The Need for Scale Sensitive Approaches in Spatially Explicit Land Use Change Modeling

This paper introduces some of the issues that are relevant to the spatially explicit modeling of land use systems. A short overview is given of the ways and means in which a number of different land use change models describe the land use system. Specific attention is given to the empirical modeling approach used in the CLUE (Conversion of Land Use and its Effects) modeling framework. This approach is demonstrated for three case studies in China, Ecuador and the Atlantic Zone of Costa Rica. These case-studies illustrate the methodology for multi-scale analysis of land use driving factors and their application in spatially explicit modeling exercises. Model functioning, performance and limitations are discussed. The presented case-studies indicate that empirical modeling results can contribute to a better theoretic imbedding of land use change research in scale sensitive and integrated theories.     

Application of GIS in the study of mass transport of pollutants by Adyar and Cooum Rivers in Chennai, Tamilnadu

Residential, industrial, commercial, institutional and recreational activities discharge degradable and non-degradable wastes that reach the coastal water through rivers and cause coastal pollution. In the present study, mass transport of pollutants by Adyar and Cooum Rivers to the coastal water as a result of land-based discharges was estimated during low tide. The lowest and the highest flow recorded in Adyar varied from 514.59 to 2,585.08×10⁶ litres/day. Similarly, the flow in Cooum River fluctuated between 266.45 and 709.34×10⁶ litres/day. The present study revealed that the Adyar River transported 53.89–454.11 t/d of suspended solids, 0.06–19.64 t/d of ammonia, 15.95–123.24 t/d of nitrate and 0.4–17.86 t/d of phosphate, 0.004–0.09 kg/d of cadmium, 0.15–1.29 kg/d of lead and 3.03–17.58 kg/d of zinc to the coastal water owing to its high discharge. Similarly, the Cooum River transported 11.87–120.06 t/d of suspended solids, 0.08–58.7 t/d of ammonia, 6.11–29.25 t/d of nitrate and 0.66–10.73 t/d of phosphate, 0.003–0.021 kg/d of cadmium, 0.02–0.44 kg/d of lead and 1.36–3.87 kg/d of zinc. A higher concentration of suspended solids was noticed in post monsoon and summer months. An increase in the mass transport of ammonia, nitrate, phosphate in summer months (April and May) and an increase in the mass transport of cadmium, lead and zinc were observed in monsoon months (October–December) in both the rivers. Thus mass transport of pollutants study reveal that Cooum and Adyar Rivers in Chennai contribute to coastal pollution by transporting inorganic and trace metals significantly through land drainage.     

Inputs of chemicals from recreational activities into the Norwegian coastal zone

Wastewater treatment works effluent is often considered to be one of the most important point sources of a wide range of anthropogenic contaminants to aquatic systems, however, this paper discusses other potential sources. With the aim of establishing the important sources of UV filters, insect repellent and biocides to the aquatic environment, samples were collected from sites with direct (bathing areas and marinas) and indirect (sites receiving wastewater effluent) human influences. Sunscreens containing UV filters are used in large volumes during the summer months and often applied shortly before a person enters the water for swimming activities. The results presented here demonstrate that washing directly from the skin is an important point source of 4 UV filters to the Oslofjord. The insect repellent, diethyl toluamide, was also measured and it was concluded that washing from the skin was not such an important point source into the fjord. Concentrations of the biocide Irgarol 1051 were also measured and were elevated in the small boat marina and surrounding enclosed area. This work demonstrates that man recreational water-based activities are a diffuse source of some contaminants into coastal and fjord environments and this study provides an initial assessment of the levels being released.     

Kinetics of sorption of lead on bed sediments of River Hindon, India

A number of low cost waste sorbent have been used for removal of heavy metals, however, few studies have been carried out on the sorption process on riverbed sediments in their natural state of occurrence. Stream sediments adsorb certain solutes from streams, thereby significantly changing the solute composition, but little is known about quantitatively describing sorption phenomena and rates of these processes. In the present investigation, sorption of lead ions on river bed sediments of river Hindon, a tributary of river Yamuna, India has been studied to demonstrate the role of bed sediments in controlling metal pollution. The effect of various operating variables, viz., initial concentration, solution pH, sediment dose, contact time and particle size has been studied. The sorption of lead ions increased with respect to pH and sorbent dose and decreased with sorbent particle size. Two important geochemical phases, iron and manganese oxide, also play important role in the sorption process. The sorption data were analysed using Langmuir and Freundlich isotherm models to determine the mechanistic parameters related to the sorption process. Further, although lead ions have more affinity for the fine fraction of the sediment, but the overall contribution of coarser fraction to sorption is more as compared to clay and silt fraction. The kinetic data suggest that the sorption of lead on bed sediments is an endothermic process, which is spontaneous at low temperature. The uptake of lead is controlled by both bulk and intraparticle diffusion mechanism.     

Cover estimation versus density counting in species-rich pasture under different grazing intensities

Two methods for monitoring of grassland vegetation were compared: visual estimation of plant cover (C) and plant densities counting (D). C and D were performed in monthly intervals for three vegetation growing seasons after imposing different grazing regimes on abandoned grassland in 1998. Species scores obtained from paired redundancy analyses (RDA) of C and D data were compared and Spearman's rank correlations were used to show if the two methods give comparable results. Results of C and D were highly correlated in the first two growing seasons only. In the third season, correlation was substantially lower as the sward structure was more heterogeneous due to creation of differently defoliated patches especially under extensive grazing. Presence of the same plant species with different habit in frequently and in infrequently grazed patches, reduced significance of Spearman's rank correlations. Cover estimation can fully substitute plant density counting in grassland with lower proportion of frequently and infrequently grazed patches only, but caution should be used when comparing different management regimes in long term analyses.     

Multivariate statistical study of seasonal variation of BTEX in the surface water of Savitri River

Volatile organic compounds (VOCs) analysis was carried out for the surface water of the Savitri river during the period of June 2005 to June 2007. BTEX compounds (Benzene, Toluene, Xylene & Ethyl benzene) were analyzed by using micro extraction technique (Purge & Trap). Concentrations of these BTEX compounds were ranging from 0.1 to 1.5 ppm during sampling period. Higher concentrations of BTEX were found at sampling location VI. Concentration of ethyl benzene was very low as compare to other compounds. However, the concentration of benzene was very high. Seasonal variations in conc. of BTEX compounds were observed and higher concentration was detected during the summer season. Salting-out effect had given higher quantification values. In PCA and PFA, the component loading for all the variables are positively correlated. Death of fishes was observed in the river that is indication of severe pollution problem.     

Identification and quantification of microcystins from a Nostoc muscorum bloom occurring in Oukaïmeden River (High-Atlas mountains of Marrakech, Morocco)

Atmospheric BTEX [benzene, toluene, ethylbenzene, o-xylene and (m + p)-xylene] concentrations have been determined in the Naples metropolitan area (NMA) and in two suburban areas located on the north within about 25 km, during 2006. The pollutants were collected by passive samplers (24-h samplings), and analysed by GC-MS. In all the areas analysed the average atmospheric benzene concentrations were higher than the limit value fixed by the European Union for 2010 and in NMA the average concentration (9.8 microg m(-3)) also exceeded the limit fixed for 2006. High linear correlation coefficients between the average daily concentrations of the different BTEX are indicative of a single major source, most likely the vehicular traffic. The temporal and spatial distribution of BTEX relative concentrations suggest that massive emissions in NMA negatively affect the quality of the air in northern suburban areas, prevalently during the hottest months of the year, probably due to transport by local seasonal winds. The ratios between BTEX daily concentrations showed a clear dependence on the intensity of solar actinic flow, indicating a major role of photochemical processes in the air cleaning from these volatile organic pollutants.     

Principal response curves technique for the analysis of multivariate biomonitoring time series

Although chemical and biological monitoring is often used to evaluate the quality of surface waters for regulatory purposes and/or to evaluate environmental status and trends, the resulting biological and chemical data sets are large and difficult to evaluate. Multivariate techniques have long been used to analyse complex data sets. This paper discusses the methods currently in use and introduces the principal response curves method, which overcomes the problem of cluttered graphical results representation that is a great drawback of most conventional methods. To illustrate this, two example data sets are analysed using two ordination techniques, principal component analysis and principal response curves. Whereas PCA results in a difficult-to-interpret diagram, principal response curves related methods are able to show changes in community composition in a diagram that is easy to read. The principal response curves method is used to show trends over time with an internal reference (overall mean or reference year) or external reference (e.g. preferred water quality or reference site). Advantages and disadvantages of both methods are discussed and illustrated.     

Selection and application of a rainbow trout toxicity testing procedure for screening Sacramento River Watershed, California samples

A number of procedures have been developed to assess toxic effects on the early life stages of salmonid fish. In this study 13 rainbow trout embryo development relatively short-term (7 to 90 day) procedures were reviewed. Three 7-day methods from the published literature and three modifications developed at AQUA-Science (A-S) were evaluated in the laboratory. Based on that evaluation, A-S methods were selected for screening surface water samples (A-S 1) collected in the Sacramento River watershed (California) and for conducting toxicity identification evaluations (TIE) to identify cause(s) of toxicity. Test control performance, test sensitivity, and reference toxicant response variability in the A-S 1 were superior to those in commonly used freshwater toxicity testing methods. The incidence of Sacramento River watershed samples resulting in a notable decrease in embryo development was very low. Of 260 samples screened only 16 (6%) resulted in statistically significant inhibition of embryo development. Of the 16 toxic samples, nine caused minimal (less than 20% abnormal development) and four marginal (less than 30%) toxicity. Samples collected from the agriculture-dominated Colusa Basin Drain and rangeland/forest-dominated Battle Creek on June 16, 2005 caused significant toxicity. TIE procedures indicated that cationic chemicals were the primary cause of toxicity. Metals analysis did not reveal concentrations sufficient to inhibit embryo development, so the most probable cause of toxicity in the two samples was cationic chemicals (perhaps surfactants?) or metals that were not included in the analytical screening.