The complexities of decision-making in food waste valorization: A critical review.

The efficient utilization of food waste (FW) resources through Food Waste Valorization (FWV) has received increasing attention in recent years. Various decision-making studies have been undertaken to facilitate FWV implementation, such as the studies on decision-making framework and FWV technology assessment. Food waste hierarchy is a widely discussed framework in FW management, but it was found too simplified and does not always contribute positively to environmental sustainability. Moreover, decision-making studies in FWV often focus on specific aspects of the food system and employ distinctive decision-making approaches, making it difficult to compare the results from different studies. Therefore, our literature review is conducted to provide a comprehensive understanding of FWV decision-making. This study identifies what decisions are needed, and three levels of decisions are revealed: system-level, FW stream-level, and FWV option-level. The assessment approaches and criteria used to support decision-making in FWV are also collected and analyzed. Building upon these findings, an hourglass model is synthesized to provide a holistic illustration of decision-making in FWV. This study untangles the complexities of FWV decision-making and sheds light on the limitations of current studies. We anticipate this study will make more people realize that FWV is a multidisciplinary issue and requires the collective participation of researchers, practitioners, policymakers, and consumers. Such collective engagement is essential to effectively address practical challenges and propel the transition of the current food system toward a more resource-efficient paradigm.

Source apportionment of heavy metal(loid)s in sediments of a typical karst mountain drinking-water reservoir and the associated risk assessment based on chemical speciations.

As important place for water storage and supply, drinking-water reservoirs in karst mountain areas play a key role in ensuring human well-being, and its water quality safety has attracted much attention. Source apportionment and ecological risks of heavy metal(loid)s in sediments of drinking-water reservoir are important for water security, public health, and regional water resources management, especially in karst mountain areas where water resources are scarce. To expound the accumulation, potential ecological risks, and sources of heavy metal(loid)s in a drinking-water reservoir in Northwest Guizhou, China, the surface sediments were collected and analyzed based on the combined use of the geo-accumulation index (Igeo), sequential extraction (BCR), ratios of secondary phase and primary phase (RSP), risk assessment code (RAC), modified potential ecological risk index (MRI), as well as the positive matrix factorization methods. The results indicated that the accumulation of Cd in sediments was obvious, with approximately 61.9% of the samples showing moderate to high accumulation levels, followed by Pb, Cu, Ni, and Zn, whereas the As and Cr were at low levels. A large proportion of BCR-extracted acid extractable and reducible fraction were found in Cd (72.5%) and Pb (40.3%), suggesting high bioavailability. The combined results of RSP, RAC, and MRI showed that Cd was the major pollutant in sediments with high potential ecological risk, while the risk of other elements was low. Source apportionment results of heavy metal(loid)s indicated that Cd (75.76%) and Zn (23.1%) mainly originated from agricultural activities; As (69.82%), Cr (50.05%), Cu (33.47%), and Ni (31.87%) were associated with domestic sources related to residents' lives; Cu (52.36%), Ni (44.57%), Cr (34.33%), As (26.51%), Pb (24.77%), and Zn (23.80%) primarily came from natural geological sources; and Pb (47.56%), Zn (22.46%) and Cr (13.92%) might be introduced by mixed sources of traffic and domestic. The contribution ratios of the four sources were 18.41%, 36.67%, 29.48%, and 15.44%, respectively. Overall, priority control factors for pollution in relation to agricultural sources included Cd, while domestic sources are primarily associated with As. It is crucial to place special emphasis on the impacts of human activities when formulating pollution prevention and control measures. The results of this study can provide valuable reference and insights for water resources management and pollution prevention and control strategies in karst mountainous areas.

Anomalous concentrations of rare earth elements in acid mine drainage and implications for rare earth resources from late Permian coal seams in northern Guizhou.

Rare earth elements (REEs) have attracted much attention in recent decades due to their growing applications in high-tech industries. Coal and acid mine drainage (AMD) are considered promising alternative sources due to their high concentrations of REEs. Here, AMD with anomalous REEs concentrations was reported in a coal-mine area in northern Guizhou, China. The AMD had a total concentration as high as 22.3 mg/l, suggesting that regional coal seams may be enriched with REEs. Five segments from borehole samples, which contained coal, rocks from the roof and floor of the coal seam were collected from the coal mine site to investigate the abundance, enrichment, and occurrence of REE-bearing minerals. Elemental analysis showed that the REE contents in the coal, mudstone and limestone from the coal seam roof, and claystone from the floor (all dating to the late Permian) varied greatly, with averages of 388, 549, 60.1 mg/kg and 2030 mg/kg, respectively. Encouragingly, the REEs content in the claystone is over an order of magnitude higher than the average content reported in most other coal-based materials. The enrichment of REEs resources in regional coal seams is particularly associated with the contribution of REEs in the claystone that comprises the coal seam floor, rather than just the coal, as considered in previous studies. The minerals in these claystone samples were dominated by kaolinite, pyrite, quartz and anatase. Two types of REE-bearing minerals, bastnaesite and monazite, were detected in the claystone samples by SEM-EDS analysis, and they were found to be adsorbed by a large amount of clay minerals, mainly kaolinite. Additionally, the results of chemical sequential extraction also confirmed that the majority of the REEs in the claystone samples are mainly in their ion-exchangeable, metal oxide and acid-soluble forms, which are viable prospects for REE extraction. Therefore, the anomalous concentrations of REEs and most of them are in extractable phases, which demonstrates that the claystone from the floor of the late Permian coal seam should be a potential secondary source of REEs. Future studies will further consider the extraction model and the economic benefits of REEs from the floor claystone samples.

Distribution, Risk Assessment, and Source Apportionment of Heavy Metal Pollution in Cultivated Soil of a Typical Mining Area in Southwest China.

The present study investigates heavy metal pollution and its sources in cultivated soils in Bijie City, Guizhou Province, China. The ground accumulation index method was used to evaluate the associated risks, while correlation, principal component, and positive matrix factor model analyses were used to identify sources. The results show that the overall contamination levels, except for Cd, were not serious. Agricultural materials, industrial activities, transportation, coal combustion and atmospheric deposition, parent rock, and irrigation accounted for 19.66%, 14.11%, 14.54%, 16.33%, 20.70%, and 14.67% of the total accumulation of metals, respectively. Copper, Ni, Zn, and Cr came mainly from parent rocks; Pb was mainly from traffic emissions; Hg was mainly from coal deposition; As was mainly from irrigation; and Cd was mainly from industrial activities. The main sources of soil metals were irrigation, agricultural activities, and coal deposition in the east and industrial activities and soil-forming parent rocks in the west. Environ Toxicol Chem 2023;42:888-900. © 2023 SETAC.

Distribution characteristics and potential pollution assessment of heavy metals (Cd, Pb, Zn) in reservoir sediments from a historical artisanal zinc smelting area in Southwest China.

Reservoir sediment contamination with heavy metals produced by mining activities has aroused widespread global concern owing to its potential threat to human health. In this study, the total concentrations and speciation of heavy metals (Cd, Pb, Zn) in the Lexi (LX) and Maoshui (MS) reservoirs around the historical artisanal zinc smelting area in Southwest China were determined, and pollution indices were applied to assess the pollution levels and potential ecological risks of the two reservoirs. The results showed that all the detected samples in the two reservoirs presented significant metal accumulation, especially for Cd, as compared with the soil background values in Guizhou Province. Between the two reservoirs, the vertical distribution characteristics of each metal in sediment columns were similar. The heavy metal concentrations of the three columns in the LX reservoir reached their maxima at 35, 15, and 10 cm and showed a trend of first increasing and then decreasing overall. However, the heavy metal contents of the three columns in the MS reservoir all exhibited wave-like characteristics in the vertical direction, and all of them reached a relatively obvious high point at approximately 5 and 30 cm. The geoaccumulation index (Igeo) and potential ecological risk index (RI) indicated that Cd was strongly enriched and represented the main risk factor, and the pollution level of the MS reservoir was significantly higher than that of the LX reservoir. Furthermore, the effect coefficients (ERMQ) confirmed that the two reservoirs are likely to have toxic impacts on aquatic organisms and need to be controlled and mitigated. The speciation analysis of heavy metals revealed that Cd was primarily in the acid-extractable fraction (69.57%, 68.28%), Pb was chiefly in the reducible fraction (55.24%, 42.18%) and oxidizable fraction (22.60%, 38.02%), and Zn was mainly in the oxidizable fraction (32.54%, 37.65%) in the LX and MS reservoirs, respectively. The ratios of the secondary phase and primary phase (RSP) and risk assessment code (RAC) evaluation demonstrated that Cd in the sediments of the two reservoirs presents a very high potential ecological risk, and Pb and Zn were at medium to high ecological risk levels. This study highlighted that the artisanal zinc smelting activities had caused serious heavy metal pollution in reservoir sediments, posing a threat to the local ecological environment.

Hydrogeochemical Characteristics and Quality Assessment of Mine Water in Coalfield Area, Guizhou Province, Southwest China.

Coal resources are widely distributed in Guizhou province, China and environmental pollution caused by coal mining is becoming increasingly serious, especially mine drainage. A total of 120 mine water samples collected from different coalfields were analyzed to investigate the hydrogeochemical characteristics and assess the water quality for drinking, domestic, and irrigative purposes. Water samples had a pH of 1.90-9.12 and most of them were acidic or weakly acidic. Total dissolved solids (TDS) ranged from 254 to 13,944 mg/L and correlated closely with the electrical conductivity (EC). The coal mine drainage of Guizhou was characterized typically by low pH value, high Fe and SO42- concentration, which were mainly attributed to oxidative weathering of pyrite. The most dominant type for abandoned coal-mine drainage was Ca-Mg-SO4, while that of the underground drainage for active mine were mainly Na-SO4 and Na-HCO3 because of high concentration of Na+ from the dissolution of evaporites and clastic rocks. High concentration of the TDS, SO42-, Fe, Mn, et al. made it unsuitable for drinking and domestic use, but part of the coal mine drainage could be used for irrigation at some sites.