The study looked at the cleanliness of the Nandujiang River's groundwater in Hainan. Researchers found that the middle section of the river had the most pollutants, especially in terms of smell and bacteria. Chemical levels like iron and phenol were too high, as were toxic substances like chlorides. The study suggests that the middle and lower parts of the river need better management to reduce pollution. If the water is used for drinking, the pollutants should be removed to meet safety standards.