Nitrate content and potential microbial signature of rock glacier outflow,Colorado Front Range

Here we characterize the nutrient content in the outflow of the Green Lake 5 rock glacier, located in the Green Lakes Valley of the Colorado Front Range. Dissolved organic carbon (DOC) was present in all samples with a mean concentration of 0·85 mg L^?1 . A one‐way analysis of variance test shows no statistical difference in DOC amounts among surface waters (p = 0·42). Average nitrate concentrations were 69 µmoles L^?1 in the outflow of the rock glacier, compared to 7 µmoles L^?1 in snow and 25 µmoles L^?1 in rain. Nitrate concentrations from the rock glacier generally increased with time, with maximum concentrations of 135 µmoles L^?1 in October, among the highest nitrate concentrations reported for high‐elevation surface waters. These high nitrate concentrations appear to be characteristic of rock glacier outflow in the Rocky Mountains, as a paired‐difference t‐test shows that nitrate concentrations from the outflow of 7 additional rock glaciers were significantly greater compared to their reference streams (p = 0·003). End‐member mixing analysis suggest that snow was the dominant source of nitrate in June, ‘soil’ solution was the dominant nitrate source in July, and base flow was the dominant source in September. Fluoresence index values and PARAFAC analyses of dissolved organic matter (DOM) are also consistent with a switch from terrestrial DOM in the summer time period to an increasing aquatic‐like microbial source during the autumn months. Copyright © 2006 John Wiley & Sons, Ltd.     

SO2 Emission from Active Volcanoes Measured Simultaneously by COSPEC and mini-DOAS

We measured SO₂ emission rate from six volcanoes in Latin America (Santa Ana, El Salvador; San Cristóbal and Masaya, Nicaragua; Arenal and Poás, Costa Rica; Tungurahua and Sierra Negra, Ecuador) and from Mt. Etna, Italy, using two different remote sensing techniques: COSPEC (COrrelation SPECtrometer) and miniDOAS (miniaturized Differential Optical Absorption Spectroscopy). One of the goals of this study was to evaluate the differences in SO₂ emission rates obtained by these two methods. The observed average SO₂ emission rates measured during this study were 2688 t·d⁻¹ from Tungurahua in July 2006, 2375 t·d⁻¹ in September 2005 and 480 t·d⁻¹ in February 2006 from Santa Ana, 1200 t·d⁻¹ in May 2005 from Etna, 955 t·d⁻¹ in March 2006 and 1165 t·d⁻¹ in December 2006 from Masaya, 5400 t·d⁻¹ of March 7, 2006 and 265 t·d⁻¹ in March 2006 from San Cristobal, 113 t·d⁻¹ in April 2006 from Arenal, 104 t·d⁻¹ in April 2006 from Poás and 11 t·d⁻¹ in July 2006 from Sierra Negra volcano. Most of the observed relative differences of SO₂ emission measurements from COSPEC and miniDOAS were lower than 10%.     

Uncertainty analysis of CO<Subscript>2</Subscript> flux components in subtropical evergreen coniferous plantation

We present an uncertainty analysis of ecological process parameters and CO₂ flux components (R _eco, NEE and gross ecosystem exchange (GEE)) derived from 3 years’ continuous eddy covariance measurements of CO₂ fluxes at subtropical evergreen coniferous plantation, Qianyanzhou of ChinaFlux. Daily-differencing approach was used to analyze the random error of CO₂ fluxes measurements and bootstrapping method was used to quantify the uncertainties of three CO₂ flux components. In addition, we evaluated different models and optimization methods in influencing estimation of key parameters and CO₂ flux components. The results show that: (1) Random flux error more closely follows a double-exponential (Laplace), rather than a normal (Gaussian) distribution. (2) Different optimization methods result in different estimates of model parameters. Uncertainties of parameters estimated by the maximum likelihood estimation (MLE) are lower than those derived from ordinary least square method (OLS). (3) The differences between simulated R_eco, NEE and GEE derived from MLE and those derived from OLS are 12.18% (176 g C·m⁻²·a⁻¹), 34.33% (79 g C·m⁻²·a⁻¹) and 5.4% (92 g C·m⁻²·a⁻¹). However, for a given parameter optimization method, a temperature-dependent model (T_model) and the models derived from a temperature and water-dependent model (TW_model) are 1.31% (17.8 g C·m⁻²·a⁻¹), 2.1% (5.7 g C·m⁻²·a⁻¹), and 0.26% (4.3 g C·m⁻²·a⁻¹), respectively, which suggested that the optimization methods are more important than the ecological models in influencing uncertainty in estimated carbon fluxes. (4) The relative uncertainty of CO₂ flux derived from OLS is higher than that from MLE, and the uncertainty is related to timescale, that is, the larger the timescale, the smaller the uncertainty. The relative uncertainties of R_eco, NEE and GEE are 4%−8%, 7%−22% and 2%−4% respectively at annual timescale. Supported by the National Natural Science Foundation of China (Grant No. 30570347), Innovative Research International Partnership Project of the Chinese Academy of Sciences (Grant No. CXTD-Z2005-1) and National Basic Research Program of China (Grant No. 2002CB412502)     

Observation and modeling of NPP for Pinus elliottii plantation in subtropical China

Based on the stem analysis of 59 individuals of Pinus elliottii in combination with tree biomass models, we calculated annual biomass increment of forest plots at Qianyanzhou Ecological Station, Chinese Academy of Sciences in subtropical China. In addition, canopy layer and community NPP were calculated based on 12 years’ litter fall data. NPP of the 21-year-old forest was estimated by using the BIOME BGC model; and both measured NPP and estimated NPP were compared with flux data. Community biomass was 10574 g · m⁻²; its distribution patterns in tree layer, shrub layer, herbaceous layer, tree root, herbaceous and shrub roots and fine roots were 7542, 480, 239, 1810, 230, 274 and 239 g · m⁻², respectively. From 1999 to 2004, the average annual growth rate and litter fall were 741 g · m⁻² · a⁻¹ (381.31 gC · m⁻² · a⁻¹) and 849 g · m⁻² · a⁻¹ (463 gC · m⁻² · a⁻¹), respectively. There was a significant correlation between annual litter fall and annual biomass increment; and the litter fall was 1.19 times the biomass increment of living trees. From 1985 to 2005, average NPP and GPP values based on BGC modeling were 630.88 (343.31–906.42 gC · m⁻² · a⁻¹) and 1 800 gC · m⁻² · a⁻¹ (1351.62–2318.26 gC · m⁻² · a⁻¹). Regression analysis showed a linear relationship (R ²=0.48) between the measured and simulated tree layer NPP values. NPP accounted for 30.2% (25.6%–32.9%) of GPP, while NEP accounted for 57.5% (48.1%–66.5%) of tree-layer NPP and 41.74% (37%–52%) of stand NPP. Soil respiration accounted for 77.0% of measured tree NPP and 55.9% of the measured stand NPP. NEE based on eddy covariance method was 12.97% higher than the observed NEP. Supported by the National Key Basic Research Special Foundation of China (Grant No. 2002CB4125), International Joint Research Project under Ministry of Science and Technology of China (Grant No. 2006DFB91920)     

Sedimentation rates in the central lake constance determined with210Pb and137Cs

Sediment cores from central Lake Constance were dated with²¹⁰Pb and¹³⁷Cs. A sedimentation rate of (0.11±0.02) g·cm⁻²·y⁻¹ was determined with the²¹⁰Pb method.¹³⁷Cs measurements revealed sedimentation rates of (0.11±0.01) g·cm⁻²·y⁻¹ and (0.08±0.01) g·cm⁻²·y⁻¹ respectively for two different cores sampled at the same location. The lower Cs-dated value indicates incomplete core recovery and demonstrates the sensitivity of this simple dating method to small losses of material at the water/sediment interface. An unambiguous application of the¹³⁷Cs method is, therefore, only possible if complete core recovery is ensured. Sedimentation rates based on particulate matter, collected in sediment traps at various water depths, agree with the results of the radioisotope methods. Estimates of 30–125 days residence times for suspended particulate matter were calculated from⁷Be measurements.     

Belowground carbon balance and carbon accumulation rate in the successional series of monsoon evergreen broad-leaved forest

The belowground part of terrestrial ecosystem is a huge carbon pool. It is believed that of the total 2500Gt carbon stored in global terrestrial ecosystem, soil carbon storage within the 1 m surface layer ac- counts for 2000Gt, which is 4-fold of vegetation car- bon storage[1,2]. Compared with the carbon in the vegetation, carbon in the deep soil layers is much more stable, and it will stay in soil profile permanentlyunless geological vicissitude occurs. Essentially, forest restoration is the…     

He,Ne and Ar isotopic composition of Fe-Mn crusts from the western and central Pacific Ocean and implications for their genesis

The noble gas nuclide abundances and isotopic ratios of the upmost layer of Fe-Mn crusts from the western and central Pacific Ocean have been determined. The results indicate that the He and Ar nu- clide abundances and isotopic ratios can be classified into two types: low 3He/4He type and high 3He/4He type. The low 3He/4He type is characterized by high 4He abundances of 191×10-9 cm3·STP·g-1 on average, with variable 4He, 20Ne and 40Ar abundances in the range (42.8―421)×10-9 cm3·STP·g-1, (5.40―141)×10-9 cm3·STP·g-1, and (773―10976)×10-9 cm3·STP·g-1, respectively. The high 3He/4He samples are characterized by low 4He abundances of 11.7×10-9 cm3·STP·g-1 on average, with 4He, 20Ne and 40Ar abundances in the range of (7.57―17.4)×10-9 cm3·STP·g-1, (10.4―25.5)×10-9 cm3·STP·g-1 and (5354―9050)×10-9 cm3·STP·g-1, respectively. The low 3He/4He samples have 3He/4He ratios (with R/RA ratios of 2.04―2.92) which are lower than those of MORB (R/RA=8±1) and 40Ar/36Ar ratios (447―543) which are higher than those of air (295.5). The high 3He/4He samples have 3He/4He ratios (with R/RA ratios of 10.4―12.0) slightly higher than those of MORB (R/RA=8±1) and 40Ar/36Ar ratios (293―299) very similar to those of air (295.5). The Ne isotopic ratios (20Ne/22Ne and 21Ne/22Ne ratios of 10.3―10.9 and 0.02774―0.03039, respectively) and the 38Ar/36Ar ratios (0.1886―0.1963) have narrow ranges which are very similar to those of air (the 20Ne/22Ne, 21Ne/22Ne, 38Ar/36Ar ratios of 9.80, 0.029 and 0.187, respectively), and cannot be differentiated into different groups. The noble gas nuclide abundances and isotopic ratios, together with their regional variability, suggest that the noble gases in the Fe-Mn crusts originate primarily from the lower mantle. The low 3He/4He type and high 3He/4He type samples have noble gas characteristics similar to those of HIMU (High U/Pb Mantle)- and EM (Enriched Mantle)-type mantle material, respectively. The low 3He/4He type samples with HIMU-type noble gas isotopic ratios occur in the Magellan Seamounts, Marcus-Wake Seamounts, Marshall Island Chain and the Mid-Pacific Sea- mounts whereas the high 3He/4He type samples with EM-type noble gas isotopic ratios occur in the Line Island Chain. This difference in noble gas characteristics of these crust types implies that the MagellanSeamounts, Marcus-Wake Seamounts, Marshall Is- land Chain, and the Mid-Pacific Seamounts originated from HIMU-type lower mantle material whereas the Line Island Chain originated from EM-type lower mantle material. This finding is consistent with varia- tions in the Pb-isotope and trace element signatures in the seamount lavas. Differences in the mantlesource may therefore be responsible for variations in the noble gas abundances and isotopic ratios in the Fe-Mn crusts. Mantle degassing appears to be the principal factor controlling noble gas isotopic abundances in Fe-Mn crusts. Decay of radioactive isotopes has a negligible influence on the nuclide abundances and isotopic ratios of noble gases in these crusts on the timescale of their formation.     

Variations of <Emphasis Type="Italic">δ</Emphasis><Superscript>18</Superscript>O in precipitation from the Muztagata Glacier,East Pamirs

Expeditions to Muztagata (in the eastern Pamirs) during the summer seasons of 2002 and 2003 collected precipitation samples and measured their oxygen isotopes. The δ ¹⁸O in precipitation displays a wide range, varying from −17.40‰ to +1.33‰ in June-September 2002 and from −22.31‰ to +4.59‰ in May-August 2003. The δ ¹⁸O in precipitation correlates with the initial temperature of precipitation during the observing periods. The positive correlation between δ ¹⁸O and temperature suggests that δ ¹⁸O can be used as an indicator of temperature in this region. The δ ¹⁸O values in fresh-snow samples collected from two snow events at different elevations on the Muztagata Glacier show a strong “altitude effect”, with a ratio of nearly −0.40% per 100 m from 5500 m to 7450 m.     

Relating snow dynamics and balsam fir stand characteristics,Montmorency Forest,Quebec

Snow water equivalent was measured during three springs on north‐ and south‐exposed sites representing a range of stand structure and development stages of Quebec's balsam fir forest. Maximum snow water equivalent of the season, mean seasonal snowmelt rate, snowmelt season duration and total snowmelt season degree‐day factor were related to canopy height, canopy density, light interception fraction and basal area of the stands using random coefficient models. Seasonal mean snowmelt rate was better explained by stand characteristics (R² from 0·41 to 0·61) than was maximum snow water equivalent (R² from 0·08 to 0·23). The best relationship was found with light interception, which explained 61% of snowmelt rate variability between stands. These relationships were not significantly affected by stand aspect (Pr ≥ S = 0·14 or higher), as snow dynamics seemed less dependent on aspect than on stand characteristics. Snowmelt recovery rates could be used by forest planners to establish an acceptable time step for the harvesting of different parts of a watershed in order to prevent peak flow augmentations. Copyright © 2005 John Wiley & Sons, Ltd.     

Gravitational effect of water circulation in the northwest Yunnan

ＧｒａｖｉｔａｔｉｏｎａｌｅｆｆｅｃｔｏｆｗａｔｅｒｃｉｒｃｕｌａｔｉｏｎｉｎｔｈｅｎｏｒｔｈｗｅｓｔＹｕｎｎａｎＭｉｎ－ＹｕＪＩＡ；（贾民育）Ｓｈａｏ－ＡｎＳＵＮ；（孙少安）Ａｉ－ＭｉｎＸＩＡＮＧ；（项爱民）ａｎｄＤｏｎｇ－ＺｈｉＬＩＵ（刘冬至）（...     

Artificially triggered lightning and its characteristic discharge parameters in two severe thunderstorms

The lightning-induced-damages in the mid-latitude regions are usually caused during severe thunder-storms. But the discharge parameters of natural lightning are difficult to be measured. Five lightning flashes have been artificially triggered with the rocket-wire technique during the passage of two severe thunderstorms. The discharge current and close electric field of return stroke in artificially triggered lightning have been obtained in microsecond time resolution by using current measuring systems and electric field change sensors. The results show that the five triggered lightning flashes include 1 to 10 return strokes, and the average return stroke current is 11.9 kA with a maximum of 21.0 kA and a mini-mum of 6.6 kA, similar to the subsequent return strokes in natural lightning. The half peak width of the current waveform is 39 μs, which is much larger than the usual result. The peak current of stroke Ip (kA) and the neutralized charge Q(C) has a relationship of Ip = 18.5Q0.65. The radiation field of return stroke is 5.9 kV·m-1 and 0.39 kV·m-1 at 60 m and 550 m, respectively. The radiation field decreases as r -1.119 with increase of horizontal distance r from the discharge channel. Based on the well-accepted transmission line model, the speed of return stroke is estimated to be about 1.4×108 m·s-1, with a variation range of (1.1―1.6)×108 m·s-1. Because of the similarities of the triggered lightning and natural lightning, the results in this article can be used in the protection design of natural lightning.     

Application of <Superscript>137</Superscript>Cs fingerprinting technique to interpreting sediment production records from reservoir deposits in a small catchment of the Hilly Loess Plateau,China

According to variations of 137Cs and clay contents, 44 flood couplets were identified in a profile of reservoir deposit with a vertical length of 28.12 m in the Yuntaishan Gully. Couplet 27 at the middle of the profile had the highest average 137Cs content of 12.65 Bq kg-1, which indicated the 1963s' deposits, then 137Cs content decreased both downward and upward in the profile. The second top and bottom couplets had average 137Cs contents of 2.15 Bq kg-1 and 0.92 Bq kg-1, respectively. By integrated analysis of reservoir construction and management history, variations of 137Cs contents over the profile, sediment yields of flood couplets and rainfall data during the period of 1958-1970, individual storms related to the flood couplets were identified. 44 floods with a total sediment yield of 2.36×104 m3 occurred and flood events in a year varied between 1 and 10 times during the period of 1960-1970. 7-10 flood events occurred during the wet period of 1961-1964 with very wet autumn, while only 1-2 events during the dry period of 1965-1969. Average annual specific sediment yield was 1.29×104 t km-2 a-1 for the Yuntaishan Gully during the period of 1960-1970, which was slightly higher than 1.11 ×104 t km-2 a-1 for the Upper Yanhe River Basin above the Ganguyi Hydrological Station and slightly lower than 1.40 ×104 t km-2 a-1 for the nearby Zhifang Gully during the same period. Annual specific sediment yields for the Yuntaishan Gully were correlated to the wet season's rainfalls well.     

Denitrification in Chongming east tidal flat sediment, Yangtze estuary, China

From July 2003 to July 2004, samples were collected on Chongming Island east tidal flat every two months. The research showed that the nitrous oxide (N2O) production rate was very low in the water, Chongming east tidal flat (CM) sediment was the N2O source of the water. Sediment N2O natural production rate was between -0.08 and 1.74 μmolN·m-2·h-1. N2O natural production rate was higher in the summer. The difference of the N2O natural production rate in the different tidal flats, the correlation between the N2O natural production rate and the denitrification rate, and those with the temperature and DO indicate that middle tidal flat sediment denitrification was the main process of the N2O production, while in the low tidal flat sediment, the production of the N2O came from several processes of the nitrogen cycling. Tidal flat sediment denitrification reaction was stronger in summer and winter but relatively lower in the late autumn and early spring. Seasonal change of the sediment denitrification rate was wide, from 1.12 to 33.34 μmolN·m-2·h-1. Temperature, DO and the coactions of them had the prominent effect on the tidal flat sediment denitrification.     

Linkage of liquid conductivity of glacier ice with its alkalinity over the north Qinghai-Xizang (Tibet) Plateau

Liquid conductivity (EC) measurement was conducted for the samples collected from several snow pits and ice cores over the Qinghai-Xizang (Tibet) Plateau, with their time range covering seasonal, decadal and centennial scales. Unlike the previous attention mostly focused on the acidity (H⁺) responding to the solid conductance (ECM) of glacial ice, we introduce the alkalinity (OH⁻) of snow and ice to show how it responds to EC. Strong linear relationship was established between EC and OH⁻ for these snow pits and ice cores. Positive correlation is also established between EC and major cations (Ca²⁺, Mg²⁺, Na⁺ and K⁺). Since the cations are known as the proxies for the intensity of mineral dust influx onto glaciers of the northern Qinghai-Xizang Plateau, we believe that EC could be used as an indicator for the history of dust input in deep ice core study. In fact, records in Guliya ice core since the Little Ice Age (LIA) indicate that dust load in glacier may depend on the combination of temperature and humidity. “Cold-dry” combination favors the dust arising, and results in higher EC and OH⁻ values, while “warm-wet” combination prevents dust form and EC and OH⁻ values are lower. In the past century, with the atmospheric warming and precipitation increasing over the northern plateau, which means an atmospheric condition of dust decreasing, both EC and OH⁻ displayed rapid decline.     

Upper mantle P wave velocity structure of the northern part of China and Mongolia

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Role of bedrock groundwater in the rainfall–runoff process in a small headwater catchment underlain by volcanic rock

The role of bedrock groundwater in rainfall–runoff processes is poorly understood. Hydrometric, tracer and subsurface water potential observations were conducted to study the role of bedrock groundwater and subsurface flow in the rainfall–runoff process in a small headwater catchment in Shiranui, Kumamoto prefecture, south‐west Japan. The catchment bedrock consists of a strongly weathered, fractured andesite layer and a relatively fresh continuous layer. Major chemical constituents and stable isotopic ratios of δ¹⁸O and δD were analysed for spring water, rainwater, soil water and bedrock groundwater. Temporal and spatial variation in SiO₂ showed that stream flow under the base flow condition was maintained by bedrock groundwater. Time series of three components of the rainstorm hydrograph (rainwater, soil water and bedrock groundwater) separated by end member mixing analysis showed that each component fluctuated during rainstorm, and their patterns and magnitudes differed between events. During a typical mid‐magnitude storm event, a delayed secondary runoff peak with 1·0 l s⁻¹ was caused by increase in the bedrock groundwater component, whereas during a large rainstorm event the bedrock groundwater component increased to ≈ 2·5 l s⁻¹. This research shows that the contribution of bedrock groundwater and soil water depends strongly on the location of the groundwater table, i.e. whether or not it rises above the soil–bedrock interface. Copyright © 2010 John Wiley & Sons, Ltd.     

Analysis of the Microseismicity Induced by Fluid Injections at the EGS Site of Soultz-sous-Forêts (Alsace, France): Implications for the Characterization of the Geothermal Reservoir Properties

In June/July 2000, a hydraulic stimulation experiment took place at the geothermal EGS site of Soultz-sous-Forêts (Alsace, France) in order to enhance the permeability of the fractured granitic massif at 5 km depth. As it is well known that fluid injections tend to induce microseismic events, a downhole and a surface seismological network have been installed to monitor the seismic activity during the stimulation test. 23400 m³ of fluid have been injected in the rock volume through the open-hole section (4400 m–5000 m) of the well GPK2 at increasing rates of 30 l.s⁻¹, 40 l.s⁻¹ and then 50 l.s⁻¹. More than 7200 microseismic events in the magnitude range –0.9 to 2.6 have been precisely located through a simultaneous inversion of the seismic velocity structure and location parameters. The analysis of the behavior of the seismicity relative to the hydraulic parameters gives important information about the geothermal reservoir. It appears that the evolution of the seismicity strongly depends on the variations of the injection rate: An increase or a decrease leads to changes of the velocity structure, the number and magnitude of microseismic events. This involves different hydro-mechanical processes between the fluid flow and the fracture planes, which will control the final shape of the microseismic cloud. Moreover, the study of the variations of the b-value with time suggests that the stimulation experiment produces a large proportion of small earthquakes, but records of events of magnitude higher than 2 indicate that fluid injection could reactivate structures whose dimensions allow the generation of such earthquakes.     

Application of snowmelt runoff model for water resource management

Snow‐covered areas (SCAs) are the fundamental source of water for the hydrological cycle for some region. Accurate measurements of river discharge from snowmelt can help manage much needed water required for hydropower generation and irrigation purposes. This study aims to apply the snowmelt runoff model (SRM) in the Upper Indus basin by the Astore River in northern Pakistan for the years 2000 to 2006. The Shuttle Radar Topographic Mission (SRTM) data are used to generate the Digital Elevation Model (DEM) of the region. Various variables (snow cover depletion curves (SCDCs), temperature and precipitation) and parameters (degree‐day factor, recession coefficient, runoff coefficients, time lag, critical temperature and temperature lapse rate) are used as input in the SRM. However, snow cover data are direct and an important input to the SRM. Satellite data from the Moderate Resolution Imaging Spectroradiometer (MODIS) are used to estimate the SCA. Normalized difference snow index (NDSI) algorithm is applied for snow cover mapping and to differentiate snow from other land features. Nash–Sutcliffe coefficient of determination (R²) and volume difference (D_V) are used for quality assessment of the SRM. The results of the current research show that for the study years (2000–2006), the average value of R² is 0·87 and average volume difference D_V is 1·18%. The correlation coefficient between measured and computed runoff is 0·95. The results of the study further show that a high level of accuracy can be achieved during the snowmelt season. The simulation results endorse that the SRM in conjunction with MODIS snow cover product is very useful for water resource management in the Astore River and can be used for runoff forecasts in the Indus River basin in northern Pakistan. Copyright © 2011 John Wiley & Sons, Ltd.     

Nitrogen compounds in the surface and subsurface waters of Karelia

Materials of long-term studies of the concentration and distribution of N forms (NH₄⁺, NO₃⁻, NO₂⁻, N_org) in precipitation, surface water and groundwater are generalized. Precipitation was found to be the main source of N compounds input into these waters. The effect of anthropogenic factors is local and does not influence the concentration and distribution of N forms in most water bodies that serve as wastewater recipients. The N forms dominating in precipitation are NO₃⁻ and N H₄⁺; N_org dominates in most surface water bodies, and NO₃⁻ dominates in groundwater. The median concentrations of N_tot in clear surface and subsurface waters are similar. The obtained characteristics of the concentrations and distribution of N forms in natural waters of Karelia can be used for other water bodies in the humid zone.     

Risk-based assessment of arsenic-affected aquacultural water in blackfoot disease hyperendemic areas

This work explored a risk-based arsenic (As) regulation in farmed pond water by ingesting tilapia (Oreochromis mossambicus) in blackfoot disease hyperendemic areas and discussed a rational As regulation in pond water. Monte Carlo analysis was used to propagate the parameter uncertainty and to assess probabilistically regulation risks. A dynamic scheme of groundwater management was proposed that curves of utilization ratios against As concentrations in groundwater were established based on the risk-based regulation. The 5th to 95th percentiles of risks range from 3.5 × 10⁻⁷ to 6.0 × 10⁻⁵ via ingesting the farmed tilapia under the current As regulation in farmed pond water in Taiwan, 50 μg/L. To compare to inorganic As regulation in drinking water, the current As regulation in farmed pond water does not pose a great threat to human health, but it is unsafe. Therefore, this study suggests that the regulation of As in farmed pond water is revised to be 25 μg/L.