The N balance has been studied in detail in the basins of small rivers under agricultural management and forest use. The N content of the watershed territory of large forests was found to be practically balanced. In the river basin where the land was intensively farmed for 10 yr, N input increased five times through mineral fertilizers, and one-and-a-half times through organic fertilizers. Consequently, the amount of N returned to the atmosphere as a result of denitrification increased by one-and-a-half times, and that leached into the ground water, increased from 0.8 to 6.5 mg 1('-1) N.

Cement dust in the environment poses a threat to the proper functioning of plants in the vicinity of cement factories, as apparent from a field study conducted at different locations in the environs of Churk Cement Factory in Mirzapur District, U.P. Plant samples were collected at 100, 500, 1000, 1500, 2000, and 4000 m northeast of the factory, at three successive stages of plant growth. The plant samples collected at 4000 m distance were treated as control, as there was no apparent deposition of cement dust on their surface. The samples were analyzed with respect to foliar injury symptoms, chlorophyll concentration and phytomass accumulation. Only plants closest to the factory displayed symptoms of foliar injury. The results reveal that wheat plants at polluted sites contained decreased concentration of chlorophyll in their leaves and had reduced accumulation of phytomass, as compared to control. The grains obtained from affected sites showed quantitative and qualitative deterioration. Physico-chemical properties of the soils at polluted sites also underwent some undesirable changes. These effects had negative correlation with the distance from the factory.

The aim of the process under consideration is the degradation of organic pollutants contained in waste water from olive processing. Degradation takes place by processing the polluted water in a tank which contains soil that has certain chemical and biochemical characteristics. The effect of the treatment is an enrichment of the soil with readily-assimilable nutrient substances to the extent that the soil pollutant mixture becomes soil-compost. Neither sludge nor solid residual products are formed in the process, since they too undergo degradation. The treatment of water and sludge is completed on parcels of land underlain with a water-tight base. The watertight floor prevents filtration of polluting substances in the treated water from percolating into the underlying soil.

A quantitative index of synergism, anatagonism and additivity has been measured experimentally in the fish Mystus vittatus for three pesticides viz. Thiotox (Endosulfan) (T), Dichlorvos (D) and Carbofuran (C). For a combination of two pesticides, the dose of the one pesticide of a pair was fixed at the no-effect level while the dose of the second pesticide was increased until the entire dose response curve was obtained. To evaluate interactions of three pesticides, the previous pair of pesticides was kept fixed at their combined TL(,0) level, and the third pesticide was increased and again a dose-response curve was obtained. From the results obtained, it is shown that a particular combination could be synergistic, antagonistic or additive, depending on the relative doses employed. In the present study (T + D)/C combination was most synergistic (toxic) in nature while D/T and C/T were least toxic antagonistic in their effects. However, T/D, (C + T)/D, C/D and D/C combinations were additive in nature. (D + T)/C, (D + C)/T, (T + C)/D and (C + D)/T combinations were found less synergistic in nature than (T + D)/C.

A simple marine algal bioassay method is described for short- and long-term studies on pesticides and industrial wastes. It can be used for rapid screening of a variety of substance with single-species and multiple-species tests and gives relative toxicities of the pollutants tested. Algae are grown in optically matched culture tubes that fit directly into spectrophotometer, allowing population density to be estimated by absorbance without removal of samples. 96h EC50 values for some pesticides and the diatom Skeletonema costatum are: EPN, 340 micro-g/l; carbophenothin, 109 micro-Gg/l; DEF,366 micro-g/l; ethoprop, 8.4 micro-g/l; methylparathion, 4.3 micro-g/l, and phorate, 1.3 micro-g/l. Presence of the chelator EDTA in medium had no effect on toxicity of carbaryl to S. costatum, Nitzschia angularum, Chorococcum sp. and Chlorella sp. Liquid industrial wastes either stimulated growth, inhibited growth, or stimulated growth at low concentrations but inhibited it at higher concentrations. In mixed species studies with the herbicide neburon, presence of a resistant species protected the sensitive species. Liquid industrial wastes from a paper products plant caused changes in relative numbers, as compared to controls, when S. costatum and Porphyridium cruentum were grown together.

Abstract. Samples of forty sewage sludges taken in England during 1979 were analysed for ten heavy metals using a rapid flameless atomic absorption spectroscopic technique. For all metals the mean concentrations were influenced by a small number of sludges containing exceptionally high concentrations. Typically, the concentration ranges showed approximately a 100-fold spread. Calculations based on U.K. guidelines for limiting the addition of toxic metals in sludge to agricultural soils indicated that application rates would theoretically be limited for more than 75% of the sludges by the concentrations of Zn, Cu and Ni, expressed additively as the Zn equivalent. Calculations of the theoretical maximum quantities of sludges which could be applied to land on an annual basis suggested that a significant proportion of the sludges would be unsuitable for application to agricultural land at rates of more than 2 t ha('-1) yr('-1).

Laboratory experiments were conducted to determine the effects of Kepone on the larval development of the mud-crab, Rhithropanopeus harrisii, and the commercial blue-crab, Callinectes sapidus, from the time of hatching until the 1st crab stage was reached. Differential survival of R. harrisii from hatching to 1st crab stage occurred in a range of 35 to 125 ppb Kepone, whereas differential survival of C. sapidus over the same period of development occurred in a range of 0.1 to 1.0 ppb. Statistical analysis indicated that, for every 10 ppb Kepone added, duration from hatching to 1st crab stage of R. harrisii was increased by 0.391+/-0.043 days; whereas for each increase of 0.1 ppb, the duration from hatching to 1st crab stage of C. sapidus is prolonged by 0.38+/-0.10 days. The 1st and 2nd zoeal stages of R. harrisii were the most sensitive developmental stages to Kepone, but the 1st zoeal stage of C. sapidus was not sensitive, statistically, to any concentration of Kepone tested. In zoeal stages II, III and IV, there were significant increases in mortality of C. sapidus over the previous stage in all media tested.

In order to ensure adequate performance and warn of potential ground water contamination, land application systems must be monitored. The monitoring system for the Lake George Village Sewage Treatment Plant land application system is described, including suction Isyimeters, observation wells and tracer studies.

The absorption and loss of tritiated water (HTO) vapor at bare soil and grass surfaces were studied in laboratory and field experiments. The exchange involves turbulent mixing in the air and diffusion within the soil. In short exposures it was found that uptake by moist soil was controlled by atmospheric mixing and was described by an exchange velocity of about 1 cm/s('-1). The exchange velocity was a little smaller for air-dried soil and grass surfaces. For exposure times exceeding a few minutes re-evaporation reduced the rate of net uptake, but the total amount deposited continued to increase as the HTO diffused deeper into the surface. The diffusion coefficient for HTO in soil was investigated in the laboratory and a simple equation was derived to predict the effective diffusion coefficient. Tritiated water, absorbed during a brief exposure, evaporated during several weeks. Its behaviour was described by the diffusion equation, but unexplained discrepancies were found in apparent diffusion coefficients in field conditions. Rain washed the activity into the soil and impeded evaporation. Most of the HTO vapor interacts with the surface within two or three days following a low level release. The effect of the surface exchange on the distribution of dose following a release of HTO vapor may be large, but will depend on the weather over a period of weeks and is difficult to foresee