Indigenous fire-managed landscapes in southeast Australia during the Holocene - new insights from the Furneaux Group islands, Bass Strait

Indigenous land use and climate have shaped fire regimes in southeast Australia during the Holocene, although their relative influence remains unclear. The archaeologically attested mid-Holocene decline in land-use intensity on the Furneaux Group islands (FGI) relative to mainland Tasmanian and SE Australia presents a natural experiment to identify the roles of climate and anthropogenic land use. We reconstruct two key facets of regional fire regimes, biomass (vegetation) burned (BB) and recurrence rate of fire episodes (RRFE), by using total charcoal influx and charcoal peaks in palaeoecological records, respectively. Our results suggest climate-driven biomass accumulation and dryness-controlled BB across southeast Australia during the Holocene. Insights from the FGI suggest people elevated the recurrence rate of fire episodes through frequent cultural burning during the early Holocene and reduction in recurrent Indigenous cultural burning during the mid-late Holocene led to increases in BB. These results provide long-term evidence of the effectiveness of Indigenous cultural burning in reducing biomass burned and may be effective in stabilizing fire regimes in flammable landscapes in the future

Simultaneous removal of PAHs and metal contaminants from water using magnetic nanoparticle adsorbents

Many industrial wastewaters are contaminated with both heavy metal ions and organic compounds, posing a major threat to public health and the environment. In this study, magnetic nanoparticle adsorbents, namely Mag-PCMA-T, which contain a maghemite core and a silica mesoporous layer that permanently confines surfactant micelles within the mesopores, were synthesized to achieve simultaneous removal of polycyclic aromatic hydrocarbons (PAHs) (1mg/L) and metal contaminants (1mg/L). The individual removal efficiency of Cd(2+) and acenaphthene using Mag-PCMA-T was evaluated under a range of initial ion concentrations and adsorbent dosages, as well as the competitive adsorption with Cd(2+) and acenaphthene simultaneously present. The isotherms and kinetics of Cd(2+) and acenaphthene sorption onto Mag-PCMA-T were determined. Mag-PCMA-T removed >85% of the acenaphthene in <30min, with relatively high sorption capacity (up to 1060mg/kg). Mag-PCMA-T also exhibited high sorption capacity for Cd(2+) (up to 2250mg/kg). The simultaneous sorption performance was stable across a wide pH range (4-9) as well as in the presence of competitive metal ions (Ca(2+) and Mg(2+)) or natural organic matters. The Mag-PCMA-T can be regenerated and reused, providing a sustainable, fast, convenient, and efficient approach for water treatment

Heteroaggregation of nanoparticles with biocolloids and geocolloids

The application of nanoparticles has raised concern over the safety of these materials to human health and the ecosystem. After release into an aquatic environment, nanoparticles are likely to experience heteroaggregation with biocolloids, geocolloids, natural organic matter (NOM) and other types of nanoparticles. Heteroaggregation is of vital importance for determining the fate and transport of nanoparticles in aqueous phase and sediments. In this article, we review the typical cases of heteroaggregation between nanoparticles and biocolloids and/or geocolloids, mechanisms, modeling, and important indicators used to determine heteroaggregation in aqueous phase. The major mechanisms of heteroaggregation include electric force, bridging, hydrogen bonding, and chemical bonding. The modeling of heteroaggregation typically considers DLVO, X-DLVO, and fractal dimension. The major indicators for studying heteroaggregation of nanoparticles include surface charge measurements, size measurements, observation of morphology of particles and aggregates, and heteroaggregation rate determination. In the end, we summarize the research challenges and perspective for the heteroaggregation of nanoparticles, such as the determination of αhetero values and heteroaggregation rates; more accurate analytical methods instead of DLS for heteroaggregation measurements; sensitive analytical techniques to measure low concentrations of nanoparticles in heteroaggregation systems; appropriate characterization of NOM at the molecular level to understand the structures and fractionation of NOM; effects of different types, concentrations, and fractions of NOM on the heteroaggregation of nanoparticles; the quantitative adsorption and desorption of NOM onto the surface of nanoparticles and heteroaggregates; and a better understanding of the fundamental mechanisms and modeling of heteroaggregation in natural water which is a complex system containing NOM, nanoparticles, biocolloids and geocolloids

Simultaneous removal of cadmium and nitrate in aqueous media by nanoscale zerovalent iron (nZVI) and Au doped nZVI particles

Nanoscale zerovalent iron (nZVI) has demonstrated high efficacy for treating nitrate or cadmium (Cd) contamination, but its efficiency for simultaneous removal of nitrate and Cd has not been investigated. This study evaluated the reactivity of nZVI to the co-contaminants and by-product formation, employed different catalysts to reduce nitrite yield from nitrate, and examined the transformation of nZVI after reaction. Nitrate reduction resulted in high solution pH, negatively charged surface of nZVI, formation of Fe3O4 (a stable transformation of nZVI), and no release of ionic iron. Increased pH and negative charge contributed to significant increase in Cd(II) removal capacity (from 40 mg/g to 188 mg/g) with nitrate present. In addition, nitrate reduction by nZVI could be catalyzed by Cd(II): while 30% of nitrate was reduced by nZVI within 2 h in the absence of Cd(II), complete nitrate reduction was observed in the presence of 40 mg-Cd/L due to the formation of Cd islands (Cd(0) and CdO) on the nZVI particles. While nitrate was reduced mostly to ammonium when Cd(II) was not present or at Cd(II) concentrations ≥ 40 mg/L, up to 20% of the initial nitrate was reduced to nitrite at Cd(II) concentrations < 40 mg/L. Among nZVI particles doped with 1 wt. % Cu, Ag, or Au, nZVI deposited with 1 wt. % Au reduced nitrite yield to less than 3% of the initial nitrate, while maintaining a high Cd(II) removal capacity

Highly efficient and irreversible removal of cadmium through the formation of a solid solution

Sulfur-containing materials are very attractive for the efficient decontamination of some heavy metals. However, the effective and irreversible removal of Cd2+, coupled with a high uptake efficiency, remains a great challenge due to the relatively low bond dissociation energy of CdS. Herein, we propose a new strategy to overcome this challenge, by the incorporation of Cd2+ into a stable ZnxCd1-xS solid solution, rather than into CdS. This can be realised through the adsorption of Cd2+ by ZnS nanoparticles, which have exhibited a Cd2+ uptake capacity of approximate 400 mg g−1. Through this adsorption mechanism, the Cd2+ concentration in a contaminated solution could effectively be reduced from 50 ppb to 80% uptake capacity for Cd2+, compared with only 9% uptake capacity for similarly-aged FeS particles. This work reveals a new mechanism for Cd2+ removal with ZnS and establishes a valuable starting point for further studies into the formation of solid solutions for hazardous heavy metal removal applications

Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.

Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability