Adsorption Capacity Of Sediments Research Articles

Effects of Reclaimed Water on the Characteristics of Dimethyl Phthalate Adsorption on Sediments

Adsorptions of Dimethyl Phthalate (DMP) on three sediments in both reclaimed and ultrapure water were studied using the batch technique and the effects of reclaimed water on it were clarified. The data were interpreted by using Freundlich and Dubinin-Radushkviech models. The values of 1/n were among 0.207 to 0.766, showing the presence of multiple adsorption sites on sediments. Compared with the ultrapure water as the background solution, the adsorption capacities of sediments for DMP were reduced in case of reclaimed water due to the competition of substances in reclaimed water. The mean adsorption energy, E, is smaller in the reclaimed water than that in ultrapure water.

Trophic Status of Shallow Lakes of La Pampa (Argentina) and Its Relation with the Land Use in the Basin and Nutrient Internal Load

Phosphorus and nitrogen are essential nutrients for living organisms. Their concentration in the water of an aquatic ecosystem is one of the factors responsible for the trophic status of the lake and is related to the soils of the region and to the human activities carried out in their basins. These nutrients are also found in the bottom sediments, where they can either be retained or re-enter the water column. Since the information about the concentrations of nutrients in the water of some lakes of La Pampa (Argentina) is fragmentary, the aim of this study is to describe the trophic status of some shallow lakes of the semiarid center of Argentina and analyze its relation with the human activities in their basins, the concentrations of nutrients and organic matter and particle size distribution of sediments. To this end, we studied ten shallow lakes subjected to different anthropogenic influences (agriculture, agriculture and livestock and impacted by cities). All were hypertrophic and the concentrations of total phosphorus and total nitrogen were among the highest reported globally. Since some lakes had no fish, cladoceran grazing (top-down effect) led them have reduced concentrations of phytoplankton chlorophyll-a and high water transparency. This relativizes the use of these parameters to determine the trophic status. The sediments of seven of the studied lakes were predominated by fine sands, whereas three were predominated by silts. Nutrient and organic matter content were high, with higher concentrations in lakes with prevalence of fine particles. The reduced adsorption capacity of sediments, the resuspension by wind, the anthropogenic input and the accumulation favored by the arheic character of the basins would explain the high concentrations of nutrients in the water of these Pampean environments.

Phosphorus sequestration in Fe-rich sediments from two Brazilian tropical reservoirs

Abstract This study investigates the important role of Fe-oxide/hydroxide-rich bottom sediments, from two Brazilian tropical reservoirs, on P sequestration from the overlying waters, which decreases the risk of eutrophication. Data on P fractionation indicates that P adsorption capacity of sediments is predominantly associated with Fe, followed by orthosphosphate adsorbed onto Al hydr(oxides) and onto different forms of apatite (Ca–P). The soluble and loosely bound P-forms are low. To have a better understanding of the role of Fe oxides on the adsorption and sequestration of P in the reservoirs, data obtained by sequential extraction of P have been related to concentrations of total Fe and of various Fe-fractions extracted through an optimized fractionation scheme. These analyses indicated high levels of Fe bound to oxides/hydroxides. These mineral oxides, and the preponderance of pH-dependent charged clay minerals (kaolinite) in the clay fraction, induce the sequestration of the P entering the lakes, mainly in particulate form, by strong retention of PO 4 3 - through surface adsorption and precipitation phenomena. Phosphorus-retention provided by the replacement of OH− groups on the basal plane of the minerals, for P anions, decreases the negative impact of P inputs in these water systems. There is significant correlation between the concentrations of soluble reactive P in the water (SRP) and major chemical components of sediments (SiO2, Fe2O3, Al2O3, K2O, P2O5), which are related to the dominant bedrock geology. The interaction of SRP with bed-sediments and the chemical conditions of the environment (decrease of redox potential with depth and, in the dry period, a low O2 abundance), can explain fluctuations of SRP and TP (total P) in the water column. Due to the dynamic equilibrium in the sediment–water interface, in the dry season, reducing conditions in hypoliminia enhance the reduction of Fe(III) to the more soluble Fe(II) with subsequent release of the strongly retained P. This mechanism increases the soluble P fraction in sediments and the soluble reactive P in the water column, in this period. The straight linkage between geochemical properties of sediments and P concentration in the water column reported in this article suggests that study of the mineralogical and geochemical composition of bottom sediments could help to improve model predictions of P concentrations in surface waters.

Use of thin-layer and high-performance liquid chromatography for the study of the adsorption of surfactants on a river sediment

The adsorption of tributylphenol ethylene oxide isomers containing various lengths of ethylene oxide chain and positional isomers of tributylphenol on a riverine sediment was studied by thin-layer chromatography combined with high-performance liquid chromatography. The adsorption capacity of the sediment was compared with that of silica, alumina and diatomaceous earth. It was established that the adsorption capacity of the riverine sediment is similar to that of silica. The adsorption of surfactants on the sediment surface is not selective. Neither the length of the ethylene oxide chain nor the position of the butyl substituents on the phenol ring influence significantly the adsorption.

Determination of phosphorus saturation level in relation to clay content in formulated pond muds

An experiment was conducted to determine the amount of P needed to saturate simulated fish pond sediments, formulated to contain six levels of clay (0, 30, 41, 64, 73 and 81% by weight). A series of cylindrical cement tanks were filled to 20 cm depth with the six sediment types and triple superphosphate (TSP) solution was added to reach P saturation in sediment. Results showed that all sediment types reached constant inorganic-P concentration in the upper 5 cm after 12 weeks of TSP application, and P adsorption capacity of sediment increased with increasing clay content. Sediment P adsorption was slower and not significant ( P > 0·05) below 5 cm depth except in the sediment type containing 0% clay. Regression analysis showed that the rate and adsorption capacity of P in sediment are primarily governed by clay content and its dominant minerals. While organic-P and loosely bound-P are commonly deposited in sediment, most inorganic-P is adsorbed by cations to form cation-P complexes. The linear relationship between cation-P saturation level and the percentage of clay in sediment is highly significant ( r 2 = 0·84, P < 0·001) and, therefore, maximum adsorption capacity of cation-P in pond sediment can be approximated by Y = 0·019 X (where Y represents the 100% saturation level in mg P g −1 soil, and X is the percentage of clay in the sediment). In practice, the level of P saturation in sediment can be approximated by the initial cation-P and clay contents in the top 5 cm of pond mud using the equation: P saturation (%) = initial cation-P (mg g −1 soil) × 100/P adsorption capacity (mg g −1 soil).

Removal of floodwater nitrogen in a cypress swamp receiving primary wastewater effluent

Intact sediment-water columns from a flowing cypress swamp receiving primary wastewater effluent were used to evaluate inorganic N removal and to determine the fate of 15NH inf4 sup+ -N added to the floodwater. Treatments represented wetland sites which had received 0 (initial application), 2, and 50 years of primary wastewater application. The rate of inorganic-N decrease in the floodwater was greatest for the initial application columns, primarily due to sediment adsorption of NH inf4 sup+ , followed by 2-year and 50-yr-columns. Maximum removal rates were 318, 296, and 148 mg N m−2 day−1, respectively. At the end of the 21-day study period, only 0.5 to 2.3% of applied 15N was recovered in the floodwater and 11.4 to 17.3% was recovered in the sediment, with the remaining 82.2 to 86.3% being lost from the sediment-water system. Results of the study indicated that N removal efficiency did not decrease with prolonged wastewater application, despite reduced sediment adsorption capacity, because of the significance of gaseous N losses (nitrification-denitrification, NH3 volatilization) as an N sink in the sediment-water system.

Sediment-water exchange in Lough Ennell with particular reference to phosphorus

The significance and evaluation of sediment phosphorus in the continuing eutropic conditions noted in Lough Ennell was assessed. A high positive correlation exists between the concentrations of total Fe, citrate dithionite bicarbonate (CDB) extractable Fe, organic content, total Al and a number of phosphorus fractions (total P, inorganic P, organic P, apatite P and CDB extractable P) for all samples recovered. A significant inverse correlation was noted between CaCO 3 and most of the other parameters measured whereas no correlations were found for Mn. The sediment adsorption capacity for orthophosphate was found to be about 450 μg P g −1 sediment. Phosphate release from hypolimnetic anaerobic sediments was considered unimportant in the biological sense due to the lack of mobility of this nutrient to the photic zones. Bioavailable P in the littoral zones (assumed to be non-apatite inorganic phosphorus, NAIP) comprised 14.5 tonnes in the uppermost 2 cm sediment layer, which is about 2.5 times the average annual external total P load. Littoral zone sediments, which are normally aerobic, accounted for an internal areal loading of 134 mg P m −2 yr −1 which is equivalent to 17 and 30% of the average external total P and inorganic P loadings respectively. This internal loading is a major contributory factor in the continuing eutrophic status of the lake.