Ô nhiễm đơn bào gây bệnh đường ruột (Cryptosporidum sp, Cyclospora sp and Giardia sp) và Coliform chịu nhiệt (ThC) trong rau thủy sinh ở vùng nước thải từ ruộng đến chợ tại Hà Nội (Contamination of protozoan parasites (Cryptosporidum sp, Cyclospora sp and Giardia sp) and Thermotolerant Coliforms (ThC) in wastewater-fed aquatic plants from “field to market” in Hanoi)
Tóm tắt
Nghiên cứu được tiến hành vào hai mùa mưa và khô năm 2005 ở khu vực trồng rau sử dụng nước thải và không dùng nước thải ở thành phố Hà Nội nhằm đánh giá mức độ ô nhiễm coliform chịu nhiệt (ThC) và các đơn bào đường ruột (Giardia spp., Cryptosporidium spp., và Cyclospora spp.) trong rau trồng từ ruộng đến chợ. Chúng tôi thu thập 314 mẫu rau muống, rau ăn sống, 36 mẫu nước tưới rau và 46 mẫu nước vẩy rau, đồng thời quan sát và phỏng vấn nông dân, người vận chuyển, bán lẻ và bán buôn tại các chợ ở Hà nội.
Mức độ ô nhiễm ThC ở rau trồng bằng nước thải cao hơn rau không trồng bằng nước thải. Các đơn bào đường ruột có mặt ở cả rau trồng bằng nước thải và không nước thải. Số lượng trung bình của Giardia spp. và Cryptosporidium spp. trong các mẫu rau ở vùng nước thải cao hơn vùng không nước thải. Tỉ lệ rau nhiễm Cyclospora spp. ít hơn so với Giardia spp. và Cryptosporidium spp. với tỉ lệ 4-5% ở vùng nước thải và không nước thải ở cả hai mùa. Mức độ ô nhiễm ThC trong rau muống tăng dần theo chuỗi từ ruộng đến chợ. Nước (vòi hoặc bể dự trữ) dùng để vẩy rau tại chợ có mức độ ô nhiễm ThC ~ 102 - 103/100ml. ThC cũng có mặt ở tất cả các loại rau thu thập được tại chợ với mức độ 102-103CFU/g. Tỷ lệ nhiễm các đơn bào đường ruột trong các mẫu rau tại chợ từ 7-33% với số lượng trung bình dưới 2 bào nang/g.
Nghiên cứu cho thấy sự ô nhiễm của ThC và các đơn bào đường ruột vì chúng có mặt trong rau và nước thu thập từ ruộng, trong quá trình vận chuyển từ ruộng đến chợ và tại chợ.
English abstract
The study was conducted in 2 seasons of 2005 in a peri-urban area using wastewater and another using non-wastewater in Hanoi to assess contamination level of thermotolerant coliforms (ThC) and protozoan parasites (Giardia spp., Cryptosporidium spp., và Cyclospora spp.) in vegetables from field to market. Vegetable samples including morning glory and other raw eaten vegetables, splashing water were collected, together with interviews were conducted with farmers, transportation men and traders in selected Hanoi markets.
Contamination level of ThC in vegetables cultivated in wastewater was higher than those cultivated in non-wastewater. Protozoan parasites were found in vegetables from both wastewater and non-wastewater area. Average numbers of Giardia spp. and Cryptosporidium spp. in vegetable samples from wastewater area were higher than those from non-wastewater. Percentage of vegetable samples contaminated with Cyclospora spp. was lower than that contaminated with Giardia spp. và Cryptosporidium spp. and was about 4-5% in wastewater and non-wastewater area in the 2 seasons. Contamination level of ThC in morning glory samples increased gradually from field to market. Splashing water from tap or storage containers at markets was contaminted with ThC (~ 102 - 103 CFU/100ml). ThC was also present in all kinds of vegetable samples collected at the selected Hanoi markets (102-103 CFU/g). Percentage of vegetable samples at markets contamined with protozoan parasites was from 7-33% and average number of the parasites was found to be less than 2 cysts per gram. In conclusion, the study shows that ThC and protozoan parasites were found in vegetables and splashing water from field, during transportation to market and at market.
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