Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Problems of Water Pollution Related to Agricultural Production IMRICH DAUBNER Institute of Experimental Biology and Ecology (SAV) Large-scale agricultural production accompanied by intensive chemical use is one of the major causes of surface and groundwater contamination. Until recently communal and industrial waste water represented the highest pollution load. At present, agriculture is in the lead in polluting surface and groundwater, and this trend has be- come a serious problem. Certainly, the concentration of agricultural production into larger units has reduced the number of pollution sources, but the intensity of pollution has risen considerably. The pollution produced by all agricultural resources in Czechoslovakia is equivalent to almost triple the load from population wastes. In a broader sense, agriculture produces up to 25 types of various pollutants which may be divided, in principle, into five main groups: ⢠wastes from large, domestic animal-breeding centers; ⢠wastes from siloing; ⢠industrial fertilizers; ⢠chemical plant protection agents; ⢠pollutants associated with agricultural equipment. In the first group of pollutants not only are liquid and solid excretions involved, but the pollution produced in maintaining agri- cultural facilities is also included. A farm with a stock of 400-800 cattle collects up to 400 m3 of excrement daily. While polluting sur- face and groundwater in general, these substances are particularly dangerous from the public health standpoint. They contain high numbers of microorganisms, including many pathogenic and poten- tially pathogenic agents. Their spectrum is relatively wide. They are 76
77 the causative agents of typhus and other salmonelloses, tuberculosis, anthrax, brucellosis, tularemia, leptospirosis, helminths, and other parasitic diseases. Wastes and extracts from composts and siloing are inseparably linked to the establishment of large breeding centers. In Czechoslo- vakia some 25-30 million tons of fodder are siloed yearly. From this amount 10-15 percent leak out into the soil and ground water. The substances contained in these so-called "silo juices" represent a diversified compound of organic matter, particularly proteins. Cal- culations have shown that these extracts are more than 200 times more concentrated than sewage from the population. At the same time they are a good nutrient substrate for the reproduction of the most diversified heterotrophic bacteria in water. Especially important from the aspect of either surface or ground- water pollution is the intensive chemical use in agriculture, especially in plant production. More than six million hectares of agricultural land are chemically treated in Czechoslovakia, with a consumption of 60-80 thousand tons of various chemicals. These include both combined industrial fertilizers and substances used for plant protec- tion. In the last 30 years, the volume of nitrogen fertilizers rose in Czechoslovakia more than tenfold. Converted to pure nutrients, the volume of phosphorous and kalium fertilizers grew approximately sevenfold. On average, this currently represents some 270 kg per hectare. Science and experience have borne out that the use of such quantities of chemicals is irrational since plants are capable of uti- lizing only a limited part of the nutrients present. The rest enters the surface and groundwater amounting to several thousand tons of chemical substances annually in the republic of Slovakia alone. Detailed analyses of the causes and the character of water pollution have shown that it is the nutrients from the fertilized soil which account for almost 50 percent of the load in the receiving waters. Nitrogen fertilizers have high solubility in water and do not easily become immobilized in soil. The introduction of large amounts of phosphorus and nitrogen into water results in intensive development of algae and the associ- ated phenomenon of eutrophication, which makes the water useless for many purposes. The costs of treatment rise quickly due to clogged filters and costs in removing odors, tastes, and discoloration. Cases have shown that both domestic and wild animals can die after swal- lowing polluted water. The mucuous membranes and skin can be
78 damaged, and dysenteric and gastroenteric symptoms have appeared in humans as well. Worldwide problems have resulted from agents used in agri- culture for plant protection, with pesticides ranking at the top of the list. These include preparations involving chlorinated hydrocar- bons, organophosphates, bromine, and iodine compounds. Apart from their positive effect on crop production, they exhibit negative properties that are magnified by their incorrect use. The worldwide production of pesticides, represented by approximately 100,000 com- mercial products, is estimated at 1,500,000 tons yearly. In Czechoslo- vakia up to 600 preparations are registered, and 182 belong to the group of particularly dangerous poisons. Annual production amounts to about 25,000 tons, representing roughly 3.6 kg per hectare. From 10 to 40 percent of the pesticides used enter surface and groundwater. These substances may persist in water for long periods, concentrate in sediments or sludge, and accumulate in insects, vege- tation, and fish. In estimating the public health hazard of pesticides, it should be noted that under the effect of various ecological factors the original substance may change its original biological properties. The successful elimination of pesticides from the environment is relatively slow. In water these substances undergo hydrolytic trans- formations, and these products of hydrolysis are also of concern with regard to public health. Our experiments show that several species of microorganisms effectively destroy pesticides in water, es- pecially those of the genus Pseudomonaa that utilize pesticides as a source of carbon, nitrogen, and energy. Microorganisms are capable of degrading not only chlorinated hydrocarbons but other types of pesticides as well. Microbial oxidation often occurs. This so-called "co-metabolism" is a significant factor in the removal of noxious bio- cides from the environment, even if full mineralization to inorganic components is not achieved. As is also known, the concentrations of pesticides usually present in our surface and ground water do not act detrimentally upon the microfiora and may be systematically destroyed. Higher doses, however, do affect physiological properties and kill cells. The combination of several substances may have a potentiating effect. These results constitute an additional scientific argument against increasing the quantity of pesticides in the envi- ronment. The application of chemical agents must be regulated in order to achieve the goal of plant protection and elimination of pests with- out detrimental side effects on man's health and his environment,
70 including food quality. Support should be given to facilitating the transition from contemporary plant protection based on chemical prevention and pest liquidation principles to integrated plant protec- tion involving more natural methods. Such a procedure, which has been successfully developed at the Center for Biological and Ecolog- ical Sciences of the Slovak Academy of Sciences, could save millions in local and foreign currency. Similarly, the pollution produced in connection with up-to-date agricultural equipment is not negligible. This includes the crude oil products of petroleum, fuel oil, and lubricants that enter the soil and then groundwater through careless handling. The amounts involved are quite large. Crude oil hydrocarbons represent a particularly disagreeable type of water pollution; whereas the majority of other wastes form a homogenous system with water, crude oil hydrocarbons produce a heterogeneous environment. Most often they are embodied in emulsions. In larger amounts, the particles subsequently form oil spots or an oil film on the surface of the water, which is often deposited on the shore and covers the macrovegetation. From the aspect of groundwater pollution the most dangerous pollutants are crude oil hydrocarbons because of their ability to move easily from the source of pollution. Their infiltration into soil is ten times faster than into water. Microorganisms contribute to their elimination in both surface and groundwater. Bacteria from the genera Achromobacter, Bacillus, Flavobacterium, Micrococcus, Mycobacterium, and especially Pseudomonas are capable of oxidiz- ing or degrading both aliphatic and aromatic hydrocarbons. Under favorable ecological conditions, they can degrade in nature at a rate of approximately 7 mg per cm2 of water surface per day. We are aware that to satisfy the needs of the population, agri- culture should take precedence over many other branches of the economy. What cannot be forgotten, however, is the negative side of this important activity. Measures must be taken to prevent, at all costs, the degradation of the environment, and particularly of such a precious natural resource as water which is becoming a limiting factor in many areas of human activity. Contemporary engineering expertise allows us to take such measures. They only need to be thoroughly and systematically brought to fruition.
