Drivers of water pollutant discharge in urban agglomerations and their scale effects: Empirical analysis of 305 counties in the Yangtze River Delta

Revealing the drivers and scale effects of water pollutant discharges is an important issue in the study of the environmental consequences during urban agglomeration evolution. It is also a prerequisite for realizing collaborative water pollutant reduction and environmental governance in urban agglomerations. This paper takes 305 counties in the Yangtze River Delta (YRD) as an example and selects chemical oxygen demand (COD) and ammonia nitrogen (NH₃-N) as two distinctive pollutant indicators, using the Spatial Lag Model (SLM) and Spatial Error Model (SEM) to estimate the drivers of water pollutant discharges in 2011 and 2016. Then the Multiscale Geographically Weighted Regression (MGWR) model is constructed to diagnose the scale effect and spatial heterogeneity of the drivers. The findings show that the size of population, the level of urbanization, and the economic development level show global-level increase impacts on water pollutant discharges, while the level of industrialization, social fixed assets investment, foreign direct investment, and local fiscal decentralization are local-level impacts. The spatial heterogeneity of local drivers presents the following characteristics: Social fixed assets investment has a strong promoting effect on both COD and NH₃-N discharges in the Hangzhou-Jiaxing-Huzhou region and the coastal area of the YRD; industrialization has a promoting effect on COD discharges in the Taihu Lake basin and Zhejiang province; foreign direct investment has a local inhibitory effect on NH₃-N discharge, and the pollution halo effect is more prominent in the marginal areas of the YRD such as northern Jiangsu, northern Anhui, and southern Zhejiang; local fiscal decentralization has a noticeable inhibitory effect on COD discharge in the central areas of the YRD, reflecting the positive impacts on improved local environmental awareness and stronger constraints of multilevel environmental regulations in the urban agglomeration. Therefore, it is recommended to guide greener development to reduce the water pollutant discharge; to embed an environmental push-back mechanism in the fields of industrial production, capital investment, and financial income and expenditure; and to establish a high-quality development pattern of urban agglomerations systematically compatible with the carrying capacity of the water environment.     

MJO特征的多尺度子空间重构

通过构造两种不同类型的理想序列,将多尺度子空间变换(Multiscale Window Transform,MWT)与传统使用最多的带通滤波方法(Butterw orth)进行比较发现:MWT滤波的结果在整体上与原序列几乎完全吻合,而Butterworth的滤波结果在振幅上总是偏小;同时MWT对边界的处理也比Butterworth要好。为此使用这两种方法分别对MJO进行重构,并比较两种方法下MJO特性的差异。结果表明:在经向(meridional)传播上,两种方法得出的MJO基本类似;但在纬向(zonal)传播及其季节变化上,两种方法的结果无论在强度还是分布上都存在明显的差异,并且这种差异主要存在于西太平洋地区。本文发现:MJO波列从年初到夏季由南向北传播,从夏季到岁末传播方向却逆转成由北向南(尤其是在西太平洋地区),这一点与前人的结果迥异。