Monitoring of organochlorine pesticides in surface waters in Hanoi and detoxification of organochlorine and organophosphorus pesticides in water by applying novel methods using ultraviolet irradation, air ionisation and solar photocatalysis

This thesis can be divided into two major parts: Monitoring of selected organochlorine pesticides in surface waters and Study on the applying of novel Advance Oxidation ProcessesAOP (Air Ionisation and Solar Photocatalytic Oxidation) for the detoxification of waters containing toxic organochlorine and organophosphorous pesticides, which are some well-known insecticides like Lindane, 4,4 ́-DDT, Methamidophos (Me) and Monocrotophos (Mo). The monitoring process was undertaken with the same procedure in two years (in the Dry Season: Nov. 1998 and in the Rainy Season: Aug. 1999) for an evaluation of the contamination of 15 organochlorine pesticides in surface waters, by sampling of 30 water samples from different sites (Red and Duong Rivers, irrigation canals, lakes and wells) on an area of ≈ 30 by 20 km in Hanoi and its surroundings, Vietnam. Those pesticides (HCH isomers, Heptachlor, Aldrin, Endrin, 4,4 ́-DDT and its derivatives) have been recently banned in Vietnam (from 1992 to 1998). This monitoring process was an initial systematic investigation of surface water quality in Hanoi, in order to find out a general evaluation towards the contamination of banned pesticides in waters. The results showed that the pollution of those pesticides was highest in the rivers and then in the irrigation canals, followed by the lakes and wells. Out of HCH isomers investigated, only Lindane appeared in most of sampling sites at considerable concentration. In the rainy season, the highest concentration of Lindane was found surprisingly in a lake water sample (West Lake) at 107 ng l, while that of Σ HCHs was 122 ng l. Besides, 4,4 ́-DDT and its derivatives were detected in most samples, and their concentrations were especially higher in the rivers and irrigation canals. The highest concentration of Σ DDTs was found in a Red River sample at 324 ng l in the rainy season and at 232 ng l in the dry season. Chlorinated cyclodienes, including aldrin, endrin and heptachlor were detected at most of the sampling sites at remarkable concentrations, while dieldrin and heptachlorepoxide (isomer A) were only detected in some samples. The photooxidation of Lindane and 4,4 ́-DDT (C0 = 5 mg l), the two major contaminated insecticides detected in surface waters in Hanoi, was investigated using two UV irradiation sources (High Pressureand Low Pressure mercury lamp: HP and LP). The addition of NaNO3 in the degradation of 4,4 ́-DDT could not significantly speed up the degradation process. Besides applying the well-known oxidative agent H2O2, the influence of the photocatalyst TiO2 (P25 Degussa) in different pH media (3, 7 and 12) on the decomposition of those 2 insecticides was extensively studied. Lindane was considerably degraded faster than 4,4 ́-DDT (e.g. with the HP, 0.2 % H2O2 at pH 7, k = 0.0139 min, t1/2 = 49.8 min for Lindane, while that were k = 0.00892 min, t1/2 = 77.7 min for 4, 4 ́-DDT. The photooxidative decomposition studies focused on the mineralisation of the two highly toxic organophosphorous insecticides, namely Methamidophos and Monocrotophos (C0 = 5 mg l). The photodegradation of Me and Mo was first undertaken using the 2 UV Lamps HP and LP with addition of H2O2. 50 % Me was degraded with the HP after 22.9 min when no H2O2 was added, while that degradation process was relatively slower for Mo (t1/2 = 166.6 min). The degradation of them was extremely fast when using the LP with or without addition of H2O2. The HP was much more effective when H2O2 was added. Using a new developed reactor Ionised Air Pilot System 2 (IAPS-2), Mo was mineralised drastically faster than Me. The half-life of the photodegradation of Mo was only 1.7 min (k = 0.3963 min), while that of Me was 59.2 min (k = 0.0117 min). The mineralisation of Me and Mo was also followed by means of Ion Chromatography. Based on the concentrations of anions, including NO3, PO4, SO4 detected during and after each oxidative process, the mineralisation of those insecticides was reconfirmed. The treated water samples of all oxidative processes using the HP, LP and IAPS-2 were biologically tested with Daphnia and Luminescent bacteria for a confirmation of the detoxification of water contaminated with Me and Mo after the treatment. The photocatalytic detoxification of Me and Mo (C0 = 10 mg l) was investigated using a Lab Solar Simulated Reactor (LSSR) and a new kind of solar non-concentrating Double Skin Sheet Reactor (DSSR) in the Institute of Solar Energy Research, Hannover (ISFH). 12 diverse different commercial, modified and novel photocatalysists (TiO2 at concentrations of 500 and 1000 mg l), which are mostly pure anatase TiO2 powder, except well-known catalyst P25 Degussa (70 % anatase, 30 % rutile) were tested with those reactors in the photocatalytic degradation of Me and Mo at different pH values of 3, 7, 12. The photonic efficiency (ζ) of them was calculated for searching for optimal catalysts. Using the LSSR at pH 7 and 500 mg l catalyst for the detoxification of Me, the highest values of ζ reached with Cat 11 (Pt-Hombikat) at 1.1 %, while that increased surprisingly to 1.78 % with Cat 8 (Mikroanatase) at 1000 mg l concentration. Both the correspondent highest values of ζ = 1.87 and 2.43 % reached with Cat 11 for the detoxification of Mo. Using the DSSR at pH 7 and 500 mg l catalyst for the detoxification of Me, the highest values of ζ reached with Cat 1 (P25 Degussa) at 0.81 %, while that increased also to 1.1 % with Cat 8 (1000 mg l concentration). For the detoxification of Mo, both the correspondent highest values of ζ = 2.94 and 3.01 % reached with Cat 11. The lowest photonic efficiency reached mostly with Cat 12 (Bayoxide T2). The novel Cat 5 supplied by Millennium (PC 500) was also an effective catalyst. In acidic and alkaline media (3 and 12), the photocatalytic degradation of Me and Mo was much faster than that at pH 7, the degradation rate increased around 10 times even when some low effective catalysts at pH 7 used. The DSSR was significantly more effective in the degradation of those 2 insecticides than the LSSR. The intermediates formed in the photooxidation processes of Me and Mo were detected and identified using the new analytic technique High Performance Liquid Chromatography coupled with a Mass Spectrometer (HPLC-MS). The possible molecular structure of those intermediates was explained based on their mass spectra (All MS and MS/MS). An initial detailed possible photocatalytic oxidation mechanisms of the degradation of Methamidophos and Monocrotophos has been found by combination of a proposed general photocatalytic oxidation mechanism of an organic pollutant (assuming an initial oxidative attack by a hydroxyl radical to a methyl group) with the molecular structures of identified intermediates.