Since 2002, a joint research team from the International Water Management Institute and the Department of Agriculture, Thai Government, has reported that there are cadmium (Cd)-contaminated paddy fields in northern Thailand. We evaluated the current situation of the Cd-polluted paddy fields in this report. Home-consumed rice grains were collected from all 23 households in the village of Pha Te, Mae Sot District of Tak Province, Thailand. The Cd concentration in unhusked rice (Oryza sativa L.) grains ranged from 0.04 to 1.75 mg Cd kg À1 , and the rice of more than half of the households contained Cd levels higher than the critical level of 0.4 mg Cd kg À1 polished rice, which is CODEX standard. Among the paddy fields, we selected one plot (1.2 ha) and analyzed Cd concentrations of the soil, and rice and soybean (Glycine max L.) grains. In this area, a rotation cropping system of wet-season rice and dry-season soybean is common practice. The soil Cd concentration ranged from 0.31 to 13.9 mg Cd kg À1 (total Cd) and 0.030 to 13.3 mg Cd kg À1 [extracted with 0.1 M hydrochloric acid (HCl)], the Cd concentration in the rice grains ranged from 0.12 to 1.27 mg Cd kg À1 , and that in the soybean grains ranged from 0.07 to 0.80 mg Cd kg À1 . The soil extractable Cd concentration was well reflected in the soybean grain Cd levels (r 2 ¼ 0.581), but not in the rice grain levels (r 2 ¼ 0.015), suggesting that rice grain Cd levels are influenced not only by the soil Cd concentration, but by other factors as well, such as soil water regime and soil pH. However, a significant difference in the grain-Cd concentration was found; that is, lower Cd in the cultivar ''Khao' Khaeng'' and higher in the ''Khao Dawk Mali 105'', which suggests a possibility of selecting a rice cultivar having low-grain Cd.

In this study sequential extraction was used to fractionate cadmium (Cd) and zinc (Zn) from soils into six operationally defined groups; water soluble, buffer-exchangeable, carbonate, FeMn oxide, organic, and residual. Soil samples from agricultural areas surrounding Pha Te village, Mae Sot District, Tak Province, Thailand, were classified into four categories; forest soil, upland soil, upper-paddy soil and lower-paddy soil. Total soil Cd and Zn concentrations ranged from 0.63 to 30.4 mg kg-1and 14.4 to 594 mg kg-1, respectively. Cd and Zn concentrations were higher in the upper-and lower-paddy soil (5.93 to 30.4 mg kg-1for Cd and 286 to 594 mg kg-1for Zn). These soils are considered as polluted. Cd in the polluted soil was dominantly associated with the buffer-exchangeable and carbonate-bound (40 to 70 % of total Cd), while in non-polluted soils; the residual fraction was dominant (50 to 80 % of the total Cd). The major proportion of Zn (37 to 46 % of total Zn) in the non-polluted soil and the upper-paddy soil occurred in the residual fraction. On the other hand, the major proportion of total Zn in the lower-paddy soil was associated with FeMn oxides (36% of total Zn). The results show that mobility and potential bioavailability of Cd and Zn (61 and 25 %) in polluted soil were higher than in non-polluted soils (15 and 19 %in Cd and Zn, respectively). Metal distribution in different chemical fractions in these soils depended on the respective total metal concentrations.

To identify rice cultivars with low grain cadmium (Cd) levels, 42 cultivars of Thai rice (Oryza sativa L.) were cultivated in a Cd-contaminated field in the Pha Te village, Mae Sot district, Tak province, Thailand, from 2009 to 2011. Among non-glutinous and late-ripening cultivars, lower levels of Cd accumulated in the grains of RD5, RD15, and Sang Yod than in Khao Dawk Mali 105, a prevailing and popular cultivar in this area. Among glutinous and late-ripening cultivars, Khao' Niaw Ubon 1 and Khao' Niaw Ubon 2 accumulated lower Cd levels than a prevailing cultivar RD6. The findings suggest that human cadmium intake can be reduced by selecting low-Cd rice cultivars.

the aim of this work was to enhance the biodiesel quality and hydrocarbon content of green microalga B. braunii strain KMITL 2 cultivated outdoor under several salinity conditions in a batch production. the enhancement would be such that the microalgal biodiesel qualities met or exceeded the current standard so that it would be a good raw material for biodiesel production. the microalga production was in 300 L open oval ponds, among various salinity levels tested (0-20 ppt), 5 ppt was the best for hydrocarbon production, yielding 54.2 ± 0.9% hydrocarbon content and 5.1 ± 0.4 g L −1 biomass. As the microalga production was scaled up by cultivation in 3,675 L open raceway pond under the 5 ppt condition, the microalga yielded a bit higher hydrocarbon content (58.8 ± 2.9%) but much lower biomass (2.5 ± 0.5 g L −1 ). The production in both oval and raceway ponds yielded a nearly identical biodiesel property (61.06-67.42 cetane number) which exceeded the value specified in international standards. Therefore, it was concluded that B. braunii strain KMITL 2 can be batch cultivated in an open pond at optimum salinity to yield sufficient hydrocarbon and biomass for biodiesel production.

The experiment was conducted on the Cd-contaminated paddy field, two of Thai rice cultivars, the prevailing KDML105 and RD15 were included together with determining grain-Cd accumulation. The results had revealed that the RD15 contained Cd in grains not only lower than KDML105 but also lower than the critical level as proposed by Codex (0.4 mg kg-1 polished rice). Thus, the RD15 was selected as the promising low grain-Cd accumulating rice cultivar, and farmers were encouraged to grow this cultivar. The grains of prevailing and promising rice cultivars were annually collected for Cd analysis. After six-years monitoring, the results revealed that the average concentration of Cd in KDML105 was 0.658 mg kg-1, which exceeded the critical level. On the other hand, the average concentration observed in RD15 (0.127 mg kg-1) was lower than the critical level. The human dietary intake of Cd through rice consumption was calculated, comparing to the provisional tolerable weekly intake (PTWI) as adopted by FAO/WHO (7 ug Cd kg-1 BW per week), the PTWI of KDML105 was far exceeded the critical level. Contrary, the RD15 had the PTWI lower than the critical level. Present results indicated that, by cultivating RD15 the promising low-grain Cd cultivar, Cd intake together with health risk of human could be reduced.