ĐÁNH GIÁ KHẢ NĂNG TỰ LÀM SẠCH NƯỚC HỒ TÂY, HÀ NỘI

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Tác giả: Anh Tú Cái, Văn Quy Lê, Thị Thu Trang Nguyễn

Ngôn ngữ: vie

Ký hiệu phân loại:

Thông tin xuất bản: Tạp chí Khoa học Biến đổi khí hậu, 2022

Mô tả vật lý: tr.62-68

Bộ sưu tập: Metadata

ID: 336867

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Hồ Tây là hồ tự nhiên tọa lạc ở Tây Bắc Hà Nội với diện tích hơn 500 ha có chu vi 18 km. Cũng như các thủy vực khác, nước hồ Tây vẫn còn khả năng tự làm sạch với điều kiện liên quan đến một số yếu tố trong đó có lượng oxy hòa tan trong nước hồ (DO). Khi lượng chất thải tăng, khả năng tự làm sạch của hồ không đáp ứng, kéo theo suy giảm DO trong nước, từ đó dẫn đến những thay đổi bất lợi đến đời sống của thủy sinh vật. DO được sử dụng như một thông số để đánh giá mức độ ô nhiễm chất hữu cơ của các nguồn nước. DO còn có ý nghĩa lớn đối với quá trình tự làm sạch của hồ. Khi DO giảm thấp (<
4 mg/l) cá và các động vật thủy sinh khác bị chết, nước sẽ trở nên có màu đen và bốc mùi hôi thối. Nguồn cung cấp oxy chủ yếu là từ khí quyển và từ sự quang hợp của các loài thực vật trong nước. Sự tụt giảm oxy được gây ra do nhiều yếu tố, trong đó quan trọng nhất là nhu cầu oxy sinh học (BOD). Kết quả cho thấy nếu tình trạng dư thừa chất dinh dưỡng trong hồ kéo dài có thể ảnh hưởng đến độ dày thiếu khí của lớp nước đáy hồ và sẽ tiếp tục di chuyển lên phía trên thuộc lớp nước mặt của hồ. Tình trạng này có thể kéo theo làm giảm khả năng tự làm sạch của hồ. Khả năng tự làm sạch của hồ được đánh giá dựa trên tỷ lệ giá trị hằng số tốc độ nạp oxy (K2) và hằng số tốc độ khử oxy (K1). Giá trị tỷ lệ tự làm sạch (K2/K1) Hồ Tây trung bình vào mùa khô là 1,6, mùa mưa là 2,24 và thuộc phạm vi có khả năng tự làm sạch (>
1).West Lake is a natural lake located in the Northwest of Hanoi with an area of more than 500 hectares with a circumference of 18 km. Like other water bodies, West Lake water is still capable of self-cleaning with conditions related to a number of factors including the dissolved oxygen (DO) value of lake water. When the amount of waste increases, the self-cleaning capacity of the lake does not respond, leading to a decrease in DO in the water, thereby leading to adverse changes to aquatic life. DO is used as a parameter to assess the level of organic pollution of water sources. DO also has great significance for the self-cleaning process of the lake. When DO drops low (<
4 mg/l) fish and other aquatic animals die, the water becomes black and has a foul odor. The main source of oxygen is from the atmosphere and from photosynthesis by aquatic plants. Oxygen depletion is caused by many factors, the most important of which is Biological Oxygen Demand (BOD). The results indicated that if the condition of excess nutrients in the lake is prolonged, it can affect the anoxic thickness of the lake bottom layer and will continue to move upward in the surface water of the lake. This situation can lead to a decrease in the self-cleaning capacity of the tank. The self-cleaning capacity of the tank is evaluated based on the ratio of the value of the air intake rate constant (K2) and the oxygen reduction rate constant (K1). The value of self-cleaning rate (K2/K1) on West Lake in dry season is 1.6 and in rainy season is 2.24 which belongs to the self-cleaning range (>
1).

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