Pollution of lakes and rivers. A paleoenvironmental perspective

Interpretation Theory. Abstract interpretation is a semantic theory introduced by Patrick and Radhia Cousot in 1977 in order to design static analysis of computer programs and, more in general, software systems. In [37, 1] we prove that completeness of abstract domains w.r.t. semantic operators is a property which is preserved by the operation of lowest upper bound and greatest lower bound in the lattice of abstractions, provided the semantic operators are completely additive. We also show some negative results concerning some properties of domain refinements that, although seem quite natural, do no hold in practice.

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A hybrid approach was proposed to simulate the spatial distribution of a number of heavy metals in the surface layer of the soil. The idea of the method is to simulate a nonlinear large-scale trend using an artificial neural network (ANN) and the subsequent modelling of the residuals by geostatistical methods. A comparison was made with the basic modelling methods based on ANN: generalised regression neural network (GRNN) and multilayer perceptron (MLP). The raw data for the surface layer modelling of Cuprum (Cu), Manganese (Mn) and Niccolum (Ni) were obtained as a result of the soil screening in the subarctic city Novy Urengoy, Russia. The ANN structures were selected by the computer simulation based on the root mean square error (RMSE) minimization. The predictive accuracy of each selected approach was verified by the correlation coefficient, the coefficient of determination, RMSE, Willmott's index of agreement (d), a ratio of performance to interquartile distance (RPIQ) between the prediction and raw data from the test data set. It was confirmed that the use of the hybrid approach provides an increase in prediction accuracy in comparison with the basic ANN models. The proposed hybrid approach for each element showed the best predictive accuracy in comparison with other models based on ANN.

Combining spatial autocorrelation with machine learning increases prediction accuracy of soil heavy metals

Mercury (Hg) concentration trends in top predator fish (lake trout and walleye) of the Great Lakes (GL) from 2004 to 2015 were determined by Kendall–Theil robust regression with a cluster-based age normalization method to control for the effect of changes in lake trophic status When data from the GLs (except Lake Erie) are combined, a significant decreasing trend in the lake trout Hg concentrations was found between 2004 and 2015 with an annual decrease of 41% per year, consistent with the decline in regional atmospheric Hg emissions and water Hg concentrations However, a breakpoint was detected with a significant decreasing slope (−81% per year) before the breakpoint (2010), and no trend after the breakpoint When the lakes are examined individually, Lakes Superior and Huron, which are dominated by atmospheric Hg inputs and are more likely than the lower lakes to respond to declining emissions from areas surrounding the GL, have significant decreasing trends with rates between 52 and 78% per year f

Mercury Temporal Trends in Top Predator Fish of the Laurentian Great Lakes from 2004 to 2015: Are Concentrations Still Decreasing?

Investigating urban heat island through spatial analysis of New York City streetscapes

The Laurentian Great Lakes of North America contain approximately 20% of the earth’s fresh water. Smaller lakes, rivers and channels connect the lakes to the St. Lawrence Seaway, creating an interconnected freshwater and marine ecosystem. The largest delta system in the Great Lakes is located in the northeastern portion of Lake St. Clair. This article focuses on the geovisualization of total mercury pollution from sediment samples that were collected in 1970, 1974 and 2001. To assess contamination patterns, dot maps were created and compared with surfaces that were generated using the kriging spatial interpolation technique. Bathymetry data were utilized in geovisualization procedures to develop three-dimensional representations of the contaminant surfaces. Lake St. Clair generally has higher levels of contamination in deeper parts of the lake, in the dredged shipping route through the lake and in proximity to the main outflow channels through the St. Clair delta. Mercury pollution levels were well above the Probable Effect Level in large portions of the lake in both 1970 and 1974. Lower contaminant concentrations were observed in the 2001 data. Lake-wide spatial distributions are discernable using the kriging technique; however, they are much more apparent when they are geovisualized using bathymetry data.

https://www.mdpi.com/2077-1312/4/1/19/pdf

Geovisualization of Mercury Contamination in Lake St. Clair Sediments

For most of the last decade, the south-western portion of the United States has experienced a severe and enduring drought. This has caused serious concerns about water supply and management in the region. In this research, 30 orthorectified Landsat satellite images from the United States Geological Service (USGS) Earth Explorer archive were analyzed for the 1972 to 2009 period. The images encompassed Lake Mead (a major reservoir in this region) and were examined for changes in water surface area. Decadal lake area minimums/maximums were achieved in 1972/1979, 1981/1988, 1991/1998, and 2009/2000. The minimum lake area extent occurred in 2009 (356.4 km2), while the maximum occurred in 1998 (590.6 km2). Variable trends in water level and lake area were observed throughout the analysis period, however progressively lower values were observed since 2000. The Landsat derived lake areas show a very strong relationship with actual measured water levels at the Hoover Dam. Yearly water level variations at the dam vary minimally from the satellite derived estimates. A complete (yearly) record of satellite images may have helped to reduce the slight deviations in the time series.

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Visualization of Lake Mead Surface Area Changes from 1972 to 2009

The Great Lakes Water Quality Agreement between Canada and the United States has identified the Buffalo River as an Area of Concern. The watershed has a long history of heavy industrial activity that contributed to its overall pollution. Sediment core data collected by the New York State Department of Environmental Conservation in 2005 were used to determine lead sediment contamination in a section of the Buffalo River. The ordinary kriging spatial interpolation technique was used to generate surface and subsurface sediment contamination estimates. Due to the meandering nature of the river, two kriging models were used to analyze surface contamination: a global kriging model and a regional kriging model, consisting of three separate sections. The results show that both the global and regional kriging models display similar interpolated surfaces and do not vary significantly. Within the sediment, lead contamination in the surface layer is lower than at the various subsurface depths. In 2011, habitat restoration efforts commenced to remediate environmental damage due to years of pollution inputs from various sources. Sediment dredging operations were initiated that are expected to be completed in 2015. The goal of these operations is to remove heavily contaminated sediments and rehabilitate the Buffalo River. The kriging results provide area-wide estimates of contamination. When compared to the dredging plan, the results indicate that additional removal of contaminated sediments may need to be considered where no dredging has occurred or is not currently planned.

/pdf/assessing-lead-contamination-in-buffalo-river-sediments-4lehr52vpd.pdf

Assessing Lead Contamination in Buffalo River Sediments

Many communities depend on Lake St. Clair for drinking water and recreational uses. In addition, it is an important transport route for natural resources and manufactured products. The St. Clair River, which flows into the lake from the northeast, is a major source of sediment. The upstream area is known as “chemical valley” due to a large amount of industrial activity located along the river. Sediment sampling surveys were conducted in 1970, 1974, and 2001 by Environment Canada as part of a continuing monitoring program. Two approaches to the representation, analysis, and visualization of lead contamination were used: a two-dimensional Geographic Information System-based approach using kriging and a three-dimensional approach that utilized the interpolated kriging surfaces overlaid on bathymetry data. The results of combining this analytical method with a three-dimensional representation appear to show that Lake St. Clair generally has lower levels of sediment contamination away from the main flow and circulation patterns leading to its Detroit River outlet. Lead levels declined below the threshold effect level in 2001 compared with the higher concentrations seen in 1970 and 1974. In addition, lake-wide spatial distributions are better visualized using the kriging spatial interpolation results when they are overlaid on the bathymetry data.



L'emploi d'outils de geovisualisation pour evaluer la contamination par le plomb des sediments dans le lac Sainte-Claire

De nombreuses communautes utilisent les eaux du lac Sainte-Claire a des fins d'approvisionnement (eau potable) et recreatives. De meme, il sert d'axe principal pour le transport des ressources naturelles et des produits transformes. La riviere Sainte-Claire, qui se jette dans le lac depuis le nord-est, deverse d'importantes quantites de sediments. La zone situee en amont abonde de produits chimiques en raison des nombreuses activites industrielles en operation de part et d'autre de la riviere. Des echantillons de sediments ont ete preleves par Environnement Canada en 1970, 1974 et 2001 dans le cadre d'un programme de surveillance continue. Deux demarches ont ete mises en œuvre en vue de representer, analyser et visualiser la contamination par le plomb : une premiere s'appuie sur un systeme d'information geographique a deux dimensions utilisant une modelisation par krigeage, et une seconde a trois dimensions utilisant les surfaces d'interpolation obtenue par krigeage superposees aux donnees bathymetriques. Cette methode d'analyse conjuguee avec une representation en trois dimensions permet d'observer une diminution generale du degre de contamination sedimentaire du lac Sainte-Claire en retrait du courant du chenal principal menant a la decharge de la riviere Detroit. En 2001, les concentrations de plomb ont baisse au-dessous du niveau de l'effet de seuil par rapport aux valeurs plus elevees observees en 1970 et 1974. En outre, une meilleure visualisation des repartitions spatiales du plan d'eau est obtenue grâce aux resultats tires de l'interpolation spatiale par krigeage lorsque ceux-ci sont superposes aux donnees bathymetriques.

Using geovisualization to assess lead sediment contamination in Lake St. Clair

Bathymetry data offer interesting opportunities for the analysis of contaminant distribution patterns. This research utilized lead surficial sediment sample data from Lake Ontario that were collected by the Canada Centre for Inland Waters in 1968 and 1998. Traditionally, two-dimensional analyses such as dot maps or proportional circle representation have been utilized to examine pollutant levels. Generating area estimates allows for expanded spatial analysis of contaminant distribution patterns. Lake-wide surfaces were derived using the ordinary kriging technique. These were then layered on bathymetry data to examine three-dimensional relationships between observed pollution patterns and lake-bottom features. Spatial variability was observed in both the 1968 and 1998 datasets. Contamination levels in 1998 dropped substantially, especially in areas that were previously the most heavily polluted and above the Probable Effect Level (4660.23 km2 or 26.72% of the common analysis area lake-bottom in 1998 versus 6189.07 km2 or 62.00% in 1968). Conversely, areas below the Threshold Effect Level increased from 922.09 km2 (5.29%) in 1968 to 3484.22 km2 (19.98%) in 1998. In both years, shallow and sill/ridge areas tended to have lower levels of contamination than deeper lake basins or contaminant inflow areas. The 1968 dataset likely provides a more detailed estimation surface as there were more points available for interpolation procedures. The kriging surfaces when combined with bathymetry, sedimentology information, and knowledge of physical processes provide a comprehensive illustration of the contaminant distributions whether they are high (1968) or when loadings are significantly reduced (1998). The results have implications for future sediment assessment programs and survey design on a lake-wide basis. The bathymetry data allowed for enhanced interpretation and an improved understanding of observed lead pollution patterns.

Stephen J. Swales

Papers

Geovisualization of Mercury Contamination in Lake St. Clair Sediments

Visualization of Lake Mead Surface Area Changes from 1972 to 2009

Assessing Lead Contamination in Buffalo River Sediments

Using geovisualization to assess lead sediment contamination in Lake St. Clair

Utilization of bathymetry data to examine lead sediment contamination distributions in Lake Ontario