Two Elsholtzia haichowensis S. populations, copper-tolerant (TLS) and non-tolerant (HA) ones were studied in hydroponic experiment for the nitrogen assimilation and plant growth under excess Cu conditions. The results demonstrated that there were surely the differences in nitrogen assimilation and plant growth between the two populations. Excess Cu caused evident decreases in the shoot and root biomass and root/shoot biomass ratio in HA population while no significant changes happened in TLS population. In addition, in HA population, excess Cu also induced apparent declines in activities of nitrate reductase (NR, EC 1.6.6.1) and glutamine synthetase (GS, EC 6.3.1.2) in the leaves and roots as well as the contents of nitrate, ammonium and amino acids in the roots. In TLS population, excess Cu did not significantly affect the NR activities in the leaves and roots and the nitrate content in the roots, and apparently elevated the root ammonium and amino acids contents, although it also clearly reduced the GS activities in the leaves and roots. Besides, with the addition of Cu in the culture solution, the Cu contents in the leaves and roots of the two populations markedly increased. But this increase was significantly lower in TLS population than that in HA population; the fact might be partly responsible for the relative stabilization of nitrogen assimilation in TLS population compared to that in HA population.

To rigorously assess treatment technologies and establish regulatory framework for chromate-contaminated site remediation, it is useful to know the exact chromium speciation in soil matrices. In an earlier study, Thornton, E. C., & Amonette, J. E. (1999). Hydrogen sulfide gas treatment of Cr(VI)-contaminated sediment samples from a plating-waste disposal site - implications for in-situ remediation. Environmental Science & Technology, 33, 4096-4101, reported that some chromate in the bulk particles was not accessible to gaseous reductants or solution-phase extractants, based on XANES studies. We hypothesized that part of this non-extractable chromate may reside in the structure of minerals such as calcium carbonate. To test this hypothesis, a number of calcium carbonate precipitates were prepared in the presence of various concentrations of chromate during the precipitation, which could coprecipitate chromate, or by adding chromate after the precipitation was completed. Hydrochloric acid was used to dissolve calcium carbonate and therefore extract the coprecipitated and surface attached chromate. The results showed that the coprecipitated chromate was non-extractable by hot alkaline solution or phosphate buffer, but could be solubilized by HCl in proportional to the amount of calcium carbonate dissolved. The X-ray diffraction experiments revealed that the coprecipitation of chromate with calcium carbonate had an influence on its crystal structure: The higher the chromate concentration, the greater the ratio of vaterite to calcite.

On the coastal plains of Finland there are approximately 3,000 km² of acid sulfate soils developed as a result of intensive agricultural drainage of waterlogged sulfide-bearing sediments. The runoff from these soils contains very high amounts of acidity and metals that have severely deteriorated the aquaculture in several downstream rivers and estuaries. Therefore, there is an urgent need to develop and test more environmental friendly ways of draining landscapes underlain with these nasty soils. In this study, over a 3-year monitoring period the effect of excess surface liming, controlled drainage and lime filter drainage of acid sulfate soils on runoff water quality (pH, sulfate, metals) was determined and assessed. The results showed that (1) the liming measures had not prevented severely acidic and metal-rich waters from forming and discharging from the soils, (2) the controlled drainage system might have reduced discharge peaks but its potential effects on the discharged water quality were nondetectable due to its small effect on the groundwater level and naturally inherited heterogeneities, and (3) the spatial and temporal variations identified for the various hydrochemical determinants were not caused by the kind of treatment applied. Therefore, on acid sulfate soil fields, like the one studied here, the short-term hydrochemical effects of the treatments tested are minor (or nonexistent) at least as long as the controlled drainage systems are not technically improved or better maintained.

Clinoptilolite is investigated as a possible regenerable sorbent for acid rock drainage based on its adsorption capacity for Zn, adsorption kinetics, effect of pH, and regeneration performance. Adsorption of Zn ions depends on the initial concentration and pH. Adsorption/Desorption of Zn reached 75% of capacity after 1–2 h. Desorption depended on pH, with an optimum range of 2.5 to 4.0. The rank of desorption effectiveness was EDTA > NaCl > NaNO₃ > NaOAc > NaHCO₃ > Na₂CO₃ > NaOH > Ca(OH)₂. For cyclic absorption/desorption, adsorption remained satisfactory for six to nine regenerations with EDTA and NaCl, respectively. The crystallinity and morphology of clinoptilolite remained intact following 10 regeneration cycles. Clinoptilolite appears to be promising for ARD leachate treatment, with significant potential advantages relative to current treatment systems.

Natural windbreaks have been planted around livestock shelters to improve odour dispersion without substantial knowledge of their best implementation practices. Using three groups of four trained panellists and an odour generator, the objective of the present research was to measure and compare the length of odour plumes (LOP) produced in the field in the absence of, and in the presence of four natural windbreaks exposed to various climatic conditions. During 39 mornings in August, September and December 2003, panellists observed the resulting odour plumes using hedonic tone (HT) as scale and in the afternoon, evaluated the odour concentration (OC) of the odorous air sampled at the generator. By correlating HT with to their corresponding OC, filed HT values were converted into OC units, and 2 OU m⁻³ contours were used to establish LOP. A multiple factor analysis verified the effect significance on LOP of the presence of a windbreak, of windbreak properties and of climatic conditions. While being diluted, OC decreased exponentially with HT as observed by panellists (P < 0.05). Secondly, the windbreaks significantly reduced LOP by 22% as compared to the site without a windbreak. Thirdly, the denser windbreaks had a greater impact on reducing LOP. The LOP of windbreaks with an optical porosity of 0.55 was not significantly different compared to that created in the absence of a windbreak. The wind speed, direction and ambient temperature had a strong influence on LOP while atmospheric stability, windbreak position downwind from the odour source within 60 m and odour emission rate had little impact, based on the analysis of 36 field tests in the presence of a windbreak.

Aquifer vulnerability assessments can be incorporated in groundwater contamination studies. Atmospheric pollutants as vanadium, V, can reach aquifers after soil deposition if the system is vulnerable. Vanadium concentrations were detected in soil and groundwater in Salamanca Mexico. V origin is related mainly to particulate emissions from a thermoelectric plant that is using fuel oil number 6 with high V content. To determine the V origin in groundwater, a soil and groundwater monitoring was carried out. A SINTACS vulnerability zoning was done. Vanadium in soil, emissions and groundwater is well correlated. The V input is associated to aquifer vulnerable zones.

While developing a low-sulphate system combining indirect chromate-reduction by biologically-produced hydrogen sulphide and direct biological chromate-reduction to treat chromate-bearing waters, the aim of the present work was to evaluate the influence of sulphate and H₂ starvation on chromate reduction. Chromate-reduction was performed under continuous-feed conditions in a fixed-film column bioreactor originally inoculated with a bacterial consortium containing Desulfomicrobium norvegicum, and fed with H₂. With 500 mg l-¹ of sulphate in the feed solution, total chromate-reduction was observed in the effluent whereas sulphate-reduction was strongly decreased, as also confirmed by measurements of isotopic ratios for sulphur. In the absence of sulphate, a chromate-reduction activity was still observed but was lower than in the presence of sulphate, and chromate-reduction was H₂-dependent. Molecular biology techniques revealed the composition of the bacterial population in the effluent. D. norvegicum together with other micro-organisms of the Bacteria domain were detected. They include members related to the genera Acinetobacter, Acetobacterium and Rhodocyclus. Even when sulphate-reduction was strongly decreased, the presence of sulphate enhances the efficiency of the H₂-dependent chromate-reduction. A H₂- and CO₂-consuming bacterial population may be used in a globally autotrophic process to reduce chromate at low sulphate concentration, thus avoiding excess sulphide production.

The structural features and O₂ consumption of the epipelic biofilm in streams of the Pampean plain were explored. The study was conducted in three lowland streams subjected to different anthropic disturbances. Three sampling sites were selected in different sectors of these streams considering land use intensity (high, moderate, and low). Samples of the water and of the epipelic biofilm were taken seasonally. El Pescado stream is subjected to a low level of human impact and showed lower organic matter and nutrient contents than the Rodríguez and Don Carlos streams which are subjected to moderate and high levels of human impact. The biofilm composition of the three streams was represented by cyanophytes and diatoms but with different species composition and dominance; protozoans and nematodes were the characteristic heterotrophic groups in the three streams. The Rodríguez and Don Carlos streams showed the highest abundance of organisms. Multiple regression showed that O₂ consumption, chlorophyll a and trophic index were significantly correlated with the oxygen demands. On the other hand, the Rodríguez and Don Carlos streams exhibited significant differences with the El Pescado stream in O₂ consumption, trophic index, and chlorophyll a content. Our results demonstrated that the different biological descriptors responded to environmental variables that are influenced by the different land use intensities, being chlorophyll a, abundance of organisms, and O₂ consumption the most sensitive variables to the changes water quality.

A quasi steady state respiration test based on Fick's law with a correction term for advective flux, for estimating petroleum hydrocarbon degradation rates, was evaluated in a full-scale (3,000 m³) biopile study. A contaminated clayey sand soil with an average TPH content of 1,421 ± 260 mg kg-¹ soil was treated in a biopile with a fixed venting and heating system. Temperature in the biopile ranged from 12.1 to 36.6°C and soil water content from 15.2 to 35.8 m³ H₂O m-³ soil. Oxygen concentrations in the biopile showed a rapid decrease with depth, before venting and reached constant atmospheric concentration during venting. Measured oxygen consumption in the biopile ranged from -0.04 to -0.68 mol O₂ m-³ soil day-¹. Average oxygen consumption rates calculated with the quasi-steady-state method were significantly (P < 0.05) lower then the oxygen consumption rates calculated with the transient method. It was suggested that the oxygen diffusion was underestimated by the diffusivity models used and that further research is needed to determine relative effective diffusion coefficients in biopiles. Although both respiration testing and petroleum hydrocarbon concentration showed a decrease of oxygen consumption in time, the estimated degradation rate was low compared to the actual decrease in petroleum hydrocarbon concentration. Additional work will have to be done to acquire a more precise knowledge of the relationship between respirometrically determined degradation rates and the actual change in petroleum hydrocarbon concentration in the soil.

In this study, benthic flux measurements of inorganic nitrogen (i.e., [graphic removed] , [graphic removed] + [graphic removed] ) were made using a batch incubation system at different stations (i.e., shallow sandy macrophyte and unvegetated beds, and deep central mud) over four seasons in Lake Illawarra, NSW, Australia, to study the influence of different primary producers (i.e., seagrasses, microphytobenthos (MPB) and macroalgae) and/or different sediment types (i.e., sand or mud) on the benthic fluxes. In general, nutrient fluxes displayed typical diel variations, with lower flux out of sediments (release) or enhanced uptake by the sediment in the light, due to the photosynthetic activities of the plant-MPB-sediment community in Lake Illawarra during photosynthetic periods. A distinct seasonal pattern of inorganic-N fluxes was also observed (e.g., the marked difference between summers 2002 and 2003). This may be explained by the seasonal variations in the biomass and activity (growing or decay phases) of MPB, seagrass and macroalgae, which may influence their nutrient assimilation and alter the chemical conditions of surface sediments that influence the benthic geochemical processes and thus benthic nutrient fluxes. On an annual basis, unvegetated sediments displayed net DIN effluxes, while seagrass beds showed a net DIN uptake, and the highest DIN uptakes coincided with the largest standing crop of seagrass and/or macroalgae and the highest levels of benthic community production. This may be due to the enhanced denitrification and/or assimilation activity by rooted plants and macroalgae, and the effect is most efficient during periods of net growth (e.g., in Spring 2002).