Agricultural Diffuse Pollution Research Articles

Water quality in Scotland: the view of the regulator

Water quality in Scotland has progressively improved over the past 50 years as the environmental damage, which resulted from the industrial revolution, has been addressed. This paper provides an overview of current water quality in rivers, lochs, estuaries and coastal waters and describes the limited information available on groundwater. The main factors affecting water quality are reviewed, with sewage, diffuse agricultural pollution, acidification and urban drainage identified as the most important. Trends in pollution pressure and levels of investment in pollution control have been used to predict the condition of Scotland's surface water over the next 10 years. Major improvements are expected. However, progress will be slowed by the increased relative importance of diffuse sources of pollution, which are less amenable to legislative controls. Future changes in environmental monitoring are also expected to move the emphasis away from point source pollution. The current freshwater classification schemes are based upon a relatively narrow measure of water quality and are expected to expand to include a wider range of ecological parameters. This will result in an increase in the waters defined as impacted as the effects of other environmental pressures are taken into account. Finally the implications of these changes for the future management of the aquatic environment are assessed.

A multicriteria approach for mapping risks of agricultural pollution for water resources: The Venice Lagoon watershed case study

A multicriteria analysis system was developed for producing risk maps of agricultural pollution due to alternative cultivation systems in the Watershed of the Lagoon of Venice (WLV) in Italy. Results of a field-scale simulation model for agricultural diffuse pollution were used to compile a matrix of environmental impacts, in terms of pollution indices. The most widespread combinations of typical environments (as defined by combinations of soil and climate variables) and alternative land uses (types of crops and cultivation systems) were described in the impact matrix. Land use in terms of crop distribution was based on census data. Two alternative cultivation systems were defined on the basis of the recent changes to the European Common Agricultural Policy: ordinary and eco-compatible. The effects of alternative scenarios were evaluated in terms of pollution risks for water resources. The evaluation procedure was built into the framework of a geographical information system to take into account the spatial features of pollution phenomena, vulnerability of the land and risk for water resources. The results demonstrated the great potential of eco-compatible practices for reducing the risks for surface and groundwater (−15 and −50%, respectively).

The use of conventionally and alternatively located buffer zones for the removal of nitrate from diffuse agricultural run-off

Interest in the use of buffer zones for the protection of surface water bodies from diffuse agricultural pollution is increasing in the UK. Current protocol for buffer zone location recommends they are established adjacent to the water body, typically in the riparian zones of rivers and streams. In many situations this may be the most efficient location to deliver benefits such as habitat provision and river bank stability, though this may not necessarily be the case for effective reduction of diffuse pollution. In the UK many of these riparian locations are by-passed by drains and ditches, rendering them ineffective as buffer zones for reducing pollutant concentrations in ground water and surface water. Alternative wetland buffer zone locations have often been found to be more effective for nitrate removal. These include areas of both footslope seepage and overland flow often associated with small ditch systems, which traditionally would not be considered as buffer zones. Examples are presented of two alternative wetland buffer zones in south-west England, one situated in an area of footslope discharge, and the other on an overland flow zone associated with a ditch system. The potential efficiency of both buffer zones is examined with regard to nitrate removal.

Agricultural practices and diffuse nitrogen pollution in Denmark: empirical leaching and catchment models

An empirical leaching model was applied to data on agricultural practices at the field level within 6 small Danish agricultural catchments in order to document any changes in nitrogen (N) leaching from the root zone during the period 1989-96. The model calculations performed at normal climate revealed an average reduction in N-leaching that amounted to 30% in the loamy catchments and 9% in the sandy catchments. The reductions in N leaching could be ascribed to several improvements in agricultural practices during the study period: (i) regulations on livestock density; (ii) regulations on the utilisation of animal manure; (iii) regulations concerning application practices for manure. The average annual total N-loss from agricultural areas to surface water constituted only 54% of the annual average N leached from the root zone in the three loamy catchments and 17% in the three sandy catchments. Thus, subsurface N-removal processes are capable of removing large amounts of N leached from agricultural land. An empirical model for the annual diffuse N-loss to streams from small catchments is presented. The model predicts annual N-loss as a function of the average annual use of mineral fertiliser and manure in the catchment and the total annual runoff from the unsaturated zone.

Diffuse agricultural nitrate pollution of groundwaters in India

Nitrate pollution of groundwater due to urban waste and industrial effluents usually centres around cities. This study has shown that nitrate levels in groundwater over vast agricultural areas can be correlated with intensive irrigated agriculture, corresponding use of nitrogenous fertilizers and groundwater development, and consequent diffuse agricultural pollution has already endangered the safety of potable groundwater for future generations in both rural and urban areas. Chemical and bacterial treatment of groundwater for nitrate removal relies on advanced technology and is considered costly even in the developed world. In a country like India where economic resources are inadequate, action on the suggested preventive measures may be taken without delay at this stage when alarming trends have been recorded.

Diffuse agricultural water pollution in India

Concern over agricultural diffuse pollution sources in integrated water quality management has been growing recently. Such sources are likely to be even more critical in developing countries, including India, where agriculture and rural habitats are still dominant, unlike the G7 or other affluent industrialised nations. A number of special features of the Indian scene need to be considered. These include: (i) extremely varying rainfall and stream-flow patterns; (ii) still largely traditional agricultural practices with average application of fertilizers and pesticides and significant areas under dry farming or only marginal irrigation; (iii) a very large cattle population, with agriculture almost always linked with animal husbandry; (iv) a culture of living close to the river (if not in the river) with dominating instream uses of bathing, washing, cattle wading, waste disposal, etc. and large-scale floodplain farming; and (v) scant respect for rules, regulations and laws alongside an extremely weak law-enforcement machinery. The paper shows that in the non-monsoon (non-flood) periods, which may account for all but 2 months of a year, agricultural diffuse pollution sources seem to have no impact on stream water quality. During these periods flows are low to minimal and pollution is dominated by the in-stream uses, sullage waters of rural communities and point discharges from urban/industrial sources, if any. Pollution due to agricultural return waters, either as wash-off or as seepage, appears to be rare during the 8-10 fair weather months. However, surface wash-off of pollutants from agricultural sources becomes the dominant factor during flood flows, and seepage/drainage from agricultural fields/soils continues to pollute streams for a month or two after the monsoons are over. Application of chemical fertilizers and pesticides (or any other agricultural chemicals) in India is still low compared to developed countries, and while eutrophication due to high levels of washed-off nutrients is observed in rural ponds and other stagnant bodies of water receiving agricultural drainage, and excessive pesticide residuals are often reported for vegetables, fodder, milk, etc., monitoring of streams and rivers does not show any significant pollution due to nutrients or pesticides from agricultural diffuse pollution during fair weather months. High nitrate concentrations have been reported in groundwater and in many areas, such as Punjab and Haryana, these can often be linked directly to diffuse agricultural sources. The major problem of agricultural diffuse pollution appears to be the heavy silt loads, along with large quantities of dissolved salts, nutrients, organics and even heavy metals and bacterial contaminants washed off during floods. The silt tends to clog up the flow channel to further encourage seasonal floodplain agriculture. This results in a vicious circle, which degrades the channel, increases flood-damage and is undesirable from ecological and sustainability points of view. High concentrations of salts and nutrients encourage growth of weeds and macrophytes after the floods have passed. The presence of organics, heavy metals and bacterial contamination renders the streamwater unfit for in-stream use or abstraction. With the introduction of intensive agriculture and adoption of modern farming techniques involving the application of much irrigation water and agricultural chemicals, the problems caused by diffuse agricultural pollution are bound to grow. Routine pollution control methods of discharge permits (or consent letters), EIAs or environmental audits, and normal enforcement measures by regulatory agencies are not likely to work for control of such pollution. Using the example of a small river in central India, Paisuni (Mandakini), the paper brings out the nature of the problems, and suggests a possible management approach.

Agricultural diffuse pollution in Thailand

Over the past two decades there have been a number of changes in Thailand, changes in the environment and quality of life for its people, changes in its communities and in the foundations of its economy. Before 1970, Thailand was a rural society in which local communities depended on the natural resources which surrounded them, and the national economy relied on the export of native crops. The sustainable use of resources was a fundamental aspect of rural life, people understood the interrelationships between the different components of their local environment and their activities which were defined by the need to protect their surrounding resources. Agriculture is the major profession and source of income for the rural poor. Land degradation and soil depletion result in low crop yields and pollution of the environment; soil erosion and landslides are found in Thailand. Nutrient uptake by crops and loss by leaching is much greater than the nutrients applied. Hence soils become less productive and it results in more land requirement for food production. Forest land declines rapidly in hilly watershed areas. Thailand is located in a tropical region and European countries are located in a temperate region. The climate is completely different, the temperature during summer in some European countries is probably almost the same as winter in Thailand. Not only is the climate in the two regions different, but land use and soil type are different also. These parameters have to be considered when studying the impact of agricultural diffuse pollution on the environment. Research studies on agricultural diffuse pollution in water resources in Thailand show that nutrient loads and pesticide residues still do not exceed the standard level. However, there was a trend showing the increase of N-NO3 in water resources, in short-term monitoring of nutrients in the east of Thailand between 1988-1990 and 1993-1995. The result showed the increase of N-NO3 from 1.60 ppm to 2.54 ppm in the same watershed and landuse areas. If the use of fertilizers and pesticides in agriculture is increased without due consideration, Thailand will face the same problem as European countries.

Agricultural diffuse pollution from fertilisers and pesticides in China

Although contamination of waterbodies by nitrates and pesticides in rural regions as the main element of agricultural diffuse pollution has been gradually realised by agricultural and environmental scientists, and supported by rapidly growing pollution cases, it is still not considered a high priority environmental problem in China because of a lack of efficient monitoring programs to provide systematic analytical data. This paper brings together evidence in terms of surface water, groundwater and the agricultural ecosystem to show the current situation of water contamination related to excess applications of inorganic fertilisers and pesticides on arable land, research on the above topics, and the importance of understanding and support from both the public and government in association with further studies.

Effects of agricultural activities on water pollution with nitrates and pesticides in the Central Valley of Chile

The objectives of this study are, first, to describe the present use of fertilisers between the Regions III and VIII of Chile, identifying the associated environmental impacts and their relationship with the predominant agricultural practices and climatic characteristics. Secondly, to simulate the transport of nitrates and pesticides in a dairy and breeding farm of the Central Valley of Chile, employing EPIC (USDA/ARS) in order to determine the importance of these contamination processes. In the North area of Chile, agricultural production generates soil and groundwater salinization problems due to low average rainfall and the use of highly efficient irrigation practices. In the Central zone, nitrate contamination due to agricultural diffuse pollution is evident; this is especially valid for groundwater contamination with nitrates. The South Central area suffers from eutrophication due to an increase in the nutrient levels in surface water. The simulation indicates that the dairy farm in the Central Valley of Chile has a soil loss of 5.02 tons/ha/year or of 14.67 tons/ha/year, based on MUSS or USLE estimates, respectively. It is important to point out that loss of NO3 and pesticides estimated by MUSS and USLE do not exceed maximum allowable standards.

Diffuse agricultural water pollution in India

Concern over agricultural diffuse pollution sources in integrated water quality management has been growing recently. Such sources are likely to be even more critical in developing countries, including India, where agriculture and rural habitats are still dominant, unlike the G7 or other affluent industrialised nations. A number of special features of the Indian scene need to be considered. These include: (i) extremely varying rainfall and stream-flow patterns; (ii) still largely traditional agricultural practices with average application of fertilizers and pesticides and significant areas under dry farming or only marginal irrigation; (iii) a very large cattle population, with agriculture almost always linked with animal husbandry; (iv) a culture of living close to the river (if not in the river) with dominating instream uses of bathing, washing, cattle wading, waste disposal, etc. and large-scale floodplain farming; and (v) scant respect for rules, regulations and laws alongside an extremely weak law-enforcement machinery.The paper shows that in the non-monsoon (non-flood) periods, which may account for all but 2 months of a year, agricultural diffuse pollution sources seem to have no impact on stream water quality. During these periods flows are low to minimal and pollution is dominated by the in-stream uses, sullage waters of rural communities and point discharges from urban/industrial sources, if any. Pollution due to agricultural return waters, either as wash-off or as seepage, appears to be rare during the 8–10 fair weather months. However, surface wash-off of pollutants from agricultural sources becomes the dominant factor during flood flows, and seepage/drainage from agricultural fields/soils continues to pollute streams for a month or two after the monsoons are over.Application of chemical fertilizers and pesticides (or any other agricultural chemicals) in India is still low compared to developed countries, and while eutrophication due to high levels of washed-off nutrients is observed in rural ponds and other stagnant bodies of water receiving agricultural drainage, and excessive pesticide residuals are often reported for vegetables, fodder, milk, etc., monitoring of streams and rivers does not show any significant pollution due to nutrients or pesticides from agricultural diffuse pollution during fair weather months. High nitrate concentrations have been reported in groundwater and in many areas, such as Punjab and Haryana, these can often be linked directly to diffuse agricultural sources. The major problem of agricultural diffuse pollution appears to be the heavy silt loads, along with large quantities of dissolved salts, nutrients, organics and even heavy metals and bacterial contaminants washed off during floods. The silt tends to clog up the flow channel to further encourage seasonal floodplain agriculture. This results in a vicious circle, which degrades the channel, increases flood-damage and is undesirable from ecological and sustainability points of view. High concentrations of salts and nutrients encourage growth of weeds and macrophytes after the floods have passed. The presence of organics, heavy metals and bacterial contamination renders the streamwater unfit for in-stream use or abstraction.With the introduction of intensive agriculture and adoption of modern farming techniques involving the application of much irrigation water and agricultural chemicals, the problems caused by diffuse agricultural pollution are bound to grow. Routine pollution control methods of discharge permits (or consent letters), EIAs or environmental audits, and normal enforcement measures by regulatory agencies are not likely to work for control of such pollution. Using the example of a small river in central India, Paisuni (Mandakini), the paper brings out the nature of the problems, and suggests a possible management approach.

Diffuse agricultural nitrate pollution of groundwaters in India

Nitrate pollution of groundwater due to urban waste and industrial effluents usually centres around cities. This study has shown that nitrate levels in groundwater over vast agricultural areas can be correlated with intensive irrigated agriculture, corresponding use of nitrogenous fertilizers and groundwater development, and consequent diffuse agricultural pollution has already endangered the safety of potable groundwater for future generations in both rural and urban areas. Chemical and bacterial treatment of groundwater for nitrate removal relies on advanced technology and is considered costly even in the developed world. In a country like India where economic resources are inadequate, action on the suggested preventive measures may be taken without delay at this stage when alarming trends have been recorded.

Agricultural diffuse pollution in Thailand

Over the past two decades there have been a number of changes in Thailand, changes in the environment and quality of life for its people, changes in its communities and in the foundations of its economy. Before 1970, Thailand was a rural society in which local communities depended on the natural resources which surrounded them, and the national economy relied on the export of native crops. The sustainable use of resources was a fundamental aspect of rural life, people understood the interrelationships between the different components of their local environment and their activities which were defined by the need to protect their surrounding resources.Agriculture is the major profession and source of income for the rural poor. Land degradation and soil depletion result in low crop yields and pollution of the environment; soil erosion and landslides are found in Thailand. Nutrient uptake by crops and loss by leaching is much greater than the nutrients applied. Hence soils become less productive and it results in more land requirement for food production. Forest land declines rapidly in hilly watershed areas.Thailand is located in a tropical region and European countries are located in a temperate region. The climate is completely different. the temperature during summer in some European countries is probably almost the same as winter in Thailand. Not only is the climate in the two regions different, but land use and soil type are different also. These parameters have to be considered when studying the impact of agricultural diffuse pollution on the environment.Research studies on agricultural diffuse pollution in water resources in Thailand show that nutrient loads and pesticide residues still do not exceed the standard level. However, there was a trend showing the increase of N-N03 in water resources, in short-term monitoring of nutrients in the east of Thailand between 1988–1990 and 1993–1995. The result showed the increase of N-N03 from 1.60 ppm to 2.54 ppm in the same watershed and landuse areas. If the use of fertilizers and pesticides in agriculture is increased without due consideration. Thailand will face the same problem as European countries.

Agricultural diffuse pollution from fertilisers and pesticides in China

Although contamination of waterbodies by nitrates and pesticides in rural regions as the main element of agricultural diffuse pollution has been gradually realised by agricultural and environmental scientists, and supported by rapidly growing pollution cases, it is still not considered a high priority environmental problem in China because of a lack of efficient monitoring programs to provide systematic analytical data. This paper brings together evidence in terms of surface water, groundwater and the agricultural ecosystem to show the current situation of water contamination related to excess applications of inorganic fertilisers and pesticides on arable land, research on the above topics, and the importance of understanding and support from both the public and government in association with further studies.

The use of conventionally and alternatively located buffer zones for the removal of nitrate from diffuse agricultural run-off

Interest in the use of buffer zones for the protection of surface water bodies from diffuse agricultural pollution is increasing in the UK. Current protocol for buffer zone location recommends they are established adjacent to the water body, typically in the riparian zones of rivers and streams. In many situations this may be the most efficient location to deliver benefits such as habitat provision and river bank stability, though this may not necessarily be the case for effective reduction of diffuse pollution. In the UK many of these riparian locations are by-passed by drains and ditches, rendering them ineffective as buffer zones for reducing pollutant concentrations in ground water and surface water. Alternative wetland buffer zone locations have often been found to be more effective for nitrate removal. These include areas of both footslope seepage and overland flow often associated with small ditch systems, which traditionally would not be considered as buffer zones. Examples are presented of two alternative wetland buffer zones in south-west England, one situated in an area of footslope discharge, and the other on an overland flow zone associated with a ditch system. The potential efficiency of both buffer zones is examined with regard to nitrate removal.

Effects of agricultural activities on water pollution with nitrates and pesticides in the Central Valley of Chile

The objectives of this study are, first, to describe the present use of fertilisers between the Regions III and VIII of Chile, identifying the associated environmental impacts and their relationship with the predominant agricultural practices and climatic characteristics. Secondly, to simulate the transport of nitrates and pesticides in a dairy and breeding farm of the Central Valley of Chile, employing EPIC (USDA/ARS) in order to determine the importance of these contamination processes. In the North area of Chile, agricultural production generates soil and groundwater salinization problems due to low average rainfall and the use of highly efficient irrigation practices. In the Central zone, nitrate contamination due to agricultural diffuse pollution is evident; this is especially valid for groundwater contamination with nitrates. The South Central area suffers from eutrophication due to an increase in the nutrient levels in surface water. The simulation indicates that the dairy farm in the Central Valley of Chile has a soil loss of 5.02 tons/ha/year or of 14.67 tons/ha/year, based on MUSS or USLE estimates, respectively. It is important to point out that loss of NO3 and pesticides estimated by MUSS and USLE do not exceed maximum allowable standards.

A Case Study of Combined Sewer Overflow Pollution: Assessment of Sources and Receiving Water Effects

Abstract Combined sewer overflow (CSO) pollution was assessed in a medium size community (the Town of Malacky) in western Slovakia by means of field monitoring and computer modelling. CSO samples were analyzed for suspended solids, total chemical oxygen demand, 5-day biochemical oxygen demand, total organic carbon, heavy metals (Cu, Zn, Ni, Cd, Pb), and biological and microbiological constituents. Study results identified CSOs as a major source of biodegradable organic pollution impacting on dissolved oxygen in the receiving streams. Cumulative effects of CSO discharges were also observed in the receiving streams, in the form of high organic content of benthic sediments, which indicated the deposition of wastewater-derived sediments flushed out from the sewer system during storm events. These findings have also been confirmed by analyses of biological constituents in the sediment samples collected from the receiving waters. A comparative analysis of various pollution sources indicated that pollution problems in the receiving waters were caused not only by the municipal effluents from the Town of Malacky, but also by diffuse agricultural pollution and release of heavy metals, especially Zn, from the native soils in the surrounding area.

Watershed-scale response to agricultural diffuse pollution control programs in Vermont, USA

From 1979 to 1990, the LaPlatte River Watershed and the St. Albans Bay Watershed Rural Clean Water Program projects in Vermont (USA) sought to reduce sediment, nutrient, and bacteria loads to parts of Lake Champlain impaired by eutrophication. Best Management Practices (BMPs) to control diffuse sources of pollution from dairy agriculture were widely implemented through a voluntary program of technical assistance and cost-sharing by agencies of the U.S. Department of Agriculture. Intensive water quality monitoring was undertaken to document water quality changes resulting from the land treatment programs, including studies of BMP effectiveness and long-term watershed-scale trend monitoring. Some BMPs significantly reduced edge-of-field pollutant delivery to surface waters. Phosphorus export from corn fields was up to 1500% higher where manure was winter spread and up to 15% of the phosphorus applied in winter-spread manure was lost in runoff. A vegetated filter strip retained more than 90% of sediment and nutrients in milking center waste and functioned effectively year-round. Watershed-level response, however, was not simply the sum of edge-of-field changes. Sediment concentration and export decreased in both project areas, but anticipated decreases in nutrient concentrations and loads did not occur. The most significant water quality trends observed were 50–75% reductions in indicator bacteria counts in all study watersheds. Factors contributing to the lack of general response in nutrient levels, recommendations for future agricultural pollution control projects, and implications for planning of diffuse source pollution control programs are discussed.

The Role of Small Wetlands in Catchment Management: Their Effect on Diffuse Agricultural Pollutants

AbstractDespite extensive interest in natural wetlands and their use in waste‐water technology, little is known about how effective they are for the control of diffuse agricultural pollution. The impact of a small upland wetland located along a drainage line on different storm generated discharge events and resultant downstream nutrient loads over a two year period was assessed. Results for individual events indicated that the relationship between this wetland and its catchment was variable. An annual nutrient budget was determined for this wetland for the period March 1994 to February 1995. The wetland retained 9.7 kg yr−1 (20.5 kg yr−1) of nitrogen and 1.5 kg yrl (±0.1 kg yr−1) of phosphorus which represented 23% of the nitrogen and 38% of the phosphorus that flowed from this catchment. It is concluded that this form of wetland has a role in strategic catchment management for the interception of nutrients flowing from diffuse agricultural sources.

Watershed-scale response to agricultural diffuse pollution control programs in Vermont, USA

From 1979 to 1990, the LaPlatte River Watershed and the St. Albans Bay Watershed Rural Clean Water Program projects in Vermont (USA) sought to reduce sediment, nutrient, and bacteria loads to parts of Lake Champlain impaired by eutrophication. Best Management Practices (BMPs) to control diffuse sources of pollution from dairy agriculture were widely implemented through a voluntary program of technical assistance and cost-sharing by agencies of the U.S. Department of Agriculture. Intensive water quality monitoring was undertaken to document water quality changes resulting from the land treatment programs, including studies of BMP effectiveness and long-term watershed-scale trend monitoring. Some BMPs significantly reduced edge-of-field pollutant delivery to surface waters. Phosphorus export from corn fields was up to 1500% higher where manure was winter spread and up to 15% of the phosphorus applied in winter-spread manure was lost in runoff. A vegetated filter strip retained more than 90% of sediment and nutrients in milking center waste and functioned effectively year-round. Watershed-level response, however, was not simply the sum of edge-of-field changes. Sediment concentration and export decreased m both project areas, but anticipated decreases in nutrient concentrations and loads did not occur. The most significant water quality trends observed were 50–75% reductions in indicator bacteria counts in all study watersheds. Factors contributing to the lack of general response in nutrient levels, recommendations for future agricultural pollution control projects, and implications for planning of diffuse source pollution control programs are discussed.

Diffuse Pollution in the Lagoon of Venice

The hypertrophic conditions of several confined areas in the Lagoon of Venice are but one of the consequences of nutrient discharges from its drainage basin. The monthly distribution of these loads, as well as their spacial subdivision among different tributaries of this characteristic water body, directly affect the growth cycle of macroalgae in it. The magnitude of these loads cannot be precisely measured by direct methods, however, it can be estimated by simulation with appropriate models. A comprehensive study aimed at the determination of these loads is under way as part of a larger intervention program to restore the physical and ecological equilibrium of the Lagoon. This paper focuses on the results of the simulation of diffuse loads generated in the Lagoon watershed. These results were obtained by interfacing a geographical information system (GIS) of the watershed and two models simulating respectively urban and agricultural diffuse pollution. Diffuse loads are then compared with the corresponding point sources to evaluate their relative contributing role in the dystrophic behavior of the Lagoon. The relative importance of diffuse sources is discussed with particular reference to time and space variability of the loads.