Background Values,Distribution and Contamination of Metals in the Sediments of the Pontevedra Ria (NW Spain)

Thirty-seven surface sediment samples were taken in the Pontevedra Ria (NW Iberian Peninsula), and metal concentrations (Cd, Co, Cr, Cu, Fe, Ni, Pb, and Zn) and organic/inorganic parameters were determined in order to obtain a mapping of their distribution, background values and the status of contamination. Background values were obtained from Metal/Fe ratios obtained by regression lines using “clean” stations. Contamination was assessed by the use of normalized enrichment factors (NEF). The middle and outer parts of the ria, mostly influenced by oceanic water and scarce anthropogenic activities, showed a low/null contamination (NEF ～ 1) for all the metals studied. However, the inner part of the ria, where most of the anthropogenic (urban and industrial) activities are located, showed a significant enrichment for Zn, Cu, and Pb, with NEF up to 5.2, 18, and 3.4, respectively. The rest of the metals were not significantly affected. Due to the hydrographic characteristics of the rias coastal systems, contamination sources are generally located well inland but in the high salinity region. Therefore rapid flocculation and accumulation of metal contaminants in sediments is favored close to their emission sources. Cadmium also showed a significant enrichment, strongly influenced by the presence of organic-rich sediments rather than contamination from point-sources. In the estuarine part of the ria, a significant enrichment was found for Cd, Cu, and Zn. However, it is unclear whether this is due to contamination by these two metals in the area or simply due to a difference in the lithogenic composition of the riverine sediments compared to the ria sediments.     

The role of bivalve molluscs as tools in estuarine sediment toxicity testing: a review

Estuarine sediments frequently are repositories and therefore potential sources of anthropogenic contaminants. Many organic and metallic chemical compounds released into aquatic systems bind to particulates and so accumulate in the sediments, thus, sediments become repositories of contaminants in estuaries. These may also cause contamination through diffusion of porewater, resuspension of particulates and dispersal of benthic fauna. There is a need to assess the biological affects of these anthropogenic contaminants because they may be toxic to infauna and bottomfish. Sediment toxicity bioassays are a means for carrying out such an assessment and primarily provide data on toxicity by measuring the effects on the test organism. Existing sediment toxicity bioassays rely on a battery of aquatic toxicity tests, which are based on the extraction of pore water, and elutriate from sediments and then subjecting these sediment phases to toxicity testing regimes. Two estuarine bivalve molluscs, Scrobicularia plana and Tapes semidecussatus were used to assess the ecotoxicity of field-collected sediments from estuarine and coastal areas around the Irish and English Coast over a 3-year study period. A variety of endpoints were measured during the study including survival in air, behaviour, animal condition, biochemistry, soft tissue metal concentrations, lysosomal membrane integrity and histopathology. Of these endpoints, the most sensitive were survival, survival in air, lysosomal membrane integrity, behaviour and histopathology.     

Temporal distribution,source apportionment,and pollution assessment of metals in the sediments of Beas river,India

Metal pollution in the fluvial sediments of the rivers has become a severe problem throughout the world. Lower valleys with agricultural land are usually receiving diverse contaminants from various sources that are characterized by constant, bioaccumulative and harmful contaminants. One example is of the Beas river (India) which shows the distribution, contamination, and pollution status of metals in the sediments. In the present study, a cluster analysis and principal component analysis were conducted to assess the impact of anthropogenic activities in sediment metals. Results of contamination factor indicate that there is low contamination, whereas enrichment factor showed that 28.5% metals showed significant pollution during pre-monsoon season, 42.8% metals showed moderate to high pollution during post-monsoon season, and 42.8% metals showed moderate to extreme pollution during the winter season. Pollution index and modified pollution index showed that sediments in the winter season are slightly and critically polluted. The ecological risk factors indicate that 23.8% metals posed moderate to high ecological risk in the sediments.     

Impact of bioavailable heavy metals on bacterial activities in coastal marine sediments

Total heavy metal concentrations in marine sediments are not sufficient to reliably predict detrimental biological effects. Here we provide evidence that only bioavailable heavy metals have a significant impact on benthic microbial loop functioning. Sediment samples collected along 250 km of the Apulian coast (Mediterranean Sea) were analysed for total and bioavailable heavy metals (Cr, Cd, Pb and Cu), organic matter content, bacterial abundance, biomass and carbon production and -glucosidase activity. Sampling strategy was specifically designed to cover a wide range of environmental conditions and types of anthropogenic influences. Total heavy metal concentrations in the sediments were tightly coupled with organic matter content, whereas bioavailable heavy metal concentrations displayed an opposite pattern. Bioavailable Cr concentrations were up to 10-fold higher than values observed for the other bioavailable metals and significantly inhibited benthic bacterial metabolism and turnover. Results from this study suggest that functional microbial variables are highly sensitive to heavy metal contamination and could be used as bioindicators of stress conditions in coastal sediments.     

Metal Pollution Assessment in Sediments of the Southeastern Black Sea Coast of Turkey

The main objective of this investigation is to determine the concentration and accumulation of heavy metals in the coastal sediments of the Southeastern Black Sea of Turkey. The selected sampling area has mainly been affected by anthropogenic activities, such as agricultural, untreated domestic and treated industrial wastewater, and mining. Metal enrichment factor (EF), geo-accumulation index (I_geo), and metal pollution index (MPI) have been calculated and relative contamination levels evaluated at all stations. In this study, the maximum EF values calculated for nickel (Ni), cobalt (Co), cadmium (Cd), lead (Pb), chromium (Cr), arsenic (As), zinc (Zn), and copper (Cu) were 1.4, 3.1, 5.2, 7.8, 7.8, 20, 26, and 42, respectively. Metal pollution has decreased in recent years, but the enrichment of heavy metals has been observed to be relatively high, especially in the uppermost 3-6 cm of the core sample from the Sürmene sampling station, which has been polluted by mining activities. In addition, factor analysis revealed that the coastal sediments from the Eastern Black Sea were influenced by several sources, namely lithogenic and anthropogenic activities (mining, wastewater discharging, agriculture).     

Climate change–contaminant interactions in marine food webs: Toward a conceptual framework

Climate change is reshaping the way in which contaminants move through the global environment, in large part by changing the chemistry of the oceans and affecting the physiology, health, and feeding ecology of marine biota. Climate change‐associated impacts on structure and function of marine food webs, with consequent changes in contaminant transport, fate, and effects, are likely to have significant repercussions to those human populations that rely on fisheries resources for food, recreation, or culture. Published studies on climate change–contaminant interactions with a focus on food web bioaccumulation were systematically reviewed to explore how climate change and ocean acidification may impact contaminant levels in marine food webs. We propose here a conceptual framework to illustrate the impacts of climate change on contaminant accumulation in marine food webs, as well as the downstream consequences for ecosystem goods and services. The potential impacts on social and economic security for coastal communities that depend on fisheries for food are discussed. Climate change–contaminant interactions may alter the bioaccumulation of two priority contaminant classes: the fat‐soluble persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), as well as the protein‐binding methylmercury (MeHg). These interactions include phenomena deemed to be either climate change dominant (i.e., climate change leads to an increase in contaminant exposure) or contaminant dominant (i.e., contamination leads to an increase in climate change susceptibility). We illustrate the pathways of climate change–contaminant interactions using case studies in the Northeastern Pacific Ocean. The important role of ecological and food web modeling to inform decision‐making in managing ecological and human health risks of chemical pollutants contamination under climate change is also highlighted. Finally, we identify the need to develop integrated policies that manage the ecological and socioeconomic risk of greenhouse gases and marine pollutants.     

The interactive effects of excess reactive nitrogen and climate change on aquatic ecosystems and water resources of the United States

Nearly all freshwaters and coastal zones of the US are degraded from inputs of excess reactive nitrogen (Nr), sources of which are runoff, atmospheric N deposition, and imported food and feed. Some major adverse effects include harmful algal blooms, hypoxia of fresh and coastal waters, ocean acidification, long-term harm to human health, and increased emissions of greenhouse gases. Nitrogen fluxes to coastal areas and emissions of nitrous oxide from waters have increased in response to N inputs. Denitrification and sedimentation of organic N to sediments are important processes that divert N from downstream transport. Aquatic ecosystems are particularly important denitrification hotspots. Carbon storage in sediments is enhanced by Nr, but whether carbon is permanently buried is unknown. The effect of climate change on N transport and processing in fresh and coastal waters will be felt most strongly through changes to the hydrologic cycle, whereas N loading is mostly climate-independent. Alterations in precipitation amount and dynamics will alter runoff, thereby influencing both rates of Nr inputs to aquatic ecosystems and groundwater and the water residence times that affect Nr removal within aquatic systems. Both infrastructure and climate change alter the landscape connectivity and hydrologic residence time that are essential to denitrification. While Nr inputs to and removal rates from aquatic systems are influenced by climate and management, reduction of N inputs from their source will be the most effective means to prevent or to minimize environmental and economic impacts of excess Nr to the nation’s water resources.     

云南程海湖泊系统响应富营养化与水文调控的长期模式

流域开发和气候变化背景下,逐渐增强的人类活动已经显著影响湖泊系统演替及功能。本研究以云南程海为研究对象,通过对程海湖泊沉积物记录与现代调查数据相结合,重建了程海近250年来的生态环境变化过程,探讨了程海湖泊系统在富营养化以及水文波动等多重环境压力影响下的长期响应模式。结果表明: 1970年之前程海营养水平整体偏低,1970—2000年间缓慢增长,2000年后快速增加,初级生产力呈长期上升趋势。1993—2000年期间,引水工程显著增加了湖泊水动力强度和物种扩散能力,促进了直链藻和菱形藻的增加。程海沉积物记录的碳循环变化主要受内源输入的长期影响。富营养化是硅藻群落长期演替的主要驱动因子,其次是湖泊水动力条件的波动。对程海的生态修复与流域管理不仅需要关注水体营养盐的富集与流域污染物的控制,同时还要考虑到湖泊水文调控和水位波动的影响。     

Organic and inorganic human-induced contamination of Posidonia oceanica meadows

In coastal environments, plants are used for phytoremediation of contamination. Organic and inorganic contaminants may be due to natural and/or anthropogenic sources. The aim of this study is to compare inorganic (trace metal) and organic (PAH) contamination in Posidonia oceanica and to analyse the relationship between these types of pollutants indeed very few studies have been interested in their correlations and common sources. P. oceanica leaves were collected in two sites exhibiting different levels of human-induced pressure. Higher values were recorded in the more polluted site (Toulon) for trace metals (Ag, Hg, Pb) as well as for PAHs (Medium Molecular Weight and High Molecular Weight) due to the presence of the city and/or harbour in proximity. For the first time in a coastal environment, correlations were observed between metals and PAHs.     

A geographic information system (GIS) analysis for trace metal assessment of sediments in the Gulf of Paria, Trinidad

The Gulf of Paria is a semi-enclosed shallow basin with increasing coastal development activities along Trinidad's west coast. Sediments present a host for trace metal pollutants from overlying waters, therefore determination of their content is critical in evaluating and detecting sources of marine pollution. This paper presents a Geographic Information System (GIS) analysis of geochemical assessment for trace metals in coastal sediments of the Gulf of Paria. This GIS approach facilitates interpretation of the spatial relationships among key environmental processes. The GIS development involves the integration of spatial and attribute data pertaining to bathymetry, current systems, topography, rivers, land use/land cover and coastal sediments. It employs spatial interpolation and retrieval operations to analyze the total trace metal concentrations of aluminum, copper and lead in the sediments and the clay-enriched sediments, to determine whether they are related to sediment type or are affected by the discharge from anthropogenic sources. Spatial distribution modeling of element concentrations are produced to indicate contamination plumes from possible anthropogenic sources such as rivers entering the Gulf of Paria, and to reveal potential hot spots and dispersion patterns. A direct spatial correlation between clay-enriched sediments and high concentrations of aluminum and lead is detected, however regions of high concentrations of copper and lead indicate a relationship to anthropogenic sources. The effectiveness of GIS for visualization, spatial query and overlay of geochemical analysis is demonstrated.     

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.     

气候变化影响下海岸带脆弱性评估研究进展

近百年来,全球气候系统正经历着以全球变暖为主要特征的显著变化。研究海岸带系统对气候变化的响应机制,评估气候变化对海岸带社会、经济和生态的潜在影响,提出切实可行的应对策略,是保障海岸带系统安全的重要前提。回顾了IPCC的四次评估报告,分析了全球气候变化对海岸带的影响。总结了海岸带脆弱性评估框架以及脆弱性评价指标体系,综述了国内外气候变化影响下海岸带脆弱性评估研究的进展。在综述国内外该领域研究进展的基础上,展望了气候变化影响下海岸带脆弱性评估研究。全球气候变化及其对海岸带的影响还有大量的科学技术问题需要进一步探讨,同时也需要对各种适应气候变化措施的可行性和有效性进行研究和验证。     

Intertwined effects of climate and land use change on environmental dynamics and carbon accumulation in a mangrove‐fringed coastal lagoon in Java,Indonesia

The identification and quantification of natural carbon (C) sinks is critical to global climate change mitigation efforts. Tropical coastal wetlands are considered important in this context, yet knowledge of their dynamics and quantitative data are still scarce. In order to quantify the C accumulation rate and understand how it is influenced by land use and climate change, a palaeoecological study was conducted in the mangrove‐fringed Segara Anakan Lagoon (SAL) in Java, Indonesia. A sediment core was age‐dated and analyzed for its pollen and spore, elemental and biogeochemical compositions. The results indicate that environmental dynamics in the SAL and its C accumulation over the past 400 years were controlled mainly by climate oscillations and anthropogenic activities. The interaction of these two factors changed the lagoon's sediment supply and salinity, which consequently altered the organic matter composition and deposition in the lagoon. Four phases with varying climates were identified. While autochthonous mangrove C was a significant contributor to carbon accumulation in SAL sediments throughout all four phases, varying admixtures of terrestrial C from the hinterland also contributed, with natural mixed forest C predominating in the early phases and agriculture soil C predominating in the later phases. In this context, climate‐related precipitation changes are an overarching control, as surface water transport through rivers serves as the “delivery agent” for the outcomes of the anthropogenic impact in the catchment area into the lagoon. Amongst mangrove‐dominated ecosystems globally, the SAL is one of the most effective C sinks due to high mangrove carbon input in combination with a high allochthonous carbon input from anthropogenically enhanced sediment from the hinterland and increased preservation. Given the substantial C sequestration capacity of the SAL and other mangrove‐fringed coastal lagoons, conservation and restoration of these ecosystems is vitally important for climate change mitigation.     

Fecal Pollution in Coastal Marine Sediments from a Semi-Enclosed Deep Embayment Subjected to Anthropogenic Activities: An Issue to Be Considered in Environmental Quality Management Frameworks Development

Sewage discharge is a major source of pollution in marine environments. Urban wastewaters can directly enter marine environments carrying pathogen organisms, organic loads, and nutrients. Because marine sediments can act as the ultimate fate of a wide range of pollutants, environmental quality assessment in this compartment can help to identify pollution problems in coastal areas. In the present study, characterization of surficial marine sediments allowed assessment of fecal pollution in a semi-enclosed deep embayment that is subjected to anthropogenic activities. Physicochemical parameters and fecal indicators presented a great spatial heterogeneity. Fecal coliform and Clostridium perfringens showed accumulation in an extensive area, not only in proximity to sewage discharge points, but also in sediments at 100 meters depth. Results included herein demonstrated that, in coastal areas, urban wastewater discharge can affect the whole ecosystem through accumulation of fecal matter in bottom sediments. Application of multivariate techniques provided useful information with applicability for management of coastal areas in such complex systems. Environmental implications of wastewater discharge in coastal areas indicate the need to implement and include sediment quality control strategies in legislative frameworks.     

三大沿海城市群滨海湿地的陆源人类活动影响模式

随着陆源人类活动对滨海湿地的干扰日益强烈,研究滨海湿地陆源人类活动影响规律对于滨海湿地资源管理和保护具有重要的现实意义.以我国三大沿海城市群(环渤海湾、长江三角洲、珠江三角洲)滨海湿地为研究对象,分别选取围海造地(直接因子)和流域污染物(营养盐、非点源无机污染物)输入(间接因子)表征1990-2000年间滨海湿地的陆源人类活动影响强度及规律.研究发现,虽然围海造地仍然以农业用地为主(＞50％),但城市建设用地比例随人口城市化率增高而增加,以珠江三角洲城市群最高;在环渤海湾和珠江三角洲城市群区域超过60％的滨海湿地面积受到高或中等污染物输入强度影响,长江三角洲城市群区域则有44.7％的滨海湿地面积处于中等污染物输入强度及以上.通过叠加围海造地和污染物输入双重陆源人类活动的综合影响强度表明,珠江三角洲城市群平均强度指数达到0.79,且处于中等及以上影响强度区域面积比例达到78％,均高于其他两个城市群滨海湿地区域.空间分析结果表明,陆源人类活动对滨海湿地的强影响区域多集中分布于河流人海口、较为发达城市滨海区以及海岸线附近.     

Contrasting distributions of bacteriophages and eukaryotic viruses from contaminated coastal sediments

Viruses are ubiquitous, abundant and play an important role in all ecosystems. Here, we advance understanding of coastal sediment viruses by exploring links in the composition and abundance of sediment viromes to environmental stressors and sediment bacterial communities. We collected sediment from contaminated and reference sites in Sydney Harbour and used metagenomics to analyse viral community composition. The proportion of phages at contaminated sites was significantly greater than phages at reference sites, whereas eukaryotic viruses were relatively more abundant at reference sites. We observed shifts in viral and bacterial composition between contaminated and reference sites of a similar magnitude. Models based on sediment characteristics revealed that total organic carbon in the sediments explained most of the environmental stress-related variation in the viral dataset. Our results suggest that the presence of anthropogenic contaminants in coastal sediments could be influencing viral community composition with potential consequences for associated hosts and the environment.     

The impact of landfilling and composting on greenhouse gas emissions – A review

Municipal solid waste is a significant contributor to greenhouse gas emissions through decomposition and life-cycle activities processes. The majority of these emissions are a result of landfilling, which remains the primary waste disposal strategy internationally. As a result, countries have been incorporating alternative forms of waste management strategies such as energy recovery from landfill gas capture, aerobic landfilling (aerox landfills), pre-composting of waste prior to landfilling, landfill capping and composting of the organic fraction of municipal solid waste. As the changing global climate has been one of the major environmental challenges facing the world today, there is an increasing need to understand the impact of waste management on greenhouse gas emissions. This review paper serves to provide an overview on the impact of landfilling (and its various alternatives) and composting on greenhouse gas emissions taking into account streamlined life cycle activities and the decomposition process. The review suggests greenhouse gas emissions from waste decomposition are considerably higher for landfills than composting. However, mixed results were found for greenhouse gas emissions for landfill and composting operational activities. Nonetheless, in general, net greenhouse gas emissions for landfills tend to be higher than that for composting facilities.