ALBERT

Description: Human society and ecosystems worldwide are increasinAagly threatened by water shortages. Despite numerous studies of climatic impacts on water availability, little is known about the influences of socioeconomic development on streamflow and water sustainability. Here, we show that the streamflow from the Yellow River to the sea has decreased by more than 80% in total over the last 60 years due to increased water consumption by agricultural, industrial and urban developments (76% of the streamflow decrease, similarly hereinafter), decreased precipitation (13%), reservoir construction (6%) and revegetation (5%). We predict that if the past trends in streamflow will continue, year-round dry-up in the lower Yellow River will commence in the late 2020s or early 2030s, unless effective countermeasures such as water diversion from the Yangtze River are taken. These results suggest that streamflow in semiarid basins is highly vulnerable to human impacts and that streamflow decline would in turn hinder further socioeconomic development and endanger river-sea ecosystems.

Description: Rare earth elements (REEs) and yttrium (Y), together known as REY, are extremely enriched in deep-sea pelagic sediments, attracting much attention as a promising new REY resource. To understand the influence of hydrothermal processes on the enrichment of REY in deep-sea sediments from the eastern South Pacific Ocean, we conducted detailed lithological, bulk sediment geochemical, and in situ mineral geochemical analyses on gravity core sample S021GC17 from the Yupanqui Basin of eastern South Pacific. The REY-rich muds of S021GC17 are dark-brown to black zeolitic clays with REY contents (ΣREY) ranging from 1057 to 1882 ppm (average 1329 ppm). The REY-rich muds display heavy rare earth elements (HREE) enriched patterns, with obvious depletions in Ce, and positive anomalies of Eu in Post-Archean Australian Shale (PAAS)-normalized REE diagrams. In contrast, the muds of S021GC17 show light rare earth elements (LREE) enriched patterns and positive anomalies of Ce and Eu in the seawater-normalized REE diagrams. Total REY abundances in the core show positive correlations with CaO, P2O5, Fe2O3, and MnO concentrations. In situ analyses of trace element contents by laser ablation-inductively coupled plasma–mass spectrometry (LA-ICP-MS) demonstrate that bioapatite fossils contain high REY concentrations (998 to 22,497 ppm, average 9123 ppm), indicating that they are the primary carriers of REY. The in situ Nd isotope values of bioapatites are higher than the average values of seawater in Pacific Ocean. Fe–Mn micronodules are divided into hydrogenetic and diagenetic types, which have average REY concentrations of 1586 and 567 ppm, respectively. The high contents of Fe-Mn-Ba-Co-Mo, the positive correlations between ΣREY and Fe-Mn, the ratios of Fe/Ti and Al/(Al + Fe + Mn), and the LREE-enriched patterns in the REY-rich muds, combined with high Nd isotope values shown by bioapatite fossils, strongly indicate that the hydrothermal fluids have played an important role in the formation of the REY-rich sediments in the eastern South Pacific Ocean.