II. Diễn biến môi tr−ờng trầm tích
7. Cao Thị Thu Trang và nnk, 1999 Phân tích D− l−ợng Hoá chất bảo vệ thực vật
cơ lo trong môi tr−ờng n−ớc - trầm tích - sinh vật biển. Báo cáo đề tài cấp cơ sở Viện Tài nguyên và Môi tr−ờng biển. L−u tại Viện Tài nguyên và Môi tr−ờng biển.
Summary
Chlorine pesticides in sediment environment at Tam Giang - Cầu Hai lagoon (Thua Thien Hue province)
Nguyen Manh Thang, Nguyen Huu Cu, Nguyen Thi Kim Anh
The Tam Giang - Cau Hai (Thua Thien Hue) is the biggest and typical lagoon in our country which provides great values in term of use and science. However, in the past recent years, it has been strongly exploited which have a great impact on environment quality including sediment. One of the causes is the Chlorine pesticides from agriculture acitivities around the lagoon and the upstream rivers having the basin is Tam Giang - Cau Hai lagoon. The amount of Chlorine pesticides in the sediment environment at Tam Giang Cau Hai is found with the appearance of 7/7 analysed compound: Lindan, Aldrin, Endrin, Dieldrin, 4,4’ - DDE, 4,4’ - DDD and 4,4’ - DDT from the form of race to quantification, the popular ones of which in dry season are Endrin, 4,4’ - DDD, 4,4’ - DDT and Lindan, Endrin, Dieldrin, 4,4’ - DDD, 4,4’ - DDT in rainy season. According to space, the estuary areas of OLau, DaiGiang, Huong have a higher chlorine pesticides than other areas and it tends to decrease gradually from the north to the south. The total chlorine pesticides in sediment is recorded to be higher in rainy season than in dry season. The pesticides recorded at the dry season is fluctuated from 1.377 to 5.956 ppb and from 2.312 to 15.653 ppb in rainy season. In the group of pesticides found in the sediment, the amount of Endrin, 4,4’ - DDD is higher than the environment set standard. Of which the amount of Endrin is higher the set standard from 2.8 - 36 times ; 4,4’ - DDD exceed the set standard from 1.05 - 3.35 times at Thuan An inlet, Thuy Tu lagoon in dry season and O Lau estuary (Tam Giang), Thuan An (Tam Giang), Dai Giang estuary (Cầu Hai lagoon) in rainy season. However, this amount just only exceeds the set standard which starts to impact on ecosystem (low ISQG), it has not yet exceeded the immediate impacting standard (high ISQG), however, it is necessary to have plan to control waste sources from agriculture activities around the lagoon and the upstream river to limit their negative impact on the eco - environment.