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East Asian monsoon variability in the Pliocene warm world has not been sufficiently studied because of the lack of direct records. We present a high-resolution precipitation record from Pliocene fluvial-lacustrine sequences in the Weihe Basin, Central China, a region sensitive to the East Asian monsoon. The record shows an abrupt monsoon shift at ~4.2 million years ago, interpreted as the result of high-latitude cooling, with an extratropical temperature decrease across a critical threshold. The precipitation time series exhibits a pronounced ~100–thousand year periodicity and the presence of precession and half-precession cycles, which suggest low-latitude forcing. The synchronous phase but mismatched amplitudes of the East Asian monsoon precipitation proxy and eccentricity suggest a nonlinear but sensitive precipitation response to temperature forcing in the Pliocene warm world. These observations highlight the role of high- and low-latitude forcing of East Asian monsoon variations on tectonic and orbital time scales.

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Soil salinization is an important driver of land degradation and has been a major factor inhibiting agricultural production and development in the southern coastal area of Laizhou Bay. In this study, 3‐D and 2‐D geostatistics were respectively used to evaluate the spatial distribution of soil salinity and groundwater total dissolved solids (TDS) and depth. Results showed that soil electrical conductivity differed greatly within the same soil layer, and the difference in average electrical conductivity of different soil layers was relatively small. The mean value of TDS exceeded 3.0 g L−1 and the mean value of groundwater depth was 13.359 m. The geographic distribution showed that the soil salinity gradually decreased from the north to the south horizontally, and the soil salinity showed a bottom accumulation tendency vertically. Over 90% of the study area has TDS values exceeding 1.0 g L−1, and approximately one‐third of the area had a groundwater depth less than 3.0 m. TDS and groundwater depth had good correlations with soil salinity, with coefficients of determination of 0.544 and 0.572, respectively. Changes in vegetation corresponded to changes in soil salinity. Soil salinity gradually decreased perpendicular to coastal lines in tidal flats without vegetative coverage to inland agricultural areas of wheat and vegetables. Soil salinization in the study area is mainly slight and moderate. Reasonable regional management measures are conducive to improving land economic benefits. The results provide a theoretical basis and reference for the partition, improvement, management of saline soil, and support for land degradation control.

Sediments are an important sink for heavy metal pollutants on account of their strong adsorption capacity. Elevated content of Cu was observed in the Chengdao area of the Yellow River Delta, where the surface sediment is mainly silt and is prone to be liquefied under hydrodynamic forces. The vertical transport of fine particles, along with pore water seepage, during the liquefaction process could promote the migration and diffusion of Cu from the interior of sediment. The present study involved a series of wave flume experiments to simulate the migration and diffusion of Cu from the interior of sediment in the subaqueous Yellow River Delta area under wave actions. The results indicated that sediment liquefaction significantly promoted the release of Cu from internal sediment to overlying water. The variations of Cu concentrations in the overlying water were opposite to the suspended sediment concentrations (SSCs). The sediment liquefaction caused high initial rises of SSCs, but led to a rapid decline of dissolved Cu concentration at the initial period of sediment liquefaction due to the adsorption by fine particles. Afterwards, the SSCs slightly increased and then gradually decreased. Meanwhile, the dissolved Cu concentration generally kept increasing under combined effects of intensively mix of sediment and overlying water, pore water seepage, and desorption. The dissolved Cu concentration in the overlying water during sediment liquefaction phase was 1.5–2.2 times that during the consolidation phase. Sediment liquefaction also caused vertical diffusion of Cu in sediment and the diffusion depth was in accordance with the liquefaction depth. The results of the present study may provide reference for the environmental management in the study area.