A pilot-scale electrocoagulation-treatment wetland system for the treatment of landfill leachate.

In the present study, the technical feasibility of an electrocoagulation-treatment wetland continuous flow system, for the removal of organic matter from landfill leachate (LL), was evaluated. The response surface methodology (MSR) was used to assess the individual and combined effects of the applied potential and distance between electrodes, on the removal efficiency and optimization of the electrocoagulation process. The hybrid treatment wetland system consisted of a vertical flow system coupled to a horizontal subsurface flow system, both planted with Canna indica. For a chemical oxygen demand (COD) concentration - without pretreatment of 5142.8 ± 2.5 mg L-1, the removal percentage for the electrocoagulation system was 79.4 ± 0.16%, under the optimal working conditions (Potential: 20 V; Distance: 2.0 cm). The COD removal efficiency in the treatment wetland with Canna indica showed a dependence with the hydraulic retention time, reaching 59.2 ± 0.2 % over 15 days. The overall efficiency of the system was about 91.5 ± 0.02 % removal of COD. In addition, a decrease in the biochemical oxygen demand (94.8 ± 0.14%) and total suspended solids (88.2 ± 0.22%), also related to the contamination levels of the LL, were obtained. This study, for the first time, shows that the coupling of electrocoagulation together with a treatment wetland system is a good alternative for the removal of organic contaminants present in LL.

Vertical distribution and trace element contamination in sediment cores affected by gold mining in Colombia.

The vertical distribution, level of contamination, potential ecological risks, and historical fluxes of trace elements (Pb, As, and Hg) were evaluated from 210Pb-dated sediment cores in three different areas with gold mining impacts in northern Colombia: the Atrato River (AR), the Delicias Marsh (DM) and the Encaramada Marsh (EM). All cores spanned ∼100 years; the mass accumulation rates followed the order AR > DM > EM. The average trace elements concentrations in the sediment cores were: Pb 2.41 ± 0.72, As 0.65 ± 0.32, Hg 0.07 ± 0.02 µg g-1 in the Atrato River; Pb 23.49 ± 2.59, As 2.46 ± 0.88, Hg 0.10 ± 0.02 µg g-1 in the Delicias Marsh; and Pb 9.76 ± 4.18, As 2.44 ± 1.26, Hg 0.17 ± 0.06 µg g-1 in the Encaramada Marsh. Sediments are classified according to the contamination factor (CF) and geoaccumulation index (Igeo) as low to very highly contaminated. The Pollution load index (PLI) indicates environmental deterioration (PLI> 1), and the Sediment quality guidelines (SQGs) indicate that only Hg may produce adverse biological effects in the EM core. This study is an example of the reconstruction of temporal changes in pollution levels and impacts of potentially toxic elements caused by gold mining in remote ecosystems, which can be reproduced in other areas where environmental monitoring is scarce or non-existent.

Health risk assessment for human exposure to mercury species and arsenic via consumption of local food in a gold mining area in Colombia.

The risk to human health from exposure to certain pollutants through the consumption of fruits, tubers, and fish were evaluated in a settlement located in a Colombian area highly impacted by gold mining activities. The concentrations of mercury (Hg) and arsenic (As) in edible food tissues and methylmercury (MeHg) in fish were determined for risk assessment. A questionnaire-based dietary survey was answered by 178 residents of three population groups: children (CHD), women of childbearing age (WCBA), and the rest of the population (RP). The estimated weekly intake (EWI) of MeHg presented values of 1.9 and 2.4 times higher than the provisional tolerable weekly intake (1.6 µg/kg BW/week) recommended by the FAO/WHO for CH and WCBA, respectively. The results of the HQ values of As and Hg for different food were above the safety level (HQ < 1) for most of the groups. For Hg, the highest HQ values correspond to fish, whereas for As in most of the food, but specially in fruits. The total target hazard quotients (HI) were higher than 1, in all the groups (except for CHD that consume tubers) indicating potential non-carcinogenic health risks. The values of carcinogenic risk (CR) for As through exposure to food ranged from 1.2·10-4 to 7.7·10-4, well above than the safety level of US EPA risk (10-4-10-6), suggesting the probability of carcinogenic risk for the entire population via ingestion. Therefore, safety control mechanisms and environmental education strategies should be applied to address food intake, associated with good agricultural practices to provide solutions to protect the health of the residents in areas affected by gold mining activities.

Evaluación de calidad del agua en la Quebrada Jui, afluente del río Sinú, Colombia / Water quality assessment in Quebrada Jui, tributary of the Sinú river, Colombia

RESUMEN La microcuenca de la quebrada Jui, enmarcada dentro de la cuenca alta del río Sinú, región Caribe de Colombia, es uno de los recursos hídricos utilizados por la población rural para consumo, riego y saneamiento; sin embargo, recibe cargas contaminadas de centros poblados en su área de influencia, que corresponden al vertimiento de aguas residuales, afluentes de laguna de oxidación, actividades ganaderas, extracción de arena, agricultura de pancoger y cultivos no formales. El objetivo de este estudio fue determinar el índice de calidad del agua (ICA) y establecer la relación entre los parámetros fisicoquímicos y microbiológicos con las diferentes fuentes antropogénicas, para establecer origen común de contaminación. Además, el análisis de plaguicidas organoclorados y organofosforados, para conocer la influencia de las actividades agrícolas. Se tomaron muestras en seis estaciones, en el periodo seco y húmedo del 2018. Las concentraciones de los parámetros fisicoquímicos y microbiológicos, se analizaron empleando los métodos estandarizados de la American Public Health Association. Los plaguicidas, se cuantificaron por el método cromatografía de gases con espectrometría de masas (GC-MS). En promedio, el ICA fue 74,1, clasificando la fuente hídrica con buena calidad, exceptuando las estaciones (E4 y E5), en el periodo húmedo, cuya clasificación fue media, debido al aporte de coliformes fecales y turbidez. La concentración de plaguicidas, se presentó por debajo del límite de detección del método. En general, el análisis estadístico multivariado indica que las fuentes de contaminación derivan de aguas residuales domésticas, escorrentía agrícola, excretas del ganado porcino y minería de arena.

ABSTRACT The micro-base of the Jui creek, framed within the upper Sinú River basin, Colombia Caribbean region, is one of the water resources used by the rural population for consumption, irrigation and sanitation. However, it receives contaminated loads from urban centers in its area of influence that correspond to the discharge wastewater, oxidation lagoon tributaries, livestock activities, sand extraction, agriculture and non-formal crops. The objective of this study was to determine the water quality index (ICA) and establish the relationship between the physical-chemical and microbiological parameters with the different anthropogenic sources to establish a common source of contamination. In addition, the analysis of organochlorinated and organophosphate pesticides to understand the influence of agricultural activities. Samples were taken in six seasons, in the dry and humid period of 2018. Concentrations of physical-chemical and microbiological parameters were analyzed using the American Public Health Association's standardized methods. The pesticides were quantified by the gas chromatography method with mass spectrometry (GC-MS). On average the WQI was 74.1 classifying the water source with good quality, except the seasons (E4 and E5) in the wet period, the classification of which was average, due to the contribution of fecal coliforms and turbidity. The concentration of pesticides was below the detection limit of the method. In general, multivariate statistical analysis indicates that sources of pollution are from domestic wastewater, agricultural runoff, pig excretions and sand mining.

Concentraciones de mercurio en atún comercializado en Montería, Colombia: evaluación del riesgo en la salud / Mercury concentrations in tuna commercialized in Montería, Colombia: evaluation of health risk

RESUMEN Objetivo El objetivo de este trabajo fue determinar la concentración de mercurio total (HgT) y metilmercurio (MeHg) en atún enlatado que se distribuye en la ciudad de Montería (Córdoba, Colombia). Materiales y Métodos Se analizaron 160 muestras de cuatro marcas diferentes, identificadas como A, B, C y D y comercializadas de agosto a noviembre de 2017. Mensual-mente se realizó un muestreo simple por atributo. El HgT y el MeHg fueron determinados usando un equipo DMA-80 (marca Milestone) y cromatógrafo de gases (Perkin Elmer Autosystem XL). Resultados El promedio de HgT y MeHg fue 0,589 ± 0,163 y 0,536 ± 0,148 ug/g, respectivamente. La mayor concentración de HgT y MeHg en atún se presentó en la marca B (HgT: 0,792 ± 0,165; MeHg: 0,725 ± 0,127). Conclusiones La evaluación del riesgo a la salud debido al consumo de atún enlatado, basado en la ingesta semanal estimada (ESI), sugiere que el consumo de atún de las diferentes marcas no asocia posibilidad de riesgo en la salud al grupo de adultos de la población (APG), al presentar valores por debajo de la ingesta semanal tolerable (3,2 μg/ kg/semana). Mientras que para los grupos de niños (N) y mujeres en edad fértil (MEF) representa riesgo para la salud el consumo del atún enlatado de la marca B, con la cual se superaría la ingesta semanal tolerable de 1,6 ug/kg/semana. Por lo tanto, se recomienda un monitoreo continuo de mercurio total y metilmercurio en atún enlatado.

ABSTRACT Objective The objective of this work was to determine the concentration of total mercury (THg) and methylmercury (MeHg) in canned tuna, distributed in supermarkets a city Caribbean coast, Colombia. Materials and Methods We analyzed 160 samples from four different brands identified as A, B, C and D marketed from August to November 2017. Simple sampling by attribute was carried out monthly. The THg and MeHg were determined using a DMA-80 Direct Mercury Analysis System-Milestone and a gas chromatograph Autosystem XL Perkin Elmer. Results The average of THg and MeHg was 0,589 ± 0,163 and 0,536 ± 0,148 μg/g, respectively. The highest concentration of THg and MeHg in tuna was presented by the B mark (HgT: 0,792 ± 0,165, MeHg: 0,725 ± 0,127). Conclusions The health risk assessment due to the consumption of canned tuna, based on the estimated weekly intake (EWI), suggests that the consumption of tuna from the different brands does not associate the possibility of health risk in the group of adults of the population (GAP), when presenting values below the tolerable weekly intake (3,2 μg/kg/ week). While for the groups of children (CH) and women of childbearing age (WCHA) the consumption of canned tuna of the B brand represents a risk to health, when the tolerable weekly intake exceeds 1,6 μg/kg/ week. Therefore, continuous monitoring of Hg-T and Hg-Me in tuna is recommended.

Heavy metal pollution and toxicity assessment in Mallorquin swamp: A natural protected heritage in the Caribbean Sea, Colombia.

This work reports the level and ecotoxicity impact of metals in the sediments of the Mallorquín swamp, a protected coastal lagoon in the Caribbean coast of Colombia. The distribution of metals was in the following decreasing order: Zn > Cu > Pb > Cd > Hg, showing statistically significant differences among sites. The average Pb and Cd concentrations in sediments were about 17 and 5 times higher, respectively, compared to those in background values. Several contamination indices suggested moderate contamination of Hg, Cu, and Zn, and strong pollution due to Cd and Pb. Multivariate analysis revealed spatial variations for metals and its anthropogenic origin, such as municipal and industrial wastewater discharges (Pb, Zn, and Hg) and agricultural activities (Cd and Cu). These findings showed the negative impact of human activities and the need to apply protective management strategies.

Sea Cucumber as Bioindicator of Trace Metal Pollution in Coastal Sediments.

Sea cucumbers are fished worldwide for export to Asia, but few studies have evaluated metal pollution and risk assessment. This study assessed concentration of trace metals and the potential ecological risk in sea cucumber (Holothuria floridana) and sediments at the Cispatá Bay, in the Caribbean Coast of Colombia. The trace metal concentrations in biota and sediments showed a similar decreasing trend as follows: Cu > Zn > Hg > Pb > Cd. The highest bioconcentration factor was found for Hg, and according to the sediment quality guidelines, Cu levels indicate adverse biological effects in the ecosystem. In this regard, Cu levels were higher than effects range low and the threshold effect levels (TEL) and lowest effect level in all the stations, whereas Hg levels were higher than TEL in most of them. Results for health risk assessment based on the maximum allowable daily consumption rate (CRlim) suggest that there is no risk to adults; however, children should limit or avoid its consumption. Results from multivariate statistical analysis suggest that agricultural activities (i.e., application of fertilizers and agrochemicals) were identified as the main anthropogenic sources of metal pollution. This research suggest that sea cucumber could be used as a bioindicator species in studies of monitoring metal contamination, with special attention to the highly significant correlation between Zn in tissue and sediments. This study also reveals that anthropic activities may have negative effects in the quality of the sediments of the bay and contributing to the knowledge of metal accumulation in sea cucumber.Graphical abstract.

Assessment of trace element pollution and ecological risks in a river basin impacted by mining in Colombia.

Trace element pollution in rivers by anthropogenic activities is an increasing problem worldwide. In this study, the contamination and ecological risk by several trace elements were evaluated along a 100-km stretch of the San Jorge River in Colombia, impacted by different mining activities. The increase of average concentration levels and range of trace elements in sediments (in µg/g) was as follows: Cu 6656 (454-69,702) > Cd 1159 (0.061-16,227) > Zn 1064 (102-13,483) > Ni 105 (31-686) > Pb 7.2 (5.1-11.7) > As 1.8 (1.0-3.2) > Hg 0.31 (0.12-1.37). Results showed that surface sediments could be classified as very high ecological risk index (RI > 600), associated with high contamination of Hg, Cd, and Cu, in stations close mining activities. Values for pollution load index indicate an environmental deterioration (PLI > 1), and sediment quality guidelines (SQGs) suggested that Cu, Ni, Zn, and Hg caused adverse biological effects. We further used pollution indices such as contamination factor (CF), enrichment factor (EF), and geoaccumulation index (Igeo) to assess the extent of contamination. According to these indices, discharges of hazardous chemicals over many years have resulted in a high degree of pollution for Cu, Pb, and Cd, with critical values in stations receiving wastes from mining activities. Multivariate statistical analysis suggested that Hg, Cd, Cu, and Zn derived from gold and coal mining, Ni and As were related from the mining of ferronickel and coal, respectively, whereas the high Pb load was attributed to diffuse source of pollution. In sum, our study provided the first detailed database on metal concentration and ecological risks to organisms in sediments of the San Jorge River Basin, and the current results also suggested future research for public health action.

Assessment of Potential Health Risks Associated with the Intake of Heavy Metals in Fish Harvested from the Largest Estuary in Colombia.

This study assesses the potential human health risks posed by six heavy metals (Hg, As, Pb, Cd, Cu, and Zn) found in five of the most consumed fish species (Mugil incilis, Centropomus undecimalis, Cathorops mapale, Eugerres plumieri, and Elops smithi) collected by the riverine population living in Ciénaga Grande de Santa Marta (CGSM), the largest estuary in Colombia. Metal concentrations were low compared with those reported in other regions around the world and the maximum value established by international monitoring organizations. The estimation of the potential risk (HQ) indicated that Cu and Hg could generate negative effects in groups of women of childbearing age (WCA) and the remaining population (RP), because they exceeded their related reference doses, with HQ values > 1; however, Cu and Hg concentrations were not high in fish and EWI, MFW, or MeHgPSL values shows that there is no evidence of a potential health risk from MeHg exposure in the study population. Therefore, the recommendations are to establish continuous monitoring of heavy metals together with strategies that address the high fish consumption, as well as to implement mechanisms for the mitigation of contamination of the watershed, to ensure the safety of organisms in the ecosystem and human health, not only of populations who depend on aquatic resources in the area but also of those that market and consume these resources in the Colombian Caribbean.

[Organochlorine insecticide residues in pasteurized milk distributed in Monteria Colombia]. / Residuos de pesticidas organoclorados en leche pasteurizada distribuida en Montería, Colombia.

OBJECTIVES: To determine and quantify organochlorine pesticide residues in pasteurized cow's milk distributed in the city of Monteria, Colombia. MATERIALS AND METHODS: 144 samples were collected and analyzed for six months (June-December 2013) from eight commercial brands identified as A, B, C, D, E, F, G, H. Simple sampling by attribute was carried out monthly. The POC (points of contact) were determined using a gas chromatograph with electron capture detector, with a capillary column RTX-5 (30.0 m long x 0.25 mm internal diameter, 0.25 pm film thickness). RESULTS: The samples analyzed showed organochlorine pesticides, exceeding the maximum residue limit established by the Codex Alimentarius. The concentrations found were: 0.53; 0.15; 0.57; 0.40; 0.22; 0.20; 0.014; 0.002 and 0.028 mg/Kg of Σα-HCH/ß-HCH, γ-HCH, δ-HCH, ΣAldrin/Dieldrin, ΣHeptachlor/Heptachlor epoxide, Endrin, α-chlordane, γ- chlordane and Endosulfan I, respectively. The brand with the highest number of pesticide residues detected during the study was A. The G brand had the highest concentration of total pesticide residues with 1.46mg/Kg. The C and D brands had lower concentrations with 0.72 and 0.0016mg/Kg, and δ-HCH and γ- chlordane, respectively. CONCLUSIONS: The samples of pasteurized milk under study had organochlorine pesticides residue levels above the maximum residue limit established by the Codex Alimentarius, indicating a risk to public health, especially in children, which the most vulnerable sub-group.

OBJETIVO: Determinar y cuantificar residuos de pesticidas organoclorados en leche de vaca pasteurizada distribuida en la ciudad de Montería, Colombia. MATERIALES Y MÉTODOS: Se colectaron y analizaron 144 muestras durante seis meses (junio-diciembre 2013) de ocho marcas comerciales identificadas como A, B, C, D, E, F, G, H. Mensualmente se realizó un muestreo simple por atributo. Los POCs (puntos de contacto) fueron determinados usando un cromatógrafo de gas con detector captura de electrones, columna capilar RTX-5 (30.0 m longitud x 0.25 mm diámetro interno, 0.25 µÎ¹τι espesor de película). RESULTADOS: En las muestras analizadas se observó la presencia de pesticidas organoclorados, excediendo el Límite Máximo Residual establecido por el Codex Alimentarius. Las concentraciones encontradas fueron: 0.53; 0.15; 0.57; 0.40; 0.22; 0.20; 0.014; 0.002 y 0.028 mg/Kg de Σα-HCH/ß-HCH, γ-HCH, δ-HCH, ΣAldrín/Dieldrín, ΣHeptacloro/Heptacloro epóxido, Endrín, α-Clordano, γ-Clordano y Endosulfán I, respectivamente. La marca con mayor número de residuos de pesticidas detectados durante el estudio fue la A. La marca G presentó mayor concentración de residuos de pesticidas totales con 1.46 mg/Kg. Las marcas C y D presentaron, concentraciones menores de 0.72 y 0.0016 mg/Kg, δ-HCH y γ-Clordano respectivamente. CONCLUSIONES: Las muestras de leche pasteurizada bajo estudio, presentan residuales de pesticidas organoclorados por encima del límite máximo residual establecidos por el Codex Alimentarius, indicando un riesgo para la salud pública especialmente para los niños que es un subgrupo de la población más vulnerable.

Assessment of human health risk associated with methylmercury in the imported fish marketed in the Caribbean.

The decline in marine and freshwaters catches in recent years in Colombia has led to a change in dietary habits, with an increase in the purchase and consumption of imported fish. This is of particular concern as fish are sometimes caught in mercury-contaminated waters, and are subsequently sold canned or uncanned. In addition, canned tuna has received little attention as it is widely assumed that concentrations are low. In this study, total mercury (THg) and methylmercury (MeHg) concentrations were evaluated in three imported fish species marketed in Colombia, Prochilodus lineatus, Prochilodus reticulatus, and Pangasianodon hypophthalmus, plus four brands of canned tuna and one of sardines. One brand of tuna showed the highest mean concentrations of THg (0.543 ±â€¯0.237 µg/g, wet weight, ww) and MeHg (0.518 ±â€¯0.337 µg/g ww), while concentrations in P. hypophthalmus were approximately 30 times lower (≈0.02 µg/g ww). The estimated weekly intake (EWI) in children was above the provisional tolerable weekly intake (PTWI) of MeHg established by the Joint FAO/World Health Organization (WHO) Expert Committee on Food Additives (JECFA) in 2007, 1.6 µg/kg body weight (bw) per week, for all the canned tuna brands. Values for adults were below PTWI, whereas for women of childbearing age, values were above PTWI only for brand D of canned tuna. The estimate of the potential risk indicated that MeHg levels in canned tuna can generate negative effects in vulnerable groups, while the EWI of fresh fish did not pose a threat to the general population. Therefore, establishing strategies to address the high consumption of canned tuna, and continuous monitoring to control commercial food, are recommended to decrease Hg exposure.

Residuos de pesticidas organoclorados en leche pasteurizada distribuida en Montería, Colombia / Organochlorine insecticide residues in pasteurized milk distributed in Monteria Colombia

RESUMEN Objetivo Determinar y cuantificar residuos de pesticidas organoclorados en leche de vaca pasteurizada distribuida en la ciudad de Montería, Colombia. Materiales y Métodos Se colectaron y analizaron 144 muestras durante seis meses (junio-diciembre 2013) de ocho marcas comerciales identificadas como A, B, C, D, E, F, G, H. Mensualmente se realizó un muestreo simple por atributo. Los POCs (puntos de contacto) fueron determinados usando un cromatógrafo de gas con detector captura de electrones, columna capilar RTX-5 (30.0 m longitud x 0.25 mm diámetro interno, 0.25 µÎ¹τι espesor de película). Resultados En las muestras analizadas se observó la presencia de pesticidas organoclorados, excediendo el Límite Máximo Residual establecido por el Codex Alimentarius. Las concentraciones encontradas fueron: 0.53; 0.15; 0.57; 0.40; 0.22; 0.20; 0.014; 0.002 y 0.028 mg/Kg de Σα-HCH/ß-HCH, γ-HCH, δ-HCH, ΣAldrín/Dieldrín, ΣHeptacloro/Heptacloro epóxido, Endrín, α-Clordano, γ-Clordano y Endosulfán I, respectivamente. La marca con mayor número de residuos de pesticidas detectados durante el estudio fue la A. La marca G presentó mayor concentración de residuos de pesticidas totales con 1.46 mg/Kg. Las marcas C y D presentaron, concentraciones menores de 0.72 y 0.0016 mg/Kg, δ-HCH y γ-Clordano respectivamente. Conclusiones Las muestras de leche pasteurizada bajo estudio, presentan residuales de pesticidas organoclorados por encima del límite máximo residual establecidos por el Codex Alimentarius, indicando un riesgo para la salud pública especialmente para los niños que es un subgrupo de la población más vulnerable.(AU)

ABSTRACT Objectives To determine and quantify organochlorine pesticide residues in pasteurized cow's milk distributed in the city of Monteria, Colombia. Materials and Methods 144 samples were collected and analyzed for six months (June-December 2013) from eight commercial brands identified as A, B, C, D, E, F, G, H. Simple sampling by attribute was carried out monthly. The POC (points of contact) were determined using a gas chromatograph with electron capture detector, with a capillary column RTX-5 (30.0 m long x 0.25 mm internal diameter, 0.25 pm film thickness). Results The samples analyzed showed organochlorine pesticides, exceeding the maximum residue limit established by the Codex Alimentarius. The concentrations found were: 0.53; 0.15; 0.57; 0.40; 0.22; 0.20; 0.014; 0.002 and 0.028 mg/Kg of Σα-HCH/ß-HCH, γ-HCH, δ-HCH, ΣAldrin/Dieldrin, ΣHeptachlor/Heptachlor epoxide, Endrin, α-chlordane, γ- chlordane and Endosulfan I, respectively. The brand with the highest number of pesticide residues detected during the study was A. The G brand had the highest concentration of total pesticide residues with 1.46mg/Kg. The C and D brands had lower concentrations with 0.72 and 0.0016mg/Kg, and δ-HCH and γ- chlordane, respectively. Conclusions The samples of pasteurized milk under study had organochlorine pesticides residue levels above the maximum residue limit established by the Codex Alimentarius, indicating a risk to public health, especially in children, which the most vulnerable sub-group.(AU)

Human health impacts of exposure to metals through extreme consumption of fish from the Colombian Caribbean Sea.

The health risks of metal exposure due to the high consumption of fish were assessed for a riverine population living on the Caribbean coast of Colombia. The concentrations of metals (Cd, Cr, Cu, Hg, Ni, Pb and Zn) in the edible tissues of fish were determined and used for risk assessment. The daily fish consumption of residents (n = 95) was as high as 283, 366 and 469 g/day in children (CH), women of childbearing age (WCHA) and the remaining population groups (RP), respectively. The estimation of the potential risk (HQ) indicated that there was no health risk from most of the metals, because they did not exceed their related reference doses, with values of HQ < 1. Although the concentrations of Pb and Hg were not particularly high in fish (<0.2 µg/g), their possible health effects for vulnerable groups are of great concern due to the extremely high fish intake. The Pb intake for all groups was higher than the lower confidence limit of the benchmark dose for nephrotoxicity and neurodevelopmental effects in children. The weekly intake of methylmercury was also elevated, with values approximately 3, 2 and 1.5 times the provisional tolerable weekly intake for CH, WCHA and RP, respectively. Moreover, higher Hg levels were found in top predators, whereas maximum levels for other metals were found in bottom-feeding fish. This study highlights that an accurate data of daily intake, a continuous monitoring of metals in fish and their related fish consumption advisories to protect subsistence fishing communities are recommended in a local and worldwide context.

Assessment of heavy metal pollution, spatial distribution and origin in agricultural soils along the Sinú River Basin, Colombia.

The presence of metals in agricultural soils from anthropogenic activities such as mining and agricultural use of metals and metal-containing compounds is a potential threat for human health through the food chain. In this study, the concentration of heavy metals in 83 agricultural soils irrigated by the Sinú River, in northern Colombia, affected by mining areas upstream and inundated during seasonal floods events were determined to evaluate their sources and levels of pollution. The average concentrations of Cu, Ni, Pb, Cd, Hg and Zn were 1149, 661, 0.071, 0.040, 0.159 and 1365mg/kg respectively and exceeded the world normal averages, with the exception of Pb and Cd. Moreover, all values surpassed the background levels of soils in the same region. Soil pollution assessment was carried out using contamination factor (CF), enrichment factor (EF), geoaccumulation index (Igeo) and a risk assessment code (RAC). According to these indexes, the soils show a high degree of pollution of Ni and a moderate to high contamination of Zn and Cu; whereas, Pb, Cd and Hg present moderate pollution. However, based on the RAC index, a low environmental risk is found for all the analysed heavy metals. Multivariate statistical analyses, principal component and cluster analyses, suggest that soil contamination was mainly derived from agricultural practices, except for Hg, which was caused probably by atmospheric and river flow transport from upstream gold mining. Finally, high concentrations of Ni indicate a mixed pollution source from agricultural and ferronickel mining activities.

Removal of mercury from gold mine effluents using Limnocharis flava in constructed wetlands.

Phytoremediation has received increased attention over the recent decades, as an emerging and eco-friendly approach that utilizes the natural properties of plants to remediate contaminated water, soils or sediments. The current study provides information about a pilot-scale experiment designed to evaluate the potential of the anchored aquatic plant Limnocharis flava for phytoremediation of water contaminated with mercury (Hg), in a constructed wetland (CW) with horizontal subsurface flow (HSSF). Mine effluent used in this experiment was collected from a gold mining area located at the Alacran mine in Colombia (Hg: 0.11 ± 0.03 µg mL-1) and spiked with HgNO3 (1.50 ± 0.09 µg mL-1). Over a 30 day test period, the efficiency of the reduction in the heavy metal concentration in the wetlands, and the relative metal sorption by the L. flava, varied according to the exposure time. The continued rate of removal of Hg from the constructed wetland was 9 times higher than the control, demonstrating a better performance and nearly 90% reduction in Hg concentrations in the contaminated water in the presence of L. flava. The results in this present study show the great potential of the aquatic macrophyte L. flava for phytoremediation of Hg from gold mining effluents in constructed wetlands.

Mercury uptake and effects on growth in Jatropha curcas.

The use of metal-accumulating plants for the phytoremediation of contaminated soils is gaining more attention. Mercury (Hg)-contaminated soils from historical gold mines represent a potential risk to human health and the environment. Therefore, Jatropha curcas plant, that has shown its tolerance to these environments, is a species of particular interest to implement phytoremediation techniques in gold mining sites. In this work, the behavior of J. curcas was assessed in different hydroponic cultures fortified with Hg at concentrations of 5, 10, 20, 40, and 80µgHg/mL (T5, T10, T20, T40 and T80, respectively). After exposure, plant growth, net photosynthesis, leaf area, and Hg accumulation were determined and variables such as net Hg uptake, effective Hg accumulation, translocation and bioaccumulation factors were calculated. Accumulation of Hg in root and leaf tissues increased with respect to the Hg concentrations in the hydroponic culture, with statistically significant differences (p<0.05) among treatments. Moreover, Hg concentration in roots was 7 and 12-fold higher in average than in plant leaves and shoots, respectively. Many effects were found in the development of plants, especially related with loss of biomass and leaf area, with significant growth inhibition related to control values (>50% with treatment T5). Moreover, percentage of inhibition was even higher (>60%) with same treatment for net photosynthesis. Finally, it should be highlighted that for T40 and T80 treatments, plant growth and photosynthesis were almost completely depleted (88%-95%).

Screening of native plant species for phytoremediation potential at a Hg-contaminated mining site.

Artisanal and small-scale gold mining (ASGM) is the largest sector of demand for mercury (Hg), and therefore, one of the major sources of Hg pollution in the environment. This study was conducted in the Alacrán gold-mining site, one of the most important ASGM sites in Colombia, to identify native plant species growing in Hg-contaminated soils used for agricultural purposes, and to assess their potential as phytoremediation systems. Twenty-four native plant species were identified and analysed for total Hg (THg) in different tissues (roots, stems, and leaves) and in underlying soils. Accumulation factors (AF) in the shoots, translocation (TF) from roots to shoots, and bioconcentration (BCF) from soil-to-roots were determined. Different tissues from all plant species were classified in the order of decreasing accumulation of Hg as follows: roots > leaves > stems. THg concentrations in soil ranged from 230 to 6320 ng g(-1). TF values varied from 0.33 to 1.73, with high values in the lower Hg-contaminated soils. No correlation was found between soils with low concentrations of Hg and plant leaves, indicating that TF is not a very accurate indicator, since most of the Hg input to leaves at ASGM sites comes from the atmosphere. On the other hand, the BCF ranged from 0.28 to 0.99, with Jatropha curcas showing the highest value. Despite their low biomass production, several herbs and sub-shrubs are suitable for phytoremediation application in the field, due to their fast growth and high AF values in large and easily harvestable plant parts. Among these species, herbs such as Piper marginathum and Stecherus bifidus, and the sub-shrubs J. curcas and Capsicum annuum are promising native plants with the potential to be used in the phytoremediation of soils in tropical areas that are impacted by mining.

Geochemistry of mercury in tropical swamps impacted by gold mining.

Artisanal and small-scale gold mining (ASGM) poses a serious threat to the local environment. Colombia has very active ASGM activities, where mercury (Hg) ends in piles of mining waste, soils, and waterways. In this study, we assessed Hg speciation and bioavailability in sediments of two tropical swamps, impacted by ASGM. In Ayapel swamp, total Hg (T-Hg) concentrations in sediments ranged between 145 and 313 ng g(-1) dry weight (dw) (mean: 235 ± 49 ng g(-1) dw), whereas Grande Achi swamp levels are 3-fold higher (range: 543-1021 ng g(-1) dw; mean: 722 ± 145 ng g(-1) dw). Even though lower levels of Hg were found in Ayapel, methylation was found to be significantly higher than in Grande Achi, and it is significantly higher in the dry than in the rainy season for both swamps. This increased methylation is linked to the statistically significant correlation between T-Hg, MeHg and organic matter in the Ayapel swamp. In fact, Hg content in both swamps is mainly associated to the organic fraction (Hg-o), with a higher statistically significant difference in Ayapel (43 ± 5%) compared to Grande Achi (33 ± 5%). On the other hand, a significant percentage (30 ± 6%) of elemental Hg fraction (Hg-e) was found in Grande Achi, directly related with Hg released during the gold recovery process from upstream ASGM sites. The percentage of the bioavailable fraction (Hg-w and Hg-h) is elevated (up to 15%), indicating a potential risk to the aquatic environment and human health because these labile Hg species could enter the water column and bioaccumulate in biota.

Phytoremediation of mercury-contaminated soils by Jatropha curcas.

Jatropha curcas plants species were tested to evaluate their phytoremediation capacity in soils contaminated by different levels of mercury. The experimental treatments consisted of four levels of mercury concentrations in the soil - T0, T1, T5, and T10 (0, 1, 5, and 10 µg Hg per g soil, respectively). The total mercury content absorbed by the different plant tissues (roots, stems and leaves) was determined during four months of exposure. The growth behavior, mercury accumulation, translocation (TF) and bioconcentration (BCF) factors were determined. The different tissues in J. curcas can be classified in order of decreasing accumulation Hg as follows: roots>leaves>stems. The highest cumulative absorption of the metal occurred between the second and third month of exposure. Maximum TF was detected during the second month and ranged from 0.79 to 1.04 for the different mercury concentrations. Values of BCF ranged from 0.21 to 1.43. Soils with T1 showed significantly higher BCF (1.43) followed by T10 (1.32) and T5 (0.91), all of them at the fourth month. On the other hand TFs were low (range 0.10-0.26) at the en of the experiment. The maximum reduction of biomass (16.3%) occurred for T10 (10 µg Hg g(-1)). In sum, J. curcas species showed high BCFs and low TFs, and their use could be a promising approach to remediating mercury-contaminated soils.

Speciation and bioavailability of mercury in sediments impacted by gold mining in Colombia.

Mercury (Hg) speciation and bioavailability were studied in surface sediments affected by artisanal and small-scale gold mining (ASGM) in the Mojana region of Colombia. The results demonstrated higher levels in sampling stations that receive water streams carrying Hg from mining areas. The T-Hg concentrations were slightly elevated with values between 196.2 and 1187.6 ng g(-1) dry weight (dw) (mean 524.2±256.8 ng g(-1) dw). The MeHg concentrations were significantly correlated with the T-Hg and organic matter (OM) and represent between 1.7% and 3.6% (mean: 2.6%) of the T-Hg. A five-step sequential extraction procedure shown that most of T-Hg in sediments occur primarily as organically bound Hg (Hg-o), which constitutes 48.4% of the T-Hg, followed by elemental Hg fraction (Hg-e) bound to amorphous compounds, such as Fe/Mn oxides with 26.5%, and the fraction bound to sulfur (Hg-s), which constitutes 18.7%. Exchangeable Hg (Hg-w; water-soluble Hg and stomach acid soluble mercury; Hg-h) represents between 1.7% and 4.7%. These fractions constitute a low percentage but exhibit a high level of risk when entering the water column, and they can bioaccumulate in organisms. The significant relationship between OM, T-Hg and MeHg suggests an important role in the control of the distribution, mobility and bioavailability of the Hg in the sediments.