The environmental and economic consequences of nitrogen (N) lost in rice-based systems in Vietnam is important but has not been extensively studied. The objective of this study was to quantify the amount of N lost in major cropping systems in the Red River Delta. An experiment was conducted in the Red River Delta of Vietnam, on five different crops including rose, daisy, cabbage, chili, and a rice-rice-maize rotation during 2004 and 2005. Core soil samples were taken periodically in 20-cm increments to a depth of 1 m and analyzed for nitrate-nitrogen and ammonium-nitrogen. The results indicate appreciable leaching losses on N in high-rainfall and irrigation conditions, especially when fertilizer application was not well synchronized with crop N demand. Highest annual leaching losses of N were recorded in flowers with 185-190 mm of percolation and 173-193 kg N ha⁻¹, followed by vegetable (cabbage and chili) with 120-122 mm of percolation and 112-115 kg N ha⁻¹, while it was lowest in rice with about 50 kg N ha⁻¹. We developed a simple N transport model that combined water and N movement through the soil profile. In most cases, the model accurately predicted the seasonal dynamics of N as well as N flow between soil layers and the amounts of N lost from the soil profile. The simulated results of N leaching with soil “puddling” conditions illustrate the advantage of an impermeable or hardpan layer in increasing water and nutrient use efficiencies in these soils. These model results also showed that it is possible to accurately estimate N losses with only a few parameters and helped us identify the risks of N leaching.

This study proposes a two-phase optimization model for regional air pollution control. To predict the pollutant concentrations at receptor zones, an interval Gaussian plume model is advanced to facilitate the generation of optimal pollution control policies. Results from the case study indicate satisfactory performance of the proposed model in handling uncertainties in parameters expressed as intervals and in stipulations associated with pollutant emission and ambient air quality. Compared with conventional models, it has advantages of generating compromised management strategies according to decision makers' preference. This would be useful when the guarantee of satisfying all constraints is inapplicable or too costly. The proposed model is capable of identifying key factors and/or input conditions that may intensely affect system outputs and thus facilitating decision makers in adjusting current system status to benefit future management. The results also reveal a significantly enhanced satisfactory level would be obtained compared with conventional “single-phase”-based optimization models.

Bioaerosols are conglomerates of biological particles such as bacterial and fungal propagules and are produced in sewers and sewage treatment plants through evaporation and turbulence. In order to evaluate the hazard to employees in wastewater treatment plants, airborne microorganisms were measured at two different sites in the sewage systems and in the grit chamber of a treatment plant. Two additional samples were taken during high-pressure cleaning in the relief sewer. Outdoor air samples served as background values. Airborne microorganisms were collected using the impaction method with the MAS-100® and the impingement method with the SKC Biosampler®. The concentrations of coliform bacteria as well as the fungal species Aspergillus fumigatus were determined in addition to mesophilic bacteria counts (cfu/m³). The highest concentrations of mesophilic bacteria were found in the encased grit chamber. Coliform bacteria were found infrequently only in the aerosol of the sewage systems; A. fumigatus was detected at all sampling sites both indoors as well as outdoors. During high-pressure cleaning, total bacteria concentrations reached up to 4.0 × 104 cfu/m3, coliforms up to 3.0 × 103 cfu/m3. These results show that personnel protective measures should be recommended to decrease the exposure risk to biological particles.

Two species of sunflower, i.e., Tithonia diversifolia and Helianthus annuus, were investigated for their potential to remove heavy metals from contaminated soils. Dried and mature T. diversifolia (Mexican flower) seeds were collected along roadsides, while H. annuus (sunflower) seeds were sourced from the Department of PBST, University of Agriculture Abeokuta, Nigeria. The contaminants were added as lead nitrate (Pb (NO3)2) and zinc nitrate (Zn (NO3)2) at 400 mg/kg which represents upper critical soil concentration for both Pb and Zn. The results indicated that T. diversifolia mopped up substantial concentrations of Pb in the above-ground biomass compared to concentrations in the roots. The concentrations in the leaf compartment were 87.3, 71.3, and 71.5 mg/kg at 4, 6, and 8 weeks after planting (AP), respectively. In roots, it was 99.4 mg/kg, 97.4 mg/g, and 77.7 mg/kg while 79.3, 77.8, and 60.7 mg/kg were observed in the stems at 4, 6, and 8 weeks AP, respectively. Observations with H. annuus followed the pattern found with T. diversifolia, showing significant (p < 0.05) accumulation of Pb in the above-ground biomass. Results obtained from Zn contaminated soils showed significant (p < 0.05) accumulation in the above-ground compartments of T. diversifolia and H. annuus compared with root. However, the highest accumulation of Zn was observed in the leaf. The translocation factor and enrichment coefficient of Pb and Zn with these plant species are greater than 1, indicating that these metals moved more easily in these plants. However, this result also showed that the translocation of Zn from root to the shoot of the two plants was higher than Pb. In conclusion, this experiment showed that these plants accumulated substantial Pb and Zn in their shoots (leaf and stem) at 4 weeks AP which diminished with time. This implies that the efficiency of these plants in cleaning the contaminated soils was at the early stage of their growth.

Background, aim, and scope Diffusive gradients in thin films (DGT) have been recognized as a suitable tool to assess in situ metal bioavailability in soils. Mine tailings have some singular characteristics such as high heavy-metal concentrations, low pH, or absence of water retention capacity that may compromise the correct application of this technique whose applicability is known to be pH dependent. The goal of this study was to determine the response of DGT devices in heavy-metal-polluted mine tailings with different pH. In addition some experiments were performed in order to determine the effect of acidic pH and dissolved ions on the binding properties of the chelating resin. Materials and methods We tested DGT devices on three different mine tailings: acid pH 3, acid tailing limed to pH 5.5, and neutral pH 7.2. The tailings showed high metal concentrations, e.g., 7,000 mg kg⁻¹ Pb, 9,000 mg kg⁻¹ Zn, and 380 mg kg⁻¹ Cu. Diffusive and Chelex resin gels were prepared according to previously published methods. Two chelating resins and diffusive gels thicknesses (0.4 and 0.7 mm) were tested. Four DGT devices of each type were placed during 24 h in pots (one device per pot) containing 1 kg mine tailings in a climate chamber with humidity (50-90%) and controlled temperature conditions (night 16°C and day 23°C). Pots were irrigated with deionized water to field capacity, and then two different experiments were performed: (a) allowing free drainage and (b) maintaining the water saturation. In addition, we tested DGT devices in solutions at pH 3 with similar properties to the soil solution measured in the acid tailing. Eluted Zn, Cd, Pb, and Cu from the chelating resins were measured using inductively coupled plasma-optical emission spectrometer (ICP-OES; Vista-MPX Varian). Results and discussion The metal concentrations taken up by the DGT devices were affected by the different pH values of the tailings. The highest metal concentrations measured with DGT (C DGT) were obtained in the pH 3 treatments (both saturated and free drainage). Significant differences for C DGT were observed between water-saturated and free drainage treatments in the acid pH 3 tailing. When limed pH 5.5 tailing and neutral pH 7 tailing were considered, these differences were lower and not significant. In pH 3 tailings low values for C DGT/C soil solution were obtained (<0.06), indicating that these soils have a low capacity to resupply depleted metals to the solution. The limed acid tailing and the neutral tailing showed values between 0.05 and 0.94 indicating a much more rapid resupply from the solid phase. Deployment under water-saturated conditions yielded much higher C DGT values than under free drainage, indicating the importance to adequately control the moisture content in these soils with poor water retention capacity. In solutions with pH 3 mimicking the soil solution composition of the tailings, a loss of the binding capacity of the resin of 50-60% and 60-80% for Zn in 0.7-mm DGT and 0.4-mm DGT devices, respectively, was observed. As a consequence, 0.7-mm DGT devices had better reliability to carry out in situ determinations in solutions with high metal concentrations and low pH. Conclusions The use of DGT in mining soils can be a promising tool to study bioavailable metals concentrations in mine tailings but it has to be used carefully under acidic pH. Competition with other cations that are present at very high concentrations may hinder the accumulation of metals by the chelating resins, which should be tested under the conditions of the particular mine tailing.

Vegetated drainages are an effective method for removal of pollutants associated with agricultural runoff. Leersia oryzoides, a plant common to agricultural ditches, may be particularly effective in remediation; however, research characterizing responses of L. oryzoides to flooding are limited. Soil reduction resulting from flooding can change availability of nutrients to plants via changes in chemical species (e.g., increasing solubility of Fe). Additionally, plant metabolic stresses resulting from reduced soils can decrease nutrient uptake and translocation. The objective of this study was to characterize belowground and aboveground nutrient allocation of L. oryzoides subjected to various soil moisture regimes. Treatments included: a well-watered and well-drained control; a continuously saturated treatment; a 48-h pulse-flood treatment; and a partially flooded treatment in which water level was maintained at 15 cm below the soil surface and flooded to the soil surface for 48 h once a week. Soil redox potential (Eh, mV) was measured periodically over the course of the 8-week experiment. At experiment termination, concentrations of Kjeldahl nitrogen, phosphorus (P), potassium (K), iron (Fe), and manganese (Mn) were measured in plant tissues. All flooded treatments demonstrated moderately reduced soil conditions (Eh < 350 mV). Plant Kjeldahl nitrogen concentrations demonstrated no treatment effect, whereas P and K concentrations decreased in aboveground portions of the plant. Belowground concentrations of P, Mn, and Fe were significantly higher in flooded plants, likely due to the increased solubility of these nutrients resulting from the reductive decomposition of metal–phosphate complexes in the soil and subsequent precipitation in the rhizosphere. These results indicate that wetland plants may indirectly affect P, Mn, and Fe concentrations in surface waters by altering local trends in soil oxidation–reduction chemistry.

This study was carried out to test ex situ growth and soil nutrient removal efficiency of 1-year-old potted willow and poplar plants. Plants were grown under two different water regimes: low irrigation—around soil field capacity (W)—and high irrigation—five times higher than field capacity (W 5). Results showed that plant productivity and water use efficiency were greater when trees were grown in the appropriate level of soil water content rather than at excessive moisture levels. Nutrient leaching was also affected by the high irrigation treatment. However, the poplar and willow clones used in this experiment showed different nutrient allocation patterns in the plant–soil–water system. The poplar clone accumulated the highest quantities of N and P in the soil. Willow accumulated N and P mainly in the biomass due to better root development under both treatments. This indicates the better performance of the willow clone in removing N and P from contaminated aquaculture wastewaters during the first growing season.

Modern European cities are characterized by high particulate matter (PM) concentrations. Unfortunately, the number of stations monitoring air pollution, especially PM, is never sufficient for the overall representation of the problem. In the present work, an inexpensive outdoor passive sampler (based on an indoor passive sampler) was developed and assembled in an effort to provide the means to extend current PM monitoring networks. The uncertainty of the sampler was tested in vitro and in vivo. Twenty such outdoor passive samplers were assembled and installed at specific locations in the Greater Thessaloniki Area and measurements of PM were carried out. The results were in good agreement with the official monitoring stations. In addition, they revealed the aggravated air quality in the center of the city and in the west suburbs.