The Beibu Gulf (also named the Gulf of Tonkin), located in the northwest of the South China Sea, is representative of a bay suffering from turbulence and contamination associated with rapid industrialization and urbanization. In this study, we aim to provide the novel baseline levels of heavy metals for the research area. Concentrations of five heavy metals (i.e., Cu, Pb, Zn, Cd and Cr) were determined in surface sediments from 35 sites in the eastern Beibu Gulf. The heavy metal content varied from 6.72 to 25.95 mg/kg for Cu, 16.99 to 57.98 mg/kg for Pb, 73.15 to 112.25 mg/kg for Zn, 0.03 to 0.12 mg/kg for Cd, and 20.69 to 56.47 mg/kg for Cr, respectively. With respect to the Chinese sediment quality criteria, sediments in the eastern Beibu Gulf have not been significantly affected by coastal metal pollutions. The results deduced from the geoaccumulation index (I_geo) showed that the study area has been slightly polluted by Pb, which might be caused by non-point sources. Relatively high concentrations of Cu, Pb and Cd were found around the coastal areas of Guangxi province, the Leizhou Peninsula and the northwest coast of Hainan Island, whereas the highest concentrations of Zn and Cr were found on the northwest coast of Hainan Island. Spatial distribution patterns of the heavy metals showed that bioavailable fractions of Pb were higher than in the residual fractions, while Cu and Cd concentrations in exchangeable and carbonate fractions were relatively higher than those in the bioavailable fractions. Hierarchical clustering analysis suggested that the sampling stations could be separated into three groups with different geographical distributions. Accompanying their similar spatial distribution in the study area, significant correlation coefficients among Cu, Cd and Pb were also found, indicating that these three metals might have had similar sources. Overall, the results indicated that the distribution of these heavy metals in the surface sediments collected from the Beibu Gulf was complex.

High‐resolution stalagmite oxygen isotope (δ¹⁸O) records are widely employed in palaeoclimate studies as indicators of East Asian Monsoon intensity in southern China. A key issue is whether the East Asian Monsoon or other factors control δ¹⁸O in precipitation in southern China, which requires modern observations to confirm. To understand which factors control the dual isotopes (δD and δ¹⁸O) of precipitation in southern China, δD and δ¹⁸O were measured from 412 precipitation events (including 144 rainwater samples from a total of 43 typhoon events) from May 2015 to April 2020 in Zhanjiang, a tropical city frequently affected by typhoon events in southern China. The overall relationship between δD and δ¹⁸O can be expressed as δD = 8.961 δ¹⁸O + 6.235; significantly lower intercept and larger slope of this relationship compared to these of the global meteoric water line (GMWL) and the China meteoric water line (CMWL). Remarkably, significantly low D‐excess and the lowest δD and δ¹⁸O occurred in the typhoon periods, suggesting that typhoon events could bring large amounts of remote moisture to this tropical city from the Western Pacific and South China Sea. The moisture from remote oceans would affect precipitation with the lowest δ¹⁸O and D‐excess, which could be responsible for the deviation of the slope and intercept from those of the CMWL and GMWL. Therefore, variations of the δ¹⁸O in precipitation are intensively influenced by typhoons, not by the East Asian Monsoon, providing new understanding for the interpretation of palaeo‐isotope data in southern China.