Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam
➤ Gửi thông báo lỗi ⚠️ Báo cáo tài liệu vi phạmNội dung chi tiết: Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam
Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam
GEOCHEMICAL STUDY OF ARSENICBEHAVIOR IN AQUIFER OF THE MEKONG DELTA, VIETNAMByNGUYEN KIM PHUONGDEPARTMENT OF EARTH RESOURCE ENGINEERING GRADUATE SCHOO Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam OL OF ENGINEERING KYUSHU UNIVERSITY FUKUOKA 2008GEOCHEMICAL STUDY OF ARSENIC BEHAVIOR IN AQUIFER OF THE MEKONG DELTA, VIETNAMA dissertation submitted in partial fulfillment of the requirements for the Degree of Doctor of Engineering in Kyushu UniversityByNGl YEN KIM PHI ONGAdvisorProf. Dr. Ryuichi I Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam TOIABSTRACTArsenic (As), a toxic metalloid, is often found at high concentration in groundwaters because it IS soluble and It sorbs weakly under reducGeochemical study of arsenic behavior in aquifer of the mekong delta, vietnam
ing conditions. Naturally occurring arsenic can be mobilized from aquifer materials by induced reducing condition, as observed 111 the Mekong Delta. VGEOCHEMICAL STUDY OF ARSENICBEHAVIOR IN AQUIFER OF THE MEKONG DELTA, VIETNAMByNGUYEN KIM PHUONGDEPARTMENT OF EARTH RESOURCE ENGINEERING GRADUATE SCHOO Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam The burial of sediments rich in organic matter leads the sediment formations to reduced conditions Moreover, the inherently abundance of acid sulfate soil and pyrite in the Mekong Delta, along with low pH are favorable conditions for the release of arsenic. Arsenic concentrations in sediments in th Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam e Mekong Delta range from 4 to 45 mg kg. Where concentration of arsenic and non are high, the sediments are yellowish brown to reddish brown implyingGeochemical study of arsenic behavior in aquifer of the mekong delta, vietnam
a presence of iron oxides hydroxides. Results of adsorption experiments on core sample indicated that maximum adsorption capacity of arsenite (As(III)GEOCHEMICAL STUDY OF ARSENICBEHAVIOR IN AQUIFER OF THE MEKONG DELTA, VIETNAMByNGUYEN KIM PHUONGDEPARTMENT OF EARTH RESOURCE ENGINEERING GRADUATE SCHOO Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam nd As(V). respectively, was adsorbed on core sample within 111. More than 0.85 mg'g (82%) and 2.2 mgg (88%) of As(III) and As(V) adsorbed after 311 of reaction time.Groundwater samples collected from tube wells at different depths (20 to 440 111) in the Mekong Delta indicate that groundwaters are of Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam sodium bicarbonate and chloride type. The high Na* and CT concentrations and high EC values of samples near coastal areas are due to differences 111Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam
degree of mixing ratiobetween fresh ground water and seawater ORP values of the groundwater range from -260 mV to 124 mV. Generally, chemical analysesGEOCHEMICAL STUDY OF ARSENICBEHAVIOR IN AQUIFER OF THE MEKONG DELTA, VIETNAMByNGUYEN KIM PHUONGDEPARTMENT OF EARTH RESOURCE ENGINEERING GRADUATE SCHOO Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam s NH4 . Mn" and Fe2 . except Cao Lanh (CL) and Hong Ngu-Tan Hong (HN-TH), which have positive ORP values. In groundwater arsenic concentrations range fl0111 1 pg 1 to 741 pg 1. Arsenic concentrations exceeding 100 pgL are detected at shallow depths around 25 m. whereas arsenic concentrations more th Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam an 10 pg L aie not found at deepei level (> 100 111 depths) except for sample Binh Minh (BM2) From the coreelation between Fe and As concentrations, tGeochemical study of arsenic behavior in aquifer of the mekong delta, vietnam
he release mechanism of arsenic IS as follows: dissolution of Fe(OH)j and desorption of arsenic under reducing condition, oxidative decomposition of FGEOCHEMICAL STUDY OF ARSENICBEHAVIOR IN AQUIFER OF THE MEKONG DELTA, VIETNAMByNGUYEN KIM PHUONGDEPARTMENT OF EARTH RESOURCE ENGINEERING GRADUATE SCHOO Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam loyed to evaluate chemical speciation of arsenic 111 soil 111 (1) Mekong Delta. Vietnam and (2) Sasagun town. Kasuya Province, Fukuoka Prefecture. Japan. Soil samples (1 111 depth) in the Mekong Delta were collected at Tan Chau (TC). An Phong (AP), Tan My (TM) and Lai Vung (LV). Among these area ars Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam enic concentrations 111 groundwater 111 TC, AP and LV were relatively high while arsenic concentrations in TM weie low. However. TM soil IS affected bGeochemical study of arsenic behavior in aquifer of the mekong delta, vietnam
y acid sulfate soil which relatively low pH (3.46). Surface soil samples (0 - 10 cm depth) in Sasaguri (N4b) were collected in aiea where is geologicaGEOCHEMICAL STUDY OF ARSENICBEHAVIOR IN AQUIFER OF THE MEKONG DELTA, VIETNAMByNGUYEN KIM PHUONGDEPARTMENT OF EARTH RESOURCE ENGINEERING GRADUATE SCHOO Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam rphous and poorly crystalline Fe-Mn hydroxides and extractediiby strong reducing agents (NHuhC^Oj was the largest one. comprising about 73% of total arsenic for the N4b, TC. AP. LV soil and 50% for TM soil. The percentage of arsenic in the residual fraction was from 15 to 23%. The small amount of ex Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam tracted arsenic in residual fraction was probably retained by silicate and Al silicate. In contrast, large dissolution of Al (74%) but slight releaseGeochemical study of arsenic behavior in aquifer of the mekong delta, vietnam
of Fe and Mn in residual fraction indicated that the HF-soluble aluminum silicate minerals. The mobile fractions of arsenic made up 1.5 - 2.9% and 7.2GEOCHEMICAL STUDY OF ARSENICBEHAVIOR IN AQUIFER OF THE MEKONG DELTA, VIETNAMByNGUYEN KIM PHUONGDEPARTMENT OF EARTH RESOURCE ENGINEERING GRADUATE SCHOO Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam except TM sample (up to 30%).Laboratory column experiments were conducted to examine the mobility of arsenic from soil in the presence of Fe hydroxide under controlling redox conditions. The soil column was made by packing mixture of Sasagun soil and Fe hydroxide coprecipitated with arsenic In order Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam to control the redox conditions, tap water and ascorbate solution was supplied with a specified time interval. In the experiment, supplying of sodiumGeochemical study of arsenic behavior in aquifer of the mekong delta, vietnam
ascorbate solution strongly affected redox potential in the soil column. A significant decrease in ORP from -143 mV to -229 mV (Period I) and from -2GEOCHEMICAL STUDY OF ARSENICBEHAVIOR IN AQUIFER OF THE MEKONG DELTA, VIETNAMByNGUYEN KIM PHUONGDEPARTMENT OF EARTH RESOURCE ENGINEERING GRADUATE SCHOO Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam ues started decreasing after 7 Ins whereas arsenic and iron concentrations increased gradually up to 70 lirs. After reaching the maximum value (71.2 mg/L), As concentrations again decreased and ORP increased. Like arsenic, dissolved iron increased up to 4154 mgL after a few hours and then the concen Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam trations decreased. However, neither arsenic nor iron was detected whenincolumn was fully in oxidizing condition Results column experiments indicatedGeochemical study of arsenic behavior in aquifer of the mekong delta, vietnam
a strong dependence of redox potential on both As and Fe concentrations. Under moderately oxidizing conditions, arsenic mainly associated with adsorptGEOCHEMICAL STUDY OF ARSENICBEHAVIOR IN AQUIFER OF THE MEKONG DELTA, VIETNAMByNGUYEN KIM PHUONGDEPARTMENT OF EARTH RESOURCE ENGINEERING GRADUATE SCHOO Geochemical study of arsenic behavior in aquifer of the mekong delta, vietnam itions, arsenic solubility seemed to be controlled by the dissolution of Fe hydroxidesGEOCHEMICAL STUDY OF ARSENICBEHAVIOR IN AQUIFER OF THE MEKONG DELTA, VIETNAMByNGUYEN KIM PHUONGDEPARTMENT OF EARTH RESOURCE ENGINEERING GRADUATE SCHOOGọi ngay
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