Potentially toxic elements in soil-plant-water-animal continuum in a mining area from Northwestern Mexico: animal exposure pathways and health risks for children.

Mining increases environmental concentrations of potentially toxic elements (PTEs) accumulating in organisms and spreading in the human food chain-their presence in milk is of great human health concern. Pathways were identified by which these elements reach raw milk from farms within a mining area in Northwestern Mexico; health risks for dairy cattle and children were also evaluated. Water from river and cattle waterers, as well as, soils showed that PTE concentrations generally below the Mexican and international limits; cattle forage concentrations were above the World Health Organization limits. Al, Mg, Mo, Ni and Zn were recorded in raw milk samples from the mining area, showing that Cd, Co, Cr, Cu, Pb and V are transferred from soil to plants but not accumulated in raw milk. Zn concentrations in raw milk exceeded the permissible limit; milk from farms without mining operations (comparison site) showed the presence of Al, Cr and Cu. In cattle tail hair, PTE did not correlate with raw milk concentrations. Metal accumulation in milk was higher through water consumption than that accumulated through forage consumption. Daily intakes (DI) of Al, Mg and Zn in cows could represent a risk for their health. The observed biotransference was higher than in other parts of Mexico, and the calculated DI and hazard quotients indicate no adverse health effects for children. However, the hazard Index values indicate that exposure to multiple PTE represents a risk for children. Management measures should be performed to control the cumulative risks to protect young children's health.

Water resources affected by potentially toxic elements in an area under current and historical mining in northwestern Mexico.

Rio Sonora watershed and its aquifer-located in northwest Mexico-have been influenced by mining operations for 140 years, possibly causing emissions of potentially toxic elements (PTE) and affecting health of exposed populations. On the basis of available data from governmental surveys (2014-2017) and recent sampling (2018), this study constructed reliable PTE total concentration database that allowed us to report temporal/spatial variations in surface and groundwater and their associated health risks to the population living in the central part of the Rio Sonora basin. The data clearly showed that a mining spill that took place in 2014 has had an adverse impact on total PTE concentrations in surface water. They also indicated the presence of different PTE point source locations that have continued to cause contamination of surface water at levels of health concern. Data also suggested slight impacts of the spill event on groundwater possibly related to soil neutralizing potential. Two metal groups were detected for surface waters (Pb-Cd-As-Ni-Cr and of Zn-Al-Cr) and groundwaters (Cr-As-Cu-Cd and Zn-Al), which suggest that they have different sources or are being released by different processes. The potential health impacts of PTE concentrations were associated with specific age groups, dates, and areas. The results indicate that in this complex semi-arid rural system, current and historical mining activities, as well as contrasting hydrological conditions, have impacted surface and groundwater quality with important ecological and human health risks.

Mobility of 4-nonylphenol and di(2-ethylhexyl) phthalate in three agricultural soils irrigated with untreated wastewater.

Agricultural irrigation using raw wastewater is a popular practice in developing countries. However, as endocrine disrupting chemicals have been found in this water, the potential pollution of soil and water sources has become a source of concern. Such pollutants may be removed during the passage of wastewater through the soil by degradation and/or sorption. In this study the sorption and mobility of bis-2-ethyl(hexyl)phthalate (DEHP) and 4-nonylphenol (4-NP) in three different soils (Leptosol, Phaeozem and Vertisol) was compared. The distribution coefficients showed that DEHP is rapidly sorbed onto the three tested soils (K(d) between 1.8 × 10(4) and 4.2 × 0(4) L/kg), while sorption of 4-NP (K(d) between 15 and 80 L/kg) was weaker. In batch experiments the soil sorption capacity observed was as follows: Vertisol > Phaeozem > Leptosol for both compounds. However, in column experiments the retardation factor (R(F)) for 4-NP was higher than for the DEHP in the three soils. This suggests the possible migration of DEHP through the soil via colloids. The column results were found consistent with those observed in the field. It was concluded that the risk of groundwater contamination is higher for Leptosol soil than for Phaeozem and Vertisol soils and that DEHP can reach the aquifer prior to 4-NP.

Sorption and desorption of carbamazepine, naproxen and triclosan in a soil irrigated with raw wastewater: estimation of the sorption parameters by considering the initial mass of the compounds in the soil.

In conventional sorption studies, the prior presence of contaminants in the soil is not considered when estimating the sorption parameters because this is only a transient state. However, this parameter should be considered in order to avoid the under/overestimation of the soil sorption capacity. In this study, the sorption of naproxen, carbamazepine and triclosan was determined in a wastewater irrigated soil, considering the initial mass of the compounds. Batch sorption-desorption tests were carried out at two soil depths (0-10 cm and 30-40 cm), using either 10 mM CaCl(2) solution or untreated wastewater as the liquid phase. Data were satisfactorily fitted to the initial mass model. For the two soils, release of naproxen and carbamazepine was observed when the CaCl(2) solution was used, but not in the soil/wastewater system. The compounds' release was higher in the topsoil than in the 30-40 cm soil. Sorption coefficients (K(d)) for CaCl(2) solution tests showed that in the topsoil, triclosan (64.9 L kg(-1)) is sorbed to a higher extent than carbamazepine and naproxen (5.81 and 2.39 L kg(-1), respectively). In the 30-40 cm soil, carbamazepine and naproxen K(d) values (11.4 and 4.41 L kg(-1), respectively) were higher than those obtained for the topsoil, while the triclosan K(d) value was significantly lower than in the topsoil (19.2 L kg(-1)). Differences in K(d) values were found when comparing the results obtained for the two liquid phases. Sorption of naproxen and carbamazepine was reversible for both soils, while sorption of triclosan was found to be irreversible. This study shows the sorption behavior of three pharmaceuticals in a wastewater irrigated soil, as well as the importance of considering the initial mass of target pollutants in the estimation of their sorption parameters.

Transporte de Atrazina en un Andosol y un Vertisol de México / Atrazine Transport in a Mexican Andosol and Vertisol / Transporte de Atrazina em um Andosol e um Vertisol de México

El problema de migración de plaguicidas en los campos agrícolas se estudia tradicionalmente a través del muestreo periódico de suelos, aguas y cultivos. Existen métodos más avanzados que permiten reducir el costo de los análisis en campo y pronosticar el riesgo de contaminación del medio ambiente. Estos métodos están basados en la simulación matemática del movimiento de plaguicidas. Se estudió el proceso de migración de atrazina en un suelo volcánico Andosol y un Vertisol de México en experimentos de laboratorio en columnas empacadas. En los experimentos se aplicaron diferentes dosis de atrazina y se estableció un flujo insaturado de agua bajo régimen permanente. Se utilizaron los marcadores del agua 18O y Br- para comparar los procesos de movimiento del agua y la atrazina. Se midieron los componentes del balance de masa de atrazina y agua, y su dinámica de elusión. Se aplicó la teoría del movimiento de sustancias químicas para interpretar los resultados experimentales y obtener las propiedades principales de transporte de atrazina en ambos suelos. Los resultados señalan que la atrazina se mueve en el Andosol 10-16 veces más lentamente que el agua y en el Vertisol el movimiento es 2,5 veces más lento. Se determinaron valores de cinco propiedades de transporte de atrazina que permiten predecir la migración del plaguicida, minimizar el muestreo en el campo y estimar el riesgo de contaminación del suelo y del acuífero aplicando los métodos de cálculo existentes en la literatura.

The problem of pesticide migration in agricultural lands is traditionally studied by means of periodical soil, water and plant sampling. More advanced methods are available today, which permit to reduce the costs of field analysis and to predict environmental contamination risk. These methods are based on mathematical simulation of pesticide movement. The process of atrazine migration in a volcanic soil Andosol and a Vertisol of Mexico was studied by means of laboratory experiments in packed columns. Different atrazine doses and steady state unsaturated water flow were applied in the experiments. The 18O and Br- water tracers were used to compare atrazine and water movement. The atrazine and water mass balance components were measured, as well as the dynamics of elution. The chemical substances movement theory was applied to interpret the experimental results and to obtain the principal properties of atrazine transport in both soils. The results show that atrazine moves in the Andosol 10-16 times slower than water, and 2.5 times slower in the Vertisol. Five properties of atrazine transport were determined, which can be used to predict the migration of this pesticide so as to minimize the sampling effort in the field, and to assess the risk of soil and aquifer contamination by calculation methods reported in the literature.

O problema de migração de praguicidas em áreas agrícolas se estuda tradicionalmente através da amostragem periódica de solos, aguas e cultivos. Existem métodos mais avançados que permitem reducir o custo das análises em campo e prever o risco de contaminação do meio ambiente. Estes métodos estão baseados em simulação matemática do movimento de praguicidas. Estudou-se o processo de migração de atrazina em um solo vulcánico Andosol e um Vertisol do México em experimentos de laboratório em colunas empacotadas. Nos experimentos se aplicaram diferentes doses de atrazina e se estabeleceu um fluxo insaturado de água sob regime permanente. Utilizaram-se os marcadores da água 18O e Br‾ para comparar os processos de movimento da água e a atrazina. Mediram-se os componentes do balanço de massa de atrazina e água, e sua dinâmica de eluição. Aplicou-se a teoria do movimento de substâncias químicas para interpretar os resultados experimentais e obter as propiedades principais de transporte de atrazina em ambos os solos. Os resultados indicam que a atrazina se movimenta no Andosol 10-16 veces mais lentamente que a água e no Vertisol o movimento é 2,5 vezes mais lento. Determinaram-se valores de cinco propriedades de transporte de atrazina que permitem predizer a migração do praguicida, minimizar a amostragem no campo e estimar o risco de contaminação do solo e do aquífero aplicando os métodos de cálculo existentes na literatura.