Elucidation and short-term forecasting of microcystin concentrations in Lake Suwa (Japan) by means of artificial neural networks and evolutionary algorithms

Non-supervised artificial neural networks (ANN) and hybrid evolutionary algorithms (EA) were applied to analyse and model 12 years of limnological time-series data of the shallow hypertrophic Lake Suwa in Japan. The results have improved understanding of relationships between changing microcystin concentrations, Microcystis species abundances and annual rainfall intensity. The data analysis by non-supervised ANN revealed that total Microcystis abundance and extra-cellular microcystin concentrations in typical dry years are much higher than those in typical wet years. It also showed that high microcystin concentrations in dry years coincided with the dominance of the toxic Microcystis viridis whilst in typical wet years non-toxic Microcystis ichthyoblabe were dominant. Hybrid EA were used to discover rule sets to explain and forecast the occurrence of high microcystin concentrations in relation to water quality and climate conditions. The results facilitated early warning by 3-days-ahead forecasting of microcystin concentrations based on limnological and meteorological input data, achieving an r(2)=0.74 for testing.     

Analysis of dissolved microcystins in surface water samples from Kovada Lake, Turkey

Dissolved (extracellular) microcystin (MC) concentrations were determined at 3 sampling stations on Lake Kovada, Turkey. The dominant species of cyanobacteria found in August and September of 2006 were Microcystis aeruginosa, Synechococcus sp., Phormidium limosum, Phormidium formosa and Planktothrix limnetica. MC concentrations in water were measured by ELISA and MC variants were examined by HPLC-PDA. Quantitative analysis by HPLC indicated that five MC variants (MC-LR, -RR, -LA, -LW, -LF) were identified in water samples from Kovada Lake. The maximum concentration of dissolved MC-LW was 98.9 µg l^− 1 in October. MC-LR was only detected in May at a concentration of 0.5 µg l^− 1. The cross reactivity of the antibody (MC10E7) to variants such as MC-LA MC-LW & MC-LF was low. Hence the results determined by ELISA were lower than those determined by HPLC in September and October samples due to differences in the specificity of the antibody to MC variants. Total extraceullar MCs was quantified by ELISA and ranged from 0.73 to 48.5 µg MC-LR equivalents l^− 1, which in some cases exceeded the WHO provisional Guideline Value for MC-LR in drinking water. This study confirms that the lakes of Turkey should be monitored for toxic cyanobacteria and for MCs to avoid or reduce the potential exposure of people to these health hazards.     

Occurrence of perchlorate in drinking water sources of metropolitan area in Japan

The occurrence of perchlorate in the Tone River Basin was investigated using an ion chromatograph (IC) coupled with a tandem mass spectrometer (MS/MS). Perchlorate was found at high concentrations in the upper Tone River and its tributary, Usui River, and the maximum concentrations were 340 and 2300 microg/L, respectively. The possible sources of perchlorate in two areas were attributable to industrial effluents. In case of the upper Tone River, perchlorate concentration in an effluent was 1100 microg/L and its concentrations in a tributary (or waterway) directly downstream of the outlet of the effluent ranged from 44 to 1500 microg/L. In case of the Usui River, perchlorate concentration in another effluent was 15,000 microg/L and its concentrations downstream of the outlet of the effluent were 1100-3900 microg/L. Due to the discharge of perchlorate in the upper Tone River Basin, perchlorate concentrations in the river waters of the middle and lower Tone River Basin were generally 10-20 microg/L. Perchlorate concentrations in 30 tap water samples were investigated. Water sources of three tap water samples were other than the Tone River Basin and their perchlorate concentrations were 0.16-0.87 microg/L. On the other hand, water sources of the remaining 27 samples were the upper, middle and lower Tone River Basin and their perchlorate concentrations were 0.06-37 microg/L. Perchlorate concentrations were more than 1 microg/L in 19 tap water samples and more than 10 microg/L in 13 samples. It was shown that tap waters in the Tone River Basin were widely contaminated with perchlorate. To our knowledge, this study was the first to report on perchlorate contamination of environmental and drinking waters in Japan.     

Degradation of microcystin in sediments at oxic and anoxic, denitrifying conditions

The potent toxin microcystin is frequently released during cyanobacterial blooms in eutrophic waters and may impose a risk to human health, when surface water is used for drinking water. For removal of microcystin in surface waters, infiltration through sediment is commonly used. In the present study, mineralization of 14C-labelled microcystin (accumulation of 14CO(2)) and concentration changes (protein phosphatase inhibition assay) demonstrated that indigenous microorganisms in the sediment of a water recharge facility were capable of degrading microcystin. At oxic or microaerophilic (<2% O(2)) conditions, microcystin added to sediment slurries at 70 microg l(-1) was reduced to <20 microg l(-1) in 1-2 weeks, and less than 3 microg l(-1) after 7 weeks. At anoxic conditions (<0.3% O(2)) and with addition of nitrate, the degradation was significantly stimulated, reducing microcystin from 100 to <20 microg l(-1) within 1 day. The simultaneous production of N(2)O in the samples suggests that the microcystin degradation was coupled to dissimilative nitrate reduction (denitrification). Since aquifers and sediments beneath drinking water reservoirs often are anoxic, nitrate respiration may be an important process in removal and detoxification of microcystin.     

Effects of low or medium-pressure UV irradiation on the release of intracellular microcystin

UV irradiation could be an alternative growth inhibition treatment against toxic Microcystis blooms in lakes. This study examined the effect of UV irradiation on the release of toxic intracellular microcystin. Conventional algicidal treatment (e.g. copper sulfate) was known to cause rapid release of intracellular microcystin and additional problems, but no studies have examined the case of UV treatment. A pure culture of Microcystis aeruginosa PCC 7806 was exposed to monochromatic low-pressure or polychromatic medium-pressure UV lamps. Irradiated pure culture suspension was subsequently incubated for 14 days under white light fluorescent lamps. During incubation, profiles of the number of cells, intracellular and extracellular microcystin concentration were determined. After the UV exposure, the number of cells gradually diminished; the net log cell reduction after 6 days of incubation was 1.6 log or 2.0 log for 600 mJ/cm2 of LP or MP UV irradiation, respectively. There were three findings for UV irradiation effects on the release of intracellular microcystin. First, because UV exposure can inhibit increases in the number of cells for about 6 days, it inhibited the increase of microcystin concentrations in water. Second, intracellular microcystin was gradually released into the surrounding water through a gradual reduction in the number of cells, preventing a rapid increase of microcystin concentration in water. Microcystin concentration in water was not significantly higher in UV-irradiated samples than non-UV-irradiated sample. Third, UV irradiation was able to degrade intracellular microcystin; it was reduced from 24.6 to 7.06 or 7.16 fg/cell by 600 mJ/cm2 of LP or MP UV irradiation, respectively. This contributed to reduce increases in microcystin concentrations in water. UV treatment can inhibit Microcystis growth and reduce intracellular microcystin content without rapid release of intracellular microcystin.     

Fish test for endocrine-disruption and estimation of water quality of Japanese rivers

The LC50 values (72 h) of 17beta-estradiol (E2), p-nonylphenol (NP) and bis-phenol-A (BPA) to adult male and female medaka were 3.5 and 3.5, 0.85 and 0.87, and 6.8 and 8.3 mg L(-1), respectively; the LC50 values to embryos were 0.46, 0.13 and 5.1 mg L(-1), respectively. The IC50 values for inhibition to egg hatching were 0.47, 0.85 and 9.0 mg L(-1), respectively. These values were much higher than concentrations detected in river water in Japan and the chemicals were considered to have no lethal effect on the fish in an aquatic environment. Mature male medaka was continuously exposed to 0.005, 0.05 or 1.0 microg L(-1) of E2, or to 0.1, 10 or 100 microg L(-1) of NP or BPA. Female specific proteins (FSP) were induced in the blood of male medaka that were exposed for 5 weeks to E2 higher than 0.005 microg L(-1), NP higher than 0.1 microg L(-1), or BPA higher than 10 microg L(-1). Based on these FSP inducible concentrations and reported concentrations of E2, NP and BPA in Japanese river water, some river water contaminated by E2 or NP could be estimated as the FSP inducible in male medaka.     

Seasonal occurrence and toxicity of Microcystis in impoundments of the Huron River, Michigan, USA

Occurrence and toxicity of Microcystis spp. were measured by ELISA in three impoundments of the Huron River in southeast Michigan, USA. Assays were conducted weekly from June through October 2005. Additional samples were collected to assess microcystin concentrations throughout the drinking water treatment process at the Ann Arbor Water Treatment Facility. Water column stability, nutrient concentrations, and N:P ratios were examined as potential predictors of phycocyanin and microcystin. Microcystin was found in two of the impoundments at seasonally varying concentrations. Microcystis presence was associated with N:P ratios between 40 and 80 by moles, and toxin levels typically peaked one to two weeks after a peak in phycocyanin. The toxin was also detected at low levels at all stages of the drinking water treatment process. Freezing and thawing water samples prior to analysis yielded maximum microcystin assay concentrations. Experiments indicated that the competitive ELISA method is susceptible to false negative reporting. This is the first report of algal toxins in this catchment, and results demonstrate that sensitive and rapid analytical methods offer the chance to link the dynamics of toxin production with environmental conditions.     

Field and laboratory arsenic speciation methods and their application to natural-water analysis

The toxic and carcinogenic properties of inorganic and organic arsenic species make their determination in natural water vitally important. Determination of individual inorganic and organic arsenic species is critical because the toxicology, mobility, and adsorptivity vary substantially. Several methods for the speciation of arsenic in groundwater, surface-water, and acid mine drainage sample matrices using field and laboratory techniques are presented. The methods provide quantitative determination of arsenite [As(III)], arsenate [As(V)], monomethylarsonate (MMA), dimethylarsinate (DMA), and roxarsone in 2-8 min at detection limits of less than 1 microg arsenic per liter (microg As L(-1)). All the methods use anion exchange chromatography to separate the arsenic species and inductively coupled plasma-mass spectrometry as an arsenic-specific detector. Different methods were needed because some sample matrices did not have all arsenic species present or were incompatible with particular high-performance liquid chromatography (HPLC) mobile phases. The bias and variability of the methods were evaluated using total arsenic, As(III), As(V), DMA, and MMA results from more than 100 surface-water, groundwater, and acid mine drainage samples, and reference materials. Concentrations in test samples were as much as 13,000 microg As L(-1) for As(III) and 3700 microg As L(-1) for As(V). Methylated arsenic species were less than 100 microg As L(-1) and were found only in certain surface-water samples, and roxarsone was not detected in any of the water samples tested. The distribution of inorganic arsenic species in the test samples ranged from 0% to 90% As(III). Laboratory-speciation method variability for As(III), As(V), MMA, and DMA in reagent water at 0.5 microg As L(-1) was 8-13% (n=7). Field-speciation method variability for As(III) and As(V) at 1 microg As L(-1) in reagent water was 3-4% (n=3).     

Occurrence of phthalates and bisphenol A and F in the environment

Certain xenoestrogens, namely bisphenol A (BPA), bisphenol F (BPF), butylbenzyl phthalate (BBP), dibutyl phthalate (DBP), and di(2-ethylhexyl)phthalate (DEHP), were measured in various compartments (surface water, sediments, sewage treatment plant effluents, sewage sludge, dump water, liquid manure) in order to contribute to a better understanding of exposure to these compounds in different environments. Hundred and sixteen surface-water samples and 35 sediments from rivers, lakes and channels, 39 sewage effluents, and 38 sewage sludges were collected in Germany. Furthermore, ten liquid manure, two waste-dump and two compost-runoff water samples were also analysed. BPA measurements showed low concentrations from 0.0005 to 0.41 microg L(-1) in surface water, in sewage effluents from 0.018 to 0.702 microg L(-1), in sediments from 0.01 to 0.19 mgkg(-1) and in sewage sludge from 0.004 to 1.363mgkg(-1) dw. Measured concentrations of BPF were clearly lower than BPA in all environmental media. DEHP dominated the phthalate concentrations, which ranged from 0.33 to 97.8 microg L(-1) (surface water), 1.74 to 182 microg L(-1) (sewage effluents), 27.9 to 154 mgkg(-1) dw (sewage sludge) and 0.21 to 8.44 mgkg(-1) (sediment). DBP was found only in minor concentrations and BBP, only in a few samples in low amounts. Very high concentrations of BPA and phthalates were confirmed in waste dump water and compost water samples as well as in the liquid manure samples.     

Arsenic speciation and uranium concentrations in drinking water supply wells in Northern Greece: correlations with redox indicative parameters and implications for groundwater treatment

The cities in the Aksios and Kalikratia areas in Northern Greece rely on arsenic contaminated groundwater for their municipal water supply. As remedial action strongly depends on arsenic speciation, the presence of other possible contaminants, and on the general water composition, a detailed study with samples from 21 representative locations was undertaken. Arsenic concentrations were typically 10-70 microg/L. In the groundwaters of the Aksios area with lower Eh values (87-172 mV), pH 7.5-8.2 and 4-6 mM HCO(3) alkalinity, As(III) predominated. Manganese concentrations were mostly above the EC standard of 0.05 mg/L (0.1-0.7 mg/L). In groundwaters of the Kalikratia area with higher Eh values (272-352 mV), pH 6.7-7.5 and 6-12 mM HCO(3) alkalinity, As(V) was the main species. Uranium in the groundwaters was also investigated and correlations with total arsenic concentrations and speciation were examined to understand more of the redox chemistry of the examined groundwaters. Uranium concentrations were in the range 0.01-10 microg/L, with the higher concentrations to occur in the oxidizing groundwaters of the Kalikratia area. Uranium and total arsenic concentrations showed no correlation, whereas uranium concentrations correlated strongly with As(III)/As(tot) ratios, depicting their use as a possible indicator of groundwater redox conditions. Finally, boron was found to exceed the EC drinking water standard of 1 mg/L in some wells in the Kalikratia area and its removal should also be considered in the design of a remedial action.     

Arsenic in hair and nails of individuals exposed to arsenic-rich groundwaters in Kandal province, Cambodia

The health implications of the consumption of high arsenic groundwater in Bangladesh and West Bengal are well-documented, however, little is known about the level of arsenic exposure elsewhere in Southeast Asia, where widespread exploitation of groundwater resources is less well established. We measured the arsenic concentrations of nail and hair samples collected from residents of Kandal province, Cambodia, an area recently identified to host arsenic-rich groundwaters, in order to evaluate the extent of arsenic exposure. Nail and hair arsenic concentrations ranged from 0.20 to 6.50 microg g(-1) (n=70) and 0.10 to 7.95 microg g(-1) (n=40), respectively, in many cases exceeding typical baseline levels. The arsenic content of the groundwater used for drinking water purposes (0.21-943 microg L(-1) (n=31)) was positively correlated with both nail (r=0.74, p<0.0001) and hair (r=0.86, p<0.0001) arsenic concentrations. In addition, the nail and hair samples collected from inhabitants using groundwater that exceeded the Cambodian drinking water legal limit of 50 microg L(-1) arsenic contained significantly more arsenic than those of individuals using groundwater containing <50 microg L(-1) arsenic. X-ray absorption near edge structure (XANES) spectroscopy suggested that sulfur-coordinated arsenic was the dominant species in the bulk of the samples analysed, with additional varying degrees of As(III)-O character. Tentative linear least squares fitting of the XANES data pointed towards differences in the pattern of arsenic speciation between the nail and hair samples analysed, however, mismatches in sample and standard absorption peak intensity prevented us from unambiguously determining the arsenic species distribution. The good correlation with the groundwater arsenic concentration, allied with the relative ease of sampling such tissues, indicate that the arsenic content of hair and nail samples may be used as an effective biomarker of arsenic intake in this relatively recently exposed population.     

Differences in the chlorine reactivity of four microcystin analogues

The presence of microcystin toxins in drinking water is highly undesirable as they have the potential to adversely affect human health. Consequently, effective removal of these toxins from water is a major goal for water authorities. In this study, four microcystin analogues were chlorinated in two treated waters, and two of the analogues were chlorinated in deionised water. The oxidation of the microcystins was related to the chlorine exposure (CT) of the sample waters with the ease of oxidation following the trend: microcystin-YR > microcystin-RR > microcystin-LR > or = microcystin-LA. This trend was in agreement with published data on model compounds and free amino acids. Values of CT of up to 25 mg min L(-1) were required for oxidation of all microcystin analogues to below the World Health Organization guideline value of 1.0 microg L(-1). Results from this study indicate that for some water resources it is important to determine the speciation of the microcystin analogues to optimise chlorination practices.     

Dynamics of microcystin production and quantification of potentially toxigenic Microcystis sp. using real-time PCR

Cyanobacterial blooms in eutrophied water body are generally composed of various genotypes with or without microcystin-producing genes (mcy gene cluster). Thus there is a need for quantification of potent toxin producing strains. The present study aimed at identifying microcystin variants and its producer strains in Durgakund pond, Varanasi, India, based on quantification of cpcBA-IGS and mcyA (condensation domain) genes using real-time PCR and LC-MS. Increase in microcystin concentrations was correlated with increase in mcyA copy number and the level of pigments (chlorophyll a, phycocyanin and carotenoids). Also, selected environmental factors (water temperature, light irradiance, rainfall, pH, N and P) and the concentration of microcystin variants (MC-LR, -RR and -YR) were also assessed in samples during May 2010 to April 2011 to establish the possible correlation among these parameters. Nutrients favored cyanobacterial bloom but it could not be correlated with the levels of microcystin variants and seemed to be geographically specific. Microcystis sp. dominant in the pond comprised potentially toxigenic cells. The ratio of potentially toxigenic Microcystis sp. to that of total Microcystis sp. ranged from 0% to 14%. Such studies paved the way to identify and quantify the most potent microcystin producer in the tropical aquatic body.     

Arsenic speciation study in some spring waters of Guam, Western Pacific Ocean

A survey of the different forms of arsenic species: inorganic arsenic (As), As(III), As(V) and organic As(III) and (V) was carried out on spring waters located along Tumon Bay in Guam. The results show that total arsenic concentrations in the spring water samples ranged from <0.3-1.2 microg/L. Inorganic arsenate, As(V), appears to be the dominant species in the spring water samples tested. The concentrations are much lower than previously reported, probably due to a much more rigorous methodological approach and requires further investigations on the status of As contamination in groundwater on the island.     

Benthic cyanobacteria (Oscillatoriaceae) that produce microcystin-LR, isolated from four reservoirs in southern California

Cyanobacteria that produce the toxin microcystin have been isolated from many parts of the world. Most of these organisms are planktonic; however, we report on several microcystin-producing benthic filamentous cyanobacterial isolates from four drinking-water reservoirs in southern California (USA): Lake Mathews, Lake Skinner, Diamond Valley Lake (DVL), and Lake Perris. Some samples of benthic material from these reservoirs tested positive for microcystin by an ELISA tube assay, and all the positive samples had in common a green filamentous cyanobacterium 10-15microm in diameter. Seventeen unialgal strains of the organism were isolated and tested positive by ELISA, and 11 cultures of these strains were found to contain high concentrations of microcystin-LR (90-432microgL(-1)). The cultures were analyzed by protein phosphatase inhibition assay (PPIA) and HPLC with photodiode array detector (PDA) or liquid chromatography/mass spectrometry (LC/MS). Microcystin per unit carbon was determined for six cultures and ranged from 1.15 to 4.15microgmg(-1) C. Phylogenetic analysis of four cultures from Lake Skinner and DVL using cyanobacterial-specific PCR and sequencing of the partial 16S rRNA gene suggested the highest similarity to an unidentified cyanobacterium in the oscillatoriales, and to a Phormidium sp. Morphologically, some of the isolates were similar to Oscillatoria, and others resembled Lyngbya. The significance of these organisms lies in the relative scarcity of known toxin producers among freshwater benthic cyanobacteria, and also as a source of cell-bound microcystin in these reservoirs.     

Delayed influence of dam storage and discharge on the determination of seasonal proliferations of Microcystis aeruginosa and Stephanodiscus hantzschii in a regulated river system of the lower Nakdong River (South Korea)

This study presents the relationship between the dam hydrology and phytoplankton proliferations in a regulated river system in East Asia. A long-term ecological study reveals that multi-purpose dam regulation on river flow in the Nakdong River (South Korea) affects proliferating patterns of phytoplankton, especially during summer (June-August) and winter (December-next February) as Microcystis aeruginosa and Stephanodiscus hantzschii, respectively, dominate each season by over 80%. Eutrophication was observed in the lower Nakdong River (South Korea) (mean+/-standard deviation: nitrate-N, 2.8+/-0.9 mg L(-1); phosphate-P, 40.3+/-31.3 microg L(-1); chlorophyll a, 45.2+/-84.9 microg L(-1); n=449), and the limnological characteristics responded to climatic variations such as monsoon and summer typhoons. The river basin experiences concentrated rainfall during the rainy season (June-September, over ca. 60% of total annual rainfall). Correlation and cross-correlation for time-delayed relationship revealed the hydrological environments (i.e., quantity of dam storage and discharge) had significantly negative relationship with the population dynamics of the two bloom-forming species for up to the next 2 years. S. hantzschii had clearer relationship with dam storage and discharge, which might be due to the seasonality exhibited by the species. The results support the necessity of "smart flow control" which may enable destruction of bloom formation by the two species with an adequate pulse of discharge generated by upstream dams in the far-east Asian river systems. This would increase the efficiency of water resource management system.     

黄浦江源水中藻类和微囊藻毒素状况调查

对黄浦江源水中的藻类和微囊藻毒素-LR和-RR的含量进行了检测,结果表明:黄浦江源水中的微囊藻毒素浓度和藻类数目相对较低,藻类数目为(30~700)×104个/L,总MC-LR浓度为100~250 ng/L,总MC-RR浓度为450~650 ng/L;黄浦江源水中的MC-RR浓度比MC-LR浓度高两倍左右,总MC-RR浓度最高为650 ng/L,总MC-LR浓度最高为250 ng/L;受黄浦江水力和环境条件的影响,藻类在河道内大量死亡、裂解导致黄浦江源水中溶解性微囊藻毒素与总微囊藻毒素浓度的比值比一般源水的高很多。     

Trace metal concentrations in water,sediments and fish tissue from Lake Tanganyika

Trace metal (Cu, Pb, Fe, Mn, Zn, Cd) concentrations were determined in water, sediments, various fin fish species and a bivalve (Mutela spekei) from Lake Tanganyika using an atomic absorption spectrophotometer. Integrated water samples to depths of 10 m were collected using a pre-rinsed flexible plastic pipe. Sediment samples were collected using a ponar mud sampler. Fish samples were obtained using a variety of fishing techniques. No differences in trace metal concentrations were observed in both inshore and offshore waters. Levels in inshore sediments were much higher than for the offshore ones. Sediment input through run-off may have been the cause for the differences. However, the levels were much lower than those reported for Lake Malawi sediments. The concentrations in the fish tissue were within ranges reported elsewhere for Lake Tanganyika fish species. The centrapomid Lates stappersii and the clupeids Limnothrissa miodon and Stolothrissa tanganicae are the most important commercial species in the lake followed by Lates marie. Lead and cadmium are of concern to human health. The mean concentrations of the two metals in the commercial fish species were as follows: L. stappersii (5.03 microg Pb/g, 0.28 microg Cd/g); L. marie (4.96 microg Pb/g, 0.25 microg Cd/g); L. miodon (4.64 microg Pb, 0.38 microg Cd); and S. tanganicae (4.96 microg Pb/g, 0.39 microg Cd/g). Levels of lead and iron in the bivalve species were exceptionally very high, being 11.08 and 6.54 mg/g, respectively.     

Simultaneous speciation of inorganic selenium and antimony in water samples by electrothermal vaporization inductively coupled plasma mass spectrometry following selective cloud point extraction

A new method was developed for the simultaneous speciation of inorganic selenium and antimony in water by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) following selective cloud point extraction (CPE). The method is based on the fact that Se(IV) and Sb(III) could form complexes with diethyldithiocarbamate (DDTC) at pH 6.00, and the complexes were quantitatively extracted into the non-ionic surfactant-rich phase of octylphenoxypolyethoxyethanol (Triton X-114), whereas the Se(VI) and Sb(V) remained as free species in aqueous solutions. Sb(III) and Se(IV) in concentrate were determined by ETV-ICP-MS after proper disposal. The total Se and total Sb were determined by the same protocol after Se(VI) and Sb(V) were reduced by l-cysteine, and Se(VI) and Sb(V) concentrations were obtained by respectively subtracting Se(IV) and Sb(III) from the total Se and the total Sb. Under the optimized conditions, the limits of detection (LODs) were 0.05 microg L(-1) for Se(IV) and 0.03 microg L(-1) for Sb(III), the relative standard deviations (RSDs) were 3.5% for Se(IV) and 4.2% for Sb(III) (C=1.00 microg L(-1), n=5). The proposed method was applied to the speciation of inorganic selenium and antimony in different water samples with satisfactory results.     

Mercury contaminations from historic mining to water, soil and vegetation in Lanmuchang, Guizhou, southwestern China

Concentrations of total mercury and methylmercury (MeHg) were measured in soil and vegetation samples collected from a small area with a long history of Hg-mining. Hg distributions were determined in stream-waters during two sampling periods. Total Hg concentrations in soil and vegetation samples were highly elevated ranging from 0.41 to 610 mg kg(-1) and from 0.02 to 55 mg kg(-1), respectively. MeHg concentrations varied from 0.41 to 8.8 microg kg(-1) in soil samples and from 0.65 to 5.5 microg kg(-1) in vegetations. The concentrations of total Hg in stream waters varied from 55.0 to 7020 ng L(-1) in the flood-flow regime and from 24.8 to 679 ng L(-1) in the base-flow regime, respectively. Average dissolved Hg concentration was 15.7 ng L(-1) in the wet season and 21.0 ng L(-1) in the dry season. However, particulate Hg was typically >70% of total Hg in the flood-flow regime. Higher concentrations of particulate Hg primarily originated from summer floods were the major pathway of Hg transportation, which were evidenced by the positive correlation between particulate Hg and total suspended solids (TSS). The contaminated soils and distribution patterns of Hg in the stream-waters may serve as an important source of Hg to the local environment in the study area.