Adsorption and desorption of arsenate in Louisiana rice soils

Gedik, Kenan/0000-0001-8244-6935WOS: 000372082000010Adsorption and desorption of arsenic (As) in the soil are dominant parameters that affect the mobility and bioavailability of arsenic. Batch arsenate adsorption and desorption experiments were conducted using soils collected from three Louisiana, USA, aquaculture ponds representing different crayfish farming and rice cultural practices. Arsenate adsorption behavior in the soils was investigated using Freundlich and Langmuir sorption equations. Results demonstrated that the Langmuir isotherm model was the best fit based on statistical correlation with soil properties governing adsorption, for the entire range of arsenate concentrations for all soils. Adsorption of As(V) was governed by soil physicochemical properties especially Fe and Al oxides, clay and organic matter. Desorption of As(V) was initially fast, but with increasing incubation times desorption occurred progressively slower. Chemical fractionation of arsenic in the soils showed that the most mobile fraction represented 4.74-5.18% of the total arsenic. A part of this mobile fraction could potentially be taken up by rice and enter the food chain, but would require additional research to quantify

Nutrient Dynamics in a Restored Wetland

This research expands the understanding of the effects of hydrological restoration on nutrient reduction in a wetland associated with the Mississippi River Basin. The objective of this project was to observe the degree to which wetland restoration can sequester excess soil nutrients to improve water quality. Soil characteristics at sites in riparian wetlands following the initiation of Redman Point-Loosahatchie Bar Environmental Restoration Project were compared. Field sites were established in the Loosahatchie Chute, based on relative distance south of the notched dikes. Additionally, a natural riparian site was monitored. Soil samples were evaluated for spatial and seasonal differences in moisture content, bulk density, total carbon (C), nitrogen (N), and phosphorus (P). Measurements of total C, total N, and P were reduced at all sites compared to the reference site. Although hydrology has been restored to the wetlands, functionality may take a considerable amount of time to be detectable. © 2014 Taylor & Francis Group, LLC

Distribution of arsenic and other metals in crayfish tissues (Procambarus clarkii) under different production practices

Gedik, Kenan/0000-0001-8244-6935WOS: 000389090100033PubMed: 27639469Louisiana is one of the world's largest producer of crayfish. Arsenic (As) and other metals (Cd, Cu, Pb and Zn) concentrations were determined in crayfish tissues, plant and soil samples collected from Louisiana paddy rice fields, where crayfish/rice rotation farming is a common practice. the samples were collected from November 2013 to April 2014 from three different crayfish farming systems. Concentration of As in rice grain, rice straw, and native vegetation ranged between 033 and 0.41, 3.14-4.93, and 326-5.89 mg kg(-1), respectively. the highest As levels in the crayfish external and internal body parts were found in gill (4.04 +/- 1.70 mg kg(-1)), followed by hepatopancreas (3.42 +/- 1.57 mg kg(-1)), exoskeleton (1.52 0.85 mg kg(-1)), and muscle (1.50 +/- 0.69 mg kg(-1)). Positive correlations between As levels in the crayfish muscle and the plant tissue on which they feed were found in all farming systems (r = 0.405-0.438). the biomagnification factor (BMF) of As in different tissues varied between 0.29 and 1.08, having gill and hepatopancreas were the highest As accumulation while the lowest biomagnification was observed in crayfish muscle tissues which is a food source for human. the As levels along with other metals in crayfish muscle tissue were in acceptable levels for human consumption under all crayfish/rice rotation practices. Further studies are needed in determining the percentage of organic and inorganic arsenic in crayfish tissue. Published by Elsevier B.V.Council of Higher Education of TurkeyMinistry of National Education - TurkeyWe would like to thank the Council of Higher Education of Turkey for supporting Kenan Gedik. We also thank William (Ray) McClain for suggestions and comments on the manuscript