GIS application on arsenic considering toxicological aspect in an old tin mining area, Thailand | |
| Author | Zhang, Jianjun |
| Call Number | AIT Diss no.EV-02-08 |
| Subject(s) | Geographic information systems--Thailand Arsenic--Toxicology--Thailand |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Technical Science, Asian Institute of Technology; Inter-University Program on Environmental Toxicology, Technology and Management, Chulabhorn Research Institute, and Mahidol University |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. EV-02-08 |
| Abstract | This paper focuses on the application of GIS on arsenic contamination and its related toxicological aspects in southern Thailand. An old tin mining area was selected as study area with total coverage of 14 km2 . Features of arsenic contamination in this area were illustrated by GIS. This paper has 5 sections as following: Creation of GIS-oriented arsenic databases The study area situates between longitude 99°50'-99°52'E and latitude 8°10'-8°12'N. Such materials and information were collected, e.g. map of study area, stratigraphic properties of geology, inventories of land uses, rivers, roads, wells (including auger holes, shallow and deep wells), dredging ponds, old mining factories, waste dumping sites, patients' distribution and disease stage, arsenic concentration in different matrix (surface water, ground water and soil). These procedures were used to create GIS database: digitization; edition; attribute input; verification of database. All GIS analysis was limited within auger holes' buffer zone of 260 meters. Arc View GIS (version 3.1ESRJ,1998) program was used for the GIS process. Geospatial distribution of arsenic in surface water, groundwater and soil Using the interpolation function of GIS, the arsenic concentration in different matrix was estimated as a surface layer. In turn, the arsenic distribution profiles in three major matrixes were displayed. Estimation from the GIS interpolation showed: in shallow groundwater, 97% of the study area had arsenic level higher than O.Olmg/L. The mean value of total arsenic was 0.53mg/L, the median was 0.03mg/L, the highest value was 64mg/L; in deep groundwater: the contaminated area was larger than shallow groundwater. The area with arsenic level higher than O.Olmg/L occupied 99% of the total. The mean value of total arsenic was 0.47mg/L, the highest arsenic was 4.0lmg/L; in soil: the area with total arsenic level higher than 50mg/kg occupied 22%. The mean arsenic level was 36mg/kg, with the median value of l 8mg/kg and the highest value of 324mg/kg. At the same time, arsenic concentration were graded according to varied sub-classes of arsenic values, hot spots with arsenic concentration higher than 10-fold standard in each media were displayed. Identification of possible sources of arsenic contamination Six major dumping sites of tin mining wastes were identified as the major pollution sources through correlation analysis between arsenic level in soil/groundwater sample sites with the distance to mining and waste dumping sites. Especially the mine junk locates at the head of Ron Na River. Most of the arsenic present in study area is from mining waste through longterm dissolution from rainwater. The river water and dredging pond water may constitute another pollution sources to groundwater because of their mutual exchange between groundwater and surface water under certain geographic conditions. Arsenic related toxicological features The study area covers the four most serious villages No. 13, 1, 12 and 2 with arsenism prevalence of 46.12%0, 36.03%0, 33.25%0 and 12.79%0 respectively. Arsenism patients with skin lesion of stage II appear only at the area with sandy surface soil and arsenic level in shallow or deep groundwater above 0.05mg/L, water soluble arsenic fraction is above 0.05mg/L. After making a buffer zone of200 m from the patients' location, the arsenic level in shallow and deep groundwater inside the zone was significantly higher than outside zone, while the difference of arsenic level in surface soil elution inside or outside of the patients' zone is not significant. This may indicate that arsenic is the major cause of arsenism and the major pathway of arsenism is through drinking water, while the inhalation and ingestion of soil dust may be less important. The sandy soil facilitates the leakage of arsenic containing surface runoff into groundwater, results in the higher arsenic level in it. In addition, due to its lack of ferric and manganese oxides comparing with clay soil which can adsorb arsenic effectively, arsenic in sandy soil is easily mobilized and could be transferred to plants and vegetables. Arsenic risk assessment process Arsenic risk from inorganic arsenic in drinking water was primarily conducted within 4 villages. Village 12 has the highest exposure dose of arsenic, l.13E-3 mg/kg-day, followed by village 13, 2 and 1, which are 7.59E-3, 5.90E-4, and 8.36E-5 mg/kg-day respectively. Consequently, this results in the same order in cancer risks of 2.26E-3, l.52E-3, l.18E-3 and l.7E-4, and hazard quotients of 1.13, 0.76, 0.59 and 0.08 respectively. According to EPA estimation, the average total intake of inorganic arsenic from food, water and other beverages is about 17 μ,g/day, of which 5 μ,g/day come from drinking water. However, village 12 has 79.1μ,g/day arsenic only from drinking water, this is far higher than EPA estimation. As to the cancer risk, village 2, 12 and 13 have higher risk values than lE-4 where concerns should be taken according to EPA standard of arsenic induced cancer risk which is between lE-6 andlE-4. Considering the total population in these tlu·ee villages, the cancer patients would be 3, 7 and 2 respectively. The highest non-cancer risk occurs in village 12 where urgent measures must be considered to reduce the arsenic exposure, such as provide bottle water, avoid using shallow groundwater, increase using rain water for drinking purpose. |
| Year | 2002 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. EV-02-08 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Preeda Parkpian |
| Examination Committee(s) | Fukushi, Kensuke;Nguyen Cong Thanh;Skorn Mongkolsuk;Chen, Xiaoyong;Monthip Sriratana Tabucanon;Lin, Hui |
| Scholarship Donor(s) | State Education Commission of P.R. China |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2002 |