a. Monitoring on the composition of flooding water, suspended sediment and submerged soils in selected agricultural and aquaculture floodplain areas of Vietnam with main focus on contents, bonding, distribution and bioavailability of heavy metals (As, Pb), nutrients (N, P), pesticides and antibiotics (organochlorine, chloramphenicol) and concentration of fecal bacterial indicators (E. coli and enterococci)
b. Studies of contaminant transfer (toxic metals, pesticides, and antibiotics) from soils, sediments and plants to water in the floodplain areas followed by development of a partition model to quantify the contaminant releases over time. The transfer model is to be integrated in a transport model that can be used to predict the composition of flooding water as depending on soil composition, contaminant release, hydrology, and other parameters.
In order to obtain baseline data for water quality (river water) and composition of flooding water, as well as to get insight in contaminant transfer, different sampling methods will be used. Monitoring will go on for a period of 2 years.
Two sites typical for the lowland, frequently inundated area will be selected. The first is a paddy field in lowland delta area next to the DayRiver and the second is a fish pond in a coastal area famous for aquaculture.
Monitoring Experiments will be conducted before, during, and after flood. From monitoring data, we will conduct further calculation and additional experiments for contaminant transfer. Water and inundated soil will be collected. Filtration will be performed at sites for suspended sediment separation.
Sub-Task 1a: Monitoring. The following methods will be used for sampling and analyzing water, soils, and sediments.
Laboratory analyses: Soils, suspended sediment, and water will be analyzed for content, bonding forms and speciation of heavy metals, nutrients, and persistent organic pollutants using different laboratory and instrumental techniques. In brief, for heavy metal and metalloid analyses in soils and sediments, samples will be sequentially extracted in addition to total analysis (Cr, Pb, Hg, Cd, Ni, As). The sequential extraction, in principle, is to separate mobile/reactive, organic bound, Fe-Mn oxide, and residual heavy metal fractions. Metal bonding and leachability will be quantified using leaching tests. Metals will be determined using GF-AAS (PE A3300) and ICP-MS (PE Elan 9000). Pesticide or antibiotic compounds in water samples, plant samples, bulk sub samples of fresh channel bed sediment and overbank deposits will be analyzed by GC/ECD, GC/MS or LC/MS. Content of P and bonding in soil and suspended sediment will be determined using a sequential fractionation scheme. Total N will be determined by the Kjeldahl method while total C is semi quantitatively determined by dry combustion. Basic water and soil solution composition comprising analyses of major cations and anions (Ca2+, Mg2+, Na+, K+, NH4+, Cl-, SO42- NO3-, PO43-) as well as alkalinity, Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Chlorophyll A, and Dissolved Organic Carbon (DOC) will be determined according to Standard Methods for the Examination of Water and Wastewater . Particle size distributions of soils and sediments will be determined using a granulometer, after the removal of organic matter (H2O2) and dispersion. Mineralogy of soil fine fraction will be determined by combined powder X-ray diffraction, chemical composition and spectroscopic methods. Some parameters as physico-chemical properties (temperature, pH, Dissolved Oxygen, salinity, turbidity, conductivity, redox potential) will be measured in the field. E-coli and total coli form will be counted by fluorescence scanning method.
Sub-Task 1b: Contaminant transfer
Cylinder Samplers: Samples of the fine-grained sediment from within the upper ca. 5 cm of flooding areas will be collected using a resuspension cylinder. A cylinder (about 0.5 m diameter and 1.0 m high) will be inserted vertically into the bed in order to isolate a known surface area of the channel bed. A metal rod will be used to stir the water and agitate the upper ca. 5 cm of the bed isolated within the cylinder, thereby resuspending the fine-grained sediment stored both on the surface and within the upper ca. 5 cm. The water and remobilized sediment contained within the cylinder will then be pumped to fill acid-washed sample containers. The water samples collected in the containers will be left to settle-out under controlled conditions and the clear supernatant will be siphoned-off. The remaining sediment will be recovered by centrifugation. Water samples will be analyzed for concentrations of bacterial fecal indicators.
Transport Modeling: A reactive transport model will be used to analyze the depth profiles of solute and solid species in floodplain soil, and to investigate capacity of sediments in terms of storage and recycling of contaminants under both steady state and unsteady state conditions. In principle, the model simulates the degradation of organic matter and other geochemical reactions in sediment column