Phosphorus retention in small constructed wetlands treating agricultural drainage water

The construction of artificial wetlands has become a measure increasingly applied to reduce nonpoint-source (NPS) pollution and to contribute to the restoration of eutrophic lakes and coastal waters. In a 2-yr study monitoring fluxes of particulate and dissolved phosphorus (P) in a small artificial wetland for the treatment of agricultural drainage water in Central Switzerland, water residence time was identified as the main factor controlling P retention in the system. Since most of the annual P load (62% as dissolved reactive phosphorus, DRP) was related to high discharge events, it was not average but minimum water residence time during flood events that determined the wetland's P retention. In agreement with a continuous stirred tank reactor (CSTR) model, our investigations suggest a minimum water residence time of 7 d to retain at least 50% of the bioavailable P. The investigated wetland retained only 2% of the bioavailable P, since the water residence time was shorter than 7 d during 61% of time in both years. Settling of phytoplankton rather than DRP uptake into phytoplankton limited the retention of bioavailable P. The overall retention efficiency of 23% total phosphorus (TP), corresponding to a surface related retention of 1.1 g P m(-2) yr(-1), was due to the efficient trapping of pedogenic particles.     

Hydrochemistry of urban groundwater, Seoul, Korea: the impact of subway tunnels on groundwater quality

Hydrogeologic and hydrochemical data for subway tunnel seepage waters in Seoul (Republic of Korea) were examined to understand the effect of underground tunnels on the degradation of urban groundwater. A very large quantity of groundwater (up to 63 million m³ year^− 1) is discharged into subway tunnels with a total length of 287 km, resulting in a significant drop of the local groundwater table and the abandonment of groundwater wells. For the tunnel seepage water samples (n = 72) collected from 43 subway stations, at least one parameter among pathogenic microbes (total coliform, heterotrophic bacteria), dissolved Mn and Fe, NH₄⁺, NO₃⁻, turbidity, and color exceeded the Korean Drinking Water Standards. Locally, tunnel seepage water was enriched in dissolved Mn (avg. 0.70 mg L^− 1, max. 5.58 mg L^− 1), in addition to dissolved Fe, NH₄⁺, and pathogenic microbes, likely due to significant inflow of sewage water from broken or leaking sewer pipes.Geochemical modeling of redox reactions was conducted to simulate the characteristic hydrochemistry of subway tunnel seepage. The results show that variations in the reducing conditions occur in urban groundwater, dependent upon the amount of organic matter-rich municipal sewage contaminating the aquifer. The organic matter facilitates the reduction and dissolution of Mn- and Fe-bearing solids in aquifers and/or tunnel construction materials, resulting in the successive increase of dissolved Mn and Fe. The present study clearly demonstrates that locally significant deterioration of urban groundwater is caused by a series of interlinked hydrogeologic and hydrochemical changes induced by underground tunnels.     

Levels of PCDD/F and dioxin-like PCB in Baltic fish of different age and gender

Concentrations of polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF) and polychlorinated biphenyls (PCB) in Baltic Sea fish like herring (Clupea harengus membras), sprat (Sprattus sprattus balticus), perch (Perca fluviatilis), pikeperch (Sander lucioperca) and flounder (Platichthys flesus trachurus) collected from four areas of the Estonian coastal waters are reported. All samples are studied for their relationship between the length (cm) and wet weight (g); length (cm) and age (years); lipid content and dry matter. The level of PCDD/F and PCB concentrations in younger 1-5 years old Baltic herring and sprat collected in 2002-2005 from the eastern and central parts of the Gulf of Finland, Gulf of Riga and Open Baltic Sea (Central Baltic) is related to the fish age and compared with those found in the 1990s. In addition, PCDD/F and PCB concentrations of different age groups herring, sprat, perch, pikeperch and flounder collected in 2003-2004 from the Lake Peipsi, Gulf of Finland, Gulf of Riga and Open Baltic Sea are related also to their age. Consequently, it was manifested that in older Baltic fish the concentrations of PCDD/F and PCB were higher than in the younger age groups. By the help of principle component analysis (PCA) the effect of gender on the concentrations of PCDD/F for the juvenile Baltic herring and sprat collected in 2004-2005 is investigated for the first time. It was summarized that the biological factor age plays a large role for the contamination of the fish with important toxic organohalogenated compounds such as PCDD/F.     

The use of ion exchange membranes for isotope analyses on soil water sulfate: laboratory experiments

To investigate the potential use of anion exchange membranes (plant root simulator [PRS] probes) for isotope investigations of the soil sulfur cycle, laboratory experiments were performed to examine the sulfate exchange characteristics and to determine the extent of sulfur and oxygen isotope fractionation during sulfate sorption and desorption on the probes in aqueous solutions and simulated soil solutions. The sulfate-exchange tests in aqueous solutions under varying experimental conditions indicated that the amount of sulfate exchanged onto PRS probes increased with increasing reaction time, initial sulfate concentration, and the number of probes used (= surface area), whereas the percentage of removal of available sulfate was constant irrespective of the initial sulfate concentration. The competition of nitrate and chloride in the solution lowered the amount of exchanged sulfate. The exchange experiments in a simulated soil under water-saturated and water-unsaturated conditions showed that a considerable proportion of the soil sulfate was exchanged by the PRS probes after about 10 d. There was no evidence for significant sulfur and oxygen isotope fractionation between soil sulfate and sulfate recovered from the PRS probes. Therefore, we recommend the use of PRS probes as an efficient and easy way to collect soil water sulfate for determination of its isotope composition.     

Plant-specific responses to zinc contamination in a semi-field lysimeter and on hydroponics

The species Agrostis stolonifera, Brassica napus and Trifolium repens representing different ecological strategies, were selected to study the effect of Zn contamination on Zn tolerance, uptake and accumulation patterns. Parallel tests were carried out with increasing concentrations of Zn in a semi-field lysimeter and hydroponics in the climate chamber. A significant reduction in biomass production or root length and an increase in shoot Zn concentration was observed for all species at increasing external Zn concentrations. However, shoot biomass production, Zn tolerance and Zn accumulation differed significantly among the tested species. The results in both experimental set-ups were quite similar concerning Zn tolerance and accumulation and improved the validity of the findings. The rather specific responses of the different plant species to Zn contamination interfere with the more generic approach used in risk assessment studies. Maximum amounts of Zn in shoot are not likely to cause a risk to herbivores.     

Dissolved Oxygen and Nutrient Fluxes Across the Sediment–Water Interface of the Neckar River,Germany: In Situ Measurements and Simulations

A benthic in situ flume and a 1D biogeochemical sediment model to evaluate solute fluxes across the sediment–water interface have been developed. The flume was successfully used to determine oxygen and nutrient fluxes at various locations of the Neckar River in Germany. The experimental results were linked with vertical pore water concentration profiles and independently verified with the model. By combining experimental and model results we assessed the influence of dissolved oxygen concentrations in the water column and the availability of degradable organic matter on sediment oxygen demand. The results and the derived relations can be used to parameterize the sediment module of large scale water quality models, allowing one to assess the influence of sediment–water interactions on various aspects of river water quality. Moreover, the biogeochemical sediment model can help to improve the general understanding of the processes governing solute concentrations and fluxes in sediments and across their interfaces.     

A sampler for the aseptic collection of water samples in the sea

A sampler is described which can be used for the collection of microbiological, phytoplanktological, and chemical sea-water samples. The sampler consist of a polyvinylchloride (PVC) frame on which a sterile silicone-rubber container (500 ml) is assembled. The sampler is fitted with a couple of reversing thermometers. All materials used, including the hydrographic cable and the messenger, have been tested for toxicity. The container, actuated by the messenger, fills and then is closed by a stop-cock to prevent any contamination with upper-level sea water during hauling aboard. The reversing thermometers reverse only when the sample has been taken properly. Thus, the thermometers guarantee good functioning of the sampler and supply also information on the exact depth at which the sample was collected. The device can operate at any depth and several devices can be operated in one cast. During normal operation, contamination due to microorganisms attached to the frame and container is negligible.This work was performed under the association contract Euratom-CNEN.     

Janzen-Connell effects are widespread and strong enough to maintain diversity in grasslands

Crop rotation schemes are believed to work by preventing specialist soil-borne pests from depressing the future yields of similar crops. In ecology, such negative plant-soil feedbacks may be viewed as a type of Janzen-Connell effect, which promotes species coexistence and diversity by preventing the same species from repeatedly occupying a particular site. In a controlled greenhouse experiment with 24 plant species and using soils from established field monocultures, we reveal community-wide soil-based Janzen-Connell effects between the three major functional groups of plants in temperate European grasslands. The effects are much stronger and more prevalent if plants are grown in interspecific competition. Using several soil treatments (gamma irradiation, activated carbon, fungicide, fertilizer) we show that the mechanism of the negative feedback is the buildup of soil pathogens which reduce the competitive ability of nearly all species when grown on soils they have formerly occupied. We further show that the magnitude of the change in competitive outcome is sufficient to stabilize observed fitness differences between functional groups in reasonably large communities. The generality and strength of this negative feedback suggests that Janzen-Connell effects have been underestimated as drivers of plant diversity in temperate ecosystems.     

Shrines in Central Italy conserve plant diversity and large trees

Sacred natural sites (SNS) are instances of biocultural landscapes protected for spiritual motives. These sites frequently host important biological values in areas of Asia and Africa, where traditional resource management is still upheld by local communities. In contrast, the biodiversity value of SNS has hardly been quantitatively tested in Western contexts, where customs and traditions have relatively lost importance due to modernization and secularization. To assess whether SNS in Western contexts retain value for biodiversity, we studied plant species composition at 30 SNS in Central Italy and compared them with a paired set of similar but not sacred reference sites. We demonstrate that SNS are important for conserving stands of large trees and habitat heterogeneity across different land-cover types. Further, SNS harbor higher plant species richness and a more valuable plant species pool, and significantly contribute to diversity at the landscape scale. We suggest that these patterns are related not only to pre-existent features, but also to traditional management. Conservation of SNS should take into account these specificities, and their cultural as well as biological values, by supporting the continuation of traditional management practices.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-015-0738-5) contains supplementary material, which is available to authorized users.