No abstract

Recently, Jia et al. employed the index, modified remote sensing ecological index (MRSEI), to evaluate the ecological quality of the Qaidam Basin, China. The MRSEI made a modification to the previous remote sensing-based ecological index (RSEI), which is a frequently used remote sensing technique for evaluating regional ecological status. Based on the investigation of the ecological implications of the three principal components (PCs) derived from the principal component analysis (PCA) and the case study of the Qaidam Basin, this comment analyzed the rationality of the modification made to RSEI by MRSEI and compared MRSEI with RSEI. The analysis of the three PCs shows that the first principal component (PC1) has clear ecological implications, whereas the second principal component (PC2) and the third principal component (PC3) have not. Therefore, RSEI can only be constructed with PC1. However, MRSEI unreasonably added PC2 and PC3 into PC1 to construct the index. This resulted in the interference of each principal component. The addition also significantly reduced the weight of PC1 in the computation of MRSEI. The comparison results show that MRSEI does not improve RSEI, but causes the overestimation of the ecological quality of the Qaidam Basin. Therefore, the modification made by MRSEI is questionable and MRSEI is not recommended to be used for regional ecological quality evaluation.

Understanding the ecosystem risk of contaminants in the surface water of lakes in scenic areas is important for environmental management. Here, a comprehensive ecological risk assessment evaluation method was established to assess the ecological risk of 14 water quality indicators of Baiyangdian Lake in the spring, summer, and autumn. The results show that the indices of ammonia nitrogen and permanganate exceed the Class III standard limit for water quality. Baiyangdian Lake is generally in a state of mesotrophication, and some areas are slightly eutrophic; the degree of eutrophication is higher in the summer and autumn than in the spring. The lake water at the inlet is eutrophic and polluted, with an inferior water quality. Heavy metals are almost not detected in Baiyangdian Lake. The heavy metal pollution indices of Nanliuzhuang and Caiputai are slightly higher than those of other areas. The ecological risk quotient of petroleum is high. The comprehensive ecological risk of the Baiyangdian Lake is at Level 4, owing to the continuous development of aquaculture and tourism in recent years. We should start the monitoring, management, and strengthening of water quality supervision to achieve the ecological and environmental planning goals of Baiyangdian Lake.