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Background: The Huangpu River serves as a vital water source for around 24 million individuals residing in the metropolitan area of Shanghai. Despite this, elevated levels of heavy metals persist in the sediments of the river, with their chemical fractionation and sources remaining inadequately understood. Results: To improve the management of heavy metal contamination, sequential extractions and zinc (Zn) isotopic compositions were utilized to evaluate pollution levels in the Huangpu River. The findings reveal that the majority of heavy metals in the river sediments are present in residual fractions, constituting an average of 67.5% for Cd, 57.6% for Cu, 60.6% for Ni, 56.2% for Pb, and 74.4% for Cr, with the exception of Zn (33.8%). Furthermore, a substantial portion of Zn, exceeding 66%, was found in acid-exchangeable, reducible, and oxidizable fractions, indicating a high potential for Zn release into aquatic ecosystems. Conclusion: Further analysis of Zn isotopes pinpointed traffic emissions, including exhaust fumes and tire wear particles (account for ~ 34.0%), along with anthropogenic emissions and fertilizer (~ 31.7%), as the major culprits behind this contamination. These findings highlight the critical need for stricter regulations to control heavy metal contamination from traffic and domestic sources within the Huangpu River basin. [ABSTRACT FROM AUTHOR]

There has been a growing interest in using cadmium (Cd) isotopes to trace the source of Cd contamination and Cd cycling in the Earth surface. Yet it remains technically challenging to precisely and efficiently determine the Cd isotopic compositions of samples with extremely low Cd concentrations due to the imperfect separation of Cd from the matrix and the interference caused by resin-derived organics when TRU Spec resin was used. In this study, we present a two-stage column chromatography system (AG-MP-1M resin + UTEVA resin) for Cd purification. Here, a Prefilter resin combined with UTEVA resin effectively purifies Cd from Sn after the separation of Cd by AG-MP-1M column while keeping the phosphorous organic compounds to an acceptable level. In contrast to TRU Spec resin, which is prone to leaking through the Prefilter resin, we find that UTEVA resin is effectively retained by the Prefilter resin, thus avoiding the P-related anomalous shifts in the Cd isotope measurement (P/Cd < 1). UTEVA resin also exhibits a comparable capacity for purifying Cd from Sn and Mo when compared to TRU Spec resin. The recovery of the two-stage column system is generally higher than 99% and the procedural blank accounting for sample digestion and chemical purification is lower than 20 pg. The Cd isotopic compositions of several reference materials are determined using double spike MC-ICP-MS, with a 111Cd–113Cd double spike pair optimized for the 111Cd, 112Cd, 113Cd, and 114Cd inversion. The δ114/110Cd values of these reference materials relative to NIST SRM 3108 agree within analytical uncertainty with previous studies. The long-term external precision of δ114/110Cd determined based on replicated measurements of BCR-2 is 0.04‰ (n = 10, 2 SD) for a minimum sample size of 10 ng. Our study thus provides an efficient two-stage column system for determining the Cd isotopic compositions of geological samples with relatively low Cd concentrations. [ABSTRACT FROM AUTHOR]

Despite extensive investigation, the nature and causes of the Mid-Pleistocene Transition remain enigmatic. In this work, we assess its linkage to asynchronous development of bipolar ice sheets by synthesizing Pleistocene mid- to high-latitude proxy records linked to hemispheric ice sheet evolution. Our results indicate substantial growth of the Antarctic Ice Sheets (AISs) at 2.0 to 1.25 million years ago, preceding the rapid expansion of Northern Hemisphere Ice Sheets after ~1.25 million years ago. Proxy-model comparisons suggest that AIS and associated Southern Ocean sea ice expansion can induce northern high-latitude cooling and enhanced moisture transport to the Northern Hemisphere, thus triggering the Mid-Pleistocene Transition. The dynamic processes involved are crucial for assessing modern global warming that is already inducing asynchronous bipolar melting of ice sheets.