Effects of Catchment and Riparian Landscape Setting on Water Chemistry and Seasonal Evolution of Water Quality in the Upper Han River Basin,China

Six-year (2005–2010) evolution of water chemistry (Cl⁻, NO₃ ⁻, SO₄ ²⁻, HCO₃ ⁻, Na⁺, K⁺, Ca²⁺ and Mg²⁺) and their interactions with morphological properties (i.e., slope and area), land cover, and hydrological seasonality were examined to identify controlling factors and processes governing patterns of stream water quality in the upper Han River, China. Correlation analysis and stepwise multiple regression models revealed significant correlations between ions (i.e., Cl⁻, SO₄ ²⁻, Na⁺ and K⁺) and land cover (i.e., vegetation and bare land) over the entire catchment in both high- and low-flow periods, and in the buffer zone the correlation was much more stronger in the low-flow period. Catchment with steeper slope (>15°) was negatively correlated with major ions, largely due to multicollinearity of basin characteristics. Land cover within the buffer zone explained slightly less of major elements than at catchment scale in the rainy season, whereas in the dry season, land cover along the river networks in particular this within 100 m riparian zone much better explained major elements rather than this over the entire catchment. Anthropogenic land uses (i.e., urban and agriculture) however could not explain water chemical variables, albeit EC, TDS, anthropogenic markers (Cl⁻, NO₃ ⁻, SO₄ ²), Na⁺, K⁺ and Ca²⁺ significantly increased during 2005–2010, which was corroborated by principal component analyses (PCA) that indicated anthropogenic inputs. Observations demonstrated much higher solute concentrations in the industrial-polluted river. Our results suggested that seasonal evolution of water quality in combined with spatial analysis at multiple scales should be a vital part of identifying the controls on spatio-temporal patterns of water quality.     

Effects of different ionic compositions on survival and growth of <Emphasis Type="Italic">Physa acuta</Emphasis>

Most inland saline waters in southern Australia predominantly contain Na⁺ and Cl⁻ as major ions. The proportions of Ca²⁺, Mg²⁺, SO₄ ²⁻, HCO₃ ⁻ and CO₃ ²⁻ in these waters somewhat vary and might influence salinity tolerance of freshwater organisms. Here the salinity stress of five ionic compositions to the freshwater snail Physa acuta Draparnaud (Gastropoda: Physidae) was compared: commercial sea salt Ocean Nature (ON), synthetic Ocean Nature (ONS) and three saline water types that are common in southern Australia (ONS but without [1]: SO₄ ²⁻, HCO₃ ⁻ and CO₃ ²⁻, [2]: Ca²⁺, HCO₃ ⁻ and CO₃ ²⁻, [3]: Ca²⁺, Mg²⁺), Milli-Q water was used as a negative control. The 96-h LC₅₀ values for all treatments did not differ. However in prolonged sub-lethal exposures, results varied depending on the ionic composition. Growth was negative and shell strength reduced in treatments lacking Ca. Though the content of major cationic elements (Ca, Mg, Na and K) did not differ per unit dry weight of snail across the treatments, the total load of these elements per individual snail varied among treatments. Furthermore, at the sub-lethal salinities tested, 1 and 5 mS cm⁻¹, ionic compositions had more effect on the snail’s growth than salinity. The long-term effects on freshwater animals, especially taxa with calcium-based exoskeletons, from exposure to common saline water types with low calcium concentrations will likely be greater than from exposure to saline waters with an ionic composition similar to seawater.     

Effects of Anions on the Capacity and Affinity of Copper Adsorption in Two Variable Charge Soils

Effects of nitrate,(NO₃⁻) chloride (Cl⁻), sulfate (SO₄^2-, and acetate (Ac⁻) on Cu²⁺ adsorption and affinity of the adsorbed Cu²⁺ were evaluated in two Fe and Al enriched variable charge soils from Southern China. The maximum adsorption of Cu²⁺ (M, a parameter from the Langmuir isotherm model) in the presence of different anions decreased in the order Cl⁻ > Ac⁻ > NO₃⁻ > SO₄^2- for both soils. The clayey loamy soil (mixed siliceous thermic Typic Dystrochrept, TTD), developed on the Arenaceous rock, adsorbed less Cu²⁺ than the clayey soil (kaolinitic thermic Plinthudults, KTP), derived from the Quaternary red earths, regardless of anion type present in the medium. The affinity of adsorbed Cu²⁺ to both soils could be characterized by the Kd (distribution coefficient) values and successive extraction of the adsorbed Cu²⁺ with 1-mol NH₄Ac L⁻¹. The log₁₀Kd value was smaller for the TTD soil than for the KTP soil and decreased in the order of Cl⁻ > NO₃⁻ > SO₄^2- > Ac⁻ at low initial Cu²⁺ concentrations (≤40 mg Cu²⁺L⁻¹), whereas at 80 mg Cu²⁺L⁻¹, the log₁₀Kd value was similar for NO₃⁻, SO₄^2-, and Ac⁻, but was slightly higher for Cl⁻. Complete extraction of Cu²⁺ adsorbed in the presence of Ac⁻ was achieved. Influence of NO₃⁻ and SO₄^2- on the affinity of adsorbed Cu²⁺ was similar, but the effects of Cl⁻ depended on the initial Cu²⁺ concentrations. The extracted percentage of the adsorbed Cu²⁺ in the presence of NO₃⁻ or SO₄^2- increased with increasing Cu²⁺ adsorption saturation. The presence of Cl⁻, NO₃⁻, or SO₄^2- markedly decreased the equilibrium solution pH for both soils with increasing initial Cu²⁺ concentrations, and the delta pH values at the highest Cu²⁺ level were 0.5, 0.63, and 0.55 U for the TTD soil and 0.79, 0.84, and 0.93 U for the KTP soil, respectively for the three anions. The presence of Ac⁻ had a minimal influence on the equilibrium solution pH because of the buffering nature of the NaAc/HAc medium which buffered the released protons. The effects of anions on Cu²⁺ adsorption and affinity of the adsorbed Cu²⁺ were dependent on anion types and were apparently related to the altered surface properties caused by anion adsorption and/or the formation of anion– Cu²⁺ complexes.     

Soil solution chemistry of two reclamation sites in the Lusatian lignite mining district as influenced by organic matter application

Due to a large reclamation (recultivation) demand in the Lusatian lignite mining district, efficient strategies for the rehabilitation of abandoned mine sites are needed. A field study was conducted for comparing the effects of three different fertilizer treatments (mineral fertilizer, sewage sludge and compost) on soil solution chemistry of both a lignite and pyrite containing spoil as well as a lignite and pyrite free spoil. The lignite and pyrite containing spoil was ameliorated with fly ash from a lignite power plant (17–21 t ha⁻¹ CaO), whereas the lignite and pyrite free site received 7.5 t ha⁻¹ CaO in form of limestone. Fertilizer application rates were: mineral fertilizer 120 N, 100 P and 80 K kg ha⁻¹. 19 t ha⁻¹ sewage sludge and 22 t ha⁻¹ compost were applied. Soil solution was sampled in 20, 60 and 130 cm depth for the period of 16 months. Solution was collected every fortnight and analysed for pH, EC, Ca²⁺, Mg²⁺, K⁺, Na⁺, Feⁿ⁺, Alⁿ⁺, Mn²⁺, Zn²⁺, NO₃ ⁻, NH₄ ⁺, SO₄ ²⁻, Cl⁻, PO₄ ³⁻, C_inorg and DOC. Lignite and pyrite containing spoil differed clearly from lignite and pyrite free spoil regarding soil solution concentrations and composition. Acidity (H⁺) produced by pyrite oxidation led to an enhanced weathering of minerals and, therefore, to at least 10 fold higher soil solution concentrations compared to the lignite and pyrite free site. Major ions in solution of the lignite and pyrite containing site were Ca²⁺, Mg²⁺, Feⁿ⁺, Alⁿ⁺ and SO₄ ²⁻, whereas soil solution at the lignite and pyrite free site was dominated by Ca2+, Mg²⁺ and SO₄ ²⁻. At both sites application of mineral fertilizer led to an immediate but short term (about 1 month) increase of NO₃ ⁻, NH₄ ⁺ and K+ concentrations in soil solution down to a depth of 130 cm. Application of sewage sludge caused a long term (about 16 months) increase of NO_{3 3} ⁻ in the topsoil, whereas NO₃ ⁻ concentrations in the subsoil were significantly lower compared to the mineral fertilizer plot. Compost application resulted in a strong long-term increase of K+ in soil solution, whereas NO₃ ⁻ concentrations did not increase. Concentrations of PO₄ ³⁻ in soil solution depend on solution pH and were not correlated with any treatment. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

Spatial distributions and net deposition rates of mineral elements in the elongating wheat (Triticum aestivum L.) leaf under saline soil conditions

Wheat leaf growth is known to be spatially affected by salinity. The altered spatial distribution of leaf growth under saline conditions may be associated with spatial changes in tissue mineral elements. The objective of this study was to evaluate the spatial distributions of mineral elements and their net deposition rates in the elongating and mature zones of leaf 4 of the main stem of spring wheat (Triticum aestivum L. cv. Lona) during its linear growth phase under saline soil conditions. Plants were grown in an illitic-chloritic silty loam with 0 and 120 mM NaCl. Three days after emergence of leaf 4, sampling was begun at 3 and 13 h into the 16-h light period. Spatial distributions of fresh weight (FW), dry weight (DW), and Na⁺, K⁺, Cl⁻, NO⁻ ₃, Ca²⁺, Mg²⁺, total P, and total N in the elongating and mature tissues were determined on a millimeter scale. The patterns of spatial distribution of Na⁺, Cl⁻, K⁺, NO₃ ⁻, and Ca²⁺ in the growing leaves were affected by salinity, while those of Mg²⁺, total P, and total N were not. Sodium, K⁺, Cl⁻, Ca²⁺, Mg²⁺, and total N concentrations (mmol · kg⁻¹ FW) were consistently higher at 120 mM NaCl than at 0 mM NaCl along the leaf axis from the leaf base, whereas NO₃ ⁻ concentration was lower at 120 mM NaCl. Deposition rates of all nutrients were greatest in the elongation zone. The elongation zone was the strongest sink for mineral elements in the leaf tissues. Local net deposition rates of Na⁺, Cl⁻, Ca²⁺, and Mg²⁺ (mmol · kg⁻¹ FW · h⁻¹) in the most actively elongating zone were enhanced by 120 mM NaCl, whereas for NO₃ ⁻ this was depressed. The lower supply of NO⁻ ₃ to growing leaves may be responsible for the inhibition of growth under saline conditions. Higher tissue concentrations of Na⁺ and Cl⁻ may cause ion imbalance but probably did not result in ion toxicity in the growing leaves. Potassium, Ca²⁺, Mg²⁺, total P, and total N are less plausibly responsible for the reduction in leaf growth in this study. Higher tissue K⁺ and Ca²⁺ concentrations at 120 mM NaCl are probably due to the presence of high Ca²⁺ in the soil of this study. Received: 13 March 1997 / Accepted: 9 June 1997     

Hillslope Nutrient Dynamics Following Upland Riparian Vegetation Disturbance

We investigated the effects of removing near-stream Rhododendron and of the natural blowdown of canopy trees on nutrient export to streams in the southern Appalachians. Transects were instrumented on adjacent hillslopes in a first-order watershed at the Coweeta Hydrologic Laboratory (35°03′N, 83°25′W). Dissolved organic carbon (DOC), K⁺, Na⁺, Ca²⁺, Mg²⁺, NO₃ ⁻-N, NH₄ ⁺-N, PO₄ ³⁻-P, and SO₄ ²⁻ were measured for 2 years prior to disturbance. In August 1995, riparian Rhododendron on one hillslope was cut, removing 30% of total woody biomass. In October 1995, Hurricane Opal uprooted nine canopy trees on the other hillslope, downing 81% of the total woody biomass. Over the 3 years following the disturbance, soilwater concentrations of NO₃ ⁻-N tripled on the cut hillslope. There were also small changes in soilwater DOC, SO₄ ²⁻, Ca²⁺, and Mg²⁺. However, no significant changes occurred in groundwater nutrient concentrations following Rhododendron removal. In contrast, soilwater NO₃ ⁻-N on the storm-affected hillslope showed persistent 500-fold increases, groundwater NO₃ ⁻-N increased four fold, and streamwater NO₃ ⁻-N doubled. Significant changes also occurred in soilwater pH, DOC, SO₄ ²⁻, Ca²⁺, and Mg²⁺. There were no significant changes in microbial immobilization of soil nutrients or water outflow on the storm-affected hillslope. Our results suggest that Rhododendron thickets play a relatively minor role in controlling nutrient export to headwater streams. They further suggest that nutrient uptake by canopy trees is a key control on NO₃ ⁻-N export in upland riparian zones, and that disruption of the root–soil connection in canopy trees via uprooting promotes significant nutrient loss to streams. Received 30 January 2001; accepted 25 July 2002.     

Accumulation of inorganic and organic osmolytes and their role in osmotic adjustment in NaCl-stressed vetiver grass seedlings

The accumulation of inorganic and organic osmolytes and their role in osmotic adjustment were investigated in roots and leaves of vetiver grass (Vetiveria zizanioides) seedlings stressed with 100, 200, and 300 mM NaCl for 9 days. The results showed that, although the contents of inorganic (K⁺, Na⁺, Ca²⁺, Mg²⁺, Cl⁻, NO₃⁻, SO₄²⁻ and H₂PO₃⁻)) and organic (soluble sugar, organic acids, and free amino acids) osmolytes all increased with NaCl concentration, the contribution of inorganic ions (mainly Na⁺, K⁺, and Cl⁻) to osmotic adjustment was higher (71.50–80.56% of total) than that of organic solutes (19.43–28.50%). The contribution of inorganic ions increased and that of organic solutes decreased in roots with the enhanced NaCl concentration, whereas the case in leaves was opposite. On the other hand, the osmotic adjustment was only effective for vetiver grass seedlings under moderate saline stress (less than 200 mM NaCl).     

The role of ion regulation in the control of the distribution of Gammarus tigrinus (Sexton) in salt-polluted rivers

Fluctuating salinities at different sites on the German salt-polluted rivers Werra and Weser were compared with extracellular ion levels of specimens of Gammarus tigrinus (Sexton; Amphipoda, Crustacea), collected at the same sites. G. tigrinus regulated haemolymph concentrations of inorganic anions (Cl⁻, SO²⁻ ₄, PO³⁻ ₄) and cations (Na⁺, K⁺, Mg²⁺, Ca²⁺) during fluctuations of salt pollution in the upper Weser. This capacity to regulate varying levels of salt pollution in the upper Weser, correlated well with the distribution of the brackish amphipods in this river ecosystem. G. tigrinus tolerated periods of Na⁺ and Cl⁻ stress (>380 mmol l⁻¹) without compensating these maxima by regulating extracellular Na⁺ and Cl⁻. However, during such bursts of Na⁺ and Cl⁻ stress in Werra and Weser, the ability to regulate extracellular [K⁺] at river water K⁺ stress of ≥6.0 mmol l⁻¹ may explain why this brackish species has been more successful in these rivers than its competitors like Gammarus pulex. The present investigation demonstrates that the water salinity affects the [NO⁻ ₃] in the haemolymph of G. tigrinus. With increasing hypo-osmotic stress the animals accumulate increasing amounts of NO⁻ ₃. A simultaneous increase in stream water [NO⁻ ₃] causes an additional accumulation of NO⁻ ₃ in the haemolymph. The high extent of accumulation indicates that active ion transport systems may be involved. The accumulation of NO⁻ ₃ in the haemolymph has low physiological consequences to G. tigrinus, but when hypo-osmotically stressed under anoxic conditions, nitrite formed by the reduction of nitrate may have an adverse affect on the metabolism of G. tigrinus. Accepted: 4 October 1999     

Long-term hydrochemical monitoring in an Oyasan Experimental Forest Watershed comprised of two small forested watersheds of Japanese cedar and Japanese cypress

Forest ecosystems are self-fertilizing systems, and development of forest stands depends on nutrient supply via biogeochemical cycling within the ecosystem. Therefore, it is important to clarify the nutrient cycle mediating growth and development. In addition, long-term hydrochemical monitoring is needed to understand the influence of environmental changes on biogeochemical cycling in forest ecosystems. The Oyasan Experimental Forest Watershed (OEFW) is located in the Field Museum Oyasan, the university forest of Tokyo University of Agriculture and Technology, in Gunma prefecture, Japan. OEFW comprises two small adjacent forested watersheds—A-watershed and B-watershed—with respective areas of 1.3 and 1.8 ha. A-watershed is a reestablished forest planted with sugi (Japanese cedar; Cryptomeria japonica) and hinoki (Japanese cypress; Chamaecyparis obtusa) in 1976, and has been managed intensively with fertilizer application. By contrast, B-watershed is an established forest planted with sugi and hinoki in 1907. No forest practices have been carried out except for thinning of suppressed trees in 1983. However, the sugi plantation on the lowest slope (18% of the watershed area) was cut in 2000, and sugi was replanted the following year. In this data paper, we present data on the daily precipitation, discharge, pH, and concentrations of major nutrients (Ca²⁺, Mg²⁺, K⁺, Na⁺, NH₄ ⁺, Cl⁻, NO₃ ⁻, and SO₄ ²⁻) in rainwater and stream water since November 1978. The arithmetical mean pH of precipitation, stream water in A- and B-watershed from the beginning of the monitoring to the present were 4.77 ± 0.67, 6.85 ± 0.41 and 6.88 ± 0.36 (average ± SD), respectively. The arithmetical mean concentrations in precipitation in mmol_c L⁻¹ were 0.030 ± 0.030 for Ca²⁺, 0.010 ± 0.011 for Mg²⁺, 0.009 ± 0.013 for K⁺, 0.020 ± 0.024 for Na⁺, 0.035 ± 0.041 for NH₄ ⁺, 0.026 ± 0.029 for Cl⁻, 0.033 ± 0.038 for NO₃ ⁻, and 0.046 ± 0.043 for SO₄ ²⁻. The mean concentrations in stream water in A-watershed were 0.180 ± 0.032 for Ca²⁺, 0.073 ± 0.013 for Mg²⁺, 0.018 ± 0.009 for K⁺, 0.182 ± 0.024 for Na⁺, 0.010 ± 0.010 for NH₄ ⁺, 0.060 ± 0.008 for Cl⁻, 0.111 ± 0.038 for NO₃ ⁻, and 0.074 ± 0.012 for SO₄ ²⁻; whereas for B-watershed the mean concentrations were 0.169 ± 0.025 for Ca²⁺, 0.079 ± 0.016 for Mg²⁺, 0.018 ± 0.005 for K⁺, 0.192 ± 0.026 for Na⁺, 0.010 ± 0.010 for NH₄ ⁺, 0.065 ± 0.010 for Cl⁻, 0.093 ± 0.025 for NO₃ ⁻, and 0.087 ± 0.011 for SO₄ ²⁻.     

Fifteen-year Change in Forest Floor Organic and Element Content and Cycling at the Turkey Lakes Watershed

To assess the long-term effects of atmospheric deposition on forest floor chemical composition, we took quantitative samplings of L-(Oi), F-(Oe), and H-(Oa) layers at an old-growth sugar maple–yellow birch stand on a till soil at the Turkey Lakes Watershed near Lake Superior, Ontario, Canada, in 1981 and 1996. We then assessed these samples for contents of organic matter (OM), total N, K, Ca, Mg, S, and Na, and exchangeable NH₄ ⁺, NO₃ ⁻, K⁺, Ca²⁺, Mg²⁺, SO₄ ²⁻, and Na⁺. Over the 15-year period, total OM and element contents remained unchanged, with the exception of N, which increased significantly from 61.3 kmol/ha in 1981 to 78.4 kmol/ha in 1996. On an area basis, there were significant increases in exchangeable Ca²⁺ (from 3.8 to 4.6 kmol/ha) and Na⁺ (from 0.05 to 0.08 kmol/ha) and decreases in exchangeable NH₄ ⁺-N (from 1.41 to 0.95 kmol/ha) and SO₄ ²⁻-S (from 1.29 to 0.96 kmol/ha). There were no significant differences in average annual litterfall OM, N, Ca, Mg, S or Na inputs between 1980 and 1985 and between 1992 and 1997. Average annual wet-only SO₄ ²⁻-S deposition during 1981–86 was 0.30; during 1992–97, it was 0.21 kmol/ha. Annual wet-only NO₃ ⁻-N averaged 0.33 kmol/ha during 1981–86 and was similar during 1992–97. Throughfall was less rich in SO₄ ²⁻ and Ca²⁺, Mg²⁺, and Na⁺ during 1992–97 than earlier. Throughfall NH₄ ⁺ and NO₃ ⁻ fluxes were unchanged. Efflux of cations from the forest floor reflected reduced throughput of SO₄ ²⁻. Overall, the results suggest that in spite of atmospheric inputs, active biological processes—including litter input, fine-root turnover, and tree uptake—serve to impart stability to the mineral composition of mature sugar maple forest floor. Received 5 October 1999; accepted 25 October 2000.     

黄河口湿地柽柳灌丛土壤盐渍化特征

为探究黄河三角洲湿地柽柳灌丛下土壤的盐渍化特征，在黄河三角洲国家级自然保护区(37°35''-12''N，118°33''-119°20''E)黄河入海口附近，根据长势基本一致的原则分别在碱蓬群落、柽柳群落和芦苇群落各选3株柽柳，采集柽柳灌丛下土壤样品，分析土壤盐分和盐碱化参数的空间分布以及距基茎不同距离处研究对象(土壤总盐(TS)、电导率(EC)、pH、交换性钠百分率(ESP))和环境因子(Na⁺、K⁺、Ca²⁺、Mg²⁺、Cl^-、HCO₃^-、SO^2-₄)之间的关系。结果表明：(1)研究区土壤为弱碱化盐土，离子含量由高到低依次为Cl^->Na⁺>SO^2-₄ >Ca²⁺>Mg²⁺>HCO^-₃>K⁺。除pH在土壤表层数值最低外，表层土壤TS、EC、ESP和盐分离子大于深层土壤，显示表聚性。(2)土壤盐分和盐碱化参数空间分布总体为：在柽柳基茎周围形成"盐谷"、"碱谷"效应， Na⁺、Mg²⁺、Cl^-表现为"盐谷"，K⁺ 、SO^2-₄ 、Ca²⁺ 表现为"盐岛"。(3)在整个土壤剖面中，与TS、EC相关性最强的阴阳离子为Mg²⁺、Cl^-，从灌丛中心到灌丛间裸地Ca²⁺、SO^2-₄与TS、EC的相关性逐渐减弱，Mg²⁺、Cl^-与TS、EC的相关性逐渐增强。Ca²⁺和SO^2-₄与pH表现为较强的负相关性；与ESP相关性最强的阴离子为HCO^-₃，与之相关性最强的阳离子为Na⁺和K⁺，并且Na⁺和K⁺与ESP的相关性表现出从灌丛中心向外逐渐增强。(4)土壤盐渍化主要受控于Na⁺，从灌丛下到灌丛间裸地Cl^-对盐渍化程度的影响逐渐增加，SO^2-₄的影响逐渐降低。     

Electrogenic Cl<Superscript>−</Superscript> secretion does not occur in the ileum of the Australian common brushtail possum, <Emphasis Type="Italic">Trichosurus vulpecula</Emphasis>, due to low levels of expression of the NaK2Cl cotransporter,NKCC1

The colon of the brushtail possum does not have an electrogenic secretory response. Given the functional significance of electrogenic Cl⁻ secretion in the intestine of eutherian mammals, we have investigated the secretory response in the small intestine of this marsupial. In the Ussing chamber cAMP-dependent secretagogues stimulated a sustained increase in ileal short-circuit current (Isc), whereas Ca²⁺-dependent secretagogues induced a transient increase. Both the responses were inhibited by mucosal addition of the anion channel blocker 5-nitro-2-(3-phenylpropylamino) benzoic acid (100 μmol l⁻¹), consistent with an anion secretory response. However, the responses were not inhibited by serosal bumetanide (10 μmol l⁻¹) and were independent of bath Cl⁻, indicating that the stimulated ileal Isc does not involve electrogenic Cl⁻ secretion driven by the NaK2Cl cotransporter, NKCC1. Consistent with this, there were low levels of NKCC1 expression in the ileal epithelium. In particular, NKCC1 expression in the ileal crypt cells was comparable to that of the villous cells. This differs from eutherian mammals where high levels of NKCC1 expression in the ileal crypt cells are associated with their role in Cl⁻ secretion. The cAMP- and Ca²⁺-dependent secretory responses were inhibited by the removal of HCO₃ ⁻ suggesting that these responses were due to electrogenic HCO₃ ⁻ secretion. We conclude that the ileum of the possum does not secrete Cl⁻ due to low levels of NKCC1 expression. It does however appear to secrete HCO₃ ⁻. These results are further significant examples of differences in the transport function of the possum intestinal epithelium compared with eutherian mammals.     

Anion uptake and acid-base and ionic effects during isolated and combined exposure to hypercapnia and nitrite in the freshwater crayfish, Astacus astacus

Nitrite influx into crayfish showed saturation kinetics, supporting a carrier-mediated uptake. Addition of 4,4′-diisothiocyanatostilbene-2,2′-disulfonate (DIDS: at 10⁻⁵, 10⁻⁴ and 10⁻³M) and bumetanide (at 10⁻⁵ M and 10⁻⁴ M) to the ambient water did not significantly affect nitrite influx. Rather than suggesting that neither Cl⁻/HCO₃ ⁻ exchange nor K⁺/Na⁺/2Cl⁻ cotransport were involved in the transport, this may reflect that the gill cuticle has a low permeability to the pharmacological agents, or that the sensitivity of the transport mechanism to the inhibitors is low. Nitrite accumulation in the haemolymph was significantly decreased during hypercapnic conditions compared to normocapnic conditions. This supports the idea that an acid–base regulatory decrease in Cl⁻(influx)/HCO₃ ⁻ (efflux) induced by hypercapnia should decrease NO₂ ⁻ uptake if NO₂ ⁻ and Cl⁻ share this uptake route. The respiratory acidosis caused by exposure to hypercapnia alone was partially compensated by HCO₃ ⁻ accumulation in the haemolymph. Combined exposure to hypercapnia and nitrite improved pH recovery, mainly by augmenting the [HCO₃ ⁻] increase, but also by decreasing haemolymph PCO₂. Exposure to nitrite in normocapnic water induced an initial increase in haemolymph [HCO₃ ⁻] and later also a decrease in PCO₂. Thus, the improved acid-base compensation during combined hypercapnia and nitrite exposure was an amplification of this nitriteinduced response. Haemolymph base excess rose much more than haemolymph [Ca], suggesting that transfer of acid-base equivalents between animal and water was more important than H⁺ buffering by exoskeletal CaCO₃ in mediating the increase in haemolymph [HCO₃ ⁻]. Accepted: 27 June 2000     

Effect of Reduced Winter Precipitation and Increased Temperature on Watershed Solute Flux, 1988–2002, Northern Michigan

Since 1987 we have studied weekly change in winter (December–April) precipitation, snowpack, snowmelt, soil water, and stream water solute flux in a small (176-ha) Northern Michigan watershed vegetated by 65–85 year-old northern hardwoods. Our primary study objective was to quantify the effect of change in winter temperature and precipitation on watershed hydrology and solute flux. During the study winter runoff was correlated with precipitation, and forest soils beneath the snowpack remained unfrozen. Winter air temperature and soil temperature beneath the snowpack increased while precipitation and snowmelt declined. Atmospheric inputs declined for H⁺, NO₃⁻, NH₄⁺, dissolved inorganic nitrogen (DIN), and SO₄²⁻. Replicated plot-level results, which could not be directly extrapolated to the watershed scale, showed 90% of atmospheric DIN input was retained in surface shallow (<15 cm deep) soils while SO₄²⁻ flux increased 70% and dissolved organic carbon (DOC) 30-fold. Most stream water base cation (C_B), HCO₃⁻, and Cl⁻ concentrations declined with increased stream water discharge, K⁺, NO₃⁻, and SO₄²⁻ remained unchanged, and DOC and dissolved organic nitrogen (DON) increased. Winter stream water solute outputs declined or were unchanged with time except for NO₃⁻ and DOC which increased. DOC and DIN outputs were correlated with the percentage of winter runoff and stream discharge that occurred when subsurface flow at the plot-level was shallow (<25 cm beneath Oi). Study results suggest that the percentage of annual runoff occurring as shallow lateral subsurface flow may be a major factor regulating solute outputs and concentrations in snowmelt-dominated ecosystems.     

Anion effects on the structural organization of spinach thylakoid membranes

Changes in the conformation of spinach thylakoid membranes were monitored in 5-doxyl stearic acid (SAL)-treated thylakoid membranes in the presence of various anions (Cl⁻, Br⁻, I⁻, NO₂ ⁻, SO₄ ²⁻, PO₄ ³⁻). The presence of anions made the thylakoid membrane more fluid. The extent of change in membrane fluidity differed with different anion and was reversible.     

Involvement of Protein Tyrosine Kinase in the InsP3-Induced Activation of Ca2+-Dependent Cl− Currents in Cultured Cells of the Rat Retinal Pigment Epithelium

This combined study of patch-clamp and intracellular Ca²⁺ ([Ca²⁺] _i ) measurement was undertaken in order to identify signaling pathways that lead to activation of Ca²⁺-dependent Cl⁻ channels in cultured rat retinal pigment epithelial (RPE) cells. Intracellular application of InsP3 (10 μm) led to an increase in [Ca²⁺] _i and activation of Cl⁻ currents. In contrast, intracellular application of Ca²⁺ (10 μm) only induced transient activation of Cl⁻ currents. After full activation by InsP3, currents were insensitive to removal of extracellular Ca²⁺ and to the blocker of I _CRAC, La³⁺ (10 μm), despite the fact that both maneuvers led to a decline in [Ca²⁺] _i . The InsP3-induced rise in Cl⁻ conductance could be prevented either by thapsigargin-induced (1 μm) depletion of intracellular Ca²⁺ stores or by removal of Ca²⁺ prior to the experiment. The effect of InsP3 could be mimicked by intracellular application of the Ca²⁺-chelator BAPTA (10 mm). Block of PKC (chelerythrine, 1 μm) had no effect. Inhibition of Ca²⁺/calmodulin kinase (KN-63, KN-92; 5 μm) reduced Cl⁻-conductance in 50% of the cells investigated without affecting [Ca²⁺] _i . Inhibition of protein tyrosine kinase (50 μm tyrphostin 51, 5 μm genistein, 5 μm lavendustin) reduced an increase in [Ca²⁺] _i and Cl⁻ conductance. In summary, elevation of [Ca] _i by InsP3 leads to activation of Cl⁻ channels involving cytosolic Ca²⁺ stores and Ca²⁺ influx from extracellular space. Tyrosine kinases are essential for the Ca²⁺-independent maintenance of this conductance. Received: 15 October 1998/Revised: 3 March 1999     

The effect of forest type on throughfall deposition and seepage flux: a review

Converting deciduous forests to coniferous plantations and vice versa causes environmental changes, but till now insight into the overall effect is lacking. This review, based on 38 case studies, aims to find out how coniferous and deciduous forests differ in terms of throughfall (+stemflow) deposition and seepage flux to groundwater. From the comparison of coniferous and deciduous stands at comparable sites, it can be inferred that deciduous forests receive less N and S via throughfall (+stemflow) deposition on the forest floor. In regions with relatively low open field deposition of atmospheric N (<10 kg N ha⁻¹ year⁻¹), lower NH₄⁺ mean throughfall (+stemflow) deposition was, however, reported under conifers compared to deciduous forest, while in regions with high atmospheric N pollution (>10 kg N ha⁻¹ year⁻¹), the opposite could be concluded. The higher the open field deposition of NH₄⁺, the bigger the difference between the coniferous and deciduous throughfall (+stemflow) deposition. Furthermore, it can be concluded that canopy exchange of K⁺, Ca²⁺ and Mg²⁺ is on average higher in deciduous stands. The significantly higher stand deposition flux of N and S in coniferous forests is reflected in a higher soil seepage flux of NO₃⁻, SO₄²⁻, K⁺, Ca²⁺, Mg²⁺ and Al(III). Considering a subset of papers for which all necessary data were available, a close relationship between throughfall (+stemflow) deposition and seepage was found for N, irrespective of the forest type, while this was not the case for S. This review shows that the higher input flux of N and S in coniferous forests clearly involves a higher seepage of NO₃⁻ and SO₄²⁻ and accompanying cations K⁺, Ca²⁺, Mg²⁺ and Al(III) into the groundwater, making this forest type more vulnerable to acidification and eutrophication compared to the deciduous forest type.     

The Occurrence,Sources and Spatial Characteristics of Soil Salt and Assessment of Soil Salinization Risk in Yanqi Basin,Northwest China

In order to evaluate the soil salinization risk of the oases in arid land of northwest China, we chose a typical oasis-the Yanqi basin as the research area. Then, we collected soil samples from the area and made comprehensive assessment for soil salinization risk in this area. The result showed that: (1) In all soil samples, high variation was found for the amount of Ca²⁺ and K⁺, while the other soil salt properties had moderate levels of variation. (2) The land use types and the soil parent material had a significant influence on the amount of salt ions within the soil. (3) Principle component (PC) analysis determined that all the salt ion values, potential of hydrogen (pHs) and ECs fell into four PCs. Among them, PC1 (C1^-, Na⁺, SO₄ ^2-, EC, and pH) and PC2 (Ca²⁺, K⁺, Mg²⁺and total amount of salts) are considered to be mainly influenced by artificial sources, while PC3 and PC4 (CO₃ ^- and HCO₃ ^2-) are mainly influenced by natural sources. (4) From a geo-statistical point of view, it was ascertained that the pH and soil salt ions, such as Ca²⁺, Mg²⁺ and HCO₃ ^-, had a strong spatial dependency. Meanwhile, Na⁺ and Cl^- had only a weak spatial dependency in the soil. (5) Soil salinization indicators suggested that the entire area had a low risk of soil salinization, where the risk was mainly due to anthropogenic activities and climate variation. This study can be considered an early warning of soil salinization and alkalization in the Yanqi basin. It can also provide a reference for environmental protection policies and rational utilization of land resources in the arid region of Xinjiang, northwest China, as well as for other oases of arid regions in the world.     

Analysis of salts transport affected by root absorption capacity in surface — irrigated fields in the upper Yellow River basin

In order to analyze the salt transport affected by roots and its effects on soil salinity in an experimental irrigated field newly established in an alluvial valley of the Yellow River in China, spatial distribution of ions contained in waters, soils and crops relevant to these phenomena were evaluated there. During the intensive surveys conducted in year 2007–2008, the Yellow River water, irrigation canal water, groundwater, field soils and crops, etc. were sampled and their chemical characteristics such as electrical conductivity, concentrations of ions Na⁺, Ca²⁺, Mg²⁺, K⁺, Cl⁻, SO₄²⁻and NO₃⁻ were measured. Irrigation seemed to cause increases in the concentrations of ions Na⁺, Cl⁻ and SO₄²⁻ in the groundwater. Although those were also major ions contained in the field soil, the soil was classed as saline but not sodic according to the standard classification. On the other hand, K⁺, which is one of the major essential nutrients for plant growth, was highly concentrated in the crops, while Na⁺ was not concentrated because of crop’s poor ability to absorb it. The ion concentration within the plant body seemed to be reflected by the active and selective ion uptake by roots and the transpiration stream. Furthermore, salt accumulation in the surface-irrigated field largely depended on the upward transport of water and ions in the soil profile affected by root absorption capacity. The information obtained in this study will contribute to the development of scientific methods for sustainable and effective plant production in irrigated fields.     

Gramicidin-Perforated Patch Analysis on HCO3 − Secretion Through a Forskolin-Activated Anion Channel in Rat Parotid Intralobular Duct Cells

Forskolin-induced anion currents and depolarization were investigated to clarify the mechanism of HCO₃ ⁻ secretion in the intralobular duct cells of rat parotid glands. Anion currents of the cells were measured at the equilibrium potential of K⁺, using a gramicidin-perforated patch technique that negligibly affects intracellular anion concentration. The forskolin-induced anion current was sustained and significantly (54%) suppressed by glibenclamide (200 μm), a blocker of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl⁻ channel. The anion current was markedly suppressed by addition of 1 mm methazolamide, a carbonic anhydrase inhibitor, and removal of external HCO₃ ⁻. Forskolin depolarized the cells in the current-clamp mode. Addition of methazolamide and removal of external HCO₃ ⁻ significantly decreased the depolarizing level. These results suggest that activation of anion channels (mainly the CFTR Cl⁻ channel located in luminal membranes) and production of cytosolic HCO₃ ⁻ induce the inward anion current and resulting depolarization. Inhibition of the Na⁺-K⁺-2Cl⁻ cotransporter and the Cl⁻-HCO₃ ⁻ exchanger had no significant effect on the current or depolarization, indicating that the uptake of Cl⁻ via the Na⁺-K⁺-2Cl⁻ cotransporter or the Cl⁻-HCO₃ ⁻ exchanger is not involved in the responses. Taken together, we conclude that forskolin activates the outward movement (probably secretion) of HCO₃ ⁻ produced intracellularly, but not of Cl⁻ due to lack of active Cl⁻ transport in parotid duct cells, and that the gramicidin-perforated patch method is very useful to analyze anion transport. Received: 17 June 2000/Revised: 14 November 2000