Seawater Intrusion In Coastal Areas Research Articles

Fluorine contents and its characteristics of groundwater in fluorosis area in Laizhou Bay, China

Fluorine concentration and other parameters in groundwater were assessed and attempts were made to clarify the relationship between fluorine (Fl) and seawater intrusion in coastal area of Laizhou Bay, China by comparing samples in fluorosis and non-fluorosis areas. The water from fluorosis villages reflects the influence of seawater intrusion and higher levels of conductivity (Ec), total dissolved solids (TDS), hardness (TH), Cl−, Br−, , Li+, Na+, Mg2+, and Sr2+. High Fl concentration was positive correlated with Ec, TDS, Cl−, Br−, Li+, Mg2+, Ca2+, Sr2+ and significantly with Na+, Na+/Ca2+, and sodium adsorption ratio. This investigation also observed that seawater intrusion and fluorosis show similar distribution and originating sources. Thus, the special process-seawater intrusion seems to be an important dynamic of Fl enrichment by changing chemical characters and enhancing Fl release ability. Moreover, the water treated by bone coal adsorption still maintains high risk of Ec, Na+, and TDS, even though Fl was within the safe limit. This study indicates that in Laizhou Bay, together with other coastal areas, seawater intrusion is a cause for concern when examining mechanism underlying fluorosis occurrence and developing integrated treatment technology.

Effects of Treated Wastewater Irrigation on Element Concentrations in Soil and Maize Plants

Surface water resources are scarce, and groundwater is the main source of water in Oman. Water shortage has lead to overpumping and reservoir depletion, which has caused seawater intrusion in coastal areas and salinization of groundwater and soils. Treated wastewater maintains environmental quality while providing sustainable agriculture and preserving scarce water sources. The numbers of wastewater treatment plants in Oman have been increased enormously, with the produced water utilized in forage production. Field experiments were conducted during the 2006–7 season to determine the effect of water quality (thrice-treated wastewater and fresh water), water quantity (1.4 ETc, 1.0 Etc, and 0.6 ETc), and their interaction on the chemical composition of forage maize. Soil moisture distributions and salinity redistributions were monitored throughout the experiments. The results indicated that treated wastewater leached more salts down the profile than fresh water. Treated wastewater also reduced the sodium adsorption ratio (SAR) by 74%, whereas fresh water reduced it by 68%. Fresh water treatments were observed to have greater moisture content than the treated wastewater. This was attributed to the fact that treated wastewater contained dissolved organic matter that slightly improves the physical conditions of the soil, resulting in increased water penetrations, and contained greater amounts of nutrients, resulting in vigorous plants that abstracted more water. The results also indicated that plants irrigated with treated wastewater contained greater nitrogen concentrations at all levels of water quantities than those irrigated with fresh water. However, potassium, phosphorus, calcium, magnesium, iron, sulfur, boron, zinc, copper, and manganese uptakes of forage maize did not show any significant differences between fresh and treated wastewater.

Use of vertical electrical soundings to delineate seawater intrusion in a coastal area of Byunsan, Korea

To delineate spatial extent of seawater intrusion in a small experimental watershed in the coastal area of Byunsan, Korea, electrical resistivity surveys with some evaluation core drillings and chemical analysis of groundwaters were conducted. The vertical electrical sounding (VES) method was applied, which is useful to identify variations in electrical characteristics of layered aquifers. The drilling logs identified a three-layered subsurface including reclamation soil, weathered layer and relatively fresh sedimentary bedrock. The upper two layers are the main water-bearing units in this area. A total of 30 electrical sounding curves corresponded mostly to the H type and they were further divided into three classes: highly conductive, intermediate, and low conductive, according to the observed resistivity values of the most conductive weathered layer. In addition, groundwater samples from 15 shallow monitoring wells were analyzed and thus grouped into two types based on HCO3/Cl and Ca/Na molar ratios with TDS levels, which differentiated groundwaters affected by seawater intrusion from those not or less affected. According to relationships between the three classes of the sounding curves and groundwater chemistry, locations of the monitoring wells with low HCO3/Cl and Ca/Na ionic ratios coincided with the area showing the highly conductive type curve, while those with the high ratios corresponded to the area showing low conductive curve type. Both the low electrical resistivity and the low ionic ratios indicated effects of seawater intrusion. From this study, it was demonstrated that the VES would be useful to delineate seawater intrusion in coastal areas.

Differentiation of palaeomarine and modern seawater intruded salinities in coastal groundwaters (of Karaikal and Tanjavur, India) based on inorganic chemistry, organic biomarker fingerprints and radiocarbon dating

Hydrosalinity evolution is examined in the Karaikal and Tanjavur coastal aquifers situated about 300 km south of Madras, Tamil Nadu, India. Ancient and modern sources of solutes in groundwaters have been differentiated using hydro-geochemical data, environmental radioisotope dates and organic biomarkers. Results from different techniques show consistently that the Pliocene aquifer possesses characteristic palmitoleic and oleic acid biomarkers, apparent 14C ages of more than 20 000 years and high I/Cl ratio; the modern marine-estuarine intruded groundwaters in the alluvial aquifer display relatively younger apparent 14C ages (modern to 3000 years), enriched potassium ion, low I/Cl ratio and contain vaccenic and hopanoic acid biomarkers, and they also tend to display transient changes in chemical characteristics. These results have practical importance with regard to identifying and controlling seawater intrusion in coastal areas.

Effect of Surface Source Variation on Seawater Intrusion in Aquifers

A one-dimensional sharp interface finite-element model is used for parametric studies on the transient behavior of seawater intrusion due to the linear variation of the surface source level. The validity of the numerical solution is established by comparing it with the results of the Hele-Shaw analog model. A general relationship between saltwater toe movement, and different rates of linear rise in the surface source level, located at various distances from the coast, was established. The movement of the interface is also monitored after the rise in the surface source level is stopped. The results obtained from the studies are applicable to a wide range of practical cases and are useful in management schemes on the control of seawater intrusion in coastal areas.