DETERMINATION OF SEDIMENTATION RATE IN ANZALI LAGOON OF NORTHERN IRAN USING 137Cs TRACER TECHNIQUE

Abstract

One of the management tools for sediment and erosion control in the different scales from plot to watershed is informing about soil displacement process that can be obtained using fallout radionuclide spectroscopy. In recent decades, use of the radionuclides for determining sedimentation rate was common, among which Cesium ( 137 Cs) is the most often used. In this research, three, 4-meter long sediment cores were collected from the western part of the Anzali Lagoon. The Anzali Lagoon is one of the sediment treated ecosystems in the north of Iran. The level of 137 Cs of the sediment samples was measured based on Spectrometry analysis in the Atomic Energy Organization of Iran. The grain size distribution showed that the sediment samples were mainly fine textured (Silt with low plasticity properties). The results represented that the highest amount of the 137 Cs was observed in the depth of 2.4-2.7 m, which can be related to the Chernobyl disaster in 1986. An overall sedimentation rate of 8.5 cm yr -1 (=119 kg m -2 yr -1 ) was obtained based on the 137 Cs calendar of the sediment cores. This sedimentation rate is considerable, and a special arrangement is necessary to save the Lagoon.

Investigating Anzali Wetland Sediment Estimation Using the MPSIAC Model

“…Given the status and characteristics of each element, including rock type, slope, direction, vegetation, land use, rainfall, and soil, factor scores were determined (Khalili Vavdare et al, 2019). First, the score of each factor was determined according to the results of the factor characteristics study.…”

“…Geologically, the rock units in most of the study area belong to the Quaternary period and predominantly have a loose structure and unconsolidated particles that erode during rainfall and snowmelt. Surface, furrow, and massif erosion transport sediment to the secondary and main waterways, and the Anzali Wetland (Khalili Vavdare et al, 2019). Using the raster map of geological units, the surface geological factor score in each sub-watershed was calculated.…”

“…The approximate location of the Anzali Wetland and its watershed is between N 36 °55′ to 37 °32′ and E 48 °45′ to °49 °42′ and is located in northern Iran along the coast of the Caspian Sea. The Anzali Wetland covers 193 km 2 in the Guilan Province and was registered in the Ramsar Convention International Wetlands list in 1975 (Khalili Vavdare et al, 2019). Although it is internationally known as an essential habitat for migratory water birds, it was added to the Montreux Record of degraded wetlands in 1993 (JICA, 2005).…”

“…Several soil erosion methods have been analyzed to watershed sediment yield or sediment rate studies (Eisazadeh et al, 2012), including empirical, numerical, and experimental models (Amini et al, 2010;Amiri, 2010;Najm et al, 2013;Noori et al, 2016;Pourkarimi et al, 2017;Zarei and Amiri, 2017;Brooshkeh et al, 2018;Noori et al, 2018;Zarei et al, 2019), as well as sensitivity analysis (Behnam et al, 2011) or chronological models (Abbasi, 2019;Khalili Vavdare et al, 2019). Empirical estimation methods were first developed to analyze the effects of agricultural practices (Eisazadeh et al, 2012;Noori et al, 2016) due to their simple structure and ease of application.…”

“…In the past, the Anzali Wetland was much deeper, but it has shallowed due to sedimentation. The total sediment inflow to the wetland is estimated at approximately 5,227.4 t km −2 year −1 (Khalili Vavdare et al, 2019). Sedimentation studies of the wetland were conducted to understand the dominant sediment origin and estimate the sedimentation rate for the ongoing management and conservation of the Anzali Wetland.…”