Spatial variability characteristics and environmental effects of heavy metals in surface riparian soils and surface sediments of Qinggeda Lake

Abstract

One hundred and twenty topsoil (0–20?cm layer) samples and 45 surface sediment samples were collected from the riparian area and bottom of Qinggeda Lake. The content of Pb, Cu, Cr, Ni, Zn, Mn, V, and As were determined to reveal the distribution characteristics and explore the spatial dependency relationship between environmental factors (pH, conductivity, and organic matter) and heavy metals using Kriging interpolation and the geographical weighted regression model. Results showed as follows: (1) The average contents of Pb, Cu, Cr, Ni, Zn, V, and As did not exceed the Standard of National Soil Environmental Quality. However, Cu, Cr, and V were higher than the Xinjiang soil background. (2) The target elements in the surface sediments of the lake showed a decreasing trend from the center of the lake to the shore. Also, the heavy metal concentrations in the eastern part of the lake shore were significantly higher than those in other areas, and the highest concentrations appeared in the paddy field. (3) The effects of the eight heavy metals on pH, conductivity, and organic matter displayed significant spatial nonstationary characteristics. Cr, As, Cu, and Zn are the primary factors that affect environmental characteristics such as pH, conductivity, and organic matter content.     

Diversity and Above-Ground Biomass Patterns of Vascular Flora Induced by Flooding in the Drawdown Area of China's Three Gorges Reservoir

Hydrological alternation can dramatically influence riparian environments and shape riparian vegetation zonation. However, it was difficult to predict the status in the drawdown area of the Three Gorges Reservoir (TGR), because the hydrological regime created by the dam involves both short periods of summer flooding and long-term winter impoundment for half a year. In order to examine the effects of hydrological alternation on plant diversity and biomass in the drawdown area of TGR, twelve sites distributed along the length of the drawdown area of TGR were chosen to explore the lateral pattern of plant diversity and above-ground biomass at the ends of growing seasons in 2009 and 2010. We recorded 175 vascular plant species in 2009 and 127 in 2010, indicating that a significant loss of vascular flora in the drawdown area of TGR resulted from the new hydrological regimes. Cynodon dactylon and Cyperus rotundus had high tolerance to short periods of summer flooding and long-term winter flooding. Almost half of the remnant species were annuals. Species richness, Shannon-Wiener Index and above-ground biomass of vegetation exhibited an increasing pattern along the elevation gradient, being greater at higher elevations subjected to lower submergence stress. Plant diversity, above-ground biomass and species distribution were significantly influenced by the duration of submergence relative to elevation in both summer and previous winter. Several million tonnes of vegetation would be accumulated on the drawdown area of TGR in every summer and some adverse environmental problems may be introduced when it was submerged in winter. We conclude that vascular flora biodiversity in the drawdown area of TGR has dramatically declined after the impoundment to full capacity. The new hydrological condition, characterized by long-term winter flooding and short periods of summer flooding, determined vegetation biodiversity and above-ground biomass patterns along the elevation gradient in the drawdown area.     

Distribution,bioavailability, and potential risk assessment of the metals in tributary sediments of Three Gorges Reservoir: The impact of water impoundment

To investigate the impact of water impoundment on the metal contamination in sediments cores from the three tributaries of Three Gorges Reservoir (TGR), the concentrations, distribution, bioavailability, and potential risk of eight trace metals between summer and winter were analyzed using sequential analysis. The mean contents of all studied metals were higher than the geochemical background value, and were higher in summer than in winter. The results of the partitioning study indicated that Cr and Ni prevailed in the residual fraction, while a small proportion was found in the easily soluble fractions. Cu and Zn were distributed mainly in the residual and reducible fraction, while Cd and Pb were predominantly associated with non-residual fractions. These observations suggested that the most easily mobilized metals in the study area were Cd and Pb. The mean enrichment factors (EF) of Cu, Zn, Cd and Hg were higher than 1.5, revealing the potential anthropogenic inputs, whilst the EF of other metals remained within the range of natural variability. The positive correlation between non-residual Cu, Zn and Cd and their EF values further indicated that anthropogenic inputs were the potentially major contributor for the enrichment of Cu, Zn and Cd in TGR sediments. The results evaluated by both potential ecological risk index and modified risk assessment code (mRAC) of all sampling sites demonstrated the relatively high potential risk of sediment contamination effect in TGR.     

Effects of mine effluent on uptake of Co,Ni, Cu,As, Zn,Cd, Cr and Pb by aquatic macrophytes

Concentrations of Ni, Co, Cu, Pb, Zn, Cd, Cr and As were determined in aquatic sediments, water and macrophytes collected from a fluvial system, contaminated by mine effluents. Myriophyllum verticillatum collected in May below the trace element point source accumulated 169 µg/g of Ni, 860 µg/g of Co, 37 µg/g of Cu, 31 µg/g of Pb, 92 µg/g of Zn, 6.9 µg/g of Cr and 1,200 µg/g of As (concentrations in dry weight). The aquatic macrophytes Nymphaea odoratae and Pontederia cordata accumulated the investigated trace elements to a much lesser extent. The concentrations of trace elements in Myriophyllum verticillatum decreased from May to August. Correlations were found between the concentrations of total Ni, Co and Cu in the bottom sediment and in the submerged macrophytes. However, there was no correlation between the amounts of these trace elements extractable by 0.5 N HCl from the sediments and the concentrations in the macrophytes.     

调水调沙工程黄河口近岸沉积物重金属和砷含量的空间分布及其生态风险评估

为了明确调水调沙工程长期影响下黄河口近岸沉积物中重金属含量的分布特征及其生态风险,基于2012年黄河口近岸27个站位的表层沉积物样品,通过ICP-MS测定重金属(Zn、Cr、Ni、Pb、Cu、Cd)和砷(As)含量,并运用潜在生态风险指数法(RI)对其进行生态风险评估。结果表明:近岸沉积物中重金属和As的平均含量表现为AsZnCrNiPbCuCd。Cr、Ni、Cu和Pb四种元素的分布规律较为一致,整体呈现出近岸和近黄河口高而远离河口和岸线低的空间分异特征。Ni、Cu、Pb、Zn与粘土均呈极显著或显著正相关(P0.01或P0.05),而Cd、Cr和As与其相关性均未达到显著水平(P0.05)。近岸沉积物中6种重金属和As的平均单项潜在生态风险指数大小顺序整体表现为CdAsNiPbCuCrZn。就潜在生态风险(RI)而言,研究区域18.52%的站位属轻微生态危害,70.07%的站位属中等生态危害,7.41%的站位属强生态危害,Cd和As是造成危害的两种主要元素。近岸沉积物中重金属和As的来源复杂且多样,主要是由于农业化肥使用、海上石油开采和泄漏、化石燃料燃烧以及河口污染物输入所致。对比研究发现,随着调水调沙工程的长期实施,除Cd和As外沉积物中其他重金属含量均呈下降趋势,说明二者的生态风险将会随调水调沙的长期实施呈增加趋势,而其他重金属的生态风险将呈降低趋势,故未来应重点关注近岸沉积物中Cd和As的生态毒理风险。     

Spatial distribution of heavy metals in sediments from the Gulf of Paria, Trinidad

The Gulf of Paria receives heavy metal input from urban runoff, industrial and agricultural activity, sewage and domestic wastes: both from the west coast and from inland areas of Trinidad. Non-residual concentrations of nine metals, as well as total mercury concentrations, were used to determine spatial distributions of heavy metals in sediments in the Gulf of Paria. Surficial sediment samples were collected at 37 stations, which included the mouths of 11 major rivers that flow into the Gulf of Paria. Stations were sampled twice during the wet season (July 1998 and November/ December 1998) and twice during the dry season (March 1999 and April 1999). Sediments were analyzed for aluminium (Al), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), nickel (Ni), zinc (Zn) and mercury (Hg). Total Organic Carbon (TOC) and grain size analyses were also performed on the sediments. Principal component analysis showed that sediments from river mouths subject to greatest land use and anthropogenic input, were distinct from other sediments in the Gulf of Paria. This was due to higher Pb, Zn, Cu and Hg concentrations (3.53-73.30 microg g(-1), 45.8-313.9 microg g(-1), 8.43-39.71 microg g(-1) and 0.03-0.10 microg g(-1), respectively). Sediments further from the coast were also distinct due to their higher Al, Fe, Cr and Mn concentrations (1.37-3.16 mg g(-1), 9.51-18.91 mg g(-1) , 17.22-28.41 microg g(-1) and 323.6-1,564.2 microg g(-1), respectively). Cd and Pb were higher in the wet season while Ni was higher in the dry season. Pb, Zn, Cu and Hg were correlated with each other and with TOC. Correlation was also observed between Al, Fe, Cr, Mn and Ni. Al, Fe, Cr and Mn were correlated with percentage clay in sediments. The results suggest that Pb, Zn, Cu and Hg are preferentially removed by organic matter, which settles at the river-mouths, while Al, Fe, Cr, Mn, and Ni become associated with clay minerals and are transported away from the coast.     

Concentrations and ecological risks of metals in surface sediments of some coastal creeks in the Niger Delta,Nigeria

The concentrations of nine metals were measured by atomic absorption spectrophotometry in surface sediments of three coastal creeks, namely, the Ifie, Egbokodo and Ubeji creeks, in the Niger Delta of Nigeria, from August 2012 to January 2013. The aim of the study was to provide information on the spatial and seasonal distribution patterns, degree of contamination, and ecological risks of metals in these sediments. The mean concentrations of the nine metals in these creek sediments ranged from 0.30 to 3.20?mg kg^?1 Cd; 10.7 to 24.7?mg kg^?1 Pb, 125 to 466?mg kg^?1 Cr; 3.1.10 to 14.9?mg kg^?1 Cu; 4.7 to 14.3?mg kg^?1 Co; 61.1 to 115?mg kg^?1 Ni; 106 to 183?mg kg^?1 Mn; 52.0 to 170?mg kg^?1 Zn and 5 469 to 20 639?mg kg^?1 Fe. In general, the metal concentrations were higher in the dry season than the wet season, except for Cr. The concentrations of Cd, Cr, Ni and Zn were above their regulatory control limits in sediment as specified by the Nigerian Regulatory Authority and Cd was identified as the main ecological risk factor. The enrichment factors for the studied metals followed the order: Cd > Cr > Ni > Zn > Pb > Co > Mn > Cu. The average multiple pollution index values indicated that these sediments were severely polluted with significant inputs from Cd, Ni and Cr.     

Soil Heavy Metal Pollution Assessment Near the Largest Landfill of China

To assess the extent and potential hazards of heavy metal pollution at Shanghai Laogang Landfill, the largest landfill in China, surface soil samples were collected near the landfill and concentrations of Cu, Zn, Cd, Pb, and Cr were determined. The results revealed that the concentrations of heavy metals, except Pb, were higher in the surface soil near the landfill than in the background soil. Principal component analysis and hierarchical cluster analysis suggested that the enrichment of Cu in soil was probably related to agricultural activities and Cd and Pb to landfill leachates, whereas Zn and Cr concentrations were probably controlled by soil matrix characteristics. The pollution indices (PIs) of the metals were: Cd > Cu > Cr > Zn > Pb. Among the five measured metals, Cd showed the largest toxic response and might cause higher ecological hazards than other metals. The integrated potential eco-risk index (RI) of the five metals ranged from 26.0 to 104.9, suggesting a low-level eco-risk potential. This study indicated the accumulations of Cu, Zn, Cd, Pb, and Cr did not reach high pollution levels, and therefore posed a low eco-risk potential in surface soil near the landfill.     

山东省部分水岸带土壤重金属含量及污染评价

为了解山东省水岸带土壤重金属的含量特征和污染状况,于2010年9月—10月采集了39个水岸带土壤样品,分析了土壤中Cr、Co、Ni、Cu、Zn、Cd、Pb和Hg的含量以及土壤的pH值、粒度和有机质,采用单因子指数法、综合指数法和潜在生态危害指数法对水岸带土壤重金属污染进行了评价,并利用相关分析和聚类分析对其来源进行了初步的解析。结果表明：水岸带土壤的pH值为5.67—8.66,主要呈碱性;有机质的平均含量为9.39 g/kg,土壤粒度主要以砂粒和粉粒为主,其平均体积百分比分别为50.33%和38.48%,平均粒径为89.69 μm;Cr、Co、Ni、Cu、Zn、Cd、Pb和Hg的平均含量为53.03 mg/kg、10.33 mg/kg、24.96 mg/kg、18.38 mg/kg、56.13 mg/kg、0.142 mg/kg、22.48 mg/kg和0.020 mg/kg。各水岸带土壤重金属的含量均符合《土壤环境质量标准》（GB15618-1995）二级标准。以山东省土壤元素背景值为评价标准,水岸带土壤重金属总体表现为轻度污染和轻微生态风险,其中Cd和Hg是主要的污染因子,其对潜在生态危害指数的平均贡献率分别为46.8% 和33.6%。洙赵新河、廖河、门楼水库和东平湖水岸带土壤重金属污染及潜在生态危害明显高于其他水源地。源解析的结果表明：水岸带土壤重金属的含量受自然源和人为源的双重影响,人为源主要包括地表径流、工业废气、垃圾和交通运输等。     

Assessment of heavy metal pollution and ecological risk in marine sediments (A case study: Persian Gulf)

This study was made to determine the pollution status and potential ecological risk of heavy metals in sediment of Persian Gulf. Surface sediments were collected seasonally by Peterson grab, and the concentrations of heavy metals were measured by using inductively coupled plasma–optical emission spectrometry (ICP–OES). The range concentrations obtained in mg/kg were 10,800–22,400 for Fe, 5.32–10.12 for Pb, 24.63–42.38 for Ni, 22.52–39.46 for Cu, and 31.64–47.20 for Cr. The concentrations of Pb, Ni, Cu, and Cr have been found lower than the Interim Sediment Quality Guidelines and probable effect level values suggesting that heavy metal contents in sediments from area of study would not be expected to cause adverse biological effects on the biota. The obtained enrichment factor values for various metals were between minimal enrichment (Pb = 0.5) and extremely enrichment (Cu = 3.11). The values of I_geo for Pb, Ni, Cu, and Cr were characterized under no pollution (0). The highest value of potential ecological risk index (RI) (8.36) was observed at St. 4 while the lowest value (5.25) was detected at station 6. Based on potential ecological RI, the Persian Gulf had low ecological risk.     

Multivariate analysis of heavy metal and nutrient concentrations in sediments of Taihu Lake, China*

Taihu Lake is one of the largest freshwater lakes in China. The Lake is very shallow with a mean depth of 1.9 m and an area of 2428 km². Nutrient concentrations (Org-C, Tot-N and Tot-P) and heavy metal concentrations (Ag, As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sr, Zn, etc.) in the lake's surface sediments were sampled at 13 locations. This was done to determine if industrialized areas along the lake's coastline were impacting the nutrient and heavy metal distribution of the lake's surface sediments. Principal Component Analysis (PCA) was used to assess the degree of contamination and spatial distribution of heavy metals and nutrients in different areas of Taihu Lake.A distinctive spatial distribution of heavy metals and nutrients was observed. Sediments from a large embayment of Taihu Lake called Lake Wulihu had significantly higher nutrient concentrations (Org-C, 2.05–3.83%; Tot-N, 0.28–0.54%; Tot-P, 0.10–0.33%) than any other area of Taihu Lake. These high nutrient levels were associated with the input of untreated domestic sewage from the large (circa one million people) City of Wuxi, which discharges its effluents into the Liangxi River. As a result, Lake Wulihu is the most eutrophic area of Taihu Lake. The nearby Meiliang Bay suffered from the worst heavy metal contamination in Taihu Lake (e.g. As, 64.0; Ag, 4.2; Cd, 0.93; Co, 14.2; Cr, 155.0; Cu, 144.0; Hg, 0.25; Ni, 79.8; Pb, 143.0 and Zn, 471 mg kg^–1). These high heavy metal concentrations were ascribed to the discharge of untreated and partially treated industrial waste water from Changzhou and Wujin via the Zhihugang River. Surface sediment samples from the east basin of Taihu Lake were characterized by high Org-C (1.0–2.3%) and Tot-N (0.18–0.37%) and low Tot-P (0.048–0.056%) concentrations. It is likely that macrophytes removal accounts for a major reduction of phosphorus in the sediments of the east basin of Taihu Lake.     

Distribution and Contamination Status of Trace Metals in the Mediterranean Coastal Sediments,Egypt

Trace metals concentrations in sediments from the Egyptian Mediterranean coast were determined to evaluate the levels of contamination. The highest concentrations of metals were generally found in the middle region of the coast. Sediment pollution assessment was carried out using Enrichment Factor (EF), Geoaccumulation Factor (Igeo), Contamination Factor (CF), Modified Degree of Contamination (mCd), and Pollution Load Index (PLI). Association of adverse effects to aquatic life was determined using the classification of sediments according to three sets of sediment quality guidelines. The mean EF values were found to fall in the following sequence: Cr > Pb > Ni > Zn > Cu > Mn. The results demonstrated that the EF of metals in the sediments of the middle region was lower than those recorded in the western region and Rafah Station at the eastern region; the difference in the EF levels was significantly correlated with Fe concentrations along the study area. Based on the average Igeo of target elements, the Egyptian Mediterranean coast could be considered not polluted with Cr, Cu, Mn, Ni, Pb, and Zn (Igeo ≤ 0). The modified degree of contamination was >1.5, indicating zero to very low contamination. The calculated PLI were less than 1, indicating only baseline levels of pollution. There were small differences between the results obtained with the three used SQGs. Highly significant correlations were found between the concentrations of Fe, Mn, Co, Cr, and Ni, suggesting similar sources and/or similar geochemical processes controlling the occurrence of these metals in the sediments.     

Toxicity of metal polluted sediments to Daphnia magna and Tubifex tubifex

Sediments from four lakes polluted by effuents from steel industries and from two reference lakes were investigated. The sediments contained elevated concentrations of oil, Pb, Cd, Hg, Zn, Ni and Cr in different combinations. The toxicity of the polluted sediments to Daphnia was much higher than reported elsewhere (24-h LC50 0.5–1.5 vol%). Tubifex survived more than 3 months in the polluted sediments, but growth and reproduction were inhibited.     

Characterization of Heavy Metal Fractions in Agricultural Soils by Sequential Extraction Procedure: The Relationship Between Soil Properties and Heavy Metal Fractions

The present research was conducted to determine heavy metals in agricultural soils from Çanakkale, Turkey, using a sequential extraction procedure (acid soluble, reducible, oxidizable, and residual) as proposed by the Community Bureau of Reference (BCR) of the European Commission. Soil samples were taken from 12 different cultivated sites and analyzed for Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn concentrations. The results revealed an order of Mn > Cd > Pb > Co > Ni > Cu > Zn > Cr for the heavy metals based on the sum of the first three fractions (acid soluble + reducible + oxidizable). The relationships between soil properties and each metal fraction were identified through Pearsons's correlation analysis. Hierarchical cluster analysis was performed to determine the behaviors and similarities of metals in each fraction. While Mn, Pb, and Zn exhibited subjective behaviors in the acid-soluble fraction, Cd, Co, Cu, Cr, and Ni exhibited similar behaviors with each other.     

Riparian vegetation’s responses to the new hydrological regimes from the Three Gorges Project: Clues to revegetation in reservoir water-level-fluctuation zone

The new hydrological regime brought about by the Three Gorges Project is the absolute opposite of the natural flood rhythms of the Yangtze River. Flooding timing, duration, frequency, rate of change and magnitude in the Three Gorges Reservoir (TGR), as important factors in affecting riparian vegetation, are completely different from the natural Yangtze Rivers’. The riparian vegetation plays important roles in stabilizing riverbanks, maintaining local biodiversity and improving water quality. Pre-dam and postdam riparian vegetations along the Yangtze River basin in the Three Gorges Reservoir Area (TGRA) were investigated in 2001 and 2009, respectively. The investigation of pre-dam riparian vegetation in 2001 showed that about 405 vascular plant species belonging to 240 genera of 83 families were distributed in the natural water-level-fluctuation zone (WLFZ) of the Yangtze River. However, only 231 vascular plant species belonging to 169 genera of 61 families were found in the WFLZ of the TGR in 2009. The changes in riparian vegetation resulted in the formation of a bald WLFZ with a 30 m magnitude in the TGRA. Although certain perennial species could be repeatedly detected in both field surveys, these are unsuitable for revegetation in the WFLZ of the TGR. This unsuitability is due to their survival via seed germination, and death in subsequent winter flooding. We propose a list of local plants that may be used to recover and re-establish riparian vegetation in the WFLZ of the TGR. We suggest that numerous physiological experiments be performed to assess how the adaptable mechanisms of riparian plants from the TGRA will respond to winter flooding. Endangered wetland shrub species such as Rhamnus tzekweiensis and Buxus ichangensis, which are confined to the riverbanks of the Yangtze River in the TGRA, should be conserved.     

Metal concentrations in urban riparian sediments along an urbanization gradient

Urbanization impacts fluvial systems via a combination of changes in sediment chemistry and basin hydrology. While chemical changes in urban soils have been well characterized, similar surveys of riparian sediments in urbanized areas are rare. Metal concentrations were measured in sediments collected from riparian areas across the urbanization gradient in Baltimore, MD. Average metal concentrations are similar to those observed in other regional studies. Two important spatial patterns are evident in the data. First, calcium concentrations double across the urbanization gradient, regardless of changes in underlying geochemistry at the boundary between the Eastern US Piedmont and Coastal Plain physiographic provinces. Alkali-earth metal ratios indicate that the additional Ca is very pure and possibly arises from cement common to urban systems. Second, hot spots of trace metals typically associated with urban systems (e.g., Cu, Zn, and Pb) occur in areas that have been artificially filled to create additional real estate in high land value areas. Together, these data indicate that riparian sediments exhibit unexpected patterns of metal contamination. If these sediments are remobilized, during events such as droughts or floods, this contamination may perpetuate legacy impacts to ecosystem health from a history of fluvial contamination.     

Heavy metals in water,sediments, fish and plants of river Hindon,U.P., India

We analysed the concentrations of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in the water, sediments, fish and plants of the River Hindon, U.P., India, at seven sampling stations, in the year 1982. Considerable variation in concentration between water, sediments, fish and plants were noted. The concentration in the water was in the order Fe > Zn > Cr > Mn > Cu > Pb > Ni > Co > Cd, in the sediments, Fe > Mn > Zn > Ni > Cr > - Co > Cu > Pb > Cd; in a fish (Heteropnuestes fossilis) Fe > Zn > Mn > Pb > Ni > Co > Cu > Cd > Cr, and in a plant (Eicchornia crassipes) Fe > Mn > Zn > Ni > Cu > Cr > Pb > Co > Cd.     

Heavy metals contamination and accumulation in submerged macrophytes in an urban river in China

Deteriorating urban water quality has attracted considerable attention in China. We investigated the contamination levels and distribution of heavy metals (As, Cd, Cu, Ni, Pb, and Zn) in Yuxi River water and sediments, and assessed the heavy metal accumulation capability of five species of submerged macrophytes: Vallisneria natans (Lour.) Hara, Potamogeton pectinatus L., Hydrilla verticillata (L. f.) Royle, Myriophyllum spicatum L., and Potamogeton crispus L. Samples were collected from upstream and downstream locations in different season. The results showed that the levels of heavy metals in the downstream areas were higher than in the upstream areas. Heavy metal concentrations in the river water during the dry seasons were higher than those during the rainy seasons, and the opposite results appeared in sediments and submerged macrophytes. In general, the river was slightly contaminated by heavy metals, and the concentrations of Pb and Ni in this river should serve as a warning, while Cd and Zn pollution in the sediments desperately needs to be removed. Furthermore, Potamogeton pectinatus L. showed a higher accumulation capacity for these metals among the five native submerged macrophytes and could be defined as a hyperaccumulator for Cd. Therefore, the potential use of native aquatic plants in contaminated rivers is worth further exploration.     

河流岸带湿地沉积物重金属分布对植被物种多样性和底栖动物群落特征的影响

河流岸带湿地栖息地完整性对河流水环境、水生态和水文的安全与健康具有重要意义,为探究河流岸带湿地表层沉积物重金属分布特征及其对植被和底栖动物的影响,对滦河干流上中下游河段表层沉积物、植物群落和底栖动物调查分析,采用生物毒性效应系数法和综合潜在生态风险指数法评价沉积物重金属污染特征,采用植被物种多样性指数和底栖动物完整性指数评价滦河植物和底栖动物群落特征,探究岸带湿地沉积物重金属空间分布与植被及底栖动物群落特征之间关系。结果表明,滦河表层沉积物总体呈清洁水平,但不同河段重金属空间分布差异较大,下游重金属生态危害系数和潜在生态风险指数高于上中游。湿地物种调查共识别维管束植物219种,大型无脊椎底栖动物105种,综合评价结果表明下游植物群落物种多样性和底栖动物群落完整性低于上中游。滦河下游岸带湿地沉积物重金属对生物群落具有生物毒性和潜在的生态风险,降低了植被物种多样性和底栖动物群落完整性。大型底栖动物完整性指数能够综合反映底栖动物群落结构特征变化,对河岸带湿地生态健康评价和监测具有重要意义。     

Metal accumulation in two contiguous eutrophic peri-urban lakes,Chivero and Manyame,Zimbabwe

Concentrations of aluminium, cadmium, chromium, cobalt, copper, iron, lead, nickel and zinc were determined in surface water, benthic sediments, and the gills, liver and stomach muscle tissues of Oreochromis niloticus and Clarias gariepinus in peri-urban lakes Chivero and Manyame, Zimbabwe. Five sites were sampled in each lake once per month in November 2015, February, May, August and November 2016. Pollution load index detected no metal contamination, whereas the geo-accumulation index reflected heavy to extreme sediment pollution, with Fe, Cd, Zn, Cr, Ni and Cu present in both lakes. Significant spatial temporal variations were detected for Al, Cr, Cu and Pb across sites within and between the two lakes. High Fe, Al and Cr concentrations in water and sediments in lakes Chivero and Manyame derive from geogenic background sources in addition to anthropogenic loads and intensity. Elevated concentrations of Al, Pb, Cu, Cd, Fe and Zn detected in gills, liver and stomach tissue of catfish corroborate concentrations in water and sediments, and pose the highest ecological and health risk for hydrobionts in lakes Chivero and Manyame. Contiguity of peri-urban lakes exposes them to similar threats, necessitating creative water management strategies, which ensure ecological continuity.