Acid Deposition and Acidification of Soil and Water in the Tie Shan Ping Area, Chongqing, China

Chongqing is among the heaviest polluted cities in China. Combustion of coal with relatively high sulfur content causes high sulfur emission and deposition in the area. Effects on soils and waters of the acid deposition in the Chongqing area have been studied in the field at a forested site outside the city. Deposition chemistry and fluxes, soil and soil water chemistry as well as surface water chemistry are presented for the period 1996–1998. There are some stress symptoms at the forest in the area and severe forest damage has been reported at Nanshan, closer to Chongqing center. Monitoring of the acidification situation in the area must be followed closely as impacts may be expected if the deposition is not reduced in the future. The deposition of sulfur, H⁺ as well as calcium at the site is high. Wet deposition of sulfur is estimated to 4.7 – 5.7 g S m^?2 yr^?1 during the three years sampled; dry deposition is probably of similar size. Annual volume-weighted pH in bulk deposition was 4.0 – 4.2 and the calcium wet deposition flux was 2.6 – 3.6 g Ca²⁺ m^?2. There are considerable seasonal variations in the concentrations, related to the seasonal variations in precipitation amount (dry winter, wet summer). The soils at the site are acid with median base saturation of 12% and 8% in the topsoil and subsoil, respectively. In soil water, aluminum concentrations are typically in the range 3–8 mg L^?1. However, due to the high base cation deposition, the Al/(Ca²⁺+Mg²⁺) molar ratio is below unity in most samples, indicating little damage of forest due to aluminum in soil water.     

Aluminium Mobility at an Acid Sensitive Site with High S-Deposition

Soil water at an acid-sensitive forested catchment in southwestern Poland has been studied for four years. Median base saturation (BS) is only 5% in the podzol B-horizons. Very low pH values in the soil water from the O-horizons (10- and 90 percentiles pH 3.5 and 4.3) increased to a typical median pH in the B-horizons of 4.4, mainly by release of inorganic labile aluminium (Al_i). Median concentrations in the B horizons were 3.4mg Al_i L^?1. Al-soil/soilwater interactions were studied over a large span of sulphate concentrations resulting from both a generally decreasing S-deposition during the last decades and an increase in precipitation during the study period. These changes led sulphate to leach from the mineral soil. Aluminium mobilisation is better described by jurbanite- than by gibbsite solubility. For the soils with aluminium saturation (AlS) >90%, there is a tendency that the concentration of Al³⁺ decreases less than divalent base cations with a decrease in SO₄ ^2? concentration. This causes the critical load molar ratio (R_CL={Al³⁺}/{Ca²⁺+Mg²⁺}) to increase with a decrease in the sulphate concentration in soil water, which is not in agreement with a simple cation-exchange model.     

Behavior of Iodine in a Forest Plot,an Upland Field and a Paddy Field in the Upland Area of Tsukuba,Japan. Iodine Concentration in Precipitation,Irrigation Water,Ponding Water and Soil Water to a Depth of 2.5 m

In the course of a series of studies conducted to investigate the long-term behavior of ¹²⁹I (which has a half-life of 16 million years) in the environment, the concentration of stable iodine (¹²⁷I) in precipitation, irrigation water and soil water to a depth of 2.5 m in a forest plot, an upland field and a paddy field in the upland area of Tsukuba, Japan, was determined. In the forest plot, the mean iodine concentrations in soil water at all the depths ranged from 0.13 to 0.21 μg L^?1, about one-tenth of the values recorded in precipitation (weighted mean 2.1 μg L^?1). This finding suggests that the major part of iodine in precipitation was sorbed onto the surface soil horizon under oxidative conditions. In the upland field, the mean iodine concentration in soil water was 2.2 μg L^?1 at a depth of 0.2 m and it decreased to 0.34–0.44 μg L^?1 at a depth of 0.5 m or more; these concentrations were about one-fifth of that in precipitation. This suggested that the major part of the iodine derived from precipitation was sorbed onto the subsurface soil horizon (at depths between 0.2 and 0.5 m). In the paddy field, during the non-irrigation period, the mean iodine concentrations in soil water at all the depths ranged from 1.8 to 4.8 μg L^?1, almost the same values as those recorded in precipitation. During the irrigation period, the mean iodine concentrations at depths of 0.2 and 0.5 m were 18.8 and 16.7 μg L^?1, values higher than the 10.9 μg L^?1 value recorded in irrigation water and the 11.8 μg L^?1 value recorded in ponding water. However, at a depth of 1.0 m or more, the mean iodine concentrations in soil water rapidly decreased from 7.3 to 1.8 μg L^?1. These data suggested that a significant amount of iodine flowed out from the paddy field by surface runoff and a considerable amount of iodine that leached to a depth of 0.5 m was retained onto the mildly oxidative soil horizon (2Bw) that lay at depths between 0.5 and 1.0 m. At a depth of 2.5 m in the paddy field, the mean iodine concentration in soil water decreased to 1.8 μg L^?1, but this level was much higher than those in the forest plot and upland field at the same depth, which suggested that a significant amount of iodine had leached into the groundwater-bearing layer. There was a negative correlation (r=-0.889) between the E_h of soil and the iodine concentration in soil water (0.2 m depth) of the paddy field. Particularly, when the E_h of soil fell below approximately 150 mV, the iodine concentration rapidly increased to above 10μg L^?1. As for the chemical forms of iodine in precipitation, irrigation water, ponding water and soil water during the winter irrigation period in the paddy field with oxidative conditions, 58–82% of iodine consisted of IO^? ₃ and 17–42% of iodine consisted of I^?. In the soil water during the summer irrigation period in the paddy field under reductive conditions, 52–58% of iodine consisted of I^?, and 42–47% consisted of IO^? ₃.     

Selenium Behavior in Open Bulk Precipitation, Soil Solution and Groundwater in Alluvial Fan Area in Tsukui, Central Japan

A monitoring study was carried out in an alluvial fan area in Tsukui, Central Japan during the study period of 1999–2003, in order to explain selenium (Se) behaviors in ecosystem combined with air, soil and groundwater. Monthly Se concentrations in open bulk precipitation (rainfall+aerosol, gaseous deposition and etc.), soil solution (collected by porous ceramic-cup) and groundwater ranged from 0.1 to 1.4 μg L^?1 (volume-weighted average: 0.34 μg L^?1), 0.21 to 1.0 μg L^?1 (0.48 μg L^?1) and 1.6 to 2.4 μg L^?1 (2.2 μg L^?1), respectively. Se concentration in open bulk precipitation was negatively correlated with the rainfall amount. Se concentration in soil solution significantly increased with DOC concentration in soil solution. Besides, despite atmospheric Se input and rainfall to the grassland study area, Se concentration in soil solution and groundwater received no significant effect from the rainfall amount, pH, Se, DOC, SO₄ ^2?, NO₃ ^? and EC in rainfall. Even though Se concentrations in groundwater were significantly correlated with soil solution volume, Se, DOC and NO₃ ^? and groundwater level, the result of multiple regression analyses (MRA) indicated that the groundwater Se was negatively influenced by groundwater level, which depended on groundwater recharge. Se was transported into the groundwater through the groundwater recharge that largely increased in this alluvial fan study area after heavy rain.     

Trends of bulk precipitation and Streamwater Chemistry in a Small Mountainous Watershed on the Shikoku Island of Japan

For this study, characteristics and trends of the chemical constituents in bulk precipitation and streamwater were observed in a small mountainous watershed on the Shikoku Island of Japan, which covered an area of 27.4 hectares. Bulk precipitation and streamwater chemistry data spans from May 1997 to October 2004, and January 1996 to October 2004, respectively. The data were tested for two types of trends: (1) a monotonic trend to determine if concentrations of the chemical constituents were generally decreasing, increasing, or stable during the study period, and (2) a step trend to determine if a change occurred following the December 1999-January 2000 forest thinning. Both parametric and non-parametric statistical analyses were carried out in this study. Although the study area is only 35 km away from the Pacific Ocean, bulk precipitation chemistry was also influenced by terrestrial sources to a large extent. Streamwater chemistry was influenced by bedrock weathering, which was dominated by Ca²⁺ and HCO_3?, and was not strongly related top recipitation chemistry.Non?parametric Seasonal Kendall Test(SKT)showedadeceasingtr end of Ca ₂₊ and anincreasing tr end of K ₊ in bulk precipitation.Despite the decreasing trend of Mg ₂₊, an increasing trend of pH was found in the stream water.Non?paramet ric Mann?Whit ney?Wilcoxon Rank Sum test showed statistically sign if icantin creases of NO _3? and Ca ₂₊ in stream water followed by a moderate thinning operation.     

Estimation of the Maximum Critical Load for Sulfur in South Korea

The maximum critical load of sulfur and its exceedance by the sulfur deposition of 1994–1997 were mapped for South Korea with a spatial resolution of 11 × 14 km using the steady-state mass balance method. The Korean soil and geological maps were used as basis for the estimations of the critical alkalinity leaching and the weathering rate of base cations. The normalized difference vegetation index data obtained from the Advanced Very High Resolution Radiometer (AVHRR) together with the observed primary productivity of plants were used for the estimation of the critical uptake of base cations. Wet deposition of the non-sea-salt base cations was derived from measured base cation concentrations in precipitation, precipitation rate and air concentration of total suspended particulate while dry deposition of base cations was estimated using the inferential technique using scavenging ratios. The predominant ranges of base cation weathering, uptake and deposition were estimated to be of 200 – 600 eq ha^?1 yr^?1, 200 – 400 eq ha^?1 yr^?1 and 400 – 600 eq ha^?1 yr^?1, respectively. Critical alkalinity leaching was mainly in the range of 1000 – 2000 eq ha^?1 yr^?1 due to relatively high value of precipitation runoff. Exceedance of sulfur critical load was found at 40 % of the ecosystems considered mainly in the southeastern part of Korea, and about 60 % of Korea ecosystems were sustainable against sulfur acidity loadings.     

Chemical Composition of Precipitation, Throughfall and Soil Solutions at Two Forested Sites in Guangzhou, South China

Rain water at two forested sites in Guangzhou (south China) show high concentrations of SO₄ ^2?, NO₃ ^? and Ca²⁺ and display a remarkable seasonal variation, with acid rain being more important during the spring and summer than during the autumn and winter. The amount of acid rain represents about 95% of total precipitation. The sources of pollutants from which acid rain developed includes both locally derived and long-middle distance transferred atmosphere pollutants. The seasonal variation in precipitation chemistry was largely related to the increasing neutralizing capacity of base cations in rainwater in winter. Soil acidification is highlighted by high H⁺ and Al³⁺ concentrations in soil solutions. The variation in elemental concentration in soil solution was related to nitrification (H⁺, NH₄ ⁺ and NO₃ ^?) and cation exchange reaction (H⁺, Al³⁺) in soil. The negative effect of soil acidification is partly dampened by substantial deposition of base cations (Ca²⁺, Mg²⁺ and K⁺) in this area.     

Soil matric potential and salt transport in response to different irrigated lands and soil heterogeneity in the North China Plain

Purpose

In the lowland area of the North China Plain (NCP), increasing utilization of brackish water could promote the transformation of precipitation into available water resources, and alleviate the conflict between increase food production and freshwater scarcity. However, the processes of soil water movement and salt migration might be altered, because utilization of brackish water results in frequent changes in groundwater depth and thickness of vadose zone. Thus, it was necessary to understand soil water movement and salt migration when using brackish water for irrigation.

Materials and methods

In this study, soil matric potential (SMP) and total dissolved solids (TDS) at multiple depths were measured in situ to investigate the mechanisms of soil water movement and salt migration at one grassland (site 1) and at three typical irrigated croplands (sites 2, 3, and 4) with different soil textures and groundwater depths in a lowland area of the NCP.

Results and discussion

The study showed that deep soil water and groundwater were recharged generally following heavy precipitation during rainy season. SMP values increased quickly at site 4 due to relatively homogeneous soils, followed by site 3?>?site 2?>?site 1 with an obvious hysteresis response of SMP at multiple depths to precipitation. Soil water mainly moved downward in piston flow, and preferential flow also existed in the soil above 100 cm in the percolation process at four sites. Generally, SMP values followed the order of site 4?>?site 1?>?site 2?>?site 3 and exhibited an inverse trend for TDS, which was mainly due to soil heterogeneity and soil texture in vertical profiles. The differences in SMP among the four sites were mainly due to land use and groundwater depth. There were significantly differences in spatiotemporal distribution of water and salts between homogenous and heterogeneous soils. The processes of infiltration and water redistribution ended quickly in relatively homogeneous soils after heavy rains. However, there was obvious hysteresis in SMP with an increase in soil depth in heterogeneous soils.

Conclusions

Homogenous soils favored water infiltration, salt leaching, and groundwater recharge, and the flow of soil water flow was blocked and salt accumulated significantly in layered soils. The soil water movement and the transformation relationship between water and salt in the vadose zone provided a basis for utilization of brackish water irrigation in lowland region of the NCP.

     

Long-term development of element budgets in a Norway spruce (Picea abies (L.) Karst.) forest of the German solling area

To evaluate ecosystem response to changing atmospheric deposition, element budgets were established over the period from 1973 to 1991 for a Norway Spruce (Picea abies (L.) Karst.) site. Budgets for Na⁺, Cl^?, Ca²⁺, Mg²⁺, N, S and H⁺ were based on total deposition and seepage water fluxes. The deposition of Ca²⁺, Mg²⁺, particularly, of S and H⁺ decreased with time, while calculated N deposition remained constant at a high level. The decrease in Ca²⁺ deposition led to a reduction of Ca²⁺ fluxes with seepage water. The decrease of Mg²⁺ deposition did not have an effect on the output fluxes of Mg²⁺. The reversibility of soil and seepage water acidification by reduced S deposition was delayed by the release of previously accumulated soil SO ₄ ^2? . The highest NO ₃ ^? fluxes were observed during the period of 1986 to 1988; NO ₃ ^? fluxes in general demonstrated a considerable annual and periodic variation. Total N accumulation in the ecosystem amounted to nearly 590 kg ha^?1 yr^?1 during the observation period. The major sink of N in the spruce site is the aggrading humus layer. The results emphasize the need for measurements over several years to make conclusions regarding the function of ecosystems in response to atmospheric deposition.     

Geochemistry of Manganese in Neutral to Alkaline Soils of Punjab,Northwest India and Its Availability to Wheat and Rice Plants

Manganese (Mn) release in 18 soil–water suspensions after their equilibration for 24 and 240 h periods at 25°C was studied in a laboratory experiment. Total dissolved Mn released into the soil solution was observed to increase from a range of 0.03–0.41 mg L^?1 (mean = 0.13 mg L^?1) to a range of 0.45–44.44 mg L^?1 (mean = 22.40 mg L^?1) with the increase in incubation periods from 24 to 240 h, respectively. The increase in Mn released was observed to be related with the redox potential (pe) induced by incubation conditions. After 24 h of equilibration period, pe of soil–water suspension ranged from ?1.75 to 0.77 (mean = ?0.24). Increasing the incubation period to 240 h, pe of soil–water suspensions declined in the range of ?4.49 to ?2.74 (mean = ?3.29). Laboratory results of redox pe and corresponding dissolved manganese concentrations of some soil–water equilibrated systems were compared with the leaf Mn content in wheat and rice plants grown in the fields, from where soil samples were collected for laboratory experiment. These results demonstrated that decline in pe due to longer equilibration period (240 h) of soil–water systems in the laboratory experiment or keeping standing water for a couple of weeks in the fields for cultivation of rice crop results in higher release of Mn and eventually its higher uptake in rice than in wheat plants. Leaf manganese content in rice ranged from 94 to 185 mg kg^?1, which was markedly higher than its range from 25 to 62 mg kg^?1 found in the wheat grown at 10 different sites. Pourbaix diagrams were drawn for different soil–water systems containing carbonate, phosphate, or sulfate along with manganese. The presence of carbonate and phosphate anions along with manganese oxides minerals in the soil–water systems of all soils results in its precipitation as MnCO₃ and MnHPO₄, respectively, in both oxidized and reduced soil field environment. In Punjab, wheat and rice crops are generally cultivated on soils heavily fertilized with P fertilizers. The presence of phosphate anion with manganese oxides minerals in the soil–water systems of all soils results in the precipitation MnHPO₄ in both oxidized and reduced soil field environment. Thus, in P-fertilized soil, MnHPO₄ compound is even more predominant than aqueous Mn²⁺ and its solubility actually controlled the availability of Mn²⁺ to plants.     

Chloride cycling in two forested lake watersheds in the west-central adirondack mountains,New York,U.S.A.

The chemistry of precipitation, throughfall, soil water, ground water, and surface water was evaluated in two forested lake-watersheds over a 4-yr period to assess factors controlling Cl^? cycling. Results indicate that Cl^? cycling in these watersheds is more complex than the generally held view of the rapid transport of atmospherically derived Cl^? through the excosystem. The annual throughfall Cl^? flux for individual species in the northern hardwood forest was 2 to 5 times that of precipitation (56 eq ha^?1), whereas the Na⁺ throughfall flux, in general, was similar to the precipitation flux. Concentrations of soil-water Cl^? sampled from ceramic tension lysimeters at 20 cm below land surface generally exceeded the Na⁺ concentrations and averaged 31 μeq L^?1, the highest of any waters sampled in the watersheds, except throughfall under red spruce which averaged 34 μeq L^?1. Chloride was concentrated prior to storms and mobilized rapidly during storms as suggested by increases in streamwater Cl^? concentrations with increasing flow. Major sources of Cl^? in both watersheds are the forest floor and hornblende weathering in the soils and till. In the Panther Lake watershed, which contains mainly thick deposits of till (>3 m), hornblende weathering results in a net Cl^? flux 3 times greater than that in the Woods Lake watershed, which contains mainly thin deposits of till. The estimated accumulation rate of Cl^? in the biomass of the two watersheds was comparable to the precipitation Cl^? flux.     

Identifying sources of snowmelt acidification with a watershed mixing model

We used ionic tracers to estimate the volume of old (soil and ground) water interacting with snowmelt in eleven Adirondack, NY watersheds. The contribution of old water varied from 66 to 90%, with no general relationship between old water % and soil depth to till. This approach also discriminated between watershed retention and release of particular ions to lake outlet water during snowmelt. Most watersheds released NO₃ ^? during snowmelt, in addition to the snowpack NO₃ ^?. Nitrification of snowpack NH₄ ⁺ explained part of the additional NO₃ ^? in lake out outlet water, but some NO₃ ^? was likely mineralized nitrogen from soil organic matter. All watersheds retained NH₄ ⁺ as well. Nitrogen release was greatest in the acidic watersheds in the southwestern Adirondacks, a region thought to be impacted by anthropogenic deposition. During snowmelt, Ca²⁺ and Mg²⁺ ions (presumably from soil exchange sites) were also released from most watersheds. In watersheds with acidic (minimum pH<4.6) lake outlet water, Al was also released during snowmelt. Thus, lake outlet water acidification during snowmelt was both buffered by cation release, and intensified by NO₃ ^? release. If the soil exchangeable cation pools were not replenished prior to snowmelt, or NO₃ ^? mobilization were increased, acidification during snowmelt would intensify.     

Biogeochemistry of a forested watershed in the central Adirondack Mountains: Temporal changes and mass balances

Information on atmospheric inputs, water chemistry and hydrology were combined to evaluate elemental mass balances and assess temporal changes in elemental transport from 1983 through 1992 for the Arbutus Lake watershed. This watershed is located within a northern hardwood ecosystem at the Huntington Forest within the central Adirondack Mountains of New York (USA). Changes in water chemistry, including increasing NO₃ ^? concentrations (1.1 μmol _c , L^?1 yr-1), have been detected during this study period. Starting in 1991 hydrological flow has been measured from Arbutus Lake and these measurements were compared with predicted flow using the BROOK2 hydrological simulation model. The model adequately (r²=0.79) simulated flow from this catchment and was used to estimate drainage for earlier periods when direct hydrological measurements were not available. Modeled drainage water losses coupled with estimates of wet and dry atmospheric deposition were used to calculate solute budgets. Export of SO₄ ^2? (831 mol _c ha^?1 yr^?1) from the greater Arbutus Lake watershed exceeded estimates of atmospheric deposition in an adjacent hardwood stand suggesting an additional source of S. These large drainage losses of SO₄ ^2? also contributed to the drainage fluxes of basic cations (Ca²⁺, Mg²⁺, K⁺ and Na⁺). Most of the atmospheric inputs of inorganic N were retained (average of 74% of wet precipitation and 85% total deposition) in the watershed. There were differences among years (56 to 228 mol ha^?1 yr^?1) in drainage water losses of N with greatest losses occurring during a warm, wet period (1989–1991).     

Responses of soil microbial community to nitrogen fertilizer and precipitation regimes in a semi-arid steppe

Purpose

Changes of nitrogen (N) cycle caused by N fertilization and precipitation regimes have affected the key ecosystem structure and functions in temperate steppe, which may modify the structure of soil microbial communities involved in N transformation. This paper was designated to examine the response of soil ammonia oxidizers and denitrifiers to the N fertilization and precipitation regimes in a semi-arid steppe where N and water contents are major limiting factors of the grassland productivity.

Materials and methods

This study was based on a long-term N fertilization and precipitation regimes experiment in Inner Mongolia (116° 17′ 20″ E, 42° 2′ 29″ N). The treatments including CK (control), R (reduced precipitation), W (30% increase in precipitation), N (10 g N m^?2 y^?1), RN (reduced precipitation and 10 g N m^?2 y^?1), and WN (30% increase in precipitation and 10 g N m^?2 y^?1). Soil basic chemical properties and microbial activities were analyzed. Molecular methods were applied to determine the abundance, structure and diversity of ammonia oxidizers and denitrifiers. Statistical analysis detected the main and interactive effect of treatments on soil microbial communities and revealed the relationship between soil microbial community structures and environmental factors.

Results and discussion

N fertilization significantly increased ammonia-oxidizing bacteria (AOB) abundance. Ammonia-oxidizing archaea (AOA) community structure was markedly changed in N fertilizer treatment and strongly affected by soil pH, while soil nitrate and water content correlated with AOB community structure. Soil nitrate was the key factor influencing nirK gene community structure, while soil pH and water content explained much of the variations of nosZ gene community. AOB-amoA and nosZ gene community diversities were influenced by precipitation regimes and interaction of N fertilization and precipitation regimes, respectively.

Conclusions

N fertilization and precipitation regimes had significant influences on the changes of soil properties and microbial functional communities. Soil nitrification was mainly driven by AOB in the semi-arid grassland. Changes of substrate content and soil pH were the key factors in shifting functional microbial communities. The non-synergistic effects of N fertilization and precipitation regimes on the microbial functional groups indicated that the negative effect of lower pH induced by N fertilization would be alleviated by precipitation regimes, which should be well considered in grassland restoration.

     

Aluminium sulphate solubility in acid forest soils in Denmark

Ion leaching in 3 sandy spruce forest soils of different origin and pH was investigated in the laboratory. Zero-tension lysimeters containing undisturbed soil columns of varying soil depth were subjected to H₂SO₄ loadings for a period of 9 weeks. The analysis of the resulting leachate supports the hypothesis that Al-sulphate minerals may form in acidic soils when exposed to acid (H₂SO₄) deposition. In the B horizon of a glaciofluvial sandy soil (pH 4.2), both H⁺ and sulphate ions were retained to maintain 2pH + PSO₄ = 11.9 in the leachate solutions. This relation between H⁺ and sulphate activity may be due to an adsorption mechanism or a precipitation mechanism. The precipitation mechanism is favored by the good fit of leachate composition to the conditions for jurbanite [AlOHSO₄] formation from gibbsite [Al(OH)₃]. In the B horizon of a sandy till at pH 3.7, the Al in soil solution (0.5 mmol L^?1) was leached with sulphate. As the sulphate load was increased, some sulphate was retained. This may also be due to the dissolution and precipitation of an Al-sulphate mineral. The ion activity products of leachate solutions from the B horizon of this soil were close to the pK_s reported for jurbanite. The conditions for the possible existence and/or formation of Al-sulphate minerals in acidic soils are discussed.     

Trends of Major Inorganic Species at the Small Watershed Ecosystem in Northern Tama Hills, the Western Tokyo Metropolitan Area, Japan

Acid rain impacts on the small forested watershed in northern Tama Hills in the western Tokyo metropolitan area Japan were investigated by surveying the trends of major inorganic species in rain and spring water during the years from 1991 to 1997. The ecosystem had been stressed by the annual H⁺-deposition of around 0.43 kmol/ha. The spring water outflow corresponded to ca. 27% of the precipitation. Budgets for the precipitation input and spring water output gave good balance for Cl^?,?0.01 ±0.09 kmol/ha, net gains for H⁺, NO₃ ^? and SO₄ ^2?, and to the contrary, relatively large net losses for Na⁺, Mg²⁺, Ca²⁺, Si(as H₄SiO₄) and HCO₃ ^?, thus suggesting the dissolution of chemical weathered products of silicate minerals. Further, in spring water, some concentration relationships were found: CNa⁺ = 376.5?2.05CCl^? (R²=0.748), CNa⁺=12.69+0.5556CHCO₃ ^? (R²=0.872) and CH₄SiO₄=130.0 + 1.108CHCO₃ ^? (R²=0.816). Evidently, the spring water chemistry reflected probable geochemical changes in the soil layer of the watershed. Mass balance in the ecosystem and estimation of the spring water output of chemical weathered products were investigated     

Changes in water quality in the Laflamme Lake Watershed Area,Canada

The Laflamme Lake Watershed Area is located in a sensitive region on the Canadian Shield and is subjected to wet atmospheric loading between 17 and 25 kg ha^?1 yr^?1. From 1981 to 1988, the level and fluctuations of the atmospheric deposition of acidifying substances has led to various responses in the water chemistry of headwater lakes in the area. The general trend in atmospheric inputs is a gradual increase of acidifying substances from 1981 to 1985 followed by a 2 yr decrease then a return to previous values. In the two lakes with almost no alkalinity acidification has occured throughout the 1983 to 1988 period. In the four lakes with slightly higher alkalinity values, a reversal in acidification is seen when atmospheric loading decreased in 1986. Along with the interannual trends, seasonal variability to acidification occurs with sensitivity of surface waters being highest during spring melt. Sensitivity to acidification can also be altered by watershed processes and in the Laflamme Lake Watershed, soil processes are effective in altering the acidity of precipitation before it reached the lake. In this watershed, wet atmospheric inputs of H⁺ and NO₃ ^? are larger than surface water outputs while the reverse occurs for Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^? and SO₄ ^2?.     

Sea Ice Approach and Chemical Species in Precipitation at Abashiri, Japan

Abashiri is a rural city on Hokkaido Island, Japan. It lies directly to the south of the Okhotsk Sea, which is the lowest latitude sea to freeze. We collected daily deposition samples over two periods: from Jan. 1997 to Mar. 1998, and from Nov. 1998 to Mar. 1999. The average concentrations of anthropogenic chemical species (NO₃ ^?, non-seasalt(nss)-SO₄ ^2?) were relatively low and those of seasalt species (Na⁺, Cl^?, Mg²⁺) were high in Japanese precipitation samples. During the period of study, we found that, when sea ice forms and approaches the coast, concentrations of seasalt species become lower, while almost no changes are found in the anthropogenic chemical species.     

Behavior of iodine in a forest plot,an upland field and a paddy field in the upland area of Tsukuba,Japan: Seasonal variations in iodine concentration in precipitation and soil water and estimation of the annual iodine accumulative amount in soil horizons

Abstract

In the course of a series of studies conducted to investigate the long-term behavior of ¹²⁹I (which has a half-life of 16 million years) in the environment, seasonal variation in the concentration of stable iodine (¹²⁷I) in precipitation and soil water to a depth of 2.5 m in a forest plot, an upland field and a paddy field in the upland area of Tsukuba, Japan, were determined. Iodine concentration in precipitation tended to increase during the summer (high air temperature) season and low-rainfall period, and a positive high correlation was observed between annual rainfall and the annual amount of iodine supplied by precipitation. No seasonal variations in iodine concentration in soil water were observed at any depth in the forest plot and upland field unlike at shallow depths (0.2 and 0.5 m) in the paddy field. In the paddy field, from the beginning of summer irrigation, under flooding conditions, iodine concentration in soil water at shallow depths (0.2 and 0.5 m) continuously increased, and immediately before mid-summer (intermittent) drainage and drainage, the maximum iodine concentration (approximately 50 µg L^?1) and lowest E_h values (approximately ?150 to ?200 mV) were recorded. These high iodine concentration levels and low E_h values were ascribed to high air temperature (approximately > 25°C on average every 10 days) and the continuation of the groundwater level above the ground surface. As for the temporary winter irrigation period (mean daily air temperature 2?4°C), the iodine concentration was low (1.7–3.7 µg L^?1) at all depths, as was the case in the non-irrigation period. After mid-summer drainage, and drainage, the iodine concentration in soil water at depths of 0.2 and 0.5 m decreased drastically as the groundwater level decreased. The mean annual amount of iodine accumulated in the surface soil horizons (0–0.67 m) in the forest plot was estimated to be approximately 2.9 mg m^?2 (7.5 µg kg^?1 dry soil), which coincided with the mean annual amount of iodine supplied to the earth surface by precipitation. A mildly oxidative subsurface 2Bw horizon (0.60–0.89 m) in the paddy field was estimated to illuviate approximately 3.1 mg m^?2 (20 µg kg^?1 dry soil) of iodine annually by retaining iodine in the soil water percolated to this horizon.     

Increasing the Knowledge of Heavy Metal Contents and Sources in Agricultural Soils of the European Mediterranean Region

This paper contributes to increase the knowledge of the contents and sources of heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) to agricultural soils in Castellón province (Spain), a representative area of the European Mediterranean region. The surface horizons of 77 agricultural soils under vegetable crops were sampled and heavy metals were analysed by atomic absorption spectroscopy (AAS) after microwave extraction using the USEPA 3051A method. Mean heavy metal contents were similar to those obtained in other areas of this region. However, heavy metal contents (e.g. Cr, Pb) in some soils were above the maximum limit set in the 86/278/CEE Directive. Multivariate analysis (correlation analysis and principal component analysis – PCA) was performed so as to identify the sources of heavy metals to soils. Co, Fe and Ni were highly correlated amongst them (r?>?0.800; p?<?0.01), whereas Cr and Mn were less correlated with Co, Fe and Ni (r?>?0.500; p?<?0.01). Other relationships among heavy metals (i.e. Cu, Pb and Zn) were also identified, although correlation coefficients were not so high as those among Co, Fe and Ni (r?<?0.500; p?<?0.01). Contents of Co, Fe, Mn and Ni were interpreted to be mainly associated with parent rocks corresponding to the first principal component (PC1). On the other hand, Cd, Cu, Pb and Zn were interpreted to be mainly related to anthropogenic activities and comprised the second (Pb and Zn) and the third (Cd and Cu) principal components (PC2 and PC3, respectively), designated as anthropogenic components. Remarkably, Cr appears to be related in the study area to both the lithogenic and the anthropogenic components. Lithogenic elements were highly correlated with soil properties. Positive relationships with CEC (r?>?0.200; p?<?0.05) and clay (r?>?0.400; p?<?0.01), and negative relationships with carbonates (r?>??0.400; p?<?0.01) and sand (r?>??0.300; p?<?0.01) were observed. Anthropogenic elements were less correlated with soils properties, since these elements are generally more mobile because they form more soluble chemical species associated to anthropogenic sources. Particularly, no correlation was found between Cd and Zn and soil properties. These findings extend results achieved in other parts of the region, highlighting the need to set soil quality standards in order to declare soils affected by anthropogenic pollution, particularly in the case of anthropogenic metals such as Cd, Cu and Pb, and also Cr and Zn in some areas. Further knowledge from other areas in this region would improve the basis for proposing such standards at regional level, which is a priority objective in Europe according to the European Thematic Strategy for Soil Protection.