Siderophores are small molecular weight extracellular organic compounds secreted by microorganisms under iron-starved conditions, used by them to chelate and solubilize iron. Though they are specific ferric iron chelator, but is reported that they bind other metals also, such as divalent heavy metals and actinides because of potentially high metal-siderophore stability constants. Thus metal contaminant fate and transport in subsurface environment can be heavily influenced by siderophores. This approach can be successfully used in removing many toxic metals off the soil which poses a serious health threat. Our research focuses on the correlation between cell growth and siderophore production and chemical characterization of the siderophore type. Its also documents the development of an assay method for the screening of different metals for complexation with siderophores based on the Chrome Azurol S (CAS) assay. The present research aims at batch scale mobilization of arsenic from arsenic contaminated soils using siderophore produced by P. azotoformans and thus evaluating its efficiency as compared to Ethylene Diamine Tetra Acetic Acid (EDTA), Citric Acid (CA) for the same. FT-IR spectroscopic studies were carried out to determine the interaction between soil, arsenic and siderophore. Results have shown that the cell growth and siderophore production are inversely related. Characterization of siderophore produced by P. azotoformans has revealed that it is of mixed-type catecholate and hydroxamate. Siderophore was found to complex with heavy metals like Cadmium, Lead, Nickel, Arsenic (III, V), Aluminium, Magnesium Zinc, Copper, Cobalt, Strontium other than Iron. Five washings by siderophore, EDTA, CA removed almost 92.8%, 77.3%, 70.0% arsenic respectively as compared to only 33.8% removal by control. Washing of arsenic contaminated soil with tap water revealed that ≈ 65.8% of arsenic in contaminated soil is in freely available or weakly bound form. The IR spectra revealed that hydrogen bonding exists between siderophore, arsenic and soil. Encouraging results of arsenic removal by biomolecule-siderophore can lead to an emerging tool brimming with opportunities for environmental clean up.

Solids and phosphorus found within urban stormwater have the potential to cause environmental damage to ecological systems in receiving waters. The evaluation of these pollutants in urban stormwater is usually undertaken by physico-chemical monitoring programs which sample streamflow for laboratory assessment. In this study, data from two such monitoring programs have been examined for the catchment characteristics which influence solids and phosphorus discharge behaviour and the potential for the use of surrogate indicators to predict streamflow concentrations. The study involved partitioning of the components on the basis of the dissolved and particulate fractions. Investigation of the physical and chemical behaviour of solids and phosphorus by univariate and multivariate data analysis techniques led to the identification of interrelationships among the measured parameters. Thus, using turbidity and conductivity, relationships were developed for suspended and dissolved solids. Similarly, relationships were developed for dissolved and particulate phosphorus using suspended and dissolved solids. These relationships have the potential to enhance rapid generation of vital information from site-based measurements and to reduce the requirements for laboratory-based analysis of indicator concentrations in urban stormwater.

In freshwater environments direct biological effect of ultraviolet radiation (UVR) result from absorption of specific wavelengths by macromolecules and alteration of biochemical processes. Indirect effects are related to UVR interaction with water and dissolved organic carbon to form chemically reactive species (ROS: reactive oxygen species). Zooplankton photoprotection includes mycosporine-like amino acids, pigments, production of quenching agents and antioxidant enzymes. The relative importance of each mechanism would depend on the organisms. In this study, we determined the antioxidant enzyme activities Catalase (CAT) and Glutathione-S-transferase (GST) in the copepod Boeckella gracilipes and the cladoceran Ceriodaphnia dubia in three Andean lakes of the North-Patagonia region. There were differences in antioxidant enzymes expression between copepods and cladocerans. CAT was significantly higher in C. dubia than in B. gracilipes whereas GST was similar in both species. The comparison of B. gracilipes enzyme activity in the three lakes showed also differences in GST but not in CAT. DOC decreases the exposure by absorption of UVR but simultaneously acts as photosensitizer producing ROS and their successive toxic products in the surface waters. We discuss that comparisons among lakes of different DOC should be considered carefully because lake physico-chemicals parameters, as well as food web structure, will difficult any predictions on the net effect of DOC.

Numerous studies have shown that Steamboat Creek in Nevada is highly contaminated with mercury, with aqueous mercury concentrations more than two orders of magnitude greater than nearby mountain streams. One objective of this study was to determine if the new Spreadsheet-based Ecological Risk Assessment for the Fate of Mercury (SERAFM) model could be calibrated to the concentrations of unfiltered and dissolved total mercury, and unfiltered and dissolved MeHg in the water column for a reach on SBC and a related constructed wetland mesocosm for different seasons and residence times. SERAFM is a new U.S. Environmental Protection Agency steady state, single segment, mass balance mercury model that has been applied to lakes, and this study also examined the model’s applicability for modeling an arid flowing water environment in different seasons. The average combined error between observed and model-estimated mercury concentrations was 12% and 17% for the reach and mesocosm, respectively. Some recommendations are proposed that may allow SERAFM to better model flowing systems.

A 3-D biological model was developed and coupled to a hydrodynamic model, i.e., Princeton Ocean Model, to simulate the seasonal variation and budget of dissolved inorganic nitrogen, phosphate, and silicate in Jiaozhou Bay. The modeled nutrients distribution pattern is consistent with observation. Silicate, the most important limiting element for phytoplankton growth, is characterized by consumption in spring, increase in summer and autumn, and accumulation in winter, whereas dissolved inorganic nitrogen and phosphorous have increasing trend with low rates in spring, due to excessive river loads. Phytoplankton plays an important role in nutrient renewal by photosynthesis and respiration processes. During an annual cycle, 7.83 x 10³ t N, 0.28 x 10³ t P, and 3.93 x 10³ t Si are transported to the bay's outer sea, i.e., the Yellow Sea, suggesting that Jiaozhou Bay is a significant source of nutrients for the Yellow Sea. The spatial distribution of nutrients is characterized by vertically homogeneous profiles, with high concentration inside the bay and low concentration toward the bay channel. These features are mainly governed by strong turbulent mixing, fluvial influx, water exchange rate, and Yellow Sea water intrusion. Numerical experiments suggest that the government should pay enough attention to proper layout of sewage drainage.

Industrialization and urbanization along the coastal population centers have brought great changes in the land cover and material fluxes from watersheds to receiving bays and estuaries. We have embarked a multiyear research project on “Watersheds Nutrient Loss and Eutrophication of Jiaozhou Bay” for the period of 2000 to 2004, funded by the Natural Science Foundation of China to examine human influence on the marine sector of ecosystem. Jiaozhou Bay, located in the southern part of Shandong Peninsula, was selected because of the existence of long-term hydrographic and meteorological records since the 1930s and recent observations on the marine ecological variables. We have made extensive and periodic measurements on the water movement, nutrients, phytoplankton, and microbe in water column and bottom sediments. Box and 3-dimensional hydrodynamic models were developed and utilized to understand the evolution of eutrophic status with time. It was found that primary productivity has suffered from silica depletion followed by phosphate, and the dominance of large phytoplankton has been replaced by small-size communities. These ecosystem changes were brought by the changes in the relative contribution among major pathways and concentrations, owing to the human activities in the watershed. Eight articles in this volume reported various aspects of the linkage between watershed human activities and ecosystem for the Jiaozhou Bay as the initial outcome of this project.

The study of mineral components in respirable particles (particulate matter with diameter less than 10 μm, PM₁₀) in ambient air is important in understanding and improving air quality. In this study, PM₁₀ samples were collected in various areas around Beijing during 2002~2003, including an urban setting, a satellite city and a rural area. The mineralogical composition of these PM₁₀ samples was studied by X-ray diffraction (XRD), environmental scanning electron microscopy / and energy-dispersive X-ray analyzer (ESEM/EDX). The results indicated that mineral composition of PM₁₀ in different seasons and in different region varied significantly. Mineral mass concentration in Beijing PM₁₀ reached the highest percentage in the spring and fell to the lowest level in the autumn. The minerals in the spring PM₁₀ were dominated by clay minerals and quartz, followed by plagioclase, K-feldspar, calcite, dolomite, hematite, pyrite, magnesite, gypsum and laumontite as well as some unidentified materials. Fewer mineral types were collected in summer, however some new components, including K(NH₄)Ca(SO4)₂·H₂O, NH₄Cl and As₂O₃·SO₃ were noted to be present, suggesting that atmospheric chemical reaction in Beijing air were more active in summer than in other seasons. Mineral components in Beijing urban air were at a higher percentage with fewer phases than that in satellite city air. In conclusion, there was considerable variation in mineral components in PM₁₀ samples collected in different seasons and areas, which reflects the related air quality of sampling areas.

The purpose of this study is to evaluate cost-effective reduction strategies for nitrogen oxides (NO x ) in the Asian region. The source-receptor relationships of the Lagrangian “puff” model of long-range transportation, ATMOS-N, were used to calculate the wet/dry deposition of the nitrogen (N) in Asia. Critical loads of N deposition in Asia were calculated from the relationships between the critical load of sulfur (S) and balance of N in and out using the data of S critical load of RAINS-ASIA. The cost functions of N reduction of Asian countries were derived by the regression analysis with the data of cost functions of European countries used in RAINS. In order to assess the environmental impact, the gaps between N deposition and critical load of N were calculated. The emission of NO x was reduced in some cases of this model, and the changes of gaps between N deposition and critical load were observed as well as the changes of the reduction cost. It is shown that a uniform reduction of NO x emissions by countries in Asia is not cost-effective strategy.

The main factors determining the geochemical fate of copper in urban freshwaters affected by raw sewage discharges were investigated in this work. Water samples from the Iraí and Iguaçu rivers were collected monthly during a 1-year period at two points located upstream and downstream from the city of Curitiba, in Brazil. Results revealed that raw sewage discharges from the heavily urbanized area caused an enhancement of humic-coated suspended solids in the Iguaçu River. In these waters copper is predominantly associated with the humic-coated particles whereas in the Iraí River copper was found primarily in the aqueous phase. The transfer of copper from the aqueous to the solid phase changed its physical speciation along the watercourse. Thus, aspects related to the overall transport of trace metals in watercourses become an important issue to be considered in further studies concerning the effect of sewage discharges on the geochemical speciation and fate of trace metals in urban rivers.

Levels of heavy metals (chromium, copper, lead and cadmium) in water and sediments of the lower Salado River (Argentina) are presented and compared to Canadian and Argentinian environmental standards. Measurement of metal levels was performed using atomic absorption spectroscopy. In order to interpret analytical results, one way ANOVA, hierarchical cluster analysis and correlations were used. Geoaccumulation Index was used as a measure of metal pollution in sediments. There were differences between the accumulation of metals in sediments and water and the control sampling site. Heavy metals, especially chromium, copper and lead, appear to be an important problem to these freshwater environments.