Variability of soil-water quality due to Tsunami-2004 in the coastal belt of Nagapattinam district, Tamilnadu

In this study, the Tsunami-caused deterioration of soil and groundwater quality in the agricultural fields of coastal Nagapattinam district of Tamilnadu state in India is presented by analyzing their salinity and sodicity parameters. To accomplish this, three sets of soil samples up to a depth of 30cm from the land surface were collected for the first six months of the year 2005 from 28 locations and the ground water samples were monitored from seven existing dug wells and hand pumps covering the study region at intervals of 3 months. The EC and pH values of both the soil and ground water samples were estimated and the spatial and temporal variability mappings of these parameters were performed using the geostatistical analysis module of ArcGIS((R)). It was observed that the spherical semivariogram fitted well with the data set of both EC and pH and the generated kriged maps explained the spatial and temporal variability under different ranges of EC and pH values. Further, the recorded EC and pH data of soil and ground water during pre-Tsunami periods were compared with the collected data and generated variability soil maps of EC and pH of the post-Tsunami period. It was revealed from this analysis that the soil quality six months after the Tsunami was nearing the pre-Tsunami scenario (EC< 1.5dSm(-1); pH<8), whereas the quality of ground water remained highly saline and unfit for irrigation and drinking. These observations were compared with the ground scenarios of the study region and possible causes for such changes and the remedial measures for taking up regular agricultural practices are also discussed.     

Analysis of the nitrifying bacterial community in BioCube sponge media using fluorescent in situ hybridization (FISH) and microelectrodes

There is growing interest in the development of more cost-effective and retrofit technologies for the upgrade and expansion of existing wastewater treatment plants with extreme space constraints. A free-floating sponge media (BioCube) process, using a 24L lab scale reactor, was operated to study the nitrification profiles and microbial community. The COD removal efficiencies were maintained, at an average of 95%, with the mixed liquor suspended solids (MLSS) inside the BioCube sponge media maintained at 12,688mg/L. The nitrification removal efficiencies were between 92% and 100%, with an average value of 99%. From the results of microelectrode measurements, the ammonium ion concentration was found to rapidly decrease from the surface of the BioCube sponge media to a depth of 2mm due to chemical reactions carried out by ammonia oxidizing bacteria (AOB) species. Multi-fluorescence in situ hybridization (FISH) has been used to investigate the spatial distributions of various microbial activities within reactors. Microbial communities were targeted using different oligonucleotide probes specific to AOB and nitrite oxidizing bacteria (NOB). There were a large number of AOB populations, but these were not uniformly distributed in the biofilm compared to the NOB populations.     

Detecting Temporal Change in Watershed Nutrient Yields

Meta-analyses reveal that nutrient yields tend to be higher for watersheds dominated by anthropogenic uses (e.g., urban, agriculture) and lower for watersheds dominated by natural vegetation. One implication of this pattern is that loss of natural vegetation will produce increases in watershed nutrient yields. Yet, the same meta-analyses also reveal that, absent land-cover change, watershed nutrient yields vary from one year to the next due to many exogenous factors. The interacting effects of land cover and exogenous factors suggest nutrient yields should be treated as distributions, and the effect of land-cover change should be examined by looking for significant changes in the distributions. We compiled nutrient yield distributions from published data. The published data included watersheds with homogeneous land cover that typically reported two or more years of annual nutrient yields for the same watershed. These data were used to construct statistical models, and the models were used to estimate changes in the nutrient yield distributions as a result of land-cover change. Land-cover changes were derived from the National Land Cover Database (NLCD). Total nitrogen (TN) yield distributions increased significantly for 35 of 1550 watersheds and decreased significantly for 51. Total phosphorus (TP) yield distributions increased significantly for 142 watersheds and decreased significantly for 17. The amount of land-cover change required to produce significant shifts in nutrient yield distributions was not constant. Small land-cover changes led to significant shifts in nutrient yield distributions when watersheds were dominated by natural vegetation, whereas much larger land-cover changes were needed to produce significant shifts when watersheds were dominated by urban or agriculture. We discuss our results in the context of the Clean Water Act.     

The Contribution of Marsh Zones to Water Quality in Dutch Shallow Lakes: A Modeling Study

Many lakes have experienced a transition from a clear into a turbid state without macrophyte growth due to eutrophication. There are several measures by which nitrogen (N) and phosphorus (P) concentrations in the surface water can be reduced. We used the shallow lake model PCLake to evaluate the effects of three measures (reducing external nutrient loading, increasing relative marsh area, and increasing exchange rate between open water and marsh) on water quality improvement. Furthermore, the contribution of different retention processes was calculated. Settling and burial contributed more to nutrient retention than denitrification. The model runs for a typical shallow lake in The Netherlands showed that after increasing relative marsh area to 50%, total phosphorous (TP) concentration in the surface water was lower than the Maximum Admissible Risk (MAR, a Dutch government water quality standard) level, in contrast to total nitrogen (TN) concentration. The MAR levels could also be achieved by reducing N and P load. However, reduction of nutrient concentrations to MAR levels did not result in a clear lake state with submerged vegetation. Only a combination of a more drastic reduction of the present nutrient loading, in combination with a relatively large marsh cover (approximately 50%) would lead to such a clear state. We therefore concluded that littoral marsh areas can make a small but significant contribution to lake recovery.     

Estimated occupational risk from bioaerosols generated during land application of class B biosolids

Some speculate that bioaerosols from land application of biosolids pose occupational risks, but few studies have assessed aerosolization of microorganisms from biosolids or estimated occupational risks of infection. This study investigated levels of microorganisms in air immediately downwind of land application operations and estimated occupational risks from aerosolized microorganisms. In all, more than 300 air samples were collected downwind of biosolids application sites at various locations within the United States. Coliform bacteria, coliphages, and heterotrophic plate count (HPC) bacteria were enumerated from air and biosolids at each site. Concentrations of coliforms relative to Salmonella and concentrations of coliphage relative to enteroviruses in biosolids were used, in conjunction with levels of coliforms and coliphages measured in air during this study, to estimate exposure to Salmonella and enteroviruses in air. The HPC bacteria were ubiquitous in air near land application sites whether or not biosolids were being applied, and concentrations were positively correlated to windspeed. Coliform bacteria were detected only when biosolids were being applied to land or loaded into land applicators. Coliphages were detected in few air samples, and only when biosolids were being loaded into land applicators. In general, environmental parameters had little impact on concentrations of microorganisms in air immediately downwind of land application. The method of land application was most correlated to aerosolization. From this large body of data, the occupational risk of infection from bioaerosols was estimated to be 0.78 to 2.1%/yr. Extraordinary exposure scenarios carried an estimated annual risk of infection of up to 34%, with viruses posing the greatest threat. Risks from aerosolized microorganisms at biosolids land application sites appear to be lower than those at wastewater treatment plants, based on previously reported literature.     

Thirty-year trends in suspended sediment in seven Lake Erie tributaries

Sediment is an important pollutant for Lake Erie and its tributaries as a carrier of other substances and as a pollutant in its own right. Environmental managers have called for major reductions in sediment loadings in Lake Erie tributaries. In this study, 30-yr (1975-2005) datasets with daily resolution are analyzed to identify and interpret trends in sediment concentrations and loads in major US tributaries to Lake Erie. The Maumee and Sandusky Rivers in agricultural northwest Ohio show continual decreases throughout this period, but the River Raisin shows increases, especially in the last decade. The urban and forested Cuyahoga River shows little trend before 2000 but shows increases since then. The mostly forested Grand River shows strong decreases before 1995, little change thereafter until the early 2000s, and then increases. In most cases, the greatest decreases or smallest increases, depending on the river, are associated with summer and fall and with low flow conditions, whereas the smallest decreases or greatest increases are associated with the spring and with high flow conditions. Analysis of concentration-flow relationships indicates that these changes are not due to weather but reflect positive and negative anthropogenic influences. Sediment decreases in the northwestern Ohio tributaries seem to reflect the successful use of agricultural practices to reduce erosion and prevent sediment loss. Opportunities for further reductions in sediment loads and concentrations lie in better management of sediment losses during winter and spring.     

Co-digestion of animal slurry can increase short-term nitrogen recovery by crops

Co-digestion changes slurry characteristics and is supposed to increase short-term nitrogen (N) uptake by crops after application. A higher N uptake from slurry reduces the need for additional mineral N fertilizer. If farmers apply co-digested slurry (CS), a higher N recovery has to be taken into account to prevent losses to the environment. Since data on the effects of co-digestion on N recovery by crops are scarce, a pot experiment was performed. The apparent N recovery (ANR) of five different co-digested pig slurries was compared with their raw source slurries (RS) during 105 d after a single fertilization of ryegrass (Lolium perenne L.), grown under controlled conditions. Slurry was mixed with sandy soil and grass was cut every 35 d. The results show that co-digestion increased (p < 0.05) the ANR at first cut on average from 39 to 50%, at second cut from 7 to 9% (p < 0.05), and had no effect on ANR at third cut (3%). The ANR increase at first cut was likely due to an increase of the NH(4)-N/total N ratio along with a decrease of the organic C/total N ratio of slurry during co-digestion. Field application may under certain circumstances decrease N fertilizer value of CS, due to a higher NH(3) emission compared to RS. A potential ANR increase may then be reduced, absent, or even become a decrease. Under comparable NH(3) emissions, however, CS can in the short term be more valuable as an N fertilizer than RS, and fertilizer savings can likely be realized.     

Atrazine and alachlor transport in claypan soils as influenced by differential antecedent soil water content

Increased attention to ground water contamination has encouraged an interest in mechanisms of solute transport through soils. Few studies have investigated the effect of the initial soil water content on the transport and degradation of herbicides for claypan soils. We investigated the effect of claypan soils at initial field capacity vs. permanent wilting level on atrazine and alachlor transport. The soil studied was Mexico silt loam (fine, smectitic, mesic Aeric Vertic Epiaqualf) with a subsoil clay content, primarily montmorillonite, of >40%. Strontium bromide, atrazine, and alachlor were applied to plots; half were at field capacity (Wet treatment), and half were near the permanent wilting point (Dry treatment). Soil cores were removed at selected depths and times, and cores were analyzed for bromide and herbicide concentrations. Bromide, atrazine, and alachlor were detected at the 0.90-m depth in dry plots within 15 d after experiment initiation. Bromide was detected 0.15 m deeper (P < 0.05) in the Dry compared with the Wet treatment at 1, 7, and 60 d after application and >0.30 m deeper (P < 0.01) in the Dry treatment at 15 and 30 d after application; similar treatment results were found for atrazine and alachlor, although on fewer dates with significant differences. The mobility order of the applied chemicals was bromide > atrazine > alachlor. The atrazine apparent half-life was significantly longer in the Dry plots compared with the Wet plots. The retardation factor determined from the relative velocity of each herbicide to that of bromide was higher for alachlor than for atrazine. This study identifies the impact that shrinkage cracks have for different moisture conditions on preferential transport of herbicides in claypan soils.     

Interactions between chromium and sulfur metabolism in Brassica juncea

The effects of chromate on sulfate uptake and assimilation were investigated in the accumulator Brassica juncea (L.) Czern. Seven-day-old plants were grown for 2 d under the following combination of sulfate and chromate concentration: (i) no sulfate and no chromate (-S), (ii) no sulfate and 0.2 mmol L(-1) chromate (-S +Cr), (iii) 1 mmol L(-1) sulfate and no chromate (+S), or (iv) 1 mmol L(-1) sulfate and 0.2 mmol L(-1) chromate (+S +Cr). Despite the toxic effects exerted by chromate as indicated by altered level of reducing sugars and proteins in leaves, the growth of B. juncea was only weakly reduced by chromate, and no variation in chlorophyll a and b was measured, regardless of S availability. Chromium (Cr) was stored more in roots than in leaves, and the maximum Cr accumulation was measured in -S +Cr plants. The significant decrease of the sulfate uptake rates observed in Cr-treated plants was accompanied by a repression of the root low-affinity sulfate transporter (BjST1), suggesting that the transport of chromate in B. juncea may involve sulfate carriers. Once absorbed, chromate induced genes involved in sulfate assimilation (ATP-sulfurylase: atps6; APS-reductase: apsr2; Glutathione synthethase: gsh2) and accumulation of cysteine and glutathione, which may suggest that these reduced S compounds play a role in Cr tolerance. Together, our findings indicate that when phytoremediation technologies are used to recover Cr-contaminated areas, the concentration of sulfate in the plant growth medium must be considered because it may influence the ability of plants to accumulate and tolerate Cr.     

Sorption of the veterinary antimicrobials sulfadimethoxine and ormetoprim in soil

Currently, limited research on the fate of antimicrobials in the environment exists, once they are discharged in human and animal wastes. Sorption of two antimicrobials, sulfadimethoxine (SDM) and ormetoprim (OMP), was investigated in two soils and sand using a series of batch experiments. Because OMP and SDM are often administered in combination, their sorption was also investigated in combination as co-solutes. The rate of SDM and OMP sorption was rapid over the first few hours of the experiments, which then slowed considerably after 16 to 68 h. OMP sorption was enhanced at high concentrations when in combination with SDM, with linear sorption coefficients ranging from 1.3 to 58.3 L.kg(-1) in the single solute experiments and 4.96 to 89.7 L.kg(-1) in the co-solute experiments. Sorption of OMP as a single solute seems to provide a better fit with the Freundlich equation, which became more linear (n approached 1) when SDM was present. Overall, SDM sorbed less than OMP in the two soils and sand. SDM linear sorption coefficients ranged from 0.4 to 25.8 L.kg(-1) as a single solute and 2.5 to 22.1 L.kg(-1) as a co-solute. Sorption of SDM becomes more nonlinear (n < 1) when SDM is present in combination with OMP. Overall, sorption of both antimicrobials increased in the selected soils and sand as the organic matter, clay content, and cation exchange capacity increased. These experiments indicate relatively low sorption of SDM and OMP in natural soils, making them a potential threat to surface and ground water.