RESUMEN
The successful use of visible and near-infrared (Vis-NIR) reflectance spectroscopy analysis requires selecting an optimal procedure of data acquisition and an accurate modeling approach. In this study, Vis-NIR with 350-2500 nm wavelengths were applied to detect different forms of lead (Pb) through the spectrally active soil constituents combining principal component regression (PCR) and Partial least-square regression (PLSR) for the Vis-NIR model calibration. Three clouds with different soil spectral properties were divided by the Linear discriminant analysis (LDA) in categories of Pb contamination risks: "low," "health," "ecological," ranging from 200 to 750 mg kg-1. Farm soils were used for calibration (n = 26), and more polluted garden soils (n = 36) from New York City were used for validation. Total and bioaccessible Pb concentrations were examined with PLSR models and compared with Support Vector Machine (SVM) Regression and Boosting Regression Tree (BRT) models. Performances of all models' predictions were qualitatively evaluated by the Root Mean Square Error (RMSE), Residual Prediction Deviation (RPD), and coefficient of determination (R2). For total Pb, the best predictive models were obtained with BRT (R2 = 0.82 and RMSE 341.80 mg kg-1) followed by SVM (validation, R2 = 0.77 and RMSE 337.96 mg kg-1), and lastly by PLSR (validation, R2 = 0.74 and RMSE 499.04 mg kg-1). The PLSR technique is the most accurate calibration model for bioaccessible Pb with an R2 value of 0.91 and RMSE of 68.27 mg kg-1. The regression analysis indicated that bioaccessible Pb is strongly influenced by organic content, and to a lesser extent, by Fe concentrations. Although PLSR obtained lower accuracy, the model selected many characteristic bands and, thus, provided accurate approach for Pb pollution monitoring.
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Plomo , Suelo , Contaminación Ambiental , Análisis de los Mínimos Cuadrados , Espectroscopía Infrarroja CortaRESUMEN
In the small city of St. John's, NL (2020 population ~114,000), 100% of the soils of the pre-1926 properties exceeded the Canadian soil Pb standard, 140 mg/kg. The Pb was traced to high-Pb coal ash used for heating and disposed on the soils outside. Analytical instruments became available in the late 1960s and 1970s and were first used for blood Pb and clinical studies and repurposed for measuring environmental Pb. The environmental research part of this study compared four common soil Pb analysis methods on the same set (N = 96) of St. John's soil samples. The methods: The US EPA method 3050B, portable X-ray fluorescence spectrometry (pXRF), The Chaney-Mielke leachate extraction (1 M nitric acid), and the relative bioaccessibility leaching procedure (US EPA method 1340). Correlation is not the same as agreement â. There is strong agreement (Berry-Mielke's Universal â) among the four soil Pb analytical methods. Accordingly, precaution is normally advisable to protect children from the high-Pb garden soils and play areas. A public health reality check by Health Canada surveillance of St. John's children (N = 257) noted remarkably low blood Pb. The low blood Pb of St. John's' children is contrary to the soil Pb results. Known urban processes causing the rise of environmental Pb and children's Pb exposure includes particle size, aerosol emission by traffic congestion, and quantities of leaded petrol during the 20th century. Smaller cities had minor traffic congestion and limited combustion particles from leaded petrol. From the perspective of the 20th century era of urban Pb pollution, St. John's, NL, children have blood Pb characteristics of a small city.
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Contaminantes del Suelo , Suelo , Canadá , Niño , Ciudades , Humanos , Plomo , Terranova y Labrador , Contaminantes del Suelo/análisisRESUMEN
Several studies have reported the presence of smithsonite (ZnCO3 ) in soils polluted by zinc mining. The present study aimed to determine upper critical threshold values of Zn phytotoxicity in a substrate spiked with ZnCO3 and to compare them with those obtained in field-collected soils. We studied Zn toxicity to perennial ryegrass (Lolium perenne L.) grown in pots with unpolluted peat treated with increasing concentrations of ZnCO3 that produced nominal total Zn concentrations of 0, 0.7, 1.3, 2.0, 2.6, and 3.3%. To keep constant near-neutral pH value in all the treatments, we used decreasing concentrations of dolomitic lime. In the treatment with total soil Zn of 3.3% (pH 6.8), the foliar Zn concentration of L. perenne was 1914 ± 211 mg kg-1 , falling into the range of 2400 ± 300 mg kg-1 reported for Lolium species grown under similar laboratory conditions in a polluted soil (total soil Zn 5.4%, pH 7.3) collected near a Zn smelter. The value of 92 ± 98 mg kg-1 was obtained for the median effective concentration (EC50) values of 0.01 M KNO3 -extractable Zn using the responses of shoot dry biomass, shoot length, and total pigments. This value falls within the range of 95 ± 46 mg kg-1 reported in other studies for the EC50 values of salt-extractable Zn using field-collected soils. The application of ZnCO3 for spiking was able to mimic foliar Zn concentrations of Lolium species observed in field-collected soils. The effective concentrations of soil Zn obtained in the present study are comparable to those obtained in field-collected soils. Future research should determine effective concentrations of metals using soils spiked with metal-containing compounds that mimic a real source of contamination. Environ Toxicol Chem 2020;39:1790-1796. © 2020 SETAC.
Asunto(s)
Carbonatos/toxicidad , Lolium/efectos de los fármacos , Suelo/química , Compuestos de Zinc/toxicidad , Biomasa , Lolium/crecimiento & desarrollo , Minería , Brotes de la Planta/anatomía & histología , Brotes de la Planta/efectos de los fármacos , Contaminantes del Suelo/toxicidad , Zinc/análisisRESUMEN
Urban gardening is popular in many cities. However, many urban soils are contaminated and pose risks to human health. This study was conducted in a highly publicized urban garden in Brooklyn, NY with elevated Pb and As levels. Our objectives were to: (1) assess the nature and extent of Pb and As contamination at this site; (2) evaluate the effectiveness of amendments on reducing the bioaccessibility and phytoavailability of Pb and As in soil; and (3) assess the potential exposure of children to Pb and As through direct and indirect exposure pathways. Field surveys of the site revealed that contamination was highly concentrated in one area of the garden associated with fruit tree production. Field plots were established in this area, with three different treatments (bone meal, compost, sulfur) and an unamended control. Bioaccessibility of Pb was significantly reduced by all three treatments compared to the control (33%): bone meal (24%), compost (23%), sulfur (24%). In this study, As bioaccessibility remained high (80-93%) with or without treatments. We found that the effectiveness of soil remediation with amendments is variable and often limited, and contaminated sites can still pose a significant risk to urban gardeners. The results of a simple assessment model suggested that Pb and As exposure was mostly from soil and dust ingestion, rather than vegetable consumption. This work is unique in that it evaluates actual elevated levels of contamination, in actively gardened urban soils, in a highly visible public context. It fills important gaps between basic research and analysis of human exposure to toxic trace metals that can be a constraint on a highly beneficial activity.
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Suelo , Niño , Ciudades , Jardinería , Jardines , Humanos , Contaminantes del SueloRESUMEN
The townships of Puchuncaví and Quintero, on the coast of central Chile, have soils contaminated by atmospheric deposition of sulfur dioxide and trace elements from the nearby Ventanas Industrial Complex. The purpose of this study was to evaluate potential human health and ecological risks, by determining the spatial distribution of soil total concentrations arsenic (As), copper (Cu), lead (Pb), and zinc (Zn) in these townships. Total concentrations of these elements were determined in 245 topsoil samples, used to generate continuous distribution maps. The background concentrations of Cu, As, Pb, and Zn in the studied soils were 100, 16, 35, and 122â¯mgâ¯kg-1, respectively. The concentrations of Cu, As, and Pb were positively correlated with each other, suggesting that their source is the Ventanas copper smelter. On the other hand, correlations for Zn were weaker than for other trace elements, suggesting low impact of the Ventanas copper smelter on spatial distribution of Zn. Indeed, only 6% of the study area exhibited Zn concentrations above the background level. In contrast, 77, 32 and 35% of the study area presented Cu, As, and Pb concentrations, respectively, above the background level. The carcinogenic risk due to exposure to As was above the threshold value of 10-04 in the population of young children (1-5 years old) on 27% of the study area. These risk values are classified as unacceptable, which require specific intervention by the Chilean government. Based on the estimated concentrations of exchangeable Cu, 10, 15, and 75% of the study area exhibited high, medium, and low phytotoxicity risk, respectively.