reach. Thus, local watershed areas are important for water-quality protection, but climate change in the headwaters is most salient to long-term flow.     

汞等重金属元素在黄浦江中迁移富集研究

为了探讨生物膜对重金属元素的富集,以及生物膜在水-沉积物交换过程中的影响和贡献,研究了生物膜和沉积物对于汞等重金属的吸附以及吸附前后汞形态的变化.结果表明沉积物中的汞和大部分重金属元素以残渣态为主,可交换态、有机质结合态、碳酸盐结合态百分含量相对较少.生物膜中有机质含量很高,生长时间,光照,季节都是影响生物膜中重金属元素含量的重要因素.可以推断,光照越强,温度越高,生长时间越长,生物膜中重金属元素含量越高.