Lake Sediment Archive Reveals a Distinct Response to Anthropogenic Pb and Zn Deposition with Historical Periods: Pb-Zn Isotope Evidence

Isotopic insights and integrated analysis for heavy metal levels, ecological risks, and source apportionment in river sediments of the Qinghai-Tibet Plateau

The research was carried out to examine the pollution characteristics, ecological risk, and origins of seven heavy metals (Hg, As, Pb, Cu, Cd, Zn, and Ni) in 51 sediment samples gathered from 8 rivers located on the Qinghai-Tibet Plateau (QTP) in China. The contents of Hg and Cd were 5.0 and 1.1 times higher than their background values, respectively. The mean levels of other measured heavy metals were below those found naturally in the local soil. The enrichment factor showed that the study area exhibited significantly enriched Hg with 70.6% sampling sites. The Cd contents at 19.6% of sampling sites were moderately enriched. The other sampling sites were at a less enriched level. The sediments of all the rivers had a medium level of potential ecological risk. Hg was the major ecological risk factor in all sampling sites, followed by Cd. The findings from the positive matrix factorization (PMF) analysis shown agricultural activities, industrial activities, traffic emissions, and parent material were the major sources. The upper, middle, and low reaches of the Quanji river had different Hg isotope compositions, while sediments near the middle reaches were similar to the δ202Hg of the industrial source. At the upstream sampling sites, the Hg isotope content was very close to the background level. The results of this research can establish a strong scientific sound to improve the safety of the natural circumstances of rivers on the QTP.

Evidence of economic development revealed in centennial scale sedimentary records of organic pollutants in Huguangyan Marr Lake

Sedimentary records of polycyclic aromatic hydrocarbons (PAHs) and phthalates could reflect energy consumption and industrial production adjustment. However, there is limited knowledge about their effects on variations of PAH and phthalate compositions in the sediment core. The PAH and phthalate sedimentary records in Huguangyan Maar Lake in Guangdong, China were constructed, and random forest models were adopted to quantify the associated impact factors. Sums of sixteen PAH (∑16 PAH) and seven phthalate (∑7 PAE) concentrations in the sediment ranged from 28.8 to 1110 and 246-4290 μg/kg dry weight in 1900-2020. Proportions of 5-6 ring PAHs to the ∑16 PAHs increased from 32.0 %-40.7 % in 1900-2020 with increased coal and petroleum consumption, especially after 1980. However, those of 2-3 ring PAHs decreased from 30.7 % to 23.6 % due to the biomass substitution with natural gas. The proportions of bis (2-ethylhexyl) phthalate to the ∑7 PAEs decreased from 52.3 %-29.1 % in 1900-2020, while those of di-isobutyl phthalate increased (13.7 % to 42.3 %). The shift from traditional plasticizers to non-phthalates drove this transformation, though the primary plastic production is increasing. Our findings underscore the effectiveness of optimizing energy structures and updating chemical products in reducing organic pollution in aquatic environments.

Controlling factors and sources-specific ecological risks associated with toxic metals in core sediments from cascade reservoirs in Southwest China

Toxic metals (TMs) in reservoir sediments pose significant risks to ecosystem security and human safety, yet their presence in the cascade reservoirs of the Lancang River remains understudied. This research examined TMs in core sediments from the Manwan (MW) and Dachaoshan (DCS) cascade reservoirs, aiming to elucidate contamination characteristics, controlling factors, and source-specific ecological risks. The study revealed that the concentrations of As, Cd, Cr, Cu, Hg, Ni, and Zn in the MW Reservoir (37.3, 0.54, 95.1, 44.0, 0.09, 44.8, and 135.7 mg/kg) were notably higher compared to the DCS Reservoir (14.6, 0.30, 82.6, 31.0, 0.08, 36.6, and 108.7 mg/kg). While both reservoirs demonstrated elevated contamination levels of Cd and Hg, the MW Reservoir also exhibited high levels of As, whereas the DCS Reservoir showed relatively high levels of Pb. Mining activities in upstream metal deposits significantly correlated Cd, Hg, and Zn in the MW Reservoir with sulfur. In both reservoir sediments, Cr and Ni displayed a greater affinity for iron oxides, while As, Cd, Cu, Hg, and Zn showed more affinity with manganese oxides. Ecological risk index (RI) values in half of the sediments from the MW Reservoir ranged from 300 to 600, denoting a significant ecological risk. Conversely, in the DCS Reservoir, 93.3 % of the sediments exhibited RI values between 150 and 300, signifying a moderate ecological risk. Source-oriented ecological risks highlighted the need for particular attention to Cd from anthropogenic sources in the MW Reservoir. These findings underscore the importance of implementing measures for TM contamination prevention and control, contributing to strategic planning for sustainable water resource management in the Lancang-Mekong River.

Arsenic and cadmium simultaneous immobilization in arid calcareous soil amended with iron-oxidizing bacteria and organic fertilizer

Immobilization stands as the most widely adopted remediation technology for addressing heavy metal(loid) contamination in soil. However, it is crucial to acknowledge that this process does not eliminate pollutants; instead, it confines them, potentially leaving room for future mobilization. Presently, our comprehension of the temporal variations in the efficacy of immobilization, particularly in the context of its applicability to arid farmland, remains severely limited. To address this knowledge gap, our research delves deep into the roles of iron-oxidizing bacteria (FeOB) and organic fertilizer (OF) in the simultaneous immobilization of arsenic (As) and cadmium (Cd) in soils. We conducted laboratory incubation and field experiments to investigate these phenomena. When OF was combined with FeOB, a noteworthy transformation of available As and Cd into stable species, such as the residual state and combinations with Fe-Mn/Al oxides, was observed. This transformation coincided with changes in soil properties, including pH, Eh, soluble Fe, and dissolved organic carbon (DOC). Furthermore, we observed synergistic effects between available As and Cd when treated with bacteria and OF individually. The stabilization efficiency of As and Cd, as determined by the Toxicity Characteristic Leaching Procedure, reached its highest values at 33.39 % and 24.67 %, respectively, after 120 days. Nevertheless, the formation of iron‑calcium complexes was disrupted due to pH fluctuations. Hence, long-term monitoring and model development are essential to enhance our understanding of the remediation process. The application of organic fertilizer and the use of FeOB in calcareous soil hold promise for the restoration of polluted soil and the maintenance of soil health by mitigating the instability of heavy metals(loid).

Multimedia distribution, partitioning, sources, comprehensive toxicity risk and co-occurrence network characteristics of trace elements in a typical Chinese shallow lake with high antibiotic risk

Although the combined pollution of trace elements and antibiotics has received extensive attention, the fate and toxicity risk of trace elements with high antibiotic risk are still unclear. The multimedia distributions, partitioning, sources, toxicity risks and co-occurrence network characteristics of trace elements in surface water (SW), overlying water (OW), pore water (PW) and sediment (Sedi) samples of 61 sites from Baiyangdian (BYD) Lake were investigated. The trace elements in the SW and OW are derived mainly from traffic and agricultural sources, and those in PW and Sedi samples are primarily from lithogenic and industrial sources. The total toxicity risk index (TRI) of nine trace elements (ΣTRI) in Sedi samples showed a very high toxicity risk (18.35 ± 8.84), and a high combined pollution toxicity risk (ΣΣTRI) was observed in PW (149.17 ± 97.52) and Sedi samples (46.37 ± 24.00). The co-occurrence network from SW to PW became more vulnerable. Generally, total antibiotics and TP may be keystones of trace elements in water and sediment. The high antibiotic risk significantly influenced ΣΣTRI in water samples but not in Sedi samples. The findings provide new implications for the monitoring and control of combined antibiotic-trace element pollution in shallow lakes.

Metals and microorganisms in a Maar lake sediment core indicating the anthropogenic impact over last 800 years

A closed Maar lake, receiving mostly atmospheric deposition, offers a unique setting for investigating the impact of human activities on the environment. In this study, we aimed to investigate the historical record of metals in core sediments of Maar Lake in Huguangyan (HGY), Southeast China, and elucidate the possible microbial responses to anthropogenic metal stress. Five stages were divided according to the historical record of metals and corresponding distribution of microbial community, among which Pb and Sn showed a peak value around 1760 CE, indicating the ancient mining and smelting activities. Since the 1980s, a substantial enrichment of metals such as Zn, As, Mo, Cd, Sn, Sb, and Pb was observed, due to the rapid industrial growth in China. In terms of microorganisms, Chloroflexi phylum, particularly dominated by Anaerolineales, showed significant correlations with Pb and Sn, and could potentially serve as indicator species for mining and smelting-related contamination. Desulfarculales and Desulfobacterales were found to be more prevalent in recent period and exhibited positive correlations with anthropogenic metals. Moreover, according to the multivariate regression modeling and variance decomposition analysis, Pb and Sn could regulate Anaerolineales and further pose impact on the carbon cycle; while sulfate-reducing bacteria (SRB) could response to anthropogenic metals and influence sulfur cycle. These findings provide new insights into the interaction between metals and microbial communities over human history.