A study on the physico-chemical speciation of heavy metals in waters of rivers, and lakes in the Changjiang River Valley, China
In the aquatic system, heavy metals always exist in a number of physico-chemical forms: particulate (Cp), soluble which consists of labile (MALI) and bound (inorganic MAb and organic MLb). The environmental behaviors of a metal are critically dependent on these forms. In this paper, the forms of heavy metals in waters from the Changjiang River source to mainstream and lakes were determined by ASV method. The main results are as follows: 1. The total contents (Ct) of Zn, Pb, Cu and Cd in the source were 4.0, 1.88, 1.28 and 0.07 (μg/L) respectively, while Ct (μg/L) in the mainstem were in the order of Zn (20.1) > Cu (14.9) > Pb (6.73) > Cd (0.15). Ct (μg/L) in Dianchi Lake were Zn (7.2) > Pb (0.72) > Cu (0.53) > Cd (0.05), and in Poyang Lake were Zn (12.5) > Pb (4.2) > Cu (3.4) > Cd (0.05), and in Poyang Lake were Zn (12.5) > Pb (4.2) > Cu (3.4) > Cd (0.05). However, most of them were presented as Cp. Their dissolved contents (Cs, μ/L) were lower. 2. The distribution of soluble forms was related to the type of metal and to environmental variables. In general, Zn and Cd have a tendency to be present in MALi, Pb in MAb and Cu in MLb.
Seasonal Variation and Preliminary Risk Assessment of Trace Element Pollution in Surface Water from Langat River, Malaysia
Heavy metals are widely used in various industries and became a great concern all over the world due to environmental contamination. This study provides an assessment of seasonal variability and risks to human health associated with the exposure to heavy metals concentrated in Langat river water of Malaysia. The Department of Environment (DOE) Malaysia kindly provided the heavy metal concentration data in water for this study. Several multivariate estimation such as an independent t test, box-and-whisker plot and Principal component analysis were carried out to evaluate the seasonal variation of metals concentration in water. The average value of ten analyzed metals was 250.81 µg/l and followed in order of abundance by August > Jun > February > October > April > December > March > May > September > January > July > November. The calculated HPI was 123.42, which is far above the critical index value of 100, indicating pollution with respect to heavy metals. Estimates of health risks associated with river water were summarized according to non-carcinogenic and carcinogenic health effects. No potential threat was detected for noncarcinogenic risk as the HI values calculated were <1. Potential carcinogenic risks associated with the ingestion and dermal absorption of heavy metals in water were evaluated probabilistically by performing 10,000 trails for Monte Carlo simulation where potential carcinogenic risk exists in case of Cd and As.It is necessary to take proper steps to reduce the pollution of heavy metals in Langat River.
Quality of rivers of the United States, 1975 water year; based on the National Stream Quality Accounting Network (NASQAN)
The National Stream Quality Accounting Network (NASQAN) was established by the U.S. Geological Survey to provide a nationally uniform basis for continuously assessing the quality of United States rivers. Stations are generally at the downstream end of hydrologic accounting units in order to measure the quantity and quality of water flowing from the units. The 1976 water year is the second year of operation of the network that represents essentially all of the accounting units and thereby describes the water-quality of the entire country. Data are available on a large number of water-quality constituents measured at 345 stations during the 1976 water year. Temperature data (usually continuous or daily measurements) from NASQAN stations were fitted to a first order harmonic equation, and the parameters for the harmonic function are reported for each station. Mean temperatures generally range from 5°-10°C in the North to more than 20°C along the southern border of the continental United States, in Hawaii, and in Puerto Rico; mean temperatures were less than 10°C at 62 stations and greater than 24°C at only 7 stations. Amplitudes of the temperature curves are greatest (greater than 12°C) for the streams at midlatitudes and in the Great and Central Plains, and are smallest for the subtropical and cold-climate streams. Considering chemical and biological characteristics of United States streams as described by NASQAN data, water quality is best (by many standards) in the Northeast, Southeast, and Northwest. These waters are generally low in dissolved solids and minor chemical constituents, are generally soft (except in Florida), and carry relatively small amounts of suspended sediment. These conditions mainly reflect the geology of the areas and the relatively large amounts of precipitation. However, many of these waters show the effects of pollution and carry moderate or high concentrations of nutrients and have correspondingly high populations of attached and floating plants. High counts of indicator bacteria also show signs of local pollution, particularly in areas of the country with large human or animal populations or both. Streams in the mid-continent area generally contain higher concentrations of minor elements than other areas of the country. Most streams in the Midcontinent and Southwest areas reflect the arid or semiarid climate, erodible soils, and agricultural activities. They are characterized by moderate to high levels of dissolved major and minor constituents, suspended sediment, major nutrients, and biota (floating and attached aquatic plants and indicator bacteria). In addition, pesticide residues were found most often and concentrations were highest in stream water and bottom sediments found in these areas.