Binnen het Landelijk Meetnet Grondwaterkwaliteit (LMG) en de Provinciale Meetnetten Grondwaterkwaliteit (PMG) worden jaarlijks monsters genomen in enkele honderden grondwaterstandsbuizen over heel Nederland. De putten hebben filters op ca. 10 en 25 m-mv. Het doel van dit onderzoek is een beeld te geven van de grondwaterkwaliteit (en de verandering ervan in de tijd) in stedelijk gebied en van de grondwaterkwaliteit in putten met oeverinfiltratie, op basis van gegevens uit deze meetnetten. Er zijn 65 putten geselecteerd in stedelijk gebied en 34 putten met oeverinfiltratie. Beide selecties blijken een grote spreiding te hebben in grondwatersamenstelling. Om na te gaan of de grondwaterkwaliteit in van de twee selecties wordt beinvloed door bebouwing respectievelijk infiltrerend oppervlaktewater is voor elke put op beide diepteniveaus een vergelijking gemaakt met de dichtstbijzijnde omliggende put die niet tot een van beide selecties behoort. Voor een aantal locaties met oeverinfiltratie is bovendien een vergelijking gemaakt tussen het grondwater en het infiltrerende oppervlaktewater. Er wordt geconcludeerd dat de grondwatersamenstelling in stedelijk gebied afwijkt van de directe omgeving door onder andere hogere concentraties aan chloride, natrium, kalium, nitraat en bicarbonaat. Het grondwater in de putten met oeverinfiltratie wordt duidelijk beinvloed door infiltrerend oppervlaktewater. De veranderingen in de watersamenstelling over de periode 1984-1995 zijn significant doch gering.
Dit onderzoek in de periode 1992-1995 omvatte een twee- of meermalige bemonstering van water uit drains en sloten van circa 30 boerderijen verspreid over de zeekleigebieden van Nederland. De samenstelling van het drainwater is gebruikt voor een beschrijving van de effecten van het weer (neerslag min verdamping) en de verdeling van de verblijftijden van het water in de bodem. De uitspoeling van nitraat door drains onder bouwland is bij benadering een lineaire functie van de stikstof-belasting aan maaiveld, waarbij de aard van de bodem (zand, zavel, klei) en de grondwater-stand (Gt) bepalende factoren zijn. De uitspoeling bij diepe grondwaterstanden is 10 tot 25% van de belasting, nadat rekening is gehouden met een reductie als gevolg van de oxidatie van sulfiden en/of het voorkomen van kwel. De uitspoeling is voor grasland kleiner dan voor bouwland. Bij grasland (en de teelt van graszaad) is de uitspoeling van nitraat bij benadering een lineaire functie van de belasting, na aftrek van opname door het gewas, bodemtype en Gt. Uit het onderzoek van het drainwater in de kleigebieden blijkt dat de uitspoeling van fosfaat relatief constante concentraties aan ortho- en totaal-fosfaat oplevert, die verschillen voor bouwland (0.10 mg.l-1 als ortho-P), voor recent grasland (0.20 mg.l-1 als ortho-P) en voor oud permanent grasland (0.40 mg.l-1 als ortho-P).
Wever D; Bronswijk JJB (Rijksinstituut voor Volksgezondheid en Milieu RIVM, 1997-12-31)
The National Groundwater Quality Monitoring Network (LMG) was established in the Netherlands around 1985. Since then, groundwater samples have been taken yearly at some 400 locations. Samples are taken at two depths (about 10 m and 25 m below soil surface) and analysed in the laboratory. The intention, expressed at the LMG start, was to optimalise the network after 10 years of measurements. The objective of the optimalisation, based on the RIVM strategy and worked out in several workshops, was to maintain the LMG as a stable monitoring network, in which the relevance for policy makers would be maximal, in combination with a 50% reduction in costs and capacity. The result of the optimalisation is a new LMG sampling scheme which meets both the objective and all the pre-defined conditions, shallow filters in sandy regions are sampled every year; shallow filters in other regions are sampled every two years; deep filters are sampled every four years; shallow filters with high chloride concentrations (marine influence) are measured every four years; filters dominated by local conditions (e.g. nearby rivers and, local sources of pollution) are eliminated. In this way, the number of filters to be sampled every year has been reduced from 756 to about 350.
Groot MSM; Bronswijk JJB; Willems WJ; Haan T de; Castilho P del (Rijksinstituut voor Volksgezondheid en Milieu RIVM, 1997-12-31)
This report contains the results of the National Soil Monitoring Network of the Netherlands in 1994, the second year of sampling. The network represents a cooperative effort of the National Institute of Public Health and the Environment (RIVM), the Agriculture Economics Research Institute (LEI-DLO) and the Research Institute for Agrobiology and Soil Fertility (AB-DLO). The primary objective of the network is to identify changes in soil quality over time. The network's secondary objective is to identify the actual quality of soil and upper groundwater. Attention is focused primarily on rural areas. The monitoring program involves sampling 40 locations yearly over a period of five years. In 1993 the network started by sampling the soil and upper groundwater on 35 dairy-cattle farms in the sandy regions of the Netherlands. In 1994, 20 intensively managed cattle farms (i.e. farms with a high phosphate production) and 20 forest sites (deciduous, pine and mixed vegetation) on sandy soils were sampled. Concentrations of heavy metals, polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides and triazines in the topsoil (0-10 cm) and the litter layer of the forest sites have been reported. Concentrations of macroparameters, nutrients and heavy metals in the upper groundwater are also presented. The measured concentrations are compared with the Dutch objectives for soil and groundwater quality (target values).
Scheuter AJ; Berg R van den; Wever D (Rijksinstituut voor Volksgezondheid en Milieu RIVM, 1997-08-31)
The six-year long case study forming part of the research project 'in situ bioremediation of oil-polluted soil', in the Dutch town of Asten in the province of Noord-Brabant, was set up to realise clean-up according to target values for soil and groundwater. Although these target values were not met for all pollutants, the long duration of the remediation led to good results: 97% of the mineral oil, 98% of the petrol and 99% of the BTX have been removed. The average remaining levels of all the pollutants in the soil only exceed the target values in the layers 300-350 cm and 350-400 cm under the soil surface. In these layers the respective levels for mineral oil are 385 mg.kg-1 and 30 mg.kg-1 dry matter; for BTX these are 9 mg.kg-1 and 6 mg.kg-1 dry matter. Petrol exceeds the target value only in the layer 300-350 cm under the soil surface: here 120 mg.kg-1 dry matter is found. The average petrol concentration in the groundwater also exceeds the target value at 540 mug.l-1. The remediation brought the total mineral oil content down from 3373 kg to 107 kg, still present at the location. Of the removed 3266 kg, 330 kg was distracted with groundwater, 1327 kg converted to carbon dioxide by microorganisms and 558 kg fixated in the cell mass of the microorganisms. Probably about 1051 kg was converted in the vadoze zone. On the basis of laboratory and column studies, the results on the duration of the remediation and the resulting remaining levels are disappointing. In situ bioremediation with the use of hydrogen peroxide is concluded to be technically and financially feasible.
Scheuter AJ (Rijksinstituut voor Volksgezondheid en Milieu RIVM, 1997-09-30)
The aim of the tracer experiment, carried out in the framework of the project 'in situ bioremediation of oil polluted soil' in Asten (Noord-Brabant) at the end of the remediation on a commercial property and a tank island, was to trace to what extent the infiltrated water flowed uniformly through the soil. This was done by studying the flow paths and residence times of the groundwater from 25 withdrawals. In the remediation technique chosen, water was used to supply oxygen (in the form of hydrogen peroxide) and to bring nutrients to the location to stimulate the microbiological degradation of pollutants. Chloride was applied to the infiltration water in such doses as to bring the chloride concentration to about 400 mg.l-1. The concentration was measured daily in all 25 withdrawals. The measuring frequency was increased the moment the concentration in the withdrawal rose to 2 or 3 times a day. Breakthrough curves were determined in this way. Although large differences in withdrawals were observed at the moment of chloride breakthrough, the results in three of the areas within the location did show some similarities. The chloride concentration started to rise soon after the start of the experiment and broke through after 235 hours in the area to the east of the commercial property. In the withdrawals on the west side of the tank island no breakthrough was measured, and in some withdrawals there was not even a rise in the concentration. The differences in breakthrough times can probably be ascribed to soil characteristics, for example, the permeability. The differences in breakthrough times could explain the large differences between the concentration levels of petrol measured in the soil and concentrations of petrol in the groundwater.
Fraters B; Vissenberg HA; Boumans LJM; Haan T de; Hoop DW de (Rijksinstituut voor Volksgezondheid en Milieu RIVM, 1997-12-31)
The report documents the results of the four years of a monitoring programme started in 1992 to assess the quality of the upper groundwater in the sandy regions of the Netherlands affected by fertiliser and manure use in agriculture. This programme is a cooperative effort of the National Institute of Public Health and the Environment (RIVM) and the Agricultural Economics Research Institute (LEI-DLO). The upper 100 cm of groundwater occurring within five metres of the surface was sampled at 99 farms (80 cattle and 19 arable) situated in the central, northern, eastern and southern sandy regions of the Netherlands. The samples were analysed for chloride, nitrate, ammonium, potassium, dissolved organic carbon and phosphate (ortho and total). Taken on average, the nutrient load did not change in the study period. The groundwater characteristics, on the contrary, did change as a consequence of the increase in precipitation in the periode 1992-1995. Nitrate and chloride concentrations in the upper metre of the groundwater were halved in this period, while the phosphorus concentration doubled. The potassium and ammonium concentrations showed a slight decrease. The average nitrate concentration in the upper metre of the groundwater under farms in the sandy regions of the Netherlands in the period 1992 - 1995, corrected for precipitation deviation from average, was found to be 158 mg.l-1. This is over three times the limit value of 50 mg.l-1. More than 95% of the farms in the sandy regions have a (precipitation corrected) nitrate concentration higher than the limit value. A relationship was derived between groundwater quality on cattle farms (nitrate and potassium) and nutrient balance surplus, as well as between the percentage of silage maize and groundwater level. On arable farms no relationship could be derived because the number of farms was too small.
Scheuter AJ (Rijksinstituut voor Volksgezondheid en Milieu RIVM, 1997-09-30)
In developing in situ remediation most of the focus used to be on techniques using infiltration water to supply oxygen to the location. Later, techniques were developed in which soil was flushed with air to enhance the oxygen availability to microorganisms. The aim of the study reported here was to examine the results of remediation where soil is flushed with air, as reported in the literature, and to examine the costs of such systems. In the study these techniques were compared with water-supply systems, particularly those using hydrogen peroxide, e.g. bioremediation in Asten (Noord-Brabant). The remediation techniques which use air to supply oxygen to the soil are soil ventilation, soil vapour extraction, bioventing and air sparging. Soil ventilation and soil vapor extraction are physical remediation techniques which can be employed only in the vadoze zone for removal of low molecular organic pollutants. Bioventing removes pollutants mainly by microbiological conversions in the vadoze zone. Air sparging can be employed only in the saturated zone, where the pollutants can be stripped by air, as well as converted by microorganisms. In general, these techniques are used on sandy soils, which are very permeable. The whole range of hydrocarbons can be remediated. According to the literature, remediations were generally kept in operation for two years. At some sites high removal rates, up to 20 mg.kg-1 soil.day-1, were reached. The literature did not mention anything about the remaining levels of pollution dropping to target-value level. Although sometimes only 5% of the original amount of pollution remains in the soil, the lowest levels obtained are found just below the former B value. Therefore, the remediation levels reached should always be viewed in connection with the remediation time and the amount of pollution originally present. At the remediation site in Asten, where a water-supply system with hydrogen peroxide dosing is used, lower remaining levels were obtained after a longer remediation time. This location could problably also be remediated using a bioventing technique if the groundwater table were lowered. The remediation time would probably be shorter because oxygen would be available to a greater extent. However, the final pollution levels in the soil are expected to be higher. Due to the lower soil-water content in the pores, the mineralization process would terminate earlier. It is possible that these results would not be obtained in the vicinity of the groundwater table. Another possibility might be natural attenuation after lowering the contamination levels with an active remediation technique. The Dutch target values can be expected to be attained, but only after a very long remediation time. Bioventing appears to be the most cost-effective remediation technique available.
The export option will allow you to export the current search results of the entered query to a file. Different
formats are available for download. To export the items, click on the button corresponding with the preferred download format.
By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.
To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export.
The amount of items that can be exported at once is similarly restricted as the full export.
After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.