The effects of chemical speciation on mineralization of organic compounds was studied using citric acid as a model substance. The degradation of ¹⁴C-labeled Al-, Co-, Cu-, and Zn-citrate was followed in chemically well-defined media inoculated with mixed cultures of microorganisms (soil extracts from two soils). The degradation of citrate was completely inhibited when the acid was bound to Zn, Cu, or Co and partly inhibited when bound to Al. The mineralization of citrate as well as histidine was also followed by incubation of the complexes (Cu, Zn, Al) in the two soils. No effect of metals on the degradation of histidine was seen. The degradation of citrate in soils was also unaffected when complexed to Cu and Zn, whereas Al exerted an inhibited decomposition in both soils.

A study was carried out recently to determine the pollution level of waters in the Karachi harbour and adjoining backwaters. Nine locations were selected, four in the backwaters, two on the seaside, and three in the main navigable channel. Four of these locations were deliberately selected to coincide with those of a previous study conducted in 1982 by Pakistan Council of Scientific and Industrial Research (PCSIR) so that the values for the concentration of different pollutants could be compared. Analysis was conducted for pH, bicarbonates, Total Solids, Volatile matter in Total Solids, Chlorides, Sulphates, Calcium, Magnesium, Sodium and Potassium.The results indicate that the composition of sea water as far as the concentration of above constituents is concerned has not changed much since the time of the PCSIR study, viz 1982, except that the organic matter concentration has increased. The reasons for this increase in organic loading and its possible impact are discussed in this paper.

A ten year survey of water quality in 330 Massachusetts streams was conducted to examine the rate and pattern of recovery from acidification. Meta-analysis was used to combine the results of the 330 non-parametric trend tests into an overall test for trend in a variety of water quality variables including pH, acid neutralizing capacity (ANC), and major inorganic ions. Analysis of trends in the raw data indicates both pH and ANC are increasing. After detrending for variations in stream runoff, we estimate the streams are recovering from acidification at a rate of +0.021 pH units/year and +2.4μeq/L/year, for pH and ANC respectively. These trends appear to be related to declines in sulfate (−1.8μeq/L/year), while base cation trends were mixed. Meta-analysis reveals the trends are not always homogeneous between seasons or between sites.While it is commonly assumed that the low ANC systems are most ‘sensitive’ to changes in acid or base inputs, we found the greatest rates of change in ANC were associated with the high ANC systems. The greatest increases in pH were seen in the low ANC streams as expected. The results also suggest streams respond quickly to changes in precipitation inputs and stream monitoring networks may be valuable as an early detection technique for changes in environmental quality.