| Estuary wetland, as a typical area of land of the land and sea interaction, is facing the threat of severe water shortage. The Liaohe estuary wetland is the second largest wetland in Asia, also is the final barrier of the Liaohe. In recent years, there have been many problems in Liaohe Estuary Wetland, such as insufficient natural rainfall, poor water supply condition, and low organic matter content in the wetland soil. Most of the paper mills are distributed along the river, and discharge much wastewater, so the papermaking wastewater has become one of the inevitable irrigation water sources for the wetland. But there are a variety of heavy metal pollutants in papermaking wastewater, long-term wastewater irrigation will whether or not cause the accumulation of heavy metals in plants, accumulate in the soil is unclear. And more researches for wetland plant absorption of heavy metal effect, characteristics of absorption and accumulation of few studies, In the study, Liaohe Wetland is simulated through the construction of the small experimental unit. The papermaking wastewater from the paper mills in the Wetland are selected to irrigate the reeds in every growth period at the beginning of the reeds so as to explore the dynamic distribution characteristics and the accumulation law of heavy metals in the reed plants and soil under the irrigation condition with different concentrations of papermaking wastewater, and investigate the transfer of heavy metals in the reed-soil system. The research provides theoretical basis and technical support for the analysis and explanation of the absorption and accumulation law of Liaohe Estuary Wetland soil and reed to heavy metals in papermaking wastewater. On the basis of the existing experimental results and research literature, the concentration of papermaking wastewater irrigation is determined, namely,50 mg·L-1,175 mg·L-1 and 300 mg·L-1 respectively. The main research results are as follows:1. Distribution and accumulation law of heavy metals in reed plants. After the papermaking wastewater irrigation, reed plant parts of each heavy metal accumulation increases along with the change of reed growth period, increase with the increase of wastewater concentration, and reeds were higher than control group in heavy metal content in plant. Among them, in the germination period of the reed, CODCr concentration wastewater of 50 mg·L-1, nickel, copper, lead, minimize accumulation in the stem of the reed, were 0.121 mg·kg-1,0.513 mg·kg-1,1.729 mg·kg-1, arsenic, minimum accumulation of manganese in reed leaves,0.146 mg·kg-1,7.383 mg·kg-1. Minimum accumulation of cadmium in the root of the reed is 0.077 mg·kg-1, when the CODCr concentration of 300 mg·kg-1, nickel, manganese, arsenic, cadmium accumulation in reed leaves, minimum 0.317 mg·kg-1,17.454 mg·kg-1,0.311 mg·kg-1,0.236 mg·kg-1, copper, lead, minimum accumulation in the reed stems,8.538 mg·kg-1, 2.364 mg·kg-1, to reed, mature period, wastewater CODCr concentration of 50 mg·L-1, accumulation of nickel in the stem of the reed is the largest,1.265 mg·kg-1, copper, arsenic, cadmium, lead, manganese, in the amount of accumulation in the root of the reed is the largest, 29.396 mg·kg-1,5.938 mg·kg-1,54.974 mg·kg-1,14.058 mg·kg-1,0.656 mg·kg-1; Accumulation of nickel in the stem of the reed maximum 4.241 mg·kg-1, copper, arsenic, cadmium, lead, manganese, accumulation of the reed root is the largest,64.749 mg·kg-1,16.524 mg·kg-1, 129.521 mg·kg-1,89.624 mg·kg-1,2.619 mg·kg-1. Show that under the condition of natural emissions, increasing the concentration of wastewater can increase the reeds on the absorption of heavy metal accumulation amount, can make full use of reeds and other plants absorb purification manganese, lead and other heavy metals in wastewater.Based on logisitics model fitting concentration of heavy metal elements in soil dynamics model, the accomodation results showed that the concentration of heavy metals in the soil and environment are related, and michaelis constant of each heavy metal in soil environment accomodation with increases with increasing of the concentration of wastewater treatment in pulp and papermaking industry, including arsenic, manganese, lead, cadmium concentration in the experimental process under the condition of fitting effect is good, concentration of nickel in CODCr concentration of 175 mg·L-1 and 300 mg·L-1, better fitting effect under the condition, copper concentration under the condition of water irrigation and CODCr concentration of 50 mg·L-1 when the fitting effect is good.2. The distribution characteristics of heavy metals in soil, and the cumulative rule. After the papermaking wastewater irrigation, the soil heavy metal content in increases with the increase of wastewater concentration. The accumulation of heavy metals in the soil volume reached maximum. Including CODCr concentration of 50 mg·L-1 in papermaking wastewater irrigation condition, nickel, cadmium is mainly accumulated in the soil of 0-5 cm, content were 7.143 mg·kg-1,0.809 mg·kg-1; Cu, Mn, As, lead, mainly accumulated in the soil of 20-40 cm, content were 29.239 mg·kg-1,183.335 mg·kg-1,36.671 mg·kg-1,10.492 mg·kg-1; CODCr concentration of 300 mg·L-1 in papermaking wastewater irrigation condition, nickel, cadmium is mainly accumulated in the soil of 0-5 cm, content were 27.741 mg·kg-1,2.487 mg·kg-1; Copper, arsenic mainly accumulated in the soil of 20-40 cm, content were 88.855 mg·kg-1, 22.109 mg·kg-1; Manganese is mainly accumulated in the 5-10 cm of the soil, the content of 542.034 mg·kg-1, lead is mainly accumulated in the soil of 40-60 cm, content is 114.891 mg·kg-1. Showed that the soil to nickel, cadmium, copper, arsenic adsorption ability is strong, weak adsorption capability for manganese and lead.Based on logistic model fitting concentration of heavy metal elements in soil dynamics model and the accomodation results showed that the concentration of heavy metals in the soil and environment are related, and michaelis constant of each heavy metal in soil environment accomodation with increases with increasing of the concentration of wastewater treatment in pulp and papermaking industry, including arsenic, manganese, lead, cadmium concentration in the experimental process under the condition of fitting effect is good, concentration of nickel in CODCr concentration of 175 mg·L-1 and 300 mg·L-1, better fitting effect under the condition, copper concentration under the condition of water irrigation and CODCr concentration of 50 mg·L-1, when the fitting effect is good.The correlation between enzyme activity and heavy metal. Degree of correlation between soil enzyme activity is close, three kinds of soil urease, phosphatase, dehydrogenase were very significant positive correlation between enzyme activity and the correlation coefficient is 0.594,0.663,0.846, respectively (P<0.01), the three enzymes activity is not significantly correlated with the change of the heavy metal content, including urease and the maximum correlation coefficient of the lead and nickel, are 0.852 and 0.804 respectively, lead and nickel content can be used to indicate the change of the urease activity do; Phosphatase and the maximum correlation coefficient of the lead and nickel, are respectively 0.584 and 0.521, lead and nickel content changes can also be used for phosphatase activity changes to indicate; Dehydrogenase and the correlation coefficient of lead and manganese, the largest is 0.596 and 0.519 respectively, the content of lead and manganese available dehydrogenase activity of changes to indicate.3. Under the condition of different concentration wastewater in reed-soil system of distribution of heavy metals. Under the condition of different CODCr concentration papermaking wastewater irrigation, reed absorption rate for large heavy metal copper and cadmium, respectively accounted for 21.391% of the total input of copper, cadmium,17.34%; 14.049%,15.034%; 13.050%,14.3%. In papermaking effluent CODCr concentration of 50 mg·L-1 irrigation condition, the cumulative rates of soil for large heavy metal nickel and lead, respectively,97.797%,94.399% of the total input. In papermaking effluent CODCr concentrations for 175,300 mg·L-1 irrigation conditions, the cumulative rates of soil for large heavy metal nickel and manganese, accounted for 98.456% of the total input,93.741%; 98.524%,94.932%.Reed wetland heavy metal accumulation in different concentration wastewater irrigation conditions, and reed wetland under the conditions of different concentration papermaking wastewater in heavy metal accumulation trends:in the papermaking effluent CODCr concentration of 50 mg·L-1 irrigation conditions, the accumulation of heavy metal nickel, copper and lead, the arsenic, manganese and cadmium accumulation does not appear. In papermaking effluent CODcr concentration of 175 mg·L-1, irrigation conditions in accumulation of heavy metals in soil, but smaller values, and standards of cadmium concentration does not exceed 1. In papermaking effluent CODCr concentration of 300 mg·L-1 irrigation conditions, the accumulation of heavy metals in soil are, among them the content of cadmium in 10 a 0.23 mg·kg-1, after more than standard 1 (0.2 mg·kg-1), but not after a more than 50 standard 2 (0.35 mg·kg-1); Lead accumulation of faster, after a 31.89 mg·kg-1, close to the standard 1 (35 mg·kg-1). |
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