A multidisciplinary weight of evidence approach for classifying polluted sediments: Integrating sediment chemistry, bioavailability, biomarkers responses and bioassays

Evaluation of chemical bioavailability and onset of biological alterations is fundamental to assess the hazard of environmental pollutants, particularly when associated to sediments which need to be removed. In the present work, five sediment samples were collected from the Venice Lagoon and data from sediment chemistry were integrated with those of bioaccumulation of chemicals in European eel (Anguilla anguilla) exposed under laboratory conditions, responses of a wide battery of biomarkers, and standardized ecotoxicological bioassays. The overall results were elaborated within a recently developed, software-assisted weight of evidence (WOE) model which provides synthetic indices for each of considered line of evidence (LOE), before a general evaluation of sediment hazard. Levels of chemicals in sediments were not particularly elevated when compared to sediment quality guidelines of Venice Protocol. On the other hand, bioavailability was evident in some samples for Cd, Cu, Zn and, especially, polycyclic aromatic hydrocarbons. The ecotoxicological approach provided further evidence on the biological and potentially harmful effects due to released contaminants, and oxidative-mediated responses appeared of primary importance in modulating sublethal responses and the onset of cellular alterations. Biomarkers variations were sensitive, and more evident variations included significant changes of cytochrome P450 biotransformation pathway, antioxidant responses, onset of oxidative damages, lysosomal membrane stability and genotoxic effects. The results obtained from the battery of bioassays indicated that responses measured at organism level were in general accordance but less marked compared to the onset of sublethal changes measured through biomarkers. Overall this study revealed differences when comparing evaluations obtained from different LOEs, confirming the importance of considering synergistic effects between chemicals in complex mixtures. Compared to a qualitative pass-fail approach toward normative values, the proposed WOE model allowed a quantitative characterization of sediment hazard and a better discrimination of on the basis of various types of chemical and biological data.     

Cost-effective selection of sampling frequencies for regulatory water quality monitoring

A dynamic programming code was formulated for the purpose of assigning sampling frequencies throughout a regulatory water quality monitoring network in order to optimize the statistical performance of the network while operating within a fixed budgetary constraint. The statistical objective is to achieve the greatest possible station to station uniformity in confidence interval widths about annual geometric means of the measured water quality variables and to keep the average confidence width reasonably small. The objective function is the sum (over several selected variables and all stations) of the normalized positive deviations of the predicted confidence interval widths from preselected design confidence interval widths. The code was designed to account for the effects of deterministic seasonal variation and serial correlation of the water quality observations by incorporating the results of the time series analysis of historical quality data. The economic constraint ensures that the annual operating cost of the system, including direct costs of travel and laboratory analysis, will not exceed the allowable budget. As an example situation, the dynamic programming code was used to assign sampling frequencies to the nine stations in Illinois from which historical quality data had been obtained and analyzed. Using five design quality constituents and representative travel and laboratory costs, an “optimal” design was produced. The optimal design achieved a 10% improvement in uniformity (standard deviation) of confidence interval widths when compared to a more traditional design based on the same budget and using identical sampling frequencies at every station.     

Using sediment quality guidelines for dredged material management in commercial ports from Spain

Dredged material contamination was assessed in different commercial ports from Spain: Port of Cádiz and Huelva, South West; Bilbao and Pasajes, North; Cartagena and Barcelona, East; Coru?a, North West. Sediment from different locations of these ports was sampled and was characterized following the Spanish recommendations for dredged material management. This characterization included grain size distribution, organic matter content and concentration of the chemical compounds included in the list of pollutants and hazardous substances (As, Cd, Cu, Cr, Hg, Ni, Pb and Zn; PCB congeners IUPAC number 28, 52, 101, 118, 138, 153 and 180; PAHs were also analyzed). The results were compared to the limit values of Spanish Action Levels that define the different categories for assessment and management. A set of empirically derived sediment quality guidelines (SQG) was used to assess the possible toxicity of the dredged materials and to improve the use of the chemical approach to characterize dredged material for its management.     

Assessment of Self-Organizing Map artificial neural networks for the classification of sediment quality

The application of mathematical tools in initial steps of sediment quality assessment frameworks can be useful to provide an integrated interpretation of multiple measured variables. This study reveals that the Self-Organizing Map (SOM) artificial neural network can be an effective tool for the integration of multiple physical, chemical and ecotoxicological variables in order to classify different sites under study according to their similar sediment quality. Sediment samples from 40 sites of 3 estuaries of Cantabria (Spain) were classified with respect to 13 physical, chemical and toxicological variables using the SOM. Results obtained with the SOM, when compared to those of traditional multivariate statistical techniques commonly used in the field of sediment quality (principal component analysis (PCA) and hierarchical cluster analysis (HCA)), provided a more useful classification for further assessment steps. Especially, the powerful visualization tools of the SOM, which offer more information and in an easier way than HCA and PCA, facilitate the task of establishing an order of priority between the distinguished groups of sites depending on their need for further investigations or remediation actions in subsequent management steps.     

Determining floodplain sedimentation rates using Cs in a low fallout environment dominated by channel- and cultivation-derived sediment inputs, central Queensland, Australia

Fallout ¹³⁷Cs has been widely used to determine floodplain sedimentation rates in temperate environments, particularly in the northern hemisphere. Its application in low fallout, tropical environments in the southern hemisphere has been limited. In this study we assess the utility of ¹³⁷Cs for determining rates of floodplain sedimentation in a dry-tropical catchment in central Queensland, Australia. Floodplain and reference site cores were analysed in two centimetre increments, depth profiles were produced and total ¹³⁷Cs inventories calculated from the detailed profile data. Information on the rates of ¹³⁷Cs migration through local soils was obtained from the reference site soil cores. This data was used in an advection–diffusion model to account of ¹³⁷Cs mobility in floodplain sediment cores. This allowed sedimentation rates to be determined without the first year of detection for ¹³⁷Cs being known and without having to assume that ¹³⁷Cs remains immobile following deposition. Caesium-137 depth profiles in this environment are demonstrated to be an effective way of determining floodplain sedimentation rates. The total ¹³⁷Cs inventory approach was found to be less successful, with only one of the three sites analysed being in unequivocal agreement with the depth profile results. The input of sediment from catchment sources that have little, or no, ¹³⁷Cs attached results in true depositional sites having total inventories that are not significantly different from those of undisturbed reference sites.     

Metallic and organic contaminants in sediments of Sydney Harbour, Australia and vicinity-- a chemical dataset for evaluating sediment quality guidelines

An internally consistent dataset comprising 103 surficial estuarine sediment samples were collected from Sydney Harbour, Australia and locations south of Sydney. This paper describes the chemical characteristics of the dataset and evaluates its suitability for use in evaluating biological effects-based sediment quality guidelines (SQGs). The sediments contained mixtures of chemicals, the most prevalent chemical classes being metals and polycyclic aromatic hydrocarbons, whereas sediments from coastal lakes/estuaries south of Sydney had low concentrations of contaminants. Maximum concentrations of the prevalent contaminants zinc, lead, copper and pyrene were 11,300, 1,420, 1,060 mg kg(-1) and 23,300 microg kg(-1), respectively. For the majority of samples, concentrations of individual chemicals exceeded most effects-based SQGs that have been adopted for use in Australia, implying occasional or frequent adverse biological effects are expected. Comparing mixtures of contaminants to ranges in numbers of SQGs exceeded and mean SQG quotients showed that most samples (57% to 68%) had contamination characteristics associated with moderate probabilities (30% to 52%) of acute toxicity, based on North American data. A smaller proportion of samples (15% to 17%) had contamination characteristics associated with high probabilities (74% to 85%) of toxicity. The wide range of chemicals and concentrations, associated with low, medium and high probabilities of toxicity, indicated that the dataset was suitable for future use in evaluating predictive abilities of SQGs. This is relevant, given the recent introduction of North American-derived SQGs for Australia.     

Practising the past in the present: using Ghanaian indigenous methods for water quality determination in the contemporary era

Surface water sources remain the dominant sources of water supply for a significant proportion of poor communities. These water supply sources tend to have low water quality levels. Application of water quality determination and purification measures could minimize water-related diseases associated with direct consumption of water with poor quality levels. A number of simple measures have been devised and utilized by indigenous communities based on their resource conservation knowledge to improve water quality levels. However, scientific approaches that are more in tune with modern demands for reliability and exactness are the preferred, mainstream approaches for determining water quality. Growing recognition of the relevance of indigenous knowledge has led to renewed interest in the possibility of utilizing it for such tasks. Research conducted in 2007 and 2008 in two indigenous communities in Ghana revealed a diversity of indigenous methods for water quality determination and purification including straining, settling and use of special seeds which could still be useful in this contemporary era. This paper recommends that knowledge co-production and transdisciplinary approaches be employed to enable indigenous communities and experts to collaborate and develop measures that tap both knowledge systems for improving water quality levels for human use.     

Environmental sensitivity and risk assessment in the Saharan Tunisian oasis agro-systems using the deepest water table source for irrigation: water quality and land management impacts

Environment, Development and Sustainability - In dry-hot areas, such as southern Tunisia, the availability of good water is very limited by the low scanty rainfall, the long dry periods and the...