Improved mapping of National Atmospheric Deposition Program wet-deposition in complex terrain using PRISM-gridded data sets

High-elevation regions in the United States lack detailed atmospheric wet-deposition data. The National Atmospheric Deposition Program/National Trends Network (NADP/NTN) measures and reports precipitation amounts and chemical constituent concentration and deposition data for the United States on annual isopleth maps using inverse distance weighted (IDW) interpolation methods. This interpolation for unsampled areas does not account for topographic influences. Therefore, NADP/NTN isopleth maps lack detail and potentially underestimate wet deposition in high-elevation regions. The NADP/NTN wet-deposition maps may be improved using precipitation grids generated by other networks. The Parameter-elevation Regressions on Independent Slopes Model (PRISM) produces digital grids of precipitation estimates from many precipitation-monitoring networks and incorporates influences of topographical and geographical features. Because NADP/NTN ion concentrations do not vary with elevation as much as precipitation depths, PRISM is used with unadjusted NADP/NTN data in this paper to calculate ion wet deposition in complex terrain to yield more accurate and detailed isopleth deposition maps in complex terrain. PRISM precipitation estimates generally exceed NADP/NTN precipitation estimates for coastal and mountainous regions in the western United States. NADP/NTN precipitation estimates generally exceed PRISM precipitation estimates for leeward mountainous regions in Washington, Oregon, and Nevada, where abrupt changes in precipitation depths induced by topography are not depicted by IDW interpolation. PRISM-based deposition estimates for nitrate can exceed NADP/NTN estimates by more than 100% for mountainous regions in the western United States.     

A Comparison of the Precipitation Chemistry Measurements Obtained by the CAPMoN and NADP/NTN Networks

Precipitation chemistry measurementsobtained by the Canadian Air and PrecipitationMonitoring Network (CAPMoN) and the U.S. NationalAtmospheric Deposition Program/National Trends Network(NADP/NTN) have been examined using more than 7 yrof collocated data from two sites, namely, Sutton,Quebec, Canada and State College, Pennsylvania, U.S.A.In the case of the CAPMoN data, weeklyprecipitation-weighted mean concentrations, totalsample depths and total standard gauge depths werecomputed from daily data and compared to thecorresponding weekly sampling data of the NADP/NTNnetwork. Seasonal and annual precipitation-weightedmean concentrations and deposition values were alsocomputed for both networks and compared. Statisticallysignificant between-network biases were found to existin the weekly results for most of the measuredvariables, particularly standard gauge depth, sampledepth, pH, H⁺, NO₃ ^-,NH₄ ⁺,Na⁺; the NADP/NTN values were consistently lowerthan those of CAPMoN with the exception of pH andNa⁺. The magnitude of the biases was less than35% of the median CAPMoN weekly value for the 7 yr. For most of the measured parameters, thevariability of the between-network differencesrepresented less than 20% of the median CAPMoN weeklyvalue. Both the between-network biases andvariabilities were functions of several physicalparameters, the most dominant being the sample depthand the ionic concentration. For seasonal and annualdeposition values, statistically significantbetween-network biases were found for H⁺,SO₄ ^2-, NO₃ ^-,Ca²⁺,NH₄ ⁺ for both periods; for Mg²⁺ andK⁺ for seasonal data; and Cl^- for yearlydata, with the NADP/NTN deposition values being lowerthan those of CAPMoN. The relative biases ranged from7 to 37%. Part of the between-network bias in thedeposition estimates was directly attributable to astrong bias in the standard gauge depths of the two networks.     

Total Mercury Distribution in Different Tissues of Frigate Tuna (Auxis thazard thazard) from the Atlantic Coastal Waters of Ghana, Gulf of Guinea

Total mercury concentrations in different tissues of frigate tuna fish (Auxis thazard thazard) was determined by the cold vapour atomic absorption spectrometry technique using an automatic mercury analyzer. A mixture of HNO₃, HClO₄ and H₂SO₄ was used for complete oxidation of organic tissue. The concentration of mercury obtained was in the order Gills < Stomach < Gonads < Intestine < Heart < Duodenum < Liver < Muscle. The concentration of total mercury detected in the edible muscle tissue of the tuna fish tested ranged from 0.044 to 0.201 μg g⁻¹ (mean = 0.108 μg g⁻¹) wet weight. These levels are all within the maximum allowed/recommended level in fish (0.5 μg g⁻¹ wet weight) set by the Food and Agriculture Organisation/World Health Organisation (FAO/WHO) and are therefore unlikely to constitute any significant mercury exposure to the general population because of consumption of tuna fish. The results of the study suggest a relatively clean marine environment that has not been significantly impacted by mercury contamination probably due to minimal industrial activity in the region.     

Organochlorines and Mercury in Waterfowl Harvested in Canada

Samples of breast muscle from 32 species of waterfowl collected from 123 sites across Canada were analyzed for chlorobenzenes (CBz), chlordane-related compounds (CHL), hexachlorocyclohexanes (HCH), DDT, mirex, dieldrin, PCBs and mercury. ΣDDT, ΣCBz and ΣPCB were the compounds most frequently found above trace levels. ΣHCH and ΣMirex were detected the least often. Mercury was detected in all of the mergansers, over 50% of dabbling, bay and sea ducks, and in less than 2% of the geese analysed. The highest levels of contaminants were generally found in birds feeding at higher trophic levels such as sea ducks and mergansers. With the exception of a few samples of mergansers and long-tailed ducks from eastern Canada, which contained ΣPCB concentrations of 1.0–2.4 mg kg⁻¹, ΣPCB levels were less than 1 mg kg⁻¹ wet weight. Only one merganser from eastern Canada had a ΣDDT concentration (2.6 mg kg⁻¹ ww) which was greater than 1 mg kg⁻¹ ww. The highest ΣCHL (0.10 mg kg⁻¹ ww) was also found in mergansers from eastern Canada. Levels of total mercury in breast muscle were either low (< 1 mg kg⁻¹ ww) or below detection limits with the exception of a few samples of mergansers from eastern Canada which contained mercury concentrations of 1.0–1.5 mg kg⁻¹ ww. Health Canada determined that the organochlorine and mercury levels found in samples of breast muscle of ducks and geese analysed in this study did not pose a health hazard to human consumers and therefore these waterfowl were safe to eat.     

Mercury trends in fish from rivers and lakes in the United States, 1969�C2005

A national dataset on concentrations of mercury in fish, compiled mainly from state and federal monitoring programs, was used to evaluate trends in mercury (Hg) in fish from US rivers and lakes. Trends were analyzed on data aggregated by site and by state, using samples of the same fish species and tissue type, and using fish of similar lengths. Site-based trends were evaluated from 1969 to 2005, but focused on a subset of the data from 1969 to 1987. Data aggregated by state were used to evaluate trends in fish Hg concentrations from 1988 to 2005. In addition, the most recent Hg fish data (1996?C2005) were compared to wet Hg deposition data from the Mercury Deposition Network (MDN) over the same period. Downward trends in Hg concentrations in fish from data collected during 1969?C1987 exceeded upward trends by a ratio of 6 to 1. Declining Hg accumulation rates in sediment and peat cores reported by many studies during the 1970s and 1980s correspond with the period when the most downward trends in fish Hg concentrations occurred. Downward Hg trends in both sediment cores and fish were also consistent with the implementation of stricter regulatory controls of direct releases of Hg to the atmosphere and surface waters during the same period. The southeastern USA had more upward Hg trends in fish than other regions for both site and state aggregated data. Upward Hg trends in fish from the southeastern USA were associated with increases in wet deposition in the region and may be attributed to a greater influence of global atmospheric Hg emissions in the southeastern USA. No significant trends were found in 62% of the fish species from six states from 1996 to 2005. A lack of Hg trends in fish in the more recent data was consistent with the lack of trends in wet Hg deposition at MDN sites and with relatively constant global emissions during the same time period. Although few significant trends were observed in the more recent Hg concentrations in fish, it is anticipated that Hg concentrations in fish will respond to changes in atmospheric Hg deposition, however, the magnitude and timing of the response is uncertain.     

Enhanced Wet Deposition Estimates using Modeled Precipitation Inputs

Effective assessments of linkages between atmospheric deposition and sensitive aquatic and terrestrial ecosystems require a knowledge of spatial patterns in deposition of greater resolution than currently available using point estimates and two-dimensional surface algorithms. A high resolution wet deposition model was developed for the Eastern U.S.A. by incorporating daily precipitation measurements from National Oceanic and Atmospheric Administration (NOAA) monitoring sites located within the Eastern U.S.A.; topographic variables, including elevation, slope, and aspect that affect the amount and distribution of precipitation across the region; and precipitation chemistry data from National Atmospheric Deposition Program (NADP) sites within and adjacent to the region. Model performance, which was tested against independent measurements from three physiographic regions of the eastern U.S.A., revealed a statistically significant reduction in interpolation error compared to traditional two-dimensional surface algorithms.     

Characteristic Study of Dry Deposition, Concentration, Compositions for Particulates Mass and Ionic Species During Summer and Autumn Season at a Traffic Sampling Site

Aerosol samples for dry deposition and total suspend particulates (TSP) were collected from August to November of 2003 in central Taiwan. Ion chromatography was used to analyze the related water-soluble ionic species (Cl⁻, NO₃ ⁻, SO₄ ²⁻, Na⁺, NH₄ ⁺, K⁺, Mg²⁺ and Ca²⁺). The results obtained in this study indicated that the ambient air particulate mass concentrations in the daytime period (averaged 975.4 μg m⁻³) were higher than the nighttime period (averaged 542.1 μg m⁻³). And the daytime dry deposition fluxes (averaged 58.12 μg m⁻² sec⁻¹) were about 2.2 times as that of nighttime dry deposition fluxes (averaged 26.54 μg m⁻² sec⁻¹) of the downward dry deposition. The average values downward and upward of dry deposition fluxes for the weekend period were almost higher than the weekday period for either daytime or nighttime period. Furthermore, the average daytime dry deposition fluxes (averaged 26.37 μg m⁻² sec⁻¹) were also about 2.3 times as that of nighttime dry deposition fluxes (averaged 11.52 μg m⁻² sec⁻¹). Moreover, the results also indicate that SO₄ ²⁻ and Ca²⁺ have higher average composition for total suspended particulates in the daytime period while Ca²⁺, SO₄ ²⁻, and Na⁺ have the higher average composition for total suspends particulates in the nighttime period.     

Behaviour and Quantification Studies of Terbacil and Lenacil in Environmental Samples Using Cyclic and Adsorptive Stripping Voltammetry at Hanging Mercury Drop Electrode

The cyclic voltammograms of terbacil and lenacil at the hanging mercury drop electrode showed a single well defined four electron irreversible peak in universal buffer of pH 4.0 for both compounds. The peak potentials were shifted to more negative values on the increase of pH of the medium, implying the involvement of protons in the electrode reaction and that the proton transfer reaction precedes the proper electrode process. The four electron single peak may be attributed to the simultaneous reduction of carbonyl groups present in 2 and 4 in pyrimidine ring of terbacil and lenacil to the corresponding hydroxy derivative. Based on the interfacial adsorptive character of the terbacil and lenacil onto the mercury electrode surface, a simple sensitive and low cost differential pulse adsorptive stripping voltammetric procedure was optimized for the analysis of terbacil and lenacil. The optimal operational conditions of the proposed procedure were accumulation potential E _acc = −0.4 V, accumulation time t _acc = 80 s, scan rate = 40 mV s⁻¹, pulse amplitude = 25 mV using a universal buffer pH 4.0 as a supporting electrolyte. The linear concentration range was found to be 1.5 × 10⁻⁵ to 1.2 × 10⁻⁹ mol/l and 1.5 × 10⁻⁵ to 2.5 × 10⁻⁸ mol/l with the lower detection limit of 1.22 × 10⁻⁹ and 2.0 × 10⁻⁸ mol/l. The correlation coefficient and relative standard deviation values are found to be 0.942, 0.996, 1.64% and 1.23%, respectively, for 10 replicants. The procedure was successfully applied for determination of terbacil and lenacil in formulations, mixed formulations, environmental samples such as fruit samples and spiked water samples.     

Interactions of Atmospheric Deposition with Coniferous Canopies in Estonia

Throughfall and open field bulk precipitation were measured at three coniferous sites during 1995–2002 in the framework of ICP Integrated Monitoring and at five coniferous sites during 1996–2002 in the framework of ICP Forests (Level II). The coniferous canopies acted as a sink for nitrate and ammonium and as a source for base cations: Ca²⁺, Mg²⁺ and K⁺. The estimated share of SO₄–S dry deposition from total deposition was 1.5–4 times higher for dormant period compared to growing period. During the study period average annual throughfall and bulk deposition of SO₄–S decreased significantly, 2.8 and 2.3 times, respectively. Throughfall enrichment with base cations increased in the order Mg < Na < Ca < K. Using Na as a tracer ion, average dry deposition and canopy leaching were calculated. Leaching was the dominant process for TF enrichment by potassium. Leaching of base cations occurred during growing as well as dormant period. The calculated internal flux of Ca²⁺ and Mg²⁺ varied in the range of 0.6–2.0 and 0.6–1.2 kg ha⁻¹ per year in spruce and pine stands, respectively. The internal circulation of K⁺ was significantly higher (8.9–10.9 kg ha⁻¹ per year) in spruce stands than in pine stands (2.7–4.4 kg ha⁻¹ per year).     

Determination of Nitrobenzene in Wastewater Using a Hanging Mercury Drop Electrode

The determination of trace amount nitrobenzene in wastewater on a hanging mercury drop electrode was studied. The determination conditions of pH, supporting electrolyte, accumulation potential, accumulation time, and voltammetric response were optimized. The sharp peak of the nitrobenzene was appeared at 0.05 V. The peak electric current was proportional to the concentration of nitrobenzene in the range of 1.47 × 10⁻⁵ ∼ 1.0 × 10⁻³ mol/l with relative standard deviations of 3.99 ∼ 8.94%. The detection limit of the nitrobenzene in water was 5 × 10⁻⁶ mol/l. The proposed method offered low limit of determination, easy operation, the use of simple instrumentation, high sensitivity and good reproducibility. It was applied to the determination of nitrobenzene in wastewater with an average recovery of 94.0% ∼ 105%. The proposed method provided fast, sensitive and sometimes real time detection of nitrobenzene.     

Atmospheric deposition of major and trace elements in Amman, Jordan

Wet and dry deposition samples were collected in the capital of Jordan, Amman. Concentrations of Al, Ba, Bi, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, V, Zn, Fe, Sr, Mg²⁺, Ca²⁺, Na⁺, K⁺, Cl⁻, NO₃ ⁻ and SO₄ ²⁻, along with pH were determined in collected samples. Mean trace metal concentrations were similar or less than those reported for other urban regions worldwide, while concentrations of Ca²⁺ and SO₄ ²⁻ were among the highest. High Ca²⁺ concentrations were attributed to the calcareous nature of the local soil and to the influence of the Saharan dust. However, high SO₄ ²⁻ concentrations were attributed to the influence of both anthropogenic and natural sources. Except for Cl⁻, NO₃ ⁻, SO₄ ²⁻ and Cu, monthly dry deposition fluxes of all measured species were higher than wet deposition fluxes. The annual wet deposition fluxes of trace metals were much lower than those reported for other urban areas worldwide.     

Deposition in boreal forests in relation to type, size, number and placement of collectors

Open precipitation and throughfall was collected at a Norway spruce stand in Finland using funnel-type collectors and at a black spruce stand in Canada using trough-type collectors. The presence or absence of a rim on the funnel, funnel diameter (9, 14 and 20 cm) and length of sampling period (1, 2 and 4 weeks) on monthly values were evaluated at the Norway spruce stand, and the number of collectors required for defined levels of accuracy and precision of throughfall loads to be reached and the influence of the spatial arrangement of collectors on solute concentrations was studied at both stands. The presence of a rim had no significant effect on open precipitation and throughfall amounts, but did on throughfall DOC, Ca²⁺, Mg²⁺, K⁺, Na⁺ and Cl⁻ ion loads. Deposition loads increased with decreasing funnel diameter; for open precipitation, this was due to increased catch efficiency while for throughfall the increase was attributed to canopy interaction and leaching of litter trapped in the collectors. Calculated monthly H⁺ loads decreased and those for all other constituents increased with collection period length. Using 15 collectors at the Norway spruce stand would allow throughfall loads to be determined to within 20% of the true mean weekly value with a confidence level of 95% for most solute, but not for NH₄ ⁺–N, NO₃ ⁻–N, Mg²⁺ and SO₄ ²⁻-S. Using 15 trough collectors, the same confidence level at the more heterogeneous black spruce stand would only be achieved for H⁺, Cl⁻, DOC and SO₄ ²⁻-S loads. In both stands, using either random or systematic placements of throughfall collectors gave similar results.     

Controls on Mercury and Methylmercury Deposition for Two Watersheds in Acadia National Park, Maine

Throughfall and bulk precipitation samples were collected for two watersheds at Acadia National Park, Maine, from 3 May to 16 November 2000, to determine which landscape factors affected mercury (Hg) deposition. One of these watersheds, Cadillac Brook, burned in 1947, providing a natural experimental design to study the effects of forest type on deposition to forested watersheds. Sites that face southwest received the highest Hg deposition, which may be due to the interception of cross-continental movement of contaminated air masses. Sites covered with softwood vegetation also received higher Hg deposition than other vegetation types because of the higher scavenging efficiency of the canopy structure. Methyl mercury (MeHg) deposition was not affected by these factors. Hg deposition, as bulk precipitation and throughfall was lower in Cadillac Brook watershed (burned) than in Hadlock Brook watershed (unburned) because of vegetation type and watershed aspect. Hg and MeHg inputs were weighted by season and vegetation type because these two factors had the most influence on deposition. Hg volatilization was not determined. The total Hg deposition via throughfall and bulk precipitation was 9.4 μg/m²/year in Cadillac Brook watershed and 10.2 μg/m²/year in Hadlock Brook watershed. The total MeHg deposition via throughfall and bulk precipitation was 0.05 μg/m²/year in Cadillac Brook watershed and 0.10 μg/m²/year in Hadlock Brook watershed.     

Estimation Of Selenium Concentration In Shallow Groundwater In Alluvial Fan Area In Tsukui, Central Japan

Total selenium (Se) and water-soluble Se in soil, and Se in a shallow groundwater were hydrogeochemically researched in an alluvial fan area in Tsukui, Central Japan. The water-soluble Se was estimated at average level of 2.6 ± 1.2μg Se kg⁻¹ dry soil (± SD, n = 25), showing less than 1% of the total Se (349–508μg Se kg⁻¹ dry soil) in soil. The monthly Se concentration in groundwater was average 2.2μg,L⁻¹, ranging 1.6–2.4μg,L⁻¹ during 2001–2003. The Se in groundwater significantly decreased with increasing groundwater level after rainfall. This result indicated that Se-bearing water percolated with relatively low Se concentration through the soil layer. According to our prediction model of linear regression curve on the observation data, Se concentration in the groundwater was estimated to be increasing with the very low rate of 4.35 × 10⁻³μg Se L⁻¹,yr⁻¹. The hydrogeochemical research and the result of the prediction model showed that any explosive increase of Se will hardly occur in this groundwater without an anthropogenic Se contamination.     

Spatial variability of soil <Superscript>137</Superscript>Cs in the South Caspian region

In a comprehensive program of environmental radioactivity survey in South Caspian region,¹³⁷Cs inventories in soil has been measured at more than 50 sites in the Iranian northern province of Guilan. This has been the first wide-range survey of soil radionuclide inventories in the narrow band sensitive ecosystem of south Caspian shore. Radioactivity measurements were carried out using HPGe gamma-spectrometry system. The activity concentration of ¹³⁷Cs in surface soil exhibits a mean value of 17.6 ± 9.4 Bq kg⁻¹, with a range of 2.3–41.7 Bq kg⁻¹. In many sites, split-level sampling method has been applied down to a depth of 20 cm. There were found generally two profiles. Most profiles exhibit a negative exponential distribution, while others revealed a clear subsurface peak in 5–10-cm layer. Cesium deposition in the study area has been estimated to be in the range of 0.38–2.9 kBq m⁻² with a mean value of 1.7 kBq m⁻². Distribution patterns of ¹³⁷Cs concentration levels and deposition values have been estimated using Kriging interpolation method. Observed hotspots in deposition pattern coincide with areas of higher precipitation.     

Accumulation and tolerance characteristics of cadmium in Chlorophytum comosum: a popular ornamental plant and potential Cd hyperaccumulator

The effects on the growth, physiological indexes and the cadmium (Cd) accumulation in Chlorophytum comosum under Cd stress were examined by pot-planting. The results showed that the tolerance index (TI) of C. comosum were all above 100 in soil Cd concentration of 100 mg kg − 1. The O2·-_{2^{\bullet}}^{-} production rate and electrical conductivity of C. comosum were significantly positively correlated to Cd adding-concentration while the MDA content increased and had significant differences with the control. The activities of SOD, CAT, and POD all rose significantly in lower Cd concentration and the Cd threshold of them were around 10, 50 and 20 mg kg − 1, respectively. The Cd in C. comosum root and aboveground part reached 1,522 and 865·5 mg kg − 1, respectively, in Cd concentration of soil up to 200 mg kg − 1. For the advantages of high tolerance, high accumulation, and high ornamental value, C. comosum may have tremendous application value in the treatment of Cd-contaminated soils.     

Concentrations of cadmium and lead heavy metals in Dardanelles seawater

Cadmium and lead were determined simultaneously in seawater by differential pulse stripping voltammetry (DPSV) preceded by adsoptive collection of complexes with 8-hydroxyquinoline (oxine) on to a hanging mercury drop electrode (HMDE). In preliminary experiments the optimal analytical condition for oxine concentration was found to be 2.10⁻⁵ M, at pH 7.7, the accumulation potential was −1.1 V, and the initial scannig potential was −0.8 V. The peak potentials were found −0.652 V for Cd and −0.463 V for Pb At the 60 s accumalation time. The limit of detection (LOD) and limit of quantitatification (LOQ) were found to be by voltammetry as 0.588 and 1.959 μg l⁻¹ (RSD, 5.50%) for Cd and 0.931 and 3.104 μg l⁻¹ (RSD, 4.10%) for Pb at 60 s stirred accumulation time respectively. In these conditions the most of the seawater samples are amenable for direct voltammetric determination of cadmium and lead using a HMDE. An adsorptive stripping mechanism of the electrode reaction was proposed. For the comparison, seawater samples were also analysed by ICP-atomic emission spectrometry method (ICP-AES). The applied voltammetric technique was validated and good recoveries were obtained.     

Appropriate Range of Quality Control Limit for Wet Deposition Monitoring

Precipitation chemistry programs in different regions of the world have different quality control limits for ion balance parameter IPD in wet deposition monitoring (R). The range of R values was calculated by assuming sample rainwater models in this paper. It was found that R was influenced by the inorganic ion types, total ion concentrations (IS) and the accuracy of the measurements (a _i ). R was defined and calculated as a function of a _i and ion concentration C _i . R values of different types of wet deposition (including ocean type, continent type and combined oceanic and continental deposition) were different. There were also differences between the samples of the same type if the samples had different total ion concentrations. When IS>100 μeq/L, the ranges of R of ocean type deposition, continent type deposition and combined oceanic and continental deposition were 5∼7%, 5∼9% and 5∼11%, respectively. When IS<50 μeq/L, if a _i was 100%, the range of R was 33∼71% because of the lower accuracy. It was also found that R of each criterion was in the range of R as calculated in this paper when IS≥50 μeq/L, but when IS<50 μeq/L, the criteria varied greatly in their R values.     

Efficacy of a Biomonitoring (Moss Bag) Technique for Determining Element Deposition Trends on a Mid-Range (375 Km) Scale

National networks detect multi-state trends in element deposition using direct measurement methods. Biomonitoring techniques have been used to examine deposition in local areas and around point sources. We sought to determine the efficacy of a moss bag technique to detect element deposition trends on a mid-range (state) scale, and to compare these results with those of the National Acid Deposition Program/National Trends Network (NADP/NTN, 1999). We sampled heavy metals, sulfur, and nitrogen deposition (21 elements) using mesh bags containing Sphagnum russowii at nine sites, over a 375 km transect crossing southern Wisconsin (upper Midwest, USA). We found statistically significant trends of decreasing deposition in a northwesterly direction for 13 elements: Al, B, Ca, Cd, Co, Cu, Cr, Fe, Mg, Mn, Ni, S, and Zn. Six of these have moderate to large changes in concentration (14–37%). The trends for Ca, Mg, and S are consistent with regional deposition patterns in 1998 isopleth maps from the NADP/NTN (1999) which are derived from a sampling array far less dense than the transect sites. This national network indicates that Ca and Mg increase to the southeast, beyond Wisconsin borders. The fact that the present study demonstrates strong correlations between both of these elements (Ca and Mg) and Al, B, Cr, Cu, Fe, Mn, Ni, and Zn (mean r for all correlations = 0.75, p < 0.02) implies that these correlated elements also increase to the southeast in neighboring states.     

Spatial variability of the shallow groundwater level and its chemistry characteristics in the low plain around the Bohai Sea,North China

To characterize the spatial distribution of groundwater level (GWL) and its chemistry characteristics in the low plain around the Bohai Sea, shallow groundwater depth of 130 wells were determined. Water soluble ions composition, total dissolved solid (TDS), electric conductivity (EC), total hardness (TH), total alkalinity (TA), and total salt content (TS) of 128 representative groundwater samples were also measured. Classical statistics, geostatistical method combined with GIS technique were then used to analyze the spatial variability and distribution of GWL and groundwater chemical properties. Results show that GWL, TDS, EC, TH, TA, and TS all presented a lognormal distribution and could be fitted by different semivariogram models (spherical, exponential, and Gaussian). Spatial structure of GWL, TDS, EC, TH, TA, and TS changed obviously. GWL decreased from west inland plain to the east coastal plain, however, TDS, EC, and TS increased from west to east, TH and TA were higher in the middle and coastal plain area. Groundwater chemical type in the coastal plain was SO₄²⁻·Cl⁻—Na⁺ while chemical types in the inland plain were SO₄²⁻·Cl⁻—Ca²⁺·Mg²⁺ and HCO₃⁻—Ca²⁺·Mg²⁺.