The influence of watershed land use on microzooplankton was examined. Six rivers and a shallow lake located in rural (agriculture, livestock) and urban areas were sampled during 4 weeks at low water, low temperatures and 3 weeks at high water, high temperatures. The major aim of this study was to analyze the composition, richness and abundance of the microzooplankton in relation to land use, taking into account nutrient concentration, biological oxygen demand (BOD5), conductivity, pH, transparency, dissolved oxygen, and chlorophyll-a. Redundancy analysis was used to assess microzooplankton response to environmental gradients. The composition and abundance can be considered good indicators of the land used and characteristic of the basin (broad range of conductivity water). The species composition show a gradient along the conductivity, pH and chlorophyll-a. Brachionus spp. were associated with saline waters on rural area and Keratella spp. (except Keratella tropica) were associated with urban water bodies. The microzooplankton abundance diminished by a factor of ten from the rivers in livestock–agriculture-dominated watersheds to those located in strictly urban areas. Urban rivers had low abundances of chlorophyll-a and microzooplankton despite the high concentration of nutrients. However, the effect of urbanization (mesotrophic/mesosaprobious state and lead presence) cannot be analyzed alone due to the potential effect of a filter-feeding invasive mollusk that colonizes the hard surfaces of harbor buildings and bridge pillars.

The levels of fluctuating asymmetry [random differences between symmetric organismal traits, fluctuating asymmetry (FA)] in the fourth instar of Chironomus spp. larvae inhabiting an agrochemical polluted river [Permatang Rawa River (PRR)] in the Juru River Basin, northeastern peninsular Malaysia, were measured. The PRR receives waters primarily from adjacent rice fields which are exposed to fertilizer and pesticide residues. Samples of larvae, water, and sediments were collected monthly from November 2007 to June 2008. In situ measurements of water pH and dissolved oxygen were made at three sampling locations along the river. Monthly water and benthic sediment collections were also conducted for the following laboratory water analyses: biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), and ammonium-N content. Non-residual metals in the sediment samples were also analyzed. The water quality index (WQI) of the PRR was also calculated. This study attempted to relate FA levels based on selected traits of Chironomus spp. larval head capsule (mentum width and first and second antennal segment length) to water quality and sediment heavy metal contamination in the PRR. All monthly measurements of FA levels including transcriptors (FA10a, FA4a, ME3, and ME1) and indices [FA, absolute asymmetry (AbsFA), and composite fluctuating asymmetry (CFA)] were calculated. The ordination model of redundancy analysis showed that the dissolved oxygen and water quality in the river expressed as WQI were negatively correlated with all FA indices (FA, AbsFA, and CFA) of the larval mentum width and length of antennal segments I and II. The water pH, BOD, and COD and sediment Cu positively influenced the FA incidence in the larval mentum. The FA indices of the antennal segment I were positively correlated with the increase in the levels of water pH, ammonium-N, BOD, and COD. The FA indices, especially CFA, were sensitive to the water pH and ammonium-N and sediment contaminated by Mn, Cu, and Zn. The FA levels calculated as FA indices of the larval antennal segment II length were positively correlated with water TSS and sediment Mn, Cu, Zn, and Ni. This study revealed that the river water quality and heavy metal contamination affect developmental stability in Chironomus spp. larvae. The FA indices of different structures in the Chironomus spp. larval head capsule could be used as bioindicators for water and sediment pollution.

Sulfonamides (SAs) are one of the broadly used antibiotics in domestic animal operations and have a notable potential of entering the environment through animal manure management practices. In this study, sulfamethazine (SMZ) was used as a prototype to study the sorption, fate, and transport of SAs in soil–water systems using batch and miscible-displacement experiments. Sulfamethazine was degraded to a polar metabolite (PM). The batch experiments indicated that the linear sorption partitioning coefficient (K d) values for the PM ranged from 7.5 to 206.2 L kg−1. Strong relationships between the sorption of PM and various soil fractions and organic matter were also observed. The miscible-displacement experiments showed that 33–70% of SMZ was degraded within 6 h during transport in the soil columns. Also, 69–99.7% of SMZ and PM were recovered in the effluents suggesting their high mobility. Also, the simultaneous degradation, sorption, and transport of SMZ and PM were described using a two-site chemical nonequilibrium fate and transport model, using the K d values obtained from the batch experiments. The parameters of this model were uniquely estimated using a global optimization strategy, the stochastic ranking evolutionary strategy.

Limited data on microbial partitioning between the freely suspended and particulate attached phases during transport along overland flow pathways have resulted in high uncertainty in bacterial fate and transport models and the application of these models to watershed management plans. The objectives of this study were to examine differences in attachment between E. coli and enterococci in runoff from plots with highly and sparsely vegetated grassland; investigate relations between flow regime, total suspended solids, and E. coli and enterococci attachment; and identify the particle size categories to which the attached cells were associated. Two rainfall simulations were conducted on large field plots 3 m wide by 18.3 m long with highly and both highly and sparsely vegetated covers and treated with standard cowpats. Results from the first experiment representing pasture with highly vegetated cover indicate that the majority of E. coli and enterococci are transported from the fresh manure source in the unattached state with only 4.8% of E. coli and 13% of enterococci associated with particles. The second experiment which compared partitioning in runoff from both highly and sparsely vegetated covers found lower bacterial attachment rates: the average E. coli percent attached was 0.06% from plots with highly vegetated cover and 2.8% from plots with sparsely vegetated cover while the corresponding values for enterococci were 0.98% and 1.23%, respectively. The findings from this study provide the first set of data on bacterial partitioning in overland flow from large field plots, and results may be helpful for parameterizing water quality models and designing conservation practices.

Nitrogen fertilizers used in agriculture often cause nitrate leaching towards shallow groundwater, especially in lowland areas where the flat topography minimize the surface run off. In order to introduce good agricultural practices that reduce the amount of nitrate entering the groundwater system, it is important to quantify the kinetic control on nitrate attenuation capacity. With this aim, a series of anaerobic batch experiments, consisting of loamy soils and nitrate-contaminated groundwater, were carried out using acetate and natural dissolved organic matter as electron donors. Acetate was chosen because it is the main intermediate species in many biodegradation pathways of organic compounds, and it is a suitable carbon source for denitrification. Sorption of acetate was also determined, fitting a Langmuir isotherm in both natural and artificially depleted organic matter soils. Experiments were performed in quadruplicate to account for the spatial variability of soil parameters. The geochemical code PHREEQC (version 2) was used to simulate kinetic denitrification using Monod equation, equilibrium Langmuir sorption of acetate, and equilibrium reactions of gas and mineral phases (calcite). The reactive modeling results highlighted a rapid acetate and nitrate mineralization rate, suggesting that the main pathway of nitrate attenuation is through denitrification while calcite acted as a buffer for pH. However, in the absence of acetate, the natural content of organic matter did not allow to complete the denitrification process leading to nitrite accumulation. Reactive modeling is thought to be an efficient and robust tool to quantify the complex biogeochemical reactions which can take place in underground environments.

Cuttings of black willow (Salix nigra), a naturally occurring wetland species, are used for restoration and streambank stabilization. As an adaptation to their wetland habitat, this species develops aerenchyma tissue to avoid root anoxia. To determine the effects of combined copper and ultraviolet-B radiation exposure on aerenchyma tissue (measured as root porosity), black willow cuttings were grown hydroponically and exposed to three ultraviolet-B (UV-B) intensities and three Cu concentrations in a completely randomized 3 × 3 factorial design. While both UV-B (F 2,42 = 11.45; p = 0.0001) and Cu (F 2,42 = 6.14; p = 0.0046) exposure increased root porosity, total biomass decreased in response to both UV-B (F 2,43 = 3.36; p = 0.0441) and to Cu (F 2,43 = 4.03; p = 0.0249). Root biomass decreased only in response to Cu (F 2,41 = 3.41; p = 0.0427) resulting in a decrease in the root/shoot ratio (F 2,42 = 3.5; p = 0.0393). Copper exposure also resulted in a decrease in the number of leaves/shoot (F 2,42 = 7.03; P = 0.0023). No UV-B and Cu interaction was found. While the present research indicates the negative effects of Cu contamination and elevated UV-B intensities on S. nigra, it also points out potential mechanisms that S. nigra uses to alleviate these stresses.

The aim of this work was to determine the optimum values for the biodegradation process of six abiotic factors considered very influential in this process. The optimisation of a polycyclic aromatic hydrocarbon (naphthalene, phenanthrene and anthracene) biodegradation process was carried out with a degrading bacterial consortium C2PL05. The optimised factors were the molar ratio of carbon/nitrogen/phosphorus (C/N/P), the nitrogen source, the iron source, the iron concentration, the pH and the carbon source. Each factor was optimised applying three different treatments during 168 h, analysing cell density by spectrophotometric absorbance at 600 nm and PAH depletion by HPLC. To determine the optimum values of the factors, an analysis of variance was performed using the cell density increments and biotic degradation constants, calculated for each treatment. The most effective values of each factor were: a C/N/P molar ratio of 100:21:16, NaNO3 as nitrogen source, Fe2(SO4)3 as iron source using a concentration of 0.1 mmol l−1, a pH of 7.0 and a mixture of glucose and PAHs as carbon source. Therefore, high concentrations of nutrients and soluble forms of nitrogen and iron at neutral pH favour the biodegradation. Also, the addition of glucose to PAHs as carbon source increased the number of total microorganism and enhanced PAH biodegradation due to the augmentation of PAH degrader microorganisms. It is also important to underline that the statistical treatment of data and the combined study of the increments of the cell density and the biotic biodegradation constant have facilitated the accurate interpretation of the optimisation results. For an optimum bioremediation process, it is very important to perform these previous bioassays to decrease the process development time and, therefore, the costs.

The adsorption of lead onto date palm fibers (palm fibers) and leaf base of palm (petiole) has been examined in aqueous solution by considering the influence of various parameters such as contact time, solution pH, adsorbent dosage, particle sizes, ionic strength, and temperature. The adsorption of Pb(II) increased with an increase of contact time. The optimal range of pH for Pb(II) adsorption is 3.0-4.5. The linear Langmuir and Freundlich models were applied to describe the equilibrium isotherms, and both models fitted well. The monolayer adsorption capacity of Pb(II) on palm fibers and petiole was found as 18.622 and 20.040 mg/g, respectively, at pH 4.5 and 25°C. Dubinin-Radushkevich (D-R) isotherm model was also applied to equilibrium data. The mean free energy of adsorption (2.397 and 4.082 kJ/mol) onto palm fibers and petiole, respectively, may be carried out via physisorption mechanism. Pseudo-first-order rate equation and pseudo-second-order rate equation were applied to study the adsorption kinetics. In comparison to first-order kinetic model, pseudo-second-order model described well the adsorption kinetics of Pb(II) onto palm fibers and petiole from aqueous solution. From the results of the thermodynamic analysis, Gibbs free energy ΔG, enthalpy change ΔH, and entropy ΔS were determined. The positive value of ΔH suggests that interaction of Pb(II) adsorbed by palm fibers is endothermic. In contrast, the negative value of ΔH indicates that interaction of Pb(II) ions by petiole is exothermic. The negative value of ΔG indicates that the adsorption of Pb(II) ions on both palm fibers and petiole is a spontaneous process.

Sulphuric acid-modified bagasse has been used as low-cost adsorbent for the removal of methylene blue (MB) dye from aqueous solution. In order to remove organic compounds that contribute to chemical oxygen demand (COD), pretreatment with thorough washing of adsorbent using boiling distilled water was performed instead of conventional washing using distilled water at room temperature only. This has resulted in the highest efficiency of color removal of 99.45% and COD reduction of 99.36% for MB dye solution at pH 9. Effects of initial pH, dye concentration, adsorbent dosage, temperature, and contact time have been studied. The adsorption of MB dye was pH dependent. Langmuir and Freundlich isotherm models were tested on the adsorption data. The kinetic experimental data were analyzed using pseudo-first order, pseudo-second order, and the intraparticle diffusion model in order to examine the adsorption mechanisms. The adsorption process followed the Langmuir isotherm as well as the Freundlich isotherm and pseudo-second-order kinetic model. The process was found to be endothermic in nature.

Brown algae Sargassum sinicola and Sargassum lapazeanum were tested as cadmium biosorbents in coastal environments close to natural and enriched areas of phosphorite ore. Differences in the concentration of cadmium in these brown algae were found, reflecting the bioavailability of the metal ion in seawater at several sites. In the laboratory, maximum biosorption capacity (q max) of cadmium by these nonliving algae was determined according to the Langmuir adsorption isotherm as 62.42 ± 0.44 mg g−1 with the affinity constant (b) of 0.09 and 71.20 ± 0.80 with b of 0.03 for S. sinicola and S. lapazeanum, respectively. Alginate yield was 19.16 ± 1.52% and 12.7 ± 1.31%, respectively. Although S. sinicola had far lower biosorption capacity than S. lapazeanum, the affinity for cadmium for S. sinicola makes this alga more suitable as a biosorbent because of its high q max and large biomass on the eastern coast of the Baja California Peninsula. Sargassum biomass was estimated at 180,000 t, with S. sinicola contributing to over 70%.