Assessment of heavy metal status and identification of source in soils under intensive vegetable growing areas of Brahmaputra valley, North East India

Copper and chromium removal from industrial sludge by a biosurfactant-based washing agent and subsequent recovery by iron oxide nanoparticles

Industrial wastewater treatment generates sludge with high concentrations of metals and coagulants, which can cause environmental problems. This study developed a sequential sludge washing and metal recovery process for industrial sludge containing > 4500 mg/kg Cu and > 5000 mg/kg Cr. The washing agent was formulated by mixing glycolipid, lipopeptide, and phospholipid biosurfactants from Weissella cibaria PN3 and Brevibacterium casei NK8 with a chelating agent, ethylenediaminetetraacetic acid (EDTA). These biosurfactants contained various functional groups for capturing metals. The optimized formulation by the central composite design had low surface tension and contained relatively small micelles. Comparable Cu and Cr removal efficiencies of 37.8% and 38.4%, respectively, were obtained after washing the sludge by shaking with a sonication process at a 1:4 solid-to-liquid ratio. The zeta potential analysis indicated the bonding of metal ions on the surface of biosurfactant micelles. When 100 g/L iron oxide nanoparticles were applied to the washing agent without pH adjustment, 83% Cu and 100% Cr were recovered. In addition, X-ray diffraction and X-ray absorption spectroscopy of the nanoparticles showed the oxidation of nanoparticles, the reduction of Cr(V) to the less toxic Cr(III), and the absorption of Cu. The recovered metals could be further recycled, which will be beneficial for the circular economy.

Identifying contamination of heavy metals in soils of Peruvian Amazon plain: use of multivariate statistical techniques

The Peruvian Amazon plain has abundant natural resources and is home to great biodiversity, which makes it an area with high economic potential. However, the use of its resources through various activities has contributed to the release of heavy metals (HMs) into its soils, generating severe pollution problems which have mainly affected the health of local populations and their ecosystems. Currently, there are no comprehensive studies that have identified the specific sources of contamination by HMs in the soils of this part of the Peruvian territory. In this sense, this research aims to identify the possible sources of contamination by HMs in the soils of the Peruvian Amazon plain to focus efforts on the establishment of adequate measures for the protection of the health of people and the ecosystem. In the present study, samples of topsoils (0-20 cm depth) and subsoils (100-150 cm depth) were collected for the analysis of 11 HMs (Co, Cr, Cu, Fe, Mn, Ni, Pb, V, Zn, Be, and Hg) in 48 sites located in four regions of the Peruvian Amazon plain (Loreto, Amazonas, San Martín, and Ucayali), over the year 2019. The enrichment factor and geoaccumulation index were applied to assess contamination levels of HMs. The results indicated that topsoils and subsoils presented a greater enrichment by the elements Be and Pb, and were classified as moderately contaminated. Likewise, the integral analysis of these indexes together with principal component analysis, hierarchical cluster analysis, correlation analysis, and coefficient of variation allowed the identification of potential sources of contamination by HMs. As a result, Fe, Co, Zn, Ni, V, and Cr were associated with natural or lithogenic sources (parent material, crude oil deposits, and organic matter decomposition). Hg was attributed to anthropogenic sources (illegal gold mining, atmospheric deposition, and vehicle emissions). Be, Pb, Cu, and Mn originated from natural sources (parent material, crude oil deposits, decomposition of organic matter, and forest fires) and anthropogenic (areas degraded by solid waste, illegal gold mining, agriculture, and hydrocarbons). These findings provide essential information to establish regulations and prevent and control HM contamination in soils of the Peruvian Amazon plain.

Quantification of heavy metals and health risk assessment in Sichuan pickle

Sichuan pickle is one of popular traditional fermented foods in China. However, the contamination of heavy metals in Sichuan pickle, particularly home-made Sichuan pickle and aged pickle brine, is little known. Therefore, the content of trace (Cr, Cu, and Zn) and toxic elements (As, Pb, and Cd) in Sichuan industrial pickle (SIP), Sichuan home-made pickle (SHP), and aged pickle brine collected from local markets and families in Sichuan province, respectively, was detected by inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS) and the health risk was assessed by target hazard quotients including target hazard quotient (THQ) and total target hazard quotient (TTHQ). Consequently, the mean concentrations of Cr, Cu, Zn, As, Pb, and Cd were 0.122, 0.540, 2.516, 0.023, 0.015, and 0.106 mg/kg in SIP and 0.071, 0.364, 2.698, 0.014, 0.015, and 0.289 mg/kg in SHP, respectively, lower than the maximum allowable concentrations set by Chinese regulations, except for Cr and Cd in few samples. Principal component analysis of the heavy metal content could obviously distinguish between SIP and SHP. The content of As, Pb, and Cd in leaf pickles was significantly higher than that in pickles fermented with other types of vegetables. A significant enrichment of heavy metals in aged pickle brine over 10 years was observed, but pickle jars had no significant effect on heavy metal content in aged pickle brine. The intake of heavy metals through daily consumption of SIP and SHP was at a safe level, whereas the TTHQ of leaf pickle was 1.006, indicating a potential health risk. In conclusion, this study provided fundamental data for food safety assurance of Sichuan pickle. PRACTICAL APPLICATION: Sichuan pickle is one of popular traditional fermented foods in China. In the present study, we investigated the contamination of heavy metals in Sichuan pickles by detecting the content of Cr, Cu, Zn, As, Cd, and Pb in Sichuan industrial pickle, Sichuan home-made pickle, and aged pickle brine, and estimated the health risk to local residents. This study can provide a reference for the safety risk of Sichuan industrial and home-made pickle in terms of heavy metal contamination, and enhance the food safety in the processing, production, and consumption of Sichuan pickle in local families and pickle industry.