【摘要】 本文阐明了长江下游水体中的主要溶解组分,主要是由蒸发岩和碳酸盐经化学风化作用所提供的。其中,SO₄部分由化石燃料燃烧后生成的SO₂在大气中氧化成SO₃,并随降雨生成H₂SO₄而进入河水,同时还分析了长江在入海过程中,各溶解组分的浓度受物理混合的影响以及可能发生的转移和溶出作用。更多还原

【Abstract】 The Changjiang River is the largest in China and the third largest in the world in terms of discharge. In recent years, a number of scientists have studied on the transfer and flux of its dissolved matter. These studies are very important in illustrating the oceanographic features of the East China Sea. Cruise to collect water samples and surface sediments from Nanjing, lower reaches of the Changjiang River, to the estuary as shown in Fig. 1 was conducted by vessel "Venus Ⅱ" in October 1983. Pore waters of sediments were obtained by using a Model CP-1 contamination-proof hydraulic piston squeezer designed and made by ourselves. Concentrations of major dissolved constituents Na, K, Ca, Mg, Cl, SO₄ and SiO₂ in river, sea and pore waters were analyzed. Eh and pH of the waters and sediments were determined in situ. The results obtained are summarized as follows: 1. The nonanthropogenie SO₄ in the Changjiang River is attributed to weathering of sulphide and sulphate minerals, and anthropogenic sulfur which is additional source of SO₄ in this river is attributed to acid rain containing H₂SO₄ formed by atmospherical SO₂ derived from the burning of fossil fuels in the region of the lower reaches. Caand Mg in rivers are derived from weathering of carbonate minerals, Mg mainly from weathering of silicate minerals. However, Fig. 3b shows that Ca and Mg in the Changjiang River are derived probably less from weathering of silicate minerals. 2. The Changjiang River Estuary is of a characteristic two-layer flow with entrainment of sand in accordance with the salinity section of the estuary as shown in Fig. 4. Whence, a model of two-layer exchange of water between the Changjiang River Estuary and the sea can be advanced as shown in Fig. 5. In which R, Q₁ and Q₂ represent the discharges of river, outflowing upper layer water and inflowing lower layer water, respectively; C_R, C₁ and C₂ represent the concentrations of a certain constituent in river, upper and lower layer waters, respectively. Assuming a steady state and no change in water volume of the estuary, the balance between the inflowing and the outflowing as in Fig. 5 should be established: Q₁=Q₂+R （1） and in case of no addition or removal and on the basis of mass balance there should be the following relation: Q₁C₁=Q₂C₂+RC_R （2） Similarly, for a conservative constituent: Q₁C₁⁰ =Q₂C₂⁰+RC_R⁰ （3） where C° represents the concentration of the conservative constituent Cl, the subscripts are the same as that mentioned above. In general condition such as the Changjiang River Estuary, viz, C₂⁰C_R⁰, and from the formula 1, 2 and 3 the following expressions can be derived: Q₁=RC₂⁰/（C₂⁰-C₁⁰） （4） Q₁=RC₁⁰/（C₂⁰-C₁⁰） （5） C_{1C1⁰（C2-CR）/C2⁰}+C_R （6） 3. In the condition of two-layer exchange of water in estuary, C₂⁰, C₂ and C_R can be considered as constants. Thus, the relation of dissolved constituent concentration C₁ to conservative constituent concentration C₁⁰ is a straight line in compliance with the formula 6. Nevertheless, by comparison of the results calculated from formula 6 with those of measurement, in addition to SO₄ and K in stations of H₁₄ and H₁₅, which were likely to occur in processes of addition and removal, respectively, the other constituents were mainly controlled by physical mixing in the estuary （Fig. 6a—f）. 4. The Q₁C₁ values for the dissolved constituents in the upper layer waters of the stations in the area of the estuary are calculated and listed in Tab. 1.更多还原