Agricultural diffuse pollution in Thailand

Over the past two decades there have been a number of changes in Thailand, changes in the environment and quality of life for its people, changes in its communities and in the foundations of its economy. Before 1970, Thailand was a rural society in which local communities depended on the natural resources which surrounded them, and the national economy relied on the export of native crops. The sustainable use of resources was a fundamental aspect of rural life, people understood the interrelationships between the different components of their local environment and their activities which were defined by the need to protect their surrounding resources. Agriculture is the major profession and source of income for the rural poor. Land degradation and soil depletion result in low crop yields and pollution of the environment; soil erosion and landslides are found in Thailand. Nutrient uptake by crops and loss by leaching is much greater than the nutrients applied. Hence soils become less productive and it results in more land requirement for food production. Forest land declines rapidly in hilly watershed areas. Thailand is located in a tropical region and European countries are located in a temperate region. The climate is completely different, the temperature during summer in some European countries is probably almost the same as winter in Thailand. Not only is the climate in the two regions different, but land use and soil type are different also. These parameters have to be considered when studying the impact of agricultural diffuse pollution on the environment. Research studies on agricultural diffuse pollution in water resources in Thailand show that nutrient loads and pesticide residues still do not exceed the standard level. However, there was a trend showing the increase of N-NO3 in water resources, in short-term monitoring of nutrients in the east of Thailand between 1988-1990 and 1993-1995. The result showed the increase of N-NO3 from 1.60 ppm to 2.54 ppm in the same watershed and landuse areas. If the use of fertilizers and pesticides in agriculture is increased without due consideration, Thailand will face the same problem as European countries.</jats:p

Water quality of a reservoir as affected by agriculture in the east of Thailand: a preliminary study

A preliminary study on the water quality of a reservoir, affected by agriculture, in the east of Thailand was conducted during 1996-1997. Monitoring water quality of a reservoir is important because the sloping lands surrounding the reservoirs are mainly utilized for cultivating cash crops (pineapple, cassava, etc). A lot of fertilizers and agrochemicals were applied to soil and crops which can polluted the water . The results from the preliminary studied will be applied for the monitoring of the water quality in other reservoirs in the 16 pilot areas.</jats:p

Heavy metals in soils and crops in southeast Asia. 2. Thailand

A reconnaissance soil geochemical and concomitant plant survey based on 318 soil (0-15 cm) and 122 plant samples was used for the assessment of heavy metal pollution of agricultural soils and crops of Thailand. Arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn) were determined in soils using aqua regia digestion, and in plants using nitric acid digestion. Organic carbon (C), pH, electrical conductivity (EC) and available phosphorus (P) were determined on the soil samples using appropriate procedures. Results indicated that concentrations of heavy metals varied widely among the different regions of Thailand. Regression analysis between the concentrations of metals in soil (aqua regia extractable) and edible plant parts indicated a small but positive relationship for Cd in all the plants sampled in the survey (R2 = 0.081, p < 0.001). There was also a positive relationship between soil and plant Cd concentrations in rice (R2 = 0.242, p < 0.010), and negative relationships for Zn in rice (R2 = 0.385, p < 0.001), and Cu (R2 = 0.355, p < 0.001) and Zn (R2 = 0.122, p < 0.026) in glutinous rice. Principal component analysis of the soil data suggested that concentrations of As, Co, Cr, Cu, Hg, Ni and Pb were strongly correlated with concentrations of Al and Fe, which is suggestive of evidence of background variations due to changes in soil mineralogy. Thus, the evidence for widespread contamination of soils by these elements through agricultural activities is not strong. On the other hand, Cd and Zn were strongly correlated with organic matter and concentrations of available and aqua regia extractable P. This is attributed to input of contaminants in agricultural fertilisers and soil amendments (e.g. manures, composts).Bernhard A. Zarcinas, Pichit Pongsakul, Mike J. McLaughlin and Gill Cozen