Fluoride in weathered rock aquifers of southern India: Managed Aquifer Recharge for mitigation

Climatic condition, geology, and geochemical processes in an area play a major role on groundwater quality. Impact of these on the fluoride content of groundwater was studied in three regions—part of Nalgonda district in Telangana, Pambar River basin, and Vaniyar River basin in Tamil Nadu, southern India, which experience semi-arid climate and are predominantly made of Precambrian rocks. High concentration of fluoride in groundwater above 4 mg/l was recorded. Human exposure dose for fluoride through groundwater was higher in Nalgonda than the other areas. With evaporation and rainfall being one of the major contributors for high fluoride apart from the weathering of fluoride rich minerals from rocks, the effect of increase in groundwater level on fluoride concentration was studied. This study reveals that groundwater in shallow environment of all three regions shows dilution effect due to rainfall recharge. Suitable managed aquifer recharge (MAR) methods can be adopted to dilute the fluoride rich groundwater in such regions which is explained with two case studies. However, in deep groundwater, increase in fluoride concentration with increase in groundwater level due to leaching of fluoride rich salts from the unsaturated zone was observed. Occurrence of fluoride above 1.5 mg/l was more in areas with deeper groundwater environment. Hence, practicing MAR in these regions will increase the fluoride content in groundwater and so physical or chemical treatment has to be adopted. This study brought out the fact that MAR cannot be practiced in all regions for dilution of ions in groundwater and that it is essential to analyze the fluctuation in groundwater level and the fluoride content before suggesting it as a suitable solution. Also, this study emphasizes that long-term monitoring of these factors is an important criterion for choosing the recharge areas.     

Arsenic behavior in newly drilled wells

In the present paper, inorganic arsenic species and chemical parameters in groundwater were determined to investigate the factors related to the distribution of arsenic species and their dissolution from rock into groundwater. For the study, groundwater and core samples were taken at different depths of two newly drilled wells in Huron and Lapeer Counties, Michigan. Results show that total arsenic concentrations in the core samples varied, ranging from 0.8 to 70.7 mg/kg. Iron concentration in rock was about 1800 times higher than that of arsenic, and there was no correlation between arsenic and iron occurrences in the rock samples. Arsenic concentrations in groundwater ranged from <1 to 171 microg/l. The arsenic concentration in groundwater depended on the amount of arsenic in aquifer rocks, and as well decreased with increasing depth. Over 90% of arsenic existed in the form of As(III), implying that the groundwater systems were in the reduced condition. The results such as high ferrous ion, low redox potential and low dissolved oxygen supported the observed arsenic species distribution. There was no noticeable difference in the total arsenic concentration and arsenic species ratio between unfiltered and filtered (0.45 microm) waters, indicating that the particulate form of arsenic was negligible in the groundwater samples. There were correlations between water sampling depth and chemical parameters, and between arsenic concentration and chemical parameters, however, the trends were not always consistent in both wells.     

Removal of trace elements in three horizontal sub-surface flow constructed wetlands in the Czech Republic

Between March 2006 and June 2008 removal of 34 trace elements was measured on a monthly basis at three horizontal-flow constructed wetlands in the Czech Republic designed to treat municipal wastewater. In general, the results indicated a very wide range of removal efficiencies among studied elements. The highest degree of removal (average of 90%) was found for aluminum. High average removal was also recorded for zinc (78%). Elements removed in the range of 50-75% were uranium, antimony, copper, lead, molybdenum, chromium, barium, iron and gallium. Removal of cadmium, tin, mercury, silver, selenium and nickel varied between 25 and 50%. Low retention (0-25%) was observed for vanadium, lithium, boron, cobalt and strontium. There were two elements (manganese and arsenic) for which average outflow concentrations were higher compared to inflow concentrations. Reduced manganese compounds are very soluble and therefore they are washed out under anaerobic conditions.     

Fluoride levels in well-water from a chronic arsenicism area of Northern Mexico

This paper reports on the concentrations and geographical relationships between fluoride and total arsenic in 129 water wells of the Región Lagunera, Mexico, where arsenic has caused severe health effects. Fluoride concentrations ranged from less than 0.5 to 3.7 mg liter(-1); 25 samples (19.4%) had levels above 1.5mg liter(-1), the current WHO and Mexican drinking water standard, whereas 45 (34.9%) had levels below 0.5 mg liter(-1). The range of total arsenic concentrations was 0.008-0.624 mg liter(-1) and 64 (50%) had levels above 0.050 mg liter(-1), the current WHO standard. A linear regression analysis of arsenic and fluoride concentrations showed a highly positive correlation (r = 0.774), consistent with their geographical distribution. The highest concentrations of both elements were found in the northeastern part of the Región, mostly corresponding to rural areas, whereas the lowest concentrations were found in the southwestern part of the Región, as well as in the cities of Torreón in the state of Coahuila, and Gómez Palacio and Lerdo in the state of Durango. In consequence, people exposed to high arsenic concentrations are also exposed to fluoride at levels above the drinking water standard. The possibility of interactions between both elements is also discussed.     

Mobilization of arsenic from subsurface sediments by effect of bicarbonate ions in groundwater

Arsenic leaching by bicarbonate ions has been investigated in this study. Subsurface sediment samples from Bangladesh were treated with different carbonate and bicarbonate ions and the results demonstrate that the arsenic leaching efficiency of the carbonate solutions decreased in the order of Na2CO3>NaHCO3>BaCO3>MnCO3. Sodium carbonate and bicarbonate ions extracted arsenic most efficiently; Na2CO3 leached maximum 118.12 microg/l of arsenic, and NaHCO3, 94.56 microg/l of arsenic from the Ganges delta sediments after six days of incubation. The arsenic concentrations extracted in the batch experiments correlated very well with the bicarbonate concentrations. The kinetics study of arsenic release indicates that arsenic-leaching rate increased with reaction time in bicarbonate solutions. Bicarbonate ions can extract arsenic from sediment samples in both oxic and anoxic conditions. A linear relationship found between arsenic contents in core samples and those in leachates suggests that dissolved arsenic concentration in groundwater is related to the amount of arsenic in aquifer sediments. In batch experiment, bicarbonate solutions effectively extracted arsenic from arsenic adsorbed iron oxyhydroxide, reflecting that bicarbonate solutions may mobilize arsenic from iron and manganese oxyhydroxide in sediments that are ubiquitous in subsurface core samples. Carbonate ion may form complexes on the surface sites of iron hydroxide and substitute arsenic from the surface of minerals and sediments resulting in release of arsenic to groundwater. Like in the batch experiment, arsenic and bicarbonate concentrations in groundwater of Bangladesh correlated very well. Therefore, bicarbonate leaching is presumed to be one important mechanism to mobilize arsenic in bicarbonate dominated reducing aquifer of Bangladesh and other parts of the world as well.     

Arsenic and other heavy metals in soils from an arsenic-affected area of West Bengal,India

Domkal is one of the 19, out of 26 blocks in Murshidabad district where groundwater contains arsenic above 0.05 mg/l. Many millions of cubic meters of groundwater along with arsenic and other heavy metals are coming out from both the hand tubewells, used by the villagers for their daily needs and shallow big diameter tubewells, installed for agricultural irrigation and depositing on soil throughout the year. So there is a possibility of soil contamination which can moreover affect the food chain, cultivated in this area. A somewhat detailed study was carried out, in both micro- and macrolevel, to get an idea about the magnitude of soil contamination in this area. The mean concentrations (mg/kg) of As (5.31), Fe (6740), Cu (18.3), Pb (10.4), Ni (18.8), Mn (342), Zn (44.3), Se (0.53), Mg (534), V (44.6), Cr (33.1), Cd (0.37), Sb (0.29) and Hg (0.54) in fallow land soils are within the normal range. The mean As (10.7), Fe (7860) and Mg (733) concentrations (mg/kg) are only in higher side whereas Hg (0.17 mg/kg) is in lower side in agricultural land soils, compared to the fallow land soils. Arsenic concentrations (11.5 and 28.0 mg/kg respectively) are high in those agricultural land soils where irrigated groundwater contains high arsenic (0.082 and 0.17 mg/l respectively). The total arsenic withdrawn and mean arsenic deposition per land by the 19 shallow tubewells per year are 43.9 kg (mean: 2.31 kg, range: 0.53-5.88 kg) and 8.04 kg ha(-1) (range: 1.66-16.8 kg ha(-1)) respectively. For the macrolevel study, soil arsenic concentration decreases with increase of distance from the source and higher the water arsenic concentration, higher the soil arsenic at any distance. A proper watershed management is urgently required to save the contamination.     

Arsenic species and chemistry in groundwater of southeast Michigan

Groundwater samples, taken from 73 wells in 10 counties of southeast Michigan in 1997 had arsenic concentrations in the range of 0.5 to 278 microg/L the average being 29 microg/l. About 12% of these wells had arsenic concentrations that exceeded the current USEPA's maximum contaminant level of 50 microg/l. Most (53-98%) of the arsenic detected was arsenite [As(III)] and other observations supported the arsenic species distribution (low redox potential and DO). In shallow groundwater (< 15 m), arsenic concentrations are low likely due to the formation of insoluble ferrosoferric hydroxide complex. In deep groundwater (> 15 m), the concentration of arsenic is possibly controlled by reductive dissolution of arsenic-rich iron hydroxide/oxyhydroxide and dissolution of arsenic sulfide minerals.     

Enrichment of trace elements in the clay size fraction of mining soils

Reactive waste dumps with sulfide minerals promote acid mine drainage (AMD), which results in water and soil contamination by metals and metalloids. In these systems, contamination is regulated by many factors, such as mineralogical composition of soil and the presence of sorption sites on specific mineral phases. So, the present study dedicates itself to understanding the distribution of trace elements in different size fractions (<2-mm and <2-μm fractions) of mining soils and to evaluate the relationship between chemical and mineralogical composition. Cerdeirinha and Penedono, located in Portugal, were the waste dumps under study. The results revealed that the two waste dumps have high degree of contamination by metals and arsenic and that these elements are concentrated in the clay size fraction. Hence, the higher degree of contamination by toxic elements, especially arsenic in Penedono as well as the role of clay minerals, jarosite, and goethite in retaining trace elements has management implications. Such information must be carefully thought in the rehabilitation projects to be planned for both waste dumps.     

Trace element accumulation in the moss Hypnum cupressiforme Hedw. and the trees Quercus ilex L. and Pinus halepensis Mill. in Catalonia

We studied trace element accumulation in the moss Hypnum cupressiforme and the widely distributed Mediterranean trees Quercus ilex and Pinus halepensis located at increasing distances from the Barcelona Metropolitan Area. Hypnum cupressiforme, Quercus ilex and, to a somewhat lesser extent, Pinus halepensis, have proved to be adequate as possible accumulative monitoring species in relation to trace elements pollution. No significant effects of crown orientation were found. One-year old leaves generally accumulated more trace elements than current-year leaves. All the studied trace elements showed greatest concentrations in the Barcelona Metropolitan Area, with lead, cadmium and arsenic concentrations being especially high. In general, trace element concentrations in biomass were similar or higher than the values reported from other Mediterranean urban areas of Europe. The top soil-layer concentrations were also higher in the Barcelona Metropolitan Area indicating the existence of mechanisms of atmospheric deposition and/or concentration in the soil. The lower values of Pb of airborne origin relative to other elements such as Cd, Cu, Zn and Sb suggest that traffic exhausts are not the only important focus of pollutants in this area. The results of biomass concentrations and of enrichment factor of biomasses respect to bedrock and soils show that atmospheric inputs account for the higher trace element concentrations in the Barcelona Metropolitan Area.     

Toxic fluoride and arsenic contaminated groundwater in the Lahore and Kasur districts, Punjab, Pakistan and possible contaminant sources

The present study is the first attempt to put forward possible sources of As, F- and SO4(2-) contaminated groundwater in the Kalalanwala area, Punjab, Pakistan. Five rainwater and 24 groundwater samples from three different depths were analyzed. Shallow groundwater from 24 to 27 m depth contained high F- (2.47-21.1mg/L), while the groundwater samples from the deeper depth were free from fluoride contamination. All groundwater samples contained high As (32-1900 microg/L), in excess of WHO drinking water standards. The SO4(2-) ranges from 110 to 1550 mg/L. Delta34S data indicate three sources for SO4(2-) air pollutants (5.5-5.7 per thousand), fertilizers (4.8 per thousand), and household waste (7.0 per thousand). Our important finding is the presence of SO4(2-), As and F- in rainwater, indicating the contribution of these elements from air pollution. We propose that pollutants originate, in part, from coal combusted at brick factories and were mobilized promotionally by the alkaline nature of the local groundwater.     

The Fate of Vanadium in an Urban Air Shed: The Lower Delaware River Valley

Vanadium compounds are toxic pollutants which require engineering control in the design stage. In the lower Delaware River Valley, the main sources are presently the combustion of vanadium rich fuel oils and the catalytic processing of high vanadium crudes. These and other Industrial emissions, result in atmospheric vanadium concentrations which have varied from 0.133 μg/m³ to 0.557 μg/m³ between 1958 and 1969. Compounds of vanadium, principally with oxygen and sulfur, are considered. The dominance of oxygen compounds over sulfur compounds as derived from equilibrium data, and the tendency of vanadium oxides to move toward vanadium’s maximum valence of +5, indicate the prevalence of V₂0₅ as the emission compound.     

Distribution of inorganic arsenic species in mine tailings of abandoned mines from Korea

The main objective of the present study is to determine arsenic species in mine tailings by applying an ion exchange method. Three abandoned mines, Jingok, Cheonbo and Sino mines in Korea, which had produced mainly gold, were selected for the collection and analysis of the tailings. It was found that the arsenic speciation using an ion exchange method was effective to separate As(III) and As(V) in leachate of mine tailings. The concentration of As(V) was found to be 63-99% in the leachate, indicating that As(V) would be the major arsenic species in the mine tailings and the tailings were under oxic conditions. The total concentrations of arsenic and metal elements in the mine tailings were up to 62,350 mg/kg As, 40 wt.% Fe, 21,400 mg/kg Mn, and 7,850 mg/kg Al. Sulfate was the dominant anion throughout the leachate, reaching a maximum dissolved concentration of 734 mg/l. The results of XRD and SEM in the mine tailings showed that main arsenic-containing minerals were pyrite (FeS2) and arsenopyrite (FeAsS) which would be the source of arsenic contamination in the study area.     

Enhanced mobilization of arsenic and heavy metals from mine tailings by humic acid

Arsenic and heavy metal mobilization from mine tailings is an issue of concern as it might pose potential groundwater or ecological risks. Increasing attention recently has been focused on the effects of natural organic matter on the mobility behavior of the toxicants in the environment. Column experiments were carried out in this research study to evaluate the feasibility of using humic acid (HA) to mobilize arsenic and heavy metals (i.e., Cu, Pb and Zn) from an oxidized Pb-Zn mine tailings sample collected from Bathurst, New Brunswick, Canada. Capillary electrophoresis analyses indicated that arsenate [As(V)] was the only extractable arsenic species in the mine tailings and the addition of HA at pH 11 did not incur the oxidation-reduction or methylation reactions of arsenic. A 0.1% HA solution with an initial pH adjusted to 11 was selected as the flushing solution, while distilled water (initial pH adjusted to 11) was used as the control to account for the mobilization of arsenic and the heavy metals by physical mixing and the effect of pH. It was found that the HA could significantly enhance the mobilization of arsenic and heavy metals simultaneously from the mine tailings. After a 70-pore-volume-flushing, the mobilization of arsenic, copper, lead and zinc reached 97, 35, 838 and 224 mg kg(-1), respectively. The mobilization of arsenic and the heavy metals was found to be positively correlated with the mobilization of Fe in the presence of the HA. Moreover, the mobilization of arsenic was also correlated well with that of the heavy metals. The mobilization of co-existing metals to some extent might enhance arsenic mobilization in the presence of the HA by helping incorporate it into soluble aqueous organic complexes through metal-bridging mechanisms. Use of HA in arsenic and heavy metal remediation may be developed as an environmentally benign and possible effective remedial option to reduce and avoid further contamination.     

Interannual patterns of variation in concentrations of trace elements in arms of Octopus vulgaris

Concentrations of essential (copper, iron, manganese, selenium, and zinc) and non-essential (arsenic, cadmium, mercury, and lead) trace elements were measured in arms of Octopus vulgaris. The cephalopods were sampled from commercial fishery landings at two sites on the Portuguese coast in spring 2002 and 2003. Mercury was determined using an Advanced Mercury Analyser Spectrophotometer (AMAS) and other trace elements were measured using inductively coupled plasma-atomic emission spectrometry (ICP-AES). Since high levels of arsenic were detected, identification of the forms present was carried out using high performance liquid chromatography (HPLC) followed by ICP-MS. Mean concentrations of trace elements analysed were in the following order: As > Zn > Fe > Cu > Cd > Pb > Se > Mn > Hg. The results of speciation of arsenic demonstrate that virtually all arsenic was in the arsenobetaine form, which is the less toxic form. The concentrations of several trace elements were generally high in samples from Viana in 2002. Cadmium concentrations were above the legal limit for human consumption in samples from Viana in 2002 and two of these animals also had lead concentrations that exceeded legal limits. Mercury appeared in all samples but levels were within legally defined safe limits. No relationship was detected between trace element concentrations and size or maturity of octopus.     

Formation of fine particles enriched by V and Ni from heavy oil combustion: Anthropogenic sources and drop-tube furnace experiments

The present study attempts to investigate the emission characteristics of fine particles with special emphasis on nickel and vanadium metal elements emitted from the heavy oil combustion in industrial boilers and power plant, which are typical anthropogenic sources in Korea. A series of combustion experiments were performed to investigate the emission characteristics of particles in the size range of submicron by means of drop-tube furnace with three major domestic heavy oils. Cascade impactors were utilized to determine the size distribution of particulates as well as to analyze the partitioning enrichment of vanadium and nickel in various size ranges. Experimental results were compared with field data of particle size distribution and metal partitioning at commercial utility boilers with heavy oil combustion. Such data were interpreted by chemical equilibrium and particle growth mechanism by means of computational models. In general, fine particles were the major portion of PM₁₀ emitted from the heavy oil combustion, with significant fraction of ultra-fine particles. The formation of ultra-fine particles through nucleation/condensation/coagulation from heavy oil combustion was confirmed by field and experimental data. Vanadium and nickel were more enriched in fine particles, particularly in ultra-fine particles. The conventional air pollution devices showed inefficient capability to remove ultra-fine particles enriched with hazardous transition metal elements such as vanadium and nickel.     

Dynamic studies on the mobility of trace elements in soil and sediment samples influenced by dumping of residues of the flood in the Mulde River region in 2002

In the analysis of soil samples, batch sequential extraction procedures are traditionally used for the fractionation of trace elements to access their mobility and potential risk for the contamination of groundwater. In the present work a continuous-flow technique has been used that enables not only the fast and efficient leaching of trace elements but as well as time-resolved studies on the mobilization of arsenic and selected heavy metals in different forms to be made. Rotating coiled columns (RCC) earlier used mainly in countercurrent chromatography have been successfully applied to the dynamic leaching of heavy metals from soils contaminated by flooding sludge's. The sample was retained in a PTFE rotating column as the stationary phase whereas aqueous solutions were continuously pumped through. The contents of elements were determined by on-line coupling of RCC and inductively coupled plasma atomic emission spectrometry (ICP-AES). This enables real-time data on the leaching process to be obtained. Dynamic and traditional batch procedures were compared. It has been shown that the aqueous elution under centrifugal forced conditions is much more effective for the mobilization of heavy metals. Hence, the dynamic leaching is characterized by a substantially more intensive interaction between solid and water and is besides substantially more time-saving than the conventional batch procedure. The RCC procedure was also employed for preliminary leaching studies with a simulated "acid rain". In comparison with the water leaching, the mobilization of heavy metals and arsenic from soil samples with employment of simulated acid rain as eluent was less effective.     

Assessment of arsenic content in soil,rice grains and groundwater and associated health risks in human population from Ropar wetland,India, and its vicinity

In the present study, potential health risks posed to human population from Ropar wetland and its vicinity, by consumption of inorganic arsenic (i-As) via arsenic contaminated rice grains and groundwater, were assessed. Total arsenic (t-As) in soil and rice grains were found in the range of 0.06–0.11 mg/kg and 0.03–0.33 mg/kg, respectively, on dry weight basis. Total arsenic in groundwater was in the range of 2.31–15.91 μg/L. i-As was calculated from t-As using relevant conversion factors. Rice plants were found to be arsenic accumulators as bioconcentration factor (BCF) was observed to be >1 in 75% of rice grain samples. Further, correlation analysis revealed that arsenic accumulation in rice grains decreased with increase in the electrical conductivity of soil. One-way ANOVA, cluster analysis and principal component analysis indicated that both geogenic and anthropogenic sources affected t-As in soil and groundwater. Hazard index and total cancer risk estimated for individuals from the study area were above the USEPA limits of 1.00 and 1.00 × 10^?6, respectively. Kruskal-Wallis H test indicated that groundwater intake posed significantly higher health risk than rice grain consumption (χ ²(1) = 17.280, p = 0.00003).     

Second german heavy-metal survey by means of mosses,and comparison of the first and second approach in germany and other european countries

This paper shows the geographic distribution in Germany of iron (Fe), nickel (Ni) and lead (Pb) analyzed in mosses in 1995/96 and compares it with the results of the 1990/91 pilot study within a European moss-monitoring programme. Other elements (As, Cd, Cr, Cu, Ti, V, Zn) are compared on basis of the overall element medians for Germany of the 1990/91 and 1995/96 survey. Samples of Pleurozium schreberi, Scleropodium purum, Hypnum cupressiforme and Hylocomium splendens were taken at a total of 1026 sites. In the 1995/96 monitoring campaign, 95% of the original sites of the 1990/91 study were resampled. The results from 1995/96 display local elevated values and many cases of areas affected by known sources of heavy-metal emissions. The industrialized and urban regions of Germany are shown up clearly by the 1995/96 moss-monitoring results: the Ruhr area, parts of Saarland and Baden-Württemberg, as well as areas in eastern Germany. Relatively low values for many elements were found in large areas of Lower Saxony and Bavaria. A comparison of the results of the 1990/91 and 1995/96 moss-monitoring programmes shows a fall in the concentration of the presented elements (except cadmium, copper and zinc) over the relevant period. Especially in the former GDR, chromium (Cr), iron (Fe), titanium (Ti) and vanadium (V) decreased significantly. This is, firstly, a reflection of the closure of and/or technological improvements to large power plants; secondly it is due to the fact that lignite has given way to other fuels. Vanadium (V) and nickel (Ni), typical constituents of crude oil, also show a decrease in the western part and thus document changes in the type of fuel consumed. The significant fall in lead concentration in 1995/96 as compared to 1990/91 in what used to be East and West Germany probably results from the increasing use of lead-free petrol. A comparison of the median values for 1990/91 and 1995/96 in mosses to the rate of emission of heavy metals in Germany for 1990 and 1995 shows similar trends in the case of elements such as arsenic (As), chromium (Cr), nickel (Ni), and lead (Pb). The comparison of the medians of the elements analyzed for 19 European countries indicates for most of the elements a general tendency to lower values in 1995, except for Lithuania, Netherlands, Portugal, Italy and United Kingdom.     

Multivariate statistical evaluation of trace elements in groundwater in a coastal area in Shenzhen, China

Multivariate statistical techniques are efficient ways to display complex relationships among many objects. An attempt was made to study the data of trace elements in groundwater using multivariate statistical techniques such as principal component analysis (PCA), Q-mode factor analysis and cluster analysis. The original matrix consisted of 17 trace elements estimated from 55 groundwater samples colleted in 27 wells located in a coastal area in Shenzhen, China. PCA results show that trace elements of V, Cr, As, Mo, W, and U with greatest positive loadings typically occur as soluble oxyanions in oxidizing waters, while Mn and Co with greatest negative loadings are generally more soluble within oxygen depleted groundwater. Cluster analyses demonstrate that most groundwater samples collected from the same well in the study area during summer and winter still fall into the same group. This study also demonstrates the usefulness of multivariate statistical analysis in hydrochemical studies.