The impact of storm water runoff on a small urban stream

Background, aim, and scope  In urban areas, storm water runoff often transports various pollutants, some of which settle and form sediments. In order to have the comprehensive view of the ecological state of storm water runoff recipients, both water and sediments of the stream must be assessed. In the Baltic Sea Area, the Water Framework Directive & HELCOM Recommendations aim to prevent or minimise pollution caused by harmful substances arising from storm water runoff, in order to promote the ecological restoration of the Baltic Sea—one of the most vulnerable seas. The aim of the study was to investigate the toxicity of bottom sediments of a small storm water runoff recipient focusing on the potential impact of successive discharges of urban storm water. Some storm water runoff quality parameters and the toxicity of bottom sediments of recipients was studied in this research. Materials and methods  During 9 years, at four discharge points, minimum four grab samples per year at each discharge point were taken for chemical characterisation. General parameters (pH, SS, BOD₇, COD_Cr and TPH) in liquid phase samples were analysed according to standard methods. Annual limit values were taken from the Lithuanian EPA requirements for the management of storm water runoff with a focus on prevention and control of contamination. Eleven composite samples of stream bottom sediments, each consisting of ten sub-samples, were collected in 2006. Toxicity screening from sediments was performed using the plant Lepidium sativum according to modified I. Magone’s methodology (Magone I, Bioindication of phytotoxicity of transport emission. In: Kachalova O-L, Zinatne (eds) Bioindication of toxicity of transport emissions in the impact of highway emissions on natural environment. Riga, pp 108–116, 1989). The level of toxic impact of Lepidium sativum (compared to control) was assessed according to the modified method of Wang (Rev Environ Contam Toxicol 126:88–127, 1992). Results  The mean pH of urban storm water runoff does not vary much from neutral, but range values are quite different, from 4.0 up to 8.7. The highest concentration of SS reached 800 mg L⁻¹, TPH—2.4 mg L⁻¹, BOD₇—300 mg O₂ L⁻¹ and COD_Cr—1,400 mg L⁻¹. The SS was above the limit in 64% of total amount of grab samples, TPH—37%, BOD₇—41% and COD_Cr—55%. The toxicity analysis of the bottom sediments showed varying toxicity of bottom sediments along the stream. From nine analysed samples of bottom sediments, 30% had weak toxicity, 30% medium and 30% strong toxicity on the test organism plant L. sativum. There was one single sample with no toxic effects, so that the results showed that urban storm water has an unacceptable environmental impact on recipients. It was also indicated that storm water runoff discharge alone is not the potential source of toxicity of bottom sediments. The litter demonstrated a weak toxicity of bottom sediments as well. Discussion  Most local authorities do not consider storm water runoff discharges to be a matter of great concern because they believe that surface runoff arising from rainfall is still relatively clean. The study showed that the current method of monitoring storm water runoff quality by chemical analyses is not the best tool for environmental impact assessment and must be combined with toxicity tests of bottom sediments of recipients. Recommendations and perspectives  To avoid the environmental impact of storm water runoff more attention should be paid to the development and implementation of storm water runoff pollution prevention measures. The study implies that future research concerning the relationships between storm water runoff deposit characteristics and biological activities must be developed to evaluate the contamination potential of stream sediment deposits for local aquatic ecosystems. Further studies should be developed to characterise the activities of the microbial community of storm water runoff sediments, and to monitor bioremediation in situ.     

Effects of Fertigation on Pigment Pattern and Fruit Quality of cv. ‘Gala’ Apples

Fruit pigmentation in ripening cv. ‘Gala, Schniga’ apples was monitored under the influence of fertigation weekly during 21 July–31 August 2009, i.e. 34 days before and 7 days after the optimal harvest date in Slovenia. The soil was a heavy loam clay with high humus content (2.8 %) and high acidity (low pH 4.9). The spectral indices NDVI (Normalized Difference Vegetation Index) and NAI (Normalized Anthocyanin Index) were obtained by a PA 1101 on attached fruit on the transition between the ground and blush colour of the fruit surface. NAI increased slowly from 0.25 to 0.6 two weeks prior to optimum maturity. NDVI values fell from 0.9 to 0.2 before and during ripening, with significant changes starting ca. 3 weeks before and during the week after the optimum harvest date. Fertigation delayed fruit ripening viz harvest date by ca. 4 days. Fertigation delayed changes in the intensity of the fruit’s epidermal pigments, expressed as NDVI for 1 week and NAI for 4 weeks, respectively, but had no significant effect on fruit colour or NDVI and NAI values at the optimal harvest date. At this time, those fruits from the fertigated trees were firmer with a lower starch index compared with the un-fertigated control. Statistically, highly significant correlations were found (p?≤?0.01) (r?=?0.35 to r?=?0.91, R²?=?0.11–0.83) between all the studied spectral and standard parameters i.e. fruit fresh firmness, soluble solids content and starch index.     

Mechanisms of pH change in wood ant (Formica polyctena) nests

We conducted a study to determine why the pH of wood ant nest materials is typically higher than that of the surrounding forest soil. An experiment with litter bags demonstrated that the pH of litter increased significantly (after only 7 months) in ant nests. Because the food that foraging ants bring into the nest contains easily decomposed carbohydrates and basic cations (largely in the form of honeydew and prey) that can cause increases in pH, we then estimated the amount of this influ of basic cations and easily decomposed carbohydrates. Based on these estimates, we conducted a second experiment to determine whether addition of field-determined quantities of an easily decomposed carbohydrate (glucose) or a basic cation (Ca²⁺) would increase the pH of the litter in artificial ant nests in the forest. Both glucose and Ca²⁺ additions significantly increased the pH of the litter but the increase was greater with Ca²⁺. The rate of pH increase in the artificial nests was similar to the rate of increase in natural nests. According to our study, ants collect substantial amounts of mineral-enriched materials in this ecosystem, which collectively increase the pH of nest material.     

Numerical investigation of irrigation scheduling based on soil water status

Improving the sustainability of irrigation systems requires the optimization of operational parameters such as irrigation threshold and irrigation amount. Numerical modeling is a fast and accurate means to optimize such operational parameters. However, little work has been carried out to investigate the relationship between irrigation scheduling, irrigation threshold, and irrigation amount. Herein, we compare the results of HYDRUS 2D/3D simulations with experimental data from triggered drip irrigation, and optimize operational parameters. Two field experiments were conducted, one on loamy sand soil and one on sandy loam soil, to evaluate the overall effects of different potential transpiration rates and irrigation management strategies, on the triggered irrigation system. In both experiments, irrigation was controlled by a closed loop irrigation system linked to tensiometers. Collected experimental data were analyzed and compared with HYDRUS 2D/3D simulations. A system-dependant boundary condition, which initiates irrigation whenever the matric head at a predetermined location drops below a certain threshold, was implemented into the code. The experimental model was used to evaluate collected experimental data, and then to optimize the operational parameters for two hypothetical soils. The results show that HYDRUS 2D/3D predictions of irrigation events and matric heads are in good agreement with experimental data, and that the code can be used to optimize irrigation thresholds and water amounts applied in an irrigation episode to increase the efficiency of water use.     

Effects of the Polish Rootstocks P2 and P22 on Vigour,Yield and Fruit Characteristics of the Apple Cultivar ‘Gravenstein’

Abstract

The performance of the Polish rootstocks P2 and P22 under Norwegian growing conditions was evaluated over 10 years (1983–92). Tree vigour of the apple cultivar ‘Gravenstein’ on P2 and P22 was 64 and 16% of that on M9, respectively. Trees on P2 had the highest yield efficiency, but less total yield per tree than M9. Owing to very dwarfing growth, trees on P22 failed to establish a sufficient canopy and produced significantly smaller apples. P2 and P22 affected apple soluble solids in a favourable way, but did not influence fruit acidity.     

Treasuring crop wild relative diversity: analysis of success from the seed collecting phase of the ‘Adapting Agriculture to Climate Change’ project

The seed collecting phase of the ‘Adapting Agriculture to Climate Change’ project was, to the best of our knowledge, the most comprehensive crop wild relatives (CWR) collecting and conservation mission to-date and provides priceless genetic diversity for ongoing and future crop breeding efforts. The seed collecting started in 2013 and was concluded in 2019, it was carried out in 22 countries in Africa, Asia, the Americas and Europe, involving CWR taxa of 28 different crop genepools. 3002 target seed accessions of 242 taxa were collected and are currently stored long-term in the countries of collection and, in most of the cases, backed up at the Millennium Seed Bank (UK). Considering also non-target species, 3854 seed accessions were collected. For the genepools of bambara groundnut (Vigna subterranea (L.) Verdc.), barley (Hordeum L.), grass pea (Lathyrus sativus L.), sorghum (Sorghum bicolor (L.) Moench), and wheat (Triticum L.), the collecting phase was highly successful in terms of diversity of both, species and populations. Despite the overall success of the project, in our analysis we discovered several issues that were encountered in the seed collecting. In particular, comparing the initial collecting targets with the seed accessions effectively collected it emerges that: (1) some important crop genepools were characterized by a low collecting success (e.g. banana/plantain (Musa L.), potato (Solanum tuberosum L.), rice (Oryza L.), (2) genepool 1 (the most important for breeding efforts) of some crop genepools was under-collected (e.g. eggplant (Solanum L.) and sorghum), (3) some important centres of plant biodiversity (especially the Indian Subcontinent) were underrepresented in the seed collecting. This analysis can guide further collecting missions in order to fill gaps in the long-term conservation of CWR of great importance for crop improvement.

     

Soil heterogeneity at the field scale: a challenge for precision crop protection

Crop protection seldom takes into account soil heterogeneity at the field scale. Yet, variable site characteristics affect the incidence of pests as well as the efficacy and fate of pesticides in soil. This article reviews crucial starting points for incorporating soil information into precision crop protection (PCP). At present, the lack of adequate field maps is a major drawback. Conventional soil analyses are too expensive to capture soil heterogeneity at the field scale with the required spatial resolution. Therefore, we discuss alternative procedures exemplified by our own results concerning (i) minimally and non-invasive sensor techniques for the estimation of soil properties, (ii) the evidence of soil heterogeneity with respect to PCP, and (iii) current possibilities for incorporation of high resolution soil information into crop protection decisions. Soil organic carbon (SOC) and soil texture are extremely interesting for PCP. Their determination with minimally invasive techniques requires the sampling of soils, because the sensors must be used in the laboratory. However, this technique delivers precise information at low cost. We accurately determined SOC in the near-infrared. In the mid-infrared, texture and lime content were also exactly quantified. Non-invasive sensors require less effort. The airborne HyMap sensor was suitable for the detection of variability in SOC at high resolution, thus promising further progress regarding SOC data acquisition from bare soil. The apparent electrical conductivity as measured by an EM38 sensor was shown to be a suitable proxy for soil texture and layering. A survey of arable fields near Bonn (Germany) revealed widespread within-field heterogeneity of texture-related ECa, SOC and other characteristics. Maps of herbicide sorption and application rate were derived from sensor data, showing that optimal herbicide dosage is strongly governed by soil variability. A phytoassay with isoproturon confirmed the reliability of spatially varied herbicide application rates. Mapping areas with an enhanced leaching risk within fields allows them to be kept free of pesticides with related regulatory restrictions. We conclude that the use of information on soil heterogeneity within the concept of PCP is beneficial, both economically and ecologically.     

Microbial responses to fluctuation of soil aeration status and redox conditions

 The response of the microbial community to changes in aeration status, from oxic to anoxic and from anoxic to oxic, was determined in arable soil incubated in a continuous flow incubation apparatus. Soil incubated in permanently oxic (air) and/or anoxic (O₂-free N₂) conditions was used as the control. Before experiments soil was preincubated for 6 days, then aeration status was changed and glucose added. Glucose concentration, extractable C, CO₂ production, microbial biomass, pH and redox potential were determined 0, 4, 8, 12, 16, 24, 36 and 48 h after change of aeration status. If oxic conditions were changed to anoxic, the amount of glucose consumed was reduced by about 60%, and CO₂ production was 10 times lower at the end of incubation compared to the control (permanently oxic conditions). Microbial biomass increased by 114% in glucose-amended soil but did not change in unamended soil. C immobilization prevailed over C mineralization. Redox potential decreased from +627 mV to –306 mV. If anoxic conditions were changed to oxic, consumption of glucose and CO₂ evolution significantly increased, compared to permanently anoxic conditions. Microbial biomass did not change in glucose-amended soil, but decreased by 78% in unamended soil. C mineralization was accelerated. Redox potential increased from +238 to +541 mV. The rate of glucose consumption was low in anoxic conditions if soil was incubated in pure N₂ but increased significantly when incubation was carried out in a CO₂/N₂ mixture. Received: 6 January 1999