[Quantification of Nitrate and Nitrite in Soil Sample of North Wales]

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Table of Contents

Nitrogen cycle5

Source of Nitrate and Nitrite in Soil6

Soil Type7

Factor affecting the concentration of Nitrate and nitrite in soil9

Standard of Nitrate and nitrite in soil11

Health effect of nitrate and nitrite15

Equipment19

Reagents19

Procedure19

Calculation20

Precision and Accuracy20

Interferences20

Effects of Storage20

Safety and disposal20

Comments21

Summary21

REFERENCES24

List of figures

FIGURE 1. A SIMPLIFIED MODEL OF THE N CYCLE AS AN INTERNAL CYCLE INTERACTING WITH THE SURROUNDINGS BY SEVERAL PROCESSES (EXTERNAL CYCLE). THE CHEMICAL FORMS OF IMPORTANT INPUTS AND OUTPUTS ARE INDICATED8

FIGURE 2 SEASONALITY OF NITRATE CONCENTRATIONS IN STREAM WATER OUTPUT IN FORESTED CATCHMENTS WITH MAINLY NORWAY SPRUCE (PICEA ABIES) AT DIFFERENT LEVELS OF N LEACHING (HAUHS ET AI., 1989; REPRODUCED BY PERMISSION OF MICHAEL HAUHS)18

List of tables

TABLE 1. EXTERNAL AND INTERNAL FLUXES AND SOIL POOL OF NAND S IN A DENSE NORWAY SPRUCE FOREST PLANTATION IN STROEDAM, DENMARK14

TABLE 2 NITROGEN CYCLE DISRUPTIONS AS INDICATED BY VARIOUS AUTHORS AND THE OBSERVED NITRATE LEACHING OR ACCUMULATION IN THE SOIL WATER (SEE TEXT). THE STUDIES SHOWN ARE PREFERABLY FROM SPRUCE FORESTS19

TABLE .3 POSSIBLE FACTORS INFLUENCING THE RISK OF N SATURATION AND NITRATE LEACHING AFTER DISTURBANCE20

Chapter 1: Literature Review

Nitrogen cycle

Nitrogen is an essential nutrient required by plants in substantial quantities. The nitrogen cycle is perhaps the most complicated among the plant nutrient cycles (Figure 1). Nitrogen exists in the form of inorganic ions, in more or less complex organic compounds as well as in gaseous forms. Considering this diversity of nitrogen compounds existing in the ecosystem, it is not surprising that a great diversity exists both within and between the nitrogen cycles of natural ecosystems. This diversity and complexity complicate the study of nitrogen cycling on ecosystem level (plots, forest stands) and even more in complex terrains such as catchments.

Figure 1. A simplified model of the N cycle as an internal cycle interacting with the surroundings by several processes (external cycle). The chemical forms of important inputs and outputs are indicated



Nitrogen is considered to be the growth-limiting factor in most terrestrial ecosystems, and natural ecosystems are characterized by a tight internal cycling of N. Leaching losses and gaseous losses are generally less than a few kg N ha-l years'. High leaching losses may, however, occur after a disturbance of the system.

In order to increase the yield of agricultural crops, addition of N fertilizer to agricultural ecosystems has increased dramatically during the last 50 years. This agricultural practice has markedly modified the N cycle. The high inputs are followed by large outputs by leaching, gaseous losses and crop removal. Due to this significant quantitative difference in N cycling in natural and agricultural ecosystems, this review of literature is divided into two sections dealing with (I) changes in the biogeochemical cycling of N in forested catchments as examples of natural or semi-natural ecosystems, and (ii) N cycling in agricultural or mixed catchments (agro geochemical N cycling).

Because of the high leaching losses of N from agricultural ecosystems to groundwater and surface water, N is now recognized as an important pollutant.

Nitrogen leaching, namely as nitrate from agricultural lands, affects ...