Status In Water Research Articles

Iron and Zinc status in soils, water and staple food cultivars in Itakpe, Kogi State of Nigeria

The levels of iron (Fe) and zinc (Zn) were quantitatively determined in soil and water samples as well as in staple food cultivars in Itakpe, Nigeria's major iron mining town. The survey was conducted to establish a baseline pollution index for Fe and Zn in the Itakpe environment and to evaluate the role of foods as an exogenous source of these metals among the inhabitants. Exceedingly high levels of both metals characterized the staple food cultivars in the town.

Phosphorus sorption characteristics of estuarine sediments under different redox conditions.

Phosphorus (P) plays a major role in eutrophication of aquatic systems. Estuarine sediments could function as sources or sinks for P to the overlying water column depending upon their physico-chemical characteristics. Understanding of P sorption phenomena in estuarine sediments is important in regulating the P availability in estuaries. Phosphorus sorption characteristics of sediments from the Indian River Lagoon, Florida, USA, were determined to examine the role of selected physico-chemical properties of the sediments on soluble reactive P status in estuary water. Mean equilibrium P concentrations (EPCo) of 0.75 mg L(-1) and mean P sorption maxima (Smax) of 32.2 mg kg(-1) were obtained under anaerobic conditions, compared with EPCo of 0.05 mg L(-1) and Smax of 132.7 mg kg(-1) under aerobic conditions. The higher EPCo values under anaerobic conditions and the greater Smax values under aerobic conditions were associated with amorphous and poorly crystalline iron. These results suggest that sediments enriched with amorphous and poorly crystalline forms of iron act as an excellent reservoir for P by adsorbing excessive P in aerobic sediment zones and releasing it upon burial under anaerobic conditions. This study also indicates that P compounds in sediments independently maintain equilibrium with P in solutions. Thus, heterogeneous systems like soil and sediment simply behave as a mixture of homogeneous surfaces as far as their P sorption characteristics are concerned, and hence can be successfully described by the Langmuir and Freundlich models.

Water Status and Leaf Area Production in Water‐ and Nitrogen‐Stressed Cotton

The combined effects of water and N deficits on leaf area production and water relations in cotton (Gossypium hirsutum L.) have not been investigated thoroughly. A study was conducted to evaluate the responses of leaf area production and water relations in cotton plants exposed to water and N deficits during the preflowering stage. Two N treatments‐nutrient solution with 12 mM of N (N‐supplied) and N‐free nutrient solution (N‐starved)‐were applied to plants when the third true leaf was visible. Two irrigation treatments‐daily irrigation (well watered) and no irrigation (water stressed)‐were superimposed on each N treatment once the plants were moved into the test chambers when they reached a leaf area of 0.050 ± 0.002 m2. Leaf area and leaf water and osmotic potentials were measured at the end of each day‐time period. Under well‐watered conditions, leaf turgor potential in N‐starved plants was about 0.3 kJ kg−1 lower than in N‐supplied plants. When plants were exposed to water deficits, the decline of leaf water potential relative to soil water content was greater in N‐starved plants than in N‐supplied plants. Nitrogen deficiency delayed and decreased the magnitude of osmotic potential adjustment and, therefore, reduced the capacity of leaves to maintain turgor. Water and N deficits decreased whole‐plant cumulative leaf area about 50 and 40%, respectively, through decreased daily production of mainstem and branch leaves and decreased final area of individual mainstem and branch leaves. Nitrogen deficiency induced a higher sensitivity of leaf growth inhibition to water deficits.

Ecological Fitness of Senecio vulgaris and Amaranthus retroflexus Biotypes Susceptible or Resistant to Atrazine

The study on the phototactic behavior of Daphnia carinata clone Dc42 as an indicator of chromium biotoxicity showed that the phototaxis inhibition ratio (Rpi) of D. carinata could better indicate the chromium status in water. There was a negative linear correlation between phototactic index (Ip) and Cr6+ concentration in standardized K2Cr2O7 solutions (R2=0.8089, P<0.001). The detection limit of Cr6+ by Ip was 0.056 mg x L(-1), much lower than that of LC50 or EC50, and the mean precision index for detection reached up to 5.46%, which suggested the sensitivity, precision and reliability of this method in monitoring chemicals biotoxicity.